JP6146717B2 - Inspection apparatus and inspection method - Google Patents

Description

  The present invention relates to an inspection apparatus and an inspection method.

  An inspection apparatus using a dark field illumination optical system is used for defect inspection. In the inspection apparatus using the dark field optical system, the defect is detected by detecting the scattered light scattered by the defect of the sample. For example, when illumination light enters a defect, the light is scattered. A detector can detect a defect by detecting scattered light. When a dark field illumination optical system is used, the intensity of scattered light increases when a defective part is illuminated. Therefore, the defect can be detected by comparing the scattered light intensity with the threshold value.

  In such an inspection apparatus, when illumination light enters a sample with a small NA, the depth of focus becomes deep. When the sample is transparent, if the NA is small, scattered light from other than the inspection target surface may be detected. For example, when the depth of the inspection target surface is shallow, the detector 18 also detects scattered light scattered on a surface other than the inspection target surface as shown in FIG. Specifically, even when an inspection for detecting a defect on the front surface of the sample is performed, a defect on the back surface is detected. Thus, when illuminating with a small NA, the detector 18 receives scattered light from the outside of the inspection target, so that there may be a case where a defect on the inspection target surface cannot be accurately detected.

JP 2014-62771 A Japanese Patent Laid-Open No. 9-269295 JP 62-188949 A

  Patent Document 1 discloses an inspection apparatus that inspects a transparent substrate such as a glass substrate. In the inspection apparatus of Patent Document 1, a transparent substrate is illuminated from an oblique direction, and scattered light scattered by the transparent substrate is detected. In Patent Document 1, linear illumination light illuminates a transparent substrate, and a one-dimensional or two-dimensional array sensor (detector) detects scattered light.

  Furthermore, in the modification 4 of patent document 1, the lens forms the surface foreign material image in the opening part of a slit (FIG. 13). The slit allows the scattered light from the front surface foreign material to pass through and blocks the scattered light from the back surface foreign material. In addition, the moving mechanism shifts the slit, so that the scattered light on the surface of the transparent substrate can be taken into the detector (paragraph 0058). By doing in this way, even when a board | substrate moves up and down, the influence of a back surface foreign material can be reduced. In Modification 5, the detector is moved instead of the slit.

  Patent Documents 2 and 3 disclose an apparatus that detects scattered light via a (light guide). In the apparatus of Patent Document 2, a plurality of optical fibers are arranged along the longitudinal direction of the illumination area. The light that has passed through the optical fiber is received by a photomultiplier tube. Thereby, the foreign material on the surface to be inspected can be detected.

  In Patent Document 3, scattered light scattered by a sample is collected on a field stop by a SELFOC (registered trademark) lens. Scattered light that has passed through the field stop enters the light guide. The light guide guides the scattered light to the light receiver. In Patent Document 1, four light guides and four light receivers are provided. Therefore, it is possible to determine on which surface of the mask the foreign matter exists. Specifically, it is possible to detect whether there is a foreign substance on the front surface of the mask, the back surface of the mask, or the pellicle protective film.

  In the configuration of Patent Document 1, it is necessary to align slits, lenses, detectors, and the like, and there is a problem that the device configuration becomes complicated. In Patent Document 2, since scattered light from different heights is received by the photomultiplier tube, it is difficult to separate and detect defects other than the inspection target surface. In Patent Document 3, since it is necessary to align a lens, a field stop, and a light guide, the apparatus configuration becomes complicated.

  The present invention has been made in the background of such circumstances, and an object thereof is to provide an inspection apparatus and an inspection method capable of accurately detecting defects on an inspection target surface in a sample with a simple configuration. It is what.

  The inspection apparatus according to the first aspect of the present embodiment includes an illumination optical system that illuminates a transparent sample with dark field, a detector that detects scattered light scattered by the sample, and the scattered light scattered by the sample. A plurality of optical fibers guided to a detector, and a holder for holding the plurality of optical fibers, the holder projecting closer to the illumination position of the sample than the incident end face of the plurality of optical fibers. is there. Thereby, it is possible to accurately detect defects on the inspection target surface in the sample with a simple configuration.

  In the inspection apparatus, the holder may be provided so as to be movable in a direction perpendicular to the surface of the sample. Thereby, the height of the surface to be inspected can be easily adjusted.

  In the above inspection apparatus, the distance between the end of the holder on the illumination position side and the incident end faces of the plurality of optical fibers may be variable. Thereby, the depth of the surface to be inspected can be easily adjusted.

