JP2007206355A - Inspection method, and inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus for efficiently inspecting a photomask. <P>SOLUTION: The inspection apparatus 10 includes: an extension circuit 18 that incorporates inspection accuracy data 30 representing inspection accuracy of each area in a photomask 5 into second image data 25 as an image of the photomask 5 produced from CAD data 23 of the photomask 5 to thereby obtain reference data 31; a TDI sensor 17 that images laser beam 20 passing through the photomask 5; and a comparison circuit 19 that compares the first image data 22 and the second image data 25 in the reference data 31 along the inspection accuracy data 30 in the reference data 31 to detect a defect in the photomask 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention inspects defects in a photomask by, for example, comparing image data acquired by imaging light transmitted through a mask with image data that is an image of a photomask formed from photomask design data. It relates to an inspection device. Further, for example, inspection for inspecting a photomask defect by comparing image data obtained by imaging light transmitted through the mask with image data that is an image of a photomask formed from photomask design data. Regarding the method.

  Conventionally, image data obtained by imaging light transmitted through a photomask with a sensor is compared with drawing data (image actually drawn on a glass substrate) developed from CAD data as photomask pattern design data. Thus, a defect of the photomask is detected.

  At this time, the sensor has inspected the entire area of the photomask with the same inspection accuracy, for example, with a high inspection accuracy corresponding to a region where the photomask must be inspected with the highest accuracy. In such a case, even a region that does not need to be inspected as accurately as the inspection accuracy in the photomask is inspected with the above-described high inspection accuracy.

  As a result, even if it is a pseudo defect caused by a highly accurate inspection or a defect that does not actually cause trouble depending on the pattern, these are recognized as defects. The number recognized as defects increases.

  If the number recognized as a defect exceeds a predetermined number, the photomask is rejected. Therefore, the production efficiency of the photomask is reduced by recognizing a defect or a defect that does not actually cause a problem as a defect.

  Therefore, when inspecting the photomask, the inspection accuracy having the inspection accuracy necessary for each region of the photomask is determined, and each region of the photomask is inspected with the determined inspection accuracy. It will be necessary.

  In this way, areas that require high inspection accuracy in the photomask are inspected with high inspection accuracy, and areas that do not require high inspection accuracy in the photomask have corresponding accuracy. You must respond to the inspection accuracy you have.

In this type of inspection method, inspection accuracy data is formed based on the mask pattern when the mask pattern is designed. The inspection accuracy data is data indicating the accuracy of inspection accuracy of each region of the photomask. And each area | region of the formed photomask is test | inspected based on test | inspection precision data (for example, refer patent document 1).
JP 2004-191957 A

  On the other hand, improvement in photomask production efficiency is required, and therefore improvement in photomask inspection work efficiency is required.

  Accordingly, an object of the present invention is to provide an inspection apparatus capable of inspecting a photomask efficiently. Another object of the present invention is to provide an efficient photomask inspection method.

  The inspection apparatus of the present invention is an inspection apparatus that inspects the photomask by comparing first image data obtained by imaging light that has passed through the photomask and reference data for the photomask. . The inspection apparatus incorporates inspection accuracy data indicating inspection accuracy of each region of the photomask into second image data which is an image of the photomask formed from design data of the photomask, and the reference data And the second image in the first image data and the reference data in accordance with the inspection accuracy data in the reference data, a sensor for imaging the light that has passed through the photomask, and the second image data in the reference data. A comparator for comparing image data and detecting defects of the photomask.

  The inspection method of the present invention is an inspection method for inspecting the photomask by comparing first image data obtained by imaging light passing through the photomask and reference data for the photomask. . The inspection method includes a step of forming second image data that is an image of the photomask from the design data of the photomask, a step of determining inspection accuracy data indicating an inspection accuracy of each region of the photomask, Incorporating the inspection accuracy data into the second image data as the reference data, irradiating the photomask with the light to acquire the first image data, and the reference data A step of comparing the first image data with the second image data in the reference data according to the inspection accuracy, and a step of determining a defect of the photomask based on the comparison result. Prepare.

  According to the present invention, the inspection efficiency of a photomask is improved.

