JP2007170914A - Method and device for inspecting photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method of a photomask capable of accurately and efficiently determining whether flaw has been removed by cleaning treatment with high accuracy, and to provide an inspection device for the photomask. <P>SOLUTION: When a flaw is detected in the first inspection of the photomask 110, the location of the flaw is stored in a flaw data memory part 117. When inspection photomask corresponding to a single sheet is completed, flaw data are recorded on an inspection result recording part 121. After flaw removal treatment (cleaning treatment or the like) has been performed, the second inspection of the photomask is performed. In this second inspection, the first inspection result is read from the inspection result recording part 121, and the image of the part where the flaw is detected by the first inspection and the image of the region, corresponding to the peripheral region of the flaw detected part are acquired by a light-detecting element 114. A flaw inspection part 116 compares the images (image data), acquired by the light detecting element 114 with the criterial image data stored in an image data memory part 115 and presence of flaw is determined. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photomask inspection method and inspection apparatus used for forming patterns of elements, wirings and the like in manufacturing processes of semiconductor devices and magnetic devices.

  In recent years, with higher performance of semiconductor devices (LSIs), further miniaturization of elements and wirings formed on a wafer is required. Normally, many photolithography processes are involved in manufacturing a semiconductor device, and a pattern formed on a photomask (also referred to as a reticle) is transferred to a photoresist film in these photolithography processes. Since the photomask serves as a master for forming elements and wirings on the wafer, it is important that there is no defect. For this reason, a plurality of inspections are performed at the time of creating the photomask. If foreign matter adheres, the foreign matter is washed to remove the foreign matter, and if there is a pattern defect, the pattern is corrected.

  By the way, there are two methods for photomask inspection: die comparison inspection and data comparison inspection. The die comparison inspection is applied when the same pattern is present side by side on the photomask, and these patterns are compared with each other to determine a different portion as a defect. On the other hand, in the data comparison inspection, a defect is detected by comparing a photomask pattern with design data.

  FIG. 1 is a block diagram showing a configuration of a photomask inspection apparatus used for die comparison inspection. This inspection apparatus includes a stage 11, a light source 12, an optical lens (objective lens) 13, a light receiving element 14, an image data storage unit 15, a defect inspection unit 16, a defect information storage unit 17, and a lens control unit. 18, a stage drive unit 19, and a control unit 20.

  The control unit 20 controls the focus of the optical lens 13 via the lens control unit 18 and controls the movement of the stage 11 via the stage drive unit 19. The control unit 20 also controls on / off of the light source 12 and also controls the image data storage unit 15, the defect inspection unit 16, and the defect information storage unit 17.

  The stage 11 is movable in the horizontal direction (X direction and Y direction), and the photomask 10 to be inspected is placed on the stage 11. A light source 12 is disposed below the stage 11, and an optical lens 13 and a light receiving element 14 are disposed above the stage 11. The light output from the light source 12 passes through the stage 11 and irradiates the photomask 10 from below. The light transmitted through the photomask 10 is collected by the optical lens 13 and input to the light receiving element 14. A signal corresponding to the pattern of the photomask 10 is output from the light receiving element 14 as the stage 11 moves.

  The signal output from the light receiving element 14 is input to the image data storage unit 15 or the defect inspection unit 16 as image data. The image data storage unit 15 temporarily stores the image data input from the light receiving element 14 and outputs the image data to the defect inspection unit 16 at a timing according to a signal sent from the control unit 20. Further, the defect inspection unit 16 compares the image data input from the light receiving element 14 with the image data stored in the image data storage unit 15 in accordance with a signal from the control unit 20, and the two image data are different. If there is a point, it is determined as a defect. When it is determined that there is a defect, the coordinates of the defective portion are written as defect information in the defect information storage unit 17. At this time, the coordinates of the defective part are acquired from the control unit 20.

  Next, a die comparison inspection method using the conventional photomask inspection apparatus having the above-described configuration will be described with reference to the schematic diagram shown in FIG. Here, as shown in FIG. 2, it is assumed that the same two patterns (chip A pattern and chip B pattern) exist side by side on the photomask 10.

  First, the photomask 10 is placed on the stage 11, and alignment is adjusted so that the XY direction of the photomask 10 and the XY direction of the stage 11 coincide. Thereafter, an inspection area is set in the control unit 20. In addition, the light source 12 is turned on to adjust the amount of light, and the control unit 10 drives the lens control unit 18 to adjust the focus of the optical lens 13.

  Next, the control unit 20 is instructed to start inspection. Thereby, the control unit 20 controls the stage driving unit 19 to move the stage 11 in the X direction at a constant speed. Then, the light output from the light source 12 according to the transmission part and the light shielding part of the photomask 10 transmits through the photomask 10 or is shielded by the photomask 10, and a signal corresponding thereto is output from the light receiving element 14. When the pattern of the chip A is scanned, the signal output from the light receiving element 14 in accordance with the signal from the control unit 20 is the image data of the pattern of the chip A (hereinafter simply referred to as “image data of the chip A”). ) Is stored in the image data storage unit 15.

  When the scanning of the pattern of the chip A is completed for one line, the scanning of the pattern of the chip B is started. At this time, the signal output from the light receiving element 14 during the scanning of the pattern of the chip B according to the signal from the control unit 20 is the image data of the pattern of the chip B (hereinafter simply referred to as “image data of the chip B”). ) Is directly input to the defect inspection unit 16. The defect inspection unit 16 compares the image data of the chip B output from the light receiving element 14 with the image data of the chip A stored in the image data storage unit 15. And is stored in the defect information storage unit 17 as defect information.

  When the scanning for one line of the chip A pattern and the chip B pattern is completed in this way, the control unit 20 moves the stage 11 in the Y direction by a predetermined pitch via the stage driving unit 19. Further, the image data storage unit 15 is cleared by a signal from the control unit 20. Thereafter, scanning of the next line is started, and defect detection is performed by comparing the image data of chip A and the image data of chip B. In this way, the entire inspection area is inspected.

  Next, data comparison inspection will be described. FIG. 3 is a block diagram showing a configuration of a photomask inspection apparatus used for data comparison inspection. This inspection apparatus includes a stage 31, a light source 32, an optical lens (objective lens) 33, a light receiving element 34, an image data storage unit 35, a defect inspection unit 36, a defect information storage unit 37, and a lens control unit. 38, a stage drive unit 39, a control unit 40, a design data storage unit 42, an image development unit 43, and a data correction unit 44.