  In the inspection apparatus, the detector may collectively detect the scattered light emitted from the emission ends of the plurality of optical fibers with one pixel. Thereby, a defect can be detected with high sensitivity.

  In the inspection apparatus, the illumination optical system may be provided with a scanner that scans illumination light in a first direction, and the plurality of optical fibers may be arranged along the first direction. Thereby, a defect can be detected with high sensitivity.

  The inspection apparatus according to the second aspect of the present embodiment includes an illumination optical system that illuminates a transparent sample with dark field, a detector that detects scattered light scattered by the sample, and a depth in the sample. And a lens for condensing the scattered light on different pixels of the detector. With this configuration, inspections at different depths can be performed simultaneously.

  The inspection method according to the third aspect of the present embodiment includes a step of illuminating a transparent sample with dark field, a step of causing scattered light from an illumination position of the sample illuminated with dark field to enter an optical fiber, and the light Detecting a scattered light propagating in the fiber with a detector, wherein a plurality of the optical fibers are provided, and a plurality of the optical fibers protrude from the incident end face of the optical fiber to the illumination position side. It is what is being held. Thereby, it is possible to accurately detect defects on the inspection target surface in the sample with a simple configuration.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection apparatus and inspection method which can detect the defect in the test object surface in a sample correctly with a simple structure with a simple structure can be provided.

It is a figure which shows the structure of the test | inspection apparatus concerning this Embodiment 1. FIG. In the inspection apparatus which concerns on Embodiment 1, it is a figure for demonstrating the optical path from a sample to a detector. It is a figure which shows the structure of the test | inspection apparatus concerning the modification of this Embodiment 1. FIG. It is a figure which shows the structure of the test | inspection apparatus concerning this Embodiment 2. FIG. It is a top view which shows the structure by the side of the incident surface of an optical fiber unit. In the inspection apparatus which concerns on Embodiment 2, it is a figure for demonstrating the optical path from a sample to a detector. It is a figure which shows the structure at the time of moving an optical fiber unit. It is a figure which shows the structure at the time of moving the optical fiber of an optical fiber unit. It is a figure which shows typically a mode that the scattered light from other than a test object surface injects into a detector.

  Hereinafter, a specific configuration of the present embodiment will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same contents.

Embodiment 1 FIG.
The inspection apparatus according to the present embodiment is an inspection apparatus that detects a defect in a transparent sample. Specifically, the inspection apparatus detects a defect by illuminating a sample using a dark field illumination optical system and detecting light scattered by the defect. The transparent sample is, for example, a transparent substrate such as a glass wafer, a photomask, or a mask blank used for manufacturing a semiconductor or a display. Here, a glass wafer having a thickness of 1 mm is used as a sample.

  The configuration of the inspection apparatus will be described with reference to FIG. FIG. 1 is a diagram schematically showing the configuration of the inspection apparatus 100. The inspection apparatus 100 is a dark field inspection machine that performs inspection using the illumination optical system 10. The inspection apparatus 100 includes a light source 11, a scanner 13, a lens 14, an XY stage 15, a lens 16, a slit 17, a detector 18, and a processing device 19. In the following description, an XYZ three-dimensional orthogonal coordinate system is used for clarity of explanation. The Z direction is a direction perpendicular to the surface of the sample 20, and the X direction and the Y direction are directions within the surface of the sample 20. In FIG. 1, the X direction is a direction parallel to the paper surface, and the Y direction is a direction perpendicular to the paper surface. The Z direction is a direction parallel to the optical axis of the illumination optical system 10 and is the height (depth) direction of the sample 20.

  The illumination optical system 10 illuminates the sample 20 with dark field. Therefore, the light source 11 generates illumination light L1 that illuminates the sample 20. For example, a laser light source having a wavelength of 532 nm or 405 nm can be used as the light source 11. The light source 11 may be a light source other than a laser light source such as a lamp light source. Furthermore, the wavelength of the illumination light L1 is not limited to the above value. The illumination light L1 from the light source 11 is a parallel light beam.

  The illumination light L1 emitted from the light source 11 enters the scanner 13. The scanner 13 is, for example, a galvanometer mirror or a polygon mirror, and deflects the illumination light L1 in the Y direction. Thereby, the illumination position on the surface of the sample 20 can be changed. In the configuration shown in FIG. 1, the illumination light L1 is deflected in a direction perpendicular to the paper surface. That is, the scanner 13 scans the illumination light L1 in the Y direction.