  An inspection apparatus 10 according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of an inspection apparatus 10. The inspection apparatus 10 is an apparatus that inspects the photomask 5. As shown in FIG. 1, the inspection apparatus 10 includes a laser output unit 11, a mirror 12, a condenser lens 13, an XY stage 14, a stage driving unit 15, an imaging lens 16, a TDI sensor 17, A development circuit 18, a comparison circuit 19, and an image readout correction unit 32 are provided.

  The laser output unit 11 outputs laser light 20 having a predetermined wavelength. The mirror 12 changes the traveling direction of the laser light 20 output from the laser output unit 11. The condensing lens 13 condenses the laser beam 20 reflected by the mirror 12 and irradiates the photomask 5 described later.

  A photomask 5 is placed and fixed on the XY stage 14. The stage drive unit 15 is connected to the XY stage 14 and moves the XY stage 14 in the X and Y directions shown in the drawing so that the entire photomask 5 is scanned by a TDI sensor 17 described later. Moving. The XY stage 14 has transparency, and therefore the laser light 20 irradiated on the photomask 5 passes through the XY stage 14. The imaging lens 16 forms an image of the laser light 20 that has passed through the photomask 5 and the XY stage 14.

  The TDI sensor 17 is an example of a sensor that captures an image of the photomask 5 formed by the imaging lens 16. FIG. 2 is a plan view of the photomask 5 fixed on the XY stage 14 as viewed from above. In FIG. 2, the scanning path 21 of the TDI sensor 17 is indicated by a one-dot chain line. As the XY stage 14 moves in the X direction and the Y direction, the TDI sensor 17 moves relative to the photomask 5.

  The TDI sensor 17 first scans along the + Y direction relative to the photomask 5. Next, the TDI sensor 17 moves along the X direction relative to the photomask 5 by the length along the X direction of the TDI sensor 17. Next, the TDI sensor 17 scans along the −Y direction relative to the photomask 5. In this way, the entire first image data 22 of the photomask 5 is acquired.

  The sensor that captures the image of the photomask 5 imaged by the imaging lens 16 is not limited to the TDI sensor 17, and another sensor may be used.

  As shown in FIG. 1, the development circuit 18 receives the CAD data 23 of the photomask 5, and develops the drawing data 24 of the photomask 5 that matches the scanning position on the photomask 5 in the TDI sensor 17 from the CAD data 23. To do. The drawing data 24 is an image of the photomask 5. In this embodiment, the alphabet “A” is used as an example of the pattern 7 of the photomask 5. Then, second image data 25 in which the drawing data 24 is subjected to distortion correction is formed.

  The photomask 5 is designed using, for example, a CAD apparatus. Therefore, the CAD data 23 is an example of photomask design data referred to in the present invention. The second image data 25 is data in which the edge of the pattern 7 is distorted so as to match the pattern 7 that will be actually formed on the glass substrate 6 of the photomask 5.

  The operation of the expansion circuit 18 until the second image data 25 is formed will be specifically described. FIG. 3 is an overall view of the drawing data 24 of the photomask 5 developed from the CAD data 23. A part designed to be formed as a straight line on the CAD data 23 is indicated as a straight line on the drawing data 24. In the present embodiment, the outer edge 7 a of the pattern 7 is designed to be a straight line on the CAD data 23. Therefore, the outer edge of the pattern on the drawing data 24 is a straight line without distortion.

  FIG. 4 is an overall view of the second image data 25 of the photomask 5. When the pattern 7 is formed on the glass substrate 6 when the photomask 5 is actually formed, the outer edge 7a of the pattern 7 tends to be slightly distorted. Therefore, as shown in FIG. 4, the expansion circuit 18 forms second image data 25 by performing predetermined processing on the drawing data 24. In FIG. 4, for the sake of explanation, the “A” shape is exaggerated and greatly distorted, but the distortion is actually small.

