Inspection device, method and program

Abstract

To provide an inspection device that can reduce false detection.SOLUTION: An inspection device according to one embodiment includes a design image acquisition unit, a captured image acquisition unit, and an image processing unit. The design image acquisition unit acquires a design image based on design data created by design software. A captured image acquisition unit acquires a captured image of an inspection target created based on the design data. The image processing unit generates a corrected reference image obtained by correcting a positional deviation caused by a deviation between a center position and a centroid position of an image conversion filter used for creating a reference image from a design image, or a processed captured image processed to include the positional deviation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to an inspection apparatus, a method, and a program. [Background technology]

[0002] In the manufacture of large-scale integrated circuits such as semiconductor devices, inspecting masks (photomasks), which are the masters on which circuit patterns are formed, for defects is important in preventing yield declines. Die-to-Database inspection is one of the photomask inspection methods. Die-to-Database inspection compares a captured image of the circuit pattern on the created photomask with a reference image, which is a virtual image generated based on the circuit pattern in the photomask design data, and detects any large differences as defects in the photomask. This inspection is simple in principle, requiring only a simple comparison of two images, and is therefore implemented in a variety of inspection devices.

[0003] In die-to-database inspection, it is important to generate a reference image from the photomask design data so that it can faithfully reproduce the captured image of a photomask without any defects. This is because it is impossible to distinguish whether the difference between the two images is due to defects being introduced during photomask production or to poor reproducibility of the reference image, and if it is the latter, there is a high possibility of false defect detection.

[0004] One known method for generating a reference image is to create a binary image based on the presence or absence of a circuit pattern from design data, and then convolve the binary image with a point spread function (PSF) that is calculated by analogizing edge blur due to the optical characteristics of the imaging system from the edge pattern of the captured image to generate a reference image. In other words, the optical blur contained in the captured image is reproduced using a convolution operation, which is a linear operation. However, depending on the captured image, asymmetric distortion may occur between the rising and falling edges of the edge pattern due to the shooting environment or lens aberration, and a symmetric PSF cannot represent this asymmetric distortion.

[0005] Therefore, a technique is known that addresses asymmetric distortion of edge patterns in captured images by using an asymmetric two-dimensional PSF in which separate PSFs are calculated for the top, bottom, left, and right and then combined.

[0006] However, with this technology, the center of gravity of the conversion filter that represents the generated asymmetric PSF may shift from the center position, and the reference image generated from such a conversion filter will have a position shift across the entire image, which may increase the error between the reference image and the captured image and lead to an increase in false positives during inspection. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-197318 Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to provide an inspection device, method, and program that can reduce false detections. [Means for solving the problem]

[0009] An inspection apparatus according to one embodiment includes a design image acquisition unit, a captured image acquisition unit, and an image processing unit. The design image acquisition unit acquires a design image based on design data created by design software. The captured image acquisition unit acquires a captured image of an inspection target created based on the design data. The image processing unit generates a corrected reference image in which a positional deviation caused by a deviation between the center position and the center of gravity position of an image conversion filter used to create a reference image from the design image is corrected, or a processed captured image that has been processed to include the positional deviation. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram illustrating the configuration of an inspection apparatus according to a first embodiment. [Figure 2] FIG. 4 is an explanatory diagram for comparing line profiles of images according to the first embodiment. [Figure 3] 2 is a flowchart illustrating the operation of the inspection apparatus of FIG. 1. [Figure 4] 4 is a flowchart illustrating the reference image generation process of the flowchart in FIG. 3. [Figure 5] FIG. 10 is a block diagram illustrating the configuration of an inspection apparatus according to a second embodiment. [Figure 6] 6 is a flowchart illustrating a reference image generation process of the inspection apparatus of FIG. 5. [Figure 7] FIG. 10 is a block diagram illustrating the configuration of an inspection apparatus according to a third embodiment. [Figure 8] FIG. 11 is an explanatory diagram for comparing line profiles of images according to the third embodiment. [Figure 9] 8 is a flowchart illustrating the operation of the inspection apparatus of FIG. 7. [Figure 10] FIG. 1 is a block diagram illustrating a hardware configuration of a computer according to an embodiment. [Figure 11] FIG. 10 is an explanatory diagram comparing line profiles of images obtained by a conventional inspection device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the inspection device will be described in detail with reference to the drawings.

[0012] (First embodiment) 1 is a diagram showing an example of the configuration of an inspection device 100 according to the first embodiment. The inspection device 100 includes a design image acquisition unit 110, a captured image acquisition unit 120, an image processing unit 130, an error information generation unit 140, and a display control unit 150. The inspection device 100 is a device for inspecting an object to be inspected (e.g., a photomask) for defects.

[0013] The design image acquisition unit 110 acquires a design image based on design data created by design software, and outputs the acquired design image to the image processing unit .

[0014] Design software is software for computer design, such as CAD (Computer Aided Design). Design data for creating masks is created through processes such as functional design to realize the required functions, logical design to create circuit diagrams, and physical design to arrange elements and lay out wiring. The design data is also used to create the object to be inspected.

[0015] The design image is an image based on the pattern of the design data. Specifically, the design image is a binarized image according to the presence or absence of the pattern of the design data, similar to, for example, Die to Database inspection. Note that the design image is not limited to showing the structure of the inspection object, but may also show, for example, the material of the inspection object or may be given the color of the inspection object.

[0016] The captured image acquisition unit 120 acquires a captured image of an inspection object created based on design data. The captured image acquisition unit 120 outputs the acquired captured image to the image processing unit 130 and the error information generation unit 140.

[0017] The inspection object is, for example, a photomask created using an electron beam exposure device or the like based on design data. The captured image is acquired by photographing the inspection object using an imaging device such as an optical camera. The captured image is, for example, a grayscale image or a color image.