  The illumination light L 1 reflected by the scanner 13 enters the lens 14. The lens 14 collects the illumination light L1 and irradiates the sample 20. The lens 14 condenses the illumination light L1 on the inspection target surface of the sample 20. Here, the lens 14 condenses the illumination light L1 on the surface of the sample 20. In FIG. 1, the illumination light L1 illuminates the sample 20 from a direction perpendicular to the surface of the sample 20, but the illumination light L1 may be illuminated from an oblique direction. That is, the optical axis of the illumination light L1 may be parallel to the Z direction or may be inclined from the Z direction.

  The illumination light L1 collected by the lens 14 enters the sample 20. Thereby, the sample 20 is illuminated with the illumination light L1. For example, the illumination light L <b> 1 forms a circular spot at the illumination position of the sample 20. The sample 20 is placed on the stage 15. The stage 15 supports the end of the sample 20. The stage 15 is a driving stage such as an XYZ stage, and moves the sample 20. By driving the stage 15, the illumination position by the illumination light L <b> 1 can be moved to an arbitrary position of the sample 20. When the stage 15 moves in the X direction, the illumination position on the sample 20 is scanned. For example, while the scanner 13 scans the illumination light L1 in the Y direction, the stage 15 moves the sample 20 in the X direction. By doing in this way, the whole sample 20 or a desired area can be scanned with the illumination light L1.

  When the illumination light L1 enters the sample 20, scattered light L2 is generated from the sample 20. Scattered light L2 from the sample 20 enters the lens 16. The lens 16 is disposed above the surface of the sample 20. Here, in order to perform a dark field inspection, the optical axis of the lens 16 is inclined from the Z direction. That is, only the scattered light L <b> 2 that is scattered in a specific oblique direction, which is the sample 20, enters the lens 16.

  The lens 16 collects the scattered light L2 on the slit 17. The slit 17 has an opening 17 a on the optical axis of the lens 16. A detector 18 is arranged immediately after the slit 17. The detector 18 receives the scattered light L2 that has passed through the slit 17. That is, only the scattered light L2 incident on the opening 17a of the slit 17 is detected by the detector 18, and the scattered light L2 incident on a position shifted from the opening 17a of the slit 17 is shielded.

  The detector 18 is a point sensor such as a PMT (photomultiplier tube) and has only one pixel. The detector 18 outputs a detection signal corresponding to the amount of scattered light L2 received to the processing device 19. Note that a line sensor having a plurality of pixels arranged along the slit 17 or a two-dimensional array sensor may be used as the detector 18.

  The slit 17 is provided with an opening 17a along a direction perpendicular to the paper surface. That is, the longitudinal direction of the opening 17 a of the slit 17 corresponds to the scanning direction of the scanner 13. The detector 18 has a detection area corresponding to the scanning area in the Y direction. For example, the detector 18 has a detection region extending in a direction corresponding to the Y direction. Therefore, most of the scattered light L2 that has passed through the slit 17 is detected by the detector 18. Therefore, even if the scanner 13 scans the illumination light in the Y direction, the detector 18 can receive the scattered light L2.

  The processing device 19 includes an information processing device such as a personal computer and an electronic circuit such as an A / D converter. The processing device 19 detects a defect according to the comparison result between the detection signal and the threshold value. Since the dark field inspection is performed, the detection signal increases at the timing when the illumination light enters the defect. When the detection signal exceeds a preset threshold value, the processing device 19 determines that a defect exists. On the other hand, if the detection signal does not exceed the threshold value, the processing apparatus determines that there is no defect. Since the coordinates of the XY stage 15 and the angle of the scanner 13 are input to the processing apparatus, the processing apparatus can specify the illumination position on the XY plane. That is, the timing at which the detection signal exceeds the threshold is set as the defect detection timing, and the processing device 19 specifies the defect coordinates from the illumination position at the defect detection timing. In this way, the presence / absence and position of the defect of the sample 20 can be detected.

  When the spot diameter of the illumination light L1 incident on the lens 14 is small, the NA of the illumination optical system 10 is small. In this case, since the depth of focus becomes deep, scattered light from a surface other than the inspection target surface enters the lens 16. The optical path of the scattered light L2 from the sample 20 to the detector 18 will be described with reference to FIG. FIG. 2 shows only a part of the configuration of the inspection apparatus 100.