  The control unit 40 controls the focus of the optical lens 33 through the lens control unit 38 and controls the movement of the stage 31 through the stage drive unit 39. The control unit 40 controls on / off of the light source 32, and also includes a design data storage unit 42, an image data development unit 43, a data correction unit 44, an image data storage unit 35, a defect inspection unit 36, and a defect information storage unit. 37 is also controlled.

  The stage 31 is movable in the horizontal direction (X direction and Y direction), and the photomask 30 to be inspected is placed on the stage 31. A light source 32 is disposed below the stage 31, and an optical lens 33 and a light receiving element 34 are disposed above the stage 31. The light output from the light source 32 passes through the stage 31 and irradiates the photomask 30 from below. The light transmitted through the photomask 30 is collected by the optical lens 33 and input to the light receiving element 34. The output of the light receiving element 34 is input to the defect inspection unit 36 as image data.

  On the other hand, the design data storage unit 42 stores pattern design data 41 of the photomask 30. The image data development unit 43 develops the design data stored in the design data storage unit 42 to obtain image data. At this time, the image data development unit 43 corrects the image data obtained by developing the design data according to the correction data stored in the data correction unit 44. This correction process corrects the difference between the design data and the pattern actually formed on the mask from the design data. For example, even if the design data is rectangular pattern data as shown in FIG. 4A, the pattern actually formed on the photomask 30 has a curved corner as shown in FIG. 4B. (Arc shape). If the image data is not corrected, the corner of the pattern shown in FIG. 4B is determined to be defective when the image data obtained by developing the design data is compared with the image data obtained from the actual pattern. Resulting in. In order to avoid such a problem, it is necessary to correct image data obtained by developing the design data.

  The image data storage unit 35 reads the image data for each line from the image data development unit 43 in accordance with a signal from the control unit 40 and outputs it to the defect inspection unit 36. The defect inspection unit 36 compares the image data input from the light receiving element 34 with the image data stored in the image data storage unit 35 to determine the presence or absence of a defect. When it is determined that there is a defect, the coordinates of the defective part are written in the defect information storage unit 37 as defect information. The coordinates of the defective part are acquired from the control unit 40.

  Next, a data comparison inspection method using the conventional photomask inspection apparatus having the above-described configuration will be described.

  First, the photomask 30 is placed on the stage 31 and alignment is adjusted so that the XY direction of the photomask 30 and the XY direction of the stage 31 coincide. Thereafter, an inspection area is set in the control unit 40. Further, the light source 32 is turned on to adjust the amount of light, and the control unit 40 drives the lens control unit 38 to adjust the focus of the optical lens 33.

  On the other hand, design data 41 is stored in advance in the design data storage unit 42. The image data development unit 43 reads design data from the design data storage unit 42 in response to a signal from the control unit 40 and develops the design data to obtain image data. At this time, the image data development unit 43 corrects the image data based on the correction data stored in the data correction unit 44. The image data storage unit 35 reads out and stores the image data for the first line from the image data development unit 43 based on the signal from the control unit 40.

  Next, the control unit 40 is instructed to start inspection. Accordingly, the control unit 40 controls the stage driving unit 39 to move the stage 31 at a constant speed in the X direction. Then, the light output from the light source 32 according to the transmission part and the light shielding part of the photomask 30 is transmitted through the photomask 30 or shielded by the photomask 30, and a signal corresponding to the light is output from the light receiving element 34. This signal is input to the defect inspection unit 36 as image data.

  The defect inspection unit 36 compares the image data input from the image data storage unit 35 with the image data input from the light receiving element 34 in accordance with a signal from the control unit 40 and determines the presence or absence of a defect. When it is determined that there is a defect, the coordinates of the defective part are written in the defect information storage unit 37 as defect information.

  When the inspection for one line is completed, the image data storage unit 35 is cleared based on the signal from the control unit 40, and then the image data for the next one line is read from the image data development unit 43 and stored in the image data. Stored in the unit 35. Further, the control unit 40 controls the stage driving unit 39 to move the stage 31 in the Y direction by a predetermined pitch. Next, scanning of the next line is started, and defect detection is performed by comparing the image data obtained from the pattern of the photomask 30 with the image data obtained from the design data 41. In this way, the entire inspection area is inspected.

  In the data comparison inspection, the image data obtained from the pattern of the photomask 30 and the image data obtained from the design data 41 are compared. Therefore, unlike the die comparison inspection, the same pattern does not exist in the photomask 30 side by side. In some cases, inspection is possible.

  Photomasks in which defects are detected by die comparison inspection or data comparison inspection are classified into defects caused by adhesion of foreign matters and defects caused by pattern defects by an operator. In other words, the operator displays an image of the defective portion on the display device attached to the inspection apparatus, and from the state of the defective portion and the size of the defective portion, whether the defect is due to adhesion of foreign matter or a defective pattern. Determine. At this time, not only observation with transmitted light but also observation with reflected light is performed.

  The photomask determined to be a defect due to the adhesion of foreign matter is sent to the cleaning process and cleaned, and the photomask determined to be a defect due to a pattern defect is sent to the correction process to correct the pattern. Note that a photomask that is determined to be a defect due to the adhesion of foreign matter is again inspected by a photomask inspection apparatus after the cleaning process, and the presence or absence of a defect is determined. Here, when a defect is detected again, it is sent to a correction process and the foreign matter is removed by a physical method. As a result, if the pattern needs to be corrected, the pattern is corrected.

  By the way, with the recent increase in the density of semiconductor devices, the photomask pattern tends to be further miniaturized, and it is required to detect minute defects even in the inspection of the photomask. In response to such demands, the defect detection capability of the inspection apparatus is improved, and fine defects can be detected. However, when the size of the defect is fine, it is difficult for an operator (operator) to observe the defective portion and determine whether the defect is due to the adhesion of foreign matter or a pattern defect.

  In order to reduce the load on the operator, it is conceivable that all the photomasks in which defects are detected in the inspection are sent to the correction process, and the foreign substances are removed in the correction process even in the case of defects due to the adhesion of foreign substances. However, since it is necessary to individually process the photomasks one by one in accordance with the state of the defect in the correction process, the processing time becomes enormous and is not realistic.

  In Patent Document 1, only a photomask that is sure to be a defective pattern among the photomasks in which defects are detected is sent to the correction process for correction, and all others are sent to the cleaning process for cleaning. It has been proposed to do.

  FIG. 5 is a flowchart showing a photomask inspection / correction process according to Patent Document 1. First, in step S11, inspection by the above-described photomask inspection apparatus is performed. In step S12, the presence / absence of a defect is determined. When it is determined that there is no defect, the photomask inspection / correction process is terminated. However, when it is determined in step S12 that there is a defect, the process proceeds to step S13.

