JP2017090147A - Polarization image acquisition device, pattern inspection device and polarization image acquisition method - Google Patents

Abstract

PURPOSE: To provide a device which acquires a polarization image usable to generate an exposure image picture when transfer is performed by an exposure device.CONSTITUTION: A polarization image acquisition device according to one embodiment of the present invention comprises: an objective 171 on which transmission light obtained by transmitting illumination light imaged on the mask substrate through a mask substrate impinges with the same numerical aperture with impinging of transmission light from the mask substrate on a reduction optical system of an exposure device receiving and imaging the transmission light from the mask substrate on a substrate to be exposed; a split type 1/2-wavelength plate 172 which is arranged nearby the pupil position of the objective and directs a P-polarized wave and an S-polarized wave of transmission light having passed through the objective to mutually orthogonal directions; a polarization beam splitter 174 which allows one of the P-polarized wave and S-polarized wave of the transmission light to pass through and restricts the other from passing through; an imaging lens 176 which images the light having passed through the polarization beam splitter 174 with a numerical aperture much smaller than that of the reduction optical system of the exposure device; and a photodiode array 105 which picks up the image formed by the imaging lens.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarization image acquisition device, a pattern inspection device, and a polarization image acquisition method. For example, the present invention relates to an apparatus and method for acquiring a polarization image that can be used to generate an exposure image of an exposure mask substrate used in semiconductor manufacturing, and an apparatus and method for inspecting pattern defects on the exposure mask substrate.

  In recent years, the circuit line width required for a semiconductor element has been increasingly narrowed as a large scale integrated circuit (LSI) is highly integrated and has a large capacity. These semiconductor elements use an original pattern pattern (also referred to as a mask or a reticle, hereinafter referred to as a mask) on which a circuit pattern is formed, and the pattern is exposed and transferred onto a wafer by a reduction projection exposure apparatus called a stepper. It is manufactured by forming a circuit. Therefore, a pattern drawing apparatus using an electron beam capable of drawing a fine circuit pattern is used for manufacturing a mask for transferring such a fine circuit pattern onto a wafer. A pattern circuit may be directly drawn on a wafer using such a pattern drawing apparatus. Alternatively, development of a laser beam drawing apparatus for drawing using a laser beam in addition to an electron beam has been attempted.

  In addition, improvement in yield is indispensable for manufacturing an LSI that requires a large amount of manufacturing cost. However, as represented by a 1 gigabit class DRAM (Random Access Memory), the pattern constituting the LSI is on the order of submicron to nanometer. One of the major factors that reduce the yield is a pattern defect of a mask used when an ultrafine pattern is exposed and transferred onto a semiconductor wafer by a photolithography technique. 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. Therefore, it is necessary to improve the accuracy of a pattern inspection apparatus that inspects defects in a transfer mask used in LSI manufacturing.

  As an inspection method, an optical image obtained by imaging a pattern formed on a sample such as a lithography mask using a magnifying optical system at a predetermined magnification is compared with an optical image obtained by imaging design data or the same pattern on the sample. A method of performing an inspection by doing this is known. For example, as a pattern inspection method, “die to die inspection” in which optical image data obtained by imaging the same pattern at different locations on the same mask is compared, or a pattern is formed using CAD data with a pattern design as a mask. The drawing data (design pattern data) converted into the device input format for input by the drawing device when drawing is input to the inspection device, and a design image (reference image) is generated based on this data and the pattern is captured. There is a “die to database (die-database) inspection” that compares an optical image as measured data. In the inspection method in such an inspection apparatus, the sample is placed on the stage, and the stage is moved so that the light beam scans on the sample and the inspection is performed. The sample is irradiated with a light beam by a light source and an illumination optical system. The light transmitted or reflected by the sample is imaged on the sensor via the optical system. The image picked up by the sensor is sent to the comparison circuit as measurement data. The comparison circuit compares the measured data and the reference data according to an appropriate algorithm after the images are aligned, and determines that there is a pattern defect if they do not match.

  In a semiconductor product with a short product cycle, it is an important item to shorten the manufacturing time. When a defective mask pattern is exposed and transferred onto a wafer, a semiconductor device made from the wafer becomes a defective product. Therefore, it is important to perform a mask pattern defect inspection. Then, the defect found by the defect inspection is corrected by the defect correcting device. However, correcting all the found defects increases the time required for manufacturing and leads to a decrease in product value. With the development of the inspection apparatus, the inspection apparatus determines that there is a pattern defect even if a very small deviation occurs. However, when a mask pattern is transferred onto a wafer with an actual exposure apparatus, the circuit can be used as an integrated circuit as long as the circuit is not disconnected or / and short-circuited due to such a defect. Therefore, it is desired to obtain an exposure image exposed on the wafer by the exposure apparatus. However, while the exposure apparatus reduces the mask pattern and forms an image on the wafer, the inspection apparatus enlarges the mask pattern and forms an image on the sensor. Therefore, the configuration of the optical system on the secondary side with respect to the mask substrate is originally different. Therefore, no matter how much the illumination light is in alignment with the exposure apparatus, it is difficult to reproduce the pattern image transferred by the exposure apparatus with the inspection apparatus.

  Here, a dedicated machine for inspecting an exposure image exposed and transferred by an exposure apparatus using an aerial image is disclosed (see, for example, Patent Document 1).

JP 2001-235853 A

  Accordingly, one aspect of the present invention provides an apparatus and method for obtaining a polarization image that can be used to create an exposure image when transferred by an exposure apparatus. Moreover, the inspection apparatus using such a polarization image is provided.

A polarized image acquisition apparatus according to an aspect of the present invention includes:
A movable stage on which a mask substrate for exposure on which a pattern is formed is placed;
The same numerical aperture as when the reduction optical system of the exposure apparatus that enters the light to be transmitted from the mask substrate and forms an image on the substrate to be exposed when the mask substrate is disposed in the exposure apparatus enters the transmitted light from the mask substrate. Then, an objective lens that makes the illumination light illuminated on the mask substrate enter the transmitted light that has passed through the mask substrate, and
It is disposed on the opposite side of the objective lens from the mask substrate and in the vicinity of the pupil position of the objective lens, and the P-polarized wave and S-polarized wave of the transmitted light after passing through the objective lens are aligned in directions orthogonal to each other. A split-type half-wave plate;
A limiting mechanism configured by one of a polarizer and a polarizing beam splitter that passes one of the P-polarized wave and the S-polarized wave of the transmitted light and restricts the other;
A drive mechanism that rotates the limiting mechanism so that the limiting mechanism passes the other described above and restricts the one passing described above;
An imaging lens for imaging light having passed through the limiting mechanism with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
An image sensor that captures an image formed by the imaging lens;
It is characterized by having.

Another aspect of the present invention is a polarization image acquisition device.
A movable stage on which a mask substrate for exposure on which a pattern is formed is placed;
The same numerical aperture as when the reduction optical system of the exposure apparatus that enters the light to be transmitted from the mask substrate and forms an image on the substrate to be exposed when the mask substrate is disposed in the exposure apparatus enters the transmitted light from the mask substrate. And an objective lens on which the illumination light imaged on the mask substrate enters the transmitted light transmitted through the mask substrate;
It is disposed on the opposite side of the objective lens from the mask substrate and in the vicinity of the pupil position of the objective lens, and the P-polarized wave and S-polarized wave of the transmitted light after passing through the objective lens are aligned in directions orthogonal to each other. A split-type half-wave plate;
A limiting mechanism configured by one of a polarizer and a polarizing beam splitter that passes one of the P-polarized wave and the S-polarized wave of the transmitted light and restricts the other;
A half-wave plate that rotates the polarization direction by 90 ° so that the limiting mechanism passes the other and limits the passing of the one;
A drive mechanism for rotating a half-wave plate for rotation;
An imaging lens for imaging light having passed through the limiting mechanism with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
An image sensor that captures an image formed by the imaging lens;
It is characterized by having.

