JP2007310162A - Inspecting device and inspecting method, and manufacturing method for pattern substrate using same inspecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspecting device and an inspecting method that remove a fine defect desirous of being ignored which originates from an OPC pattern of a scattering bar etc., in defect inspection of a mask with a pattern, and a manufacturing method for a pattern substrate using the inspecting device and inspecting method. <P>SOLUTION: The inspecting device includes a filter generator which generates an OPC filter masking an OPC area corresponding to the 0PC pattern by using a first image and a second image, a high-sensitivity defect candidate detector which detects a defect candidate with high sensitivity from a result of comparison between the first image and the second image, a low-sensitivity detect candidate detector which detects a defect candidate with low sensitivity from the result of comparison between the first image and the second image, and a defect judgement unit which uses the OPC filter to judge the low-sensitivity defect candidate detected by the low-sensitivity defect candidate detector as a defect in the OPC area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection apparatus, an inspection method, and a pattern substrate manufacturing method using the inspection method. In particular, an inspection apparatus and inspection method for a mask having an OPC pattern, and a method for manufacturing a patterned substrate using the inspection method.

  With the miniaturization of semiconductors, there is a demand for reducing the size of a pattern formed on a photomask for exposure. In recent years, the miniaturization of mask pattern design rules has further accelerated, and the development speed of various semiconductor devices has also accelerated. Further, due to the miniaturization of the pattern formed on the photomask, the interference effect due to the light diffraction phenomenon has become prominent. For this reason, a pattern different from the design data is transferred to the wafer, which causes causes such as a decrease in yield of the integrated circuit to be finally formed and malfunction of the integrated circuit.

  In order to solve this problem, a technique called OPC (Optical Proximity Effect Correction) that reduces pattern deformation after projection exposure due to the light interference effect has been developed. In this method, the photomask pattern is corrected with respect to the design data by evaluating the influence of the diffraction effect from a simulation or the like. That is, the transfer pattern faithfully reproduces the design data by previously adding an auxiliary pattern different from the main pattern accompanying the design data to the mask pattern.

  Further, due to the reduction in pattern size, defects such as wiring insulation defects and short circuits due to defects in the pattern in the semiconductor manufacturing process are likely to occur, resulting in a decrease in yield. In order to prevent such problems from occurring, a high-precision and defect-free mask is required, and whether or not there is a defect in a semiconductor substrate or a pattern substrate such as a photomask used in the manufacturing process. An inspection device is used to inspect the above. In the mask defect inspection, it is necessary to further improve the defect detection sensitivity.

  There are mainly two types of photomask inspection apparatuses: a die-to-database method and a die-to-die method. In the die-to-database method, a defect is detected by comparing an actually detected pattern image with CAD data stored in a processing device such as a computer. In contrast, the die-to-die method detects defects by detecting pattern images of the same pattern arranged at different positions and comparing them.

In these mask inspection apparatuses, when a mask having an OPC pattern is inspected, a pseudo defect may occur. This is because a mask inspection apparatus has an optical sensitivity limit, and a pattern width or pattern interval of a certain value or less cannot be read normally. Since a difference occurs between the mask pattern obtained by the inspection and the reference data, it is determined to be a pseudo defect. In addition, a defect in a minute auxiliary pattern such as a scattering bar which is an example of an OPC pattern has a lower transferability than a defect in the main pattern, and thus does not need to be detected with high sensitivity. Since the defect detection is performed including the scattering bar having a narrow line width, there is a high possibility that a minute difference of the scatter bar itself which is not to be inspected is detected as a defect. In particular, a fine pattern such as a scattering bar has a large variation in pattern formation. For this reason, by increasing the sensitivity of the inspection apparatus, a lot of defects that should be ignored occur, which hinders defect evaluation. Therefore, in Patent Document 1, the mask is reconstructed by extracting the OPC pattern and the region to be inspected from the design data.
Japanese Patent Laid-Open No. 2004-145152

  The present invention has been made to solve such problems, and in inspection of a mask with a pattern, an inspection apparatus and inspection for removing minute defects to be ignored derived from an OPC pattern such as a scattering bar. It is an object of the present invention to provide a method, an inspection apparatus, and a pattern substrate manufacturing method using the inspection method.

  The inspection apparatus according to the first aspect of the present invention is a first image picked up with respect to a photomask having a main pattern transferred to an image plane and an OPC pattern for performing proximity effect correction on the main pattern. An inspection apparatus that compares the second image with a second image to detect a defect provided in the mask and inspects the light, and condenses the light from the illumination light source and the light from the illumination light source. An illumination light source system that emits light to the sample, and a detector that detects the luminance of light transmitted through or reflected from the sample out of light emitted from the illumination light source system to capture the image of the sample; A filter creation unit that generates an OPC filter that masks an OPC region corresponding to an OPC pattern using the first image and the second image, and a comparison between the first image and the second image Detect defect candidates with high sensitivity to the results By using the OPC filter with a sensitivity defect candidate detection unit, a low sensitivity defect candidate detection unit that detects a defect candidate with low sensitivity with respect to a comparison result between the first image and the second image. The OPC region includes a defect determination unit that determines the low sensitivity defect candidate detected by the low sensitivity defect candidate detection unit as a defect. By doing in this way, the defect detection which removed the defect to ignore can be performed.

  In the inspection apparatus according to the second aspect of the present invention, a process for applying a maximum value filter and a minimum value filter are applied to the first image and the second image in the filter creation unit in the inspection apparatus described above. By performing the processing, a main pattern mask filter for masking the main pattern is generated, and the OPC filter is generated based on the main pattern filter. In this way, a filter that can mask the main pattern can be created. In the inspection apparatus according to the third aspect of the present invention, the process of applying the maximum value filter and the process of applying the minimum value filter are performed a plurality of times by the filter creating unit. By doing in this way, the image by the OPC pattern in the main pattern mask filter can be removed.

  The inspection apparatus according to a fourth aspect of the present invention is the main pattern mask for the first image and the second image in the filter creation unit of the inspection apparatus according to the second aspect and the third aspect. The OPC mask filter is generated by performing a process of applying a filter and performing a process of applying a maximum value filter to the first image and the second image to which the main pattern filter has been applied. This makes it possible to create an OPC mask filter that can mask not only the OPC pattern but also the vicinity of the OPC pattern.

  An inspection apparatus according to a fifth aspect of the present invention is a transmission / reflection image captured with respect to a photomask having a main pattern transferred to an imaging plane and an OPC pattern that performs proximity effect correction on the main pattern. An inspection apparatus that detects and inspects a defect provided in the mask in a simultaneous photographed image, condensing light from a transmission illumination light source and irradiating the mask, and epi-illumination An epi-illumination optical system that collects light from a light source and irradiates the mask, and transmits and reflects the sample out of the light emitted from the illumination light source system to the sample in order to capture an image of the sample. The amount of reflected light detected by the detector reflected by a light-shielding pattern composed of a detector that detects at least one of light and the main pattern and the OPC pattern transmits light. A light amount adjusting means for adjusting at least one light amount of the illumination light source so as to be 1.5 times or more of the light amount of the transmitted light detected by the detector through an excessive pattern; the transmitted light; and A filter creation unit that generates an OPC filter that masks an OPC region corresponding to an OPC pattern using a transmission / reflection simultaneous photographed image created by reflected light, and a high sensitivity for the transmission / reflection simultaneous photographed image. A high-sensitivity defect candidate detection unit that detects a defect candidate, a low-sensitivity defect candidate detection unit that detects a defect candidate with low sensitivity, and the OPC filter for the transmission and reflection simultaneous captured image, and the OPC region Then, the defect determination part which determines the low sensitivity defect candidate detected by the said low sensitivity defect candidate detection part as a defect is provided.