[0018] The imaging device may be an electron microscope, an X-ray camera, or a camera similar in principle to them. That is, the imaging device scans and irradiates light (electromagnetic waves) from a light source onto the inspection object, and converts the transmitted or reflected light (electromagnetic waves) into pixel values ​​depending on the intensity when it reaches a sensor, thereby creating an image of the inspection object. The light source may be, for example, a DUV (Deep Ultraviolet) laser. The sensor uses imaging elements arranged in a two-dimensional array, similar to a CMOS sensor. The light source and sensor are designed so that the wavelength of light and the arrangement of the sensor array can be appropriately determined depending on the fineness of the pattern of the inspection object.

[0019] The image processing unit 130 receives the design image from the design image acquisition unit 110 and receives the captured image from the captured image acquisition unit 120. The image processing unit 130 generates a corrected reference image in which the positional deviation caused by the deviation between the center position and the center of gravity position of the image conversion filter used when creating the reference image from the design image is corrected. The image processing unit 130 outputs the generated corrected reference image to the error information generation unit 140.

[0020] Specifically, the image processing unit 130 includes an image conversion filter calculation unit 131, a filter correction unit 132, and a reference image generation unit 133.

[0021] The image conversion filter calculation unit 131 calculates an image conversion filter based on the design image and the captured image. The image conversion filter is, for example, a rectangular filter. The image conversion filter calculation unit 131 outputs the calculated image conversion filter to the filter correction unit 132.

[0022] Specifically, the image conversion filter calculation unit 131 calculates the image conversion filter by, for example, transforming each of the design image and the captured image into the frequency domain using a fast Fourier transform, calculating an optical transfer function (OTF), and then returning it to the spatial domain. Alternatively, for example, the image conversion filter calculation unit 131 may calculate the image conversion filter by determining parameters of a preset conversion model through machine learning. A DNN (Deep Neural Network) may be used as the machine learning.

[0023] The image conversion filter is an asymmetric filter and includes a symmetric filter. The asymmetric filter is, for example, a filter in which the coefficients of the kernel are rotationally asymmetric. The asymmetric filter also includes a filter in which the center of gravity calculated based on the coefficients of the kernel is shifted from the center position of the kernel. The image conversion filter also includes one or more filters. That is, the image conversion filter may include multiple filters.

[0024] The filter correction unit 132 calculates a correction value based on the amount of deviation between the center position and the center of gravity position of the image conversion filter, and corrects the image conversion filter using the correction value to generate a corrected image conversion filter. The filter correction unit 132 outputs the generated corrected image conversion filter to the reference image generation unit 133.

[0025] Specifically, the filter correction unit 132 calculates the two-dimensional position of the image conversion filter as X={x, y} t Then, the center of gravity position G={x g ,y g} t is calculated using, for example, the following formula (1).

[0026]

number

[0027] In equation (1), f(X) represents the coefficient of the image conversion filter, and tapx indicates the number of taps in the x-direction of the PSF, and tap y indicates the number of taps in the y direction of the PSF.

[0028] The filter correction unit 132 calculates the center position C of the image conversion filter by using the c ,y c} t is calculated using, for example, the following formula (2).

[0029]

number

[0030] Below, calculation of correction values ​​when the image conversion filter has one filter and calculation of correction values ​​when the image conversion filter has a plurality of filters will be described.

[0031] When the image conversion filter has one filter, the filter correction unit 132 calculates the correction value D={x d ,y d} t is calculated using, for example, the following formula (3).

[0032]

number

[0033] According to equation (3), the correction value is calculated as the difference (difference value) between the center position and the center position of the image conversion filter. In this case, the deviation between the center position and the center position of the image conversion filter corresponds to the difference value.

[0034] When the image conversion filter has a plurality of filters (N>1, hereinafter also referred to as "N pieces"), the filter correction unit 132 calculates one correction value based on a plurality of deviation amounts (for example, difference values) calculated from the center position and center of gravity position of each of the plurality of filters. One correction value calculated from a plurality of difference values ​​includes, for example, six values: total value, average value, maximum value, minimum value, median value, and mode value. Hereinafter, one calculated correction value will be referred to as Dout Let's say.

[0035] When the correction value is a total value, the filter correction unit 132 calculates the correction value using, for example, the following equation (4).

[0036]

number

[0037] According to equation (4), the correction value is calculated as the sum of N difference values.

[0038] When the correction value is an average value, the filter correction unit 132 calculates the correction value using, for example, the following equation (5).

[0039]

number

[0040] According to equation (5), the correction value is calculated as the average of N difference values.

[0041] When the correction value is the maximum value, the filter correction unit 132 calculates the correction value using, for example, the following equation (6).

[0042]

number

[0043] In equation (6), max() is a function that extracts the maximum value among the N difference values. Therefore, in equation (6), the correction value is calculated as the maximum value among the N difference values. Note that, if the sign of each difference value is not taken into consideration, the filter correction unit 132 may calculate the maximum value among the absolute values ​​of the N difference values ​​as the correction value, for example, using the following equation (7).

[0044]

number

[0045] When the correction value is the minimum value, the filter correction unit 132 calculates the correction value using, for example, the following equation (8).

[0046]

number

[0047] In equation (8), min() is a function that extracts the minimum value among the N difference values. Therefore, in equation (8), the correction value is calculated as the minimum value among the N difference values. Note that, if the sign of each difference value is not taken into consideration, the filter correction unit 132 may calculate the minimum value among the absolute values ​​of the N difference values ​​as the correction value, for example, using the following equation (9).

[0048]

number

[0049] When the correction value is the median value, the filter correction unit 132 calculates the correction value using, for example, the following equation (10).

[0050]

number

[0051] In equation (10), median() is a function that extracts the median value of N difference values. Therefore, in equation (10), the correction value is calculated as the median value of N difference values.