  In step S13, the operator observes the image of the defective portion displayed on the display device, and determines whether the defect is due to a pattern defect or other causes. When it is certain that the defect is caused by a pattern defect, the process proceeds to step S17 and correction processing is executed. On the other hand, if it is determined in step S13 that the defect is due to the attachment of foreign matter, or if it is not possible to determine whether the defect is due to the attachment of foreign matter or a pattern failure, the process proceeds to step S14.

  In step S14, a cleaning process is performed on the photomask. Then, it transfers to step S15 and test | inspects by a photomask inspection apparatus again. In step S16, the presence / absence of a defect is determined. When it is determined that there is no defect, the photomask inspection / correction process is terminated. However, when it is determined in step S16 that there is a defect, the process proceeds to step S17 to execute a correction process.

  In Patent Document 2, a defective portion of a photomask after cleaning processing (a portion where a defect is detected in the first inspection) is observed using a SEM (scanning electron microscope) or a photomask inspection apparatus, and foreign matter is removed. It has been proposed to determine whether or not. In this case, since the coordinates of the defective part are known at the time of the first inspection, the observation position is moved to the position of the defect detected by the first inspection by inputting the coordinates to the SEM or the photomask inspection apparatus. It is easy to make.

  FIG. 6 is a flowchart showing photomask inspection / correction processing according to Patent Document 2. First, in step S21, inspection by the above-described photomask inspection apparatus is performed. In step S22, the presence / absence of a defect is determined. When it is determined that there is no defect, the photomask inspection / correction process is terminated. However, when it is determined in step S22 that there is a defect, the process proceeds to step S23.

  In step S23, the operator observes the image of the defective portion displayed on the display device, and determines whether the defect is due to a defective pattern or due to adhesion of foreign matter. If it is determined that the pattern is defective, the process proceeds to step S26 to correct the pattern. On the other hand, if it is determined in step S23 that the defect is due to the adhesion of foreign matter, the process proceeds to step S24.

  In step S24, a cleaning process is performed on the photomask. Thereafter, the process proceeds to step S25. In step S25, using the SEM or the above-described photomask inspection apparatus, the coordinates of the portion determined to be defective in the first inspection are input, and the position of the coordinates and the image of the surrounding area are displayed on the display device. To determine the presence or absence of defects. The presence or absence of this defect is determined by observing the screen displayed on the display device by the operator. If it is determined that there is no defect, the photomask inspection / correction process is terminated. If it is determined that there is a defect, the process proceeds to step S26 to correct the defect portion.

In this method, by inputting the coordinates of the defective portion detected in the first inspection (step S21) to the SEM or the photomask inspection apparatus, only the portion where the defect is detected in the first inspection is selectively observed. Can do. Therefore, although it is necessary for the operator himself to determine whether or not there is a defect, the inspection time can be greatly reduced as compared with the case where the entire photomask is inspected by the photomask inspection apparatus.
Japanese Patent Laid-Open No. 06-67407 JP 2003-185592 A

  However, the present inventors consider that the conventional photomask inspection method described above has the following problems. That is, in the method described in the cited document 1, all of the photomasks in which defects are detected, except those that are surely defective in pattern, are cleaned and reinspected (inspection in step S15). The number of photomasks that need to be increased. Usually, the inspection of the photomask takes 5 to 6 hours per sheet (when the size of the inspection area is about 100 mm × 100 mm). Therefore, if the number of photomasks that need to be reinspected increases, from the viewpoint of throughput and cost. It becomes a problem.

  In the method described in the cited document 2, there is a possibility that a determination error occurs because the operator's vision is used to confirm whether or not the foreign matter has been removed, and it cannot be said that the reliability is sufficient.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a photomask inspection method and inspection apparatus capable of determining whether or not a defect has been removed by a cleaning process with high accuracy and efficiency.

  The above-described problems include a first step of acquiring an image of a photomask by an image acquisition unit, and detecting defects by comparing with image data serving as a reference by a defect inspection unit, and defects detected in the first step. A second step of storing the position in the defect information storage unit as defect information, and a third step of recording the defect information stored in the second step in the inspection result recording unit in association with a unique identification code for each photomask. A step of performing a defect removal process, a step of reading the defect information recorded in the third step, and a position of the defect detected in the first step from the photomask after the defect removal process; And a fifth step of acquiring an image of only the peripheral area by the image acquisition unit and determining the presence or absence of a defect by comparing with image data serving as a reference by the defect inspection unit. It is solved by a method of inspection.

  In addition, the above-described problems include a stage on which a photomask is placed, an image acquisition unit that obtains an image of the photomask placed on the stage, and first image data that serves as a reference for defect detection. The image data storage unit to store, the image data acquired by the image acquisition unit as second image data, the second image data and the first image data stored in the image data storage unit, A defect inspection unit that detects defects by comparing the defect detection unit, a defect information storage unit that stores the position of the defect detected by the defect inspection unit as defect information, and defect information of at least one photomask. An inspection result recording unit for recording in association with a unique identification code, and a control unit for controlling the image acquisition unit, the image data storage unit, the defect inspection unit, and the inspection result recording unit. The control unit controls the image acquisition unit based on the defect information recorded in the inspection result recording unit when re-inspecting the photomask in which the defect information is recorded in the inspection result recording unit. An image of only the position of the defect detected in the previous inspection and its peripheral area is acquired from the mask and input to the defect inspection unit as the second image data, and the defect detection unit inputs the second This is solved by a photomask inspection apparatus that compares the image data with the first image data stored in the image data storage unit to determine the presence or absence of a defect.

  In the present invention, when a defect is detected in the first inspection of the photomask, the position of the defect is stored in the defect information storage unit as defect information. When the inspection of one photomask is completed, the defect information of the photomask is recorded in the inspection result recording unit in association with the identification code unique to the photomask.

  Thereafter, defect removal processing (for example, cleaning processing) is performed, and a second inspection is performed. In this second inspection, the first inspection result is read from the inspection result recording unit, and an image of a region where a defect is detected in the first inspection from the photomask and a region corresponding to the surrounding region is read by the image acquisition unit. The defect inspection unit compares the acquired image (image data) with the reference image data.

  As described above, in the present invention, since only the portion in which the defect is detected in the first inspection process is inspected in the second inspection process, the inspection time is remarkably shortened compared with the method of reinspecting the entire photomask. The In the present invention, the defect detection unit automatically compares the image data acquired from the photomask and the reference image data even in the second inspection process, so that human error by the operator is avoided. There is no risk of occurrence and the reliability of inspection is high.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 7 is a block diagram showing the configuration of the photomask inspection apparatus according to the first embodiment of the present invention. This embodiment shows an example in which the present invention is applied to an inspection apparatus for die comparison inspection.