  An inspection apparatus according to a sixth aspect of the present invention is the inspection apparatus according to the fifth aspect, wherein the filter creating unit applies a maximum value filter to the simultaneous transmission / reflection reflection image and a minimum value. A main pattern mask filter that masks the main pattern is generated by performing a filtering process, and the OPC filter is generated based on the main pattern filter.

  An inspection apparatus according to a seventh aspect of the present invention is the inspection apparatus according to the sixth aspect, wherein the process of applying the maximum value filter and the process of applying the minimum value filter are performed a plurality of times by the filter creation unit. It is what is said. The inspection apparatus according to an eighth aspect of the present invention is the inspection apparatus according to the sixth aspect or the seventh aspect, wherein the filter creating unit applies the main pattern mask filter to the transmission / reflection simultaneous captured image. The OPC mask filter is generated by performing a process of applying a maximum value filter to the transmission / reflection simultaneous photographed image to which the main pattern filter is applied.

  An inspection method according to a ninth aspect of the present invention is a first image picked up by a photomask having a main pattern transferred to an imaging plane and an OPC pattern for performing proximity effect correction on the main pattern. An inspection method for comparing a second image with a second image to detect a defect provided in the mask and detecting the light transmitted through or reflected by the photomask. An imaging step for capturing the second image and the second image, and an OPC mask filter creating step for generating an OPC filter for masking an OPC region corresponding to the OPC pattern, using the first image and the second image. , A high-sensitivity defect candidate detection step for detecting defect candidates with high sensitivity with respect to a comparison result between the first image and the second image, the first image, and the second image Low sensitivity and defect A low-sensitivity defect candidate detection step for detecting a low-sensitivity defect candidate and a defect determination step for determining, as a defect, the low-sensitivity defect candidate detected by the low-sensitivity defect candidate detection unit in the OPC region by using the OPC filter. Inspection method. By using this method, it is possible to detect a defect by removing a defect to be ignored.

  An inspection method according to a tenth aspect of the present invention is a process for applying a maximum value filter to the first image and the second image and a minimum value filter in the OPC mask filter creating step in the inspection method described above. This is an inspection method for generating a main pattern mask filter that masks the main pattern. By using this inspection method, a filter capable of masking the main pattern can be created.

  An inspection method according to an eleventh aspect of the present invention is an image obtained by masking the main pattern with respect to the first image and the second image in the OPC mask filter creating step in the inspection method according to the tenth aspect. From this, it is an inspection method for creating the OPC mask filter by performing a process of applying a maximum value filter. By using this inspection method, the image by the OPC pattern in the main pattern mask filter can be removed.

  In the inspection method according to the twelfth aspect of the present invention, in the OPC mask filter creation step in the inspection methods according to the tenth and eleventh aspects, the first image and the second image are generated using the main pattern mask filter. This is an inspection method for generating the OPC mask filter by performing a process of applying a maximum value filter from an image obtained by masking the main pattern from the image. By using this inspection method, it is possible to create an OPC mask filter that can mask not only the OPC pattern but also the vicinity of the OPC pattern.

  An inspection method according to a thirteenth aspect of the present invention is a transmission reflection imaged with respect to a photomask having a main pattern transferred to an imaging plane and an OPC pattern that performs proximity effect correction on the main pattern. An inspection method in which a defect provided in the mask is detected by using a simultaneously photographed image, and the amount of reflected light in a light shielding pattern composed of the main pattern and the OPC pattern is light Adjusting the amount of light of the illumination light source so that the amount of transmitted light detected through the transmission pattern passing through the light is 1.5 times or more, and simultaneously transmitting the light transmitted through the photomask and the reflected light. An imaging step for detecting and imaging the simultaneous transmission / reflection image and an OPC pattern for masking an OPC area corresponding to the OPC pattern using the transmission / reflection simultaneous image. An OPC mask filter creating step for generating data, a high-sensitivity defect candidate detecting step for detecting defect candidates with high sensitivity for the transmission and reflection simultaneous captured image, and a low sensitivity for the transmission and reflection simultaneous captured image. A low-sensitivity defect candidate detection step for detecting a defect candidate; and a defect determination step for determining a low-sensitivity defect candidate detected by the low-sensitivity defect candidate detection unit as a defect in the OPC region by using the OPC filter; Is an inspection method.

  An inspection method according to a fourteenth aspect of the present invention is the inspection method according to the thirteenth aspect, wherein in the OPC mask filter creation step, a process of applying a maximum value filter to the transmission / reflection simultaneous captured image is performed. This is an inspection method for generating a main pattern mask filter for masking the main pattern by performing a process of applying a minimum value filter.

  An inspection method according to a fifteenth aspect of the present invention is the inspection method according to the fourteenth aspect, wherein an image obtained by masking the main pattern from the transmission / reflection simultaneous captured image in the OPC mask filter creating step is provided. This is an inspection method for creating the OPC mask filter by performing a process of applying a maximum value filter.

  An inspection method according to a sixteenth aspect of the present invention is the inspection method according to the fourteenth aspect or the fifteenth aspect, wherein in the OPC mask filter creation step, the transmission / reflection is performed using the main pattern mask filter. In the inspection method, the OPC mask filter is generated by performing a process of applying a maximum value filter from an image obtained by masking the main pattern from a simultaneous photographed image.

  A pattern substrate manufacturing method according to a seventeenth aspect of the present invention includes an inspection step of inspecting a photomask by the above-described inspection method, and a defect correction step of correcting a defect of the photomask inspected by the inspection step, The pattern substrate manufacturing method includes an exposure step of exposing the substrate through the photomask corrected in the defect correction step, and a developing step of developing the exposed substrate.

  According to the inspection apparatus and the inspection method and the method of manufacturing a patterned substrate using the inspection apparatus and the inspection method according to the present invention, a small defect to be ignored derived from an OPC pattern such as a scattering bar is removed when a defect is detected. can do.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description is omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

Embodiment 1 FIG.
In the inspection method and inspection apparatus according to the present embodiment, a die-to-die method is used in which a mask having an OPC pattern captures two images and compares the two images to inspect the pattern. Further, an OPC filter for masking an OPC area corresponding to a minute OPC pattern is created by using a process for applying a maximum value filter and a process for applying a minimum value filter.

  In the OPC area corresponding to the OPC pattern, the defect candidate detected with low sensitivity is determined as a defect. Accordingly, it is possible to provide an inspection method and an inspection apparatus capable of removing a defect to be ignored, which is a minute defect derived from the OPC pattern, and taking out only a defect to be detected with high sensitivity.

  First, a configuration diagram of an inspection apparatus according to the present embodiment is shown in FIG. 1, and the inspection apparatus according to the present embodiment will be described with reference to FIG. The inspection apparatus 1 according to the present embodiment uses a die-to-die method. 11 is an illumination light source, 12 and 13 are lenses, 14 is an aperture stop, and 15 is a lens. These are for irradiating light from the back side of the photomask 10 in order to detect a pattern image of the photomask 10. It is an illumination optical system. Reference numerals 16 and 17 denote lenses, and reference numeral 18 denotes a light receiving sensor.

  A transmission illumination optical system for causing the light emitted from the illumination light source 11 to enter the photomask 10 will be described. The illumination light source 11 can use, for example, one multimode optical fiber that is a small light source. When an optical fiber is used as the illumination light source 11, the light source is disposed in the vicinity of one end of the optical fiber, and the other end is disposed on the optical axis. Here, one end on the light source side is an incident end of light from the light source, and a multi-end is an emission end. Light incident on the incident end of the optical fiber from the light source propagates through the optical fiber and is emitted from the exit end. Thereby, the photomask 10 can be irradiated with light emitted at an emission angle or less determined by the NA (numerical aperture) of each optical fiber. The illumination light source 11 may be a bundle fiber in which a plurality of optical fibers are bundled in addition to a single optical fiber.

