JP2020016497A - Inspection device and inspection method - Google Patents

Abstract

To provide an inspection device and an inspection method with which it is possible to specify the color of a defective pixel.SOLUTION: An inspection device 100 pertaining to one embodiment of the present invention inspects a sample 20 having a color filter pattern in which pixels in a plurality of colors are arranged in array form. The inspection device 100 comprises: a light source 10 for generating illumination light L1 with which the sample 20 is irradiated; a detector 11 for detecting diffracted light L3 from an illumination area illuminated by the illumination light L1; and a processing device for performing inspection on the basis of the result of detection by the detector 11. The processing device 50 acquires a sample image under a first and a second condition. The processing device 50 detects a defect on the basis of images of the sample under the first and second conditions and specifies the color of a defective pixel on the basis of the result of detection under the first and second conditions.SELECTED DRAWING: Figure 1

Description

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

  Patent Literature 1 discloses a defect inspection method for inspecting a defect of an image sensor. In the defect inspection method of Patent Literature 1, image data obtained from each of a plurality of imaging elements formed on a semiconductor wafer is used. Specifically, four image data are acquired by illuminating four image sensors under the same image capturing conditions. Then, a synthesized image obtained by synthesizing the four image data is displayed, and a visual sensory test is performed.

  Patent Literature 2 discloses an inspection device for an image sensor on which a color filter is formed. In Patent Literature 2, a monitor area is formed outside a pixel area of an image sensor. An anti-reflection film, a light-shielding pattern, a flattening film, a color filter, and a lens are formed in the pixels in the monitor region. The monitor area is provided with a plurality of pixels having different light-shielding patterns in a planar arrangement.

JP 2008-28180 A JP 2016-9826 A

  2. Description of the Related Art In a defect inspection in an image pickup device manufacturing process, there is an optical defect inspection device that detects reflected light from an image pickup device illuminated by illumination light with a detector. In the inspection using reflected light, a defect is detected based on the detection intensity of the reflected light. When a defect generated in a pixel provided with a color filter pattern is detected using reflected light, there are the following problems.

  When an image sensor is imaged by a low magnification detector, information from pixels of different colors is mixed in the reflected light. In the optical inspection at a low magnification, the light receiving pixels of the detector collectively receive the light reflected by the pixels of different colors. Therefore, there is a problem that the color of the defective pixel cannot be specified.

  The present disclosure has been made in view of such circumstances, and provides an inspection apparatus and an inspection method capable of specifying the color of a pixel having a defect.

  An inspection device according to an aspect of the present embodiment is an inspection device for a sample having a color filter pattern in which pixels of a plurality of colors are arranged in an array, and a light source that generates illumination light for illuminating the sample. A detector that detects diffracted light from an illumination area illuminated by the illumination light, and a processing device that performs an inspection based on a detection result of the detector, wherein the processing device has a first condition, And obtaining an image of the sample under the second condition, detecting a defect based on the image of the sample under the first condition and the second condition, and detecting the defect under the first condition and the second condition. Is used to specify the color of a defective pixel.

  In the above inspection device, under the first condition, a difference in pixel reflectance between the pixel of the first color and the pixel of the second color is different from the pixel of the second color and the pixel of the third color. The difference in pixel reflectance between the pixel of the second color and the pixel of the third color is greater than the first pixel in the second condition under the second condition. Preferably, the difference in pixel reflectance between the color pixel and the second color pixel is larger.

  In the above inspection apparatus, when a defect is detected under the first condition and no defect is detected under the second condition, the pixel having the defect is identified as having the first color, and the first pixel is identified. If no defect is detected under the condition and a defect is detected under the second condition, the defective pixel is identified as having the third color, and a defect is detected under the first condition. Further, when a defect is detected under the second condition, the pixel having the defect may be specified as the second color.

  In the above inspection device, in the color filter pattern, pixels of the first color and pixels of the second color are alternately arranged in the first pixel column, and the first color pixel and the second color pixel are arranged next to each other. In the second pixel column, the pixels of the second color and the pixels of the third color may be alternately arranged.

  In the above inspection apparatus, the wavelength of light detected by the detector is λ, the illumination angle of the illumination light with respect to the sample is α, the detection angle of the detector with respect to the sample is β, and the repetition period of the pixel is d. When n is an integer other than 0, it is preferable that the first condition and the second condition are conditions that satisfy dsinα + dsinβ = nλ.

  An inspection method according to an aspect of the present embodiment is an inspection method using an inspection device that inspects a sample having a color filter pattern in which pixels of a plurality of colors are arranged in an array. A light source that generates illumination light to be illuminated, and a detector that detects diffracted light from an illumination area illuminated with the illumination light, and obtains an image of the sample under the first condition and the second condition, respectively. Detecting a defect based on the image of the sample under the first condition and the second condition, and specifying a color of a defective pixel based on the detection result under the first condition and the second condition Is what you do.

  In the above-described inspection method, under the first condition, a difference in pixel reflectance between a pixel of the first color and a pixel of the second color is different from that of a pixel of the second color and a pixel of the third color. The difference in pixel reflectance between the pixel of the second color and the pixel of the third color is greater than the first pixel in the second condition under the second condition. Preferably, the difference in pixel reflectance between the color pixel and the second color pixel is larger.

  In the above-described inspection method, when a defect is detected under the first condition and no defect is detected under the second condition, the defective pixel is identified as having the first color, and the first pixel is identified. If no defect is detected under the condition and a defect is detected under the second condition, the defective pixel is identified as having the third color, and a defect is detected under the first condition. Further, when a defect is detected under the second condition, the pixel having the defect may be specified as the second color.

  In the color filter pattern, in a first pixel column, pixels of a first color and pixels of a second color are alternately arranged, and in a second pixel column adjacent to the first pixel column, The pixels of the second color and the pixels of the third color may be alternately arranged.

  In the above inspection method, the wavelength of light detected by the detector is λ, the illumination angle of the illumination light with respect to the sample is α, the detection angle of the detector with respect to the sample is β, and the repetition period of the pixel is d. When n is an integer other than 0, it is preferable that the first condition and the second condition are conditions that satisfy dsinα + dsinβ = nλ.