[0052] When the correction value is the mode value, the filter correction unit 132 calculates the correction value using, for example, the following equation (11).

[0053]

number

[0054] In equation (11), mode() is a function that extracts the most frequent value among the N difference values. Therefore, in equation (11), the correction value is calculated as the most frequent value among the N difference values.

[0055] Furthermore, each of the multiple filters may have a weight. The weight set for the filter may be set in advance, or may be set by machine learning or the like according to the captured image. Furthermore, the weight set for each of the multiple filters may be set so that the sum of the respective weights is a predetermined number (for example, 1).

[0056] If the filters are weighted, the correction value is calculated based on the weight W of each filter. Below, as an example, calculation of the total value when the filters are weighted (weighted addition (weighted average)) will be described. The filter correction unit 132 performs the weighted addition using, for example, the following equation (12). It is assumed that the sum of the weights set for the multiple filters is 1.

[0057]

number

[0058] According to equation (12), the correction value is calculated as a weighted average of N difference values.

[0059] When calculating one correction value from a plurality of difference values, the same calculation method may be used for the x direction and the y direction, or different calculation methods may be used for each direction.

[0060] The filter correction unit 132 corrects the center of gravity position of the image conversion filter to the center position using the correction value calculated above. new ={x gn ,y gn} t is calculated using, for example, the following equation (13).

[0061]

number

[0062] The filter correction unit 132 calculates a new filter coefficient f new (x) is calculated using, for example, the following equation (14).

[0063]

number

[0064] As a result of the above, the filter correction unit 132 generates a corrected image conversion filter using the new center of gravity position and new filter coefficients.

[0065] In addition, when calculating new filter coefficients, if the correction value is a decimal, the filter correction unit 132 may calculate new filter coefficients using an interpolation filter. Examples of interpolation filters include nearest neighbor interpolation, bilinear interpolation, and bicubic interpolation. Furthermore, if a conversion model of the image conversion filter is available, the filter correction unit 132 may calculate, as new filter coefficients, filter coefficients shifted by the correction value based on the conversion model. Furthermore, the filter correction unit 132 may repeatedly correct the center of gravity position so that the correction value is equal to or less than a preset threshold.

[0066] The reference image generation unit 133 generates a corrected reference image based on the design image and the corrected image transformation filter. Specifically, the reference image generation unit 133 generates the corrected reference image by a convolution operation between the design image and the corrected image transformation filter. The reference image generation unit 133 outputs the generated corrected reference image to the error information generation unit 140. Note that the reference image generation unit 133 may generate the corrected reference image using not only the convolution operation but also a Fourier transform.

[0067] The corrected reference image is not limited to the design image, and may be generated using a differential image obtained by differentiating the design image, an enlarged image obtained by enlarging a portion of the design image, or an extracted image obtained by extracting only the color components of the design image. When a corrected image conversion filter having multiple filters is used, the processed image (e.g., the design image, the differential image, the enlarged image, and the extracted image) used to generate the corrected reference image may be associated in advance with one or more of the multiple filters. That is, the reference image generation unit 133 may generate a reference image using a filter according to the characteristics of the processed image.

[0068] Furthermore, for example, the reference image generating unit 133 may generate a composite reference image by synthesizing corrected reference images generated from a plurality of processed images respectively. The reference image generating unit 133 may select, by machine learning or the like, a combination of a processed image and a filter that reduces an error with respect to the captured image, and generate a corrected reference image based on the selected combination.

[0069] The error information generation unit 140 receives the captured image from the captured image acquisition unit 120 and receives the corrected reference image from the image processing unit 130. The error information generation unit 140 generates error information based on the captured image and the corrected reference image. The error information generation unit 140 outputs the generated error information to the display control unit 150.

[0070] Specifically, the error information generating unit 140 calculates the error by performing a difference process between the captured image and the corrected reference image. The difference process may be, for example, not only a simple difference but also a maximum error, a minimum error, a maximum absolute error, an average error, a mean squared error (MSE), or a root mean squared error (RMSE).

[0071] The error information generating unit 140 may also calculate the error based on circuit information associated with the design image. The circuit information includes, for example, information on the circuit area and other areas in the design image. The other areas are, for example, areas of solid patterns and areas required for manufacturing other than the area used as a product.

[0072] The error information generating unit 140 may output the error information to the image processing unit 130. For example, when selecting a combination of a processed image and a filter using machine learning, the image processing unit 130 may select an optimal combination by providing feedback using the error information.

[0073] The display control unit 150 receives error information from the error information generation unit 140. The display control unit 150 displays the test results based on the error information. The test results are displayed on a display device such as a liquid crystal display (LCD). This display device may be included in the inspection device 100. The display control unit 150 may transfer the test results via a network and display the test results on an external terminal (e.g., a tablet terminal). The display control unit 150 may also be called a test result generation unit because it generates the test results.

[0074] The inspection results can be displayed in five different formats: (1) a difference image, (2) an error display above a threshold, (3) a heat map, (4) a histogram, and (5) an enlarged display. The display control unit 150 displays at least one of these five display formats. Each display format will be described below.

[0075] (1) Difference image The display control unit 150 displays a difference image obtained from the difference between the captured image and the corrected reference image. The difference image may reflect the positive or negative value of the numerical value (pixel value) calculated for each pixel, or may reflect the absolute value of the pixel value. By displaying the difference image in this way, the user can check for defects.

[0076] (2) Error display above threshold The display control unit 150 highlights and displays on the image an area (portion) where an error equal to or greater than a preset threshold occurs based on the error information. The images that highlight the error are, for example, a reference image, a captured image, and a difference image. The highlighting of the error is, for example, by coloring the portion where the error occurs. Furthermore, the display control unit 150 may display coordinate information of the portion where the error occurs. By displaying the portion where the error occurs in this way, the user can identify the defective portion.