  This inspection apparatus includes a stage 111, a light source 112, an optical lens (objective lens) 113, a light receiving element 114, an image data storage unit 115, a defect inspection unit 116, a defect information storage unit 117, and a lens control unit. 118, a stage drive unit 119, a control unit 120, and an inspection result recording unit 121.

  The control unit 120 controls the focus of the optical lens 113 via the lens control unit 118 and controls the movement of the stage 111 via the stage drive unit 119. The control unit 120 also controls on / off of the light source 112 and also controls the image data storage unit 115, the defect inspection unit 116, the defect information storage unit 117, and the inspection result recording unit 121.

  The stage 111 is movable in the horizontal direction (X direction and Y direction), and the photomask 110 to be inspected is placed on the stage 111. A light source 112 is disposed below the stage 111, and an optical lens 113 and a light receiving element 114 are disposed above the stage 111. The light output from the light source 112 passes through the stage 111 and irradiates the photomask 110 from below. The light transmitted through the photomask 110 is collected by the optical lens 113 and input to the light receiving element 114. A signal corresponding to the pattern of the photomask 110 is output from the light receiving element 114 as the stage 111 moves.

  The signal output from the light receiving element 114 is input to the image data storage unit 115 or the defect inspection unit 116 as image data. The image data storage unit 115 temporarily stores the image data input from the light receiving element 114 and outputs the image data to the defect inspection unit 116 at a timing according to a signal sent from the control unit 120. Further, the defect inspection unit 116 compares the image data input from the light receiving element 114 with the image data stored in the image data storage unit 115 in accordance with a signal from the control unit 120, and the two image data are different. If there is a point, it is determined as a defect. When it is determined that there is a defect, the coordinates of the defective portion are written as defect information in the defect information storage unit 117. At this time, the coordinates of the defective part are acquired from the control unit 120.

  In the inspection result recording unit 121, the defect information stored in the defect information storage unit 117 is stored in association with a unique identification code (for example, a serial number) for each photomask 110. The inspection result recording unit 121 can record defect information of a plurality of photomasks.

  In the present embodiment, the image acquisition unit that acquires the image of the photomask 110 includes a light source 112, an optical lens 113, a light receiving element 114, and a stage drive unit 119.

  Next, a die comparison inspection method using the photomask inspection apparatus having the above-described configuration will be described.

  In the first inspection, the photomask 110 is inspected as in the conventional inspection apparatus described above. That is, the photomask 110 is placed on the stage 111, and the alignment is adjusted so that the XY direction of the photomask 110 and the XY direction of the stage 111 coincide. Then, one of the two identical patterns is scanned and a signal (image data) output from the light receiving element 114 is accumulated in the image data storage unit 115, and then the other pattern is scanned while the light receiving element 114 is scanned. The defect inspection unit 116 compares the signal (image data) output from the image data and the image data stored in the image data storage unit 115 to determine the presence or absence of a defect. When it is determined that there is a defect, the defect information storage unit 117 stores the coordinates of the defective part as defect information.

  When the inspection of the photomask 110 is completed in this way, the control unit 120 records the defect information stored in the defect information storage unit 117 in the inspection result recording unit 121 in association with the identification code unique to the inspected photomask 110. To do. The photomask 110 determined to have a defect is classified into one sent to the cleaning process and one sent to the correction process by the operator.

  FIG. 8 is a flowchart showing an inspection method (second inspection) of the washed photomask. With reference to FIG. 8, the inspection method of this embodiment will be described.

  First, in step S31, preparation for inspection is performed. That is, the photomask 110 that has been subjected to cleaning processing (defect removal processing) is placed on the stage 111, and alignment is adjusted so that the XY direction of the photomask 110 and the XY direction of the stage 111 coincide. Thereafter, the identification code of the photomask 110 to be inspected is input to the control unit 120. Further, the light amount of the light source 112 and the focus of the optical lens 113 are adjusted.

  Next, the control unit 120 is instructed to start inspection. Accordingly, the process proceeds to step S <b> 32, and the control unit 120 reads out defect information in the first inspection from the inspection result recording unit 121. In step S33, the stage 111 is moved to a defective portion of the chip A (a position corresponding to a position where the defect is detected in the first inspection).

  Next, the process proceeds to step S34, and the pattern of the defective portion of the chip A is scanned as shown in FIG. At this time, in the present embodiment, an image of a square region 126 of 512 pixels × 512 pixels centering on the defective portion is acquired with 256 gradations. In the present embodiment, the size of one pixel is about 90 to 100 nm. Image data acquired from the pattern of the chip A (hereinafter simply referred to as “image data of the chip A”) is stored in the image data storage unit 115. Note that reference numeral 125 in FIG. 9 virtually indicates a defect detected in the first inspection.

  Next, the process proceeds to step S35, and the stage 111 is moved to a defective portion of the pattern of the chip B (a position corresponding to a position where a defect is detected in the first inspection). In step S36, the pattern of the defective portion of the chip B is scanned. Also in this case, an image of a square region 126 of 512 pixels × 512 pixels centering on the defective portion is acquired with 256 gradations. The image data of the pattern of the chip B (hereinafter simply referred to as “chip B image data”) is stored in the defect inspection unit 116.

  In step S37, the defect inspection unit 116 compares the image data of chip A stored in the image data storage unit 115 with the image data of chip B stored in the defect inspection unit 116. To determine the presence or absence of defects. If there is a difference between the two image data, it is determined that there is a defect, and the position (coordinates) of the defective portion and the image data around the defective portion are stored in the defect information storage unit 117.

  Next, in step S <b> 38, it is determined whether or not the inspection of all defective portions of the photomask 110 recorded in the inspection result recording unit 121 has been completed. If it is determined that the process has not ended, the process returns to step S32 and the above-described process is repeated. In this way, in this embodiment, only the portion where the defect is detected in the first inspection is inspected again.

  Since the photomask 110 in which the defect is detected in the second inspection has a defect that cannot be removed by cleaning, the photomask 110 is subjected to correction processing in the correction process.

  In the present embodiment, as described above, in the second inspection performed after the cleaning process, the entire photomask 110 is not inspected, but a portion determined as a defect by the first inspection and its surroundings. Only the area is automatically inspected by the inspection device. Therefore, the inspection time is remarkably shortened as compared with the case of reinspecting the entire photomask. For example, in the conventional inspection method, it took 5 to 6 hours to fully inspect a photomask having an inspection area size of 100 mm × 100 mm. On the other hand, according to this embodiment, even if there are 50 defects in one photomask, the time required for the inspection is about 10 minutes. Further, in the second and subsequent inspections, since the portion determined to be defective by the first inspection is not extracted from the inspection data in all areas, the speed at which the inspection apparatus accesses the data is also increased.