  In FIG. 2, B is the inspection target surface, and A and C are surfaces other than the inspection target surface. Here, the scattered light from the inspection target surface B is referred to as scattered light L2B. Similarly, the scattered light from the surface A above the inspection target surface B (lens 14 side) is referred to as scattered light L2A, and the scattered light from the surface C below the inspection target surface B is referred to as scattered light L2C.

  As described above, the illumination light L1 is incident on the sample 20 from the upper side and is condensed on the inspection target surface B by the lens 14. The spot diameter of the illumination light L1 is the smallest on the inspection target surface B. The illumination light L1 is narrowed down from the surface A toward the inspection target surface B. Further, the illumination light L1 spreads from the inspection target surface B toward the surface C. The optical axis of the lens 16 intersects the optical axis of the lens 14 on the inspection target surface B.

  Scattered light L <b> 2 </ b> B from the inspection target surface B is collected by the lens 16 onto the opening 17 a of the slit 17. On the other hand, the scattered light L <b> 2 </ b> A from the surface A is collected at a position shifted from the opening 17 a of the slit 17. Accordingly, the scattered light L2A cannot pass through the opening 17a of the slit 17. Similarly, the scattered light L2C from the surface C is condensed at a position shifted from the opening 17a of the slit 17. Therefore, the scattered light L2C cannot pass through the opening 17a of the slit 17. Thus, only the scattered light L2B from the inspection target surface B can pass through the slit 17. That is, the scattered light L2A and L2C from the surface A other than the inspection target surface B or the surface C is shielded by the slit 17.

  Therefore, the detector 18 detects only the scattered light L2 from the inspection target surface B. It is possible to accurately detect a defect on the inspection target surface B. That is, even if there is a defect on the surface A or C, the scattered light L2A and L2C are shielded by the slit 17 and are not received by the detector 18. Therefore, the defect on the inspection target surface B can be reliably separated from the defects on the surfaces A and C other than the inspection target surface B and detected.

  Furthermore, the position of the inspection target surface can be controlled by moving the slit 17. For example, the surface A can be set as the inspection target surface by moving the slit 17 so that the illumination light L2A is condensed at the position of the opening 17a. By moving the slit 17 so that the illumination light L2C is condensed at the position of the opening 17a, the surface C can be set as the inspection target surface. In this way, the height of the inspection target surface can be adjusted by sliding the slit 17 in the direction perpendicular to the longitudinal direction of the opening 17a on the surface perpendicular to the optical axis of the lens 16. Therefore, it is possible to detect a defect on an arbitrary surface of the sample 20. When the slit 17 is moved, the detection area of the detector 18 is made sufficiently wide. That is, even if the slit 17 is moved, the detector 18 having a wide detection area is used so that the scattered light L2 that has passed through the opening 17a enters the detector 18.

  Furthermore, by changing the width of the opening 17a of the slit 17, the depth of the inspection target surface can be controlled. For example, by reducing the width of the opening 17a, the depth of field on the inspection target surface can be reduced. Alternatively, by increasing the width of the opening 17a, the depth of field on the inspection target surface can be increased. That is, when the width of the opening 17a is narrow, scattered light is blocked by the slit 17 even if the height is slightly shifted from the inspection target surface. On the other hand, when the width of the opening 17a is wide, the scattered light passes through the opening 17a and is detected by the detector 18 if the height is slightly shifted from the inspection target surface.

  Therefore, the position resolution in the height direction (Z direction) can be adjusted by changing the width of the opening 17a. Thus, by making the width of the opening 17a of the slit 17 variable, the depth of field on the inspection target surface can be controlled.

  In the above description, the slit 17 having the opening 17a in the direction corresponding to the scanning direction of the scanner 13 is used as the light shielding member. However, a configuration other than the slit 17 may be used as the light shielding member. For example, when scanning is not performed by the scanner 13, a pinhole having a dot-like opening can be used as the light shielding member. And the effect similar to the case where the slit 17 is adjusted can be acquired by adjusting the position of a pinhole and the magnitude | size (diameter) of an opening part.

  Note that a cylindrical lens may be used as the lens 16. A cylindrical lens arranged in a direction along the slit 17 may be used as the lens 16. By doing so, the amount of scattered light detected by the detector 18 can be increased.

  In addition, although the scanner 13 scans in the Y direction and the stage 15 scans in the X direction, the present invention is not limited to this configuration. For example, the scanner 13 may scan in the XY direction, or the stage 15 may scan in the XY direction.