[0077] (3) Heat Map The display control unit 150 displays a heat map based on the error information superimposed on the image. The heat map is an image that visualizes the intensity of the error according to the shade of color, etc. The images on which the heat map is superimposed are, for example, a reference image, a captured image, and a difference image. In this way, by using the heat map, the user can easily check the defective portion.

[0078] (4) Histogram The display control unit 150 displays a histogram based on the error information. The histogram, for example, shows the number of pixels for each error value using a bar graph or the like. If there are multiple captured images, the histogram may show the number of images for each error value using a bar graph or the like. By displaying the histogram in this way, the user can check the error mean, variance, outliers, etc.

[0079] (5) Enlarged view The display control unit 150 enlarges and displays the image of the part with a large error. The images to be enlarged are, for example, the reference image, the captured image, and the difference image. By displaying the enlarged image in this way, the user can check the part with the error in more detail.

[0080] The configuration of the inspection device 100 according to the first embodiment has been described above. Next, the differences between a conventional inspection device and the inspection device 100 according to the first embodiment will be described with reference to FIGS. 11 and 2.

[0081] FIG. 11 is an explanatory diagram comparing the line profiles of each image obtained by a conventional inspection device. The conventional inspection device does not have the function of correcting misalignment as in this embodiment. FIG. 11 shows a line profile 10 of the design image, a line profile 20 of the reference image (with misalignment), and a line profile 30 of the captured image. Each line profile also shows its center of gravity: line profile 10 shows center of gravity position 11, line profile 20 shows center of gravity position 21, and line profile 30 shows center of gravity position 31.

[0082] As shown in Figure 11, when an image conversion filter whose center of gravity is shifted from the center position is applied to a design image, a reference image with a positional shift is generated. In Figure 11, the center of gravity 11 in the design image and the center of gravity 31 in the photographed image are both aligned at the center, but the center of gravity 21 in the reference image is shifted from the center position, resulting in a positional shift (gap) between the reference image and the photographed image. Since inspection equipment detects errors based on the difference between the reference image and the photographed image, such positional shifts can increase false detections.

[0083] Fig. 2 is an explanatory diagram comparing line profiles of each image in the first embodiment. Fig. 2 shows a line profile 10 of a design image, a line profile 200 of a reference image (after position correction), and a line profile 30 of a captured image. Furthermore, a line profile 20 of a reference image (with misalignment) is also shown for comparison with line profile 200. As in Fig. 11, line profile 10 shows center of gravity position 11, line profile 200 shows center of gravity position 201, line profile 20 shows center of gravity position 21, and line profile 30 shows center of gravity position 31.

[0084] As shown in Figure 2, in the first embodiment, when an image conversion filter that corrects the center of gravity to a central position is applied to a design image, a reference image with corrected positional deviation (gap) is generated. In Figure 2, the center of gravity 11 in the design image, the center of gravity 201 in the reference image, and the center of gravity 31 in the captured image are all aligned at their central positions. By correcting the positional deviation in this way, the center of gravity of the reference image and the captured image are aligned, thereby reducing the difference between the two, and the inspection device 100 can reduce false detections.

[0085] The above has described the differences between the conventional inspection device and the inspection device 100 according to the first embodiment. Next, the operation of the inspection device 100 will be described with reference to the flowchart of FIG.

[0086] Fig. 3 is a flowchart illustrating the operation of the inspection device 100. The flowchart in Fig. 3 shows a series of steps from when a design image and a captured image are input to the inspection device 100 until the inspection results are output.

[0087] (Step ST110) The design image acquisition unit 110 acquires a design image.

[0088] (Step ST120) After the design image is acquired, the captured image acquisition unit 120 acquires the captured image. The process of step ST120 may be performed before the process of step ST110, or may be performed simultaneously with the process of step ST110.

[0089] (Step ST130) After the captured image is acquired, the image processing unit 130 generates a corrected reference image in which the positional deviation has been corrected. Hereinafter, the process of step ST130 will be referred to as "reference image generation process." A specific example of the reference image generation process will be described with reference to the flowchart of FIG. 4.

[0090] Fig. 4 is a flowchart illustrating the reference image generation process of the flowchart of Fig. 3. The flowchart of Fig. 4 transitions from step ST120.

[0091] (Step ST131) After the design image is acquired, the image conversion filter calculation unit 131 calculates an image conversion filter based on the design image and the captured image.

[0092] (Step ST132) After the image conversion filter is calculated, the filter correction unit 132 generates a corrected image conversion filter based on the amount of deviation between the center position and the center of gravity position of the image conversion filter. Specifically, the filter correction unit 132 calculates a correction value based on the amount of deviation, and corrects the image conversion filter using the calculated correction value to generate the corrected image conversion filter.

[0093] (Step ST133) After the corrected image conversion filter is generated, the reference image generation unit 133 generates a corrected reference image in which the positional deviation is corrected based on the design image and the image conversion filter. After step ST133, the process proceeds to step ST140.

[0094] (Step ST140) After the corrected reference image is generated, the error information generating unit 140 generates error information based on the captured image and the corrected reference image.

[0095] (Step ST150) After the error information is generated, the display control unit 150 displays the test results based on the error information. After step ST150, the process ends.

[0096] As described above, the inspection apparatus according to the first embodiment acquires a design image based on design data created by design software, acquires a captured image of an inspection target created based on the design data, and generates a corrected reference image in which misalignment caused by a misalignment between the center position and center of gravity of an image conversion filter used to create a reference image from the design image is corrected. The inspection apparatus according to the first embodiment also calculates an image conversion filter based on the design image and the captured image, calculates a correction value based on the amount of misalignment between the center position and center of gravity of the image conversion filter, corrects the image conversion filter using the correction value to generate a corrected image conversion filter, and generates the corrected reference image based on the design image and the corrected image conversion filter. Therefore, the inspection apparatus according to the first embodiment can reduce false detections by generating a reference image in which misalignment caused by the image conversion filter is corrected.

