JP7532225B2 - Charged particle beam inspection device and charged particle beam inspection method - Google Patents

Description

The present invention relates to a charged particle beam inspection device and a charged particle beam inspection method. For example, the present invention relates to an inspection device that irradiates a multi-beam electron beam, acquires a secondary electron image of the emitted pattern, and inspects the pattern.

In recent years, as large-scale integrated circuits (LSIs) have become more highly integrated and have larger capacities, the circuit line width required for semiconductor elements has become increasingly narrow. These semiconductor elements are manufactured by forming circuits by exposing and transferring a pattern onto a wafer using a reduced projection exposure device known as a stepper, using an original pattern (also called a mask or reticle, hereafter collectively referred to as a mask) on which a circuit pattern is formed.

And for the manufacturing of LSIs, which require a huge manufacturing cost, improving the yield is essential. However, immersion exposure and multi-patterning technology have already achieved processing dimensions of less than 20 nm, and furthermore, the practical application of EUV (Extreme Ultraviolet) exposure is about to realize fine processing of less than 10 nm. In addition, practical application of fine processing techniques other than those using exposure machines, such as NIL (Nano Imprinting Lithography) and DSA (Directed Self-Assembly, self-organizing lithography), is also progressing. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small, and the number of patterns that must be inspected for the same area has become enormous. Therefore, there is a need for high-precision and high-speed inspection devices that inspect defects in ultra-fine patterns transferred onto semiconductor wafers. Another major factor that reduces yields is pattern defects in the masks used when exposing and transferring ultra-fine patterns onto semiconductor wafers using photolithography technology. For this reason, there is a need for high-precision inspection equipment to check for defects in transfer masks used in LSI manufacturing.

A known inspection method is to compare an optical image of a pattern formed on a sample to be inspected, such as a wafer such as a semiconductor wafer or a mask such as a lithography mask, captured at a predetermined magnification using a magnifying optical system with design data or an optical image of the same pattern on the sample to be inspected. For example, there is a "die to die inspection" method in which optical image data of the same pattern captured at different locations on the same mask are compared, and a "die to database inspection" method in which pattern design CAD data is converted into a device input format for input by a drawing device when drawing a pattern on a mask, drawing data (design pattern data) is input to an inspection device, design image data (reference image) is generated based on this, and this design image data is compared with an optical image that is the measurement data captured by capturing the pattern. In such an inspection method using an inspection device, the substrate to be inspected is placed on a stage (sample stage), and the stage is moved to scan the sample to be inspected with a light beam, and the inspection is performed. A light beam is irradiated onto the substrate to be inspected by a light source and an illumination optical system. The light that is transmitted through or reflected from the substrate to be inspected passes through the optical system and forms an image on a sensor. The image captured by the sensor is sent to a comparison circuit as measurement data. After aligning the images, the comparison circuit compares the measurement data with the reference data according to an appropriate algorithm, and if there is a mismatch, it determines that there is a pattern defect.

In the above-mentioned pattern inspection device, an optical image is obtained by irradiating a substrate to be inspected with a laser beam and capturing a transmitted or reflected image. In contrast to this, the development of an inspection device that irradiates a substrate to be inspected with a multi-beam consisting of multiple electron beams arranged in an array such that multiple beam rows are arranged in a straight line at the same pitch, detects secondary electrons corresponding to each beam emitted from the substrate to be inspected, and obtains a pattern image is also progressing. In a pattern inspection device using an electron beam including such a multi-beam, the substrate to be inspected is scanned for secondary electrons in each small area. In this case, a so-called step-and-repeat operation is performed in which the position of the substrate to be inspected is fixed while the beam is being scanned, and the position of the substrate to be inspected is moved to the next small area after the scan is completed. By using a multi-beam array arrangement in which multiple beam rows are arranged in a straight line at the same pitch, multiple beams can be arranged in a limited area, making it possible to simultaneously scan multiple small areas at once. Therefore, an improvement in throughput is expected. However, in the step-and-repeat operation, a settling time (overhead time) is required for the stage position to stabilize each time the stage is moved. Because the range (small area) scanned in one go is small, the number of steps of the stage is enormous to scan the entire substrate. This means that time not needed for scanning is wasted, equal to the number of steps multiplied by the settling time. Even when scanning a substrate using multiple beams, some estimates suggest that for one substrate, more than 80 hours of time not needed for scanning may be wasted.

In order to improve the throughput of the inspection device, it is being considered to change the stage movement method from a step-and-repeat operation method to a continuous movement method that does not require a settling time for each step. However, when scanning with an arrayed multi-beam, the continuous movement method can eliminate the need for settling time, but instead, the same small area is sent sequentially within the scanning range of multiple beams lined up in the movement direction, which results in repeated unnecessary scanning of small areas where a pattern image has already been acquired. Therefore, it still does not lead to an improvement in throughput. In order to avoid such repeated unnecessary scanning, it is necessary to skip over the small area that has already been scanned and scan the next small area, so the deflection width of the multi-beams needs to be increased. However, if the deflection width of the beam is increased, the effect of aberration in the electron optical system becomes greater, making it difficult to narrow each beam sufficiently, resulting in so-called blurring.

The following technology has been disclosed to suppress this. That is, a multibeam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on the substrate surface in a first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction is used to collectively deflect the multibeam to a group of N x N' divided small regions on the substrate arranged in N pitch p in the first direction and N' in the second direction, among a plurality of divided small regions obtained by dividing an inspection area of the substrate into a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction. While the stage moves continuously in the direction opposite to the first direction over a distance obtained by N/M·p, the multibeam is tracking deflected to follow the continuous movement of the stage. Then, while the multibeam is tracking deflected to follow the continuous movement of the stage, the multibeam is collectively deflected to scan the group of N x N' divided small regions.

The above technology makes it possible to reduce the amplitude of the beam deflection in the first direction. This makes it possible to reduce the effect of aberrations in the electron optical system.

Here, depending on the type of sample to be inspected, the pattern image may become white or black due to the charging of the sample to be inspected. This may make it difficult to determine whether or not there is a pattern defect. Therefore, it is possible to obtain multiple pattern images by scanning the multi-beam in different directions on, for example, the small area (including the divided small area) on the sample to be inspected, and then perform inspection using an image obtained by averaging the multiple pattern images. Such an averaged image can be easily obtained when the stage does not move continuously. Next, as described above, consider the case where the stage movement method is the continuous movement method. In this case, when performing beam scanning, there is a problem that unintended vibrations are applied to the stage due to the continuous movement of the stage, causing a specific part of the sample to jump out of the area where beam scanning is possible. In addition, this problem is particularly serious when beam scanning is performed at the edge of the small area described above. Furthermore, the unintended vibrations applied to the stage are particularly likely to occur in the direction of stage movement or the opposite direction to the direction of stage movement.

JP 2018-017571 A

In view of this, one aspect of the present invention provides an inspection device and method for performing pattern inspection while continuously moving a stage using a multi-beam in which multiple beams are aligned in the direction of stage movement, in which images acquired by scanning beams in different directions are averaged while eliminating the effects of unintended stage vibration.

A charged particle beam inspection device according to one aspect of the present invention includes a movable stage on which a substrate is placed, a stage control circuit for continuously moving the stage in a direction opposite to a first direction, and a multi-beam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on the substrate surface in the first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction, and performs a test on the substrate by dividing an inspection area of the substrate into a plurality of small areas having a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction, the plurality of small areas being divided into N small areas at a pitch p in the first direction and N' small areas in the second direction. a first function of deflecting the multibeams collectively onto a group of N×N' small regions arranged on a substrate, and tracking-deflecting the multibeams so as to follow the continuous movement of the stage while the stage is continuously moving a distance obtained by N/M·p in the direction opposite to the first direction, and performing tracking reset by re-deflecting the multibeams collectively onto a new group of N×N' small regions arranged at a pitch p in the first direction, which is N away from the group of N×N' small regions, by the time the movement of the stage is completed in the direction opposite to the first direction by the distance obtained by N/M·p; While the beam is being deflected for tracking, a first step is performed in which, in each of the plurality of small regions, a deflection of the multi-beams is repeatedly performed collectively along a second direction from the end portion on the opposite side to the first direction to the end portion on the first direction, with the end portion on the opposite side to the first direction of each of the plurality of small regions as a starting point and the end portion on the first direction of each of the plurality of small regions as an ending point, and then, a first step is performed in which, in each of the plurality of small regions, a deflection of the multi-beams collectively along a second direction is repeatedly performed from the end portion on the opposite side to the first direction to the end portion on the first direction, with the end portion on the opposite side to the first direction of each of the plurality of small regions as a starting point and the end portion on the first direction of each of the plurality of small regions as an ending point. The charged particle beam inspection device is characterized in that it is equipped with a deflector having two functions, a first function of collectively deflecting the multibeams in a direction opposite to the second direction, with the end point at the first direction as an end point, from the end point at the opposite side of the first direction toward the end point at the first direction, thereby scanning a group of N x N' small regions, and a detector for detecting secondary electrons emitted from the substrate as a result of irradiating the substrate with the multibeams, and uses a combination of values such that the greatest common denominator between the values of N and M is 1, as the values of N and M.

In the above-mentioned charged particle beam inspection apparatus, when the measurement pixel size that can be irradiated with the charged particle beam is PS and the beam scan time in the second direction or the reverse direction to the second direction, including the second beam settling time Ofs_v in the second direction or the reverse direction to the second direction, is Tv, it is preferable that the stage movement speed V is V = PS N /(2Tv).

The charged particle beam inspection device according to claim 1, wherein, in the above-mentioned charged particle beam inspection device, when the measurement pixel size that can be irradiated with the charged particle beam is PS and the scanning frequency of the charged particle beam is f, the beam scan time Tv in the second direction or the direction opposite to the second direction is Tv = (p/PS) x (p/M/PS) x (1/f) + (p/M/PS) x Ofs_v.

In the above-mentioned charged particle beam inspection device, it is preferable to further include an average image acquisition circuit that acquires an average secondary electron image by averaging the first secondary electron image acquired in the first step and the second secondary electron image acquired in the second step.

1 is a configuration diagram showing a configuration of a pattern inspection device according to a first embodiment; 3 is a conceptual diagram showing the configuration of a shaping aperture array member in the first embodiment. FIG. 1 is a conceptual diagram for explaining an example of a scan operation in the first embodiment. FIG. 4 is a diagram showing an example of a multi-beam irradiation area and measurement pixels in the first embodiment. FIG. FIG. 13 is a conceptual diagram for explaining an example of details of a scan operation in a comparative example to the first embodiment. FIG. 11 is a conceptual diagram for explaining an example of details of a scan operation in the first embodiment. 5 is a diagram showing an example of the relationship between the number of beams and the number of divisions in the first embodiment. FIG. 4 is a diagram showing the relationship between sub-regions and scanning regions in the first embodiment. FIG. FIG. 11 is a schematic diagram showing an example of a scanning operation in the first mode of the first embodiment. FIG. 11 is a schematic diagram showing an example of a scanning operation in the first mode of the first embodiment. FIG. 13 is a schematic diagram showing an example of a scanning operation in a second aspect of the first embodiment. FIG. 13 is a schematic diagram showing another example of the scanning operation in the second aspect of the first embodiment. FIG. 13 is a schematic diagram showing another example of the scanning operation in the second aspect of the first embodiment. FIG. 13 is a schematic diagram showing another example of the scanning operation in the second aspect of the first embodiment. FIG. 13 is a schematic diagram showing an example of a scan operation in another comparative example of the first embodiment; FIG. 13 is a schematic diagram showing an example of a scan operation in another comparative example of the first embodiment; FIG. 2 is a flowchart showing some of the main steps of the inspection method according to the first embodiment. FIG. 13 is a conceptual diagram for explaining another example of details of the scan operation in the first embodiment. 11 is a conceptual diagram for explaining an example of a relationship between sub-regions and corresponding beams in a scan operation in the first embodiment. FIG. FIG. 11 is a conceptual diagram for explaining another example of the scan operation in the first embodiment. 2 is a diagram showing an internal configuration of a comparison circuit according to the first embodiment; 4 is a diagram showing an example of a relationship between a grid and a frame area in the first embodiment. FIG. FIG. 11 is a configuration diagram showing another configuration of the pattern inspection device in the first embodiment.