Another aspect of the present invention is a polarization image acquisition device.
A movable stage on which a mask substrate for exposure on which a pattern is formed is placed;
The same numerical aperture as when the reduction optical system of the exposure apparatus that enters the light to be transmitted from the mask substrate and forms an image on the substrate to be exposed when the mask substrate is disposed in the exposure apparatus enters the transmitted light from the mask substrate. Then, an objective lens that makes the illumination light illuminated on the mask substrate enter the transmitted light that has passed through the mask substrate, and
It is disposed on the opposite side of the objective lens from the mask substrate and in the vicinity of the pupil position of the objective lens, and the P-polarized wave and S-polarized wave of the transmitted light after passing through the objective lens are aligned in directions orthogonal to each other. A split-type half-wave plate;
A polarizing beam splitter that transmits one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other;
A first imaging lens for imaging light having passed through the polarization beam splitter with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A first image sensor that captures an image formed by the first imaging lens;
A second imaging lens for imaging the light reflected by the polarization beam splitter with the above-mentioned numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A second image sensor that captures an image formed by the second imaging lens;
It is characterized by having.

The pattern inspection apparatus according to one aspect of the present invention includes:
The polarization image acquisition device described above;
A combining unit that combines the first optical image by one of the P-polarized wave and the S-polarized wave and the second optical image by the other of the P-polarized wave and the S-polarized wave;
A first die image obtained by combining the first and second optical images in the first die, and a first and second optical image in the second die on which a pattern similar to the first die is formed A comparison unit for comparing the synthesized second die image corresponding to the first die image;
It is characterized by having.

The polarized image acquisition method of one embodiment of the present invention includes:
Illuminating illumination light on a mask substrate for exposure on which a pattern is formed; and
The same numerical aperture as when the reduction optical system of the exposure apparatus that enters the light to be transmitted from the mask substrate and forms an image on the substrate to be exposed when the mask substrate is disposed in the exposure apparatus enters the transmitted light from the mask substrate. In the process, the illumination light is transmitted through the mask substrate and incident on the objective lens, and
P-polarized wave of transmitted light after passing through the objective lens using a split-type half-wave plate located on the opposite side of the objective lens from the mask substrate and in the vicinity of the pupil position of the objective lens Aligning S-polarized waves in directions orthogonal to each other;
Passing one of the P-polarized wave and the S-polarized wave of the transmitted light and restricting the other, and
Imaging one of the passed P-polarized wave and S-polarized wave on the image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the image sensor described above to capture a first image formed by one of the P-polarized wave and S-polarized wave that have been imaged;
Outputting an optical image of the first image;
Passing the other of the P-polarized wave and the S-polarized wave of the transmitted light, and restricting one of the above-described passes;
Forming the other of the P-polarized wave and the S-polarized wave that have passed through the above-described image sensor with the above-described numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the image sensor described above to capture a second image formed by the other of the formed P-polarized wave and S-polarized wave;
Outputting an optical image of the second image;
It is characterized by having.

In another aspect of the present invention, a polarization image acquisition method includes:
The polarized image acquisition method of one embodiment of the present invention includes:
Illuminating illumination light on a mask substrate for exposure on which a pattern is formed; and
The same numerical aperture as when the reduction optical system of the exposure apparatus that enters the light to be transmitted from the mask substrate and forms an image on the substrate to be exposed when the mask substrate is disposed in the exposure apparatus enters the transmitted light from the mask substrate. In the process, the illumination light is transmitted through the mask substrate and incident on the objective lens, and
P-polarized wave of transmitted light after passing through the objective lens using a split-type half-wave plate located on the opposite side of the objective lens from the mask substrate and in the vicinity of the pupil position of the objective lens Aligning S-polarized waves in directions orthogonal to each other;
Passing one of the P-polarized wave and S-polarized wave of the transmitted light and reflecting the other;
Forming one of the P-polarized wave and the S-polarized wave, which have been passed, on the first image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the first image sensor to capture a first image formed by one of the P-polarized wave and S-polarized wave formed as described above;
Outputting an optical image of the first image;
Imaging the other of the reflected P-polarized wave and S-polarized wave of the transmitted light on the second image sensor with the above-described numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the second image sensor to capture a second image formed by the other of the P-polarized wave and the S-polarized wave formed as described above;
Outputting an optical image of the second image;
It is characterized by having.

  According to one aspect of the present invention, it is possible to acquire a polarization image that is a basis for creating an exposure image when transferred by an exposure apparatus.

1 is a configuration diagram illustrating a configuration of a pattern inspection apparatus according to a first embodiment. 6 is a conceptual diagram for comparing the numerical aperture in the inspection apparatus and the numerical aperture in the exposure apparatus in the first embodiment. FIG. 6 is a diagram for describing the characteristics of an S-polarized wave and a P-polarized wave in a comparative example of Embodiment 1. FIG. It is a figure for comparing the relationship between the image side numerical aperture, S polarization wave, and P polarization wave in Embodiment 1 and a comparative example. FIG. 6 is a diagram for explaining a technique for separately obtaining a P-polarized component image and an S-polarized component image in the first embodiment. 3 is a diagram illustrating an example of a configuration of a split-type half-wave plate and a state of a polarization component in Embodiment 1. FIG. FIG. 6 is a diagram for explaining an arrangement position of a divided half-wave plate in the first embodiment. FIG. 3 is a conceptual diagram for explaining an inspection region in the first embodiment. 3 is a diagram illustrating an internal configuration of a comparison circuit in the first embodiment. FIG. 6 is a diagram illustrating a part of the configuration of an optical image acquisition unit of an inspection apparatus according to Embodiment 2. FIG. FIG. 10 is a diagram illustrating a part of the configuration of an optical image acquisition unit of an inspection apparatus according to Embodiment 3.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing the configuration of the pattern inspection apparatus according to the first embodiment. In FIG. 1, an inspection apparatus 100 for inspecting a defect of a pattern formed on a mask substrate 101 includes an optical image acquisition unit 150 and a control system circuit 160 (control unit).

  The optical image acquisition unit 150 (polarization image acquisition device) includes a light source 103, a transmission illumination optical system 170, a movable XYθ table 102, a magnifying optical system 104, a split-type half-wave plate 172, and a polarization beam splitter 174. Two photodiode arrays 105 and 205 (an example of a sensor), two sensor circuits 106 and 206, two stripe pattern memories 123 and 223, and a laser length measurement system 122 are included. A mask substrate 101 is placed on the XYθ table 102. Examples of the mask substrate 101 include an exposure photomask that transfers a pattern onto a semiconductor substrate such as a wafer. The photomask is formed with a pattern constituted by a plurality of graphic patterns to be inspected. Here, a case where the same two patterns are formed on the left and right is shown. For example, the mask substrate 101 is arranged on the XYθ table 102 with the pattern formation surface facing downward.

  The transmission illumination optical system 170 includes a projection lens 180, an illumination shape switching mechanism 181, and an imaging lens 182. Further, the transmission illumination optical system 170 may have other lenses, mirrors, and / or optical elements.

  The magnifying optical system 104 includes an objective lens 171 and two imaging lenses 176 and 178. Further, the magnifying optical system 104 may include other lenses and / or mirrors between the objective lens 171 and the imaging lens 176 and / or between the objective lens 171 and the imaging lens 178. .

  In the control system circuit 160, a control computer 110 serving as a computer is connected via a bus 120 to a position circuit 107, a comparison circuit 108, an autoloader control circuit 113, a table control circuit 114, a magnetic disk device 109, a magnetic tape device 115, and a flexible disk. A device (FD) 116, a CRT 117, a pattern monitor 118, and a printer 119 are connected. The sensor circuit 106 is connected to the stripe pattern memory 123, and the stripe pattern memory 123 is connected to the comparison circuit 108. Similarly, the sensor circuit 206 is connected to the stripe pattern memory 223, and the stripe pattern memory 223 is connected to the comparison circuit 108. The XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor.