[0097] (Second embodiment) The inspection device according to the first embodiment corrects the misalignment of the image conversion filter in the image processing unit, and generates a misalignment-corrected reference image using the misalignment-corrected image conversion filter. The inspection device according to the second embodiment generates a reference image in the image processing unit using the image conversion filter before misalignment correction, and generates a misalignment-corrected reference image by correcting the misalignment of the reference image.

[0098] 5 is a block diagram illustrating the configuration of an inspection device 500 according to the second embodiment. The inspection device 500 includes a design image acquisition unit 510, a captured image acquisition unit 520, an image processing unit 530, an error information generation unit 540, and a display control unit 550. Note that the design image acquisition unit 510, the captured image acquisition unit 520, and the display control unit 550 have substantially the same configurations as the design image acquisition unit 110, the captured image acquisition unit 120, and the display control unit 150 in FIG. 1, and therefore a description thereof will be omitted.

[0099] The image processing unit 530 receives the design image from the design image acquisition unit 510 and receives the captured image from the captured image acquisition unit 520. The image processing unit 530 generates a corrected reference image in which a positional deviation caused by a deviation between the center position and the center of gravity position of an image conversion filter used when creating a reference image from the design image is corrected. The image processing unit 530 outputs the generated corrected reference image to the error information generation unit 540. Note that the image processing unit 530 may also output a reference image generated from the design image to the error information generation unit 540.

[0100] Specifically, the image processing unit 530 includes an image conversion filter calculation unit 531, a reference image generation unit 532, and a reference image correction unit 533. The image conversion filter calculation unit 531 differs from the image conversion filter calculation unit 131 in FIG. 1 in that the output destinations of the image conversion filter are the reference image generation unit 532 and the reference image correction unit 533.

[0101] The reference image generation unit 532 generates a reference image based on the design image and the image conversion filter. Specifically, the reference image generation unit 532 generates the reference image by performing a convolution operation between the design image and the image conversion filter. The reference image generation unit 532 outputs the generated reference image to the reference image correction unit 533. The reference image generation unit 532 may also output the generated reference image to the error information generation unit 540. The reference image generated by the reference image generation unit 532 may be called an uncorrected reference image because no position correction has been performed on it.

[0102] The reference image correction unit 533 calculates a correction value based on the amount of deviation between the center position of the image conversion filter and the center of gravity position, and corrects the reference image using the correction value to generate a corrected reference image. The reference image correction unit 533 outputs the generated corrected reference image to the error information generation unit 540.

[0103] Specifically, the reference image correction unit 533 corrects the reference image before correction as R na Then, the corrected reference image R a is calculated using, for example, the following equation (15).

[0104]

number

[0105] In addition, when the correction value is a decimal in calculating the corrected reference image, the reference image correction unit 533 may calculate the corrected reference image using an interpolation filter. Note that the interpolation filter may be the same as that described in the first embodiment, and therefore the description thereof will be omitted.

[0106] The error information generation unit 540 receives the captured image from the captured image acquisition unit 120 and receives the corrected reference image from the image processing unit 530. The error information generation unit 540 generates error information based on the captured image and the corrected reference image. The error information generation unit 540 outputs the generated error information to the display control unit 550.

[0107] Furthermore, the error information generating unit 540 may further receive a reference image (reference image before correction) from the reference image generating unit 532. In this case, the error information generating unit 540 may generate error information based on the captured image, the corrected reference image, and further the reference image before correction. For example, the error information generating unit 540 generates first error information based on the captured image and the reference image before correction, and generates second error information based on the captured image and the corrected reference image. Thus, the error information may include the first error information and the second error information.

[0108] In the second embodiment, since a reference image before correction is generated, the display control unit 550 may display a difference image before and after position correction of the reference image as the inspection result. Therefore, the inspection result may further include (6) a display form of a difference image before and after position correction in addition to the five display forms described in the first embodiment. This display form will be described below.

[0109] (6) Difference image before and after position correction The display control unit 550 displays two images: a first difference image obtained from the difference between the captured image and the pre-correction reference image, and a second difference image obtained from the difference between the captured image and the corrected reference image. The display control unit 550 may, for example, display the two difference images side by side, either vertically or horizontally, or may switch between the two difference images by selecting a software button or the like. By displaying the difference images before and after position correction in this way, the user can confirm that defects that may occur depending on the type of filter have disappeared in the difference image after position correction.

[0110] The configuration of the inspection device 500 according to the second embodiment has been described above. Next, the reference image generation process of the inspection device 500 will be described using the flowchart in Fig. 6. Note that the operation of the inspection device 500 is the same as that of the flowchart in Fig. 3, except that the process of step ST130 is replaced with the process of step ST230.

[0111] Fig. 6 is a flowchart illustrating the reference image generation process of the inspection device 500. The flowchart in Fig. 6 corresponds to the process of step ST230, which transitions from step ST120.

[0112] (Step ST231) After the design image is acquired, the image conversion filter calculation unit 531 calculates an image conversion filter based on the design image and the captured image.

[0113] (Step ST232) After the image conversion filter is calculated, the reference image generating unit 532 generates a reference image based on the design image and the image conversion filter.

[0114] (Step ST233) After the reference image is generated, the reference image correction unit 533 generates a corrected reference image in which the positional deviation is corrected based on the deviation amount between the center position and the center of gravity position of the image conversion filter. Specifically, the reference image correction unit 533 calculates a correction value based on the deviation amount, and corrects the reference image using the calculated correction value to generate the corrected reference image. After step ST233, the process proceeds to step ST140.

