Image processing apparatus, image processing method, optical device, method of using optical device, and image processing program

Abstract

To provide an image processing apparatus configured to simply and accurately determine the quality of the contrast of a pattern.SOLUTION: An image processing apparatus 100 includes: a captured image acquisition unit 10 which acquires a captured image G10 pf a sample 50 with a pattern PT having a first portion 51 and a second portion 52 different in reflectance; a first acquisition unit 11 which performs Fourier transform on the captured image G10 to obtain a first spatial frequency distribution G11; a second acquisition unit 12 which applies a filter for removing components other than a frequency component, to the first spatial frequency distribution G11 to obtain a second spatial frequency distribution G12; an information processing unit 13 which performs predetermined information processing on the second spatial frequency distribution G12 to obtain an information processing result G13; and an evaluation unit 14 which evaluates the contrast between the first portion 51 and the second portion 52 of the pattern PT in the captured image G10, based on the information processing result G13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an image processing device, an image processing method, an optical device, a method for using an optical device, and an image processing program. [Background technology]

[0002] Patent Document 1 describes an inspection device that takes an image of a pattern surface of a sample and inspects it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-107110 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to easily and accurately evaluate the quality of the contrast of a pattern in an image of a sample.

[0005] The purpose of the present disclosure has been made to solve such problems, and is to provide an image processing device, an image processing method, an optical device, a method for using an optical device, and an image processing program that can accurately evaluate the quality of pattern contrast. [Means for solving the problem]

[0006] The image processing device according to the present disclosure includes an image acquisition unit that acquires an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; a first acquisition unit that performs a Fourier transform on the image to acquire a first spatial frequency distribution; a second acquisition unit that applies a filter to the first spatial frequency distribution that removes frequency components other than those in the pattern region, thereby acquiring a second spatial frequency distribution after the components other than the frequency components have been removed; an information processing unit that performs predetermined information processing on the second spatial frequency distribution to acquire an information processing result; and an evaluation unit that evaluates the image based on the information processing result, wherein the evaluation unit evaluates the contrast between the first portion and the second portion of the pattern in the image.

[0007] In the image processing device, the information processing unit may obtain a transformed image by performing an inverse Fourier transform on the second spatial frequency distribution as a result of the information processing, and the evaluation unit may evaluate a parameter based on the luminance of the first part and the second part in the transformed image.

[0008] In the image processing device, the information processing unit may obtain an arithmetic result as the information processing result by performing arithmetic on the second spatial frequency distribution, the arithmetic result including a formula equivalent to a differential filter, and the evaluation unit may evaluate a parameter based on the luminance of the first part and the second part in the arithmetic result.

[0009] In the image processing device, the pattern may include a specific pattern in which the first portion and the second portion are formed in a predetermined direction under predetermined repetition conditions.

[0010] In the image processing device, the information processing unit may obtain, as a result of the information processing, a modulated image that has been subjected to modulation processing to reduce the overall intensity in the second spatial frequency distribution, and the evaluation unit may evaluate a parameter based on the brightness of the first part and the second part in the modulated image.

[0011] an information processing unit that performs a modulation process on the first spatial frequency distribution or the modulation image to reduce the overall intensity of the first spatial frequency distribution when the pattern does not include the specific pattern; and an evaluation unit that evaluates the captured image. The information processing unit performs a predetermined information processing on the second spatial frequency distribution or the modulation image to obtain an information processing result, and the evaluation unit evaluates the contrast between the first and second portions of the pattern in the captured image based on the information processing result.

[0012] In the image processing device, the information processing unit may obtain a transformed image by performing an inverse Fourier transform on the second spatial frequency distribution as a result of the information processing, and the evaluation unit may evaluate a parameter based on the luminance of the first part and the second part in the transformed image.

[0013] In the image processing device, the information processing unit may obtain an arithmetic result as the information processing result by performing arithmetic on the second spatial frequency distribution, the arithmetic result including a formula equivalent to a differential filter, and the evaluation unit may evaluate a parameter based on the luminance of the first part and the second part in the arithmetic result.

[0014] The image processing device may further include a setting unit that sets a plurality of imaging conditions for the same pattern area, wherein the captured image acquisition unit acquires a plurality of captured images captured under the plurality of imaging conditions for the same pattern area, the first acquisition unit acquires the first spatial frequency distribution for the plurality of captured images, the second acquisition unit acquires the second spatial frequency distribution for the plurality of captured images, the information processing unit acquires the information processing results for the plurality of captured images, and the evaluation unit evaluates the plurality of captured images based on the plurality of information processing results.

[0015] The image processing device may further include an inspection unit that inspects the sample for defects based on an image captured under the imaging conditions having a predetermined contrast among the plurality of captured images evaluated by the evaluation unit.

[0016] The image processing method according to the present disclosure includes the steps of: causing an image acquisition unit to acquire an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; causing a first acquisition unit to acquire a first spatial frequency distribution by Fourier transforming the image; causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components by applying a filter to the first spatial frequency distribution that removes frequency components other than those in the pattern region; causing an information processing unit to acquire a result of the information processing by performing a predetermined information processing on the second spatial frequency distribution; and causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the image based on the result of the information processing.

[0017] In the image processing method, in the step of having the information processing unit acquire the information processing result, a transformed image obtained by performing an inverse Fourier transform on the second spatial frequency distribution may be acquired as the information processing result, and in the step of evaluating, a parameter based on the luminance of the first part and the second part in the transformed image may be evaluated.

[0018] In the image processing method, in the step of having the information processing unit acquire the information processing result, an arithmetic result may be acquired as the information processing result by performing arithmetic on the second spatial frequency distribution, including a formula equivalent to a differential filter, and in the step of evaluating, a parameter based on the luminance of the first part and the second part in the arithmetic result may be evaluated.

[0019] In the image processing method, the pattern may include a specific pattern in which the first portion and the second portion are formed in a predetermined direction under predetermined repetition conditions.

[0020] In the image processing method, in the step of having the information processing unit acquire the information processing result, a modulated image that has been modulated to reduce the overall intensity in the second spatial frequency distribution may be acquired as the information processing result, and in the step of evaluating, a parameter based on the luminance of the first part and the second part in the modulated image may be evaluated.

[0021] an image processing method according to the present disclosure, comprising the steps of: causing an image acquisition unit to acquire an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; causing a first acquisition unit to acquire a first spatial frequency distribution by Fourier transforming the image; causing a determination unit to determine whether the pattern includes a specific pattern in which the first portion and the second portion are formed under specific repetition conditions in a specific direction; if the pattern includes the specific pattern, causing a second acquisition unit to apply a filter to the first spatial frequency distribution that removes frequency components other than those in the pattern region, and acquire a second spatial frequency distribution after the components other than the frequency components have been removed; if the pattern does not include the specific pattern, causing an information processing unit to acquire a modulated image that has been modulated to reduce the overall intensity in the first spatial frequency distribution; causing the information processing unit to acquire a result of the information processing by performing specific information processing on the second spatial frequency distribution or the modulated image; and causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the image based on the result of the information processing.

[0022] In the image processing method, in the step of having the information processing unit acquire the information processing result, a transformed image obtained by performing an inverse Fourier transform on the second spatial frequency distribution may be acquired as the information processing result, and in the step of evaluating, a parameter based on the luminance of the first part and the second part in the transformed image may be evaluated.