  In the inspection apparatus 100, the light source 103, the XYθ table 102, the transmission illumination optical system 170, the magnifying optical system 104, the photodiode arrays 105 and 206, and the sensor circuits 106 and 206 constitute a high-magnification inspection optical system. For example, an inspection optical system having a magnification of 400 to 500 times is configured. The XYθ table 102 is driven by the table control circuit 114 under the control of the control computer 110. It can be moved by a drive system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions. As these X motor, Y motor, and θ motor, for example, linear motors can be used. The XYθ table 102 can be moved in the horizontal direction and the rotation direction by a motor of each axis of XYθ. The focus position (optical axis direction: Z-axis direction) of the objective lens 171 is dynamically adjusted on the pattern forming surface of the mask substrate 101 by an auto focus (AF) control circuit (not shown) under the control of the control computer 110. The For example, the objective lens 171 is moved in the optical axis direction (Z-axis direction) by a piezoelectric element (not shown) to adjust the focal position. The moving position of the mask substrate 101 placed on the XYθ table 102 is measured by the laser length measurement system 122 and supplied to the position circuit 107.

  Design pattern data (drawing data) that is a basis for pattern formation of the mask substrate 101 may be input from the outside of the inspection apparatus 100 and stored in the magnetic disk device 109.

  Here, FIG. 1 shows components necessary for explaining the first embodiment. It goes without saying that the inspection apparatus 100 may normally include other necessary configurations.

  FIG. 2 is a conceptual diagram for comparing the numerical aperture of the inspection apparatus and the numerical aperture of the exposure apparatus in the first embodiment. FIG. 2A shows a part of an optical system of an exposure apparatus such as a stepper that exposes and transfers a pattern formed on a mask substrate to a semiconductor substrate. In the exposure apparatus, illumination light (not shown) is illuminated on the mask substrate 300, transmitted light 301 from the mask substrate 300 is incident on the objective lens 302, and light 305 that has passed through the objective lens 302 is a semiconductor substrate 304 (wafer: exposed). The image is formed on the substrate. 2A shows one objective lens 302 (reduction optical system), it goes without saying that a combination of a plurality of lenses may be used. Here, in the current exposure apparatus, the pattern formed on the mask substrate 300 is reduced to 1/4, for example, and transferred to the semiconductor substrate 304 by exposure. In this case, the numerical aperture NAi (numerical aperture on the image i side) of the exposure apparatus with respect to the semiconductor substrate 304 is set to NAi = 1.4, for example. In other words, the numerical aperture NAi (the numerical aperture on the image i side) of the objective lens 302 that can pass through the objective lens 302 is set to NAi = 1.4, for example. In the exposure apparatus, since the transmitted light image from the mask substrate 300 is reduced to ¼, the sensitivity of the objective lens 302 to the mask substrate 300 becomes ¼. In other words, the numerical aperture NAo (numerical aperture on the object o side) of the objective lens 302 that can be incident when transmitted light enters the objective lens 302 from the mask substrate 300 is ¼ of NAi, and NAo = 0.35. It becomes. Therefore, in the exposure apparatus, the transmitted light image from the mask substrate 300 of a light beam having a numerical aperture NAo = 0.35 is exposed and transferred to the semiconductor substrate 304 as an image of a light beam having a very wide numerical aperture NAi = 1.4. become.

  On the other hand, in the inspection apparatus 100 according to the first embodiment, as shown in part of the inspection apparatus 100 in FIG. 2B, illumination light (not shown) is illuminated on the mask substrate 101 and transmitted from the mask substrate 101. The light 190 enters the magnifying optical system 104 including the objective lens, and the light 192 that has passed through the magnifying optical system 104 forms an image on the photodiode array 105 (image sensor). At that time, the numerical aperture NAo (numerical aperture on the object o side) of the objective lens that can be incident when the transmitted light 190 is incident on the magnifying optical system 104 from the mask substrate 101 is equal to the objective lens 302 of the exposure apparatus. For example, NAo = 0.35 is set. However, in the inspection apparatus 100, since the transmitted light image from the mask substrate 300 is enlarged by 200 to 500 times so that it can be compared by inspection, the sensitivity of the magnifying optical system 104 to the mask substrate 101 is 200 to 500. Become. Therefore, the numerical aperture NAi (numerical aperture on the image i side) of the magnifying optical system 104 with respect to the photodiode array 105 cannot be set to a very wide numerical aperture NAi = 1.4 unlike the objective lens 302 of the exposure apparatus. For example, the numerical aperture NAi = 0.002. Thus, the numerical aperture NAi (numerical aperture on the image i side) of the magnifying optical system 104 with respect to the photodiode array 105 is sufficiently smaller than that of the objective lens 302 (reduction optical system) of the exposure apparatus. In FIG. 2B, only the magnifying optical system 104 is shown, but a plurality of lenses are arranged in the magnifying optical system 104. As described above, the magnifying optical system 104 includes at least the objective lens 171 and the imaging lens 176 (and the imaging lens 178).

  Accordingly, the objective lens 171 is transmitted from the mask substrate 101 by the objective lens 302 of the exposure apparatus that enters the transmitted light from the mask substrate 101 and forms an image on the semiconductor substrate 304 when the mask substrate 101 is disposed in the exposure apparatus. Illumination light imaged on the mask substrate 101 enters the transmitted light 190 transmitted through the mask substrate 101 with the same numerical aperture NAo (NAo = 0.35) as in the case where the light 301 is incident. The imaging lens 176 (and the imaging lens 178) forms an image of the light that has passed through the magnifying optical system 104 with a numerical aperture NAi (NAi = 0.002) that is sufficiently smaller than the objective lens 302 of the exposure apparatus. .

  FIG. 3 is a diagram for explaining the characteristics of the S-polarized wave and the P-polarized wave in the comparative example of the first embodiment. FIG. 3 shows an example of a state in which the light 305 that has passed through the objective lens 302 of the exposure apparatus as a comparative example forms an image on the semiconductor substrate 304. Since the numerical aperture NAi (numerical aperture on the image i side) of the objective lens 302 with respect to the semiconductor substrate 304 becomes a very wide numerical aperture NAi = 1.4, the amplitude of the P-polarized component of the light 305 in particular due to the effect of light interference. Decreases, disappears, or reverses.

  FIG. 4 is a diagram for comparing the relationship between the image-side numerical aperture, the S-polarized wave, and the P-polarized wave in the first embodiment and the comparative example. As described above, in the exposure apparatus, the numerical aperture NAi of the objective lens 302 on the semiconductor substrate 304 side is as large as NAi = 1.4. Therefore, as shown in FIG. 4, the amplitude of the P-polarized component is reduced or eliminated. Or reverse. Further, the amplitude of the S-polarized component remains the same regardless of the numerical aperture NAi of the objective lens 302 on the semiconductor substrate 304 side.

  On the other hand, as described above, in the inspection apparatus 100, the numerical aperture NAi on the photodiode array 105 side of the magnifying optical system 104 is NAi = 0.0008, which is very (sufficiently) smaller than the objective lens 302 of the exposure apparatus. Therefore, there is no reduction in the amplitude of the P-polarized component. Similarly, the same state is maintained for the amplitude of the S polarization component.

  Both the light of the mask pattern image formed on the semiconductor substrate 304 in the exposure apparatus and the light of the mask pattern image formed on the photodiode array 105 in the inspection apparatus 100 are combined light of the P-polarized component and the S-polarized component. If the P polarization components are different, the obtained optical images are not the same image.