  An inspection apparatus according to an aspect of the present embodiment is an inspection apparatus for a sample having a color filter pattern in which a plurality of pixels are used as a repeating unit and a pixel array of the repeating unit is repeatedly arranged in first and second directions. A light source that generates illumination light for illuminating the sample, a detector that detects diffracted light from an illumination area illuminated with the illumination light, and a process of performing an inspection based on a detection result of the detector And a processing device, wherein the processing device acquires an image of the sample under a first condition and a second condition in which the direction of the pixel array with respect to the illumination direction of the illumination light is different, and the first condition and the second condition A defect is detected based on an image of the sample under the condition, and a position of a defective pixel in the repeating unit is specified based on a detection result under the first condition and the second condition.

  In the above inspection apparatus, it is preferable that, under the first condition and the second condition, the direction of the pixel array with respect to the illumination direction of the illumination light is different by 90 °.

    The inspection method according to an aspect of the present embodiment is an inspection method for inspecting a sample having a color filter pattern in which a plurality of pixels are used as a repeating unit and a pixel array of the repeating unit is repeatedly arranged in first and second directions. An inspection method using an apparatus, wherein the inspection apparatus includes a light source that generates illumination light that illuminates the sample, and a detector that detects diffracted light from an illumination area illuminated with the illumination light. Acquiring an image of the sample under first and second conditions in which the direction of the pixel array with respect to the illumination direction of the illumination light is different, and based on the image of the sample under the first and second conditions. An inspection device that detects a defect and specifies a position of a defective pixel in the repeating unit based on the detection result under the first condition and the second condition.

  In the above inspection apparatus, it is preferable that, under the first condition and the second condition, the direction of the pixel array with respect to the illumination direction of the illumination light is different by 90 °.

  According to the present disclosure, it is possible to provide an inspection apparatus and an inspection method capable of specifying a color of a pixel having a defect.

It is a figure showing the composition of the inspection device concerning this embodiment. It is a process sectional view showing a manufacturing process of a color filter pattern. FIG. 3 is a diagram illustrating a pixel array of a color filter pattern. It is a figure for explaining a reflected light pattern and diffraction light intensity when a pixel reflectance is changed. FIG. 9 is a diagram for explaining a process of specifying a color in which a defect exists based on a defect detection result under a first condition and a second condition. FIG. 13 is a diagram illustrating a pixel array when the Bayer array is rotated by 90 ° in the second embodiment. FIG. 17 is a diagram illustrating a pixel array when the RCCC array is rotated by 90 ° in the third embodiment.

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

  The inspection device according to the present embodiment is a macro inspection device that inspects a sample such as a semiconductor wafer on which a fine pattern is formed. The inspection device performs a macro inspection based on the reflection luminance value of the sample image. Specifically, the inspection device detects a defect of the sample provided with the color filter pattern. The color filter pattern is used for an image sensor or a display device, and includes a plurality of pixels arranged in an array. In the following description, a semiconductor wafer on which an image sensor chip such as a charge-coupled device (CCD) sensor or a complementary metal-oxide-semiconductor (CMOS) sensor is formed is used as a sample.

Embodiment 1 FIG.
An inspection apparatus and an inspection method according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating the entire configuration of the inspection apparatus. The inspection device 100 includes a light source 10, a detector 11, a filter 13, a filter 14, a stage 30, and a processing device 50. Note that an optical element other than the configuration illustrated in FIG. 1, for example, a lens or a mirror may be appropriately provided in the optical system. When the monochromatic light source 10 is used, the filters 13 and 14 become unnecessary.

  FIG. 1 shows an XYZ three-dimensional orthogonal coordinate system for clarity of explanation. Note that the Z direction is a vertical direction, and is a direction parallel to the thickness direction of the sample 20. The Z direction is the normal direction of the pattern formation surface of the sample 20. The X direction and the Y direction are horizontal directions, and are directions parallel to the pixel arrangement direction of the sample 20.

  The sample 20 to be inspected is mounted on the stage 30. The color filter pattern (not shown in FIG. 1) is formed on the upper surface of the sample 20 as described above. The color filter pattern includes pixels repeatedly arranged at a predetermined pitch in the X direction and the Y direction. Each pixel of the color filter pattern is formed with one of the first to third colored layers. Specifically, colored layers of red (R), green (G), and blue (B) are arranged in an array. Each colored layer has a property of transmitting only light of the corresponding color. The detailed pixel configuration of the color filter pattern will be described later. The inspection apparatus 100 according to the present embodiment specifies the color of a defective pixel.

  The light source 10 and the detector 11 are arranged on the sample 20. The light source 10 is, for example, a linear light source that generates linear illumination light L1. The illumination light uniformly illuminates a linear illumination area on the surface of the sample 20 along the Y direction. Alternatively, the light source 10 may emit ring-shaped or planar illumination light. The illumination light L1 from the light source 10 may be focused on the surface of the sample 20 by a lens. The light source 10 emits illumination light L1 such as visible light, ultraviolet light, or infrared light.

  The light source 10 illuminates the sample 20 from an oblique direction, that is, a direction inclined from the Z axis. Alternatively, the light source 10 may illuminate the sample 20 from a direction parallel to the Z axis. In the XZ plane, the angle between the optical axis of the illumination light L1 and the Z axis is the illumination angle α. The incident angle of the illumination light L1 on the optical axis is the illumination angle α. The illumination light L1 illuminates the sample 20 from a direction inclined from the Z axis by an illumination angle α. The optical system of the illumination light L1 may be provided with a lens, an optical scanner, a mirror, and the like.

  The illumination light L1 from the light source 10 forms a linear illumination area on the surface of the sample 20. For example, the illumination light L1 may be focused on the pattern surface of the sample 20 by a lens (not shown). The illumination light L1 is reflected on the surface of the sample 20. The light reflected regularly in the illumination area is referred to as regular reflected light L2. The regular reflection light L2 propagates along an optical axis inclined by an angle α from the Z axis. Note that the regular reflection light L2 is a zero-order diffracted light. Further, the diffracted light diffracted in the illumination area is referred to as diffracted light L3. That is, since a repetitive pattern is formed on the surface of the sample 20, diffracted light L3 is generated. The diffracted light L3 is a reflected diffracted light reflected on the surface of the sample 20. The diffracted light L3 and the specularly reflected light L2 propagate along optical axes at different angles.