[0023] In the image processing method, in the step of having the information processing unit acquire the information processing result, an arithmetic result may be acquired as the information processing result by performing arithmetic on the second spatial frequency distribution, including a formula equivalent to a differential filter, and in the step of evaluating, a parameter based on the luminance of the first part and the second part in the arithmetic result may be evaluated.

[0024] The image processing method may further include a step of causing a setting unit to set a plurality of imaging conditions for the same pattern area, and in the step of causing the captured image acquisition unit to acquire, the captured image acquisition unit is caused to acquire a plurality of the captured images captured under the plurality of imaging conditions for the same pattern area, and in the step of causing a first acquisition unit to acquire the first spatial frequency distribution, the first acquisition unit is caused to acquire the first spatial frequency distribution for the plurality of captured images, and in the step of causing a second acquisition unit to acquire the second spatial frequency distribution, the second acquisition unit is caused to acquire the second spatial frequency distribution for the plurality of captured images, and in the step of causing an information processing unit to acquire the information processing results for the plurality of captured images, the information processing unit is caused to acquire the information processing results for the plurality of captured images, and in the step of evaluating, the evaluation unit is caused to evaluate the plurality of captured images based on the plurality of information processing results.

[0025] The image processing method may further include a step of having an inspection unit inspect defects in the sample based on an image captured under the imaging conditions having a predetermined contrast among the multiple captured images evaluated by the evaluation unit.

[0026] The optical device according to the present disclosure includes an optical system that illuminates a sample with illumination light and collects detection light from the illuminated sample, a detector that detects the detection light, and the image processing device described above.

[0027] A method of using an optical device according to the present disclosure includes the steps of illuminating a sample with illumination light and collecting detection light from the illuminated sample using an optical system, detecting the detection light with a detector, and performing the image processing method described above.

[0028] An image processing program according to the present disclosure causes a computer to perform the following operations: acquire an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; Fourier transform the image, causing the first acquisition unit to acquire a first spatial frequency distribution; apply a filter to the first spatial frequency distribution that removes frequency components other than those in the pattern region, causing the second acquisition unit to acquire a second spatial frequency distribution after the removal of the frequency components other than those in the first spatial frequency distribution; perform predetermined information processing on the second spatial frequency distribution, causing an information processing unit to acquire an information processing result; and cause an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the image based on the information processing result.

[0029] An image processing program according to the present disclosure causes a computer to execute the following steps: acquire an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; cause a first acquisition unit to perform a Fourier transform on the image; cause a determination unit to determine whether the pattern includes a specific pattern in which the first portion and the second portion are formed under specific repetition conditions in a specific direction; if the pattern includes the specific pattern, apply a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and cause a second acquisition unit to acquire a second spatial frequency distribution after the components other than the frequency components have been removed; if the pattern does not include the specific pattern, cause an information processing unit to acquire a modulated image that has been modulated to reduce the overall intensity in the first spatial frequency distribution; perform specific information processing on the second spatial frequency distribution or the modulated image, thereby causing the information processing unit to acquire a result of the information processing; and cause an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the image based on the result of the information processing. [Effects of the Invention]

[0030] According to the present disclosure, the quality of the contrast of a pattern can be evaluated simply and accurately. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a block diagram illustrating an image processing device according to a first embodiment. [Figure 2] 2 is a schematic diagram illustrating a captured image acquired by a captured image acquisition unit in the image processing device according to the first embodiment. FIG. [Figure 3] 4 is a schematic diagram illustrating a first spatial frequency distribution acquired by a first acquisition unit in the image processing device according to the first embodiment. FIG. [Figure 4] 4 is a schematic diagram illustrating a second spatial frequency distribution acquired by a second acquisition unit in the image processing device according to the first embodiment. FIG. [Figure 5] 3 is a schematic diagram illustrating an example of an information processing result acquired by an information processing unit in the image processing device according to the first embodiment. FIG. [Figure 6] FIG. 2 is a flowchart illustrating an image processing method using the image processing device according to the first embodiment. [Figure 7] 1 is a block diagram illustrating an image processing device according to a first embodiment. [Figure 8] FIG. 10 is a block diagram illustrating an image processing device according to a modified example of the first embodiment. [Figure 9] FIG. 10 is a flowchart illustrating an image processing method using an image processing device according to a modified example of the first embodiment. [Figure 10] FIG. 10 is a block diagram illustrating an image processing device according to a second embodiment. [Figure 11] FIG. 10 is a flowchart illustrating an information processing method using the image processing device according to the second embodiment. [Figure 12] FIG. 10 is a block diagram illustrating an image processing device according to a modified example of the second embodiment. [Figure 13] FIG. 10 is a flowchart illustrating an image processing method using an image processing device according to a modified example of the second embodiment. [Figure 14]FIG. 10 is a configuration diagram illustrating an optical device according to a third embodiment. [Figure 15] FIG. 11 is a flowchart illustrating a method of using the optical device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, a specific configuration of the present embodiment will be described with reference to the drawings. The following description shows a preferred embodiment of the present disclosure, and the scope of the present disclosure is not limited to the following embodiment. In the following description, parts with the same reference numerals indicate substantially the same content.

[0033] <Embodiment 1> An image processing device and an image processing method according to embodiment 1 will be described. The image processing device of this embodiment may be applied to an optical device including an inspection device that inspects a sample for defects, etc., and a review device that displays an image of the sample. That is, the image processing device of this embodiment may be connected to an optical device such as an inspection device or review device, or may be incorporated into the optical device. The inspection device may include a review device, a storage device, and an image correction device, etc. The review device may include an inspection device, a storage device, and an image correction device, etc. The image processing device may perform image processing on images detected by the inspection device, images stored in the storage device, images input to the image correction device, etc.

[0034] Fig. 1 is a block diagram illustrating an image processing device 100 according to embodiment 1. As shown in Fig. 1, the image processing device 100 includes a captured image acquisition unit 10, a first acquisition unit 11, a second acquisition unit 12, an information processing unit 13, and an evaluation unit 14.

[0035] <Captured image> FIG. 2 is a schematic diagram illustrating a captured image G10 acquired by the captured image acquisition unit 10 in the image processing device 100 according to the first embodiment. As shown in FIG. 2, the captured image acquisition unit 10 acquires a captured image G10 of a sample 50. The sample 50 includes a pattern area PA in which a pattern PT is formed. The pattern PT may have a first portion 51 and a second portion 52. The first portion 51 and the second portion 52 may have different reflectances. For example, the first portion 51 may be expressed in black or a color close to black, and the second portion 52 may be expressed in white or a color close to white. Therefore, the pattern PT of the captured image G10 has contrast between the first portion 51 and the second portion 52.

