JP2017129385A - Mask inspection method and mask inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mask inspection method and a mask inspection device with which it is possible to appropriately inspect a defect in mask pattern.SOLUTION: The mask inspection method includes: dividing an inspection area out of a pattern area which is to be inspected for a defect into a plurality of stripes extending in a first direction and adjacent to each other in a second direction orthogonal to the first direction; comparing the focusing object position of a last stripe out of the plurality of stripes to be inspected last with the inspection area; when the object position is out of the inspection area, changing the position of the last stripe in the second direction so that the object position is within the inspection area; and scanning along each stripe with inspection light while adjusting focus to the object position of each stripe.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a mask inspection method and a mask inspection apparatus.

  An EUV (Extreme Ultraviolet) mask mainly has a light shielding band (that is, a black border region) between a pattern region having a pattern and a non-pattern region having no pattern arranged on the outer periphery of the pattern region. It has become. The light shielding band is provided for the purpose of preventing a shadowing phenomenon in which EUV light is blocked. The shading band is lower than the pattern area and the non-pattern area.

  When inspecting a pattern defect of an EUV mask, an inspection area set by a user in a pattern area is virtually divided into a plurality of stripes. After the inspection area is divided into a plurality of stripes, the inspection light is scanned along each stripe while focusing on the focus target position of each stripe (that is, the focus signal acquisition position). In the process of scanning the inspection light, a pattern defect on the stripe is inspected based on the reflected light of the inspection light from the stripe.

  The inspection area can be arbitrarily set in the pattern area, while the width of the stripe is determined to be a constant width such as 3584 pixels. For this reason, in the final stripe to be inspected last, a part of the area in the width direction often protrudes outside the inspection area. When the focus target position is set at the center position in the width direction of each stripe, the final stripe may protrude outside the inspection area, and the focus target position of the final stripe may be outside the inspection area.

  When the inspection area is set sufficiently inside the light-shielding band, the focus target position of the final stripe can be within the pattern area even when it is outside the inspection area. In this case, since the focus adjustment of the final stripe is performed so as to match the pattern region having almost the same height as the inspection region, defocusing, that is, focus blurring hardly occurs.

JP 2012-78164 A

  However, when the inspection area reaches the vicinity of the light shielding band, the final stripe protrudes outside the inspection area, so that the focus target position of the final stripe can be within the light shielding band. In this case, focus adjustment of the final stripe is performed so as to match the light shielding band whose height is lower than the inspection area. As a result, defocus increases, and a pseudo defect is detected even though no defect actually occurs.

  Therefore, conventionally, there has been a problem that it is difficult to properly inspect the mask pattern for defects.

  An object of the present invention is to provide a mask inspection method and a mask inspection apparatus that can appropriately inspect defects in a mask pattern.

  A mask inspection method according to one embodiment of the present invention is a mask inspection method for inspecting a defect in a pattern of a mask having a pattern region having a pattern and a peripheral region surrounding the pattern region and having a different height from the pattern region. The inspection area to be inspected for defects in the pattern area is divided into a plurality of stripes extending in the first direction and adjacent in the second direction orthogonal to the first direction, and inspected last among the plurality of stripes. Compare the target position of the final stripe to be in focus with the inspection area, and if the target position is outside the inspection area, change the position of the final stripe in the second direction so that the target position is within the inspection area. The inspection light is scanned along each stripe while focusing on the target position of each stripe.

  In the mask inspection method described above, the position of the final stripe may be changed so that the final stripe is entirely within the inspection area.

  A mask inspection method of the present invention is a mask inspection method for inspecting a defect of a pattern of a mask having a pattern region having a pattern and a peripheral region surrounding the pattern region and having a height different from the pattern region. The inspection area to be inspected for defects is divided into a plurality of stripes extending in the first direction and adjacent in the second direction orthogonal to the first direction, and the last stripe to be inspected last among the plurality of stripes. Compare the focus target position with the inspection area, and if the target position is outside the inspection area, change the position of the final stripe in the second direction so that the entire final stripe is outside the inspection area; and , Change the stripe immediately before the last stripe whose focus target position is in the inspection area to a new last stripe, and While focusing on the target position, it may be configured to scan the inspection light along each stripe.

  In the mask inspection method described above, the position of the final stripe may be changed in units of frames constituting the stripe.