[0115] As described above, the inspection apparatus according to the second embodiment acquires a design image based on design data created by design software, acquires a captured image of an inspection target created based on the design data, and generates a corrected reference image in which misalignment caused by a misalignment between the center position and center of gravity of an image conversion filter used to create a reference image from the design image is corrected. The inspection apparatus according to the second embodiment also calculates an image conversion filter based on the design image and the captured image, generates a reference image based on the design image and the image conversion filter, calculates a correction value based on the misalignment between the center position and center of gravity of the image conversion filter, and corrects the reference image using the correction value to generate the corrected reference image. Therefore, the inspection apparatus according to the second embodiment can reduce false detections by generating a reference image in which misalignment caused by the image conversion filter is corrected.

[0116] (Third embodiment) The inspection devices according to the first and second embodiments align the corrected reference image and the captured image by correcting the positional deviation of the reference image in the image processing unit. The inspection device according to the third embodiment aligns the reference image and the processed captured image by processing the captured image using a correction value for the positional deviation of the reference image in the image processing unit.

[0117] 7 is a block diagram illustrating the configuration of an inspection device 700 according to the third embodiment. The inspection device 700 includes a design image acquisition unit 710, a captured image acquisition unit 720, an image processing unit 730, an error information generation unit 740, and a display control unit 750. Note that the design image acquisition unit 710 has substantially the same configuration as the design image acquisition unit 110 in FIG. 1 or the design image acquisition unit 510 in FIG. 5, and therefore a description thereof will be omitted.

[0118] The captured image acquisition unit 720 acquires a captured image of an inspection object created based on design data. The captured image acquisition unit 720 outputs the acquired captured image to the image processing unit 730. The captured image acquisition unit 720 may also output the acquired captured image to the error information generation unit 740. The captured image acquired by the captured image acquisition unit 720 may also be called an unprocessed captured image because it has not been subjected to processing to incorporate positional deviation.

[0119] The image processing unit 730 receives the design image from the design image acquisition unit 710 and receives the captured image from the captured image acquisition unit 720. The image processing unit 730 generates a reference image from the design image. The image processing unit 730 also generates a processed captured image by processing the captured image so as to include a positional deviation caused by a deviation between the center position and the center of gravity position of an image conversion filter used when creating the reference image from the design image. The image processing unit 730 outputs the reference image and the generated processed captured image to the error information generation unit 740.

[0120] Specifically, the image processing unit 730 includes an image conversion filter calculation unit 731, a reference image generation unit 732, and a captured image processing unit 733. The image conversion filter calculation unit 731 differs from the image conversion filter calculation unit 131 in Fig. 1 and the image conversion filter calculation unit 531 in Fig. 5 in that the output destination of the image conversion filter is the reference image generation unit 732 and the captured image processing unit 733. The reference image generation unit 732 also differs from the reference image generation unit 532 in Fig. 5 in that the output destination of the reference image is the error information generation unit 740.

[0121] The captured image processing unit 733 calculates a correction value based on the amount of deviation between the center position and the center of gravity position of the image conversion filter, and processes the captured image using the correction value to generate a processed captured image. The captured image processing unit 733 outputs the generated processed captured image to the error information generating unit 740. Note that the captured image processing unit 733 may also be called a correction unit because it processes the captured image using the correction value.

[0122] Specifically, the captured image processing unit 733 converts the captured image before processing into I na In this case, the processed image I a is calculated using, for example, the following equation (16).

[0123]

number

[0124] According to equation (16), the processed captured image is calculated based on the correction value caused by the positional deviation of the reference image. When the correction value is a decimal value in calculating the processed captured image, the captured image processing unit 733 may calculate the corrected reference image using an interpolation filter. The interpolation filter may be the same as that described in the first embodiment, and therefore, a description thereof will be omitted.

[0125] The error information generation unit 740 receives the reference image and the processed captured image from the image processing unit 730. The error information generation unit 740 generates error information based on the reference image and the processed captured image. The error information generation unit 740 outputs the generated error information to the display control unit 750.

[0126] Furthermore, the error information generating unit 740 may further receive a captured image (a captured image before processing) from the captured image acquiring unit 720. In this case, the error information generating unit 740 may generate error information based on the reference image, the processed captured image, and further on the captured image before processing. For example, the error information generating unit 740 generates first error information based on the reference image and the captured image before processing, and generates second error information based on the reference image and the processed captured image. Therefore, the error information may include the first error information and the second error information.

[0127] Specifically, the error information generating unit 740 calculates the error by performing differential processing between the processed captured image and the reference image. Note that the differential processing may be the same as that described in the first embodiment, and therefore a description thereof will be omitted.

[0128] The display control unit 750 receives error information from the error information generation unit 740. The display control unit 750 displays the inspection results based on the error information. The inspection results are substantially the same as the five display modes described in the first embodiment. For example, while the first embodiment mainly displays a difference image related to the corrected reference image, the third embodiment differs in that it mainly displays a difference image related to the processed captured image. However, since the center of gravity positions of the reference image and the captured image are the same, the inspection device 700 can reduce false detections.

[0129] In the third embodiment, since error information regarding the captured image before processing may be generated, the display control unit 750 may display a difference image regarding the captured image before and after the misalignment processing as the inspection result. Therefore, the inspection result may further include a display form (6') of a difference image before and after the misalignment processing in addition to the five display forms described in the first embodiment. In addition, in the third embodiment, this display form is designated as (6') to distinguish it from the display form (6) in the second embodiment. This display form will be described below.

[0130] (6') Difference image before and after position shift processing The display control unit 750 displays two images: a first difference image obtained from the difference between the reference image and the captured image before processing, and a second difference image obtained from the difference between the reference image and the processed captured image. The display control unit 750 may, for example, display the two difference images side by side, either vertically or horizontally, or may switch between the two difference images by selecting a software button or the like. By displaying the difference images before and after the misalignment processing in this way, the user can confirm that defects that may occur depending on the type of filter have disappeared in the difference image after the misalignment processing.