[0036] Here, the horizontal direction of the captured image G10 is the X-axis direction, and the vertical direction is the Y-axis direction. The first portion 51 and the second portion 52 may have portions extending in the X-axis direction, for example. Note that in FIG. 2, the captured image G10 captures only a portion of the sample 50 including one second portion 52 and first portions 51 on both sides of it, but this is not limited to this. The captured image G10 may include a pattern PT having multiple first portions 51 and multiple second portions 52. The pattern PT may be formed by the first portions 51 and the second portions 52 in a predetermined direction under predetermined repetition conditions. A pattern in which the first portions 51 and the second portions 52 are formed in a predetermined direction under predetermined repetition conditions is called a specific pattern. As an example, the specific pattern may include a pattern in which multiple first portions 51 extending in the X-axis direction and multiple second portions 52 extending in the X-axis direction are formed in the Y-axis direction at a predetermined frequency.

[0037] The sample 50 may be, for example, a mask. In this case, the pattern PT includes a mask pattern. The first portion 51 may include one of the absorber and the multilayer of the mask, and the second portion 52 may include the other of the absorber and the multilayer.

[0038] <Spatial frequency distribution (first spatial frequency distribution)> 3 is a schematic diagram illustrating a first spatial frequency distribution G11 acquired by the first acquisition unit 11 in the image processing device 100 according to the first embodiment. As shown in FIG. 3, the first acquisition unit 11 acquires a spatial frequency distribution by performing a Fourier transform on the captured image G10. The spatial frequency distribution acquired by the first acquisition unit 11 is referred to as the first spatial frequency distribution G11. Here, the horizontal direction of the first spatial frequency distribution G11 is the u-axis direction, and the vertical direction is the v-axis direction.

[0039] <Spatial frequency distribution after removal (second spatial frequency distribution)> 4 is a schematic diagram illustrating a second spatial frequency distribution G12 acquired by the second acquisition unit 12 in the image processing device 100 according to the first embodiment. As shown in FIG. 4, the second acquisition unit 12 applies a filter to the first spatial frequency distribution G11 that removes components other than the frequency components in the pattern area PA, and acquires the spatial frequency distribution after removing the components other than the frequency components. The spatial frequency distribution acquired by the second acquisition unit 12 after removing the components other than the frequency components is referred to as the second spatial frequency distribution G12.

[0040] The frequency components in the first spatial frequency distribution G11 include components of the first portion 51 and the second portion 52. For example, in the case of a pattern PT formed by the first portion 51 extending in the X-axis direction and the second portion 52 extending in the X-axis direction, the components of the first portion 51 and the second portion 52 have components in the v-axis direction. In the case of a pattern PT formed by the first portion 51 extending in the Y-axis direction and the second portion 52 extending in the Y-axis direction, the components of the first portion 51 and the second portion 52 have components in the u-axis direction. The components other than the frequency components in the first spatial frequency distribution G11 include components other than the components of the first portion 51 and the second portion 52. Specifically, for example, the components other than the frequency components include surface roughness such as processing scratches on the surface of the multilayer. In this case, the second acquisition unit 12 acquires the second spatial frequency distribution G12 after removing the surface roughness components from the first spatial frequency distribution G11.

[0041] <Information processing results (converted image)> 5 is a schematic diagram illustrating an example of an information processing result G13 acquired by the information processing unit 13 in the image processing device 100 according to the first embodiment. As shown in FIG. 5, the information processing unit 13 acquires the information processing result G13 by performing predetermined information processing on the second spatial frequency distribution G12. For example, the information processing unit 13 may perform an inverse Fourier transform as the information processing performed on the second spatial frequency distribution G12. As a result, the information processing unit 13 may acquire, as the information processing result G13, a converted image G13a obtained by performing an inverse Fourier transform on the second spatial frequency distribution G12. Therefore, the information processing result G13 may include the converted image G13a.

[0042] The evaluation unit 14 evaluates the captured image G10 based on the information processing result G13. Specifically, the evaluation unit 14 evaluates the contrast between the first portion 51 and the second portion 52 of the pattern PT in the captured image G10 based on the information processing result G13. When the information processing result G13 includes a converted image G13a, the evaluation unit 14 may evaluate a parameter based on the luminance of the first portion 51 and the second portion 52 in the converted image G13a.

[0043] For example, the information processing unit 13 may apply a differential filter to the converted image G13a. In this case, the evaluation unit 14 may evaluate a value corresponding to the gradient of the luminance. The larger the value corresponding to the gradient at the boundary between the first portion 51 and the second portion 52, the greater the contrast. Therefore, the evaluation unit 14 can evaluate the contrast between the first portion 51 and the second portion 52 of the pattern PT by evaluating the gradient of the luminance as a parameter based on the luminance of the first portion 51 and the second portion 52. The information processing unit 13 may obtain a differential image by differentiating the luminance of each pixel in the converted image G13a using the luminance of pixels surrounding each pixel. In this case, the evaluation unit 14 evaluates the value of each pixel of the differential image.

[0044] <Information processing results (arithmetic results)> The information processing unit 13 may perform arithmetic shown in a predetermined formula as information processing on the second spatial frequency distribution G12. Thereby, the information processing unit 13 obtains an arithmetic result by performing arithmetic shown in the predetermined formula on the second spatial frequency distribution G12. For example, the information processing unit 13 performs processing shown in the following formula (1).

[0045] G(u, v)=F'(u, v)H(u, v) (1)

[0046] Here, G(u, v) represents the arithmetic result after information processing by the information processing unit 13. F'(u, v) represents the spatial frequency distribution after the removal, i.e., the second spatial frequency distribution G12. H(u, v) represents a filter for the second spatial frequency distribution G12. For example, H(u, v) functioning as a filter may be a Laplacian filter functioning as a differential filter of the following equation (2).

[0047] H(u, v) = -4π 2 (u 2 +v 2 ) (2)

[0048] The filter for the second spatial frequency distribution G12 is not limited to a Laplacian filter, and may be a Gaussian filter, a Sobel filter, or the like. In this way, the information processing unit 13 obtains an arithmetic result as the information processing result G13 by performing arithmetic including a formula corresponding to the filter for the second spatial frequency distribution G12. For example, by performing an inverse Fourier transform on the arithmetic result, a result obtained by applying a differential filter to the above-mentioned converted image G13a may be obtained.

[0049] The evaluation unit 14 evaluates a parameter based on the luminance of the first portion 51 and the second portion 52 in the arithmetic result. For example, the evaluation unit 14 performs the evaluation using an evaluation formula such as the following formula (3).

[0050] C=ΣAlog 10 |G(u, v)| (3)

[0051] Here, C indicates an evaluation value, which corresponds to the intensity distribution of the differential image in real space. That is, it corresponds to the contrast in the second spatial frequency distribution G12. A is a constant, and |G(u, v)| indicates the absolute value of the second spatial frequency distribution G(u, v).

[0052] <Information processing results (modulation processing)> The information processing unit 13 may obtain, as the information processing result G13, a modulated image obtained by performing a modulation process on the second spatial frequency distribution G12. The modulation process includes a process of reducing the overall intensity in the second spatial frequency distribution G12. In the modulated image, components other than the frequency components in the pattern area PA are reduced. Thus, the evaluation unit 14 can evaluate parameters based on the luminance of the first portion 51 and the second portion 52 in the modulated image.