  Further, according to the present embodiment, since the presence or absence of a defect is automatically determined by the inspection apparatus, there is no possibility that an artificial error occurs and the reliability of the inspection is high.

  In this embodiment, the defect information storage unit 117 that stores defect information of one photomask and the inspection result recording unit 121 that stores defect information of a plurality of photomasks are individually provided. The defect information storage unit 117 and the inspection result recording unit 121 may be configured integrally.

(Modification of the first embodiment)
In the first embodiment described above, a case has been described in which image data acquisition, image data comparison, and defect presence / absence determination processes are sequentially repeated for each defective portion. However, image data of all defective portions is acquired. After that, the comparison of the image data and the determination of the presence / absence of a defect may be collectively performed. This eliminates the need to wait for the start of movement of the stage 111 until the comparison of the image data and the determination of the presence / absence of a defect are completed, and the time required for inspection can be further shortened.

  In the first embodiment, image data of both the pattern of the chip A and the pattern of the chip B is acquired in the second inspection. When a defect is detected in the first inspection, information indicating which chip pattern has a defect and image data of a chip having no defect in a part corresponding to the defective part (chip A pattern has a defect) When the chip B pattern is defective, the chip B pattern image data is recorded in the inspection result recording unit 121. Thereby, the process of acquiring the image data of the pattern of one chip can be omitted. FIG. 10 is a flowchart showing the inspection method at this time.

  First, in the same manner as in the first embodiment described above, preparation for inspection is performed in step S41, and in step S42, defect information (defect portion coordinates, defect pattern on which chip is defective) from the inspection result recording unit 121 in the first inspection. Information indicating whether or not there is, and defect-free image data). At this time, the control unit 120 transfers the corresponding defect-free image data from the inspection result recording unit 121 to the image data storage unit 115.

  Next, the process proceeds to step S43, and the control unit 120 moves the stage to a position (defect portion) where a defect is detected in the first inspection. In step S44, a predetermined range (for example, a range of 512 pixels × 512 pixels) around the defective portion is scanned, and a signal output from the light receiving element 114 is stored in the defect inspection unit 116 as image data. .

  In step S45, the defect inspection unit 116 compares the defect-free image data stored in the image data storage unit 115 with the image data (image data acquired from the photomask) stored in the defect inspection unit 116. Then, the presence or absence of defects is determined. When it is determined that there is a defect, the coordinates of the defective part are stored in the defect information storage unit 117.

  Next, in step S46, it is determined whether or not all inspections for defective portions of the photomask 110 recorded in the inspection result recording unit 121 have been completed. If it is determined that the process has not been completed, the process returns to step S42 and the above-described process is repeated.

  According to this method, the number of movements of the stage 111 is reduced, and the inspection time can be further shortened as compared with the first embodiment described above.

(Second Embodiment)
FIG. 11 is a block diagram showing a configuration of a photomask inspection apparatus according to the second embodiment of the present invention. This embodiment shows an example in which the present invention is applied to an inspection apparatus for data comparison inspection.

  This inspection apparatus includes a stage 131, a light source 132, an optical lens (objective lens) 133, a light receiving element 134, an image data storage unit 135, a defect inspection unit 136, a defect information storage unit 137, and a lens control unit. 138, a stage drive unit 139, a control unit 140, a design data storage unit 142, an image development unit 143, a data correction unit 144, and an inspection result recording unit 145.

  The control unit 140 controls the focus of the optical lens 133 via the lens control unit 138 and controls the movement of the stage 131 via the stage drive unit 139. In addition, the control unit 140 controls on / off of the light source 132, and the design data storage unit 142, the image data development unit 143, the data correction unit 144, the image data storage unit 135, the defect inspection unit 136, and the defect information storage unit. 137 and the inspection result recording unit 145 are also controlled.

  The stage 131 is movable in the horizontal direction (X direction and Y direction), and the photomask 130 to be inspected is disposed on the stage 131. A light source 132 is disposed below the stage 131, and an optical lens 133 and a light receiving element 134 are disposed above the stage 131. The light output from the light source 132 passes through the stage 131 and irradiates the photomask 130 from below. The light transmitted through the photomask 130 is collected by the optical lens 133 and input to the light receiving element 134. The output of the light receiving element 134 is input to the defect inspection unit 136 as image data.

  On the other hand, the design data storage unit 142 stores design data 141 of the pattern of the photomask 130. The image data expansion unit 143 expands the design data stored in the design data storage unit 142 to obtain image data. At this time, the image data development unit 143 corrects the image data obtained by developing the design data in accordance with the correction data stored in the data correction unit 144. This correction processing corrects the difference between the design data and the pattern actually formed on the photomask 130 from the design data (see FIGS. 2A and 2B).

  The image data storage unit 135 reads image data for each line from the image data development unit 143 in accordance with a signal from the control unit 140 and outputs the read image data to the defect inspection unit 136. The defect inspection unit 136 compares the image data input from the light receiving element 134 with the image data stored in the image data storage unit 135 to determine the presence / absence of a defect. When it is determined that there is a defect, the coordinates of the defective part are written in the defect information storage unit 137 as defect information. The coordinates of the defective part are acquired from the control unit 140.

  In the inspection result recording unit 145, the defect information stored in the defect information storage unit 137 is stored in association with an identification code (for example, a serial number) unique to each photomask 130. The inspection result recording unit 145 can record defect information of a plurality of photomasks.

  Next, a data comparison inspection method using the photomask inspection apparatus configured as described above will be described.

  In the first inspection, the photomask 130 is inspected in the same manner as the conventional inspection apparatus described above. That is, the photomask 130 is placed on the stage 131, and alignment is adjusted so that the XY direction of the photomask 130 and the XY direction of the stage 131 coincide. Then, the image data obtained by developing the design data 141 stored in the design data storage unit 142 by the image data development unit 143 is compared with the image data obtained by scanning the photomask 130 to determine the defect. Determine presence or absence. When it is determined that there is a defect, the position coordinates of the defective portion are stored in the defect information storage unit 137 as defect information.

  When the inspection of the photomask 130 is completed in this way, the control unit 140 records the defect information stored in the defect information storage unit 137 in the inspection result recording unit 145 in association with the identification code unique to the inspected photomask 130. To do. The photomask 130 determined to have a defect is classified into one sent to a cleaning process and one sent to a correction process by an operator (operator).

  FIG. 12 is a flowchart showing an inspection method (second inspection) of a washed photomask. With reference to FIG. 12, the inspection method of this embodiment will be described.