  The light emitted from the illumination light source 11 is refracted by the lens 12 and enters the lens 13. The light incident on the lens 13 is refracted by the lens 13 and becomes substantially parallel light and enters the aperture stop 14. The aperture stop 14 is provided with an opening having a predetermined size around the optical axis. At this time, stray light is blocked by the aperture stop 14. The light that has passed through the aperture stop 14 enters the lens 15. The lens 15 is an objective lens and collects light so that an image of a field stop is formed on the surface of the pattern forming surface of the photomask 10. Using such an optical system, the photomask 10 is illuminated with light from the illumination light source 11.

  The photomask 10 is placed on an XY stage (not shown) connected to a driving mechanism, and is provided so as to be able to scan in the direction of the arrow in FIG. Of course, the scanning direction may be opposite to the arrow direction. Then, the entire surface of the photomask is illuminated by raster scanning the photomask 10. Thereby, the entire surface of the photomask 10 can be inspected.

  The light that illuminates the photomask 10 from the illumination light source 11 in this way is transmitted based on the pattern formed on the photomask 10. The light emitted from the illumination light source 11 passes through a transmission pattern other than the light shielding pattern on the photomask 10 and enters the lens 16. On the other hand, when the light emitted from the illumination light source 11 enters the light shielding pattern, it is reflected. The light shielding pattern has a main pattern to be transferred and an OPC pattern for performing OPC on the main pattern. A region corresponding to the main pattern is a main pattern region, and a region corresponding to the OPC pattern is an OPC region. A region corresponding to the transmission pattern is defined as a transmission region.

  Thus, the light transmitted through the photomask 10 from the illumination light source 11 enters the lens 16. This light is refracted by the lens 16 and enters the lens 17. The light incident on the lens 17 is refracted by the lens 17 and incident on the light receiving sensor 18. The light receiving sensor 18 is a photodetector such as a CCD, for example, and outputs a signal based on the luminance of incident light to the processing device 20. The processing device 20 is an information processing device having a personal computer or the like. The processing device 20 is provided with an A / D converter 21 and converts an output signal from the light receiving sensor 18 from an analog signal to a digital signal. This digital signal is stored in the memory 22. Further, an output signal from a drive mechanism that drives the photomask 10 is input to the processing apparatus 20. Based on the output signal from the drive mechanism, the position (coordinates) on the photomask of the detection location is specified.

  The memory 22 stores luminance data based on the luminance of light in each pixel. Further, the memory 22 can store luminance data corresponding to a certain area of the photomask. The processing device 20 includes a display device such as an LCD or CRT, and can display a pattern image. By the inspection apparatus as described above, a pattern image by two transmission images can be obtained. In the above-described apparatus, the pattern image based on the transmission image is acquired, but the pattern image based on the reflection image may be acquired.

  In the inspection apparatus according to the present embodiment, a filter for hiding the OPC pattern such as a scattering bar is created. This filter is a filter for obscuring an OPC area that is slightly wider than the OPC pattern. Then, highly sensitive defect candidate detection is performed on the mask, and the above-described filter is applied to the defect region obtained at this time. As a result, defects derived from the OPC pattern are removed. At this time, even the defect to be detected in the OPC area is removed. Therefore, defect detection with low sensitivity is performed on the mask. This makes it possible to compensate for a defect to be detected in the OPC area. A defect candidate is determined when the difference between the luminance data of the two images to be compared is greater than or equal to a threshold value. A low threshold value is referred to as high sensitivity detection, and a high value is referred to as low sensitivity detection. Thereby, it is possible to reliably detect only defects that affect the transfer during exposure. Therefore, defect detection can be performed accurately.

  Next, a method for creating a filter for masking the vicinity of the OPC pattern will be described. First, a process for applying a maximum value filter to the input image is performed. The maximum value filter is to obtain the maximum value of luminance data of pixels near the target pixel and use the maximum value as the luminance data after filtering in the target pixel. For example, consider a case of 3 pixels × 3 pixels having luminance data as shown in FIG. At this time, the maximum value of the luminance data of the 3 pixels × 3 pixels is obtained as a pixel in the vicinity of the target pixel. Since the maximum value is 9 at this time, the luminance data of the central pixel which is the target pixel is set to 9 (see FIG. 2B). By doing so, the bright region can be expanded. Here, 3 pixels × 3 pixels have been described as an example, but a matrix having a number of pixels of 3 or more, such as 5 pixels × 5 pixels, may be used. Further, a process other than the 8-neighbor process may be used.

  Similarly, the minimum value filter is to obtain the minimum value of the luminance data possessed by the pixels in the vicinity of the target pixel and use the minimum value as the luminance data after filtering in the target pixel. For example, consider a case of 3 pixels × 3 pixels having luminance data as shown in FIG. At this time, the minimum value of luminance data of the 3 pixels × 3 pixels is obtained as a pixel in the vicinity of the target pixel. At this time, since the minimum value is 0, the luminance data of the pixel that is the target pixel is set to 0 (see FIG. 2C). By doing so, a bright region can be contracted.

  In this case, by using the maximum value filter for the input image, the bright part erodes the dark part, so that a minute pattern such as a scattering bar becomes smaller. At this time, the maximum value filtering process is repeated until the scattering bar disappears. Thereafter, binarization is performed, and the size of the main pattern is restored by using expansion processing.

  This creates an image with no change in the main pattern. By repeating the maximum value filter process until the minute pattern such as the scattering bar disappears, the minute pattern can be erased and only the main pattern can be extracted. An image obtained by extracting only the main pattern is called a main pattern mask filter.

  At this time, the main pattern mask filter is a filter that does not pass the luminance data of the portion where the main pattern is located and sets the luminance data of the set value. Further, in the portion other than the main pattern, the filter passes the luminance data of the pixel as it is. The set value described above may be a value that does not become the same value as the scattering bar during binarization processing described later. For example, it may be the same as the luminance data in the transmissive area.

  By using the main pattern mask filter and the input image, an image in which the luminance data of the main pattern area becomes the set value is completed. In this image, an OPC pattern such as a scattering bar is left. By applying a minimum value filter to this image and binarizing it, it is possible to obtain a filter that masks an OPC area that is a slightly larger area from the OPC pattern. This filter is called an OPC mask filter. This filter is a filter for masking the OPC area. The OPC mask filter is a filter that does not pass the luminance data of the OPC area and passes the luminance data of the part other than the OPC area as it is. The above operation is performed on two input images. In the first image, the first main pattern mask filter and the first OPC mask filter, and in the second image, the second main pattern mask filter and the second main image. The OPC mask filter is created.

  By using the OPC mask filter as a filter, an image from which an OPC area such as a scattering bar is removed can be taken out. From this, by applying this OPC mask filter to the defect candidate detection result obtained by performing highly sensitive defect candidate detection, defect candidates that are highly likely to be formed in the vicinity of the scattering bar are removed. be able to.

  Furthermore, in the inspection method according to the present embodiment, defect candidates are also detected with low sensitivity for an unfiltered image. This is to detect a large defect in the vicinity of the OPC pattern by performing defect candidate detection with low sensitivity. Such large defects need to be detected because they are transferred during exposure. For this reason, large defects in the vicinity of the OPC pattern are compensated for by detecting defect candidates with low sensitivity.

  In the inspection apparatus according to the present embodiment, mask defect candidates are detected with high sensitivity. A defect candidate near the OPC pattern is removed by applying an OPC mask filter to the detection result of the defect candidate obtained by this highly sensitive defect candidate detection. Also, mask defect candidates are detected with low sensitivity. The defect detection is performed by combining the defect candidates obtained by performing these two defect candidate detections. As a result, it is possible to provide an inspection method and an inspection apparatus that remove a minute defect candidate that is derived from an OPC pattern such as a scattering bar and that is desired to be ignored.

  For example, consider the case where two input images captured by the inspection apparatus are shown in FIGS. 3 (a) and 3 (b). 3A is an input image A, and FIG. 3B is an input image B. At this time, in the input image A, a main pattern 31 having a shape close to a square is provided. A scattering bar 32 is provided in the vicinity of the main pattern 31. The scattering bar 32 is formed with a width less than the resolution limit of the exposure apparatus.