[0053] Although the information processing unit 13 has been described as acquiring a modulated image obtained by performing a modulation process on the second spatial frequency distribution G12 (spatial frequency distribution after the removal) as the information processing result G13, this is not limiting. The information processing unit 13 may acquire a modulated image by performing a modulation process on the first spatial frequency distribution G11. The second acquisition unit 12 may acquire the second spatial frequency distribution G12 by applying a filter that removes frequency components other than those in the pattern area PA to the first spatial frequency distribution G11 after the modulation process. Furthermore, the information processing unit 13 may or may not perform a modulation process again on the second spatial frequency distribution G12 acquired in this manner. The information processing unit 13 may set a predetermined threshold and cause the determination unit 17, described later, to determine whether to perform a modulation process on the first spatial frequency distribution G11 and the second spatial frequency distribution G12.

[0054] Next, an information processing method of this embodiment will be described. Fig. 6 is a flowchart illustrating an image processing method using the image processing device 100 according to the first embodiment. As shown in Fig. 6, in step S10, a captured image G10 is acquired. Specifically, the captured image acquisition unit 10 is caused to acquire a captured image G10 of a sample 50 including a pattern area PA in which a pattern PT having a first portion 51 and a second portion 52 with mutually different reflectances is formed.

[0055] Next, in step S11, a first spatial frequency distribution G11 is acquired. Specifically, the captured image G10 is Fourier transformed and the first acquisition unit 11 acquires the first spatial frequency distribution G11.

[0056] Next, in step S12, a second spatial frequency distribution G12 is acquired. Specifically, a filter that removes components other than the frequency components in the pattern region PT is applied to the first spatial frequency distribution G11, and the second acquisition unit 12 acquires the second spatial frequency distribution G12 after removing the components other than the frequency components.

[0057] Next, in step S13, predetermined information processing is performed. Specifically, the predetermined information processing is performed on the second spatial frequency distribution G12, causing the information processing unit 13 to acquire an information processing result G13. For example, the information processing unit 13 may acquire a converted image G13a as the information processing result G13, or may acquire an arithmetic result. Alternatively, the information processing unit 13 may acquire a modulated image as the information processing result G13.

[0058] Next, in step S14, the captured image G10 is evaluated. Specifically, the evaluation unit 14 is caused to evaluate the contrast between the first portion 51 and the second portion 52 of the pattern PT in the captured image G10 based on the information processing result G13. The evaluation unit 14 may be caused to evaluate a parameter based on the luminance of the first portion 51 and the second portion 52 in the converted image G13a and the arithmetic result. Alternatively, the evaluation unit 14 may be caused to evaluate a parameter based on the luminance of the first portion 51 and the second portion 52 in the modulated image.

[0059] The image processing device 100 may include an information processing device such as a personal computer or a server. FIG. 7 is a block diagram illustrating the image processing device 100 according to the first embodiment. As shown in FIG. 7, the image processing device 100 may further include a processor PRC, a memory MMR, a storage device STR, and a user interface UI. The storage device STR stores programs that represent processes to be executed by each component of the image processing device 100. The processor PRC loads the programs from the storage device STR into the memory MMR and executes the programs. As a result, the processor PRC realizes the functions of each component of the image processing device 100, such as the captured image acquisition unit 10, the first acquisition unit 11, the second acquisition unit 12, the information processing unit 13, and the evaluation unit 14. The user interface UI may include input devices such as a keyboard, a mouse, and an image capture device, and output devices such as a display, a printer, and a speaker.

[0060] Each component of the image processing device 100 may be realized by dedicated hardware. Furthermore, some or all of the components may be realized by general-purpose or dedicated circuits, processor PRCs, etc., or a combination of these. These may be configured by a single chip, or by multiple chips connected via a bus. Some or all of the components may be realized by a combination of the above-mentioned circuits, processor PRCs, etc., and programs. A CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field-Programmable Gate Array), a quantum processor (quantum computer control chip), etc., may be used as the processor PRC.

[0061] Furthermore, when some or all of the components of the image processing device 100 are realized by a plurality of image processing devices 100, circuits, etc., the plurality of image processing devices 100, circuits, etc. may be centrally or decentralized. For example, the image processing devices 100, circuits, etc. may be realized in a form in which they are connected to each other via a communication network by a client-server system, a cloud computing system, etc. Furthermore, the functions of the image processing device 100 may be provided in a SaaS (Software as a Service) format.

[0062] <Modification> Next, a modified example of embodiment 1 will be described. Fig. 8 is a block diagram illustrating an image processing device 101 according to a modified example of embodiment 1. As shown in Fig. 8, the image processing device 101 further includes a setting unit 15 and an inspection unit 16.

[0063] The setting unit 15 sets a plurality of imaging conditions for the same pattern area PA. The imaging conditions include, for example, the relative position of the objective lens with respect to the pattern area PA of the sample 50. By setting a plurality of imaging conditions, the setting unit 15 causes the captured image acquisition unit 10 to acquire a plurality of captured images G10 captured under the plurality of imaging conditions.

[0064] The captured image acquisition unit 10 acquires multiple captured images G10 captured under multiple imaging conditions for the same pattern area PA. The first acquisition unit 11 may perform a Fourier transform on each of the multiple captured images G10 to acquire a first spatial frequency distribution G11 for the multiple captured images G10. The second acquisition unit 12 may apply a filter to each of the multiple first spatial frequency distributions G11, which filter removes components other than frequency components in the pattern area PA, to acquire a second spatial frequency distribution G12 for the multiple captured images G10 after removing the components other than frequency components. The information processing unit 13 may perform predetermined information processing on each of the multiple second spatial frequency distributions G12 to acquire information processing results G13 for the multiple captured images G10. The evaluation unit 14 may evaluate the multiple captured images G10 based on the multiple information processing results G13.

[0065] Furthermore, the setting unit 15 selects an image G10 captured under imaging conditions having a predetermined contrast from among the multiple captured images G10 evaluated by the evaluation unit 14. The inspection unit 16 inspects the sample 50 for defects based on the image G10 captured under imaging conditions having a predetermined contrast from among the multiple captured images G10 evaluated by the evaluation unit 14. In this way, since the inspection is performed based on the image G10 captured under imaging conditions having a predetermined contrast, which is selected from among the multiple captured images G10 captured under multiple imaging conditions, the sample 50 can be inspected more preferably. Note that this inspection may be performed by a known process such as comparing the captured image G10 with a reference image or performing die-to-die comparison on the captured image G10.

[0066] 9 is a flowchart illustrating an image processing method using the image processing device 101 according to a modification of the first embodiment. As shown in FIG. 9, in this modification, steps S10a to S10c are added between steps S10 and S11, compared to the image processing method described above. In addition, steps S15 to S18 are added after step S14.

[0067] Steps S10 to S10b are phases for acquiring captured images G10 under a plurality of imaging conditions. For example, for a point at a specific XY coordinate, captured images G10 are acquired while changing the relative position in the Z-axis direction within a predetermined range.

[0068] Step S10c and steps S11 to S16 are phases for identifying an image G10 with good contrast (such an imaging condition) from images G10 captured under a plurality of imaging conditions. An image G10 with good focus is identified from images G10 captured at various relative positions in the Z-axis direction. Note that, even if images G10 captured under all imaging conditions are evaluated, if none of them are good enough to exceed a criterion such as a threshold, the image G10 with the best evaluation among them may be selected, or a message to that effect may be displayed to the user and the process may end. Here, steps S10 to S14 are the same as the flowchart in the first embodiment described above.