In the following embodiments, an example of a charged particle beam will be described using an electron beam. However, this is not limiting. Other charged particle beams, such as an ion beam, may also be used.

Embodiment 1.
FIG. 1 is a configuration diagram showing the configuration of a pattern inspection apparatus in the first embodiment. In FIG. 1, an inspection apparatus 100 for inspecting a pattern formed on a substrate is an example of a charged particle beam inspection apparatus. The inspection apparatus 100 includes an electron optical image acquisition mechanism 150a and a control circuit 160 (control unit). The electron optical image acquisition mechanism 150a includes an electron beam column 102 (electron lens barrel), an inspection chamber 103, a detection circuit 106, a stripe pattern memory 123, and a laser length measurement system 122. In the electron beam column 102, an electron gun (irradiation source) 201, an electromagnetic lens 202, a shaping aperture array substrate 203, a reduction lens 205, an electromagnetic lens 206, an electromagnetic lens (objective lens) 207, a deflector 208, a collective blanking deflector 212, a limiting aperture substrate 213, a beam separator 214, a deflector 218, electromagnetic lenses 224 and 226, and a multi-detector 222 are arranged.

In the inspection chamber 103, an XY stage (an example of a sample stage or stage) 105 that can move at least on the XY plane is placed. On the XY stage 105, a substrate (inspected sample) 101 on which a chip pattern to be inspected is formed is placed. The substrate 101 is, for example, a silicon wafer. The substrate 101 is placed on the XY stage 105 with the pattern-forming surface facing upward. Also, on the XY stage 105, a mirror 216 is placed that reflects laser light for laser length measurement irradiated from a laser length measurement system 122 placed outside the inspection chamber 103. The multi-detector 222 is connected to a detection circuit 106 outside the electron beam column 102. The detection circuit 106 is connected to a stripe pattern memory 123.

In the control system circuit 160, the control computer 110, which is a computer, is connected to the position circuit 107, the development circuit 111, the stage control circuit 114, the lens control circuit 124, the blanking control circuit 126, the deflection control circuit 128, the image storage device 132, the comparison circuit 108, the storage device 109 such as a magnetic disk device, the monitor 117, the memory 118, the printer 119, the reference circuit 112, the settling time storage device 140, the scan frequency storage device 141, the average image acquisition circuit 144, the movement speed calculation circuit 146, the scan time calculation circuit 148, and the scan time storage device 149 via the bus 120. The XY stage 105 is driven by the drive mechanism 142 under the control of the stage control circuit 114. In the drive mechanism 142, for example, a drive system such as a three-axis (X-Y-θ) motor that drives in the X direction, Y direction, and θ direction is configured, and the XY stage 105 is movable. These X, Y, and θ motors (not shown) can be, for example, step motors. The XY stage 105 can be moved horizontally and in a rotational direction by motors on the X, Y, and θ axes. The movement position of the XY stage 105 is measured by a laser measurement system 122 and supplied to the position circuit 107. The laser measurement system 122 measures the position of the XY stage 105 using the principle of laser interference by receiving reflected light from a mirror 216.

The electron gun 201 is connected to a high-voltage power supply circuit (not shown), and an acceleration voltage is applied between the filament and the extraction electrode (not shown) in the electron gun 201 from the high-voltage power supply circuit. In addition, a voltage is applied to a specified extraction electrode, and the cathode (filament) is heated to a specified temperature, so that the electrons emitted from the cathode are accelerated and emitted as an electron beam. The reduction lens 205 and the objective lens 207 are, for example, electromagnetic lenses, and are both controlled by the lens control circuit 124. The beam separator 214 is also controlled by the lens control circuit 124. The collective blanking deflector 212 is composed of at least two-pole electrodes, and is controlled by the blanking control circuit 126. The deflectors 208 are each composed of at least four-pole electrodes, and are controlled by the deflection control circuit 128.

When the substrate 101 is a semiconductor wafer on which multiple chip (die) patterns are formed, pattern data for the chip (die) patterns is input from outside the inspection device 100 and stored in the storage device 109. When the substrate 101 is an exposure photomask, design pattern data that is the basis for forming a mask pattern on the exposure photomask is input from outside the inspection device 100 and stored in the storage device 109.

Here, FIG. 1 shows the configuration necessary for explaining this embodiment. The inspection device 100 may also be provided with other configurations that are normally required.

2 is a conceptual diagram showing the configuration of the shaping aperture array member in the first embodiment. In FIG. 2, the shaping aperture array substrate 203 has holes (openings) 22 in a two-dimensional (matrix-like) array of N columns (x direction) × N' rows (y direction) (N is an integer of 2 or more, N' is an integer of 1 or more) in the x and y directions (x: first direction, y: second direction) at a predetermined arrangement pitch L. Note that when the reduction ratio of the multi-beam is a times (when the multi-beam diameter is reduced to 1/a and irradiated onto the substrate 101), and the inter-beam pitch of the multi-beam in the x and y directions on the substrate 101 is p, the arrangement pitch L is L = (a x p). The example in FIG. 2 shows a case where 5 x 5 holes 22 for forming the multi-beam are formed, where N = 5 and N' = 5. Next, the operation of the electro-optical image acquisition mechanism 150a in the inspection device 100 will be described.

The electron beam 200 emitted from the electron gun 201 (emission source) is illuminated almost perpendicularly by the electromagnetic lens 202 onto the entire shaping aperture array substrate 203. As shown in FIG. 2, a plurality of holes 22 (openings) are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates the area including all of the plurality of holes 22. Each portion of the electron beam 200 irradiated onto the positions of the plurality of holes 22 passes through each of the plurality of holes 22 of the shaping aperture array substrate 203, thereby forming a multi-primary electron beam (multi-beam) 20.

The formed multi-beam 20 is deflected by the electromagnetic lens (reduction lens) 205 and the electromagnetic lens 206, respectively, and while repeating intermediate images and crossovers, passes through the beam separator 214 arranged at the crossover position of each beam of the multi-beam 20 and proceeds to the objective lens 207. The objective lens 207 then focuses the multi-beam 20 on the substrate 101. The multi-beam 20 focused on the substrate 101 (sample) surface by the objective lens 207 is deflected collectively by the deflector 208 and irradiated on the respective irradiation positions on the substrate 101 of each beam. Note that when the entire multi-beam 20 is deflected collectively by the collective blanking deflector 212, it moves out of position from the hole in the center of the limiting aperture substrate 213 and is blocked by the limiting aperture substrate 213. On the other hand, the multi-beams 20 that are not deflected by the collective blanking deflector 212 pass through a hole in the center of the limiting aperture substrate 213 as shown in FIG. 1. Blanking control is performed by turning the collective blanking deflector 212 ON/OFF, and the beams are collectively controlled to be ON/OFF. In this way, the limiting aperture substrate 213 blocks the multi-beams 20 that are deflected by the collective blanking deflector 212 to be in the beam OFF state. Then, the multi-beams 20 for inspection (for image acquisition) are formed by a group of beams that pass through the limiting aperture substrate 213 from when the beams are turned ON until when they are turned OFF.

When the multi-beam 20 is irradiated onto a desired position on the substrate 101, a bundle of secondary electrons (multi-secondary electron beam 300) including reflected electrons corresponding to each beam of the multi-beam 20 is emitted from the substrate 101 as a result of the irradiation of the multi-beam 20.

The multiple secondary electron beams 300 emitted from the substrate 101 pass through the objective lens 207 and proceed to the beam separator 214.

Here, the beam separator 214 generates an electric field and a magnetic field in perpendicular directions on a plane perpendicular to the direction in which the central beam of the multi-beam 20 travels (the central axis of the electron orbit). The electric field exerts a force in the same direction regardless of the direction of electron travel. In contrast, the magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electrons can be changed depending on the direction in which the electrons enter. For the multi-beam 20 entering the beam separator 214 from above, the force due to the electric field and the force due to the magnetic field cancel each other out, and the multi-beam 20 travels straight downward. In contrast, for the multi-secondary electron beam 300 entering the beam separator 214 from below, the force due to the electric field and the force due to the magnetic field both act in the same direction, and the multi-secondary electron beam 300 is bent diagonally upward and separated from the multi-beam 20.

The multi-secondary electron beam 300, which is bent obliquely upward and separated from the multi-beam 20, is further bent by the deflector 218 and projected onto the multi-detector 222 while being refracted by the electromagnetic lenses 224 and 226. The multi-detector 222 detects the projected multi-secondary electron beam 300. The multi-detector 222 may project reflected electrons and secondary electrons, or may project secondary electrons that remain after the reflected electrons diverge midway. The multi-detector 222 has, for example, a two-dimensional sensor (not shown). Then, each secondary electron of the multi-secondary electron beam 300 collides with a corresponding area of the two-dimensional sensor, generating electrons, and generating secondary electron image data for each pixel. The intensity signal detected by the multi-detector 222 is output to the detection circuit 106.

3 is a conceptual diagram for explaining an example of the scanning operation in the first embodiment. In FIG. 3, the inspection area 30 of the substrate 101 is virtually divided into a plurality of stripe areas 32 in a rectangular shape with a predetermined width in the y direction, for example. It is suitable to apply the substrate 101 to, for example, an exposure mask substrate. For example, the substrate 101 is virtually divided into a plurality of stripe areas 32 in a rectangular shape with a width equal to a natural number multiple of the width of the irradiation area 34 that can be irradiated by one irradiation of the entire multi-beam 20. In the example of FIG. 3, the substrate 101 is virtually divided into a plurality of stripe areas 32 in a rectangular shape with the same width as the irradiation area 34. First, the XY stage 105 is moved to adjust the tracking area 33 so that the irradiation area 34 that can be irradiated by one irradiation of the multi-beam 20 is located at a position outside the first stripe area 32, for example, by one size of the irradiation area 34 from the left end of the first stripe area 32, and the scanning operation is started. In the first embodiment, the XY stage 105 is continuously moved in the -x direction (an example of the opposite direction to the first direction) at a constant speed, for example, and the irradiation area 34 is moved to follow the continuous movement while scanning the sub-area group arranged at pitch p in the desired tracking area 33. After the scanning is completed, the irradiation area 34 is moved to the next tracking area 33 in the x direction (an example of the first direction), thereby performing tracking reset. By repeating such an operation, the stripe area 32 is scanned in order in the x direction. When scanning the first stripe area 32, the XY stage 105 is moved in the -x direction, for example, to perform a scanning operation relatively in the x direction. After the multi-beam irradiation of the first stripe area 32 is completed, the stage position is moved in the -y direction, and the irradiation area 34 is adjusted to be located relatively in the y direction at a position, for example, one size to the right of the right end of the second stripe area 32, and then the XY stage 105 is moved in the x direction, for example, to perform multi-beam irradiation in the -x direction in the same manner. The inspection time can be reduced by scanning while alternating directions, such as irradiating the third stripe region 32 with multiple beams in the x direction and irradiating the fourth stripe region 32 with multiple beams in the -x direction. However, scanning while alternating directions is not limited to this, and scanning may proceed in the same direction when drawing each stripe region 32. The multiple beams 20 formed by passing through each hole 22 of the shaping aperture array substrate 203 simultaneously detect multiple secondary electron beams 300 consisting of a bundle of secondary electrons corresponding to a maximum of the same number of beams (primary electron beams) as each hole 22.

Figure 4 is a diagram showing an example of the irradiation area of the multi-beam and the measurement pixels in the first embodiment. In Figure 4, each stripe area 32 is divided into a plurality of mesh areas in a mesh shape, for example, by the beam size of the multi-beam. Each such mesh area becomes a measurement pixel 36 (unit irradiation area). Then, within the irradiation area 34, a plurality of measurement pixels 28 (irradiation positions of the beam at one shot painted black) that can be irradiated by one irradiation of N x N' multi-beams 20 are shown. In other words, the pitch p in the x and y directions between adjacent measurement pixels 28 becomes the pitch between each beam of the multi-beam 20 on the substrate 101. In the example of Figure 4, one of four adjacent measurement pixels 28 is set as one of the four corners of a rectangle, and a region surrounded by p x p in the x and y directions starting from that measurement pixel 28 (hereinafter referred to as p x p region 27) is divided by the division number M (M is an integer of 2 or more) in the x direction to form one grid 29 (sub-region; small region) as a rectangular region of size p/M in the x direction and p in the -y direction. The example of Figure 4 shows a case where each grid 29 (individual beam scan region) is composed of 3 x 9 pixels.