  The development circuit 18 has a function of automatically incorporating the inspection accuracy data 30 into the second image data 25. The inspection accuracy data 30 will be specifically described. The inspection accuracy data 30 is data indicating the inspection accuracy in each region of the photomask 5. The area is indicated by XY coordinates. For example, if there is a defect on the photomask 5, the inspection accuracy corresponds to a threshold value with which the defect actually causes trouble. For example, when there is a defect in a certain area on the photomask 5 and the defect size is larger than a predetermined size, the inspection accuracy of the certain area is determined by using the predetermined size as a threshold value. It is set so that a defect larger than the size of is recognized as a defect.

  In addition, when the designer of the photomask 5 examines the inspection accuracy of the photomask 5 using the second image data 25 formed at the design stage of the photomask 5, This is reflected in the inspection accuracy data 30.

  The intention of the designer will be specifically described. Generally, when a pattern is formed on a glass substrate when forming a photomask, the corners of the pattern formed on the glass substrate tend to be slightly rounded. Therefore, in order to prevent the corners of the pattern from being rounded, a protrusion protruding outside the corner is formed in the CAD data of the pattern.

  In the present embodiment, in order to clearly form the corners of the four corners of the pattern 7, the CAD data 23 is formed with protrusions 7 b that protrude outside the four corners. Therefore, as shown in FIGS. 3 to 5, the protrusion 7 b exists in the drawing data 24 and the second image data 25, but as shown in FIG. 1, in the actual pattern 7 of the photomask 5. And it does not exist in the first image data 22.

  However, since the projection 7 b does not exist in the pattern 7 in the photomask 5, when the first image data 22 and the second image data 25 are compared, it is recognized that the photomask 5 is defective. It becomes like In such a case, the inspection accuracy of the region where the protrusion 7b is present needs to be set so that the protrusion 7b is not recognized as a defect. Specifically, in the inspection accuracy of the region where the protrusion 7b exists in the second image data 25, the size of the protrusion 7b is set as a threshold, and a defect having a size smaller than the protrusion 7b is not recognized as a defect. Set to

  As described above, the inspection accuracy determined from the second image data 25 and the intention of the designer are incorporated in the inspection accuracy data 30.

  The inspection accuracy data 30 is automatically incorporated into the second image data 25 in the development circuit 18. Specifically, the inspection accuracy of the region is integrally incorporated in the region on the second image data 25 corresponding to the region sensed by the TDI sensor 17 in the photomask 5. In this way, the data in which the second image data 25 and the inspection accuracy data 30 are integrated becomes reference data 31. FIG. 5 shows the reference data 31. The unfolding circuit 18 is an example of the unfolding unit referred to in the present invention.

  The image readout correction unit 32 sends a correction command for correcting the coordinate position of the reference data 31 formed by the expansion circuit 18 by adding or subtracting the coordinate position by the width of the TDI sensor 17 in the charge accumulation direction.

  The comparison circuit 19 compares the first image data 22 detected by the TDI sensor 17 with the reference data 31 and detects the presence or absence of a defect. The inspection accuracy data 30 in the reference data 31 is used as the inspection accuracy when comparing the first image data 22 and the reference data 31.

  Next, an example of a defect inspection method by the inspection apparatus 10 will be described. In the present embodiment, as shown by the second image data 25 in FIG. 5 surrounded by a two-dot chain line, the second image data 25 is stored in the first to seventh and ninth regions 41 in the development circuit 18. ˜47,49.

  The first to sixth regions 41 to 46 indicate the four corner regions of “A” of the pattern 7. The seventh area 47 is an area excluding the first to sixth areas 41 to 46 among the areas where the pattern 7 is formed in the second image data 25. The ninth area 49 is an area excluding the first to seventh areas 41 to 47 in the second image data 25. That is, the pattern 7 is not formed in the ninth region 49. In the present embodiment, protrusions 7 b are formed at the four corners (included in the first to sixth areas) of “A” of the second image data 25 for the above reasons.