  The detector 11 detects the diffracted light L3 from the illumination area. For example, a lens (not shown) may form an image of the diffracted light L3 on the light receiving surface of the detector 11. The detector 11 detects the diffracted light L3 from an oblique direction, that is, a direction inclined from the Z axis. The angle of the detector 11 with respect to the sample 20 is defined as a detection angle β. The angle formed between the Z axis and the optical axis of the detector 11 is the detection angle β.

  The detection angle β corresponds to the direction in which the diffracted light propagates. For example, the detection angle β is adjusted so that the diffracted light L3 propagates along the optical axis of the detection optical system and enters the detector 11. Further, the detector 11 is arranged so as not to detect the regular reflection light L2. That is, the detection optical system is arranged such that the specularly reflected light L2 that is specularly reflected from the illumination area at an angle α passes outside the detector 11.

  The detector 11 is a line sensor camera in which light receiving pixels are arranged in the Y direction. For example, the detector 11 images the sample 20 using a CCD line sensor or the like. The intensity and the diffraction angle of the diffracted light L3 change depending on the pitch and size of the pattern. Since the intensity of the diffracted light L3 changes according to the surface state of the sample 20, the color of the colored layer, the film thickness, the pattern size, the light wavelength, the underlying structure, and the like, the luminance value at the detector 11 changes.

  Then, the detector 11 images the sample 20 while changing the relative position between the sample 20 and the illumination area. Specifically, the stage 30 is movable in the X direction. While moving the stage 30 in the X direction, the detector 11 detects diffracted light L3 from the illumination area illuminated by the light source 10. Then, detection data corresponding to the luminance of the diffracted light L3 detected by the detector 11 is input to the processing device 50. Further, the processing device 50 controls the driving of the stage 30. Then, the processing device 50 visualizes the luminance change of the light detected by the detector 11. By doing so, a diffracted light image of the entire surface of the sample 20 can be obtained.

  In this manner, the processing device 50 acquires an image of the sample 20. The processing device 50 performs an inspection based on the acquired sample image. When the sample 20 has a defect, the intensity of the diffracted light L3 changes, so that the brightness of the sample image changes. For example, in a portion having a defect, the brightness of the sample image decreases. Alternatively, the brightness of the sample image is increased in a portion having a defect. Therefore, a defect can be detected according to a change in luminance of the sample image. Note that the inspection apparatus 100 can detect variations in the pattern dimensions and film thickness of the colored layer, foreign substances attached to the surface, and the like as defects.

  Further, the processing device 50 can selectively extract the illumination wavelength or the detection wavelength by inserting and removing the filters 13 and 14. Thus, the sample can be imaged under different imaging conditions. The processing device 50 detects a defect based on the sample image. Further, the processing device 50 specifies the color of the defective pixel based on the detection result of the defect under different conditions. The detailed processing of the processing device 50 will be described later.

  Further, a filter 13 is arranged between the light source 10 and the sample 20. Further, a filter 14 is arranged between the sample 20 and the detector 11. The filters 13 and 14 are, for example, wavelength selection filters such as band-pass filters. Actually, a plurality of filters 13 and 14 are arranged in the optical path so as to be insertable and removable. For example, one bandpass filter selected from a plurality of bandpass filters is inserted into the optical path as the filter 13 or the filter 14. By using a band-pass filter as the filter 13 or the filter 14, the detected light can be made monochromatic.

  Thereby, the wavelength λ of the diffracted light L3 detected by the detector 11 can be selected. The filter 13 serves as means for changing the illumination wavelength. As described above, the imaging condition can be changed by disposing the filter 13 in the optical path or removing the filter 13 from the optical path. In FIG. 1, the filter 13 is disposed in the optical path of the illumination light L1. Although the filter 14 is provided in the optical path of the diffracted light L3, only one of the filters may be provided. Alternatively, the wavelength may be switched by switching a plurality of light sources. By using the light source 10 as a monochromatic light source, the filters 13 and 14 can be omitted. Further, in order to change the imaging condition, the illumination angle and the detection angle may be changed.

  Further, the angle between the light source 10 and the detector 11 is variable. For example, by rotating the light source 10 around the Y axis, the illumination angle α of the illumination light L1 can be changed (see arrow A in FIG. 1). Further, by rotating the detector 11 around the Y axis, the detection angle β detected by the detector 11 can be changed (see the arrow B in FIG. 1).

  The angle between the light source 10 and the detector 11 can be adjusted independently. That is, the illumination angle α and the detection angle β can be changed independently. Alternatively, the angle of the illumination light and the detector 11 may be changed by tilting the stage 30 around the X axis or the Y axis. When the light source 10 or the detector 11 is moved to change the detection angle, the filter 13 or the filter 14 also moves.

  Further, the stage 30 can rotate around the Z axis. Thereby, the angle of the sample 20 can be changed in the XY plane. That is, the arrangement angle of the pattern with respect to the illumination light can be changed.

Here, the inspection apparatus 100 captures an image of the sample under an imaging condition that satisfies the diffraction condition expression shown in Expression (1).
dsinα + dsinβ = nλ (1)

  Here, λ is the wavelength of light, and d is the repetition period of the pattern. α is the illumination angle and β is the detection angle. n is an integer indicating the order of the diffracted light, and can be any integer other than 0.

  The light receiving pixel size of the detector 11 is, for example, about several μm to several tens μm, and the pixel size on the sample 20 is also about the same. As the detector 11, a line sensor in which photodiodes are arranged in a line can be used. The detector 11 and the light source 10 are arranged to be inclined with respect to the Z direction. The pattern size of the color filter on the sample 20 is sufficiently smaller than the pixel size of the detector 11 on the sample 20.

  The light source 10 illuminates the entire sample 20 at one time in the Y direction. That is, an optical system with a low magnification and a wide field of view is used. The light receiving pixel size of the detector 11 is larger than the pixel size of the color filter pattern. Therefore, one light receiving pixel of the detector 11 receives diffracted light from a plurality of pixels formed on the sample 20. As described above, the inspection can be performed at a high throughput by the low-magnification optical system, so that the inspection at 10 to 150 sheets / h can be performed. Since the throughput is high, it is possible to inspect all the wafers in the manufacturing process.