[0131] The configuration of the inspection device 700 according to the third embodiment has been described above. Next, the differences between a conventional inspection device and the inspection device 700 according to the third embodiment will be described with reference to Fig. 8. Note that the conventional inspection device has been described in the first embodiment with reference to Fig. 11, and therefore description thereof will be omitted here.

[0132] Fig. 8 is an explanatory diagram comparing the line profiles of each image in the third embodiment. Fig. 8 shows a line profile 10 of a design image, a line profile 20 of a reference image, and a line profile 800 of a captured image (after misalignment processing). Furthermore, a line profile 30 of a captured image before processing to include misalignment is also shown for comparison with line profile 800. Similarly to Fig. 11, line profile 10 shows center of gravity position 11, line profile 20 shows center of gravity position 21, line profile 30 shows center of gravity position 31, and line profile 800 shows center of gravity position 801.

[0133] As shown in Fig. 8, in the third embodiment, a captured image that intentionally includes a positional shift is generated by processing the captured image based on the positional shift (gap) relative to the reference image. As a result, as shown in Fig. 8, it is possible to align the center of gravity 21 in the reference image and the center of gravity 801 in the captured image after the positional shift processing. Therefore, since both the reference image and the captured image include the same positional shift, the difference between the two due to the positional shift is reduced, and the inspection device 700 can reduce erroneous detections.

[0134] The above has described the differences between the conventional inspection device and the inspection device 700 according to the third embodiment. Next, the operation of the inspection device 700 will be described with reference to the flowchart of FIG.

[0135] Fig. 9 is a flowchart illustrating the operation of the inspection device 700. The flowchart in Fig. 9 shows a series of steps from when a design image and a photographed image are input to the inspection device 700 until the inspection results are output.

[0136] (Step ST310) The design image acquisition unit 710 acquires a design image.

[0137] (Step ST320) After the design image is acquired, the captured image is acquired by the captured image acquisition unit 720. The process of step ST320 may be performed before the process of step ST310, or may be performed simultaneously with the process of step ST310.

[0138] (Step ST330) After the photographed image is acquired, the image conversion filter calculation unit 731 calculates an image conversion filter based on the design image and the photographed image.

[0139] (Step ST340) After the image conversion filter is calculated, the reference image generating unit 732 generates a reference image based on the design image and the image conversion filter.

[0140] (Step ST350) After the reference image is generated, the captured image processing unit 733 generates a processed captured image that has been processed to include a positional shift based on the amount of shift between the center position and the center of gravity of the image conversion filter. Specifically, the captured image processing unit 733 calculates a correction value based on the amount of shift, and processes the captured image using the calculated correction value to generate the processed captured image.

[0141] (Step ST360) After the processed captured image is generated, the error information generating section 740 generates error information based on the reference image and the processed captured image.

[0142] (Step ST370) After the error information is generated, the display control section 750 displays the test results based on the error information. After step ST370, the process ends.

[0143] As described above, the inspection apparatus according to the third embodiment acquires a design image based on design data created by design software, acquires a captured image of an inspection object created based on the design data, and generates a processed captured image that is processed to include a misalignment caused by a misalignment between the center position and the center of gravity of an image conversion filter used to create a reference image from the design image. The inspection apparatus according to the third embodiment also calculates an image conversion filter based on the design image and the captured image, generates a reference image based on the design image and the image conversion filter, calculates a correction value based on the misalignment between the center position and the center of gravity of the image conversion filter, and processes the captured image using the correction value to generate a processed captured image. Therefore, the inspection apparatus according to the third embodiment can reduce false detections by generating a captured image that is processed to include a misalignment caused by the image conversion filter.

[0144] (Hardware configuration) 10 is a block diagram illustrating the hardware configuration of a computer 1000 according to one embodiment. The computer 1000 includes, as hardware components, a central processing unit (CPU) 1010, a random access memory (RAM) 1020, a program memory 1030, an auxiliary storage device 1040, and an input / output interface 1050. The CPU 1010 communicates with the RAM 1020, the program memory 1030, the auxiliary storage device 1040, and the input / output interface 1050 via a bus 1060.

[0145] The CPU 1010 is an example of a general-purpose processor. The RAM 1020 is used by the CPU 1010 as a working memory. The RAM 1020 includes a volatile memory such as a Synchronous Dynamic Random Access Memory (SDRAM). The program memory 1030 stores various programs including test programs. The program memory 1030 may be, for example, a read-only memory (ROM), a part of the auxiliary storage device 1040, or a combination thereof. The auxiliary storage device 1040 stores data non-temporarily. The auxiliary storage device 1040 includes a non-volatile memory such as an HDD or SSD.

[0146] The input / output interface 1050 is an interface for connecting to other devices, and is used to connect to, for example, an input device, an image capture device, and a display device.

[0147] Each program stored in program memory 1030 includes computer-executable instructions. When executed by CPU 1010, the program (computer-executable instructions) causes CPU 1010 to perform a predetermined process. For example, when executed by CPU 1010, an inspection program causes CPU 1010 to perform the series of processes described with respect to each section in FIGS. 1, 5, and 7.

[0148] The program may be provided to computer 1000 in a state where it is stored on a computer-readable storage medium. In this case, for example, computer 1000 may further include a drive (not shown) for reading data from the storage medium, and acquire the program from the storage medium. Examples of storage media include magnetic disks, optical disks (CD-ROM, CD-R, DVD-ROM, DVD-R, etc.), magneto-optical disks (MO, etc.), and semiconductor memories. Alternatively, the program may be stored on a server on a communications network, and computer 1000 may download the program from the server using input / output interface 1050.