[0069] Steps S17 and S18 are phases in which an inspection is performed using the captured image G10 with good contrast.

[0070] After acquiring the captured image G10 in step S10, it is determined in step S10a whether acquisition of the captured image G10 under a plurality of predetermined imaging conditions has been completed. Specifically, it is determined whether the captured image acquisition unit 10 has acquired a plurality of captured images G10 captured under a plurality of imaging conditions for the same pattern area PA. If acquisition of the captured image G10 under a plurality of imaging conditions has not been completed (NO), the process proceeds to step S10b. If acquisition of the captured image G10 under a plurality of imaging conditions has been completed (YES), the process proceeds to step S10c.

[0071] In step S10b, the imaging conditions are changed. Specifically, for example, the relative position of the objective lens with respect to the pattern area PA of the sample 50 is changed. Then, the process returns to step S10, and steps S10 to S10a are repeated.

[0072] In step S10c, the captured image G10 to be evaluated is read out. That is, the captured image G10 to be evaluated is changed. Specifically, the captured image G10 is changed in order to evaluate the captured image G10 under different imaging conditions from the previous one. Steps S11 to S14 are the same as those described above.

[0073] Next, in step S15, it is determined whether to inspect. Specifically, it is determined whether the captured image G10 to be evaluated has obtained a predetermined evaluation suitable for inspection, and if not, it is determined whether to select the captured image G10 to be inspected. For example, the evaluation unit 14 may determine whether the captured image G10 has obtained a predetermined evaluation, or the setting unit 15 may determine whether the captured image G10 has obtained a predetermined evaluation. If the captured image G10 has obtained a predetermined evaluation (if YES), the process proceeds to step S17. If the captured image G10 has not obtained a predetermined evaluation (if NO), the process proceeds to step S16.

[0074] Furthermore, in step S15, if none of the captured images G10 under all imaging conditions (for example, the captured image G10 with the last flag) have received a predetermined evaluation and none of them are good enough to exceed a criterion such as a threshold, the captured image G10 with the best evaluation among them may be selected. If a selection is to be made (YES), the process proceeds to step S17. If a selection is not to be made (NO), the process proceeds to step S16.

[0075] In step S16, it is determined whether to end the process. For example, if the process does not end because the last flagged captured image G10 remains unevaluated (NO), the process returns to step S10c. On the other hand, if the process is to end (YES), the process ends. In this case, the process may end by displaying to the user that none of the captured images exceeded a threshold or other criterion.

[0076] In step S17, a captured image G10 is selected. For example, if there is a captured image G10 for which a predetermined evaluation has been obtained, the setting unit 15 is made to select that captured image G10. On the other hand, if there is no captured image G10 for which a predetermined evaluation has been obtained, the setting unit 15 is made to select the captured image G10 with the best evaluation from among the multiple captured images G10 captured under multiple imaging conditions. Specifically, the setting unit 15 is made to select the captured image G10 under the imaging conditions with the best contrast from among the multiple captured images G10 evaluated by the evaluation unit 14.

[0077] Next, in step S18, the sample 50 is inspected. Specifically, the inspection unit 16 is caused to inspect defects in the sample 50 using an image G10 captured under imaging conditions having a predetermined contrast, among the multiple captured images G10 evaluated by the evaluation unit 14. Then, the process ends.

[0078] Next, the effects of this embodiment will be described. In the image processing device 100 of this embodiment, the information processing unit 13 performs predetermined information processing on the second spatial frequency distribution G12 after removing components other than the frequency components in the pattern area PA, thereby acquiring an information processing result G13. Then, the evaluation unit 14 evaluates the contrast between the first portion 51 and the second portion 52 of the pattern PT in the captured image G10 based on the information processing result G13 acquired by the information processing unit 13. This makes it possible to simply and accurately evaluate whether the contrast of the pattern PT is good or bad.

[0079] The information processing unit 13 may obtain, as the information processing result G13, a converted image G13a obtained by performing an inverse Fourier transform on the second spatial frequency distribution G12. As a result, the evaluation unit 14 evaluates a value corresponding to the gradient of luminance in the converted image G13a using a differential filter or the like, and therefore, it is possible to simply and accurately evaluate the quality of the contrast between the first portion 51 and the second portion 52.

[0080] Furthermore, the information processing unit 13 may acquire an arithmetic result as the information processing result G13 by performing arithmetic on the second spatial frequency distribution G12, the arithmetic result including an equation corresponding to a differential filter. This enables the evaluation unit 14 to evaluate a value corresponding to the slope in the spatial frequency domain G12, and to simply and accurately evaluate the quality of the contrast between the first portion 51 and the second portion 52.

[0081] Furthermore, the information processing unit 13 may acquire a modulated image as the information processing result G13. By reducing the overall luminance in the modulated image, components other than frequency components are reduced compared to the frequency components, allowing the evaluation unit 14 to simply and accurately evaluate the quality of the contrast between the first portion 51 and the second portion 52.

[0082] Among a plurality of captured images G10 captured under a plurality of imaging conditions for the same pattern area PA, an imaging condition having a predetermined contrast is selected. In other words, a captured image G10 having a good contrast suitable for evaluation is selected. Then, defects in the sample 50 are inspected using the selected captured image G10. This improves inspection accuracy.

[0083] <Embodiment 2> Next, an image processing device 200 according to the second embodiment will be described. Fig. 10 is a block diagram illustrating the image processing device 200 according to the second embodiment. As shown in Fig. 10, the image processing device 200 according to this embodiment further includes a determination unit 17 in addition to a captured image acquisition unit 10, a first acquisition unit 11, a second acquisition unit 12, an information processing unit 13, and an evaluation unit 14. The operations of the captured image acquisition unit 10, the first acquisition unit 11, and the evaluation unit 14 are the same as those in the first embodiment described above.

[0084] The determination unit 17 determines whether the pattern PT in the pattern area PA of the sample 50 includes a specific pattern. As described above, the specific pattern includes a pattern PT in which a first portion 51 and a second portion 52 are formed under a predetermined repetition condition in a predetermined direction.

[0085] When the pattern PT includes a specific pattern, the second acquisition unit 12 applies a filter to the first spatial frequency distribution G11 that removes frequency components other than those in the pattern area PA, and acquires a second spatial frequency distribution G12.

[0086] On the other hand, when the pattern PT does not include a specific pattern, the information processing section 13 acquires a modulated image that has been subjected to modulation processing that reduces the overall intensity in the first spatial frequency distribution G11.

[0087] The information processing unit 13 acquires an information processing result G13 by performing predetermined information processing on the second spatial frequency distribution G12 acquired by the second acquisition unit 12 or the modulated image acquired by the information processing unit 13. Specifically, the information processing unit 13 may acquire, as the information processing result G13, a transformed image G13a obtained by performing an inverse Fourier transform on the second spatial frequency distribution G12. Furthermore, the information processing unit 13 may acquire, as the information processing result G13, an arithmetic result by performing arithmetic on the second spatial frequency distribution G12 including an equation corresponding to a differential filter.