  Here, the processing device 50 is, for example, an information processing device such as a personal computer, and performs processing on the acquired sample image. The processing device 50 detects a defect by comparing the luminance value of the sample image acquired by the detector 11 with a threshold value. For example, a portion where the luminance value is lower than the threshold is defined as a defective portion. When a defect is detected, the productivity is improved by feeding back to a manufacturing process or the like and performing a rework process.

  By adjusting the imaging condition and receiving the diffracted light L3, it is possible to extract only information from pixels of a specific color. Therefore, the inspection apparatus 100 acquires a sample image while changing the imaging conditions. The imaging conditions include the angle of the illumination light around the Y axis, the angle of the detector 11 around the Y axis, the angle of the sample 20 around the Z axis, the illumination light wavelength, the illumination light polarization, the detection light wavelength, and the detection light polarization. And the spot shape of the illumination light on the sample 20. At least, the angle of the illumination light around the Y axis, the angle of the detector 11 around the Y axis, the angle of the sample 20 around the Z axis, the illumination light wavelength, the illumination light polarization, the detection light wavelength, the detection light polarization, and the illumination. A plurality of sample images are acquired by changing one or more of the light spot shapes. This makes it possible to easily select an appropriate imaging condition.

  The inspection apparatus 100 acquires an image of the sample 20 under the first condition and the second condition, respectively. The processing device 50 detects a defect based on the image of the sample under the first condition and the second condition. Note that the first condition and the second condition are conditions that satisfy the diffraction condition expression shown in Expression (1). The processing device 50 specifies the color of the defective colored layer based on the detection results under the first condition and the second condition. The processing in the processing device 50 will be described later.

  Next, the pixel configuration of the sample 20 will be described. FIG. 2 is a diagram schematically showing a manufacturing process of the color filter pattern provided on the sample 20. FIG. 2 shows a step of forming a colored layer on the base film 24 in the order of G, B, and R. Of course, the order of film formation is not limited to the order shown in FIG.

  First, a pattern of the G colored layer 22 is formed on the base film 24 at a position to be a G pixel. The G colored layers 22 are patterned in a staggered arrangement. Further, a pattern of the B colored layer 23 is formed on the base film 24 at a position to be a B pixel. Then, a pattern of the R colored layer 21 is formed on the base film 24 at a position to be an R pixel. The G colored layer 22 has a characteristic of selectively transmitting green wavelength light. The B colored layer 23 has a property of selectively transmitting light of a blue wavelength, and the R colored layer 21 has a property of selectively transmitting light of a red wavelength. The patterns of the colored layers 21, 22, and 23 are formed by applying, exposing, and developing a photosensitive resin, respectively.

  In the sample 20 on which the color filters are formed, the patterns of the colored layers 21, 22, and 23 are repeatedly arranged at a predetermined pitch. The base film 24 is, for example, a flattening film. Under the base film 24, semiconductor elements such as photodiodes and CCDs (not shown) are formed. In the case of a color filter pattern for an image sensor, an on-chip lens or the like is further formed on the colored layer. Therefore, it is preferable to make the heights and shapes of the coloring layers 21, 22, and 23 uniform.

  On the base film 24, RGB coloring layers 21 to 23 are sequentially formed. Therefore, the surface condition of the base film 24 differs in the step of forming each of the coloring layers 21 to 23. For example, the R colored layer 21 is patterned with the G colored layer 22 and the B colored layer 23 formed on the surface of the base film 24. The second and subsequent color layers are coated with a photosensitive resin in a state where a concavo-convex pattern (that is, a first color layer) is formed on the base film 24. Therefore, it becomes difficult to apply the photosensitive resin with a uniform film thickness. Further, the number of times of immersion in the developer differs for each colored layer. For example, the G color layer 22 applied first is immersed in the developer three times. Therefore, it is difficult to uniformly form the colored layers 21 to 23 of all colors due to process variations and the like.

  It is desired to evaluate manufacturing variations of the coloring layers 21 to 23. However, since the colored layers 21 to 23 of the color filter pattern limit the wavelength of transmitted light, it is difficult to inspect using the reflected light. For example, when the inspection is performed at a low magnification, one light receiving pixel of the detector 11 includes information of a plurality of pixels of the sample 20. That is, information of the RGB colored layers 21 to 23 is mixed in one light receiving pixel of the detector 11. Furthermore, in a color filter for an image sensor, it is difficult to detect transmitted light because the base is a semiconductor wafer. Therefore, it is difficult to specify the color of the pixel having the defect in the inspection at a low magnification. Therefore, in the present embodiment, the color of the pixel is specified by detecting the diffracted light L3 while changing the imaging conditions.

  FIG. 3 is a diagram showing a pixel array of the color filter pattern 25. In FIG. 3, the pixel array of the color filter pattern 25 is a Bayer array. FIG. 3 shows 6 × 8 = 48 pixels. Here, a red pixel is a pixel 26R, a green pixel is a pixel 26G, and a blue pixel is a pixel 26B. Pixels are arranged at regular intervals.

  In the first pixel column 28 (for example, the first column from the top), the pixels 26G and the pixels 26R are alternately arranged. In the second pixel column 29 (for example, the second column from the top), the pixels 26B and Pixels 26G are alternately arranged. A pixel adjacent to the pixel 26G in the first pixel column 28 in the −Y direction is a pixel 26B. A pixel adjacent to the pixel 26R in the first pixel column 28 in the −Y direction is a G pixel 26G. Further, the first pixel columns 28 and the second pixel columns 29 are alternately arranged.

  In the Bayer array, the pixel arrangement is different between odd-numbered pixel columns and even-numbered pixel columns. In the odd-numbered pixel columns, the pixels of the first color (R) and the pixels of the second color (G) are alternately arranged. In the even-numbered pixel columns, the pixels of the second color (G) and the third color (G) are arranged. The pixels of the color (B) are alternately arranged. Therefore, the four pixels of the G pixel, the R pixel, the B pixel, and the G pixel (dotted frame in FIG. 3) are set as one repetition unit 27, and the repetition unit 27 repeats in the X direction and the Y direction. Are arranged.

