JPS6378012A - Pattern inspecting instrument - Google Patents

Abstract

PURPOSE:To easily execute an inspection of a minute pattern, and also, to execute the inspection at a high speed by providing an image position moving means for allowing an image forming position of a linear light beam to an object to be inspected, to correspond to a detection by a line sensor, and moving it successively in the optical axis direction. CONSTITUTION:The titled device is provided with image position moving means 26, 28 for allowing an image forming position of a linear light beam to an object M to be inspected to correspond to a detection by a line sensor 27 and moving it successively in the optical axis direction. In this way, the image forming position of this linear light beam is moved in the optical axis direction, and also, it is detected successively by the sensor 27, and height data of each position of a pattern for running along not a point but a line are obtained at a single stroke. Accordingly, the inspection speed is improved remarkably, and also, by using fully the photodetecting surface of an objective lens 26, a light beam of a large diameter can be made incident, the light beam can be reduced to an extremely small diameter, and a very minute pattern can also be inspected.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a pattern inspection device that detects the three-dimensional shape of a fine pattern using a linear light beam, so that even very fine patterns can be easily detected. In addition, in order to improve the inspection speed, an image position moving means is provided for sequentially moving the imaging position of the linear light beam in the optical axis direction.

[Industrial application field]

The present invention relates to a pattern inspection device that automatically inspects the three-dimensional shape of a fine pattern (for example, a wiring pattern formed on a wafer such as an IC or LSI) using a line-shaped light beam.

As wiring patterns become finer and more dense, there is an increasing demand for detecting the three-dimensional shape of conductor wiring. Especially IC
The shape of conductors is becoming submicron or smaller. In such fields, visual inspection by humans is no longer possible, and automation of inspection is strongly desired.

[Conventional technology]

The schematic configuration of the optical system related to the conventional pattern inspection device is shown in the third section.
As shown in the figure. In the figure, a long linear light beam 1 perpendicular to the plane of the paper is made incident through a part of an objective lens 1, and is irradiated onto an object M to be inspected obliquely from above. Then, on the object M to be inspected, a linear image is obtained along the unevenness of the pattern formed there. Therefore, the reflected light (broken line) in a direction different from the direction of the irradiation is formed into an image by the lens 2 via another part of the objective lens 1. Then, there is a peak of light intensity at a position corresponding to the height of the pattern on the object M to be inspected. For example, different peak positions P1 and P2 are obtained from reflected lights from different heights hl and h2. Therefore, by detecting these peak positions with the photodetector 3, height data at each position of the pattern can be obtained based on the positions.
The three-dimensional shape of the pattern can be detected from these height data.

Further, FIG. 5 shows a schematic configuration of an optical system related to another conventional device. In the figure, a light beam from a laser 11 is condensed by a lens 12, and an image is formed on an object to be inspected M via a half mirror 13 by an objective lens 14 movable in the optical axis direction. Next, the reflected light is reflected by a half mirror 13 and detected by a photomultiplier tube 16 through a pinhole 15. At this time, by moving the objective lens 14 up and down in the optical axis direction, the photomultiplier 16 can obtain the maximum signal strength when the detection surface and the imaging position of the light beam coincide. Therefore, the height of the detection surface can be determined from the imaging position of the light beam when the maximum signal intensity is obtained in the photomultiple 16. In this way, the three-dimensional shape of the pattern can be detected from the height data obtained at each point of the object M to be inspected.

[Problem that the invention seeks to solve]

In the former device described above, it is necessary to use one objective lens 1 for the illumination light and the reflected light, and to make their directions different from each other.
It is only possible to use one part that is offset from the center of the
Therefore, the diameter of the light beam must be reduced accordingly. Then, for example, as shown by the broken line in FIG.
When the beam is incident, the beam diameter can be narrowed down to a very small size as shown by the dotted line in Figure ('b), but on the other hand,
The above light beam of small diameter2. When the light beam 12 is incident, it is no longer possible to focus the light beam as small as the light beam 12, as shown by the solid line in FIG.

The diameter of the light beam has a great deal to do with the detection performance, so if the diameter of the light beam β cannot be narrowed down to a small size as described above, it will be impossible to inspect fine patterns, which will lead to finer patterns in the future. There is a risk that it will not be possible to follow.

In addition, in the latter device described above, since the light receiving surface of the objective lens 14 is fully used, the diameter of the light beam can be narrowed down to a very small size. The problem is that it takes a lot of time.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a pattern inspection apparatus that can easily inspect even very fine patterns and can also speed up the inspection.