  Therefore, in the first embodiment, based on such a phenomenon, in the inspection apparatus 100, the mask pattern image formed on the photodiode array 105 is obtained by separating the image into a P-polarized component image and an S-polarized component image. . Thus, an exposure image can be generated from the two types of images captured by the photodiode array 105 by adjusting the manner (ratio) of combining the P-polarized component and the S-polarized component.

  FIG. 5 is a diagram for explaining a technique for obtaining a P-polarized component image and an S-polarized component image separately in the first embodiment. FIG. 5 shows a part of the configuration of FIG. In FIG. 5, the dotted line indicates the pupil position from each lens. It should be noted that the scales of the positions of the components in FIGS. 1 and 5 are not matched. Laser light (for example, DUV light) having a wavelength in the ultraviolet region or less, which is inspection light, is generated from the light source 103. The generated light is illuminated to the illumination shape switching mechanism 181 by the projection lens 180, and the illumination shape switching mechanism 181 changes the shape of the illumination light (inspection light) to the illumination shape used in the exposure apparatus. The Illumination light having the same illumination shape as that used in the exposure apparatus is imaged on the pattern formation surface of the mask substrate 101 by the imaging lens 182 from the back side opposite to the pattern formation surface of the mask substrate 101. The transmitted light (mask pattern image) transmitted through the mask substrate 101 has the same numerical aperture NAo (NAo = 0.35) as that when the objective lens 302 (reduction optical system) of the exposure apparatus enters the transmitted light from the mask substrate 101. ) And is projected onto the split half-wave plate 172 in parallel by the objective lens 171. Therefore, the optical conditions so far of the inspection apparatus 100 can be the same as those of the exposure apparatus.

  The split-type half-wave plate 172 is disposed on the opposite side of the objective lens 171 from the mask substrate 101 and in the vicinity of the pupil position of the objective lens 171. Then, the split type half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in the directions orthogonal to each other. By aligning the directions, it is possible to arrange the prior environment so that the P-polarized wave can be separated and left. Alternatively, the pre-environment can be arranged so that the S-polarized wave can be left separated from the others.

  FIG. 6 is a diagram showing an example of the configuration of the split-type half-wave plate and the state of the polarization component in the first embodiment. In the example of FIG. 6, an 8-divided half-wave plate is shown as an example of the divided half-wave plate 172. As shown in FIG. 6A, the eight-divided half-wave plate 172 is divided into eight regions, and the direction of the fast axis indicated by the dotted line is different in each region. As shown in FIG. 6A, the S-polarized light component is oriented in the circumferential direction of the transmitted light, and is aligned in the x direction, for example, by passing through an 8-divided half-wave plate. On the other hand, as shown in FIG. 6B, the P-polarized light component is directed in the radial direction of the transmitted light, and is orthogonal to the S-polarized light component by passing through an 8-divided half-wave plate. For example, they are aligned in the y direction. In the example of FIG. 6, an eight-divided type is shown, but the present invention is not limited to this. It may be a 4-split type, a 16-split type, or any other split type. For the transmitted light (mask pattern image), it is sufficient if the P-polarized component and the S-polarized component can be aligned in directions orthogonal to each other.

FIG. 7 is a diagram for explaining the arrangement position of the split-type half-wave plate in the first embodiment. The divided half-wave plate 172 is disposed on the opposite side of the mask substrate 101 with respect to the objective lens 171 and in the vicinity of the pupil position of the objective lens 171. The spread of the light beam at the position of the split-type half-wave plate 172 is desirably 5% or less of the pupil diameter D of the objective lens 171 (the maximum diameter of the axial parallel light flux that has passed through the objective lens 171). Therefore, the shift amount ΔL from the pupil position of the objective lens 171 at the arrangement position of the split type half-wave plate 172 is the pupil diameter D of the objective lens 171, the field diameter d of the objective lens 171, and the focal length f of the objective lens 171. It is preferable that the following expression (1) is satisfied using
(1) ΔL <0.05 · D · f / d

  Therefore, the split type half-wave plate 172 is preferably arranged within the pupil position deviation amount ΔL from the pupil position of the objective lens 171.

  The transmitted light that has passed through the split-type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 passes one of the P-polarized wave and S-polarized wave of the transmitted light and reflects the other. To do. In the example of FIG. 5, the P-polarized wave of the transmitted light is allowed to pass and the S-polarized wave is reflected. The relationship between the transmitted polarization component and the reflected polarization component may be reversed. Since the direction of the same polarized wave is aligned by the split type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174.

  The light (for example, P-polarized wave) that has passed through the polarization beam splitter 174 enters the imaging lens 176, and the imaging lens 176 (first imaging lens) converts the incident light into the objective lens 302 (reduction optics) of the exposure apparatus. The image is formed on the photodiode array 105 with a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the system.

  The photodiode array 105 (first image sensor) captures an image (for example, an image of a P-polarized component) (first image) formed by the imaging lens 176.

  The light reflected from the polarization beam splitter 174 (for example, S-polarized wave) enters the imaging lens 178, and the imaging lens 178 (second imaging lens) converts the incident light into the objective lens 302 (reduction optics) of the exposure apparatus. The image is formed on the photodiode array 205 with a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the system).

  The photodiode array 205 (second image sensor) captures an image (for example, an image of an S-polarized component) (second image) formed by the imaging lens 178.

  For example, a TDI (Time Delay Integration) sensor or the like is preferably used as the photodiode arrays 105 and 205. The photodiode arrays 105 and 205 (image sensors) capture an optical image of the corresponding polarization component of the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is placed is moving. .

  FIG. 8 is a conceptual diagram for explaining the inspection region in the first embodiment. As shown in FIG. 8, the inspection area 10 (entire inspection area) of the mask substrate 101 is virtually divided into a plurality of strip-shaped inspection stripes 20 having a scan width W, for example, in the y direction. Then, the inspection apparatus 100 acquires an image (stripe region image) for each inspection stripe 20. For each of the inspection stripes 20, an image of a graphic pattern arranged in the stripe region is taken in the longitudinal direction (x direction) of the stripe region using laser light. The movement of the XYθ table 102 moves the mask substrate 101 in the x direction, and as a result, an optical image is acquired while the photodiode arrays 105 and 205 move continuously in the −x direction relatively. In the photodiode arrays 105 and 205, an optical image having a scan width W as shown in FIG. In other words, the photodiode arrays 105 and 205 as an example of the sensor capture an optical image of the pattern formed on the mask substrate 101 using the inspection light while moving relative to the XYθ table 102. In the first embodiment, after an optical image in one inspection stripe 20 is captured, the optical image having the scan width W is similarly moved while moving in the y direction to the position of the next inspection stripe 20 and moving in the opposite direction. Take images continuously. That is, imaging is repeated in a forward (FWD) -backforward (BWD) direction in the opposite direction on the forward path and the backward path.

  Here, the imaging direction is not limited to repeating forward (FWD) -backforward (BWD). You may image from one direction. For example, FWD-FWD may be repeated. Alternatively, BWD-BWD may be repeated.

  The P-polarized light pattern image formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105, and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (stripe region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range having a maximum gradation when the amount of illumination light is 60% incident.

  On the other hand, the S-polarized light pattern image formed on the photodiode array 205 is photoelectrically converted by each light receiving element of the photodiode array 205, and further A / D (analog / digital) converted by the sensor circuit 206. . Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 223. When capturing such pixel data (stripe region image), the dynamic range of the photodiode array 205 is preferably, for example, a dynamic range having a maximum gradation when the amount of illumination light is 60% incident.

  Further, when acquiring an optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (calculation unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the P-polarized light stripe region image is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of P-polarized light is, for example, 8-bit unsigned data, and represents the brightness gradation (light quantity) of each pixel. The P-polarized light stripe area image output into the comparison circuit 108 is stored in a storage device to be described later.