  Next, conditions for capturing a sample image will be described with reference to FIG. FIG. 4 is a diagram illustrating a reflected light pattern due to a difference in pixel reflectance. Specifically, FIG. 4 shows the reflected light pattern and the diffracted light intensity when the pixel reflectance is changed in the pixel arrangement shown in FIG. Note that the pixel reflectance is the reflectance of specular light reflected on the surface of the pixel, and is shown in the range of 0% to 100%. Since the pixel reflectance is the reflectance of specularly reflected light, the pixel reflectance varies depending on the wavelength of light, the illumination angle, and the polarization condition. As the pixel reflectance, for example, a value measured in advance can be used.

  The pixel reflectance of the R pixel R is Rr, the pixel reflectance of the G pixel is Rg, and the pixel reflectance of the B pixel is Rb. Further, the pixel reflectances Rr, Rg, and Rb change according to the wavelength of the illumination light. In FIG. 4, pixels with higher pixel reflectivity are shown in a brighter pattern, and pixels with lower pixel reflectivity are shown in a darker pattern. FIG. 4 shows conditions A to C in which the ratio of the pixel reflectances Rr, Rg, and Rb is changed.

  Under condition A, the ratio (Rr / Rg) is increased and the ratio (Rb / Rg) is decreased. Under the condition A, the diffracted light at the first pixel row 28 is stronger than the diffracted light at the second pixel row 29. Therefore, the diffraction peak of the diffracted light from the first pixel row 28 becomes bright. Therefore, the sample image acquired under the condition A that satisfies the diffraction condition contains much information on the reflected light from the GR pattern.

  Under condition B, the ratio (Rr / Rg) is increased, and the ratio (Rb / Rg) is increased. Under the condition B, the diffracted light in the first pixel row 28 and the diffracted light in the second pixel row 29 become as strong as each other. Therefore, the diffraction peak of the diffracted light from the first pixel row 28 and the second pixel row 29 becomes bright. Therefore, the sample image acquired under the condition B that satisfies the diffraction condition includes the reflected light information from the GR pattern and the reflected light information from the GB pattern to the same extent.

  Under the condition C, the ratio (Rr / Rg) is reduced and the ratio (Rb / Rg) is increased. Under the condition C, the amplitude of the diffracted light in the second pixel row 29 is larger than the amplitude of the diffracted light in the first pixel row 28. Therefore, the diffraction peak from the second pixel column 29 becomes bright. Therefore, the sample image acquired under the condition C that satisfies the diffraction condition contains much information on the reflected light from the GB pattern.

  By changing the conditions related to the pixel reflectance in this way, more specific color information can be included in the sample image. For example, by changing the transmission wavelength of the wavelength selection filters 13 and 14, the pixel reflectance can be set to an appropriate condition. When the transmission wavelength is changed, either the illumination angle or the detection angle is changed. That is, when the wavelength λ is changed, it is necessary to change α or β in the above equation (1). By picking up the sample image under the two conditions, the color of the defective pixel can be specified. The processing device 50 acquires a sample image with the imaging conditions as the first condition and the second condition, respectively. Note that an image captured under the first condition is defined as a first sample image. An image captured under the second condition is defined as a second sample image. The first condition and the second condition can be, for example, as follows.

  Under the first condition, the ratio (Rb / Rg) is a value close to 1, and the ratio (Rr / Rg) is a value larger or smaller than 1. That is, under the first condition, the ratio (Rb / Rg) is closer to 1 than the ratio (Rr / Rg). In other words, under the first condition, the difference in pixel reflectance between the R pixel and the G pixel is larger than the difference in pixel reflectance between the B pixel and the G pixel. The difference in pixel reflectance between the two pixels is a value obtained by subtracting the smaller pixel reflectance from the larger pixel reflectance. In the case of the first condition, as in the case of the condition A of FIG. 4, the first sample image contains a large amount of light reflected from the GR pattern.

  Under the second condition, the ratio (Rr / Rg) is a value close to 1, and the ratio (Rb / Rg) is a value larger or smaller than 1. That is, under the first condition, the ratio (Rr / Rg) is closer to 1 than the ratio (Rb / Rg). In other words, the difference in pixel reflectance between the B pixel and the G pixel is larger than the difference in pixel reflectance between the R pixel and the G pixel. In the case of the second condition, similarly to the condition C of FIG. 4, the second sample image includes a large amount of information on the reflected light from the GB pattern.

  In the first sample image, the intensity of the diffracted light from the first pixel row is high, and the intensity of the diffracted light from the second pixel row is low. Therefore, by imaging the sample 20 under the first condition, information on the first pixel row can be selectively received. In the second sample image, the intensity of the diffracted light from the first pixel row is weakened, and the intensity of the diffracted light from the second pixel row is low. Therefore, by imaging the sample 20 under the second condition, the information of the second pixel row can be selectively received. The first sample image contains more reflected light information from the GR repeating pattern, and the second sample image contains more reflected light information from the GB repeating pattern.

  Here, the processing device 50 detects a defect in each of the first sample image and the second sample image. For example, the processing device 50 compares the luminance value of the sample image with a threshold. Then, the processing device 50 specifies a location where the luminance value is less than the threshold value as a defective location. Alternatively, when the luminance value is high at the defective portion, the processing device 50 specifies a position where the luminance value is equal to or larger than the threshold value as the defective portion.

  The processing device 50 specifies the color of the defective pixel based on the detection results under the first condition and the second condition. That is, the processing device 50 specifies the color of the defective pixel by comparing the detection result of the defect based on the first sample image with the detection result of the defect based on the second sample image.

  FIG. 5 is a diagram for explaining a process of specifying the color of a defective pixel based on a result of the defect detection. FIG. 5 is a table showing detection results of three patterns of defects 61.

  If the defect 61 is not detected under the first condition and the defect 61 is detected under the second condition, it is specified that the defect 61 exists in the B pixel. That is, it is determined that the B colored layer has a film formation failure. When the defect is detected under the first condition and the defect 61 is not detected under the second condition, it is specified that the defect 61 exists in the R pixel. That is, it is determined that there is a film formation failure in the R colored layer. If a defect is detected under the first condition and a defect 61 is detected under the second condition, it is specified that the defect 61 is in the G pixel. That is, it is determined that there is a film formation failure in the G colored layer.

  That is, when there is a defect at the same position in the first sample image and the second sample image, the processing device 50 specifies that the defect exists in the G pixel. When there is no defect in the second sample image at the position where the defect is present in the first sample image, the processing device 50 specifies that the defect exists in the R pixel. When there is no defect in the first sample image at the position where the defect exists in the second sample image, the processing device 50 specifies that the defect exists in the B pixel.