  In the mask inspection method described above, the inspection area is divided into a plurality of stripes so that adjacent stripes overlap in the second direction, and the position of the final stripe is changed by the amount of overlap between adjacent stripes. It may be done by changing. Note that not only the position of the final stripe but also the positions of stripes other than the final stripe may be changed by changing the overlap amount between adjacent stripes.

  In the mask inspection method described above, the inspection region is divided into a plurality of stripes so that the frames constituting each stripe overlap in the second direction, and the position of the final stripe is changed between adjacent frames. It may be performed by changing the overlap amount. Note that not only the position of the final stripe but also the positions of stripes other than the final stripe may be changed by changing the overlap amount between adjacent frames.

  A mask inspection apparatus according to one embodiment of the present invention is a mask inspection apparatus that inspects a pattern defect of a mask having a pattern region having a pattern and a peripheral region that surrounds the pattern region and has a different height from the pattern region. The stripe management section that divides the inspection area to be inspected for defects in the pattern area into a plurality of stripes extending in the first direction and adjacent in the second direction orthogonal to the first direction, and focusing of each stripe A focus mechanism that performs focusing on the target position of the plurality of stripes, and the stripe management unit detects the target position of the final stripe to be inspected last out of the plurality of stripes when the target position is outside the inspection area. The position of the final stripe is changed in the second direction so as to be inside.

  A mask inspection apparatus of the present invention is a mask inspection apparatus for inspecting a pattern defect of a mask having a pattern region having a pattern and a peripheral region that surrounds the pattern region and has a different height from the pattern region. Among them, the inspection area to be inspected for defects extends in the first direction and is divided into a plurality of adjacent stripes in the second direction orthogonal to the first direction, and to the target position for focusing each stripe. A stripe mechanism, and the stripe management unit inspects the entire final stripe when the focus target position of the final stripe to be inspected last out of the plurality of stripes is outside the inspection area. Change the position of the final stripe in the second direction so that it is out of the area, and Position may be configured to change the stripe immediately preceding the last stripe in the examination region to the new final stripe.

  According to the present invention, it is possible to appropriately inspect a defect of a mask pattern.

It is a figure which shows the mask inspection apparatus of 1st Embodiment. 2A is a plan view showing an example of a mask to which the mask inspection apparatus of the first embodiment can be applied, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. 2A. It is a flowchart which shows the mask inspection method of 1st Embodiment. It is a perspective view which shows the mask inspection method of 1st Embodiment. FIG. 5A shows a focus target position before the final stripe position is changed in the mask inspection method of the first embodiment, and FIG. 5B shows a focus target position after the final stripe position is changed. It is a schematic diagram. It is a flowchart which shows the mask inspection method of 2nd Embodiment. It is a schematic diagram which shows the mask inspection method of 2nd Embodiment. It is a flowchart which shows the mask inspection method of 3rd Embodiment. FIG. 9 is a schematic diagram showing overlap between frames and overlap between stripes in the mask inspection method of the third embodiment. It is a flowchart which shows the mask inspection method of 4th Embodiment. FIG. 11A shows a focus target position before the final stripe position is changed in the mask inspection method according to the fourth embodiment, and FIG. 11B shows a focus target position after the final stripe position is changed. It is a schematic diagram.

  Embodiments according to the present invention will be described below with reference to the drawings. The embodiments do not limit the present invention.

(First embodiment)
FIG. 1 is a diagram illustrating a mask inspection apparatus 1 according to the first embodiment. FIG. 2A is a plan view showing an example of a mask 2 to which the mask inspection apparatus 1 of the first embodiment can be applied. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. 2A. The mask inspection apparatus 1 of FIG. 1 can be used, for example, to inspect defects in the pattern of the EUV mask (hereinafter also simply referred to as a mask) 2 shown in FIGS. 2A and 2B.

  Here, the configuration of the mask 2 will be described first. The mask 2 is used for photolithography in a semiconductor manufacturing process. As shown in FIGS. 2A and 2B, the mask 2 includes a pattern region 201, a non-pattern region 202, and a light shielding band 203 that is an example of a peripheral region. The pattern area 201 has a rectangular shape in plan view. In the pattern region 201, an absorber pattern 204 is formed by surface irregularities. The pattern 204 has a shape corresponding to the semiconductor pattern. The uppermost layer of the multilayer mirror 214 is exposed between the adjacent patterns 204. The multilayer mirror 214 can expose the resist on the wafer by reflecting the EUV light incident between the adjacent patterns 204. The non-pattern area 202 is provided around the pattern area 201. The non-pattern region 202 has a rectangular frame shape surrounding the pattern region 201 in plan view. No pattern is formed in the non-pattern region 202. The light shielding band 203 surrounds the pattern area 201 between the pattern area 201 and the non-pattern area 202. The light shielding band 203 has a rectangular frame shape surrounding the pattern region 201 in plan view. The height of the light shielding band 203 is lower than the heights of the pattern area 201 and the non-pattern area 202. The pattern area 201 and the non-pattern area 202 may have the same height.