  Similarly, the S-polarized light stripe region image is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of S-polarized light is, for example, 8-bit unsigned data, and represents the brightness gradation (light quantity) of each pixel. The S-polarized light stripe region image output in the comparison circuit 108 is stored in a storage device to be described later.

  As described above, according to the first embodiment, it is possible to simultaneously acquire the polarization images of the S-polarized wave and the P-polarized wave that are the basis for creating an exposure image when transferred by the exposure apparatus. Then, the acquired polarization image of the P-polarized wave is matched with the state of the P-polarized component whose amplitude is reduced, eliminated, or reversed by the objective lens 302 (reduction optical system) of the exposure apparatus, and then the S-polarized wave By combining with a polarized image, an exposure image can be created. According to Embodiment 1, since imaging is performed with the S-polarized wave and the P-polarized wave separated, it is possible to adjust one polarization component image.

  The inspection apparatus 100 according to the first embodiment further performs pattern inspection of the mask substrate 101 using the polarization images of the S-polarized wave and the P-polarized wave.

  FIG. 9 is a diagram illustrating an internal configuration of the comparison circuit according to the first embodiment. 9, in the comparison circuit 108, storage devices 50, 52, 58, 60, 66, 68 such as a magnetic disk device, frame dividing units 54, 56, a correcting unit 62, a combining unit 64, an alignment unit 70, And the comparison part 72 is arrange | positioned.

  In the comparison circuit 108, the stripe area image (optical image) of the P-polarized wave of the inspection stripe 20 is stored in the storage device 50. Then, the frame dividing unit 54 reads the P-polarized wave stripe area image, and divides the P-polarized wave stripe area image into a predetermined size (for example, the same width as the scan width W) in the x direction. For example, the image is divided into 512 × 512 pixel frame images. Thereby, for example, with respect to a plurality of frame regions 30 (FIG. 8) obtained by dividing the inspection stripe 20 with the same width as the scan width W, a frame image of the P-polarized wave of each frame region 30 can be acquired. The frame image of the P-polarized wave is stored in the storage device 58.

  Similarly, an S-polarized wave stripe area image (optical image) of the inspection stripe 20 is stored in the storage device 52. Then, the frame division unit 56 reads the S-polarized wave stripe area image, and divides the S-polarized wave stripe area image into a predetermined size (for example, the same width as the scan width W) in the x direction. For example, the image is divided into 512 × 512 pixel frame images. Thereby, the frame image of the S polarized wave in each frame region 30 can be acquired. The frame image of the S polarized wave is stored in the storage device 60.

  Next, the correction unit 62 decreases the gradation value of the P-polarized wave frame image at a predetermined rate so as to match the exposure image. The reduction ratio may be adjusted to the amplitude amount (ratio) of the P-polarized component that is reduced, eliminated, or inverted by the objective lens 302 (reduction optical system) of the exposure apparatus.

  The synthesizing unit 64 synthesizes the frame image (first optical image) based on the corrected P-polarized wave and the frame image (second optical image) based on the uncorrected S-polarized wave. Accordingly, a combined frame image (first die image) is generated by combining the frame image by the P-polarized wave and the frame image by the S-polarized wave in the die (1) (first die) to be inspected. The composite frame image of the die (1) is stored in the storage device 66.

  In the first embodiment, “die to die inspection” is performed in which optical image data obtained by imaging the same pattern at different locations on the same mask are compared. For example, the above-described stripe region image includes images of two dies on which the same pattern is formed. Therefore, a composite frame image (second die image) of the frame region 30 of the die (2) (second die) corresponding to the frame region 30 of the composite frame image of the die (1) is similarly generated. The composite frame image of the die (2) is stored in the storage device 68.

  The alignment unit 70 aligns the composite frame image (optical image) of the die (1) to be compared with the composite frame image (reference image) of the die (2) to be compared using a predetermined algorithm. Do. For example, alignment is performed using a least square method.

  The comparison unit 72 combines the frame image (first optical image) based on the P-polarized wave after correction in the die (1) and the frame image (second optical image) based on the unpolarized S-polarized wave. Frame image (first optical image) by corrected P-polarized wave and uncorrected S-polarized light in image (first die image) and die (2) in which a pattern similar to die (1) is formed The synthesized frame image (second die image) corresponding to the synthesized frame image (first die image) obtained by synthesizing the wave frame image (second optical image) is compared.

  Here, in the composite frame image generated by the first embodiment, the numerical aperture NAo of the objective lens 171 is set according to the same conditions as the exposure apparatus. Therefore, the numerical aperture NAo of the objective lens 171 is smaller than the numerical aperture NAo of the objective lens used in the conventional high-resolution pattern defect inspection apparatus. Therefore, since the light beam incident on the objective lens 171 is small, the resolution of the image is worse than that of the conventional high-resolution pattern defect inspection apparatus. On the other hand, when a mask pattern is transferred onto a wafer with an actual exposure apparatus, such a pattern can be used as an integrated circuit as long as no circuit disconnection or / and short circuit occurs on the wafer due to defects. Since the composite frame image generated by the first embodiment is created in accordance with the exposure image exposed on the wafer by the exposure apparatus, whether or not a circuit disconnection or / and a short-circuit occurs on the wafer is determined. Can be inspected. Therefore, the comparison unit 72 does not inspect individual shape defects of individual graphic patterns, but inspects the distance between adjacent patterns. In such a case, the comparison unit 72 measures the inter-pattern distance of each pattern in the composite frame image (first die image), and similarly, between the patterns of each pattern in the composite frame image (second die image). Measure distance. Then, it is determined whether the difference obtained by subtracting the corresponding inter-pattern distance of the composite frame image (second die image) from the inter-pattern distance of the composite frame image (first die image) is larger than the determination threshold. It is determined as a defect. Then, the comparison result is output. The comparison result may be output from the magnetic disk device 109, the magnetic tape device 115, the flexible disk device (FD) 116, the CRT 117, the pattern monitor 118, or the printer 119.

  As described above, according to the first embodiment, the polarization images of the S-polarized wave and the P-polarized wave are obtained. Therefore, the exposure image is obtained by using the polarization images of the S-polarized wave and the P-polarized wave. Thus, the pattern inspection of the mask substrate 101 can be performed.

Embodiment 2. FIG.
Although the first embodiment has described the configuration in which two sensors are used to simultaneously capture the polarization image of the S-polarized wave and the polarization image of the P-polarized wave, the present invention is not limited to this. In the second embodiment, a configuration will be described in which imaging is performed using one sensor while switching between an S-polarized wave polarization image and a P-polarized wave polarization image.

  FIG. 10 is a diagram illustrating a part of the configuration of the optical image acquisition unit of the inspection apparatus according to the second embodiment. FIG. 10 shows a part necessary for explaining the configuration of the optical image acquisition unit 150 (polarized image acquisition device) in the second embodiment in the configuration of FIG. The optical image acquisition unit 150 according to the second embodiment does not require the photodiode array 205 (an example of a sensor), the sensor circuit 106, and the stripe pattern memory 123 in the configuration of FIG. Instead, a drive mechanism 175 that rotates the incident surface of the polarization beam splitter 174 (limit mechanism) is disposed. Other points of the inspection apparatus according to the second embodiment are the same as those in FIG.

  The configuration and situation until the laser light (for example, DUV light) having a wavelength below the ultraviolet region, which is the inspection light, is generated from the light source 103 and the transmitted light of the mask substrate 101 is transmitted through the divided half-wave plate 172 are implemented. This is the same as the first embodiment. Therefore, the split half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, it is possible to arrange the prior environment so that the P-polarized wave can be separated and left. Alternatively, it is the same as in the first embodiment in that the prior environment can be adjusted so that the S-polarized wave can be left separately.