  First, in step S51, preparation for inspection is performed. That is, the washed photomask 130 is placed on the stage 131, and alignment is adjusted so that the XY direction of the photomask 130 and the XY direction of the stage 131 coincide. The design data storage unit 142 stores design data of the inspection target photomask 130. Thereafter, the identification code of the photomask 130 to be inspected is input to the control unit 140. Further, the light amount of the light source 132 and the focus of the optical lens 131 are adjusted.

  Next, the control unit 140 is instructed to start inspection. As a result, the process proceeds to step S52, and the control unit 140 reads defect information in the first inspection from the inspection result recording unit 145. In step S 53, the image data of the defective portion (the position corresponding to the position where the defect is detected in the first inspection) is read from the image data development unit 143 and stored in the image data storage unit 135. Here, image data of a square area of 512 pixels × 512 pixels centering on the defective portion is stored. In this embodiment, the size of one pixel is about 90 to 100 nm.

  Next, in step S54, the stage 131 is moved to the position of the defective part. Then, the process proceeds to step S55, and the pattern of the defective portion of the photomask 130 is scanned. Also in this case, image data of a square area of 512 pixels × 512 pixels centering on the defective portion is acquired. Image data acquired by the light receiving element 134 is stored in the defect inspection unit 136.

  Next, the process proceeds to step S56, where the defect inspection unit 136 stores image data (image data obtained from the design data) stored in the image data storage unit 135 and image data stored in the defect inspection unit 136 (image data). Image data acquired from the photomask 130) and the presence or absence of a defect is determined. If there is a difference between the two image data, it is determined that there is a defect, and the coordinates of the defective part are stored in the defect information storage unit 137.

  Next, in step S57, it is determined whether or not the inspection of all defective portions of the photomask 130 recorded in the inspection result recording unit 145 has been completed. If it is determined that the process has not ended, the process returns to step S52, and the above-described processing is repeated. In this way, in this embodiment, only the portion where the defect is detected in the first inspection is re-inspected.

  Also in the present embodiment, in the second inspection performed after the cleaning process, the entire photomask 130 is not inspected, but only the portion determined as a defect by the first inspection and the surrounding area are inspected. Inspect automatically. Therefore, the inspection time is remarkably shortened compared with the case where the entire photomask is inspected.

  Further, according to the present embodiment, since the presence or absence of a defect is automatically determined by the inspection apparatus, there is no possibility that an artificial error occurs and the reliability of the inspection is high.

  Also in this embodiment, a defect information storage unit 137 that stores defect information of one photomask and an inspection result recording unit 145 that stores defect information of a plurality of photomasks are individually provided. However, the defect information storage unit 137 and the inspection result recording unit 145 may be integrally configured.

(Modification of the second embodiment)
In the second embodiment described above, a case has been described where image data acquisition, image data comparison, and determination of the presence / absence of a defect are repeated in order for each defective portion. After the acquisition, comparison of image data and determination of presence / absence of a defect may be performed collectively. This eliminates the need to wait for the start of movement of the stage 131 until the comparison of the image data and the determination of the presence / absence of the defect are completed, and the time required for the inspection can be further shortened.

  In the second embodiment described above, the design data is expanded in the second inspection and the image data obtained thereby is corrected. When a defect is detected in the first inspection, Image data (corrected image data) corresponding to the defective portion may be acquired from the image data development unit 143 and stored in the inspection result storage unit 145. As a result, the process of developing the design data and the process of correcting the image data obtained thereby are not required in the second inspection, and the load on the inspection apparatus is reduced.

(Third embodiment)
A photomask inspection method according to the third embodiment will be described below.

  In the first and second embodiments, when there is a defect due to adhesion of foreign matter and a defect due to pattern failure in one photomask, a cleaning process (defect removal process) is performed after the first inspection is completed, The defective part is inspected in the second inspection. In this case, in the second inspection, not only the part to which the foreign matter has adhered but also the pattern defective part is inspected. In the case of a defect due to a pattern defect, since the defect cannot be removed by cleaning, it is useless to inspect the defective part due to the pattern defect in the second inspection (inspection after the cleaning process).

  Therefore, in the inspection method according to the present embodiment, the second inspection is omitted for a portion that has been found to be a defect due to a pattern defect in the first inspection. The present embodiment is realized by using the die comparison inspection inspection apparatus described in the first embodiment or the data comparison inspection inspection apparatus described in the second embodiment. Here, for convenience of explanation, it is assumed that an inspection apparatus for die comparison inspection having the configuration shown in FIG. 7 is used.

  13 and 14 are flowcharts showing a photomask inspection method according to the third embodiment of the present invention. FIG. 13 shows a flowchart at the time of the first inspection, and FIG. 14 shows a flowchart at the time of the second inspection (after the cleaning process). First, the first inspection will be described with reference to the flowchart of FIG. 13 and the block diagram of FIG.

  First, in step S61, the inspection apparatus performs the first inspection of the photomask 110 as described in the first embodiment. Thereafter, in step S62, the operator (operator) determines the type of defect while viewing the image of the defective portion. That is, in the case of a defect that needs to be corrected such as a pattern defect, the process proceeds to step S63, and the flag “D” is added to the defect information stored in the defect information storage unit 117. If the defect requires cleaning such as adhesion of foreign matter, the process proceeds to step S64, and a flag “P” is added to the defect information stored in the defect information storage unit 117. Further, if the defect is not a defect but is a pseudo-defect determined by the inspection apparatus, the process proceeds to step S65, and the flag “F” is added to the defect information stored in the defect information storage unit 117. The pseudo defects are those in which, for example, as shown in FIGS. 2A and 2B, the difference between the design data generated in the photomask forming process and the actual pattern is determined as a defect. .

  Thereafter, in step S66, it is determined whether or not flags have been added to all defective portions. If there is a defective portion to which no flag is added, the process returns to step S62 and the above-described processing is executed.

  In this way, any one flag of “D”, “P”, and “F” is added to all the defect information of the photomask 110. The defect information is recorded in the inspection result recording unit 121 in association with an identification code (such as a serial number) unique to the photomask 110.

  Next, an inspection method for the second inspection (inspection after the cleaning process) will be described with reference to the flowchart of FIG. 14 and the block diagram of FIG.

  First, in step S <b> 71, after the photomask 110 is placed on the stage 111, defect information of the photomask 110 is read from the inspection result recording unit 121. In step S72, the control unit 120 determines whether the flag added to the defect information is “P”. When the flag is other than “P” (in other words, when the flag is “D” or “F”), that is, when the defect is determined not to be a defect due to the adhesion of foreign matter in the first inspection, the process returns to step S71. Read next defect information.