  In order to inspect such a defect in the pattern 204 of the mask 2, as shown in FIG. 1, the mask inspection apparatus 1 includes a light source 3, a polarization beam splitter 4, an illumination optical system 5, An XYθ table 6, an enlargement optical system 7, and a photodiode array 8 are provided. A wavelength plate that changes the polarization direction of light may be provided between the polarizing beam splitter 4 and the XYθ table 6.

  The light source 3 emits laser light toward the polarization beam splitter 4. The light used for photolithography is EUV light, but the light used for defect inspection of the pattern 204, that is, inspection light may be laser light. The polarization beam splitter 4 reflects light from the light source 3 toward the illumination optical system 5. The illumination optical system 5 irradiates the light reflected by the polarization beam splitter 4 toward the XYθ table 6. The mask 2 placed on the XYθ table 6 reflects the light emitted from the illumination optical system 5. The mask 2 is illuminated by the reflected light of the mask 2. The reflected light of the mask 2 passes through the illumination optical system 5 and the deflecting beam splitter 4 and then enters the expansion optical system 7. The magnifying optical system 7 forms the incident reflected light of the mask 2 on the photodiode array 8 as an image of the mask 2 (hereinafter also referred to as an optical image). The photodiode array 8 photoelectrically converts the optical image of the mask 2. Based on the optical image of the mask 2 subjected to photoelectric conversion, the defect of the pattern 204 is inspected.

  As shown in FIG. 1, the mask inspection apparatus 1 includes an autoloader 9, an X-axis motor 10A, a Y-axis motor 10B and a θ-axis motor 10C, a Z sensor 13, a focus mechanism 11, and a laser length measurement system 12. With.

  The autoloader 9 automatically conveys the mask 2 on the XYθ table 6. The X-axis motor 10A, the Y-axis motor 10B, and the θ-axis motor 10C move the XYθ table 6 in the X direction, the Y direction, and the θ direction, respectively. Thereby, the light of the light source 3 is scanned with respect to the mask 2 on the XYθ table 6. The laser length measurement system 12 detects the positions of the XYθ table 6 in the X direction and the Y direction.

  The Z sensor 13 detects the height of the surface of the mask 2 on the pattern 204 side (hereinafter also referred to as a mask surface), that is, the position in the Z direction. The Z sensor 13 may include, for example, a projector that emits light to the mask surface and a light receiver that receives the emitted light. By providing the projector and the light receiver, the Z sensor 13 can optically detect the height of the mask surface.

  In order to suppress the defocusing of the optical image, the focus mechanism 11 performs focusing to adjust the focus of the illumination optical system 5 to the mask surface. Focusing is performed by moving the XYθ table 6 in the Z direction by a moving amount corresponding to the height of the mask surface detected by the Z sensor 13. The focusing is not necessarily limited to moving the XYθ table 6 in the Z direction, and may be performed by moving the illumination optical system 5 in the Z direction, for example.

  As shown in FIG. 1, the mask inspection apparatus 1 includes various circuits connected to a bus 14. Specifically, the mask inspection apparatus 1 includes an autoloader control circuit 15, a stripe management circuit 16, which is an example of a stripe management unit, a table control circuit 17, a Z sensor control circuit 21, and an autofocus control circuit 18. Prepare. In addition, the mask inspection apparatus 1 includes a position circuit 22, a development circuit 23, a reference circuit 24, and a comparison circuit 25. The mask inspection apparatus 1 includes a sensor circuit 19, and the sensor circuit 19 is connected between the photodiode array 8 and the comparison circuit 25.

  The autoloader control circuit 15 controls the autoloader 9.

  As shown in FIG. 4, the stripe management circuit 16 virtually divides the inspection area 205 to be inspected for defects in the pattern area 201 into a plurality of strip-shaped stripes 206. In FIG. 4, the stripes 206 extend in the X direction, which is an example of the first direction, and are adjacent to each other in the Y direction, which is an example of the second direction. The inspection area 205 can be set by the user by an input operation to the mask inspection apparatus 1. In the example of FIG. 4, the entire pattern area 201 is set as the inspection area 205, but the inspection area 205 may be a partial area of the pattern area 201.