[0088] In this way, when the determination unit 17 determines that the pattern PT includes a specific pattern, the second acquisition unit 12 and the information processing unit 13 perform the same operations as in embodiment 1. On the other hand, when the determination unit 17 determines that the pattern PT does not include a specific pattern, the information processing unit 13 acquires a modulated image obtained by modulating the first spatial frequency distribution G11.

[0089] Next, an image processing method will be described. Fig. 11 is a flowchart illustrating an image processing method using the image processing device 200 according to the second embodiment. As shown in Fig. 11, steps S20, S21, and S26 are the same as steps S10, S11, and S14 in the image processing method according to the first embodiment.

[0090] Next, in step S22, it is determined whether the pattern PT of the sample 50 includes a specific pattern. Specifically, the determination unit 17 is caused to determine whether the pattern PT includes a specific pattern in which a first portion 51 and a second portion 52 are formed under specific repetition conditions in a specific direction. Here, the determination by the determination unit 17 may be made based on the intensity of the frequency component corresponding to the specific pattern in the first spatial frequency distribution G11, or may be made based on the identification information of the sample 50 having the pattern PT. In step S22, if the pattern PT includes the specific pattern (YES), the process proceeds to step S23. In step S22, if the pattern PT does not include the specific pattern (NO), the process proceeds to step S24.

[0091] In step S23, a second spatial frequency distribution G12 is acquired. Specifically, when the pattern PT includes a specific pattern, a filter that removes components other than the frequency components in the pattern area PA is applied to the first spatial frequency distribution G11, and the second acquisition unit 12 acquires the second spatial frequency distribution G12 after removing the components other than the frequency components. Then, the process proceeds to step S25.

[0092] In step S24, a modulated image is acquired. Specifically, when the pattern PT does not include a specific pattern, the information processing unit 13 is caused to acquire a modulated image that has been subjected to modulation processing to reduce the overall intensity in the first spatial frequency distribution G11. Then, the process proceeds to step S25.

[0093] In step S25, predetermined information processing is performed. Specifically, the predetermined information processing is performed on the second spatial frequency distribution G12 or the modulation image, causing the information processing unit 13 to acquire an information processing result G13. The predetermined information processing may include a transformed image G13a obtained by inverse Fourier transform, or may include an arithmetic result.

[0094] <Modification> Next, a modified example of the second embodiment will be described. Fig. 12 is a block diagram illustrating an image processing device 201 according to the modified example of the second embodiment. As shown in Fig. 12, the image processing device 201 further includes a setting unit 15 and an inspection unit 16. The functions of the setting unit 15 and the inspection unit 16 are similar to those of the modified example of the first embodiment.

[0095] Next, an information processing method according to a modification of the second embodiment will be described. FIG. 13 is a flowchart illustrating an image processing method using an image processing device 201 according to a modification of the second embodiment. As shown in FIG. 13, step S20 and steps S21 to S26 are similar to the image processing method according to the second embodiment. In this modification, steps S20a to S20c are added between steps S20 and S21. Furthermore, steps S27 to S30 are added after step S26. Steps S20a to S20c and steps S27 to S30 are similar to steps S10a to S10c and steps S15 to S18, respectively, in the modification of the first embodiment.

[0096] Next, the effects of this embodiment will be described. In the image processing device 201 of this embodiment, the determination unit 17 determines whether the pattern PT includes a specific pattern. If the specific pattern is included, the determination unit 17 performs the same processing as in the first embodiment to evaluate the contrast between the first portion 51 and the second portion 52 of the pattern PT in the captured image G10. On the other hand, if the specific pattern is not included, the determination unit 17 performs modulation processing and evaluates the contrast between the first portion 51 and the second portion 52 of the pattern PT in the captured image G10 based on the information processing result G13 for the modulation image. Therefore, information processing effective for the specific pattern can be performed on the specific pattern, so that the quality of the pattern contrast can be efficiently determined. Other configurations and effects are included in the description of the first embodiment.

[0097] <Embodiment 3> Next, an optical device according to a third embodiment will be described. The optical device of this embodiment includes any one of the image processing devices 100, 101, 200, and 201 described above. In the following, the optical device will be described as including the image processing device 100. The optical device is, for example, an inspection device for a mask used in a semiconductor manufacturing process. The optical device may also be a review device. FIG. 14 is a configuration diagram illustrating an optical device 1 according to the third embodiment. As shown in FIG. 14, the optical device 1 includes an image processing device 100, an optical system 20, and a detector 30.

[0098] The optical system 20 illuminates the sample 50 with illumination light L1 and collects detection light R1 from the illuminated sample 50. For example, the optical system 20 includes a separating means 21, an objective lens 22, and a collecting lens 23. Note that the optical system 20 may include optical elements such as a drop mirror, a concave mirror, and a reflecting mirror, as long as it can illuminate the sample 50 with illumination light L1 and collect detection light R1 from the illuminated sample 50. The optical system 20 may also include other optical elements, such as a scanning means.

[0099] The optical system 20 may include a light source LS, or may introduce illumination light L1 from a light source LS separate from the optical device 1. The illumination light L1 may include white light, or may include light having a predetermined center wavelength, such as infrared light, ultraviolet light, or EUV (Extreme Ultraviolet) light. The sample 50 is placed on a stage 55. Here, for convenience of explanation of the optical device 1, an αβγ Cartesian coordinate system is introduced. The upper surface of the stage 55 is defined as the αβ plane, and the direction perpendicular to the upper surface of the sample 50 is defined as the γ axis direction. The α axis and the β axis may correspond to the X axis and the Y axis in the captured image G10.

[0100] In the following description, the optical system 20 is assumed to include a separating means 21, an objective lens 22, and a condenser lens 23. Illumination light L1 generated from a light source LS is incident on a separating means 21 such as a half mirror. The separating means 21 transmits part of the incident illumination light L1 and reflects part of it. The illumination light L1 reflected by the separating means 21 is incident on an objective lens 22. The objective lens 22 focuses the incident illumination light L1 on a sample 50. The illumination light L1 focused by the objective lens 22 illuminates the sample 50. Detection light R1 is emitted from the sample 50 illuminated by the illumination light L1.

[0101] The detected light R1 may include reflected light, scattered light, fluorescence, and luminescence. The reflected light includes light that is the illumination light L1 reflected by the sample 50. The scattered light includes light that is the illumination light L1 scattered by the sample 50. The fluorescence includes fluorescence from the sample 50 excited by the illumination light L1. The luminescence includes luminescence from the sample 50 excited by the illumination light L1. The sample 50 may contain defects. Therefore, the detected light R1 includes information about the defects contained in the sample 50.

[0102] The detection light R1 is incident on the objective lens 22. The objective lens 22 collects and transmits the detection light R1. The detection light R1 that has passed through the objective lens 22 is incident on the separation means 21. The separation means 21 transmits part of the incident detection light R1 and reflects part of it. The detection light R1 that has passed through the separation means 21 is incident on the condenser lens 23. The condenser lens 23 collects the incident detection light R1 onto the detector 30.

[0103] The detector 30 detects the detection light R1. The detector 30 may be, for example, a camera using TDI. The detector 30 outputs the detected detection result to the image processing device 100. The detector 30 may output the detected detection result to a storage device (not shown). The detector 30 may also acquire the detection result from the storage device.