  The transmitted light that has passed through the split-type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 passes one of the P-polarized wave and S-polarized wave of the transmitted light and reflects the other. To do. In other words, the polarization beam splitter 174 (an example of a limiting mechanism) allows one of the P-polarized wave and the S-polarized wave of the transmitted light to pass and restricts the other. Which polarized light is allowed to pass or is restricted from passing depends on the position of the polarizing beam splitter 174 rotated by the drive mechanism 175. That is, the driving mechanism 175 rotates the beam splitter 174 so that the polarization beam splitter 174 passes one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other. For example, when imaging a polarization image of the P-polarized wave of the transmitted light, the driving mechanism 175 causes the S-polarized wave so that the polarization beam splitter 174 transmits the P-polarized wave of the transmitted light and reflects the S-polarized wave. Rotate the direction of the beam splitter 174 in the state of 90 ° (or −90 °). Conversely, when imaging a polarization image of the S-polarized wave of the transmitted light, the driving mechanism 175 causes the P-polarized light so that the polarization beam splitter 174 transmits the S-polarized wave of the transmitted light and reflects the P-polarized wave. The direction of the beam splitter 174 in the state of the wave is rotated by −90 ° (or 90 °).

  In the example of FIG. 10, the polarization beam splitter 174 is used, but the present invention is not limited to this. Instead of the polarizing beam splitter 174, for example, a polarizer (another example of a limiting mechanism) may be used. Similarly to the polarization beam splitter 174, the polarizer can also pass one of the P-polarized wave and the S-polarized wave and reflect the other with respect to the polarizer by adjusting the orientation of the polarizer by the drive mechanism 175. .

  As described above, since the directions of the same polarized wave are aligned by the split-type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or a polarizer).

  When the direction of the polarization beam splitter 174 is set by the drive mechanism 175 so that the P-polarized wave can pass, the light (P-polarized wave) that has passed through the polarization beam splitter 174 enters the imaging lens 176 and forms an image. The lens 176 (first imaging lens) has a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reduction optical system) of the exposure apparatus. To form an image on the photodiode array 105.

  The photodiode array 105 (image sensor) captures an image (P-polarized component image) (first image) formed by the imaging lens 176.

  Note that, for example, a TDI sensor is preferably used as the photodiode array 105 as in the first embodiment. The photodiode array 105 (image sensor) captures an optical image of the corresponding polarization component of the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is placed is moving. As described above, the optical image may be picked up in units of the inspection stripe 20.

  The P-polarized light pattern image formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105, and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (stripe region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range having a maximum gradation when the amount of illumination light is 60% incident.

  Further, when acquiring an optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (calculation unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the P-polarized light stripe region image is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of P-polarized light is, for example, 8-bit unsigned data, and represents the brightness gradation (light quantity) of each pixel. The P-polarized light stripe area image output in the comparison circuit 108 is stored in the storage device 50.

  Next, the driving mechanism 175 changes the direction of the polarization beam splitter 174 so that the S-polarized wave can pass. Then, the S-polarized wave is imaged on the same inspection stripe 20 on which the P-polarized wave is imaged.

  The configuration and situation until the laser light (for example, DUV light) having a wavelength below the ultraviolet region, which is the inspection light, is generated from the light source 103 and the transmitted light of the mask substrate 101 is transmitted through the divided half-wave plate 172 are implemented. This is the same as the first embodiment. Therefore, the split half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, it is possible to arrange the prior environment so that the P-polarized wave can be separated and left. Alternatively, it is the same as in the first embodiment in that the prior environment can be adjusted so that the S-polarized wave can be left separately.

  The transmitted light that has passed through the split-type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 passes the S-polarized wave of the transmitted light and reflects the P-polarized wave.

  As described above, since the directions of the same polarized wave are aligned by the split-type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or a polarizer).

  Since the direction of the polarization beam splitter 174 is set by the drive mechanism 175 so that the S-polarized wave can pass, the light (S-polarized wave) that has passed through the polarization beam splitter 174 enters the imaging lens 176 and forms an image. The lens 176 (imaging lens) is a photodiode having a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reduction optical system) of the exposure apparatus. An image is formed on the array 105.

  The photodiode array 105 (image sensor) captures an image (image of an S-polarized component) (second image) formed by the imaging lens 176.

  The photodiode array 105 (image sensor) captures an optical image of the corresponding polarization component of the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is placed is moving. As described above, the optical image may be picked up in units of the inspection stripe 20.

  The S-polarized light pattern image formed on the photodiode array 105 is photoelectrically converted by the respective light receiving elements of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (stripe region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range having a maximum gradation when the amount of illumination light is 60% incident.

  Further, when acquiring an optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (calculation unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of S-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of S-polarized light is, for example, 8-bit unsigned data, and represents the brightness gradation (light quantity) of each pixel. The S-polarized light stripe region image output in the comparison circuit 108 is stored in the storage device 52.

  As described above, according to the second embodiment, the polarization images of the S-polarized wave and the P-polarized wave, which are the basis for creating the exposure image when transferred by the exposure apparatus, are acquired at different times. it can. Then, the acquired polarization image of the P-polarized wave is matched with the state of the P-polarized component whose amplitude is reduced, eliminated, or reversed by the objective lens 302 (reduction optical system) of the exposure apparatus, and then the S-polarized wave By combining with a polarized image, an exposure image can be created. According to the second embodiment, since imaging is performed with the S-polarized wave and the P-polarized wave separated, it is possible to adjust one polarization component image.

  The inspection apparatus 100 according to the second embodiment further performs pattern inspection of the mask substrate 101 using the polarization images of the S-polarized wave and the P-polarized wave. The inspection method may be the same as in the first embodiment.

Embodiment 3 FIG.
Although the first embodiment has described the configuration in which two sensors are used to simultaneously capture the polarization image of the S-polarized wave and the polarization image of the P-polarized wave, the present invention is not limited to this. In the second embodiment, a configuration will be described in which imaging is performed using one sensor while switching between an S-polarized wave polarization image and a P-polarized wave polarization image.

  FIG. 11 is a diagram illustrating a part of the configuration of the optical image acquisition unit of the inspection apparatus according to the third embodiment. FIG. 11 shows a part necessary for explaining the configuration of the optical image acquisition unit 150 (polarized image acquisition device) in the second embodiment in the configuration of FIG. The optical image acquisition unit 150 according to the third embodiment does not require the photodiode array 205 (an example of a sensor), the sensor circuit 106, and the stripe pattern memory 123 in the configuration of FIG. Instead, a half-wave plate 177 (a half-wave plate for rotation) and a drive mechanism 175 for rotating the half-wave plate for rotation are provided on the incident side of the polarization beam splitter 174 (a limit mechanism). Be placed. Other points of the inspection apparatus according to the third embodiment are the same as those in FIG.

  The configuration and situation until the laser light (for example, DUV light) having a wavelength below the ultraviolet region, which is the inspection light, is generated from the light source 103 and the transmitted light of the mask substrate 101 is transmitted through the divided half-wave plate 172 are implemented. This is the same as the first embodiment. Therefore, the split half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, it is possible to arrange the prior environment so that the P-polarized wave can be separated and left. Alternatively, it is the same as in the first embodiment in that the prior environment can be adjusted so that the S-polarized wave can be left separately.

  The transmitted light that has passed through the split-type half-wave plate 172 passes through the half-wave plate 177 and then enters the polarization beam splitter 174. The polarization beam splitter 174 transmits the P-polarized wave and the S-polarized wave of the transmitted light. Pass one of them and reflect the other. In other words, the polarization beam splitter 174 (an example of a limiting mechanism) allows one of the P-polarized wave and the S-polarized wave of the transmitted light to pass and restricts the other. Which polarized light is allowed to pass or is restricted from passing depends on the arrangement position of the half-wave plate 177 rotated by the drive mechanism 175. That is, the drive mechanism 175 rotates the half-wave plate 177 so that the polarization beam splitter 174 transmits one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other. For example, when imaging a polarization image of the P-polarized wave of the transmitted light, the driving mechanism 175 causes the S-polarized wave so that the polarization beam splitter 174 transmits the P-polarized wave of the transmitted light and reflects the S-polarized wave. The direction of the half-wave plate 177 that is in the direction of is rotated by 45 ° (or −45 °). Conversely, when imaging a polarization image of the S-polarized wave of the transmitted light, the driving mechanism 175 causes the P-polarized light so that the polarization beam splitter 174 transmits the S-polarized wave of the transmitted light and reflects the P-polarized wave. The direction of the half-wave plate 177 in the state of the wave is rotated by −45 ° (or 45 °).