  Also, the stripe management circuit 16 compares the final stripe 206A (see FIG. 4) to be inspected last among the stripes 206 with the focus target position of the final stripe 206A. The focus target position is uniform for all stripes 206. For example, the focus target position may be the center position of each stripe 206 in the Y direction.

  When the focus position of the final stripe 206A is outside the inspection area 205, the stripe management circuit 16 changes the position of the final stripe 206A in the Y direction so that the target position is within the inspection area 205. To do.

  The position of the final stripe 206 </ b> A may be changed so that the entire final stripe 206 </ b> A fits in the inspection area 205. In this case, the focus target position of the final stripe 206A can be controlled within the inspection region 205 simply and reliably.

  On the other hand, when the focus target position of the final stripe 206A is within the inspection area 205, the stripe management circuit 16 maintains the target position.

  The stripe management circuit 16 outputs management information of the stripe 206 including the focus adjustment target position to the table control circuit 17.

  If the focus target position of the final stripe 206A deviates from the inspection area 205, the target position may exist in the light shielding band 203. In this case, focusing at the final stripe 206A is performed so as to match the light shielding band 203. Since the height of the light-shielding band 203 is lower than the height of the inspection area 205, a large defocus is generated by focusing on the final stripe 206A.

  On the other hand, according to the first embodiment, by changing the position of the final stripe 206A, the target position for focusing of the final stripe 206A can be accommodated in the inspection region 205. Thereby, since the focus adjustment at the final stripe 206A can be performed so as to match the inspection region 205, defocusing can be suppressed.

  The table control circuit 17 drives and controls the motors 10A to 10C according to the management information of the stripe 206 input from the stripe management circuit 16. By driving control of the motors 10A to 10C, the XYθ table 6 moves so that the light of the light source 3 is scanned along the stripe 206. In addition, the XYθ table 6 moves so as to focus on the inspection area 205 in focusing on the final stripe 206A.

  The autofocus control circuit 18 controls the focus mechanism 11 so as to perform focusing. The autofocus control circuit 18 outputs a focus signal corresponding to the height of the sensor surface detected by the Z sensor 13 to the focus mechanism 11. Based on the focus signal, the focus mechanism 11 moves the XYθ table 6 in the Z direction by an amount corresponding to the height of the sensor surface.

  The sensor circuit 19 captures the optical image photoelectrically converted by the photodiode array 8 and A / D converts the captured optical image. Then, the sensor circuit 19 outputs the A / D converted optical image to the comparison circuit 25. The sensor circuit 19 may be, for example, a TDI (Time Delay Integration) sensor circuit. By using the TDI sensor, the pattern 204 can be imaged with high accuracy.

  The laser length measurement system 12 detects the movement position of the XYθ table 6 and outputs the detected movement position to the position circuit 22. The position circuit 22 detects the position of the mask 2 on the XYθ table 6 based on the movement position input from the laser length measurement system 12. Then, the position circuit 22 outputs the detected position of the mask 2 to the comparison circuit 25.

  The development circuit 23 reads the design data of the mask 2. The design data may be read from a magnetic disk device 31 described later. The design data may be information such as the coordinates of the graphic representing the mask, the length of the side, and the type. The development circuit 23 converts the read design data into binary or multivalued image data. Then, the expansion circuit 23 outputs the design data converted into image data to the reference circuit 24.

  The reference circuit 24 generates a reference image used for defect inspection of the pattern 204 by performing appropriate filter processing on the design data input from the development circuit 23. The reference circuit 24 outputs the generated reference image to the comparison circuit 25.

  The comparison circuit 25 measures the line width at each position of the pattern of the optical image while using the position information input from the position circuit 22. The comparison circuit 25 compares the line width and the gradation value (brightness) of both patterns of the measured optical image pattern and the reference image pattern input from the reference circuit 24. Then, the comparison circuit 25 detects, for example, an error between the line width of the pattern of the optical image and the line width of the pattern of the reference image as a defect of the pattern 204.