FIG. 5 is a conceptual diagram for explaining an example of details of a scan operation in a comparative example of the first embodiment. In the example of FIG. 5, as a comparative example of the first embodiment, N multibeams of one stage in the y direction out of N×N′ multibeams 20 are shown. A “stage” refers to the number of grids 29 or p×p areas arranged in the y direction. For example, “one stage” means that “one grid 29 or p×p area is arranged in the y direction”. Here, N=5 multibeams arranged in the x direction with the same pitch p are shown. In the comparative example of the first embodiment, each of the N=5 multibeams arranged in the x direction with the same pitch p scans all of the p×p areas 27 surrounded by p×p in the x and y directions starting from the measurement pixel 28 of the beam, and then scans the next p×p area 27 surrounded by p×p. In the comparative example of the first embodiment, the stage speed is controlled so that the XY stage 105 moves by N·p while each beam scans the area surrounded by p×p (the period t=t ₀ ′ to t ₁ ′). At that time, the deflector 208 performs tracking deflection so that each beam can scan the area surrounded by the p×p by the deflection operation of the deflector 208. Then, at the time when the scanning of the p×p area 27 surrounded by N p×p arranged continuously in the x direction is completed (t=t ₁ '), tracking reset is performed by deflecting N=5 multi-beams collectively in the x direction so that the scanning areas do not overlap. By repeating such an operation, it is possible to scan the area on the continuously moving stage with the multi-beams so that the scanning areas do not overlap. In the example of FIG. 5, it is necessary to deflect the multi-beams by (N-1)·p (=4p) in the x direction (or -x direction). Therefore, in the comparative example of the first embodiment, the amplitude of the beam deflection in the x direction (or -x direction) is required by (N-1)·p. On the other hand, the amplitude of the beam deflection in the y direction (or -y direction) is required by p. If the number of beams N is large, the amplitude of the beam deflection becomes very large. Therefore, as described above, the influence of aberration in the electron optical system becomes large.

Figure 6 is a conceptual diagram for explaining an example of the details of the scanning operation in the first embodiment. In the example of Figure 6, as the first embodiment, out of the N x N' multi-beams 20, one stage of N multi-beams in the y direction is shown. Here, as in Figure 5, N = 5 multi-beams arranged in the x direction with the same pitch p are shown. In the first embodiment, one of the four adjacent measurement pixels 28 is set as one of the four corners of a rectangle, and the p x p region 27 surrounded by p x p in the x and y directions starting from the measurement pixel 28 is divided in the x direction by the division number M. Therefore, one grid 29 (sub-region; small region) is formed by a rectangular region of size p/M in the x direction and p (predetermined size) in the -y direction. The example of Figure 6 shows the case where the division number M = 3. In the first embodiment, N=5 multi-beams arranged in the x direction with the same pitch p are shown, each of which scans a grid 29 (sub-region) of size p/M in the x direction and p in the y direction (predetermined size) starting from the measurement pixel 28 of that beam, and then scans the next grid 29 that is N pixels away in the x direction.

6, in the first embodiment, while each beam scans the grid 29 surrounded by (p/M)×p (period t=t ₀ to t ₁ ), if the stage speed is the same as that of the comparative example in FIG. 5 , the XY stage 105 moves by N/M·p. At that time, the deflector 208 performs tracking deflection by the first function, with the grid 29 of size (p/M)×p arranged in N pieces at pitch p in the x direction as the tracking region 33, so that each beam can scan the grid 29 surrounded by (p/M)×p by deflection operation by the second function of the deflector 208. Then, at the time (t=t ₁ ) when scanning of the grid 29 of size (p/M)×p arranged in N pieces at pitch p in the x direction by the second function of the deflector 208 is completed, the deflector 208 uses the first function to collectively deflect N=5 multi-beams to positions separated by N grids 29 in the x direction so that the scanning regions do not overlap. In the example of FIG. 6, the deflector 208 uses the first function to collectively deflect five multi-beams to positions spaced apart by five grids 29. At this time, it goes without saying that the deflection position by the second function of the deflector 208 is reset from the last pixel 36 in the grid 29 to the first pixel 28. By repeating such an operation in the period t=t ₁ to t ₂ , the period t=t ₂ to t ₃ , and so on, it is possible to scan with the multi-beams so that the scanning areas do not overlap on the same stripe region 32 even when the stage is moved continuously. In the example of FIG. 6, it is necessary to deflect the multi-beams in the x direction by (N-1)/M·p (=4p/M). Therefore, in the first embodiment, the amplitude of the beam deflection in the x direction can be suppressed to (N-1)/M·p. However, if the relationship between the number of beams N in the x direction and the number of divisions M is not controlled, scanning omissions (missing teeth) or overlapping scanning grids 29 (sub-regions) will occur. In the first embodiment, in order to apply such a scanning method, a combination of values is used in which the greatest common divisor between the number of beams N in the x direction and the number of divisions M is 1. By setting such a condition, it is possible to avoid scan omissions (missing teeth) or overlapping scans.

Figure 7 is a diagram showing an example of the relationship between the number of beams and the number of divisions in the first embodiment. In Figure 7, a scanning operation is shown when the number of divisions M is changed using N = 7 x-direction beams. Also, in Figure 7, for ease of understanding, the beam is shown scanning a different stage each time a tracking reset is performed. Note that in Figure 7, for convenience, the size in the y direction of the p x p region 27 surrounded by p x p is narrowed. Figure 7 (a) shows the case where the number of divisions M = 1, that is, the p x p region 27 surrounded by p x p is not divided. In Figure 7 (a), when a tracking reset is performed, the amplitude of the beam deflection becomes large at 6p. In Figure 7 (b), the number of divisions M = 2, that is, the p x p region 27 surrounded by p x p is divided into two. In Figure 7 (b), when a tracking reset is performed, the amplitude of the beam deflection can be reduced to 3p. FIG. 7C shows a case where the number of divisions M=3, that is, the p×p region 27 surrounded by p×p is divided into three. FIG. 7C shows a case where the beam deflection amplitude can be reduced to 2p when performing tracking reset. FIG. 7D shows a case where the number of divisions M=4, that is, the p×p region 27 surrounded by p×p is divided into four. FIG. 7D shows a case where the beam deflection amplitude can be reduced to (3/2)p when performing tracking reset. FIG. 7E shows a case where the number of divisions M=5, that is, the p×p region 27 surrounded by p×p is divided into five. FIG. 7E shows a case where the beam deflection amplitude can be reduced to (6/5)p when performing tracking reset. FIG. 7F shows a case where the number of divisions M=6, that is, the p×p region 27 surrounded by p×p is divided into six. FIG. 7F shows a case where the beam deflection amplitude can be reduced to p when performing tracking reset. In this way, by increasing the number of divisions M, the amplitude of the beam deflection can be reduced.

Here, when one beam scans the sub-areas (grids 29) in which the p×p area 27 surrounded by p×p is divided into M, scanning with a multi-beam 20 having N beams in the x direction will result in N sub-areas (grids 29) arranged every M being scanned simultaneously. Here, a group of M×N consecutive sub-areas (grids 29) is taken as one predetermined range. If the first beam of the multi-beam 20 moves a predetermined range in the x direction, the sub-area that was not scanned will remain as it is without being scanned. Here, if the number of sub-areas to be skipped (amount of movement) when performing a tracking reset is D, M×N/D tracking cycle operations will be performed while the first beam of the multi-beam 20 moves a predetermined range in the x direction. Therefore, in order to scan all of the sub-areas that were previously scanned only one at a time in the M direction without overlap and without omission, the division number M and the number of tracking cycle operations must be the same, that is, M=M×N/D. Therefore, D=N. Therefore, in the first embodiment, the number D of sub-regions to jump over when performing a tracking reset is the same as the number N of beams in the x direction. Also, the beam amplitude at that time is (N-1)p/M.

When N sub-areas (grids 29) arranged every M are scanned simultaneously and the number of sub-areas skipped when performing a tracking reset is set to N, the following relationship is required to prevent the scanning ranges from overlapping in one specified range.
0,M,2M,3M,...,(N-1)M,NM
0,N,2N,3N,...,(M-1)N,MN

It is necessary to ensure that these two sequences do not end up with the same value midway. Therefore, a combination of the number of beams N in the x direction and the number of divisions M with a greatest common divisor of 1 (a mutually prime relationship between the number of beams N and the number of divisions M) is required. In the example of Figures 7(a) to 7(f), when the number of divisions M = 7, the same value will occur midway. Specifically, when performing a tracking reset, the sub-area after the movement has already been scanned by the adjacent beam, so there will be an overlap and this is not OK.

It is even more preferable to use a prime number as the value of the number of beams N, as shown in the examples of Figures 7(a) to 7(f). By setting the number of beams N to a prime number (e.g., 2, 3, 5, 7, 11, 13, 17, 23, ...), the degree of freedom for the number of divisions M can be dramatically increased.

Figure 8 is a diagram showing the relationship between the sub-region 29 and the scanning region in the first embodiment. Figure 8 shows a diagram in which an area surrounded by beam pitch p x p is divided into three in the x direction. As shown in Figure 8, when each beam of the multi-beam 20 scans a corresponding sub-region (grid 29), it is preferable to set the scanning region 31 of each beam so that it partially overlaps with the adjacent sub-region (grid 29). The adjacent sub-regions (grid 29) are scanned with different beams of the multi-beam 20. Therefore, due to the influence of aberration of the optical system, the inter-beam pitch p deviates from the equal pitch. Therefore, it is preferable to provide a margin width α that can absorb such deviation. Therefore, it is preferable that the scanning region 31 when actually scanning is an area that is added with a margin width α to at least one end side of both ends in the x direction from the sub-region (grid 29). Note that by adding such a margin, the scanning end position moves in the x direction by the margin width α. If a margin width α is provided on both sides, the scanning start position will also move in the -x direction by the margin width α. Figure 8 shows the case where a margin width α is added in the x direction, but it is even more preferable to add a margin width α in the y direction as well.

As explained in FIG. 7, the beam amplitude can be reduced by increasing the division number M. Therefore, from the viewpoint of reducing the beam amplitude, a larger division number is desirable. On the other hand, increasing the division number M increases the number of sub-regions (grids 29), which increases the number of overlapping parts and increases the amount of wasted image data. This increases the amount of data. Therefore, from the viewpoint of reducing the amount of data, a smaller division number is desirable. Therefore, it is more preferable to select the minimum value of the division number M that can obtain a beam amplitude that can ignore the effects of aberrations in the electron optical system.

Figure 9 is a schematic diagram showing an example of a scanning operation in the first aspect of the first embodiment. Note that, although actual scanning is performed by scanning the beam on each measurement pixel 28 as shown in Figure 4, the scanning operation is shown here by using arrows to illustrate it for ease of understanding. Note that, in Figure 9, the x direction to the right on the paper is the first direction, the -x direction to the left on the paper is the opposite direction to the first direction (stage movement direction), the y direction to the top on the paper is the second direction, and the -y direction to the bottom on the paper is the opposite direction to the second direction.

Figure 9(a) shows the first step of the scanning operation. In the first step, the beam is deflected along the y direction. Here, the deflection of the beam in the first step is performed starting from the end 29a (e.g., the bottom of the end 29a) on the -x direction side of the grid 29 and ending at the end 29b (e.g., the top of the end 29b) on the x direction side of the grid 29. Also, the deflection of the beam in the first step is repeatedly performed from the end 29a on the -x direction side of the grid 29 to the end 29b on the x direction side of the grid 29. Therefore, as an example of scanning the beam in Figure 9(a), first, scanning is performed from (1) to (2), then scanning is performed from (3) to (4), and then scanning is performed from (5) to (6). For example, scanning from (1) to (2) is scanning the pixel 28 provided at the end 29a on the -x direction side in the grid 29. For example, scanning from (5) to (6) is a scan of pixel 28 located at end 29b on the x-direction side of grid 29. Scanning from (3) to (4) is a scan of pixel 28 located between end 29a on the -x-direction side and end 29b on the x-direction side of grid 29. Note that during this series of scans, XY stage 105 continues to move in the -x direction, so grid 29 also continues to move in the -x direction.