  On the other hand, if it is determined in step S72 that the flag is “P”, the process proceeds to step S73. Then, the control unit 120 moves the stage 111 to scan the defective portion, and determines whether or not there is a defect in step S74. If it is determined in step S74 that there is a defect, that is, if the defect cannot be removed by cleaning, the process proceeds to step S75, where the defect information flag is changed to “D” and stored in the defect information storage unit 117. On the other hand, if it is determined in step S74 that there is no defect, that is, if the defect is removed by cleaning, the process proceeds to step S76, where the defect information flag is changed to “F” and stored in the defect information storage unit 117. .

  Next, the process proceeds to step S77, and the control unit 120 determines whether or not the inspection of all defective portions has been completed. If it is determined in step S77 that inspection of all defective portions has not been completed, the process returns to step S71 and the above-described processing is repeated. On the other hand, if it is determined in step S77 that the inspection of all defective portions has been completed, the processing is completed. In this way, in the second inspection, only the defect portion to which the “P” flag is added is inspected, and the defect information flag is changed to “D” or “F” according to the result.

  In the present embodiment, only the defective portion to which the flag “P” is added in the first inspection, that is, only the portion where the defect may be removed by cleaning is re-inspected. Compared with this, the inspection time can be further shortened.

  In the present embodiment, after completion of the second inspection (inspection after the cleaning process), the flag added to the defective portion is “D” indicating that the defect needs to be corrected, or correction is performed. One of the flags “F” indicating an unnecessary defect (such as a pseudo defect). Therefore, in the correction process, only the defect to which the flag “D” is added needs to be corrected, and the correction process can be made efficient.

(Fourth embodiment)
A photomask inspection method according to the fourth embodiment of the present invention will be described below.

  In the first and second embodiments, the presence / absence of a defect is determined by comparing image data of a relatively wide range (512 pixels × 512 pixels) centering on a defective portion. This is because, when two images are compared, it is necessary to perform pattern matching processing to make the patterns of the two images exactly match. In this case, if the pattern formed by performing complex correction such as optical proximity correction (OPC) is within the comparison range, the difference between the design data and the actually formed pattern is defective. There is a risk of being detected as a (pseudo defect).

  Therefore, in this embodiment, when a defect is detected in the first inspection, the coordinates of the center of gravity (center point) of the defect are stored as defect information, and the periphery of the defect portion (defect portion) is stored in the second inspection. Pattern matching processing is performed using the data of a relatively wide range of image data (not including the image), and then the image data of the relatively narrow range centering on the center of gravity of the defective portion (the image of the defective portion) is compared. Determine if there is a defect. The present embodiment is realized by using the die comparison inspection inspection apparatus described in the first embodiment or the data comparison inspection inspection apparatus described in the second embodiment. Here, for convenience of explanation, it is assumed that an inspection apparatus for die comparison inspection having the configuration shown in FIG. 7 is used.

  FIGS. 15A to 15E are schematic views showing a photomask inspection method according to this embodiment. In this embodiment, when a defect is detected in the first inspection, the center of gravity (center point) of the defective portion is obtained, and a rectangular area of ± 5 pixels in the X direction and ± 5 pixels in the Y direction is determined from the center of gravity. The position is set as a defect area and recorded in the inspection result recording unit 121.

  FIG. 15A shows an example of an image when a defect is detected in the first inspection. As shown in FIG. 15 (a), when a defect is detected in the first inspection, the range of ± 5 pixels in the X direction and ± 5 pixels in the Y direction is centered on the center of gravity of the defective portion. Is stored in the defect information storage unit 118. When the inspection of the photomask 110 is completed, defect information (including defect area information) stored in the defect information recording unit 118 is recorded in the inspection result recording unit 121 in association with an identification code unique to the photomask. .

  In the second inspection, image data of an area of 512 pixels × 512 pixels corresponding to the defective portion is acquired based on the defect information read from the inspection result recording unit 121 (see FIG. 9). FIG. 15B shows the image data of the defective portion acquired from the pattern of the chip A, and FIG. 15C shows the image data of the defective portion acquired from the pattern of the chip B. Then, pattern matching processing is performed using a portion other than the defect area (a rectangular area indicated by a broken line in the drawing) of these image data. The pattern of both images is completely matched.

  Next, the control unit 120 extracts defect area image data from the image data acquired from the chip A pattern and the image data acquired from the chip B pattern, and compares the image data of the defect areas. FIG. 15D is a diagram showing the image data of the defective area extracted from the image data of FIG. 15B, and FIG. 15E is the image data of the defective area extracted from the image data of FIG. FIG. The control unit 120 determines that there is a defect when there is a difference between the image data of these two defective areas, and determines that there is no defect when there is no difference.

  In the present embodiment, in addition to obtaining the same effect as in the first embodiment, the presence / absence of a defect is determined by comparing image data in an extremely small area (defect area) of the defective portion. There is an effect that pattern comparison is not performed and erroneous determination due to a pseudo defect or the like can be avoided.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Additional remark 1) The 1st process which acquires the image of a photomask with an image acquisition part, and detects a defect compared with the image data used as a reference by a defect inspection part,
A second step of storing the position of the defect detected in the first step in the defect information storage unit as defect information;
A third step of recording the defect information stored in the second step in an inspection result recording unit in association with a unique identification code for each photomask;
A fourth step of performing defect removal processing;
The defect information recorded in the third step is read, and an image of only the position of the defect detected in the first step and its peripheral region is acquired from the photomask after the defect removal processing by the image acquisition unit. And a fifth step of determining the presence or absence of a defect by comparing with image data serving as a reference by the defect inspection unit.

  (Supplementary note 2) The photomask inspection method according to supplementary note 1, wherein the reference image data is an image acquired by the image acquisition unit.

  (Supplementary note 3) The photomask inspection method according to supplementary note 1, wherein the reference image data is data obtained by developing the photomask design data.

  (Supplementary Note 4) In the fifth step, pattern matching processing is performed between the image data of the peripheral area of the defect acquired by the image acquisition unit and the reference image data, and then the image of the position of the defect The inspection method for a photomask according to appendix 1, wherein the presence / absence of a defect is determined by comparing the reference image data of a portion corresponding thereto.

(Additional remark 5) It is judged whether it is a defect which can be removed by the said defect removal process between the said 2nd process and the said 3rd process, and a specific flag is added to the said defect information about the defect which can be removed And having a process of
In the fifth step, only the image of the area corresponding to the defect information to which the specific flag is added is obtained from the photomask, and the presence or absence of a defect is determined by the defect inspection unit. The photomask inspection method according to attachment 1.