  As shown in FIG. 1, the mask inspection apparatus 1 includes a control computer 30, a magnetic disk device 31, a magnetic tape device 32, a floppy (registered trademark) disk 33, a CRT 34, a pattern monitor 35, and a printer. 36. These components 30 to 36 are all connected to the bus 14. The control computer 30 executes various types of control and processing related to the defect inspection of the pattern 204 for each component connected to the bus 14. The magnetic disk device 31, the magnetic tape device 32, and the floppy disk 33 store various types of information related to defect inspection. The CRT 34 and the pattern monitor 35 display various images related to defect inspection. The printer 36 prints various information related to defect inspection.

(Mask inspection method)
Next, a mask inspection method to which the mask inspection apparatus 1 is applied will be described. FIG. 3 is a flowchart illustrating the mask inspection method according to the first embodiment. FIG. 4 is a perspective view showing the mask inspection method of the first embodiment. In the mask inspection method according to the first embodiment, the XYθ table 6 is moved so that the stripe 206 in the inspection region 205 is continuously scanned in the direction indicated by the dashed arrow in FIG. In FIG. 4, the stripe 206A located in the most + Y direction is the final stripe 206A. Further, in the mask inspection method of the first embodiment, the defect of the pattern 204 (see FIG. 1) on the stripe 206 based on the optical image picked up by the photodiode array 8 while scanning light along the stripe 206. Inspect. The following description focuses on focusing in the process of defect inspection of the pattern 204.

  First, as shown in FIG. 3, an inspection setup is performed (step S1). In the inspection setup, in order, the loading of the mask 2 by the autoloader 9, the alignment of the mask 2 by the XYθ table 6, the calibration of the imaging conditions (for example, the light amount) according to the mask 2 by the calibration circuit (not shown), The inspection area 205 is set by the stripe management circuit 16. In the case of a D-DB (Die to Database) inspection in which a defect of the pattern 204 is inspected by comparing an optical image with a reference image, a learning process for correcting the reference image using a representative optical image is performed.

  After the inspection setup, the stripe management circuit 16 performs pre-inspection preparation (step S2). In the pre-inspection preparation, the stripe management circuit 16 performs an operation of virtually dividing the inspection area 205 into a plurality of stripes 206.

  After the pre-inspection preparation, the stripe management circuit 16 compares the focus target position of the final stripe 206 </ b> A among the plurality of divided stripes 206 with the inspection area 205. At this time, the stripe management circuit 16 may compare the focus target position of the final stripe 206 </ b> A with the position of the end of the inspection region 205. Then, the stripe management circuit 16 determines whether the focus target position of the final stripe 206A is outside the inspection area 205 (step S3).

  FIG. 5A is a schematic diagram illustrating a focus target position before changing the position of the final stripe 206A in the mask inspection method according to the first embodiment. FIG. 5B is a schematic diagram illustrating a focus target position after the position of the final stripe 206A is changed. 5A and 5B show a line L (hereinafter also referred to as a focus target line) L that passes through the center position in the Y direction of the stripe 206 as a focus target position of the stripe 206. Since the focus signal is acquired based on the reflected light from the focus target line L, the focus target line L can also be referred to as a focus signal acquisition line. The focus target line L of the final stripe 206A in FIG. 5A exists outside the inspection region 205, and the focus target line L of the final stripe 206A in FIG. 5B exists in the inspection region 205. In the example of FIG. 5B, the entire final stripe 206A is within the inspection area 205.

  When the focus position of the final stripe 206A is not outside the inspection area 205 (step S3: No in FIG. 3), the stripe management circuit 16 does not change the focus position of the final stripe 206A. In this case, the inspection along each stripe 206 is started while maintaining the original stripe 206 (step S4 in FIG. 3).

  On the other hand, as shown in FIG. 5A, when the focus target position (that is, the focus target line L) of the final stripe 206A is outside the inspection region 205 (step S3: Yes in FIG. 3), the stripe management circuit 16 The position of the final stripe 206A in the Y direction is changed so that the target position falls within the inspection area 205 (step S5 in FIG. 3). For example, as shown in FIG. 5B, the stripe management circuit 16 changes the position of the final stripe 206A in the Y direction so that the entire final stripe 206A is within the inspection region 205. After changing the position of the final stripe, the inspection along each stripe 206 is started (step S4 in FIG. 3).

  As described above, according to the first embodiment, when the focus target position of the final stripe 206A is outside the inspection area 205, the target position is changed by changing the position of the final stripe 206A in the Y direction. Can be stored in the inspection region 205. By keeping the target position within the inspection region 205, defocusing caused by focusing on the light shielding band 203 in focusing of the final stripe 206A can be avoided. Thereby, the detection of a pseudo defect can be prevented and the defect of the pattern 204 can be inspected appropriately.