  The first sample image contains a lot of reflected light information from the GR pattern, and the second sample image contains a lot of reflected light information from the GB pattern. Therefore, the color of the defective pixel can be specified by comparing the defect detection results of the two sample images. In other words, it is possible to specify which of the coloring layers 21 to 23 has a problem in the film formation step. Therefore, the color of the defective pixel can be easily specified.

  In the present embodiment, the inspection device 100 detects a defect based on diffracted light from the sample 20 having a color filter pattern. Defect inspection can be performed without waiting for completion of all wafer film forming steps. At the time of completion of the color filter pattern forming process, the quality of each colored layer can be determined. The time from the occurrence of a film formation defect to the improvement of the process can be greatly reduced.

  Further, the defect can be detected without using a special jig for inputting / outputting an electric signal such as a probe card in the image sensor. In addition, since the quality of the process can be determined based on the image at a low magnification, the inspection can be performed in a short time. Therefore, the film formation state of various product wafers can be easily confirmed in a short time.

  Although the color filter patterns in the Bayer array are set as the inspection targets, color filter patterns in other arrays may be set as the inspection targets. In addition, the inspection apparatus 100 is not limited to the RGB color filter pattern. For example, the inspection method according to the present embodiment can also inspect an RCCC (Red / Clear / Clear / Clear) color filter pattern. Further, the inspection apparatus 100 can be applied to inspection of a color filter pattern such as RGBW (white), C (cyan), M (magenta) Y (yellow), and CMYK (black).

Embodiment 2.
The inspection apparatus 100 can specify which of the pixels 26G of the first pixel row 28 and the pixels 26G of the second pixel row 29 has a defect by rotating the sample 20. That is, in the second embodiment, the inspection apparatus 100 acquires the sample image by changing the angle of the sample 20 under the first condition and the second condition. An inspection method according to the second embodiment will be described with reference to FIG.

  FIG. 6 is a diagram showing a pixel array when the rotation angles of the sample 20 are 0 ° and 90 °. Here, the stage 30 rotates the sample 20 by 90 ° around the Z axis. Specifically, FIG. 6 illustrates the pixel array of FIG. 3 as a 0 ° pixel array, and a case where the pixel array is rotated 90 ° counterclockwise as a 90 ° pixel array. FIG. 6 shows an array of 4 × 4 pixels. Even when the sample 20 is rotated, the directions of the X axis and the Y axis do not change. Note that the basic configuration and processing of the inspection apparatus 100 are the same as those in the first embodiment, and thus description thereof will be omitted.

  Similar to FIG. 3, four pixels of a G pixel, an R pixel, a B pixel, and a G pixel are indicated by a dotted frame as one repeating unit 27. The four pixels included in the repeating unit 27 composed of the 2 × 2 pixel array are shown as a pixel 26R, a pixel 26G1, a pixel 26G2, and a pixel 26B. That is, two G pixels included in one repetition unit are shown as pixels 26G1 and 26G2. The sample 20 has a color filter pattern in which repeating units are repeatedly arranged in the X direction and the Y direction.

  When the sample 20 is rotated by 90 °, the arrangement of pixels in the repeating unit 27 changes. Specifically, in the order of upper left, upper right, lower left, and lower right, 0 ° indicates the pixel 26G1, 26R, 26B, and 26G2, and 90 ° indicates the pixel 26R, 26G2, and 26G1. , Pixel 26B. In the case of 0 °, the first pixel column 28 and the second pixel column 29 are parallel to the X direction, but in the case of 90 °, the first pixel column 28 and the second pixel column 29 are in the Y direction. And become parallel. In the case of 90 °, one line of pixels parallel to the X direction is referred to as a first pixel row 281 and a second pixel row 291 respectively.

  In the repeating unit 27, the pixel 26R and the pixel 26B are arranged diagonally. In the repeating unit 27, the pixels 26G1 and 26G2 are arranged diagonally. The green pixels 26G1 and 26G2 paired with the pixels 26R and 26B in the pixel column change between 0 ° and 90 °. For example, in the case of 0 °, the pixels 26G1 and the pixels 26R are alternately arranged in the first pixel row 28 along the X direction, and the pixels 26B are arranged in the second pixel row 29 along the X direction. The pixels 26G2 are alternately arranged. On the other hand, in the case of 90 °, in the first pixel row 281 along the X direction, the pixels 26R and the pixels 26G2 are alternately arranged, and in the second pixel row 291 along the X direction, the pixels 26G1 and Pixels 26B are alternately arranged.

  By rotating the sample 20 by 90 °, it is possible to specify which of the pixels 26G1 and 26G2 has a defect. Specifically, under the first condition, the angle of the stage 30 is set to 0 °, and the processing device 50 acquires a sample image. Under the second condition, the processing device 50 acquires a sample image with the stage angle being 90 °. Conditions other than the angle of the stage 30 are the same. Note that both the first condition and the second condition are conditions for increasing the ratio (Rr / Rg) and decreasing the ratio (Rb / Rg).

  In this case, under the first condition, a defect in a pixel column in which the pixels 26G2 and the pixels 26R are alternately arranged is detected. On the other hand, under the second condition, a defect in a pixel column in which the pixels 26R and the pixels 26G1 are alternately arranged is detected.

  Therefore, when a defect is detected under the first condition and no defect is detected under the second condition, it is determined that the pixel 26G2 has a defect. If no defect is detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 26G1 has a defect. When a defect is detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 26R has a defect. As described above, by changing the angle of the sample 20 by 90 °, the processing device 50 can specify which of the green pixel 26G1 and the pixel 26G2 has a defect. The processing device 50 specifies the position of the defective pixel in the repeating unit 27 based on the defect detection results under the first and second conditions.

  In the above example, the pixel array is rotated by rotating the stage 30, but the pixel array is rotated by changing the positions and directions of the detector 11, the light source 10, the filter 13, the filter 14, and the like. May be. The condition may be changed so that the direction of the pixel array relative to the illumination direction and the detection direction is rotated. Then, an image of the sample 20 is acquired under the first condition and the second condition in which the direction of the pixel arrangement with respect to the illumination direction of the illumination light is different.