  In the example of FIG. 11, the polarization beam splitter 174 is used, but the present invention is not limited to this. Instead of the polarizing beam splitter 174, for example, a polarizer (another example of a limiting mechanism) may be used. Also for the polarizer, like the polarization beam splitter 174, the direction of the half-wave plate is adjusted by the drive mechanism 175 so that one of the P-polarized wave and the S-polarized wave is allowed to pass and the other is reflected. be able to.

  As described above, since the directions of the same polarized wave are aligned by the split-type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or a polarizer).

  When the direction of the polarization beam splitter 174 is set by the drive mechanism 175 so that the P-polarized wave can pass, the light (P-polarized wave) that has passed through the polarization beam splitter 174 enters the imaging lens 176 and forms an image. The lens 176 (first imaging lens) has a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reduction optical system) of the exposure apparatus. To form an image on the photodiode array 105.

  The photodiode array 105 (image sensor) captures an image (P-polarized component image) (first image) formed by the imaging lens 176.

  Note that, for example, a TDI sensor is preferably used as the photodiode array 105 as in the first embodiment. The photodiode array 105 (image sensor) captures an optical image of the corresponding polarization component of the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is placed is moving. As described above, the optical image may be picked up in units of the inspection stripe 20.

  The P-polarized light pattern image formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105, and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (stripe region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range having a maximum gradation when the amount of illumination light is 60% incident.

  Further, when acquiring an optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (calculation unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the P-polarized light stripe region image is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of P-polarized light is, for example, 8-bit unsigned data, and represents the brightness gradation (light quantity) of each pixel. The P-polarized light stripe area image output in the comparison circuit 108 is stored in the storage device 50.

  Next, the direction of the half-wave plate 177 is changed by the drive mechanism 175 so that the S-polarized wave can pass. Then, the S-polarized wave is imaged on the same inspection stripe 20 on which the P-polarized wave is imaged.

  The configuration and situation until the laser light (for example, DUV light) having a wavelength below the ultraviolet region, which is the inspection light, is generated from the light source 103 and the transmitted light of the mask substrate 101 is transmitted through the divided half-wave plate 172 are implemented. This is the same as the first embodiment. Therefore, the split half-wave plate 172 aligns the P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens 171 in directions orthogonal to each other. By aligning the directions, it is possible to arrange the prior environment so that the P-polarized wave can be separated and left. Alternatively, it is the same as in the first embodiment in that the prior environment can be adjusted so that the S-polarized wave can be left separately.

  The transmitted light that has passed through the split-type half-wave plate 172 is incident on the polarization beam splitter 174, and the polarization beam splitter 174 passes the S-polarized wave of the transmitted light and reflects the P-polarized wave.

  As described above, since the directions of the same polarized wave are aligned by the split-type half-wave plate 172, the P-polarized wave and the S-polarized wave can be separated by the polarizing beam splitter 174 (or a polarizer).

  Since the direction of the half-wave plate 177 is set by the drive mechanism 175 so that the S-polarized wave can pass, the light (S-polarized wave) that has passed through the polarization beam splitter 174 enters the imaging lens 176, The imaging lens 176 (imaging lens) allows incident light to have a numerical aperture (NAi = 0.0008) sufficiently smaller than the numerical aperture (NAi = 1.4) of the objective lens 302 (reduction optical system) of the exposure apparatus. An image is formed on the photodiode array 105.

  The photodiode array 105 (image sensor) captures an image (image of an S-polarized component) (second image) formed by the imaging lens 176.

  The photodiode array 105 (image sensor) captures an optical image of the corresponding polarization component of the pattern formed on the mask substrate 101 while the XYθ table 102 on which the mask substrate 101 is placed is moving. As described above, the optical image may be picked up in units of the inspection stripe 20.

  The S-polarized light pattern image formed on the photodiode array 105 is photoelectrically converted by the respective light receiving elements of the photodiode array 105 and further A / D (analog / digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. When capturing such pixel data (stripe region image), the dynamic range of the photodiode array 105 is preferably, for example, a dynamic range having a maximum gradation when the amount of illumination light is 60% incident.

  Further, when acquiring an optical image of the inspection stripe 20, the laser length measurement system 122 measures the position of the XYθ table 102. The measured position information is output to the position circuit 107. The position circuit 107 (calculation unit) calculates the position of the mask substrate 101 using the measured position information.

  Thereafter, the stripe region image of S-polarized light is sent to the comparison circuit 108 together with data indicating the position of the mask substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) of S-polarized light is, for example, 8-bit unsigned data, and represents the brightness gradation (light quantity) of each pixel. The S-polarized light stripe region image output in the comparison circuit 108 is stored in the storage device 52.

  As described above, according to the third embodiment, the polarization images of the S-polarized wave and the P-polarized wave, which are the basis for creating the exposure image when transferred by the exposure apparatus, are acquired at different times. it can. Then, the acquired polarization image of the P-polarized wave is matched with the state of the P-polarized component whose amplitude is reduced, eliminated, or reversed by the objective lens 302 (reduction optical system) of the exposure apparatus, and then the S-polarized wave By combining with a polarized image, an exposure image can be created. According to the third embodiment, since the imaging is performed with the S-polarized wave and the P-polarized wave separated, it is possible to adjust one polarization component image.

  The inspection apparatus 100 according to the third embodiment further performs a pattern inspection of the mask substrate 101 using the polarization images of the S-polarized wave and the P-polarized wave. The inspection method may be the same as in the first embodiment.

  In the above description, each “˜circuit” or “˜unit” includes one arithmetic circuit, and the arithmetic circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, and the like. Is included. Further, a common circuit (the same circuit) may be used as the arithmetic circuit included in each “˜circuit” or each “˜unit”. Alternatively, different circuits (separate circuits) may be used. A program for executing a processor or the like may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (read only memory). For example, the position circuit 107, the comparison circuit 108, the autoloader control circuit 113, the table control circuit 114, and the like may be configured by at least one circuit described above. Similarly, the frame division units 54 and 56, the correction unit 62, the synthesis unit 64, the alignment unit 70, and the comparison unit 72 may be configured by at least one circuit described above.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In the above-described example, the tone value of the P-polarized wave frame image is corrected to match the exposure image, and then the corrected P-polarized wave frame image (first optical image) is not corrected. Although the case where the frame image (second optical image) by the polarization wave is synthesized has been described, the present invention is not limited to this. Since it is a die-to-die inspection, it is not necessary to match the exposure image as long as the images are synthesized in the same manner. Therefore, the exposure image may be combined at a different ratio. Further, the first optical image and the second optical image may be independently used for inspection without being combined. Moreover, although the example mentioned above demonstrated the case where the distance between adjacent patterns was test | inspected, it is not restricted to this. For example, the synthesized frame image (first die image) and the synthesized frame image (second die image) may be compared for each pixel using a predetermined algorithm. For example, the defect may be determined when the difference obtained by subtracting the gradation value of the combined frame image (second die image) from the gradation value of the combined frame image (first die image) is larger than a threshold value.

  In addition, although descriptions are omitted for parts and the like that are not directly required for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used.