[0149] The processing described in the embodiments is not limited to being performed by a general-purpose hardware processor such as CPU 1010 executing a program, but may also be performed by a dedicated hardware processor such as an ASIC (Application Specific Integrated Circuit). The term processing circuit (processing unit) includes at least one general-purpose hardware processor, at least one dedicated hardware processor, or a combination of at least one general-purpose hardware processor and at least one dedicated hardware processor. In the example shown in Figure 10, CPU 1010, RAM 1020, and program memory 1030 correspond to the processing circuit.

[0150] Therefore, according to the above embodiments, it is possible to reduce false detections.

[0151] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0152] 10...line profile, 11...center of gravity position, 20...line profile, 21...center of gravity position, 30...line profile, 31...center of gravity position, 100...inspection device, 100...inspection device, 110...design image acquisition unit, 120...captured image acquisition unit, 130...image processing unit, 131...image conversion filter calculation unit, 132...filter correction unit, 133...reference image generation unit, 140...error information generation unit, 150...display control unit, 200...line profile, 201...center of gravity position, 500...inspection device, 500...inspection device, 510...design image acquisition unit, 520...captured image acquisition unit, 530 ...Image processing unit, 531...Image conversion filter calculation unit, 532...Reference image generation unit, 533...Reference image correction unit, 540...Error information generation unit, 550...Display control unit, 700...Inspection device, 700...Inspection device, 710...Design image acquisition unit, 720...Captured image acquisition unit, 730...Image processing unit, 731...Image conversion filter calculation unit, 732...Reference image generation unit, 733...Captured image processing unit, 740...Error information generation unit, 750...Display control unit, 1000...Computer, 1030...Program memory, 1040...Auxiliary storage device, 1050...Input / output interface, 1060...Bus.

Claims

1. a design image acquisition unit that acquires a design image based on design data created by the design software; a captured image acquisition unit that acquires a captured image of an inspection object created based on the design data; an image processing unit that generates a corrected reference image in which a positional deviation caused by a deviation between the center position and the center of gravity position of an image conversion filter used when creating a reference image from the design image is corrected, or a processed captured image that has been processed to include the positional deviation; An inspection device comprising:

2. The image processing unit an image conversion filter calculation unit that calculates the image conversion filter based on the design image and the captured image; a correction unit that calculates a correction value based on the amount of deviation between the center position and the center of gravity position of the image conversion filter, and corrects the image conversion filter using the correction value to generate a corrected image conversion filter; a reference image generation unit that generates the corrected reference image based on the design image and the corrected image conversion filter; The inspection device of claim 1 , comprising:

3. an error information generating unit that generates error information based on the captured image and the corrected reference image; The inspection device of claim 2 further comprising:

4. a display control unit that displays the inspection result based on the error information The inspection device of claim 3 further comprising:

5. The image processing unit an image conversion filter calculation unit that calculates the image conversion filter based on the design image and the captured image; a reference image generation unit that generates the reference image based on the design image and the image conversion filter; a correction unit that calculates a correction value based on the amount of deviation between the center position and the center of gravity position of the image conversion filter, and corrects the reference image using the correction value to generate the corrected reference image; The inspection device of claim 1 , comprising:

6. an error information generating unit that generates error information based on the captured image and the corrected reference image; The inspection device of claim 5 further comprising:

7. the error information generating unit generates the error information further based on the reference image; the error information includes first error information based on the captured image and the reference image and second error information based on the captured image and the corrected reference image; The inspection device according to claim 6.

8. a display control unit that displays the inspection result based on the error information The inspection device of claim 7 further comprising:

9. The image processing unit an image conversion filter calculation unit that calculates the image conversion filter based on the design image and the captured image; a reference image generation unit that generates the reference image based on the design image and the image conversion filter; a correction unit that calculates a correction value based on the amount of deviation between the center position and the center of gravity position of the image conversion filter, and processes the captured image using the correction value to generate the processed captured image; The inspection device of claim 1 , comprising:

10. an error information generating unit that generates error information based on the reference image and the processed captured image; The inspection device of claim 9 further comprising:

11. the error information generating unit generates the error information further based on the captured image; the error information includes first error information based on the reference image and the captured image and second error information based on the reference image and the processed captured image; The inspection device according to claim 10.

12. a display control unit that displays the inspection result based on the error information The inspection device of claim 11 further comprising:

13. The image conversion filter includes a plurality of filters, the correction unit calculates the correction value based on a plurality of deviation amounts calculated from the center positions and center of gravity positions of the plurality of filters, respectively. The inspection device according to any one of claims 2 to 12.

14. the correction unit calculates a sum, average, maximum, minimum, median, or mode of the plurality of deviation amounts as the correction value; The inspection device according to claim 13.

15. the correction unit calculates the maximum or minimum absolute value of the plurality of deviation amounts as the correction value. The inspection device according to claim 13.

16. each of the plurality of filters has a weight; the correction unit calculates the correction value based on weights of the plurality of filters corresponding to the plurality of deviation amounts, respectively.

16. The inspection device according to claim 15.

17. acquiring a design image based on design data created by the design software; acquiring a photographed image of an inspection object created based on the design data; generating a corrected reference image in which a positional deviation caused by a deviation between the center position and the center of gravity position of an image conversion filter used when creating a reference image from the design image has been corrected, or a processed captured image that has been processed to include the positional deviation; An inspection method comprising:

18. Computer means for acquiring a design image based on design data created by the design software; a means for acquiring a photographed image of an inspection object created based on the design data; A means for generating a corrected reference image in which a positional deviation caused by a deviation between the center position and the center of gravity position of an image conversion filter used when generating a reference image from the design image has been corrected, or a processed captured image that has been processed to include the positional deviation. Inspection program to function as.

Images