  In the above example, the ratio (Rr / Rg) is increased and the ratio (Rb / Rg) is decreased together with the first condition and the second condition. It is good also as conditions to make it low and to make ratio (Rb / Rg) high. In this case, it is specified that not the pixel 26R but the pixel 26B has a defect. That is, when a defect is detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 26B has a defect. In this manner, in one repetition unit, the processing device 50 can specify the position of a defective pixel.

  Note that the inspection method according to the second embodiment can be used in combination with the inspection method described in the first embodiment. For example, when the inspection method of the first embodiment determines that the green pixel 26G has a defect, the inspection method of the second embodiment may be performed. In this case, in the repeating unit 27 including four pixels, the processing device 50 can specify a defective pixel. Further, in the present embodiment, since it is only necessary to rotate stage 30 by 90 °, the conditions can be changed easily.

Embodiment 3
In the third embodiment, an inspection is performed on a filter having an RCCC array. In the present embodiment, similarly to the second embodiment, the image of the sample 20 is acquired by rotating the sample 20 by 90 °. FIG. 7 is a diagram schematically illustrating a pixel array of the RCCC array. FIG. 7 shows the pixel arrangement when the rotation angle of the stage 30 is 0 ° and 90 °, similarly to FIG. Note that the basic configuration and processing of the inspection apparatus 100 are the same as those of the first and second embodiments, and thus description thereof will be omitted.

  In the case of the RCCC arrangement, four pixels, that is, the pixel 36R, the pixel 36C1, the pixel 36C2, and the pixel 36C3 form one repeating unit 37. The repeating units 37 each composed of a 2 × 2 pixel array are repeatedly arranged in the X direction and the Y direction. In FIG. 7, since 4 × 4 pixels are shown, four repeating units 37 are shown. Of course, more pixels are arranged on the actual sample 20. The pixel 36R is a pixel having a red coloring layer. The pixel 36C1, the pixel 36C2, and the pixel 36C3 are pixels having a colorless and transparent resin layer.

  In the repeating unit 37, in the order of upper left, upper right, lower left, and lower right, the pixel 36R, the pixel 36C2, the pixel 36C1, and the pixel 36C3 are arranged in the case of 0 °, and the pixels 36C2, 36C3, and 36R in the case of 90 °. , Pixel 36C1. When the sample 20 is rotated by 90 °, the arrangement of the pixels in the repeating unit 27 of the pixel array changes. In the third embodiment, as in the second embodiment, the first condition is set to 0 ° and the second condition is set to 90 ° to acquire a sample image.

  In the repeating unit 37 of the pixel array, the pixel 36R and the pixel 36C3 are arranged diagonally. In the repeating unit 37, the pixels 36C1 and 36C2 are arranged diagonally. Pixels 36R and 36C3 are paired with pixels 36C1 and 36C2 in the pixel column between 0 ° and 90 °. In the case of 0 °, the pixels 36R and the pixels 36C2 are alternately arranged in the first pixel column 38 along the X direction, and the pixels 36C1 and the pixels 36C3 are alternately arranged in the second pixel column 39. Have been. In the case of 90 °, in the first pixel row 381 along the X direction, the pixels 36C2 and 36C3 are alternately arranged, and in the second pixel column 39, the pixels 36R and 36C1 are alternately arranged. Have been.

  By rotating the sample 20 by 90 °, the position of a defective pixel can be specified in the repeating unit 37. That is, the processing device 50 specifies which of the pixels 36R and the pixels 36C1 to C3 has a defect based on the defect detection results under the first and second conditions. Specifically, under the first condition, the angle of the stage 30 is set to 0 °, and the processing device 50 acquires a sample image. Under the second condition, the processing device 50 acquires a sample image with the stage angle being 90 °. Conditions other than the angle of the stage 30 are the same. Here, both the first condition and the second condition are conditions for increasing the ratio (Rr / Rc) and decreasing the ratio (Rc / Rc).

  The diffraction of the RC pattern has a period of two pixels, and the diffraction of the CC pattern has a period of one pixel. Therefore, when the inspection for the RC pattern is performed (hereinafter, referred to as a first inspection) and when the inspection is performed for the CC pattern (hereinafter, referred to as a second inspection), the repetition pitch is different. Change the position of the light source. Specifically, in the case of the first inspection, in the diffraction condition expression shown in Expression (1), the repetition period d is twice the pixel pitch in the first inspection, and the repetition period d is two times in the second inspection. Α and β are determined as the pixel pitch.

  First, the first inspection will be described. Under the first condition of the first inspection, a defect in a pixel column in which the pixels 36R and the pixels 36C1 are alternately arranged is detected. On the other hand, under the second condition of the first inspection, a defect in a pixel column in which the pixels 36C2 and the pixels 36R are alternately arranged is detected. In the first inspection, a portion having a defect is specified as described below. If a defect is detected under the first condition and no defect is detected under the second condition, it is determined that the pixel 36C1 has a defect. If no defect is detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 36C2 has a defect. When a defect is detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 36R has a defect.

  Next, the second inspection will be described. Under the first condition of the second inspection, a defect in a pixel column in which the pixels 36C2 and the pixels 36C3 are alternately arranged is detected. On the other hand, under the second condition of the second inspection, a defect in a pixel column in which the pixels 36C1 and the pixels 36C3 are alternately arranged is detected. In the second inspection, a portion having a defect is specified as described below. If a defect is detected under the first condition and no defect is detected under the second condition, it is determined that the pixel 36C2 has a defect. When a defect is not detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 36C1 has a defect. When a defect is detected under the first condition and a defect is detected under the second condition, it is determined that the pixel 36C3 has a defect.

  As described above, in the first inspection and the second inspection, the sample image is captured under the first and second conditions, respectively. One of the detection angle and the illumination angle is changed between the first inspection and the second inspection. That is, the inspection apparatus 100 acquires a sample image and detects a defect under four conditions. Then, the processing device 50 specifies the position of the defective pixel in the repeating unit 27 by comparing the defect detection results under the four conditions. In the inspection of the present embodiment, only one of the first inspection and the second inspection may be performed.