Figure 9(b) shows the second step of the scanning operation. In the second step, the beam is deflected along the -y direction. Here, the deflection of the beam in the second step is performed starting from the end 29a (e.g., the top of the end 29a) on the -x direction side of the grid 29 and ending at the end 29b (e.g., the bottom of the end 29b) on the x direction side of the grid 29. Also, the deflection of the beam in the second step is repeatedly performed from the end 29a on the -x direction side of the grid 29 to the end 29b on the x direction side of the grid 29. Therefore, as an example of scanning the beam in Figure 9(b), first, scanning is performed from (19) to (20), then scanning is performed from (21) to (22), and then scanning is performed from (23) to (24). For example, scanning from (19) to (20) is scanning the pixel 28 provided at the end 29a on the -x direction side of the grid 29. For example, the scan from (23) to (24) is a scan of the pixel 28 located at the end 29b on the x-direction side of the grid 29. The scan from (21) to (22) is a scan of the pixel 28 located between the end 29a on the -x-direction side and the end 29b on the x-direction side of the grid 29. Note that during this series of scans, the XY stage 105 continues to move in the -x direction, so the grid 29 also continues to move in the -x direction.

The scanning operation is performed by performing the above first and second steps in sequence.

Figure 10 is a schematic diagram showing another example of the scanning operation in the first aspect of the first embodiment. It differs from Figure 9 in that the y direction, which is the upward direction on the page, is the opposite direction to the second direction, and the -y direction, which is the downward direction on the page, is the second direction. Also, Figure 10(a) differs from Figure 9(a) in that the beam is deflected along the -y direction. Also, Figure 10(b) differs from Figure 9(b) in that the beam is deflected along the +y direction.

When the beam scan time in the y direction or the -y direction, including the second beam settling time Ofs_v in the y direction or the -y direction, is Tv, the moving speed V of the XY stage 105 is V = PS N / (2Tv). This is derived as follows. First, the area of the grid 29 covered by one beam is (p/M) x p. The distance that the XY stage 105 moves from the start to the completion of the beam scan on the grid 29, which is (p/M) x p, is N/M·p, as described in paragraph 0035. Next, the size of the measurement pixel 28 in the x direction and y direction is PS, and the time required for the beam scan in the y direction is Tv. In this case, the scan time in the y direction can be calculated by (p/(M x PS)) x Tv. 9 and 10, the polarity is changed in the y direction and scanning is performed twice (y direction and -y direction), so the following equation is established: ((p/(M×PS))×Tv×2)×V= N/M·p . Therefore, V=PS N /(2Tv)). The movement speed V of the XY stage 105 described above is calculated by, for example, the movement speed calculation circuit 146.

Next, the beam scan time Tv in the y or -y direction is Tv = (p/PS) x (p/M/PS) x (1/f) + (p/M/PS) x Ofs_v. Here, f is the scan frequency used for beam scanning. (p/PS) x (p/M/PS) is the number of measurement pixels 28 in the grid 29. Therefore, the term (p/PS) x (p/M/PS) x (1/f) is the term corresponding to the time required to irradiate each measurement pixel 28 in the grid 29 with the beam. Next, (p/M/PS) x Ofs_v is the term of the time required to return the beam to scan in the same direction. Therefore, the sum of these is derived as Tv = (p/PS) x (p/M/PS) x (1/f) + (p/M/PS) x Ofs_v. The scan frequency is stored, for example, in the scan frequency storage device 141.

Figure 11 is a schematic diagram showing an example of a scanning operation in the second aspect of the first embodiment. In Figure 11, the x direction to the right on the paper is the first direction, the -x direction to the left on the paper is the opposite direction to the first direction (stage movement direction), the y direction to the top on the paper is the second direction, and the -y direction to the bottom on the paper is the opposite direction to the second direction.

Figure 11 (a) shows the first step of the scanning operation. In the first step, the beam is deflected along the y direction. Here, the deflection of the beam in the first step is performed starting from the end 29a (e.g., the bottom of the end 29a) on the -x direction side of the grid 29 and ending at the end 29b (e.g., the top of the end 29b) on the x direction side of the grid 29. Also, the deflection of the beam in the first step is repeatedly performed from the end 29a on the -x direction side of the grid 29 to the end 29b on the x direction side of the grid 29. Therefore, as an example of scanning the beam in Figure 11 (a), first, scanning is performed from (1) to (2), then scanning is performed from (3) to (4), and then scanning is performed from (5) to (6). For example, scanning from (1) to (2) is scanning the pixel 28 provided at the end 29a on the -x direction side of the grid 29. For example, scanning from (5) to (6) is a scan of pixel 28 located at end 29b on the x-direction side of grid 29. Scanning from (3) to (4) is a scan of pixel 28 located between end 29a on the -x-direction side and end 29b on the x-direction side of grid 29. Note that during this series of scans, XY stage 105 continues to move in the -x direction, so grid 29 also continues to move in the -x direction.

Figure 11 (b) shows the second step of the scanning operation. In the second step, the beam is deflected along the -x direction. Here, the deflection of the beam in the second step is performed starting from the end 29c (for example, the right end of the end 29c) on the -y direction side of the grid 29 and ending at the end 29d (for example, the left end of the end 29d) on the y direction side of the grid 29. Also, the deflection of the beam in the second step is repeatedly performed from the end 29c on the -y direction side of the grid 29 to the end 29d on the y direction side of the grid 29. Therefore, as an example of the scanning of the beam in Figure 11 (b), first, scanning is performed from (7) to (8), then scanning is performed from (9) to (10), and then scanning is performed from (11) to (12). Note that during the series of scans, the XY stage 105 continues to move in the -x direction, and therefore the grid 29 also continues to move further in the -x direction.

Figure 11(c) shows the third step of the scanning operation. In the third step, the beam is deflected along the x direction. Here, the deflection of the beam in the second step is performed starting from the end 29c (for example, the left end of the end 29c) on the -y direction side of the grid 29 and ending at the end 29d (for example, the right end of the end 29d) on the y direction side of the grid 29. Also, the deflection of the beam in the third step is repeatedly performed from the end 29d on the y direction side of the grid 29 to the end 29c on the -y direction side of the grid 29. Therefore, as an example of the scanning of the beam in Figure 11(c), first, scanning is performed from (13) to (14), then scanning is performed from (15) to (16), and then scanning is performed from (17) to (18). Note that during the series of scans, the XY stage 105 continues to move in the -x direction, and therefore the grid 29 also continues to move further in the -x direction.

Figure 11(d) shows the fourth step of the scanning operation. In the fourth step, the beam is deflected along the -y direction. Here, the deflection of the beam in the fourth step is performed starting from the end 29a (e.g., the top of the end 29a) on the -x direction side of the grid 29 and ending at the end 29b (e.g., the bottom of the end 29b) on the x direction side of the grid 29. Also, the deflection of the beam in the fourth step is repeatedly performed from the end 29a on the -x direction side of the grid 29 to the end 29b on the x direction side of the grid 29. Therefore, as an example of the scanning of the beam in Figure 11(d), first, scanning is performed from (19) to (20), then scanning is performed from (21) to (22), and then scanning is performed from (23) to (24). For example, scanning from (19) to (20) is a scan of pixel 28 provided at end 29a on the -x direction side of grid 29. For example, scanning from (23) to (24) is a scan of pixel 28 provided at end 29b on the x direction side of grid 29. And scanning from (21) to (22) is a scan of pixel 28 provided between end 29a on the -x direction side and end 29b on the x direction side of grid 29. Note that during the series of scans, XY stage 105 continues to move in the -x direction, and therefore grid 29 also continues to move in the -x direction.

The scanning operation is performed by carrying out the above first, second, third and fourth steps in order.

Figure 12 is a schematic diagram showing another example of the scanning operation in the second aspect of the first embodiment. In Figures 11(b) and 11(c), the scanning is repeated from end 29c on the -y direction side of grid 29 to end 29d on the y direction side of grid 29, whereas in Figures 12(b) and 12(c), the scanning is repeated from end 29d on the y direction side of grid 29 to end 29c on the -y direction side of grid 29.

Figure 13 is a schematic diagram showing another example of the scanning operation in the second aspect of the first embodiment. It differs from Figure 11 in that the y direction, which is the upward direction on the page, is the opposite direction to the second direction, and the -y direction, which is the downward direction on the page, is the second direction. Also, Figure 13(a) differs from Figure 11(a) in that the beam is deflected along the -y direction. Also, Figure 13(d) differs from Figure 11(d) in that the beam is deflected along the +y direction.

Figure 14 is a schematic diagram showing another example of the scanning operation in the second aspect of the first embodiment. In Figures 13(b) and 13(c), scanning is repeatedly performed from end 29c on the -y direction side of grid 29 to end 29d on the y direction side of grid 29, whereas in Figures 14(b) and 14(c), scanning is repeatedly performed from end 29d on the y direction side of grid 29 to end 29c on the -y direction side of grid 29.

When the beam scan time in the x direction or the -x direction, including the first beam settling time Ofs_h in the x direction or the -x direction, is Th, and the beam scan time in the y direction or the -y direction, including the second beam settling time Ofs_v in the y direction or the -y direction, is Tv, the moving speed V of the XY stage 105 is V = PS N / (2 x (M x Th + Tv)). This is derived as follows. First, the area of the grid 29 covered by one beam is (p/M) x p. The distance that the XY stage 105 moves from the start of the beam scan on the grid 29, which is (p/M) x p, to the completion is N/M · p, as described in paragraph 0035. Next, the size of the measurement pixel 28 in the x direction and y direction is PS, and the time required for the beam scan in the x direction is Th, and the time required for the beam scan in the y direction is Tv. In this case, the scan time in the x direction can be calculated by (p/PS) x Th. Also, the scan time in the y direction is calculated by (p/(M×PS))×Tv. Then, as shown in FIG. 11 to FIG. 14, two scans are performed in the x direction by changing the polarity (x direction and −x direction), and two scans are performed in the y direction by changing the polarity (y direction and −y direction), so the following equation is established: ((p/(M×PS))×Tv×2+(p/PS)×Th×2)×V= N/M·p . Therefore, V=PS N /(2×(M×Th+Tv)). The movement speed V of the XY stage 105 described above is calculated by, for example, the movement speed calculation circuit 146.

Next, the beam scan time Th in the x direction or the -x direction is Th = (p/PS) x (p/M/PS) x (1/f) + (p/PS) x Ofs_h. Here, f is the scan frequency used for beam scanning. (p/PS) x (p/M/PS) is the number of measurement pixels 28 in the grid 29. Therefore, the term (p/PS) x (p/M/PS) x (1/f) is the term corresponding to the time required to irradiate each measurement pixel 28 in the grid 29 with the beam. Next, (p/PS) x Ofs_h is the term of the time required to return the beam to scan in the same direction. Therefore, the sum of these is derived as Th = (p/PS) x (p/M/PS) x (1/f) + (p/PS) x Ofs_h. The scan frequency is stored, for example, in the scan frequency storage device 141.

Similarly, the beam scan time Tv in the y or -y direction is Tv = (p/PS) x (p/M/PS) x (1/f) + (p/M/PS) x Ofs_v.

The first beam settling time Ofs_h and the second beam settling time Ofs_v are stored in the settling time storage device 140. The first beam settling time Ofs_h and the second beam settling time Ofs_v may be input by an operator using the control computer 110, for example, and stored in the settling time storage device 140. The beam scan time Th and the beam scan time Tv are calculated, for example, by the scan time calculation circuit 148 based on the above formula. The calculated beam scan time Th and beam scan time Tv may be stored, for example, in the scan time storage device 149.

Figure 15 is a schematic diagram showing an example of a scanning operation in another comparative example of embodiment 1.