  The main pattern 31 has small convex portions 33 and small transparent foreign matters 34. Further, the scattering bar 32 has a convex portion 35 and a concave portion 36. Here, the convex portions 33 and 35 are portions where the light shielding film protrudes from the pattern based on the design data of the photomask due to, for example, a manufacturing defect. Further, the recess 36 is a portion that is recessed from a pattern based on the photomask design data. The transparent foreign matter 34 is, for example, a portion where the light shielding film has not been formed in the region that becomes the light shielding pattern because the transparent foreign matter has adhered when the light shielding film is formed. Here, 35 and 36 existing in the scattering bar are so small that they do not affect the transfer pattern. Therefore, 35 and 36 need not be determined as defects. That is, 35 and 36 are defects that should be ignored.

  Also in the input image B, a main pattern 41 and a scattering bar 42 having the same shape are formed. However, the input image B has a defect at a location different from the input image A. Specifically, the convex portion 43 exists in the main pattern 41. In addition, a colored defect 44 isolated from the main pattern 41 and the scattering bar 42 exists on the transparent pattern. Furthermore, convex portions 45 and 46 exist on the scattering bars 42a and 42b.

  The convex portions 43, 45, and 46 are portions protruding from the pattern based on the photomask design data in the same manner as the convex portion 35 in the input image A. In addition, the coloring defect 44 is, for example, a place where a foreign substance is attached in a place where the light shielding film is formed in a place where the transparent pattern is formed.

  The convex portions 46 present on the scattering bar 42b are so small that they do not affect the transfer pattern. Therefore, it is not necessary to determine that the convex portion 46 is detected as a defect. That is, the convex part 46 is a defect to be ignored. The term “large defect” or “small defect” as used herein means that when the width of the scattering bar is about 100 nm, a defect having a size of 50 nm or less is a small defect, and a defect having a size larger than that is a large defect.

  In each of the input image A and the input image B, FIGS. 4A and 4B show that the minimum value filtering process is performed and then the binarization is performed and then the contraction process is performed. The diagram shown in FIG. 4A is the main pattern mask filter 51 for the input image A, and the diagram shown in FIG. 4B is the main pattern mask filter 52 for the input image B. The data of the main pattern mask filters 51 and 52 is 0 in the main pattern area, and 1 in the OPC area and the transmission area. Applying this filter uses, for example, a value obtained by integrating the filter value and luminance data for each pixel as luminance data.

  FIG. 5A shows the input image A obtained by applying the main pattern mask filter 51. Further, FIG. 5B is a diagram obtained by applying the main pattern mask filter 52 to the input image B. That is, in FIGS. 5A and 5B, the main pattern is masked and an image with the scattering bar remaining is obtained. The portion where the main pattern at this time is located is shown in white.

  FIGS. 6A and 6B are obtained by subjecting this image to minimum value filter processing and binarization thereafter. Note that. Data that becomes 1 in the binarization process is input to the main pattern. Therefore, the binarization process makes the OPC area 0 and other parts become 1. 6A shows the OPC mask filter 61 for the input image A, and FIG. 6B shows the OPC mask filter 62 for the input image B. These OPC mask filters 61 and 62 have a pattern in which the masked portion is larger than the image shown in FIGS. 5 (a) and 5 (b). By using the OPC mask filters 61 and 62, the vicinity of the scattering bar is masked. The data of the OPC mask filters 61 and 62 is 0 in the OPC area and 1 in the main pattern and the transmission area. Note that expansion processing may be performed when the OPC mask filters 61 and 62 are formed.

  A filtered image A obtained by applying the OPC mask filter 61 to the input image A is shown in FIG. 7A, and a filtered image B obtained by applying the OPC mask filter 62 to the input image B is shown in FIG. It is. 7A and 7B show the areas masked by the OPC mask filters 61 and 62 by whitening. As described above, by applying the OPC mask filter, an image in which only the main pattern is left can be extracted. At this time, it can be seen that the defects located on the scattering bar and the defects existing in isolation have been removed.

  Defect candidate detection is performed using these two images. First, using the input image A and the input image B, highly sensitive defect candidates are detected. FIG. 8A is a diagram in which the defective portion at this time is expressed in white. At this time, any method of defect candidate detection may be used. For example, by aligning two images, the image A is used as a reference image, and the luminance data is compared for each pixel with the image B, and the difference between the luminance data in the image A and the luminance data in the image B exceeds the threshold value. The case is taken out as a defect candidate. The diagram shown in FIG. 8B shows the defect candidate portion white when defect candidate detection is performed with low sensitivity.

  As shown in FIG. 8A, when highly sensitive defect candidate detection is performed, the convex portion 33, the transparent foreign material 34, the convex portion 35, and the concave portion 36 located in the input image A exist. Moreover, the convex part 43 located in the input image B, the coloring defect 44, the convex part 45, and the convex part 46 exist. However, the convex part 35, the concave part 36, and the convex part 46 in the vicinity of the scattering bar are defect candidates to be ignored.

  As shown in FIG. 8B, when the defect candidate detection with low sensitivity is performed, the convex portion 43, the isolated defect 44, and the convex portion 45 located in the input image B are detected. At this time, a large defect that affects the transfer pattern is detected.

  First, the OPC mask filter 61 for the input image A is applied to the high-sensitivity defect candidate detection result shown in FIG. FIG. 9A is a diagram at this time. The defect candidates appearing at this time are considered to be defect candidates to be detected in the input image B. However, here, the transparent defect 34 in the input image A is determined as a defect candidate to be detected in the input image B. This is because filtering could not be performed. That is, the transparent defect 34 appearing in the input image A has disappeared by the maximum value filter processing when the OPC mask filter 61 is created. That is, the transparent defect 34 does not appear in the OPC mask filter 61. Therefore, the transparent defect 34 cannot be filtered by the OPC mask filter 61. Therefore, as shown in FIG. 9A, the transparent defect 34 has been detected as a defect. However, since the transparent defect 34 is a defect existing in the main pattern of the input image A and is considered to be a defect to be detected, the defect in the OPC region of the input image B can be removed.

  Similarly, the OPC mask filter 62 for the input image B is applied to the highly sensitive defect candidate detection result. FIG. 9B is a diagram at this time. The defect candidates appearing at this time are considered to be defect candidates to be detected in the input image A. However, here, the convex portion 43 in the input image B is determined as a defect candidate to be detected in the input image A. The reason is the same as the reason for the transparent defect 34 described above. However, since the convex portion 43 is also a defect existing in the main pattern of the input image B and is considered to be a defect to be detected, a defect obtained by removing the defect in the OPC area in the input image A can be detected.

  As described above, the OPC mask filter 61 is applied to the defect candidate detection result. At this time, it is possible to prevent a defect candidate to be detected as a defect in the input image B from being filtered. Similarly, the OPC mask filter 62 is applied to the defect candidate detection result. At this time, it is possible to prevent the defect candidates detected as defects in the input image A from being filtered.

  In FIGS. 9A and 9B, since the vicinity of the scattering bar is masked, defects near the scattering bar are not detected. Therefore, in FIG. 9A, the transparent defect 34, the convex part 43, and the coloring defect 44 are detected. That is, the defect in the OPC area is removed from the defect candidate detection result. Further, in FIG. 9B, convex portions 33, transparent defects 34, and convex portions 43 are detected. That is, the defect in the OPC area is removed from the defect candidate detection result. Defect detection is performed by combining the defects detected in FIGS. 8B, 9A, and 9B (see FIG. 10). That is, the pixel determined as a defect in any of FIGS. 8B, 9A, and 9B is detected as a defect. From the above, the convex part 33, the transparent defect 34, the convex part 43, the coloring defect 44, and the convex part 45, which are the defects to be detected, are detected. In this way, it is possible to detect only defect candidates that are desired to be detected. Thus, since the high-sensitivity defect candidate in the OPC region is not determined as a defect, only the defect candidate that affects the transfer pattern can be detected and detected as a defect.