  Some or all of the processing of the processing device 50 may be executed by a computer program. The above-described program may be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer-readable media include various types of tangible storage media. Examples of the non-transitory computer-readable medium include a magnetic recording medium (for example, a flexible disk, a magnetic tape, and a hard disk drive), a magneto-optical recording medium (for example, a magneto-optical disk), a CD-ROM (Read Only Memory), a CD-R, It includes a CD-R / W, a semiconductor memory (for example, a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, and a RAM (Random Access Memory)). In addition, the program may be supplied to a computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line such as an electric wire and an optical fiber, or a wireless communication line.

  As described above, the embodiments of the present invention have been described. However, the present invention includes appropriate modifications without impairing the objects and advantages thereof, and is not limited by the above embodiments.

REFERENCE SIGNS LIST 100 inspection device 10 light source 11 detector 13 filter 14 filter 20 sample 21 colored layer 22 colored layer 23 colored layer 24 base film 25 color filter pattern 28 first pixel column 29 second pixel column 30 stage 50 processing device

Claims (14)

An inspection apparatus for a sample having a color filter pattern in which pixels of a plurality of colors are arranged in an array,
A light source that generates illumination light for illuminating the sample, and a detector that detects diffracted light from an illumination area illuminated with the illumination light,
A processing device that performs an inspection based on the detection result of the detector,
The processing device includes:
Obtaining an image of the sample under the first condition and the second condition;
Detecting a defect based on the image of the sample under the first condition and the second condition;
An inspection apparatus for identifying a color of a defective pixel based on detection results under the first condition and the second condition. In the first condition, the difference in pixel reflectance between the first color pixel and the second color pixel is determined by the pixel reflectance between the second color pixel and the third color pixel. Is larger than the difference between
In the second condition, the difference in pixel reflectance between the pixel of the second color and the pixel of the third color is caused by the difference between the pixel of the first color and the pixel of the second color. The inspection device according to claim 1, wherein the difference is larger than a difference in pixel reflectance. When a defect is detected under the first condition and no defect is detected under the second condition, the defective pixel is identified as having the first color,
If no defect is detected under the first condition and a defect is detected under the second condition, the defective pixel is identified as having the third color,
3. The inspection apparatus according to claim 2, wherein when a defect is detected under the first condition and a defect is detected under the second condition, the pixel having the defect is specified as the second color. . In the color filter pattern,
In the first pixel column, pixels of the first color and pixels of the second color are alternately arranged,
4. The pixel according to claim 1, wherein the second color pixel and the third color pixel are alternately arranged in a second pixel row adjacent to the first pixel row. 5. Inspection equipment. The wavelength of light detected by the detector is λ, the illumination angle of the illumination light with respect to the sample is α, the detection angle of the detector with respect to the sample is β, the repetition period of the pixel is d, and n is other than 0 Where the first condition and the second condition are
dsinα + dsinβ = nλ
The inspection device according to any one of claims 1 to 4, wherein the inspection device satisfies the following condition. An inspection method by an inspection apparatus that inspects a sample having a color filter pattern in which pixels of a plurality of colors are arranged in an array,
The inspection device,
A light source for generating illumination light for illuminating the sample,
A detector for detecting diffracted light from the illumination area illuminated with the illumination light,
Acquiring images of the sample under the first condition and the second condition,
Detecting a defect based on the image of the sample under the first condition and the second condition;
An inspection method for identifying a color of a defective pixel based on detection results under the first condition and the second condition. In the first condition, the difference in pixel reflectance between the first color pixel and the second color pixel is determined by the pixel reflectance between the second color pixel and the third color pixel. Is larger than the difference between
In the second condition, the difference in pixel reflectance between the pixel of the second color and the pixel of the third color is caused by the difference between the pixel of the first color and the pixel of the second color. The inspection method according to claim 6, wherein the difference is larger than the difference in pixel reflectance. When a defect is detected under the first condition and no defect is detected under the second condition, the defective pixel is identified as having the first color,
If no defect is detected under the first condition and a defect is detected under the second condition, the defective pixel is identified as having the third color,
8. The inspection method according to claim 7, wherein when a defect is detected under the first condition and a defect is detected under the second condition, the defective pixel is identified as the second color. . In the color filter pattern,
In the first pixel column, pixels of the first color and pixels of the second color are alternately arranged,
9. The second pixel column adjacent to the first pixel column, wherein the pixels of the second color and the pixels of the third color are alternately arranged. 10. Inspection method. The wavelength of light detected by the detector is λ, the illumination angle of the illumination light with respect to the sample is α, the detection angle of the detector with respect to the sample is β, the repetition period of the pixel is d, and n is other than 0 Where the first condition and the second condition are
dsinα + dsinβ = nλ
The inspection method according to any one of claims 6 to 9, which satisfies the following condition. A sample inspection apparatus having a color filter pattern in which a plurality of pixels are used as a repeating unit and a pixel array of the repeating unit is repeatedly arranged in first and second directions,
A light source that generates illumination light for illuminating the sample, and a detector that detects diffracted light from an illumination area illuminated with the illumination light,
A processing device that performs an inspection based on the detection result of the detector,
The processing device includes:
A first condition in which a direction of the pixel array with respect to an illumination direction of the illumination light is different, and an image of the sample is acquired under a second condition;
Detecting a defect based on the image of the sample under the first condition and the second condition;
An inspection apparatus for identifying a position of a defective pixel in the repeating unit based on the detection results under the first condition and the second condition.   The inspection apparatus according to claim 11, wherein a direction of the pixel array with respect to an illumination direction of the illumination light is different by 90 ° between the first condition and the second condition. An inspection method using an inspection apparatus for inspecting a sample having a color filter pattern in which a plurality of pixels are used as a repeating unit and a pixel array of the repeating unit is repeatedly arranged in first and second directions,
The inspection device,
A light source for generating illumination light for illuminating the sample,
A detector for detecting diffracted light from the illumination area illuminated with the illumination light,
A first condition in which a direction of the pixel array with respect to an illumination direction of the illumination light is different, and an image of the sample is acquired under a second condition;
Detecting a defect based on the image of the sample under the first condition and the second condition;
An inspection method for identifying a position of a defective pixel in the repeating unit based on detection results under the first condition and the second condition.   14. The inspection method according to claim 13, wherein the direction of the pixel arrangement with respect to the illumination direction of the illumination light differs by 90 degrees between the first condition and the second condition.

Images