[0104] Next, a method of using the optical device 1 will be described. Fig. 15 is a flow chart illustrating a method of using the optical device 1 according to the first embodiment. As shown in Fig. 15, in step S31, detection light R1 from the sample 50 is collected. Specifically, the sample 50 is illuminated with illumination light L1, and the detection light R1 from the illuminated sample 50 is collected by the optical system 20. Next, in step S32, the detection light R1 is detected by the detector 30. Next, in step S33, the image processing device 100 performs the image processing described above.

[0105] According to this embodiment, the optical device 1 can process the detected results using the image processing device 100, so it is possible to simply and accurately evaluate the quality of the contrast of the pattern PT. Other configurations and effects are included in the descriptions of the first and second embodiments and each modified example.

[0106] Although the embodiments of the present disclosure have been described above, the present disclosure includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited to the above-described embodiments. Furthermore, the configurations of the first and second embodiments and the modifications may be combined as appropriate. The following image processing program for causing a computer to execute the above-described image processing method is also within the scope of the technical concept of the present disclosure.

[0107] (Appendix 1) causing an image acquisition unit to acquire an image of the sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; performing a Fourier transform on the captured image to cause a first acquisition unit to acquire a first spatial frequency distribution; applying a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components; performing predetermined information processing on the second spatial frequency distribution, thereby causing an information processing unit to acquire an information processing result; causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the captured image based on the information processing result; An image processing program that causes a computer to perform the following: (Appendix 2) When the information processing unit acquires the information processing result, obtaining a transformed image by performing an inverse Fourier transform on the second spatial frequency distribution as a result of the information processing; When the evaluation is performed, evaluating a parameter based on the luminance of the first portion and the second portion in the transformed image; 2. The image processing program according to claim 1, which causes a computer to execute the steps of: (Appendix 3) When the information processing unit acquires the information processing result, obtaining an arithmetic result as the information processing result by performing arithmetic on the second spatial frequency distribution including an equation corresponding to a differential filter; When the evaluation is performed, evaluating a parameter based on the luminance of the first portion and the second portion of the arithmetic result; 1. An image processing program according to claim 1. (Appendix 4) the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; 4. The image processing program according to claim 2 or 3. (Appendix 5) When the information processing unit acquires the information processing result, obtaining, as a result of the information processing, a modulated image that has been subjected to modulation processing to reduce the overall intensity in the second spatial frequency distribution; When the evaluation is performed evaluating a parameter based on the intensities of the first and second portions of the modulation image; 1. An image processing program according to claim 1. (Appendix 6) causing an image acquisition unit to acquire an image of the sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; performing a Fourier transform on the captured image to cause a first acquisition unit to acquire a first spatial frequency distribution; causing a determination unit to determine whether the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; when the pattern includes the specific pattern, applying a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components; When the pattern does not include the specific pattern, an information processing unit acquires a modulated image that has been subjected to modulation processing to reduce the overall intensity in the first spatial frequency distribution; performing predetermined information processing on the second spatial frequency distribution or the modulation image, thereby causing the information processing unit to acquire an information processing result; causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the captured image based on a result of the information processing. An image processing program that causes a computer to perform the following: (Appendix 7) When the information processing unit acquires the information processing result, obtaining a transformed image by performing an inverse Fourier transform on the second spatial frequency distribution as a result of the information processing; When the evaluation is performed, evaluating a parameter based on the luminance of the first portion and the second portion in the transformed image; 7. The image processing program according to claim 6. (Appendix 8) When the information processing unit acquires the information processing result, obtaining an arithmetic result as the information processing result by performing arithmetic on the second spatial frequency distribution including an equation corresponding to a differential filter; When the evaluation is performed, evaluating a parameter based on the luminance of the first portion and the second portion of the arithmetic result; 7. The image processing program according to claim 6. (Appendix 9) further causing the computer to set a plurality of imaging conditions for the same pattern region in a setting unit; When the captured image acquisition unit acquires the captured image, causing the captured image acquisition unit to acquire a plurality of captured images captured under a plurality of imaging conditions for the same pattern region; When the first acquisition unit acquires the first spatial frequency distribution, causing the first acquisition unit to acquire the first spatial frequency distribution for the plurality of captured images; When the second acquisition unit acquires the second spatial frequency distribution, causing the second acquisition unit to acquire the second spatial frequency distribution for the plurality of captured images; When the information processing result is acquired by the information processing unit, causing the information processing unit to acquire information processing results for the plurality of captured images; When the evaluation is performed, causing the evaluation unit to evaluate the plurality of captured images based on the plurality of information processing results; 6. An image processing program according to claim 1 or 5. (Appendix 10) 10. An image processing program according to claim 9, further comprising causing a computer to have an inspection unit inspect defects in the sample based on an image captured under the imaging conditions having a predetermined contrast among the plurality of captured images evaluated by the evaluation unit. [Explanation of symbols]

[0108] 1 Optical device 10. Image acquisition unit 11 First acquisition part 12 Second acquisition part 13 Information Processing Department 14 Evaluation Section 15 Setting section 16 Inspection Department 17 Judgment section 20 Optical system 21 Separation means 22 Objective Lens 23 Condenser lens 30 detectors 50 samples 51 Part 1 52 Part 2 55 Stages 100, 101, 200, 201 Image processing device G10 Captured image G11 1st spatial frequency distribution G12 2nd spatial frequency distribution G13 Information Processing Results G13a converted image PA Pattern Area PT Pattern L1 illumination light LS light source MMR Memory PRC Processor R1 Detected light STR storage UI User Interface

Claims

1. an image acquisition unit that acquires an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; a first acquisition unit that performs a Fourier transform on the captured image to acquire a first spatial frequency distribution; a second acquisition unit that applies a filter that removes components other than frequency components in the pattern region to the first spatial frequency distribution, and acquires a second spatial frequency distribution after removing the components other than the frequency components; an information processing unit that performs predetermined information processing on the second spatial frequency distribution to obtain an information processing result; an evaluation unit that evaluates the captured image based on the information processing result; Equipped with the evaluation unit evaluates contrast between the first portion and the second portion of the pattern in the captured image. Image processing device.

2. the information processing unit obtains, as a result of the information processing, a transformed image obtained by performing an inverse Fourier transform on the second spatial frequency distribution; the evaluation unit evaluates a parameter based on luminance of the first portion and the second portion in the converted image. The image processing device according to claim 1 .

3. the information processing unit obtains, as the information processing result, an arithmetic result by performing arithmetic on the second spatial frequency distribution including an equation corresponding to a differential filter; the evaluation unit evaluates a parameter based on the luminance of the first portion and the second portion in the arithmetic result. The image processing device according to claim 1 .

4. the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; 4. The image processing device according to claim 2 or 3.

5. the information processing unit acquires, as a result of the information processing, a modulated image that has been subjected to modulation processing to reduce an overall intensity in the second spatial frequency distribution; the evaluation unit evaluates a parameter based on luminance of the first portion and the second portion in the modulation image. The image processing device according to claim 1 .