  Here, only the defect candidate to be detected is extracted by applying an OPC mask filter to the defect candidate detected with high sensitivity. However, even if it is not such a method, you may detect a defect by the image which masked the OPC area | region using the OPC mask filter for the input image.

  The configuration of the arithmetic processing unit 23 that performs the arithmetic processing described above will be described with reference to FIG. FIG. 11 is a block diagram showing a configuration of the arithmetic processing unit 23. The arithmetic processing unit 23 includes a flare removal unit 231, a shading correction unit 232, a filter creation unit 233, a high sensitivity defect candidate detection unit 234, a low sensitivity defect candidate detection unit 235, and a defect determination unit 236.

  The flare removal unit 231 and the shading correction unit 232 perform preprocessing for performing the above-described processing. That is, the flare removing unit 231 performs processing for removing flare according to the amount of light incident on the light receiving sensor 18. The shading correction unit 232 performs shading correction on the luminance data according to the luminance distribution of the illumination system and the sensitivity distribution in the light receiving sensor 18.

  As described above, the filter creation unit 233 creates a main pattern mask filter by using shrinkage processing, expansion processing, and binarization from a pattern image including an OPC pattern, and generates an OPC mask from the main pattern mask filter and the pattern image. Create a filter. The high sensitivity defect candidate detection unit 234 and the low sensitivity defect candidate detection unit 235 perform high sensitivity defect detection and low sensitivity defect candidate detection from two pattern images. The high sensitivity defect candidate detection unit 234 and the low sensitivity defect candidate detection unit 235 detect defect candidates with different threshold values. The defect determination unit 236 removes defect candidates located in the OPC region by applying an OPC mask filter to defect candidates extracted by performing highly sensitive defect candidate detection. The defect determination is performed by combining the defect candidate obtained by the high-sensitivity defect candidate detection from which the defect candidate in the OPC region is removed and the defect candidate obtained by the low-sensitivity defect candidate detection.

  The processing device 20 is not limited to a physically single device. For example, the A / D converter 21, the memory 22, and the arithmetic processing unit 23 may be incorporated in different devices. Furthermore, parallel processing may be performed using an arithmetic processing unit 23 having a plurality of CPUs. The light receiving sensor 18 may be a one-dimensional line sensor or a two-dimensional area sensor. For example, a CCD sensor, a CMOS sensor, a photodiode array, or the like can be used.

  Further, it may be a delay-integration (TDI) type imaging apparatus. In this case, the scanning direction of the stage coincides with the vertical transfer direction of the signal charge, and the scanning speed and the transfer speed are synchronized. Thereby, detection sensitivity can be improved. The inspection apparatus described above is not limited to inspection of a photomask, and any substrate having a transparent pattern and a light shielding pattern can be used. For example, examples of the sample to be inspected include a color filter substrate in addition to a photomask. The light shielding pattern may be a halftone pattern that transmits a part of the illumination light. The illumination light source 11 is not limited to an optical fiber, and other light sources can be used. For example, a laser light source, a lamp light source, or a bundle fiber can be used.

  A semiconductor wafer or the like is created using the mask inspected by the above inspection method. At this time, the defect is detected by the inspection method described above, the exposed substrate is developed through the mask in which the defect is corrected, etching is performed, and the resist is removed. Thereby, productivity of pattern substrates, such as a semiconductor device, can be improved.

Embodiment 2. FIG.
In the second embodiment, a captured image of simultaneous transmission and reflection illumination is obtained with a mask having an OPC pattern. At this time, the chrome surface reflected light is adjusted to 1.5 or more of the glass surface transmitted light. That is, in the simultaneous illumination photographed image, the glass surface and the chrome surface are adjusted so as to be distinguished by the difference in luminance. An OPC filter for masking an OPC area corresponding to a minute OPC pattern is created from a captured image obtained by this simultaneous illumination by using a process for applying a maximum value filter and a process for applying a minimum value filter.

  In the OPC area corresponding to the OPC pattern, the defect candidate detected with low sensitivity is determined as a defect. Accordingly, it is possible to provide an inspection method and an inspection apparatus capable of removing a defect to be ignored, which is a minute defect derived from the OPC pattern, and taking out only a defect to be detected with high sensitivity. Components and operating principles similar to those of the first embodiment are omitted.

  First, the inspection apparatus according to the present embodiment will be described with reference to FIG. Here, an inspection apparatus that detects defects attached to the photomask 130 as a sample will be described as an example. 111 is a transmission illumination light source, 112 is a transmission filter, 113 is a drive motor, 114 is a mirror, 115 is an objective lens, 116 is a stage, 121 is an epi-illumination light source, 122 is an epi-illumination filter, 123 is a drive motor, and 124 is a beam A splitter, 125 is an objective lens, 141 is a lens, 142 is a detector, and 150 is a processing device.

  A photomask 130 as a sample is provided with a light shielding pattern 131 that reflects light. Specifically, a light shielding pattern 131 is formed on the photomask 130 by forming and patterning a light shielding film such as a chromium film on a transparent glass substrate. Therefore, a region of the photomask 130 where the light shielding pattern 131 is not provided becomes a transmission pattern 132 that transmits light. That is, the photomask 130 includes a light shielding pattern 131 and a transmission pattern 132.

  The light shielding pattern 131 has a higher reflectance than the transmission pattern 132. The photomask 130 is placed on the stage 116. The photomask 130 is placed on the stage 116 so that the pattern surface on which the light shielding pattern 131 is formed is up. The stage 116 is a transparent stage and transmits incident light.

  A transmission illumination optical system for causing the transmission illumination light emitted from the transmission illumination light source 111 to enter the photomask 130 will be described. The transmitted illumination light source 111 is a lamp light source, for example, and emits transmitted illumination light in the direction of the transmission side filter 112. The transmitted illumination light from the transmitted illumination light source 111 passes through the transmission-side filter 112 and enters the mirror 114.

  The mirror 114 is disposed below the stage 116 on which the photomask 130 is placed, and reflects the transmitted illumination light from the transmitted illumination light source 111 in the direction of the photomask 130. The transmitted illumination light reflected by the mirror 114 enters the objective lens 115. The transmitted illumination light refracted by the objective lens 115 enters the photomask 130 through the stage 116. The objective lens 115 collects transmitted illumination light on the pattern surface of the photomask 130.

  Of the transmitted illumination light collected by the objective lens 115 and incident on the photomask 130, the transmitted light transmitted through the photomask 130 is refracted by the objective lens 125 and enters the beam splitter 124. The beam splitter 124 is, for example, a half mirror, which transmits half of incident light and reflects half. The transmitted light that has passed through the beam splitter 124 is refracted by the lens 141 and enters the detector 142.

  The detector 142 is an image pickup device such as a two-dimensional CCD camera, and picks up an optical image of the photomask 130. That is, the lens 141 collects the transmitted light on the light receiving surface of the detector 142. Thereby, the transmission image of the area | region where the transmission illumination light of the photomask 130 was irradiated can be imaged. The detector 142 outputs a detection signal based on the detected light amount to the processing device 150. The processing device 150 includes, for example, an analog circuit for performing defect determination based on a detection signal, and a personal computer for storing and displaying the result of defect determination.

  Next, an epi-illumination optical system for causing the epi-illumination light emitted from the epi-illumination light source 121 to enter the photomask 130 will be described. The epi-illumination light source 121 is a lamp light source, for example, and emits epi-illumination light in the direction of the epi-illumination filter 122. The epi-illumination light from the epi-illumination light source 121 passes through the epi-illumination filter 122 and enters the beam splitter 124. The beam splitter 124 is disposed above the photomask 130 placed on the stage 116, and reflects a part of incident incident illumination light in the direction of the photomask 130. The epi-illumination light reflected by the beam splitter 124 enters the objective lens 125. The objective lens 125 collects the incident illumination light on the pattern surface of the photomask 130.