  In addition, all polarization image acquisition apparatuses, pattern inspection apparatuses, and polarization image acquisition methods that include elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Inspection area | region 20 Inspection stripe 30 Frame area | region 50,52,58,60,66,68 Memory | storage device 54,56 Frame division part 62 Correction | amendment part 64 Synthesis | combination part 70 Positioning part 72 Comparison part 100 Inspection apparatus 101 Mask substrate 102 XYθ table 103 Light source 104 Magnifying optical system 105, 205 Photo diode array 106, 206 Sensor circuit 107 Position circuit 108 Comparison circuit 109 Magnetic disk device 110 Control computer 113 Autoloader control circuit 114 Table control circuit 115 Magnetic tape device 116 FD
117 CRT
118 Pattern Monitor 119 Printer 120 Bus 122 Laser Length Measuring System 123, 223 Stripe Pattern Memory 150 Optical Image Acquisition Unit 160 Control System Circuit 170 Transmitted Illumination Optical System 171 Objective Lens 172 Splitting Type Half-Wave Plate 174 Polarizing Beam Splitters 176, 178 Imaging lens 177 Half-wave plate 180 Projection lens 181 Illumination shape switching mechanism 182 Imaging lens 190 Transmitted light 192 Light 300 Mask substrate 301 Transmitted light 302 Objective lens 304 Semiconductor substrate 305 Light

Claims (6)

A movable stage on which a mask substrate for exposure on which a pattern is formed is placed;
A case in which the reduction optical system of the exposure apparatus that enters the exposed light from the mask substrate and forms an image on the exposed substrate when the mask substrate is disposed in the exposure apparatus receives the transmitted light from the mask substrate; An objective lens that has the same numerical aperture and that receives the transmitted light that is transmitted through the mask substrate as illumination light imaged on the mask substrate;
The P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens are arranged on the opposite side of the mask substrate with respect to the objective lens and in the vicinity of the pupil position of the objective lens. A split type half-wave plate aligned in an orthogonal direction;
A limiting mechanism configured by one of a polarizer and a polarizing beam splitter that passes one of the P-polarized wave and the S-polarized wave of the transmitted light and restricts the other;
A drive mechanism that rotates the restriction mechanism so that the restriction mechanism passes the other and restricts the passage of the one;
An imaging lens that forms an image of light that has passed through the limiting mechanism with a sufficiently smaller numerical aperture than the reduction optical system of the exposure apparatus;
An image sensor that captures an image formed by the imaging lens;
A polarization image acquisition device comprising: A movable stage on which a mask substrate for exposure on which a pattern is formed is placed;
A case in which the reduction optical system of the exposure apparatus that enters the exposed light from the mask substrate and forms an image on the exposed substrate when the mask substrate is disposed in the exposure apparatus receives the transmitted light from the mask substrate; An objective lens that has the same numerical aperture and that receives the transmitted light that is transmitted through the mask substrate as illumination light imaged on the mask substrate;
The P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens are arranged on the opposite side of the mask substrate with respect to the objective lens and in the vicinity of the pupil position of the objective lens. A split type half-wave plate aligned in an orthogonal direction;
A limiting mechanism configured by one of a polarizer and a polarizing beam splitter that passes one of the P-polarized wave and the S-polarized wave of the transmitted light and restricts the other;
A half-wave plate that rotates the polarization direction by 90 ° so that the limiting mechanism passes the other and restricts the passing of the one;
A drive mechanism for rotating the half-wave plate for rotation;
An imaging lens that forms an image of light that has passed through the limiting mechanism with a sufficiently smaller numerical aperture than the reduction optical system of the exposure apparatus;
An image sensor that captures an image formed by the imaging lens;
A polarization image acquisition device comprising: A movable stage on which a mask substrate for exposure on which a pattern is formed is placed;
A case in which the reduction optical system of the exposure apparatus that enters the exposed light from the mask substrate and forms an image on the exposed substrate when the mask substrate is disposed in the exposure apparatus receives the transmitted light from the mask substrate; An objective lens that has the same numerical aperture and that receives the transmitted light that is transmitted through the mask substrate as illumination light imaged on the mask substrate;
The P-polarized wave and the S-polarized wave of the transmitted light after passing through the objective lens are arranged on the opposite side of the mask substrate with respect to the objective lens and in the vicinity of the pupil position of the objective lens. A split type half-wave plate aligned in an orthogonal direction;
A polarizing beam splitter that transmits one of the P-polarized wave and the S-polarized wave of the transmitted light and reflects the other;
A first imaging lens for imaging light having passed through the polarizing beam splitter with a sufficiently smaller numerical aperture than the reduction optical system of the exposure apparatus;
A first image sensor that captures an image formed by the first imaging lens;
A second imaging lens that images light reflected by the polarizing beam splitter with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
A second image sensor that captures an image formed by the second imaging lens;
A polarization image acquisition device comprising: The polarized image acquisition device according to any one of claims 1 to 3,
A combining unit that combines the first optical image by the one of the P-polarized wave and the S-polarized wave and the second optical image by the other of the P-polarized wave and the S-polarized wave;
The first die image in which the first and second optical images in the first die are combined, and the first and second in the second die in which the same pattern as the first die is formed. A comparison unit that compares a second die image corresponding to the first die image, in which an optical image is combined;
A pattern inspection apparatus comprising: Forming an illumination light image on a mask substrate for exposure on which a pattern is formed;
A case in which the reduction optical system of the exposure apparatus that enters the exposed light from the mask substrate and forms an image on the exposed substrate when the mask substrate is disposed in the exposure apparatus receives the transmitted light from the mask substrate; A step of causing the illumination light to pass through the mask substrate and enter the objective lens with the same numerical aperture;
The transmitted light after passing through the objective lens using a split-type half-wave plate disposed at a position opposite to the mask substrate with respect to the objective lens and in the vicinity of the pupil position of the objective lens Aligning the P-polarized wave and the S-polarized wave in directions orthogonal to each other;
Passing one of the P-polarized wave and the S-polarized wave of the transmitted light and limiting the other;
Imaging one of the P-polarized wave and the S-polarized wave that has passed through an image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the image sensor to capture a first image formed by the one of the P-polarized wave and the S-polarized wave that have been imaged;
Outputting an optical image of the first image;
Passing the other of the P-polarized wave and the S-polarized wave of the transmitted light, and restricting the passage of the one;
Forming the other of the P-polarized wave and the S-polarized wave that has passed through the image sensor with the numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the image sensor to capture a second image by the other of the P-polarized wave and the S-polarized wave that have been imaged;
Outputting an optical image of the second image;
A polarization image acquisition method comprising: Forming an illumination light image on a mask substrate for exposure on which a pattern is formed;
A case in which the reduction optical system of the exposure apparatus that enters the exposed light from the mask substrate and forms an image on the exposed substrate when the mask substrate is disposed in the exposure apparatus receives the transmitted light from the mask substrate; A step of causing the illumination light to pass through the mask substrate and enter the objective lens with the same numerical aperture;
The transmitted light after passing through the objective lens using a split-type half-wave plate disposed at a position opposite to the mask substrate with respect to the objective lens and in the vicinity of the pupil position of the objective lens Aligning the P-polarized wave and the S-polarized wave in directions orthogonal to each other;
Passing one of the P-polarized wave and the S-polarized wave of the transmitted light and reflecting the other;
Imaging one of the P-polarized wave and the S-polarized wave that has passed through the first image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus;
Using the first image sensor to capture a first image formed by the one of the P-polarized wave and the S-polarized wave formed,
Outputting an optical image of the first image;
Forming the other reflected one of the P-polarized wave and the S-polarized wave of the transmitted light on a second image sensor with a numerical aperture sufficiently smaller than the reduction optical system of the exposure apparatus; ,
Using the second image sensor to capture a second image by the other of the P-polarized wave and the S-polarized wave that have been imaged;
Outputting an optical image of the second image;
A polarization image acquisition method comprising:

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