  First, the designer creates inspection accuracy data 30. As an example of the procedure for creating the inspection accuracy data 30, the second image is created based on the CAD data 23 at the stage when the pattern 7 of the photomask 5 is designed using the CAD apparatus or when the design is completed. Data 25 is created. Then, the designer uses the second image data 25 to verify a place in the photomask 5 that requires particularly high inspection accuracy. Similarly, the second image data 25 is used to verify a place that does not require so much accuracy in the photomask 5. These verification results are reflected in the inspection accuracy data 30. Specifically, the pattern 7 is not formed in the ninth region 49 of the second image data 25. Therefore, even if the ninth region 49 is defective, the defect does not cause much trouble in practice. Therefore, the inspection accuracy of the ninth region 49 is set to be lower than the inspection accuracy of the first to sixth regions 41 to 46.

  Furthermore, the designer also reflects the protrusion 7 b, which is the designer's intention, in the inspection accuracy data 30. Specifically, the inspection accuracy of the first to sixth regions 41 to 46 is set so that only a defect larger than the size of the protrusion 7b is recognized as a defect so that the protrusion 7b is not recognized as a defect. .

  The seventh region 47 is a region excluding the first to sixth regions 41 to 46 among the regions where the pattern 7 is formed. In the seventh area 47, for example, a substantially intermediate inspection accuracy between the inspection accuracy of the first to sixth regions 41 to 46 and the inspection accuracy of the ninth region 49 is set.

  A series of creation of the inspection accuracy data 30 is a step of determining inspection accuracy data referred to in the present invention.

  Next, the designer inputs CAD data 23 and inspection accuracy data 30 to the expansion circuit 18. Next, the photomask 5 is placed and fixed on the XY stage 14.

  Next, the laser beam 20 is output from the laser output unit 11. The stage drive unit 15 drives the XY stage 14 so that the TDI sensor 17 images the photomask 5 along the scanning path 21. The first image data 22 captured by the TDI sensor 17 is transmitted to the comparison circuit 19. Thus, the process imaged by the TDI sensor 17 is a process of acquiring the first image data referred to in the present invention.

  The image readout correction unit 32 transmits a signal for expanding the reference data 31 of the part sensed by the TDI sensor 17 in the photomask 5 to the expansion circuit 18.

  The development circuit 18 receives a signal from the image readout correction unit 32 and forms reference data 31 corresponding to the first image data 22 (part of the photomask 5) captured by the TDI sensor 17.

  FIG. 6 is a flowchart showing an example of the operation of the expansion circuit 18. As shown in FIG. 6, in the expansion circuit 18, the drawing data 24 is first expanded from the CAD data 23 in step ST1. Next, in step ST2, the drawing data 24 is processed to form second image data 25. Steps ST1 and ST2 are steps for forming the second image data referred to in the present invention. Next, inspection accuracy data 30 is incorporated into the second image data 25 in step ST3. Step ST3 is a step of automatically incorporating the inspection accuracy data referred to in the present invention into the second image data to obtain reference data.

  As described above, the inspection accuracy data 30 input to the development circuit 18 is automatically incorporated into the second image data 25, whereby the reference data 31 is automatically formed. For example, when the TDI sensor 17 images the first area 41, the development circuit 18 forms reference data 31 corresponding to the first area 41. The reference data 31 is transmitted to the comparison circuit 19.

  In the comparison circuit 19, the first image data 22 and the reference data 31 are compared. In the comparison circuit 19, for example, when the first image data 22 corresponding to the first area 41 and the reference data 31 corresponding to the first area 41 are compared, the first image data 22 included in the reference data 31 is compared. Using the inspection accuracy data 30 indicating the inspection accuracy of the area 41, the first image data 22 corresponding to the first area 41 and the second image data 25 corresponding to the first area 41 are compared.

  The first image data 22 corresponding to the first area 41 does not have the protrusion 7b, but the second image data 25 corresponding to the first area 41 has the protrusion 7b. However, since the first region 41 is inspected with inspection accuracy that does not recognize the protrusion 7b as a defect, the protrusion 7b is not recognized as a defect. The same applies to the second to fourth regions 42 to 44.

  As shown in FIG. 1, the defect 100 exists in the photomask 5 corresponding to the ninth region 49. The defect 100 has a size that can be recognized as a defect with the inspection accuracy set in the ninth region 49. Therefore, the comparison circuit 19 determines that the ninth region 49 is defective. The series in the comparison circuit 19 is a step of comparing the reference data referred to in the present invention with the second image data, and a step of determining a defect.