  Of the epi-illumination light collected by the objective lens 125 and incident on the photomask 130, the reflected light reflected by the photomask 130 is refracted by the objective lens 125 and enters the beam splitter 124. The reflected light transmitted through the beam splitter 124 is refracted by the lens 141 and enters the detector 142. The lens 141 collects the reflected light on the light receiving surface of the detector 142. Thereby, the reflected image of the area | region where the epi-illumination light of the photomask 130 was irradiated can be imaged.

  Here, the objective lens 125 of the epi-illumination optical system and the objective lens 115 of the transmission illumination optical system are arranged on the same optical axis. Accordingly, the transmitted illumination light emitted from the objective lens 115 and the incident illumination light emitted from the objective lens 125 are incident on the same position of the photomask 130. Of the transmitted illumination light emitted from the objective lens 115, the transmitted light transmitted through the photomask 130 and the reflected light reflected from the photomask 130 among the incident illumination light emitted from the objective lens 125 are: Propagates in the same direction on the same optical axis. That is, of the transmitted illumination light, the transmitted light transmitted through the photomask 130 and the reflected light of the incident illumination light reflected by the photomask 130 enter the detector 142 through a common optical path. Therefore, by simultaneously illuminating the photomask 130 using the incident illumination light and the transmitted illumination light, and detecting by the detector 142, an optical image in which the reflected image and the transmitted image are superimposed can be taken.

  The stage 116 on which the photomask 130 is placed is an XY stage provided so as to be movable in the horizontal direction. Therefore, by moving the stage 116 in the horizontal direction, the incident positions of the incident illumination light and the transmitted illumination light on the photomask 130 change relatively. Therefore, the illumination area on the photomask 130 can be scanned, and an arbitrary portion of the photomask 130 can be inspected. Further, the entire surface of the photomask 130 can be inspected by, for example, raster scanning the stage 116.

  The transmission side filter 112 and the epi-illumination side filter 122 are, for example, ND filters, which attenuate incident light and transmit it. Further, the transmission filter 112 and the epi-illumination filter 122 have different light transmittances depending on the rotation angle. For example, the transmission-side filter 112 and the epi-illumination-side filter 122 are divided into a plurality of regions having different light transmittances, and the light transmittance changes stepwise depending on the incident position. Therefore, the amount of transmitted illumination light can be adjusted by rotating the transmission side filter 112 by the drive motor 113. That is, the rotation angle of the drive motor 113 is adjusted so that the transmitted illumination light passes through a region of the transmission-side filter 112 having a desired light transmittance.

  In addition, the amount of incident illumination light can be adjusted by rotating the incident side filter 122 by the drive motor 123. That is, the rotation angle of the drive motor 123 is adjusted so that the epi-illumination light passes through the region having the desired light transmittance in the epi-illumination side filter 122. Thereby, it can adjust so that the light quantity of the transmitted light detected with the detector 142 and the light quantity of reflected light may become a desired ratio.

  In the inspection apparatus according to the present embodiment, the reflected light reflected by the light shielding pattern 131 out of the epi-illumination light from the epi-illumination light source 121 is transmitted through the transmission pattern 132 out of the transmission illumination light from the transmission illumination light source 111. The amount of light is adjusted so that the light amount is 1.5 times or more of the amount of light and is detected by the detector. Furthermore, it is preferable that the amount of reflected light is at least twice the amount of transmitted light.

  For example, the transmission-side filter 112 and the epi-illumination-side filter 122 are rotated and adjusted so as to obtain a desired light amount. Note that in the case where the light amount can be adjusted by only one of the transmission-side filter 112 and the epi-illumination-side filter 122, one of the filters may not be provided. Furthermore, the light amount adjusting means for adjusting the light amount is not limited to the filter and the motor that rotates the filter. For example, the light quantity may be adjusted by putting a plurality of filters in and out of the optical path. Further, the amount of light may be adjusted by changing the output of the epi-illumination light source 121 or the transmission illumination light source 111.

  The transmission pattern 132 of the photomask 130 has a high light transmittance and transmits most of the incident light. Further, the transmissive pattern 132 regularly reflects a very small part of incident light. For example, the transmission pattern has a light transmittance of about 92% and a reflectance of about 4%. The light shielding pattern 131 of the photomask 130 shields substantially all of the incident light. A part of the light shielded by the light shielding pattern 131 is regularly reflected on the surface of the light shielding pattern 131.

  For example, the reflectance of the light shielding pattern 131 is about 10%, and the light transmittance of the light shielding pattern 131 is ideally about 0%. The reflectance at the light shielding pattern 131 is higher than the reflectance at the transmissive pattern 132. Therefore, in the region of the light shielding pattern 131, the change in the light amount of the transmitted illumination light greatly affects the imaging of the composite image of the transmitted image and the reflected image, and the change in the light amount of the incident illumination light hardly affects. In the area of the transmissive pattern 132, the change in the amount of incident illumination light and the amount of transmitted illumination light affects the capture of a composite image. In the region of the transmissive pattern 132, the change in the amount of incident illumination light has a greater influence on the composite image than the change in the amount of transmitted illumination light.

  In the inspection apparatus according to the present embodiment, an OPC filter for hiding an OPC pattern such as a scattering bar is created. This OPC filter is a filter for obscuring an OPC area which is an area slightly wider than the OPC pattern.

  A highly sensitive defect candidate is detected for the mask, and the above-described filter is applied to the defect region obtained at this time. As a result, defects derived from the OPC pattern are removed. At this time, even the defect to be detected in the OPC area is removed. Therefore, defect detection with low sensitivity is performed on the mask. This makes it possible to compensate for a defect to be detected in the OPC area. Further, when the difference between the luminance of the glass surface in the minimum value image after the maximum value described later and the luminance of the pixel having the glass surface luminance in the minimum value image after the maximum value in the maximum value image after the minimum value described later is a certain threshold value or more. Although it is set as a defect candidate, a low threshold is called high-sensitivity detection, and a high threshold is called low-sensitivity detection. Thereby, it is possible to reliably detect only defects that affect the transfer during exposure. Therefore, defect detection can be performed accurately.

  Next, a method for creating an OPC filter for masking the vicinity of the OPC pattern will be described. For example, consider the case where the transmission / reflection simultaneous captured image obtained by the above-described inspection apparatus is shown in FIG. In the transmission / reflection simultaneous captured image shown in FIG. 13A, rectangular main patterns 161a and 161b are provided. Scattering bars 162a to 162e are provided in the vicinity of the main patterns 161a and 161b. The scattering bars 162a to 162e are formed with a width that is less than or equal to the resolution limit of the exposure apparatus.

  The main pattern 161a has a convex portion 163. In addition, the main pattern 161b includes a defect 166 and a convex portion 167 located in the main pattern 161b. The scattering bar 162b has a convex portion 164. Further, a point defect 165 exists between the scattering bar 162c and the main pattern 161b. Here, the convex portion 164 present on the scattering bar 162b is so small as not to affect the transfer pattern. Therefore, the convex portion 164 may not be determined as a defect. That is, the convex portion 164 is a defect that should be ignored.

  First, a maximum value filter is applied to the simultaneous transmission and reflection image shown in FIG. 13A, and the maximum value created by applying the minimum value filter until the main pattern becomes the original size after erasing the OPC pattern. FIG. 13B shows a post-value minimum value image. At this time, the OPC pattern is removed.