In FIG. 15(a), the beam is scanned along the -x direction in the first step as shown in FIG. 11(a), for example. In this case, particularly in scanning the end 29b of the grid 29 on the x direction side as shown in (1), (3), and (5) of FIG. 15(a), if the grid 29 protrudes from the tracking region 33 in the -x direction corresponding to the movement direction of the XY stage 105, the beam is not irradiated to the end 29b of the grid 29 on the x direction side, making it impossible to perform inspection. On the other hand, FIG. 15(b) shows the beam being scanned along the x direction. In this case, particularly in scanning the end 29a of the grid 29 on the -x direction side as shown in (2), (4), and (6) of FIG. 15(b), if the grid 29 protrudes from the tracking region 33 in the -x direction corresponding to the movement direction of the XY stage 105, the beam is not irradiated to the end 29a of the grid 29 on the -x direction side, making it impossible to perform inspection. To avoid this problem, it is preferable to perform beam scanning along the y or -y direction in the first step.

Figure 15(c) shows, for example, the fourth step shown in Figure 11(d), where the beam is scanned along the -x direction. In this case, particularly in scanning the end 29a of the grid 29 on the -x direction side, as in (20), (22), and (24), if the grid 29 protrudes from the tracking region 33 in the x direction corresponding to the direction opposite to the movement direction of the XY stage 105, the beam is not irradiated to the end 29a of the grid 29 on the -x direction side, making it impossible to perform inspection. On the other hand, Figure 15(d) shows, for scanning the beam along the x direction. In this case, particularly in scanning the end 29b of the grid 29 on the x direction side, as in (19), (21), and (23), if the grid 29 protrudes from the tracking region 33 in the x direction corresponding to the direction opposite to the movement direction of the XY stage 105, the beam is not irradiated to the end 29b of the grid 29 on the x direction side, making it impossible to perform inspection. To avoid this problem, it is preferable to perform beam scanning in the y or -y direction in the fourth step.

In view of the above, it is preferable that beam scanning along the x direction or the -x direction is performed in the second or third step. And it is preferable that beam scanning along the y direction or the -y direction is performed in the first or fourth step.

Figure 16 is a schematic diagram showing an example of a scanning operation in another comparative example of the first embodiment. In Figure 16(a), for example, in the first step as shown in Figure 11(a), the beam is scanned along the y direction. However, unlike Figure 11(a), for example, scanning is performed with the end 29b of the grid 29 on the x direction side as the starting point and the end 29a of the grid 29 on the -x direction side as the end point. In this case, especially in scanning the end 29b of the grid 29 on the x direction side as shown in (1) and (2) of Figure 16(a), if the grid 29 protrudes from the tracking region 33 in the -x direction corresponding to the movement direction of the XY stage 105, the beam is not irradiated to the end 29b of the grid 29 on the x direction side, and inspection cannot be performed.

In FIG. 16(b), the beam is scanned along the -y direction in the fourth step as shown in FIG. 11(d). However, unlike FIG. 11(d), scanning is performed starting from the end 29b of the grid 29 on the x direction side and ending from the end 29a of the grid 29 on the -x direction side. In this case, particularly in scanning the end 29a of the grid 29 on the -x direction side as shown in (23) and (24) in FIG. 16(b), if the grid 29 protrudes from the tracking region 33 in the x direction, which corresponds to the opposite direction to the movement direction of the XY stage 105, the beam is not irradiated to the end 29a of the grid 29 on the -x direction side, and inspection is not possible.

In view of the above, it is preferable that the beam scan in the first step is performed with the end 29a of the grid 29 on the -x direction side as the starting point and the end 29b of the grid 29 on the x direction side as the end point. The grid 29 continues to move in the -x direction even during the beam scan. Therefore, when the beam scan is performed from the -x direction to the x direction, the grid 29 has already moved further in the -x direction by the time the end of the grid 29 on the x direction side is scanned. Therefore, at this time, there is less risk that unintended vibrations applied to the XY stage 105 will cause the grid 29 to jump out of the tracking region 33, making it impossible to perform the inspection.

Similarly, it is preferable that the beam scan in the fourth step is performed with the end 29a of the grid 29 on the -x direction side as the starting point and the end 29b of the grid 29 on the x direction side as the end point. The grid 29 continues to move in the -x direction even during the beam scan. Therefore, when the beam scan is performed from the -x direction to the x direction, the grid 29 is still in a position closer to the x direction when the end of the grid 29 on the -x direction side is scanned. Therefore, at this time, there is less risk that unintended vibrations applied to the XY stage 105 will cause the grid 29 to jump out of the tracking region 33, making it impossible to perform the inspection.

Figure 17 is a flow chart showing some of the main steps of the inspection method in embodiment 1. Figure 17 shows the main steps of the inspection method from the start to the end of scanning. In Figure 17, the inspection method in embodiment 1 performs a series of steps, including a substrate transport step (S102), an inspection position movement step (S104), a stage movement step (start of constant speed movement) (S106), a sub-area scanning step (first step) (S108a), a sub-area scanning step (second step) (S108b), a sub-area scanning step (third step) (S108c), a sub-area scanning step (fourth step) (S108d), a determination step (S110), a tracking reset step (S112), a determination step (S114), and a stripe movement step (S116).

In the substrate transport process (S102), the substrate 101 is transported into the inspection chamber 103 using a transport mechanism (not shown) and placed on the XY stage 105.

In the inspection position movement step (S104), under the control of the stage control circuit 114, the drive mechanism 142 moves the XY stage 105 so that the inspection position is within a position where the multi-beam 20 can be irradiated. First, the XY stage 105 is moved so that the irradiation area 34 of the multi-beam 20 is positioned on the left end side of the stripe area 32 (e.g., two sizes outside the irradiation area 34).

In the stage movement process (start of uniform-speed continuous movement) (S106), under the control of the stage control circuit 114, the drive mechanism 142 moves the XY stage 105 at a uniform speed, for example, in the -x direction at a movement speed V. This starts uniform-speed continuous movement.

In the case of the embodiment shown in Figures 11 to 14, in the sub-area scanning process (first process) (S108a), sub-area scanning process (second process) (S108b), sub-area scanning process (third process) (S108c) and sub-area scanning process (fourth process) (S108d), the electron-optical image acquisition mechanism 150a scans a plurality of grids 29 (sub-areas; small areas) in which the stripe area 32, which is the inspection area of the substrate 101, is divided by a size obtained by p/M (M is an integer of 2 or more) in the x direction and by p (a predetermined size) in the y direction, for each group of N x N' grids 29. Specifically, tracking is started by deflecting N×N' multibeams 20 collectively onto a group of N×N' grids 29 on the substrate 101, which are arranged with N grids 29 arranged at a pitch p in the x direction and N' grids 29 arranged in the y direction, and while the XY stage 105 moves continuously in the -x direction by a distance obtained by N/M·p, the group of N×N' grids 29 is scanned while deflecting the multibeams 20 for tracking so as to follow the continuous movement of the XY stage 105. Then, a first secondary electron image is acquired in a first step, a second secondary electron image is acquired in a second step, a third secondary electron image is acquired in a third step, and a fourth secondary electron image is acquired in a fourth step. In addition, an average image acquisition circuit 144 is used to acquire an average secondary electron image from the first secondary electron image, the second secondary electron image, the third secondary electron image, and the fourth secondary electron image. The acquired average secondary electron image is stored in, for example, the image storage device 132. In the case of the embodiment shown in FIG. 9 and FIG. 10, a sub-area scanning process (first process) (S108a) and a sub-area scanning process (second process) (S108b) are performed. Then, a first secondary electron image is acquired in the first process, and a second secondary electron image is acquired in the second process. Then, an average secondary electron image is acquired from the first secondary electron image and the second secondary electron image using the average image acquisition circuit 144.

Figure 18 is a conceptual diagram for explaining another example of the details of the scanning operation in the first embodiment. The multi-beam 20 is composed of a plurality of electron beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on the surface of the substrate 101 in the x direction (first direction) and in N' rows (N' is an integer of 1 or more) at the same pitch p (predetermined size) in the y direction (second direction) perpendicular to the x direction. In the example of Figure 18, as such N x N' multi-beams 20, 5 x 5 multi-beams arranged in the x direction and y direction on the surface of the substrate 101 at the same pitch p are shown. Note that the pitch in the y direction may be different from that in the x direction. One of the four adjacent measurement pixels 28 is set as one of the four corners of a rectangle, and the p x p region 27 surrounded by p x p in the x and y directions starting from the measurement pixel 28 is divided in the x direction by the division number M. Therefore, one grid 29 (sub-region; small region) is composed of a rectangular region with a size of p/M in the x direction and p in the -y direction. Therefore, the example in Figure 18 shows a case where the number of divisions M = 3. The example in Figure 18 shows a case where each beam of the 5 x 5 multi-beam scans its corresponding grid 29 (sub-region), and after scanning, scans the next grid 29 that is N (here, 5) apart in the x direction.

First, under the control of the deflection control circuit 128, the first function of the deflector 208 is to deflect the multibeam 20 collectively to a group of N×N' grids 29 on the substrate 101 arranged at a pitch p in the x direction and N' in the y direction, among the multiple grids 29 obtained by dividing the stripe region 32 (inspection region) of the substrate 101 by a size obtained by p/M (M is an integer of 2 or more) in the x direction and a size of p in the y direction. Here, the group of N×N' grids 29 arranged at a pitch p in the x direction among the multiple grids 29 in the irradiation region 34 of the multibeam 20 is deflected as a tracking region 33. The main deflector 208 deflects the multibeam 20 collectively to a reference position (e.g., the center) of the tracking region 33. Then, the main deflector 208 performs tracking deflection of the multibeam 20 so as to follow the continuous movement of the XY stage 105.

Under the control of the deflection control circuit 128, the second function of the deflector 208 is to deflect the multi-beams 20 collectively so that each beam of the multi-beams 20 is positioned, for example, at the first pixel 36 in the x direction and the last pixel 36 in the y direction of the corresponding grid 29. In practice, the multi-beams 20 are deflected collectively so that each beam of the multi-beams 20 is positioned, for example, at the first pixel 36 in the x direction and the topmost pixel 36 in the y direction of the scanning area 31 obtained by adding a margin to the corresponding grid 29. Then, while the multi-beams 20 are deflected for tracking to follow the continuous movement of the XY stage 105, the multi-beams 20 are deflected collectively so as to scan a group of N x N' grids 29 (specifically, the scanning area 31) set as the tracking area 33. Then, during each shot, each beam irradiates one measurement pixel 36 corresponding to the same position in the assigned grid 29. In the example of FIG. 18, each beam irradiates the measurement pixel 36 that is the first from the left in the top row of the assigned grid 29 in the first shot. Then, the deflector 208 shifts the beam deflection position of the entire multibeam 20 by one measurement pixel 36 in the −y direction, and in the second shot, the first measurement pixel 36 from the left in the second row from the top in the assigned grid 29 is irradiated. This scanning is repeated, and after irradiation of the first measurement pixel 36 from the left in the bottom row is completed, the deflector 208 shifts the beam deflection position of the entire multibeam 20 by one measurement pixel 36 in the x direction, while shifting the beam deflection position to the second measurement pixel 36 from the left in the top row. This operation is repeated, and while the XY stage 105 moves continuously in the −x direction by a distance obtained by N/M·p, all measurement pixels 36 in one grid 29 are irradiated in order with one beam. This operation is performed simultaneously for N×N' multibeams 20. In one shot, the multi-beam 20 formed by passing through each hole 22 of the shaping aperture array substrate 203 detects a multi-secondary electron beam 300 consisting of a bunch of secondary electrons corresponding to a plurality of shots up to the same number as each hole 22 at once. The first function of the deflector 208 is to deflect the multi-beam 20 to follow the movement of the XY stage 105 so that the deflection position does not shift due to the movement of the XY stage 105 until all the measurement pixels 36 in the grid 29 covered by the multi-beam 20 have been scanned (tracking operation).