(Appendix 6) a stage on which a photomask is placed;
An image acquisition unit for acquiring an image of a photomask placed on the stage;
An image data storage unit for storing first image data serving as a reference for defect detection;
The image data acquired by the image acquisition unit is used as second image data, and the defect is detected by comparing the second image data with the first image data stored in the image data storage unit. Defect inspection department;
A defect information storage unit that stores, as defect information, the position of the defect detected by the defect inspection unit;
An inspection result recording unit for recording defect information of at least one photomask in association with an identification code unique to the photomask;
A control unit that controls the image acquisition unit, the image data storage unit, the defect inspection unit, and the inspection result recording unit;
The control unit controls the image acquisition unit based on the defect information recorded in the inspection result recording unit when re-inspecting a photomask in which defect information is recorded in the inspection result recording unit. The image of only the position of the defect detected in the previous inspection and the area around it is acquired and input to the defect inspection unit as the second image data, and the defect detection unit inputs the second image that has been input An inspection apparatus for a photomask, wherein the presence of a defect is determined by comparing data and first image data stored in the image data storage unit.

  (Supplementary Note 7) The photomask inspection apparatus according to Supplementary Note 6, wherein the image data storage unit stores an image acquired by the image acquisition unit as the first image data.

(Appendix 8) Furthermore, a design data storage unit for storing photomask design data;
An image data expansion unit that expands the design data stored in the design data storage unit to obtain image data;
7. The photomask inspection apparatus according to appendix 6, wherein the image data storage unit stores the image data expanded by the image data expansion unit as the first image data.

  (Additional remark 9) The image data development section performs a data correction process for correcting a difference between the design data and an actual pattern of the photomask formed thereby. Inspection device.

  (Additional remark 10) The said defect detection part performs a pattern matching process with the said 2nd image data using the image data of the area | region around a defect among said 1st image data, and the image in the position of the said defect after that 7. The photomask inspection apparatus according to appendix 6, wherein the presence of a defect is determined by comparing the data and the first image data corresponding to the data.

FIG. 1 is a block diagram showing a configuration of a conventional photomask inspection apparatus used for die comparison inspection. FIG. 2 is a schematic diagram showing a die comparison inspection method. FIG. 3 is a block diagram showing a configuration of a conventional photomask inspection apparatus used for data comparison inspection. FIG. 4A is a schematic diagram showing design data, and FIG. 4B is a schematic diagram showing a pattern actually formed on the photomask by the design data. FIG. 5 is a flowchart (part 1) showing a conventional photomask inspection / correction process. FIG. 6 is a flowchart (part 2) showing a conventional photomask inspection / correction process. FIG. 7 is a block diagram showing the configuration of the photomask inspection apparatus according to the first embodiment of the present invention. FIG. 8 is a flowchart showing a photomask inspection method (second inspection) according to the first embodiment. FIG. 9 is a schematic diagram showing a photomask inspection method according to the first embodiment. FIG. 10 is a flowchart showing a photomask inspection method according to a modification of the first embodiment of the present invention. FIG. 11 is a block diagram showing a configuration of a photomask inspection apparatus according to the second embodiment of the present invention. FIG. 12 is a flowchart showing a photomask inspection method (second inspection) according to the second embodiment. FIG. 13 is a flowchart (No. 1) showing a photomask inspection method according to the third embodiment of the present invention. FIG. 14 is a flowchart (No. 2) showing the photomask inspection method according to the third embodiment of the present invention. FIGS. 15A to 15E are schematic views showing a photomask inspection method according to the fourth embodiment of the present invention.

Explanation of symbols

10, 30, 110, 130 ... photomask,
11, 31, 111, 131 ... stages 12, 32, 112, 132 ... light sources,
13, 33, 113, 133 ... optical lenses,
14, 34, 114, 134... Light receiving element,
15, 35, 115, 135 ... image data storage unit,
16, 36, 116, 136 ... defect inspection section,
17, 37, 117, 137 ... defect information storage unit,
18, 38, 118, 138... Lens control unit,
19, 39, 119, 139 ... stage drive unit,
20, 40, 120, 140 ... control unit,
41, 141 ... design data,
42, 142 ... design data storage unit,
43, 143... Image data development unit,
44, 144 ... data correction unit,
121, 145... Inspection result recording unit.

Claims (4)

A first step of acquiring an image of a photomask by an image acquisition unit and detecting defects by comparing with image data serving as a reference by a defect inspection unit;
A second step of storing the position of the defect detected in the first step in the defect information storage unit as defect information;
A third step of recording the defect information stored in the second step in an inspection result recording unit in association with a unique identification code for each photomask;
A fourth step of performing defect removal processing;
The defect information recorded in the third step is read, and an image of only the position of the defect detected in the first step and its peripheral region is acquired from the photomask after the defect removal processing by the image acquisition unit. And a fifth step of determining the presence or absence of a defect by comparing with image data serving as a reference by the defect inspection unit.   In the fifth step, pattern matching processing is performed between the image data of the peripheral area of the defect acquired by the image acquisition unit and the reference image data, and then the image of the position of the defect and the corresponding portion 2. The photomask inspection method according to claim 1, wherein the presence or absence of a defect is determined by comparing the reference image data. There is a step of determining whether or not the defect can be removed by the defect removal process between the second step and the third step, and adding a specific flag to the defect information for the removable defect. And
In the fifth step, only the image of the area corresponding to the defect information to which the specific flag is added is obtained from the photomask, and the presence or absence of a defect is determined by the defect inspection unit. The photomask inspection method according to claim 1. A stage on which a photomask is placed;
An image acquisition unit for acquiring an image of a photomask placed on the stage;
An image data storage unit for storing first image data serving as a reference for defect detection;
The image data acquired by the image acquisition unit is used as second image data, and the defect is detected by comparing the second image data with the first image data stored in the image data storage unit. Defect inspection department;
A defect information storage unit that stores, as defect information, the position of the defect detected by the defect inspection unit;
An inspection result recording unit for recording defect information of at least one photomask in association with an identification code unique to the photomask;
A control unit that controls the image acquisition unit, the image data storage unit, the defect inspection unit, and the inspection result recording unit;
The control unit controls the image acquisition unit based on the defect information recorded in the inspection result recording unit when re-inspecting a photomask in which defect information is recorded in the inspection result recording unit. The image of only the position of the defect detected in the previous inspection and the area around it is acquired and input to the defect inspection unit as the second image data, and the defect detection unit inputs the second image that has been input An inspection apparatus for a photomask, wherein the presence of a defect is determined by comparing data and first image data stored in the image data storage unit.

Images