  Next, a minimum value filter is applied to the transmission / reflection simultaneous image shown in FIG. 14A (same as FIG. 13A), and after removing the influence of small dark defects, the main pattern is restored to its original size. FIG. 14B shows a maximum value image after the minimum value created by applying the maximum value filter until it becomes. At this time, the minimum value filter is applied to such an extent that the scattering bars 162a to 162e or the scattering bars 162a to 162e and the main patterns 161a and 161b are not fused, and then the maximum value filter is applied until the main pattern becomes the original size. multiply. By doing in this way, the convex parts 163, 164, 167, the defect 166, and the point defect 165 which are defects are removed.

  The OPC filter is created by using the minimum value image after the maximum value shown in FIG. 13B and the maximum value image after the minimum value shown in FIG. 14B. A pixel having a transmissive surface luminance in the minimum value image after the maximum value is selected, and when the pixel in the maximum value image after the minimum value at that position is larger than the glass surface luminance, it is extracted as an OPC pattern candidate region. This is because the pixel having the OPC pattern has the transmission surface luminance in the minimum value image after the maximum value and the light shielding surface luminance in the maximum value image after the minimum value. Further, in the inspection apparatus according to the present embodiment, since the reflection intensity at the light shielding surface is larger than the transmission luminance at the transmission surface, the pixel is selected as the pixel having the transmission surface luminance in the minimum value image after the maximum value, and the pixel The OPC pattern candidate region is extracted by the fact that the luminance in the maximum value image after the minimum value is larger than the transmission surface luminance. An image obtained by extracting the OPC pattern candidate area is shown in FIG.

  This OPC pattern candidate area includes an erroneous candidate area caused by a dot defect on the transmission surface or a foreign substance near the pattern boundary. In order to exclude them, a process of applying a maximum value filter after applying a minimum value filter in the vertical direction and a process of applying a maximum value filter after applying the minimum value filter in the horizontal direction are performed. By superimposing the images obtained by these two processes, an OPC pattern area corresponding to the OPC pattern is extracted. An image of the OPC pattern area at this time is shown in FIG. An OPC filter capable of masking the OPC region can be created by binarizing the image of the OPC pattern region shown in FIG. 15B by applying a minimum value filter in all directions. The OPC filter created at this time is as shown in FIG.

  Therefore, first, a high-sensitivity defect candidate search is performed by setting a threshold value in the transmission / reflection simultaneous image shown in FIG. 13A, and in the image showing the defects 163 to 167 searched at that time, Apply the above OPC filter. The figure at this time is FIG. At this time, the convex portion 164 which is a defect applied to the OPC filter is considered as a defect in the vicinity of the OPC filter and is removed. By doing so, it is possible to remove defect candidates that are likely to be in the vicinity of the scattering bar and that are to be ignored. Thereafter, a defect candidate search with low sensitivity is performed to compensate for a defect to be detected in the vicinity of the scatter limber. In this example, the defect does not exist.

  Here, the luminance profile of the cross section AA in the simultaneous transmission / reflection image (same as FIG. 13A) shown in FIG. 18A will be described as an example. FIG. 18B shows a cross-sectional view taken along the line AA. FIG. 18C shows a luminance profile in the transmission / reflection simultaneous captured image at this time. In FIG. 18C, the horizontal axis represents the pixel position, and the vertical axis represents the luminance at that pixel.

  In the inspection apparatus according to the present embodiment, since the reflected luminance at the light shielding surface is 1.5 times or more the transmitted luminance at the transmissive surface, the luminance value in the luminance profile at the light shielding surface is large. In addition, since the light cannot be transmitted, and the light is scattered without being reflected, the luminance of the pixels having the defects 163 to 167 is remarkably reduced. In addition, in the luminance at the defects 163, 164, 165, and 167 existing on the light-transmitting surface and the defect 166 existing on the light-shielding surface, the decrease in luminance at the defect 166 existing on the light-shielding surface is larger. That is, in the luminance in the transmission / reflection simultaneous photographed image, light shielding pattern> transparent pattern> defect on transparent pattern> defect on light shielding pattern.

  In the luminance profile shown in FIG. 18C, a minimum value luminance profile after the maximum value and a maximum value luminance profile after the minimum value are created. The minimum value luminance profile after the maximum value is shown in FIG. 19A, and the maximum value luminance profile after the minimum value is shown in FIG. 19B. As described above, in the minimum value luminance profile after the maximum value, luminance peaks corresponding to the scattering bars 162a, 162b, and 162c are removed. Further, in the maximum value luminance profile after the minimum value, luminance valleys corresponding to the defects 163 to 167 are removed.

  At this time, holes existing in the main pattern 161b are also removed. From these two luminance profiles, the luminance in the maximum value luminance profile after the minimum value is larger than the luminance in the minimum value luminance profile after the maximum value at the pixel position indicated by an ellipse in FIGS. 19 (a) and 19 (b). It has become. Therefore, the pixel at this pixel position becomes an OPC pattern candidate area (see FIG. 19C). By using the horizontal maximum value filter and the vertical maximum value filter from the OPC pattern candidate region shown in FIG. 19C, the region corresponding to the hole existing in the main pattern 161b is removed. In this way, the OPC pattern area is extracted (see FIG. 19D).

  The OPC pattern area created in this way is binarized by applying a minimum value filter, whereby the OPC filter shown in FIG. 20A is created. FIG. 20B shows the OPC filter applied to the luminance profile shown in FIG. As shown in FIG. 20B, by providing a threshold value, portions corresponding to the defects 163 and 165 to 167 are taken out as defects.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

Configuration diagram of inspection apparatus according to Embodiment 1 (A) Example of luminance data of 3 pixels × 3 pixels (b) Luminance data of 3 pixels × 3 pixels after applying the maximum value filter (c) Luminance of 3 pixels × 3 pixels after applying the minimum value filter data Example of captured mask pattern image Main pattern mask filter in input images A and B The figure which removed the neighborhood of the main pattern from the pattern image in input images A and B OPC mask filter for input images A and B Filtered images in input images A and B (A) High sensitivity defect detection diagram (b) Low sensitivity defect detection diagram (A) The figure which applied the OPC mask filter in the input image A from the highly sensitive defect detection figure in the input images A and B. FIG. (B) The figure which applied the OPC mask filter in the input image B from the highly sensitive defect detection figure in the input images A and B. FIG. FIG. 4 is a diagram illustrating a defect detected in the first embodiment. It is a block diagram which shows the structure of the arithmetic processing part of the processing apparatus used for the test | inspection apparatus which concerns on this invention. FIG. 5 is a schematic configuration diagram of an inspection apparatus according to a second embodiment. It is an example of the captured simultaneous transmission / reflection image of the mask and a minimum value image after the maximum value created from the simultaneous transmission / reflection image. It is a figure of the maximum value image after the minimum value created from the transmission / reflection simultaneous photographing image. It is an image obtained by synthesizing an image obtained by extracting an OPC pattern candidate region and an image obtained by applying a horizontal maximum value filter and a vertical maximum value filter therefrom. It is a figure of the OPC filter in an Example. It is a figure when the OPC filter in an Example is applied to the transmission / reflection simultaneous imaging | photography image. It is sectional drawing in section AA, and the brightness | luminance profile corresponding to the sectional drawing. It is a figure until it produces an OPC filter from the brightness | luminance profile corresponding to the cross section AA. It is the figure when this OPC filter is applied to the figure of the OPC filter in an Example, and the brightness | luminance profile corresponding to the cross section AA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inspection apparatus 10 Photomask 11 Illumination light source 12, 13, 15, 16, 17 Lens 14 Aperture stop 18 Light receiving sensor 20 Processing apparatus 21 Converter 22 Memory 31, 41 Main pattern 32, 42 Scattering bars 33, 35, 45, 46 Convex part 34 Transparent defect 36 Concave part 44 Colored defect 51, 52 Main pattern mask filter 61, 62 OPC mask filter 111 Transmission illumination light source 112 Transmission side filter 113 Drive motor 114 Mirror 115 Objective lens 116 Stage 121 Incident illumination light source 122 Incident side filter 123 Drive motor 124 Beam splitter 125 Objective lens 130 Photomask 131 Light shielding pattern 132 Transmission pattern 141 Lens 142 Detector 150 Processing device 161a, b Main pattern 162a-e Scattering Guba 163,164,167 protrusions 165 point defect 166 defects 231 flare removing section 232 a shading correction section 233 filter generation unit 234 high-sensitivity defect candidate detecting section 235 low-sensitivity defect candidate detection unit 236 defect determination unit