(Second Embodiment)
Next, an embodiment in which the position of the final stripe 206A is changed in units of frames will be described as a second embodiment. In addition, in 2nd Embodiment, about the structure part corresponding to 1st Embodiment, the overlapping description is abbreviate | omitted using the same code | symbol. FIG. 6 is a flowchart illustrating a mask inspection method according to the second embodiment. FIG. 7 is a schematic diagram illustrating a mask inspection method according to the second embodiment.

  As shown in FIG. 7, the stripe 206 is composed of, for example, a frame 207 of 512 × 512 pixels. In the example of FIG. 7, the number of frames in the Y direction of the stripe 206 is seven frames. The comparison circuit 25 described above has a plurality of units divided for each frame 207. The comparison circuit 25 individually inspects the defect of the pattern 204 for each unit, that is, for each frame.

  In the second embodiment, when the focus target position of the final stripe 206A (see FIGS. 4, 5A, and 5B) is outside the inspection region 205, the stripe management circuit 16 in the Y direction of the final stripe 206A. Change the position in frames.

  Specifically, as shown in FIG. 6, the stripe management circuit 16 first changes the position of the final stripe 206 </ b> A (step S <b> 5 in FIG. 3) to first place the focus target position in the inspection area 205. The number of frames of the final stripe 206A to be moved (hereinafter also referred to as the number of moving frames) is calculated (step S51).

  After calculating the number of moving frames, the stripe management circuit 16 moves the final stripe 206A in the Y direction by a moving amount corresponding to the number of moving frames (step S52). For example, when the number of moving frames is 1, the stripe management circuit 16 moves the final stripe by one frame, that is, 512 pixels in the −Y direction.

  According to the second embodiment, by changing the position of the final stripe 206A in units of frames 207, the unit of the amount of change (that is, the amount of movement) of the position of the final stripe 206A is changed to the defect of the pattern 204 by the comparison circuit 25. It can be matched with the processing unit of inspection. As a result, the influence of the change in the position of the final stripe 206A on the defect inspection of the pattern 204 can be minimized. For example, the inspection according to the change in the position of the final stripe 206A can be easily performed by shifting the frame 207 in which each unit of the comparison circuit 42 is in charge of the inspection according to the change in the position of the final stripe 206A. .

(Third embodiment)
Next, as a third embodiment, an embodiment in which the position of the final stripe 206A is changed by adjusting the overlap amount will be described. In addition, in 3rd Embodiment, about the structure part corresponding to 1st Embodiment, the overlapping description is abbreviate | omitted using the same code | symbol. FIG. 8 is a flowchart showing a mask inspection method according to the third embodiment. FIG. 9 is a schematic diagram showing overlap between frames and overlap between stripes in the mask inspection method of the third embodiment.

  In order to inspect the inspection area 205 without omission, as shown in FIG. 9, the frames 207 in the stripe 206 overlap each other by a predetermined pixel in the overlap portion 207a in the Y direction. That is, the inspection area 205 is divided into a plurality of stripes 206 such that the frames 207 constituting each stripe 206 overlap in the Y direction. Further, as shown in FIG. 9, the stripes 206 also overlap each other by a predetermined pixel in the overlap portion 206a in the Y direction. That is, the inspection area 205 is divided into a plurality of stripes 206 such that adjacent stripes 206 overlap in the Y direction.

  Hereinafter, the number of pixels in the Y direction of the overlap portion 207a of the frame 207 is also referred to as an inter-frame overlap amount. The number of pixels in the Y direction of the overlap portion 206a of the stripe 206 is also referred to as an overlap amount between stripes.

  In the third embodiment, the stripe management circuit 16 overlaps the position of the final stripe 206A in the Y direction between frames when the focus target position of the final stripe 206A (see FIG. 4) is outside the inspection area 205. Change based on amount and overlap between stripes.

  Specifically, as shown in FIG. 8, the stripe management circuit 16 first increases the interframe overlap amount by a predetermined amount as a change in the position of the final stripe 206A in the Y direction (step S5 in FIG. 3) ( Step S501).

  After increasing the overlap amount between frames, the stripe management circuit 16 increases the overlap amount between stripes by a predetermined amount (step S502).