  In the figure, reference numeral 110 denotes a comparison result by the comparison circuit 19. The comparison result 110 indicates that the defect 100 has been detected.

  In the inspection apparatus 10 configured as described above, the inspection accuracy data 30 is automatically incorporated into the second image data 25 in the expansion circuit 18 and becomes reference data 31. Then, the inspection apparatus 10 automatically inspects the photomask 5 using the reference data 31. Therefore, the inspection efficiency of the photomask 5 is improved.

  Next, an inspection apparatus 10 according to a second embodiment of the present invention will be described with reference to FIG. In addition, the structure which has a function similar to 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description. In the present embodiment, reference data 31 when a plurality of areas having different inspection accuracy overlap each other will be described.

  FIG. 7 shows the reference data 31 of the present embodiment. In FIG. 7, the first region 41 and the eighth region 48 having different inspection accuracy are indicated by a two-dot chain line. The inspection accuracy of the first region 41 is relatively moderate so as not to recognize the protrusion 7b as a defect. The inspection accuracy in the eighth region 48 is set to be stricter than the inspection accuracy in the first region 41. That is, the inspection accuracy of the eighth region 48 is higher than the inspection accuracy of the first region 41.

  As shown in the drawing, a part of the first area 41 and a part of the eighth area 48 overlap each other. Therefore, the overlapping portion 101 where a part of the first area 41 and a part of the eighth area 48 overlap is the inspection accuracy set in the first area 41 and the inspection set in the eighth area 48. It is examined with two inspection accuracy. In such a case, in this embodiment, the inspection result inspected with the inspection accuracy set in the eighth region 48 having high inspection accuracy is adopted as the inspection result of the overlapping portion 101.

  As described above, the reference data 31 includes a priority indicating which inspection accuracy is used in the overlapping portion 101 when each region overlaps each other.

  In the present embodiment, the inspection result with high inspection accuracy is set to be adopted. However, for example, the inspection result with low inspection accuracy may be adopted.

1 is a schematic configuration diagram of an inspection apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of a photomask fixed on the XY stage shown in FIG. 1. The whole figure of drawing data. The whole figure of the 2nd image data. Overall view of reference data. 3 is a flowchart showing an example of the operation of the expansion circuit shown in FIG. The whole figure of the data for reference of the inspection device concerning a 2nd embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 5 ... Photomask, 10 ... Inspection apparatus, 17 ... TDI sensor (sensor), 18 ... Development | deployment circuit (expansion part), 19 ... Comparison circuit (comparison part), 20 ... Laser beam, 22 ... 1st image data, 23 ... CAD data (design data), 25 ... second image data, 30 ... inspection accuracy data, 31 ... reference data.

Claims (3)

An inspection apparatus for inspecting the photomask by comparing first image data obtained by imaging light passing through the photomask and reference data for the photomask,
A developing unit that incorporates inspection accuracy data indicating inspection accuracy of each region of the photomask into the second image data that is an image of the photomask formed from the design data of the photomask, and serves as the reference data; ,
A sensor for imaging light that has passed through the photomask;
A comparison unit that compares the first image data with the second image data in the reference data along the inspection accuracy data in the reference data, and detects a defect of the photomask;
An inspection apparatus comprising: An inspection method for inspecting the photomask by comparing first image data obtained by imaging light that has passed through the photomask and reference data for the photomask,
Forming second image data which is an image of the photomask from the design data of the photomask;
Determining inspection accuracy data indicating inspection accuracy of each region of the photomask;
Incorporating the inspection accuracy data into the second image data to provide the reference data;
Irradiating the photomask with the light to obtain the first image data;
Comparing the first image data and the second image data in the reference data in accordance with the inspection accuracy in the reference data;
Determining a defect of the photomask based on the comparison result;
An inspection method comprising:   The inspection accuracy of the overlapping portions of the plurality of regions at least partially overlapping each other among the regions is determined in advance so that any one of the plurality of regions is employed. The inspection method according to claim 2.

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