  In the present embodiment, the detector 18 collectively detects scattered light emitted from the emission ends of the plurality of optical fibers 33 with one pixel. Thereby, since the alignment of the detector 18 becomes unnecessary, a defect can be detected easily. Of course, a line sensor such as a CCD camera having a plurality of pixels or a two-dimensional array sensor may be used as the detector 18.

(Modification)
A modification of the inspection apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 3 is a diagram showing an optical path from the sample 20 to the detector 18. The basic configuration of the inspection apparatus 100 is the same as the configuration shown in FIG.

  In the modified example, the slit 17 is not provided. Further, the detector 18 includes a plurality of pixels. As the detector 18, a two-dimensional array sensor such as a CCD camera (Charge Coupled Device) or a CMOS camera (Complementary Metal Oxide Semiconductor) can be used. Note that although FIG. 3 shows a configuration including three pixels 18a to 18c for simplification of description, the number of pixels is not particularly limited.

  The pixels 18 a to 18 c are arranged in a direction perpendicular to the direction corresponding to the scanning direction (Y direction) of the scanner 13. In addition, as described above, when the height of the inspection target surface is different, the light collection position of the scattered light by the lens 17 is shifted. Accordingly, the scattered light L2A from the surface A is incident on the pixel 18a. Scattered light L2B from the surface B is incident on the pixel 18b. Scattered light L2C from the surface C is incident on the pixel 18c. By using the detector 18 having a plurality of pixels 18a to 18c, scattered light from inspection surfaces with different heights can be separated and detected.

  A plurality of pixels 18 a to 18 c are arranged along the direction in which the light collection position of the scattered light by the lens 16 is shifted. Scattered light from different positions in the Z direction enters different pixels. In this way, it is possible to simultaneously perform defect inspections at different heights. That is, the detection signal is compared with the threshold value for each of the pixels 18a to 18c. And a defect is detected according to the comparison defect for every pixel. By doing so, inspections at different heights can be performed simultaneously. Further, the position of the defect in the Z direction can be detected.

  For example, when a two-dimensional array sensor is used as the detector 18, the inspection target surface is different for each pixel column. When the line sensor is used, the inspection target surface is different for each pixel. The lens 16 collects the scattered light on different pixels of the detector 18 according to the depth in the sample 20. Therefore, inspections at different depths (heights) can be performed simultaneously.

Embodiment 2. FIG.
The configuration of the inspection apparatus according to this embodiment will be described with reference to FIG. FIG. 4 is a diagram showing the overall configuration of the inspection apparatus 200. The present embodiment is different from the first embodiment in that an optical fiber unit 30 is provided instead of the slit 17. That is, the optical fiber unit 30 is arranged in the optical path from the sample 20 to the detector 18.

  Note that the basic configuration of the inspection apparatus 200 is the same as that of the inspection apparatus 100 shown in the first embodiment, and a description thereof will be omitted. For example, the light source 11 and the scanner 13 of the illumination optical system 10 have the same configuration as that in FIG. Therefore, as in the first embodiment, the scanner 13 scans the illumination light L1 in the Y direction. Further, the stage 15 has the same configuration as that of the first embodiment. The stage 15 is moving the sample 20 in the X direction.

  An optical fiber unit 30 is disposed above the sample 20. The optical fiber unit 30 is disposed in the vicinity of the surface of the sample 20. An optical fiber unit 30 is disposed toward the illumination position of the sample 20.

  The optical fiber unit 30 includes an optical fiber 33 and a holder 34. The holder 34 includes a first light shielding plate 31 and a second light shielding plate 32. The first light shielding plate 31 is disposed below the optical fiber 33, and the second light shielding plate 32 is disposed above. The first light shielding plate 31 and the second light shielding plate 32 serve as a holder 34 that holds the optical fiber 33 in the vertical direction. That is, the plurality of optical fibers 33 are held above the sample 20 by the holder 34.

  The optical fiber 33 is an optical fiber formed of a transparent resin, and light propagates through the optical fiber 33. For example, the diameter of the optical fiber 33 is 0.5 mm. A detector 18 is disposed on the exit end face of the optical fiber 33. The incident end face of the optical fiber 33 faces the illumination position of the sample 20. The optical fiber 33 is disposed inclined from the Z direction. Scattered light L 2 incident from the incident end face in the optical fiber 33 propagates in the optical fiber 33. Then, the scattered light L2 propagated through the optical fiber 33 is emitted from the emission end face. Scattered light L <b> 2 emitted from the emission end face of the optical fiber 33 is received by the detector 18. Thus, the optical fiber 33 serves as a light guide member that guides the scattered light L2 from the sample 20 to the detector 18. The detector 18 is a photomultiplier tube as in the first embodiment.