  For example, it is assumed that the final stripe 206A protrudes 750 pixels in the + Y direction (see FIG. 5A) with respect to the inspection region 205. Further, the number of stripes in the inspection area 205 is 100, the number of frames per stripe is 7, the number of pixels in the Y direction per stripe is 3584, the allowable variation amount of the overlap amount between frames is 1 pixel, and the overlap amount between stripes The permissible variation amount is 1 pixel.

  According to the flowchart of FIG. 8, the total width in the Y direction of the stripe 206 is increased to 700 pixels (that is, 1 pixel × 7 frames ×) by increasing the overlap amount between frames by 1 pixel which is an allowable variation amount (step S501). 100 stripes). At this time, the number of pixels of the final stripe 206A protruding in the + Y direction from the inspection area 205 is 50 pixels. Next, by increasing the overlap amount between stripes by 0.5 pixels (step S502), the total width in the Y direction of the stripes 206 can be further reduced by 50 pixels (that is, 0.5 pixels × 100 stripes). As a result, the number of pixels of the final stripe 206A that protrudes from the inspection area 205 in the + Y direction becomes 0, and the entire final stripe 206A fits in the inspection area 205.

  Note that the change in the position of the final stripe 206A in the Y direction based on the overlap amount between frames and the overlap amount between stripes is not limited to the above embodiment. For example, the overlap amount between frames may be changed after the overlap amount between stripes is changed. Further, the position of the final stripe 206A may be changed only by changing one of the interframe overlap amount and the stripe overlap amount. Further, the change in the Y-direction position of the final stripe 206A based on the interframe overlap amount and the inter-stripe overlap amount may be accompanied by a change in the Y-direction position of the stripes 206 other than the final stripe 206A. That is, the position of the final stripe 206A in the Y direction may be accommodated in the inspection region 205 by changing the position of each stripe 206 in the Y direction little by little.

  According to the third embodiment, the position of the final stripe in the Y direction can be easily changed based on the inter-frame overlap amount and the inter-stripe overlap amount. Thereby, defocus can be easily suppressed.

(Fourth embodiment)
Next, an embodiment in which the final stripe 206A itself is changed will be described as a fourth embodiment. Note that in the fourth embodiment, the description of the components corresponding to the first embodiment will be omitted by using the same reference numerals. FIG. 10 is a flowchart showing a mask inspection method according to the fourth embodiment. FIG. 11A is a schematic diagram illustrating a focus target position before changing the position of the final stripe 206A in the mask inspection method according to the fourth embodiment. FIG. 11B is a schematic diagram illustrating a focus target position after the position of the final stripe 206A is changed.

  In the first embodiment, when the focus position of the final stripe 206A is outside the inspection area 205 (step S3: Yes in FIG. 3), the final stripe 206A is set so that the target position is within the inspection area 205. The position in the Y direction has been changed (step S5 in FIG. 3).

  On the other hand, in the fourth embodiment, as shown in FIG. 11A, when the focus target position L of the final stripe 206A is outside the inspection region 205 (step S3: Yes in FIG. 10), FIG. As shown in FIG. 10, the position of the final stripe 206A in the Y direction is changed so that the entire final stripe 206A is outside the inspection region 205 (step S6 in FIG. 10). By changing the position of the final stripe 206A in this way, the final stripe 206A completely deviates outside the inspection area 205 and is excluded from the inspection target.

  In the fourth embodiment, after the position of the final stripe 206A in the Y direction is changed, the stripe 206B immediately before the final stripe 206A (see FIGS. 11A and 11B) is changed to a new final stripe (FIG. 10). Step S7). Note that the focus target position of the stripe 206B is in the inspection region 205. For this reason, focusing on the stripe 206B does not focus on the light shielding band 203.

  According to the fourth embodiment, when the focus target position of the final stripe 206A is outside the inspection area 205, the final stripe 206A is removed from the inspection area 205 by changing the position of the final stripe 206A in the Y direction. A complete departure can be made. Further, the stripe 206B immediately before the final stripe 206A whose focus target position is in the inspection area 205 can be changed to a new final stripe. Thereby, since defocusing caused by focusing on the light shielding band 203 in focusing on the final stripe can be avoided, detection of pseudo defects can be prevented.

  In addition, you may combine these suitably for several embodiment mentioned above. For example, the third embodiment may be combined with the second embodiment. In addition, the position of the final stripe 206A in the fourth embodiment is changed in units of frames as in the second embodiment, and the overlap amount between frames and the overlap amount between stripes as in the third embodiment. Or based on

  Further, in the fourth embodiment, the position of the stripe 206B may be changed in the + Y direction so that the final stripe 206B after the change can cover the end of the inspection region 205. In this case, the change of the position of the stripe 206B in the + Y direction may be performed by reducing at least one of the overlap amount between frames and the overlap amount between stripes.