6. an image acquisition unit that acquires an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; a first acquisition unit that performs a Fourier transform on the captured image to acquire a first spatial frequency distribution; a determination unit that determines whether the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; a second acquisition unit that, when the pattern includes the specific pattern, applies a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and acquires a second spatial frequency distribution after removing the components other than the frequency components; an information processing unit that acquires a modulated image that has been subjected to modulation processing to reduce an overall intensity in the first spatial frequency distribution when the pattern does not include the specific pattern; an evaluation unit for evaluating the captured image; Equipped with the information processing unit performs predetermined information processing on the second spatial frequency distribution or the modulated image to obtain an information processing result; the evaluation unit evaluates the contrast between the first portion and the second portion of the pattern in the captured image based on the information processing result. Image processing device.

7. the information processing unit obtains, as a result of the information processing, a transformed image obtained by performing an inverse Fourier transform on the second spatial frequency distribution; the evaluation unit evaluates a parameter based on luminance of the first portion and the second portion in the converted image. The image processing device according to claim 6 .

8. the information processing unit obtains, as the information processing result, an arithmetic result by performing arithmetic on the second spatial frequency distribution including an equation corresponding to a differential filter; the evaluation unit evaluates a parameter based on the luminance of the first portion and the second portion in the arithmetic result. The image processing device according to claim 6 .

9. a setting unit for setting a plurality of imaging conditions for the same pattern area; the captured image acquisition unit acquires a plurality of captured images captured under a plurality of imaging conditions for the same pattern region, the first acquisition unit acquires the first spatial frequency distribution for the plurality of captured images; the second acquisition unit acquires the second spatial frequency distribution for the plurality of captured images; the information processing unit acquires the information processing results for the plurality of captured images, the evaluation unit evaluates the plurality of captured images based on the plurality of information processing results. The image processing device according to claim 1 or 6.

10. an inspection unit that inspects the sample for defects based on the captured image under the imaging conditions having a predetermined contrast among the plurality of captured images evaluated by the evaluation unit; The image processing device according to claim 9 .

11. causing an image acquisition unit to acquire an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; a step of causing a first acquisition unit to acquire a first spatial frequency distribution by performing a Fourier transform on the captured image; applying a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components; a step of causing an information processing unit to acquire a result of information processing by performing predetermined information processing on the second spatial frequency distribution; causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the captured image based on the information processing result; An image processing method comprising:

12. In the step of causing the information processing unit to acquire the information processing result, obtaining a transformed image by performing an inverse Fourier transform on the second spatial frequency distribution as a result of the information processing; In the step of evaluating, evaluating a parameter based on the luminance of the first portion and the second portion in the transformed image; The image processing method according to claim 11.

13. In the step of causing the information processing unit to acquire the information processing result, obtaining an arithmetic result as the information processing result by performing arithmetic on the second spatial frequency distribution including an equation corresponding to a differential filter; In the step of evaluating, evaluating a parameter based on the luminance of the first portion and the second portion of the arithmetic result; The image processing method according to claim 11.

14. the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; 14. The image processing method according to claim 12 or 13.

15. In the step of causing the information processing unit to acquire the information processing result, obtaining, as a result of the information processing, a modulated image that has been subjected to modulation processing to reduce the overall intensity in the second spatial frequency distribution; In the step of evaluating, evaluating a parameter based on the luminance of the first portion and the second portion of the modulation image; The image processing method according to claim 11.

16. causing an image acquisition unit to acquire an image of a sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; a step of causing a first acquisition unit to acquire a first spatial frequency distribution by performing a Fourier transform on the captured image; causing a determination unit to determine whether the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; When the pattern includes the specific pattern, applying a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern area, and causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components; When the pattern does not include the specific pattern, an information processing unit acquires a modulated image that has been subjected to modulation processing to reduce the overall intensity in the first spatial frequency distribution; a step of causing the information processing unit to acquire a result of information processing by performing predetermined information processing on the second spatial frequency distribution or the modulation image; causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the captured image based on a result of the information processing; An image processing method comprising:

17. In the step of causing the information processing unit to acquire the information processing result, obtaining a transformed image by performing an inverse Fourier transform on the second spatial frequency distribution as a result of the information processing; In the step of evaluating, evaluating a parameter based on the luminance of the first portion and the second portion in the transformed image; The image processing method according to claim 16.

18. In the step of causing the information processing unit to acquire the information processing result, obtaining an arithmetic result as the information processing result by performing arithmetic on the second spatial frequency distribution including an equation corresponding to a differential filter; In the step of evaluating, evaluating a parameter based on the luminance of the first portion and the second portion of the arithmetic result; The image processing method according to claim 16.

19. a step of causing a setting unit to set a plurality of imaging conditions for the same pattern area; In the step of causing the captured image acquisition unit to acquire the captured image, causing the captured image acquisition unit to acquire a plurality of captured images captured under a plurality of imaging conditions for the same pattern region; In the step of causing a first acquisition unit to acquire the first spatial frequency distribution, causing the first acquisition unit to acquire the first spatial frequency distribution for the plurality of captured images; In the step of causing a second acquisition unit to acquire the second spatial frequency distribution, causing the second acquisition unit to acquire the second spatial frequency distribution for the plurality of captured images; In the step of causing an information processing unit to acquire the information processing result, causing the information processing unit to acquire information processing results for the plurality of captured images; In the step of evaluating, causing the evaluation unit to evaluate the plurality of captured images based on the plurality of information processing results; 17. The image processing method according to claim 11 or 16.

20. The method further includes a step of causing an inspection unit to inspect defects of the sample based on an image captured under the imaging conditions having a predetermined contrast among the plurality of captured images evaluated by the evaluation unit.

20. The image processing method according to claim 19.

21. an optical system that illuminates a sample with illumination light and collects detection light from the illuminated sample; a detector that detects the detection light; an image processing device according to claim 1 or 6; An optical device comprising:

22. illuminating a sample with illumination light and collecting detection light from the illuminated sample with an optical system; detecting the detection light with a detector; performing an image processing method according to claim 11 or 16; A method of using an optical device comprising the steps of:

23. causing an image acquisition unit to acquire an image of the sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; performing a Fourier transform on the captured image to cause a first acquisition unit to acquire a first spatial frequency distribution; applying a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components; performing predetermined information processing on the second spatial frequency distribution, thereby causing an information processing unit to acquire an information processing result; causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the captured image based on the information processing result; An image processing program that causes a computer to perform the following:

24. causing an image acquisition unit to acquire an image of the sample including a pattern region in which a pattern having a first portion and a second portion with mutually different reflectances is formed; performing a Fourier transform on the captured image to cause a first acquisition unit to acquire a first spatial frequency distribution; causing a determination unit to determine whether the pattern includes a specific pattern in which the first portion and the second portion are formed under predetermined repetition conditions in a predetermined direction; when the pattern includes the specific pattern, applying a filter to the first spatial frequency distribution that removes components other than frequency components in the pattern region, and causing a second acquisition unit to acquire a second spatial frequency distribution after removing the components other than the frequency components; When the pattern does not include the specific pattern, an information processing unit acquires a modulated image that has been subjected to modulation processing to reduce the overall intensity in the first spatial frequency distribution; performing predetermined information processing on the second spatial frequency distribution or the modulation image, thereby causing the information processing unit to acquire an information processing result; causing an evaluation unit to evaluate the contrast between the first portion and the second portion of the pattern in the captured image based on a result of the information processing; An image processing program that causes a computer to perform the following:

Images