Means for Solving Problem C] The present invention focuses a linear light beam on an object to be inspected through an objective lens, and sequentially detects the linear images obtained by this using a line sensor. The pattern inspection apparatus is provided with an image position moving means for sequentially moving the image formation position of the linear light beam on the object to be inspected in the optical axis direction in correspondence with the detection by the line sensor. be.

[For production]

By moving the imaging position of the above linear light beam in the optical axis direction and sequentially detecting it with a line sensor,
Height data along "lines" instead of "points" can be obtained all at once. Therefore, compared to the one-point inspection shown in FIG. 5, the inspection principle is the same, but the inspection speed is significantly improved.

Moreover, according to the inspection principle of the apparatus shown in FIG. 5, since the entire light receiving surface of the objective lens can be used to make a large diameter light beam incident, the light beam can be narrowed down to an extremely small diameter. Therefore, even very fine patterns can be inspected.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the present invention. In this embodiment, first, the light beam Jl output from the laser 21 is
After the + is reflected by the mirror 22, it is spread in only one direction (X direction) by the cylindrical lens 23. The light beams l and 2 thus expanded only in the X direction are transmitted through the lens 24, and then incident on the objective lens 26 via the half mirror 25, forming linear light beams β,
4, an image is formed on the object M to be inspected from directly above. Then, a linear image is formed there on a plane that coincides with the imaging position of the light beam 114. This image is transmitted to the line sensor 2 via the objective lens 26 and the half mirror 25.
Detected at 7.

Note that the objective lens 26 is fixed to, for example, a piezo element (not shown) whose movable direction is in the direction of its optical axis.
By driving the piezo element with the lens driving section 28, the objective lens 26 can be sequentially moved in the optical axis direction.

If the objective lens 26 is moved in the optical axis direction in this way,
Along with that, the above linear light beam! ! The 14 imaging positions are
It moves in the optical axis direction relative to the object M to be inspected.

That is, in this embodiment, the imaging position of the light beam 114 is sequentially moved by moving the objective lens 26 in the direction of its optical axis.

Next, height detection based on the movement of the imaging position will be specifically explained. If the objective lens 26 is moved in the direction of its optical axis as described above, a linear image will be formed on the plane that coincides with the imaging position of the light beam Nla.
The maximum signal intensity is obtained from the area where the linear image is detected by the sensor 27. For example, in the example shown in FIG. 1, if the imaging position is brought to the substrate R by moving the objective lens 26 downward, a linear image L1 will be formed at that position, so the line sensor The highest signal intensity is obtained from the region corresponding to the above-mentioned image at 27, and only minute signal intensity is obtained from the other regions. On the other hand, if the image forming position is brought to the conductor portion Q by moving the objective lens 26 upward from the above position by Δh, the line image L2 is formed only at that position, so that the line sensor 27 The highest signal intensity is obtained from the area corresponding to image L2, and only minute signal intensity is obtained from the other areas. Therefore, the objective lens 26 is moved from below to above (or from above to below) along its front axis direction, and the line sensor 27 sequentially captures the images formed on the substrate R or the conductor part Q accordingly. By performing the detection, a two-dimensional image corresponding to an image cut by the line-shaped light beams 1 and 4 is obtained.

Note that in the above detection, the movement of the objective lens 26 and the detection of the line sensor 27 are synchronized with each other by the lens drive section 28 and the sensor drive section (and amplifier) 29 based on a command from the CPU 32.

The two-dimensional image obtained from the line sensor 27 is sent to the image processing unit 31 via the sensor drive unit (and amplification unit) 29.
can be stored in The image processing unit 31 first detects the height at each position in the X direction along the linear light beam 114 based on the two-dimensional image. By performing such height detection at each position of the object to be inspected M while sequentially moving the xy stage S in the X and X directions by the stage drive unit 30, the three-dimensional shape of the pattern formed by the conductor portion Q can be obtained. Finally, by comparing the three-dimensional shape obtained in this manner with a reference shape, defects in the pattern are determined.

As described above, according to this embodiment, by moving the objective lens 26, the imaging position of the linear light beam ji'+4 is moved in the optical axis direction, and this is sequentially detected by the line sensor 27. Therefore, instead of inspecting each "point" as shown in FIG. 5, a long area along a "line" can be inspected at once. Therefore, this example is a "point"
Inspection speed is significantly improved compared to regular inspection.

Furthermore, as shown in FIG. 3, the area in which the objective lens is used does not have to be limited to a portion, and the entire light receiving surface of the objective lens 26 can be used to allow a large diameter light beam to enter. Therefore, like the light beam 12 shown in FIG. 4, the linear light beam j2+4 can be focused to an extremely small diameter. Therefore, it becomes possible to inspect even very fine patterns with high precision.