  The configuration of the optical fiber unit 30 will be described in detail with reference to FIG. FIG. 5 is a plan view showing the configuration of the optical fiber unit 30, and schematically shows the configuration on the incident end face side of the optical fiber 33.

  The first light shielding plate 31 and the second light shielding plate 32 sandwich the plurality of optical fibers 33. Thereby, the holder 34 can hold the plurality of optical fibers 33. For example, the first light shielding plate 31 and the second light shielding plate 32 are each formed of a flat plate. The first light shielding plate 31 and the second light shielding plate 32 are light shielding plates made of, for example, black resin. Therefore, the first light shielding plate 31 and the second light shielding plate 32 absorb the incident scattered light. A plurality of optical fibers 33 are arranged in a row between the first light shielding plate 31 and the second light shielding plate 32. Therefore, the plurality of optical fibers 33 are arranged at the same height from the surface of the sample 20. The plurality of optical fibers 33 are arranged along the Y direction. In plan view parallel to the incident end face, the first light shielding plate 31 and the second light shielding plate 32 hold the plurality of optical fibers 33 in a direction perpendicular to the arrangement direction.

  As described above, by arranging the plurality of optical fibers 33 in a line, scattered light from the illumination position scanned in the Y direction by the scanner 13 can be appropriately detected. The incident end faces of the plurality of optical fibers 33 may be arranged on the same plane. What is necessary is just to change the arrangement | positioning by the side of the output end surface of the some optical fiber 33 according to the detection area | region of the detector 18. FIG. That is, the plurality of optical fibers 33 may be bundled so that scattered light from the emission end faces of the plurality of optical fibers 33 is received by the detector 18. Of course, the arrangement of the plurality of optical fibers 33 on the incident end face side is not limited to one row. For example, a plurality of optical fibers 33 may be arranged in two or more rows. Alternatively, if the illumination light L1 is not scanned in the Y direction, the plurality of optical fibers 33 may not be arranged in a line.

  The state of the scattered light incident on the optical fiber unit 30 is shown in FIG. FIG. 6 is a diagram schematically illustrating an optical path of scattered light. In FIG. 6, a part of the configuration shown in FIG. 4 is omitted. In FIG. 6, the illumination light L <b> 1 is collected on the inspection target surface B.

  The plurality of optical fibers 33 are arranged along a direction inclined from the Z direction. The holder 34 protrudes toward the illumination position from the incident end surface 33a of the optical fiber 33. That is, the end 31a on the illumination position side of the first light shielding plate 31 and the end 32a on the illumination position side of the second light shielding plate 32 are arranged on the illumination position side of the incident end face 33a. The first light shielding plate 31 or the second light shielding plate 32 shields part of the scattered light from the sample 20.

  Scattered light from surfaces A and C other than the inspection target surface B is shielded by the first light shielding plate 31 or the second light shielding plate 32. That is, scattered light from surfaces A and C other than the inspection target surface B cannot pass through the gap between the first light shielding plate 31 and the second light shielding plate 32. Scattered light from surfaces A and C other than the inspection target surface B is incident on the first light shielding plate 31 or the second light shielding plate 32. Scattered light from surfaces A and C other than the inspection target surface B is shielded by the first light shielding plate 31 or the second light shielding plate 32 and does not enter the incident end surface 33 a of the optical fiber 33.

  On the other hand, only the scattered light L <b> 2 </ b> B from the inspection target surface B enters the incident end surface 33 a of the optical fiber 33. That is, a part of the scattered light L2B from the inspection target surface B passes through the gap between the first light shielding plate 31 and the second light shielding plate 32 and enters the optical fiber 33. The scattered light L2B incident on the incident end face 33a of the optical fiber 33 propagates through the optical fiber 33 and exits from the exit end face 33c. The scattered light L2B emitted from the emission end face 33c is detected by the detector 18 (not shown in FIG. 6).

  In the present embodiment, a first light shielding plate 31 and a second light shielding plate 32 that cover at least a part of the side surface 33b of the optical fiber 33 are provided. The first light shielding plate 31 and the second light shielding plate 32 protrude from the illumination position side with respect to the optical fiber 33. With this configuration, the NA of the optical fiber 33 can be further limited. That is, the NA of the detection optical system can be made smaller than the NA of the optical fiber 33. Thereby, the height of the detection target surface can be limited. Scattered light from surfaces A and C other than the predetermined inspection target surface B is absorbed by the holder 34. Thereby, only the defect of the surface B to be inspected can be detected.