In the detection process, the multi-detector 222 detects secondary electrons emitted from the substrate 101 due to irradiation of the substrate 101 with the multi-beam 20. Each beam scans a corresponding grid 29. Each time the multi-beam 20 is shot, secondary electrons are emitted upward from the irradiated measurement pixel 36. In this way, the multi-detector 222 detects secondary electrons emitted from the substrate 101 due to irradiation of the substrate 101 with the multi-beam 20. The multi-detector 222 detects the multi-secondary electron beams 300 emitted upward from each measurement pixel 36 for each measurement pixel 36.

In the determination step (S110), the control computer 110 determines whether scanning of all grids 29 in the target stripe region 32 has been completed when the multi-beams 20 have scanned all measurement pixels 36 in the grids 29 (specifically, the scanning region 31) that they are responsible for. If scanning of all grids 29 in the target stripe region 32 has been completed, the process proceeds to the determination step (S114). If scanning of all grids 29 in the target stripe region 32 has not been completed, the process proceeds to the tracking reset step (S112).

In the tracking reset step (S112), when all measurement pixels 36 in the grids 29 (specifically, the scanning area 31) assigned to each of the deflectors 20 are scanned by the multi-beams 20 through the deflection operation, which is the second function of the deflector 208, the deflector 208 performs a tracking reset by collectively deflecting the multi-beams 20 to a new group of N x N' grids 29 (specifically, the scanning area 31) arranged at a pitch p in the x direction and N grids away in the x direction from the group of N x N' grids 29, by the time the movement of the XY stage 105 in the -x direction by the distance obtained by N/M·p is completed.

In the example of FIG. 18, a new group of N×N' grids 29 (specifically, scanning areas 31) spaced five apart in the x direction is reset to a new tracking area 33. The deflector 208 then uses its first function to perform tracking deflection of the multi-beam 20 so that it follows the continuous movement of the XY stage 105. During tracking reset, the deflector 20 also uses its second function to collectively deflect the multi-beam 20 so that each beam of the multi-beam 20 is positioned at, for example, the first pixel 36 in the x direction and the last pixel 36 in the y direction of the corresponding grid 29 (specifically, scanning area 31).

Then, the tracking cycle from the start of tracking to the tracking reset, and the scanning during tracking are repeated. In other words, as described above, while the multi-beam 20 is being deflected for tracking so as to follow the continuous movement of the XY stage 105, a group of N x N' grids 29 (specifically, scanning areas 31) set as the tracking area 33 is scanned. By repeating this operation, all pixels 36 in the stripe area 32 can be scanned.

Note that, although the first shot, second shot, etc. have been described here as separate shots, the multi-beam 20 may perform a raster scan operation in which the deflection position is moved while continuing to irradiate the beam without turning the beam on and off for each pixel 36. Also, it is not limited to scanning each pixel row lined up in the y direction in the same direction. After scanning the first pixel row in the x direction in the -y direction, the second pixel row may be scanned in the y direction (reverse direction).

Figure 19 is a conceptual diagram for explaining an example of the relationship between sub-regions and corresponding beams in the scan operation in the first embodiment. In the example of Figure 19, a case where 5 x 5 multi-beams 20 arranged at the same pitch p in the x and y directions are used is shown. Also, a case where the number of divisions M = 3 is shown. Also, in the example of Figure 19, the width (y-direction size) of the stripe region 32 is divided according to the size of the irradiation region 34. Therefore, the stripe region 32 is divided into a plurality of grids 29 with an x-direction size of p/M (= p/3) and a y-direction size of p. In the example of Figure 19, such a plurality of grids 29 are divided into five stages in the y direction, and the plurality of grids 29 in the x direction of each stage are scanned by N (= 5) multi-beams 20 in the x direction that are responsible for the same stage. As shown in Figure 19, the grids 29 scanned by the five beams (1 to 5) in each stage during the nth tracking cycle are indicated by 1-(n), 2-(n), 3-(n), 4-(n), and 5-(n), respectively. When resetting the nth tracking, the deflector 208 is used to deflect the grid 29 N (=5) ahead, so the grid 29 5 ahead becomes the grid 29 scanned in the n+1th tracking cycle. The grids 29 scanned during the n+1th tracking cycle are indicated by 1-(n+1), 2-(n+1), 3-(n+1), 4-(n+1), and 5-(n+1), respectively. By repeating the same operation, all grids 29 can be scanned.

For example, in the p x p region 27 of p x p that contains the grid 29 scanned by the first beam in the top row during the nth tracking cycle, there are two remaining grids 29 divided into thirds. The grid adjacent to the 1-(n) grid 29 in the x direction (right side) is scanned by the third beam during the n-1th tracking cycle. The grid adjacent to the 1-(n) grid in the x direction (right side) is scanned by the fifth beam during the n-2th tracking cycle. The scanning of the p x p region 27 is completed by these three tracking cycles. The same is true for each row in the y direction.

For example, in the p x p region 27 of p x p that contains the grid 29 scanned by the second beam in the top row during the nth tracking cycle, there are two remaining grids 29 divided into thirds. The grid adjacent to the 2-(n) grid 29 in the x direction (right side) is scanned by the fourth beam during the n-1th tracking cycle. The grid adjacent to the 2-(n) grid in the x direction (right side) is scanned by the first beam during the n+1th tracking cycle. Scanning within the p x p region 27 of p x p is completed by these three tracking cycles. The same is true for each row in the y direction.

For example, in the p x p region 27 of p x p that contains the grid 29 scanned by the third beam in the top row during the nth tracking cycle, there are two remaining grids 29 divided into thirds. The grid adjacent to the 3-(n) grid 29 in the x direction (right side) is scanned by the fifth beam during the n-1th tracking cycle. The grid adjacent to the 3-(n) grid in the x direction (right side) is scanned by the second beam during the n+1th tracking cycle. The scanning of the p x p region 27 of p x p is completed by these three tracking cycles. The same is true for each row in the y direction.

For example, in the p x p region 27 of p x p that contains the grid 29 scanned by the fourth beam in the top row during the nth tracking cycle, there are two remaining grids 29 divided into thirds. The grid adjacent to the 4-(n) grid 29 in the x direction (right side) is scanned by the first beam during the n+2th tracking cycle. The grid adjacent to the 4-(n) grid in the x direction (right side) is scanned by the third beam during the n+1th tracking cycle. The scanning of the p x p region 27 of p x p is completed by these three tracking cycles. The same is true for each row in the y direction.

For example, in the p x p region 27 of p x p that contains the grid 29 scanned by the fifth beam in the top row during the nth tracking cycle, there are two remaining grids 29 divided into thirds. The grid adjacent to the 5-(n) grid 29 in the x direction (right side) is scanned by the second beam during the n+2th tracking cycle. The grid adjacent to the 5-(n) grid in the x direction (right side) is scanned by the fourth beam during the n+1th tracking cycle. The scanning of the p x p region 27 of p x p is completed by these three tracking cycles. The same is true for each row in the y direction.

Therefore, when scanning the stripe region 32 using N=5 multi-beams with a division number M=3, the scanning operation will start from a position outside the end of the stripe region 32 on the scanning start side where the fifth beam can scan the grid 29 at least two tracking cycles in front.

By scanning using multiple beams 20 as described above, scanning operations (measurements) can be performed faster than when scanning with a single beam.

In the determination step (S114), the control computer 110 determines whether scanning of all stripes 32 has been completed. If scanning of all stripes 32 has been completed, the electro-optical image acquisition process ends. If scanning of all stripes 32 has not been completed, the process proceeds to the stripe movement step (S116).

In the stripe movement step (S116), under the control of the stage control circuit 114, the drive mechanism 142 moves the XY stage 105 so that the irradiation area 34 of the multi-beam 20 is positioned on the left side of the next stripe area 32 (e.g., one size outside the irradiation area 34). Then, the above-mentioned steps are repeated.

Figure 20 is a conceptual diagram for explaining another example of the scanning operation in the first embodiment. As shown in Figure 20, in the inspection area 330 of the substrate 101, for example, a plurality of chips 332 (dies) are formed in an array shape with a predetermined width in the x and y directions. Here, it is preferable to apply a semiconductor substrate (e.g., a wafer) as the substrate 101 to be inspected. Each chip 332 is formed on the substrate 101 with a size of, for example, 30 mm x 25 mm. The pattern inspection is performed for each chip 332. The area of each chip 332 is virtually divided into a plurality of stripe areas 32 with the same y-direction width as the irradiation area 34 that can be irradiated by irradiating the entire multi-beam 20 once. The scanning operation of each stripe area 32 may be the same as that described above. As described above, in the first embodiment, the XY stage 105 is continuously moved in the -x direction to continuously move the irradiation area 34 in the x direction relative to the XY stage 105, and each stripe area 32 is scanned by the multi-beam 20. Once scanning of all the stripe regions 32 has been completed, the stage position is moved in the -y direction, and the next stripe region 32 in the same row in the y direction is scanned in the same manner by the multi-beam 20. This operation is repeated, and once scanning of one chip 332 region is completed, the XY stage 105 is moved, and a similar scanning operation is performed on the stripe region 32 at the top of the next chip 332. By repeating this operation, all the chips 332 are scanned.

As described above, the electron optical image acquisition mechanism 150a uses the multi-beam 20, which is a plurality of electron beams, to scan the substrate 101 on which a graphic pattern is formed while continuously moving the XY stage 105, and detects the multi-secondary electron beam 300 emitted from the substrate 101 due to irradiation with the multi-beam 20. The method of scanning and the method of detecting the multi-secondary electron beam 300 are as described above. The detection data of the secondary electrons from each measurement pixel 36 detected by the multi-detector 222 is output to the detection circuit 106 in the order of measurement. In the detection circuit 106, the analog detection data is converted to digital data by an A/D converter (not shown) and stored in the stripe pattern memory 123. Then, when the detection data for one stripe region 32 (or chip 332) is accumulated, it is transferred to the comparison circuit 108 as stripe pattern data (or chip pattern data) together with information indicating each position from the position circuit 107.

Meanwhile, a reference image is created in parallel with or before or after the multi-beam scanning and secondary electron detection process.

As a reference image creation process, when the substrate 101 is a semiconductor substrate, the reference image creation units such as the expansion circuit 111 and the reference circuit 112 create a reference image of an area corresponding to a measurement image (electron optical image) of a frame area having a size equal to or smaller than a grid 29 composed of a plurality of pixels 36, which will be described later, based on exposure image data that defines an exposure image on the substrate when a mask pattern of an exposure mask is exposed and transferred to the semiconductor substrate. Instead of the exposure image data, drawing data (design data) that is the basis for forming an exposure mask that exposes and transfers a plurality of figure patterns to the substrate 101 may be used. When the substrate 101 is an exposure mask, the reference image creation units such as the expansion circuit 111 and the reference circuit 112 create a reference image of an area corresponding to a measurement image (electron optical image) of a frame area composed of a plurality of pixels 36, based on drawing data (design data) that is the basis for forming a plurality of figure patterns on the substrate 101.

Specifically, it operates as follows. First, the expansion circuit 111 reads out the drawing data (or exposure image data) from the storage device 109 through the control computer 110, converts each graphic pattern of each frame area defined in the read out drawing data (or exposure image data) into binary or multi-value image data, and this image data is sent to the reference circuit 112.

The figures defined in the drawing data (or exposure image data) are, for example, rectangles or triangles as basic figures, and the figure data stored defines the shape, size, position, etc. of each pattern figure using information such as the coordinates (x, y) at the reference position of the figure, the length of the sides, and a figure code that serves as an identifier to distinguish the type of figure, such as a rectangle or triangle.

When the drawing data (or exposure image data) that becomes such figure data is input to the expansion circuit 111, it is expanded to data for each figure, and the figure code and figure dimensions that indicate the figure shape of the figure data are interpreted. Then, binary or multi-value design image data is expanded as a pattern to be arranged in a grid with a grid of a predetermined quantization dimension as a unit, and output. In other words, the design data is read, the inspection area is virtually divided into grids with a predetermined dimension as a unit, the occupancy rate of the figure in the design pattern is calculated for each grid, and n-bit occupancy data is output. For example, it is preferable to set one grid as one pixel. Then, if one pixel has a resolution of 1/2 ⁸ (=1/256), a small area of 1/256 is assigned to the area of the figure arranged in the pixel, and the occupancy rate in the pixel is calculated. Then, the occupancy rate is output to the reference circuit 112 as 8-bit occupancy data. The grid may be the same size as the measurement pixel 36.