  Further, the present embodiment is not limited to the D-DB inspection based on the difference from the reference image, and DD (Die) that detects a difference from the die image drawn from the same design data arranged on the mask as a defect. to Die). Further, the present embodiment can be applied to a mask other than the EUV mask as long as the mask has a peripheral region having a height different from that of the pattern region 201 around the pattern region 201.

  At least a part of the mask inspection apparatus 1 may be configured by hardware or software. When configured by software, a program for realizing at least a part of the functions of the mask inspection apparatus 1 may be stored in a recording medium such as a flexible disk or a CD-ROM, and read and executed by a computer. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory.

  The above-described embodiments are presented as examples, and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Mask inspection apparatus 2 Mask 201 Pattern area 203 Shading zone 11 Focus mechanism 16 Stripe management circuit

Claims (8)

A mask inspection method for inspecting a defect in a pattern of a mask having a pattern region having a pattern and a peripheral region surrounding the pattern region and having a different height from the pattern region,
An inspection region to be inspected for defects in the pattern region is divided into a plurality of stripes extending in a first direction and adjacent in a second direction orthogonal to the first direction,
Compare the target position of focus adjustment of the final stripe to be inspected last among the plurality of stripes, and the inspection area,
When the target position is outside the inspection area, the position of the final stripe is changed in the second direction so that the target position is within the inspection area.
A mask inspection method, wherein inspection light is scanned along each stripe while focusing on the target position of each stripe. A mask inspection method for inspecting a defect in a pattern of a mask having a pattern region having a pattern and a peripheral region surrounding the pattern region and having a different height from the pattern region,
An inspection region to be inspected for defects in the pattern region is divided into a plurality of stripes extending in a first direction and adjacent in a second direction orthogonal to the first direction,
Compare the target position of focus adjustment of the final stripe to be inspected last among the plurality of stripes, and the inspection area,
When the target position is outside the inspection area, the position of the final stripe is changed in the second direction so that the entire final stripe is outside the inspection area, and the focus target position is Change the stripe immediately before the final stripe in the inspection area to a new final stripe,
A mask inspection method, wherein inspection light is scanned along each stripe while focusing on the target position of each stripe.   2. The mask inspection method according to claim 1, wherein the position of the final stripe is changed so that the entire final stripe is within the inspection area.   4. The mask inspection method according to claim 1, wherein the position of the final stripe is changed in units of frames constituting the stripe. The division of the inspection region into the plurality of stripes is performed so that adjacent stripes overlap in the second direction,
The mask inspection method according to claim 1, wherein the position of the final stripe is changed by changing an overlap amount between adjacent stripes. The division of the inspection region into the plurality of stripes is performed so that frames constituting each stripe overlap in the second direction,
The mask inspection method according to claim 1, wherein the position of the final stripe is changed by changing an overlap amount between adjacent frames. A mask inspection apparatus for inspecting a defect of a pattern of a mask having a pattern region having a pattern and a peripheral region surrounding the pattern region and having a different height from the pattern region,
A stripe management unit that divides an inspection region to be inspected for defects in the pattern region into a plurality of stripes extending in a first direction and adjacent in a second direction orthogonal to the first direction;
A focusing mechanism that performs focusing on the target position of focusing of each stripe,
The stripe management unit is configured such that when the focus position of the final stripe to be inspected last out of the plurality of stripes is outside the inspection area, the target position is within the inspection area. A mask inspection apparatus that changes the position of the final stripe in a direction. A mask inspection apparatus for inspecting a defect of a pattern of a mask having a pattern region having a pattern and a peripheral region surrounding the pattern region and having a different height from the pattern region,
A stripe management unit that divides an inspection region to be inspected for defects in the pattern region into a plurality of stripes extending in a first direction and adjacent in a second direction orthogonal to the first direction;
A focusing mechanism that performs focusing on the target position of focusing of each stripe,
The stripe management unit is configured such that when the focus target position of the final stripe to be inspected last out of the plurality of stripes is outside the inspection area, the entire final stripe is outside the inspection area. A mask inspection characterized in that the position of the final stripe is changed in the second direction, and the stripe immediately before the final stripe whose focus target position is in the inspection area is changed to a new final stripe. apparatus.

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