  In the present embodiment, the holder 34 that holds the plurality of optical fibers 33 is disposed in the vicinity of the illumination position of the sample 20. Therefore, it is possible to detect only scattered light from a desired inspection target surface with a simple configuration. For example, alignment of the lens 16, the slit 17, and the detector 18 is not necessary. With a simple configuration, it is possible to accurately detect defects on the inspection target surface in the sample with a simple configuration. That is, it is possible to detect defects on the inspection target surface by distinguishing them from defects on surfaces other than the inspection target surface. A plurality of fibers 33 are held by a holder 34 protruding from the incident end face 33a. Therefore, the apparatus configuration can be simplified.

  Further, the scattered light from the sample 20 is directly incident on the optical fiber 33 without arranging the lens 16 between the optical fiber unit 30 and the sample 20. Since the lens 16 is not used, the influence of lens aberration can be eliminated. The normal lens 16 has a configuration in which a plurality of lenses are accommodated in a cylindrical lens barrel. When the cylindrical lens 16 is used, the installation space is limited, and it is difficult to approach the vicinity of the sample 20. By using a detection optical system that does not use the lens 16 as in the present embodiment, the optical fiber unit 30 can be disposed close to the sample 20. More scattered light can be incident on the detector 18 than in the configuration of FIG. 1 using the lens 16. Thereby, the detection light quantity of scattered light can be made high and a defect can be detected with higher sensitivity.

  For example, the optical fiber unit 30 is disposed at a height of 0.5 mm from the surface of the sample 20. That is, the distance from the surface of the sample 20 to the lower end of the optical fiber unit 30 is 0.5 mm. Thus, since the optical fiber unit 30 can be disposed in the vicinity of the sample 20, the intensity of scattered light received by the detector 18 can be increased. Therefore, defects can be detected with higher sensitivity than in the first embodiment.

  The detector 18 may collectively detect scattered light emitted from the emission ends of the plurality of optical fibers 33 by one pixel. Thereby, since the alignment of the detector 18 becomes unnecessary, a defect can be detected easily. The illumination optical system 10 is provided with a scanner 13 that scans illumination light in the Y direction. A plurality of optical fibers 33 may be arranged along the Y direction. Thereby, since the alignment of the detector 18 becomes unnecessary, a defect can be detected easily.

  Furthermore, since the lens 16 is not used, the scanning range by the scanner 13 can be easily widened. By increasing the number of optical fibers 33 arranged, the scanning range of the scanner 13 can be widened. On the other hand, when the lens 16 is used, it is necessary to increase the diameter of the lens 16 when the scanning range by the scanner 13 is widened. When the diameter of the lens 16 is increased, an expensive lens 16 is required. By using the optical fiber unit 30 without using the lens 16 as in the present embodiment, an inexpensive device configuration can be realized.

  Furthermore, it is preferable that the optical fiber unit 30 is arranged so as to be movable in the vertical direction (Z direction). For example, the optical fiber unit 30 moves in the direction of arrow D in FIG. In this way, the height of the inspection target surface can be changed. The optical fiber unit 30 is moved up and down so as to change the distance between the optical fiber unit 30 and the sample 20. For example, the holder 34 may be driven up and down by an actuator (not shown) such as a motor. The holder 34 holding the optical fiber 33 is raised in the direction of arrow D in FIG. By doing so, only the scattered light L <b> 2 </ b> A enters the optical fiber 33. Therefore, the surface A can be the inspection target surface. Alternatively, the inspection target surface C can be inspected by lowering the holder 34 that holds the optical fiber 33 (not shown).

  By doing so, the height of the inspection object surface can be easily controlled. Therefore, the defects on the surfaces A, B, and C can be detected separately. The moving direction of the sample 20 and the optical fiber unit 30 may be parallel to the Z direction or may be inclined from the Z direction. That is, the holder 34 may be provided so as to be movable in the Z direction perpendicular to the surface of the sample 20. By doing so, the surface to be inspected can be easily adjusted to an arbitrary height.