Next, the reference circuit 112 applies appropriate filtering to the design image data, which is the image data of the graphic image sent to it. The measurement data obtained as an optical image from the detection circuit 106 is in a state where a filter has been applied by the electro-optical system, in other words, in an analog state that changes continuously, so that it can be matched to the measurement data by also applying filtering to the design image data, which is the image data on the design side with digital image intensity (shade value). In this way, a design image (reference image) is created to be compared with the measurement image (optical image) of the frame area. The image data of the created reference image is output to the comparison circuit 108, and the reference images output to the comparison circuit 108 are each stored in memory.

Figure 21 is a diagram showing the internal configuration of the comparison circuit in the first embodiment. In Figure 21, the comparison circuit 108 includes storage devices 50 and 52 such as magnetic disk devices, a division unit 56, an alignment unit 58, and a comparison unit 60. Each "~ unit" such as the division unit 56, the alignment unit 58, and the comparison unit 60 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. In addition, each "~ unit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. The input data or the calculation results required for the division unit 56, the alignment unit 58, and the comparison unit 60 are stored in a memory (not shown) each time.

The transferred stripe pattern data (or chip pattern data) is temporarily stored in the storage device 50 together with information indicating each position from the position circuit 107. Similarly, the reference image data is temporarily stored in the storage device 52 together with information indicating each position in the design.

Next, the division unit 56 divides the stripe pattern data (or chip pattern data) into frame areas (unit inspection areas) and generates multiple frame images (inspection images).

Figure 22 is a diagram showing an example of the relationship between the grid and the frame area in the first embodiment. As described above, each grid 29 is scanned by one beam. As described above, each grid 29 is scanned for each scanning area 31 larger than the grid 29 in order to prevent an error at the joint between the grid 29 scanned by another beam. Since the characteristics of the obtained secondary electron image may vary for each beam, it is desirable to use an image obtained by one beam for the image of one unit inspection area. Therefore, in the first embodiment, the measured stripe pattern data (or chip pattern data) is divided for each frame area 35 that is the unit inspection area to create multiple frame images. Similarly, a reference image is created for each frame area 35. In this case, the frame area 35 is set to a range scanned by one beam. Therefore, the frame area 35 is set to a size equal to or smaller than the grid 29 size. For example, it is preferable to set the size to a natural multiple of the grid 29. In this way, the division unit 56 divides the detected secondary electron image into inspection images equal to or smaller than the size of the scanning area 31.

Next, the alignment unit 58 aligns the frame image (measurement image) and the reference image in sub-pixel units smaller than a pixel 36. For example, the alignment can be performed using the least squares method.

Then, the comparison unit 60 compares the frame image (inspection image) with a reference image corresponding to the frame image (average secondary electron image). For example, the comparison unit 60 compares the frame image with the reference image for each pixel 36. The comparison unit 60 compares the two for each pixel 36 according to a predetermined judgment condition, and judges the presence or absence of a defect such as a shape defect. For example, if the gradation value difference for each pixel 36 is greater than a judgment threshold, it is judged to be a defect. Alternatively, the inspection accuracy may be lowered compared to the shape defect inspection to inspect the presence or absence of a break or short in the pattern. For example, the edge pair of the pattern is detected and the distance between the edge pair is measured. This makes it possible to measure the width dimension of the line pattern and the distance of the space portion between the line patterns. Similarly, if the difference with the distance obtained from the reference image is greater than the judgment threshold, it is judged to be a defect. By measuring between multiple edge pairs in the line direction, the presence or absence of a break and/or short in the pattern can be inspected. Then, the comparison result is output. The comparison results may be output from the storage device 109, the monitor 117, the memory 118, or the printer 119.

As described above, according to the first embodiment, the amplitude of beam deflection can be reduced in pattern inspection performed while continuously moving the XY stage 105 using the multi-beam 20 in which multiple beams are aligned in the moving direction of the XY stage 105. This makes it possible to suppress the effects of aberration in the optical system. Furthermore, the use of the multi-beam 20 can improve the throughput in pattern inspection.

Figure 23 is a configuration diagram showing another configuration of the pattern inspection device in embodiment 1. The electro-optical image acquisition mechanism 150a shown in Figure 1 is equipped with a deflector 208. In contrast, the electro-optical image acquisition mechanism 150b shown in Figure 23 is equipped with a main deflector 208 and a sub-deflector 209. For example, the main deflector 208 performs the first function described above, and the sub-deflector 209 performs the second function described above.

For example, an inspection apparatus having the configuration of FIG. 23 includes a movable stage on which a substrate is placed, a stage control circuit for continuously moving the stage in a direction opposite to a first direction, and a multi-beam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on the substrate surface in the first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction, and an inspection area of the substrate is divided into a plurality of small areas having a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction, and the inspection area is divided into a plurality of small areas having a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction, the inspection area being divided into a plurality of small areas having a size obtained by p/M (M is an integer of 2 or more) in the first direction and a pitch p in the first direction. The multi-beams are deflected collectively to a group of N×N' small regions on the substrate, N of which are arranged at a pitch p and N' of which are arranged in the second direction, and while the stage is continuously moving a distance obtained by N/M·p in the direction opposite to the first direction, the multi-beams are deflected in a tracking manner so as to follow the continuous movement of the stage, and by the time the movement of the stage in the direction opposite to the first direction is completed by the distance obtained by N/M·p, the multi-beams are deflected collectively to a new group of N×N' small regions arranged at a pitch p in the first direction, N away from the group of N×N' small regions, to perform tracking resetting. a first deflector (main deflector 208) that performs tracking deflection of the multi-beams so as to follow the continuous movement of the stage, and a first step of repeatedly deflecting the multi-beams collectively along a second direction from an end portion on the side opposite to the first direction in each of the plurality of small regions as a starting point and an end portion on the side in the first direction in each of the plurality of small regions as an end point, in a direction opposite to the first direction, toward an end portion on the side in the first direction, and then a first step of repeatedly deflecting the multi-beams collectively along a second direction in each of the plurality of small regions as a starting point and an end portion on the side in the first direction in each of the plurality of small regions as an end point, and then a first step of repeatedly deflecting the multi-beams collectively along a second direction from an end portion on the side opposite to the first direction in each of the plurality of small regions as an end point, and a second step of repeatedly deflecting the multi-beams collectively in the direction opposite to the first direction, a third step of repeatedly deflecting the multi-beams collectively in the first direction, and a fourth step of repeatedly deflecting the multi-beams collectively in the direction opposite to the second direction from the end portion on the opposite side of the first direction to the end portion on the first direction in the first direction, with an end portion on the opposite side of the first direction in each of the plurality of small regions as a starting point and an end portion on the first direction in each of the plurality of small regions as an ending point,
This inspection device is characterized by comprising a second deflector (sub-deflector 209) that deflects the multi-beam collectively so as to scan a group of N x N' small areas, and a detector that detects secondary electrons emitted from the substrate as a result of irradiating the substrate with the multi-beam, and by using a combination of values for N and M such that the greatest common divisor between the values of N and M is 1.

In the above description, the series of "circuits" includes processing circuits, which may include electric circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices. Each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. The program that executes the processor may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, a FD, or a ROM (read-only memory). The series of "storage devices" in this embodiment may be, for example, a magnetic disk device, a magnetic tape device, a FD, or a ROM, a flash memory, or the like.

The above describes the embodiment with reference to specific examples. However, the present invention is not limited to these specific examples. In the above example, the XY stage 105 is moved continuously at a constant speed, but the present invention is not limited to this. Although continuous movement at a constant speed is preferable for ease of control, continuous movement accompanied by acceleration and deceleration is also acceptable. Furthermore, regarding the magnitude relationship between the number of beams N and the number of divisions M in the direction of continuous movement of the XY stage 105 during scanning (the -x direction in the embodiment), it does not matter which is larger as long as the least common denominator between the two values is 1.

The order of irradiation of the beams when scanning the grid 29 (scanning area 31) may be arbitrary. However, since the entire multi-beam 20 is deflected collectively by the deflector 208, the irradiation order is the same between each grid 29.

In addition, in the above example, the beams are arranged in an orthogonal lattice, but this is not limiting. For example, a diagonal lattice may be used. Alternatively, the beam rows arranged in the x direction may be arranged slightly offset in the x direction in each row adjacent in the y direction. For example, the heads of the beam rows arranged in the x direction may be arranged in an uneven manner.

The shape of the grid 29 (sub-region; small region) described above is not limited to a rectangle. As long as it is arranged at a pitch of p/M in the x direction and at an equal pitch in the y direction, it may be of any other shape. The shape of the grid 29 (sub-region; small region) may be, for example, a parallelogram. In such a case, the scanning area 31 may also be set to a parallelogram to match the shape of the grid 29. In the case of a parallelogram: Since the circuit pattern has many horizontal and/or orthogonal lines in the x direction, scanning the beam diagonally makes it easier to avoid scanning parallel to the circuit pattern, and the effects of charging can be avoided.

The arrangement pitch of the multi-beams 20 may be different in the x and y directions. For example, they may be arranged at equal pitch p in the x direction and at equal pitch p' in the y direction.

In addition, although descriptions of device configurations, control methods, and other aspects that are not directly necessary for explaining the present invention have been omitted, the required device configurations and control methods can be appropriately selected and used.

All other electron beam inspection devices and electron beam inspection methods that incorporate the elements of the present invention and that can be modified as appropriate by a person skilled in the art are included within the scope of the present invention.

20 multi-beam 22 hole 27 area (p×p area)
28, 36 Pixel 29 Grid 30, 330 Inspection area 31 Scanning area 32 Stripe area 33 Tracking area 34 Irradiation area 35 Frame area 50, 52 Memory device 56 Dividing section 58 Alignment section 60 Comparison section 100 Inspection device 101 Substrate 102 Electron beam column 103 Inspection chamber 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Memory device 110 Control computer 111 Expansion circuit 112 Reference circuit 114 Stage control circuit 117 Monitor 118 Memory 119 Printer 122 Laser length measurement system 120 Bus 123 Stripe pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 132 Image memory device 140 Settling time memory device 141 Scan frequency memory device 144 Average image acquisition circuit 146 Movement speed calculation circuit 148 Scan time calculation circuit 149 Scan time memory device 150a Electron optical image acquisition mechanism 150b Electron optical image acquisition mechanism 160 Control system circuit 200 Electron beam 201 Electron gun 202 Electromagnetic lens 203 Shaping aperture array substrate 205 Electromagnetic lens (reduction lens)
206 Electromagnetic lens 207 Electromagnetic lens (objective lens)
208 Deflector (main deflector)
209: Sub-deflector 212: Collective blanking deflector 214: Beam separator 216: Mirror 222: Multi-detector 224, 226: Projection lens 228: Deflector 300: Multi-secondary electron 332: Chip