Claims (17)

Comparing the first image and the second image captured with respect to a photomask having a main pattern transferred to the imaging surface and an OPC pattern that performs proximity effect correction on the main pattern; An inspection apparatus that detects and inspects defects provided in the mask,
An illumination light source;
An illumination light source system for collecting light from the illumination light source and emitting it to the sample;
A detector for detecting the luminance of light transmitted through or reflected from the sample out of light emitted from the illumination light source system to the sample in order to capture an image of the sample;
A filter generation unit that generates an OPC filter that masks an OPC region corresponding to an OPC pattern using the first image and the second image;
A high-sensitivity defect candidate detection unit that detects a defect candidate with high sensitivity with respect to a comparison result between the first image and the second image;
A low-sensitivity defect candidate detection unit that detects defect candidates with low sensitivity with respect to a comparison result between the first image and the second image;
An inspection apparatus comprising: a defect determination unit that determines the low-sensitivity defect candidate detected by the low-sensitivity defect candidate detection unit as a defect in the OPC region by using the OPC filter.   The filter creation unit generates a main pattern mask filter that masks the main pattern by performing a process of applying a maximum value filter and a process of applying a minimum value filter to the first image and the second image. The inspection apparatus according to claim 1, wherein the OPC filter is generated based on the main pattern filter.   The inspection apparatus according to claim 2, wherein the process of applying the maximum value filter and the process of applying the minimum value filter are performed a plurality of times by the filter creation unit.   The filter creation unit performs a process of applying the main pattern mask filter to the first image and the second image, and applies to the first image and the second image to which the main pattern filter is applied. The inspection apparatus according to claim 2, wherein the OPC mask filter is generated by performing processing for applying a maximum value filter. Defects provided in the mask in a simultaneous transmission / reflection image captured with respect to a photomask having a main pattern transferred to the imaging plane and an OPC pattern that performs proximity effect correction on the main pattern An inspection device that detects and inspects
A transmission illumination optical system that collects light from the transmission illumination light source and irradiates the mask; and
An epi-illumination optical system that condenses light from an epi-illumination light source and irradiates the mask;
A detector for detecting at least one of transmitted light and reflected light of the sample out of light emitted from the illumination light source system to the sample in order to capture an image of the sample;
The amount of the reflected light reflected by the light-shielding pattern composed of the main pattern and the OPC pattern and detected by the detector transmits the transmission pattern that transmits light and is detected by the detector. A light amount adjusting means for adjusting the light amount of at least one of the illumination light sources so as to be 1.5 times or more the light amount of light;
A filter creation unit that generates an OPC filter that masks an OPC region corresponding to an OPC pattern using a transmission and reflection simultaneous captured image created by the transmitted light and the reflected light;
A high-sensitivity defect candidate detection unit that detects defect candidates with high sensitivity for the transmission and reflection simultaneous captured image;
A low-sensitivity defect candidate detection unit that detects defect candidates with low sensitivity for the transmission and reflection simultaneous captured image;
An inspection apparatus comprising: a defect determination unit that determines the low-sensitivity defect candidate detected by the low-sensitivity defect candidate detection unit as a defect in the OPC region by using the OPC filter.   The filter creation unit generates a main pattern mask filter that masks a main pattern by performing a process of applying a maximum value filter and a process of applying a minimum value filter to the transmission / reflection simultaneous captured image, and The inspection apparatus according to claim 5, wherein the OPC filter is generated based on a pattern filter.   The inspection apparatus according to claim 6, wherein the process of applying the maximum value filter and the process of applying the minimum value filter are performed a plurality of times by the filter creation unit.   The filter creation unit performs a process of applying the main pattern mask filter to the transmission / reflection simultaneous captured image, and performs a process of applying a maximum value filter to the transmission / reflection simultaneous captured image to which the main pattern filter is applied. The inspection apparatus according to claim 6, wherein the OPC mask filter is generated by: Comparing the first image and the second image captured with respect to a photomask having a main pattern transferred to the imaging surface and an OPC pattern that performs proximity effect correction on the main pattern; An inspection method for detecting and detecting defects provided in the mask,
An imaging step of detecting light transmitted through or reflected by the photomask to capture the first image and the second image;
Using the first image and the second image, an OPC mask filter creating step for generating an OPC filter for masking an OPC region corresponding to an OPC pattern;
A high-sensitivity defect candidate detection step for detecting defect candidates with high sensitivity with respect to a comparison result between the first image and the second image;
A low-sensitivity defect candidate detection step for detecting defect candidates with low sensitivity with respect to a comparison result between the first image and the second image;
A defect determination step of determining, in the OPC region, the low sensitivity defect candidate detected by the low sensitivity defect candidate detection unit as a defect by using the OPC filter.   In the OPC mask filter creating step, a main pattern mask that masks the main pattern by performing a process of applying a maximum value filter and a process of applying a minimum value filter to the first image and the second image. The inspection method according to claim 9, wherein a filter is generated.   The OPC mask filter creating step creates the OPC mask filter by performing a process of applying a maximum value filter to an image obtained by masking the main pattern from the first image and the second image. Item 11. The inspection method according to Item 10.   In the OPC mask filter creating step, a process of applying a maximum value filter from an image obtained by masking the main pattern from the first image and the second image using the main pattern mask filter is performed. The inspection method according to claim 10 or 11, wherein a mask filter is generated. Provided on the mask using a transmission / reflection simultaneous photographed image captured with respect to a photomask having a main pattern transferred to the imaging plane and an OPC pattern for performing proximity effect correction on the main pattern. An inspection method for detecting and detecting defects that are present,
Illumination light source so that the amount of reflected light in the light shielding pattern composed of the main pattern and the OPC pattern is 1.5 times or more the amount of transmitted light detected through the transmission pattern that transmits light Adjusting the amount of light,
An imaging step of simultaneously detecting the light transmitted through the photomask and the reflected light to capture the transmission-reflection simultaneous captured image;
An OPC mask filter creating step for generating an OPC filter for masking an OPC region corresponding to an OPC pattern using the transmission / reflection simultaneous photographed image;
A high-sensitivity defect candidate detection step for detecting defect candidates with high sensitivity for the transmission and reflection simultaneous captured image;
Low-sensitivity defect candidate detection step for detecting defect candidates with low sensitivity for the transmission and reflection simultaneous captured image;
A defect determination step of determining, in the OPC region, the low sensitivity defect candidate detected by the low sensitivity defect candidate detection unit as a defect by using the OPC filter.   In the OPC mask filter creation step, a main pattern mask filter for masking the main pattern is generated by performing a process of applying a maximum value filter and a process of applying a minimum value filter to the transmission / reflection simultaneous photographed image. The inspection method according to claim 13.   15. The OPC mask filter creation step creates the OPC mask filter by performing a process of applying a maximum value filter to an image obtained by masking the main pattern from the transmission / reflection simultaneous captured image. Inspection method.   In the OPC mask filter creation step, the OPC mask filter is generated by performing a process of applying a maximum value filter from an image obtained by masking the main pattern from the transmission and reflection simultaneous captured image using the main pattern mask filter. The inspection method according to claim 14 or 15. An inspection step for inspecting a photomask by the inspection method according to any one of claims 9 to 16,
A defect correcting step of correcting defects of the photomask inspected by the inspecting step;
An exposure step of exposing the substrate through the photomask corrected in the defect correction step;
A pattern substrate manufacturing method comprising a developing step of developing the exposed substrate.

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