  Furthermore, it is preferable that the distance between the end portions 31 a and 32 a on the illumination position side of the holder 34 and the incident end surfaces 33 a of the plurality of optical fibers 33 is variable. For example, the optical fiber 33 is moved along the direction of arrow E. Thereby, the depth of the surface to be inspected can be controlled. For example, each optical fiber 33 is pushed into the illumination position side from the rear side of the holder 34 in the direction of arrow E in FIG. By doing so, the incident end face 33a of the optical fiber 33 can be brought close to the illumination position. The distance from the end portions 31a and 32a on the illumination position side of the holder 34 to the incident end surface 33a is shortened. Therefore, the NA of the detection optical system that detects scattered light can be further increased. It is possible to increase the depth of field on the inspection target surface.

  Alternatively, by pulling out a part of each optical fiber 33 from the rear side of the holder 34, the incident end face 33a of the optical fiber 33 can be moved away from the illumination position (not shown). By doing so, the distance from the end portions 31a, 32a on the illumination position side of the holder 34 to the incident end face 33a is increased. Therefore, the NA of the detection optical system that detects scattered light can be further reduced. It is possible to reduce the depth of field on the inspection target surface.

  As described above, the depth of the inspection target surface can be controlled by changing the protrusion amount of the holder 34 protruding from the incident end surface 33a. Note that the depth of the inspection target surface may be controlled by moving the holder 34 instead of the optical fiber 33. That is, at least one of the first light shielding plate 31 and the second light shielding plate 32 may be moved closer to or away from the illumination position. Even if it does in this way, the same effect can be acquired. Since the distance between the end portions 31a and 32a on the illumination position side of the holder 34 and the incident end surfaces 33a of the plurality of optical fibers 33 is variable, adjustment can be easily performed. The distances from the incident end faces 33a of the plurality of optical fibers 33 may be changed by an actuator such as a motor, or may be changed manually by an operator.

  In the inspection apparatus 200, the end 31a of the first light-shielding plate 31 and the end 32a of the second light-shielding plate 32 are configured to protrude toward the illumination position from the incident end face 33a. The configuration is not limited to this. For example, only the end portion 31a of the first light shielding plate 31 may be configured to protrude to the illumination position side from the incident end surface 33a. Only the end portion 32a of the second light shielding plate 32 may be configured to protrude to the illumination position side from the incident end surface 33a. Further, the configuration of the holder 34 is not limited to the configuration in which the first light shielding plate 31 and the second light shielding plate 32 sandwich the optical fiber 33 from above and below as shown in FIG. That is, the holder 34 may have any configuration as long as it can hold the optical fiber 33.

  As mentioned above, although embodiment of this invention was described, this invention contains the appropriate deformation | transformation which does not impair the objective and advantage, Furthermore, it does not receive the restriction | limiting by said embodiment.

DESCRIPTION OF SYMBOLS 100 Inspection apparatus 200 Inspection apparatus 10 Illumination optical system 11 Light source 13 Scanner 14 Lens 15 XY stage 16 Lens 17 Slit 18 Detector 19 Processing apparatus 20 Sample 30 Optical fiber unit 31 1st light shielding plate 32 2nd light shielding plate 33 Optical fiber 34 Holder

Claims (5)

An illumination optical system for illuminating a transparent sample with dark field; and
A detector for detecting scattered light scattered by the sample;
A plurality of optical fibers for guiding scattered light scattered by the sample to the detector;
A holder for holding the plurality of optical fibers, Bei example and a holder which protrudes illumination position side of the sample than the incident end face of said plurality of optical fibers,
An inspection apparatus in which a distance between an end portion on the illumination position side of the holder and an incident end face of the plurality of optical fibers is variable .   The inspection apparatus according to claim 1, wherein the holder is movably provided in a direction perpendicular to the surface of the sample. The inspection apparatus according to claim 1, wherein the detector collectively detects the scattered light emitted from the emission ends of the plurality of optical fibers by one pixel. The illumination optical system is provided with a scanner that scans illumination light in a first direction,
The inspection apparatus according to claim 1 , wherein the plurality of optical fibers are arranged along the first direction. Illuminating a transparent sample with dark field; and
Allowing the scattered light from the illumination position of the sample illuminated in the dark field to enter the optical fiber;
Detecting the scattered light propagating in the optical fiber with a detector,
A plurality of the optical fibers are provided,
A plurality of the optical fibers are held by a holder protruding to the illumination position side from the incident end face of the optical fiber ,
An inspection method in which a distance between an end portion on the illumination position side of the holder and an incident end face of the plurality of optical fibers is variable .

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