Claims (20)

a movable stage on which a substrate is placed;
a stage control circuit for continuously moving the stage in a direction opposite to a first direction;
A multibeam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on the substrate surface in the first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction is used, and the multibeams are collectively directed to a group of N×N' small regions on the substrate arranged in the first direction at the pitch p and N' small regions on the substrate arranged in the second direction, among a plurality of small regions obtained by dividing an inspection region of the substrate into a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction. a first function of deflecting the multi-beams so as to follow the continuous movement of the stage while the stage is continuously moving a distance obtained by N/M·p in the direction opposite to the first direction, and performing a tracking reset by collectively re-deflecting the multi-beams to a new group of N×N′ small regions arranged at the pitch p in the first direction, N away from the group of N×N′ small regions, by the time the movement of the stage in the direction opposite to the first direction is completed by the distance obtained by N/M·p;
While the multiple beams are being deflected in a tracking manner so as to follow the continuous movement of the stage, each of the multiple beams is deflected in each of the plurality of small regions,
a first step of repeatedly deflecting the multi-beams collectively along the second direction from an end portion of each of the plurality of small regions on the side opposite to the first direction to an end portion of each of the plurality of small regions on the side in the first direction as a starting point and an end portion of each of the plurality of small regions on the side in the first direction, from the end portion on the side opposite to the first direction to the end portion on the side in the first direction; and
a second step of repeatedly deflecting the multi-beams collectively in a direction opposite to the second direction from an end of each of the plurality of small regions on the side opposite to the first direction to an end of each of the plurality of small regions on the side opposite to the first direction, the second step being performed from the end of the multi-beams on the side opposite to the first direction to the end of the multi-beams on the side opposite to the first direction;
a deflector having a second function of collectively deflecting the multi-beam so as to scan the N×N′ small area group;
a detector for detecting secondary electrons emitted from the substrate as a result of irradiating the substrate with the multi-beam;
Equipped with
A charged particle beam inspection device, comprising: a combination of values such that the greatest common divisor between the value of N and the value of M is 1, as the value of N and the value of M. When a measurement pixel size that can be irradiated with the charged particle beam is PS, and a beam scan time in the second direction or the opposite direction to the second direction, including a second beam settling time Ofs_v in the second direction or the opposite direction to the second direction, is Tv,
The moving speed V of the stage is V=PS N /(2Tv).
2. The charged particle beam inspection device according to claim 1, wherein: When the size of a measurement pixel that can be irradiated with the charged particle beam is P and the scanning frequency of the charged particle beam is f,
The beam scan time Tv in the second direction or the direction opposite to the second direction is Tv=(p/PS)×(p/M/PS)×(1/f)+(p/M/PS)×Ofs_v
2. The charged particle beam inspection device according to claim 1, wherein: The charged particle beam inspection device according to claim 1, further comprising an average image acquisition circuit that acquires an average secondary electron image by averaging the first secondary electron image acquired in the first step and the second secondary electron image acquired in the second step. a movable stage on which a substrate is placed;
a stage control circuit for continuously moving the stage in a direction opposite to a first direction;
A multibeam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on the substrate surface in the first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction is used, and the multibeams are collectively directed to a group of N×N' small regions on the substrate arranged in the first direction at the pitch p and N' small regions on the substrate arranged in the second direction, among a plurality of small regions obtained by dividing an inspection region of the substrate into a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction. a first function of deflecting the multi-beams so as to follow the continuous movement of the stage while the stage is continuously moving a distance obtained by N/M·p in the direction opposite to the first direction, and performing a tracking reset by collectively re-deflecting the multi-beams to a new group of N×N′ small regions arranged at the pitch p in the first direction, N away from the group of N×N′ small regions, by the time the movement of the stage in the direction opposite to the first direction is completed by the distance obtained by N/M·p;
While the multiple beams are being deflected in a tracking manner so as to follow the continuous movement of the stage, each of the multiple beams is deflected in each of the plurality of small regions,
a first step of repeatedly deflecting the multi-beams collectively along the second direction from an end portion of each of the plurality of small regions on the side opposite to the first direction to an end portion of each of the plurality of small regions on the side in the first direction as a starting point and an end portion of each of the plurality of small regions on the side in the first direction, from the end portion on the side opposite to the first direction to the end portion on the side in the first direction; and
a second step of repeatedly deflecting the multiple beams collectively in a direction opposite to the first direction, and then
a third step of repeatedly deflecting the multiple beams collectively along the first direction, and then
a fourth step of repeatedly deflecting the multi-beams collectively in a direction opposite to the second direction from an end of each of the plurality of small regions on the side opposite to the first direction to an end of each of the plurality of small regions on the side opposite to the first direction, the fourth step being performed with the end of each of the plurality of small regions on the side opposite to the first direction as a starting point and the end of each of the plurality of small regions on the side opposite to the first direction as an ending point,
a deflector having a second function of collectively deflecting the multi-beam so as to scan the N×N′ small area group;
a detector for detecting secondary electrons emitted from the substrate as a result of irradiating the substrate with the multi-beam;
Equipped with
A charged particle beam inspection device, comprising: a combination of values such that the greatest common divisor between the value of N and the value of M is 1, as the value of N and the value of M. The charged particle beam inspection device according to claim 5, wherein the collective deflection of the multi-beam in the second step is repeated from the side opposite to the second direction toward the second direction. The charged particle beam inspection device according to claim 5, wherein the collective deflection of the multi-beam in the second step is repeated from the side in the second direction to the side in the opposite direction to the second direction. The size of a measurement pixel that can be irradiated with the charged particle beam is PS,
A beam scan time in the first direction or the opposite direction to the first direction, including a first beam settling time Ofs_h in the first direction or the opposite direction to the first direction, is Th;
When a beam scan time in the second direction or the opposite direction to the second direction, including a second beam settling time Ofs_v in the second direction or the opposite direction to the second direction, is Tv,
The moving speed V of the stage is V=PS N /(2×(M×Th+Tv)).
6. The charged particle beam inspection device according to claim 5, wherein When the size of a measurement pixel that can be irradiated with the charged particle beam is P and the scanning frequency of the charged particle beam is f,
The beam scan time Th in the first direction or the direction opposite to the first direction is expressed as follows: Th=(p/PS)×(p/M/PS)×(1/f)+(p/PS)×Ofs_h
and
The beam scan time Tv in the second direction or the direction opposite to the second direction is Tv=(p/PS)×(p/M/PS)×(1/f)+(p/M/PS)×Ofs_v
6. The charged particle beam inspection device according to claim 5, wherein The charged particle beam inspection device according to claim 5, further comprising an average image acquisition circuit that acquires an average secondary electron image obtained by averaging the first secondary electron image acquired in the first step, the second secondary electron image acquired in the second step, the third secondary electron image acquired in the third step, and the fourth secondary electron image acquired in the fourth step. a multibeam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on a substrate surface in a first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction, the multibeams being deflected collectively onto a group of N×N' small regions on the substrate, N of which are arranged at the pitch p in the first direction and N' of which are arranged in the second direction, among a plurality of small regions obtained by dividing an inspection region of the substrate into a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction, while performing tracking deflection of the multibeams so as to follow the continuous movement of the stage while the stage on which the substrate is placed is continuously moved a distance obtained by N/M·p in a direction opposite to the first direction;
Each of the multiple beams is focused on each of the plurality of small regions.
a first step of repeatedly deflecting the multi-beams collectively along the second direction from an end portion of each of the plurality of small regions on the side opposite to the first direction to an end portion of each of the plurality of small regions on the side in the first direction as a starting point and an end portion of each of the plurality of small regions on the side in the first direction, from the end portion on the side opposite to the first direction to the end portion on the side in the first direction; and
a second step of repeatedly deflecting the multi-beams collectively in a direction opposite to the second direction from an end of each of the plurality of small regions on the side opposite to the first direction to an end of each of the plurality of small regions on the side opposite to the first direction, the second step being performed from the end of the multi-beams on the side opposite to the first direction to the end of the multi-beams on the side opposite to the first direction;
Detecting secondary electrons emitted from the substrate due to irradiation of the substrate with the multi-beam;
a charged particle beam inspection method for performing tracking reset by collectively deflecting the multi-beam to a new group of N×N′ small regions arranged at the pitch p in the first direction, the new group of N×N′ small regions being N away from the group of N×N′ small regions in the first direction, by the time the movement of the stage is completed by a distance obtained by N/M·p in a direction opposite to the first direction, the method comprising:
A charged particle beam inspection method using a combination of values such that the greatest common divisor between the value of N and the value of M is 1 as the value of N and the value of M. When a measurement pixel size that can be irradiated with the charged particle beam is PS, and a beam scan time in the second direction or the opposite direction to the second direction, including a second beam settling time Ofs_v in the second direction or the opposite direction to the second direction, is Tv,
The moving speed V of the stage is V=PS N /(2Tv).
12. The charged particle beam inspection method according to claim 11, wherein: When the size of a measurement pixel that can be irradiated with the charged particle beam is P and the scanning frequency of the charged particle beam is f,
The beam scan time Tv in the second direction or the direction opposite to the second direction is Tv=(p/PS)×(p/M/PS)×(1/f)+(p/M/PS)×Ofs_v
12. The charged particle beam inspection method according to claim 11, wherein: The charged particle beam inspection device according to claim 11, which acquires an average secondary electron image by averaging the first secondary electron image acquired in the first step and the second secondary electron image acquired in the second step. a multibeam consisting of a plurality of charged particle beams arranged in N rows (N is an integer of 2 or more) at the same pitch p on a substrate surface in a first direction and in N' rows (N' is an integer of 1 or more) in a second direction perpendicular to the first direction, the multibeams being deflected collectively onto a group of N×N' small regions on the substrate, N of which are arranged at the pitch p in the first direction and N' of which are arranged in the second direction, among a plurality of small regions obtained by dividing an inspection region of the substrate into a size obtained by p/M (M is an integer of 2 or more) in the first direction and a predetermined size in the second direction, while performing tracking deflection of the multibeams so as to follow the continuous movement of the stage while the stage on which the substrate is placed is continuously moved a distance obtained by N/M·p in a direction opposite to the first direction;
Each of the multiple beams is focused on each of the plurality of small regions.
a first step of repeatedly deflecting the multi-beams collectively along the second direction from an end portion of each of the plurality of small regions on the side opposite to the first direction to an end portion of each of the plurality of small regions on the side in the first direction as a starting point and an end portion of each of the plurality of small regions on the side in the first direction, from the end portion on the side opposite to the first direction to the end portion on the side in the first direction; and
a second step of repeatedly deflecting the multiple beams collectively in a direction opposite to the first direction, and then
a third step of repeatedly deflecting the multiple beams collectively in a direction opposite to the first direction, and then
a fourth step of repeatedly deflecting the multi-beams collectively in a direction opposite to the second direction from an end of each of the plurality of small regions on the side opposite to the first direction to an end of each of the plurality of small regions on the side opposite to the first direction, the fourth step being performed with the end of each of the plurality of small regions on the side opposite to the first direction as a starting point and the end of each of the plurality of small regions on the side opposite to the first direction as an ending point,
Detecting secondary electrons emitted from the substrate due to irradiation of the substrate with the multi-beam;
a charged particle beam inspection method for performing tracking reset by collectively deflecting the multi-beam to a new group of N×N′ small regions arranged at the pitch p in the first direction, the new group of N×N′ small regions being N away from the group of N×N′ small regions in the first direction, by the time the movement of the stage is completed by a distance obtained by N/M·p in a direction opposite to the first direction, the method comprising:
A charged particle beam inspection method using a combination of values such that the greatest common divisor between the value of N and the value of M is 1 as the value of N and the value of M. The charged particle beam inspection method according to claim 15, wherein the collective deflection of the multi-beam in the second step is repeated from the side opposite to the second direction toward the second direction. The charged particle beam inspection method according to claim 15, wherein the collective deflection of the multi-beam in the second step is repeated from the side in the second direction to the side in the opposite direction to the second direction. The size of a measurement pixel that can be irradiated with the charged particle beam is PS,
A beam scan time in the first direction or the opposite direction to the first direction, including a first beam settling time Ofs_h in the first direction or the opposite direction to the first direction, is Th;
When a beam scan time in the second direction or the opposite direction to the second direction, including a second beam settling time Ofs_v in the second direction or the opposite direction to the second direction, is Tv,
The moving speed V of the stage is V=PS N /(2×(M×Th+Tv)).
16. The charged particle beam inspection method according to claim 15, wherein: When the size of a measurement pixel that can be irradiated with the charged particle beam is P and the scanning frequency of the charged particle beam is f,
The beam scan time Th in the first direction or the direction opposite to the first direction is expressed as follows: Th=(p/PS)×(p/M/PS)×(1/f)+(p/PS)×Ofs_h
and
The beam scan time Tv in the second direction or the direction opposite to the second direction is Tv=(p/PS)×(p/M/PS)×(1/f)+(p/M/PS)×Ofs_v
16. The charged particle beam inspection method according to claim 15, wherein: The charged particle beam inspection method according to claim 15, further comprising: acquiring an average secondary electron image by averaging a first secondary electron image acquired in the first step, a second secondary electron image acquired in the second step, a third secondary electron image acquired in the third step, and a fourth secondary electron image acquired in the fourth step.