Next, the configuration of another embodiment of the present invention is shown in FIG. In this embodiment, as a means for moving the imaging position of the linear light beam β14, instead of the vertical movement of the objective lens 26 in the embodiment of FIG. It is provided between the lenses 24 to produce a cylindrical lens effect as described below.

The ultrasonic deflector 40 is arranged in a direction (
The ultrasonic wave has a deflection direction (X direction), and a deflection angle corresponding to the frequency distribution of the diffraction grating generated within the ultrasonic medium. By giving such an ultrasonic deflector 40 a frequency distribution such that the light that has passed through it is spread in the X direction by a cylindrical lens, the ultrasonic deflector 40 can be , it can be considered as a cylindrical lens 40a indicated by a broken line. The frequency distribution of the diffraction grating for obtaining such a cylindrical lens 40a can be obtained by giving a necessary frequency variation to the drive signal output from the deflector drive unit 41.

In this embodiment, the ultrasonic deflector 40 is used as the cylindrical lens 40a, and the state of the frequency fluctuation is gradually changed to sequentially change the focal length of the cylindrical lens 40a. A linear light beam! , 4 are sequentially moved in the optical axis direction. Note that the change in the focal length of the cylindrical lens 40a and the detection by the line sensor 27 are performed by the deflector drive unit 41 based on the command from the CPU 32.
and the sensor driver (and amplifier) 29.

In this way, using the ultrasonic deflector 40, the light beam jl'
Even if the +4 imaging position is moved and sequentially detected by the line sensor 27, the three-dimensional shape of the pattern can be obtained in the same manner as in the embodiment shown in FIG.

According to this embodiment, the light beam E is similar to the embodiment shown in FIG.
14 can be narrowed down to an extremely small diameter, making it possible to inspect extremely fine patterns with high precision. Furthermore, since the inspection is performed by "line" and the imaging position can be moved faster by the ultrasonic deflector 40 than by moving the objective lens 26, the inspection speed is further improved.

In each of the above embodiments, the absolute imaging position of the linear light beam jll+4 is moved, but even if the relative imaging position with respect to the object M to be inspected is moved. good. For example, instead of moving the absolute imaging position, the imaging position may be fixed and the xy stage S
may be moved in the optical axis direction.

Further, the means for creating the linear light beam 114 is not limited to the above-mentioned cylindrical lens 23, etc., and for example, an ultrasonic deflector having a deflection direction in the X direction may be used to direct the light in the X direction. By waving it linearly,
A substantially linear light beam can be obtained.

〔Effect of the invention〕

According to the pattern inspection device of the present invention, the light beam can be narrowed down to an extremely small size on the surface of the object to be inspected, making it possible to inspect extremely fine patterns, which is sufficient to withstand the trend of finer patterns in the future. will be able to follow. Moreover, since a linear light beam is used, it is possible to
Since the inspection is performed by "line", the inspection speed can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, FIG. 3 is a schematic block diagram showing an optical system related to a conventional device, and FIG. Figures (a) and (b) are diagrams for explaining the problems of the above-mentioned conventional device, and FIG. 5 is a configuration diagram showing the optical system of another conventional device. 21... Laser, 23... Cylindrical lens, 26... Objective lens, 27... Line sensor, 28... Lens drive unit, 40... Ultrasonic deflector, 41... Deflector Drive part. Figure 3: Figure 5

Claims (1)

[Claims] 1) Imaging means (
21, 22, 23, 24, 26; 40), and a line sensor (
27) in a pattern inspection apparatus having detection means (26, 25, 27, 29, 31) that sequentially detects the three-dimensional shape of the fine pattern, Image position moving means (26, 28; 40, 41) that sequentially moves the image position in the optical axis direction in correspondence with the detection by the line sensor.
A pattern inspection device characterized by being provided with. 2) The image position moving means comprises the objective lens (26) and lens driving means (28, etc.) for moving the objective lens in the optical axis direction. The pattern inspection device described. 3) The pattern inspection apparatus according to claim 2, wherein the lens driving means includes a piezo element to which the objective lens is fixed and is driven by a predetermined drive signal. 4) The image position moving means includes an ultrasonic wave deflector (40) disposed in front of the objective lens, and a deflector that produces a cylindrical lens effect whose focal length sequentially changes with respect to the ultrasonic deflector. The pattern inspection apparatus according to claim 1, characterized in that it comprises a driving means (41). 5) The deflector driving means provides the ultrasonic deflector with a drive signal having a frequency variation for producing the cylindrical lens effect.
The pattern inspection device described in Section 1.