Wafer visual inspection device and wafer visual inspection method

Abstract

To provide a wafer appearance inspection device and a wafer appearance inspection method, which can improve the quality of filmed-wafers.SOLUTION: A wager appearance inspection device 10 comprises a control unit 12 configured to generate a plurality of whole images 40 of a wafer surface including partial images 41-45 acquired dividing the wafer surface into a plurality of areas along a circumferential direction of the wafer surface, generate an average image 50 based on the plurality of whole images 40, and detect abnormality on the wafer surface based on the average image 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a wafer appearance inspection apparatus and a wafer appearance inspection method. [Background technology]

[0002] Conventionally, there has been known a method for evaluating the back surface of a wafer, which detects and evaluates polishing unevenness, cloudiness, scratches, and particles (see, for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5433201 Summary of the Invention [Problem to be solved by the invention]

[0004] Defects on the film-formed surface of a bare wafer (film-formed wafer) are more difficult to detect than defects on a bare wafer due to the influence of the film on the wafer. It is required to improve the quality of film-formed wafers by detecting defects on the film-formed surface of the wafer.

[0005] Therefore, an object of the present disclosure is to propose a wafer appearance inspection apparatus and a wafer appearance inspection method that can improve the quality of film-coated wafers. [Means for solving the problem]

[0006] One embodiment of the present disclosure that solves the above problem is as follows. [1] An appearance inspection apparatus comprising: a control unit that generates a plurality of overall images of a wafer surface, including part images obtained by photographing the wafer surface divided into a plurality of regions along a circumferential direction, generates an average image based on the plurality of overall images, and detects abnormalities on the wafer surface based on the average image. [2] The control unit generates each of the plurality of overall images based on the part images captured at different brightnesses. [3] The visual inspection apparatus according to the above-mentioned [1] or [2], wherein the control unit detects abnormalities on the wafer surface based on a differential image obtained by subtracting the average image from the overall image. [4] The control unit extracts pixels in the difference image whose brightness is equal to or greater than a first threshold value as detection candidate pixels, and detects abnormalities on the wafer surface from among the detection candidate pixels. [5] The control unit generates an approximation line based on the positions of the detection candidate pixels, and detects the detection candidate pixels corresponding to a combination of the approximation lines whose difference in slope of the approximation lines is within a second threshold value as abnormal. [6] The visual inspection apparatus described in any one of [1] to [5] above, wherein the control unit detects abnormalities on the wafer surface based on the difference between an average brightness in a central region of the average image that includes the center of the wafer surface and an average brightness in a peripheral region other than the central region. [7] generating a plurality of whole images of the wafer surface including part images obtained by dividing the wafer surface into a plurality of regions along a circumferential direction and capturing the part images; generating an average image based on the plurality of overall images; detecting anomalies on the wafer surface based on the average image; A visual inspection method comprising: [8] The appearance inspection method according to [7] above, further comprising generating each of the plurality of overall images based on the part images captured at different brightnesses. Effect of the Invention

[0007] According to the wafer appearance inspection apparatus and wafer appearance inspection method of the present disclosure, the quality of film-coated wafers can be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing an example of the configuration of a visual inspection system according to an embodiment; [Diagram 2] FIG. 13 is a diagram showing an example of an entire image generated based on part images. [Diagram 3] FIG. 13 is a diagram illustrating an example of an average image. [Figure 4] FIG. 13 is a diagram illustrating an example of a difference image. [Diagram 5] FIG. 13 is a diagram showing an example of linear approximation in a difference image. [Figure 6] FIG. 13 is a diagram showing an example in which approximate straight lines with the same slope are extracted. [Figure 7] FIG. 11 is a diagram illustrating an example of an abnormality detection result. [Figure 8] FIG. 1 is a diagram showing an example of film unevenness within a wafer surface. [Figure 9] 1A to 1C are diagrams showing examples of average images at various portions from the outer periphery to the center of a wafer. [Figure 10] 1 is a graph showing an example of average brightness in an average image of each portion of a wafer. [Figure 11] 4 is a flowchart illustrating an example of a procedure of a visual inspection method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Configuration example of wafer appearance inspection device 10) Hereinafter, a wafer appearance inspection system 100 and an appearance inspection apparatus 10 according to an embodiment of the present disclosure will be described with reference to the drawings. As shown in Fig. 1, the wafer appearance inspection system 100 includes an appearance inspection apparatus 10, an imaging apparatus 20, and a transport apparatus 30. The imaging apparatus 20 or the transport apparatus 30 may be included in the appearance inspection apparatus 10.

[0010] The appearance inspection system 100 may inspect the appearance of a wafer surface including the front surface or the back surface of a wafer. The wafer includes a silicon wafer and the like. The appearance inspection system 100 inspects the appearance of a wafer surface on which a thin film such as a CVD (Chemical Vapor Deposition) film is formed on a polished wafer or an epitaxial wafer. The type of the thin film may be, for example, an oxide film such as a silicon oxide film or a nitride film such as a silicon nitride film. The type of the thin film is not limited to an oxide film or a nitride film, and may be various other materials. The thickness of the thin film may be, for example, about 250 nm to 450 nm. The thickness of the thin film may be 250 nm or less, or 450 nm or more. Hereinafter, the appearance inspection system 100 for inspecting the appearance of the back surface of a wafer on which a thin film is formed will be described.

[0011] In the visual inspection system 100, a wafer is transported by a transport device 30 to an imaging device 20, which then captures an image of the front or back surface of the wafer. The imaging device 20 outputs the captured image of the wafer to the visual inspection device 10. The visual inspection device 10 inspects the appearance of the front or back surface of the wafer based on the image of the wafer.

[0012] The appearance inspection apparatus 10 includes a control unit 12, an input unit 14, and an output unit 16. The control unit 12 controls each component of the appearance inspection apparatus 10. The control unit 12 acquires information or data such as an image of a wafer from the input unit 14. The control unit 12 outputs a processing result based on the information or data via the output unit 16. The control unit 12 may include at least one processor. The processor may execute a program that realizes various functions of the control unit 12. The processor may be realized as a single integrated circuit. The integrated circuit is also referred to as an IC (Integrated Circuit). The processor may be realized as a plurality of integrated circuits and discrete circuits that are communicatively connected. The processor may be realized based on various other known technologies.

[0013] The control unit 12 may further include a memory unit. The memory unit stores, for example, an image of a wafer or a visual inspection result based on an image of a wafer. The memory unit may include an electromagnetic storage medium such as a magnetic disk, or may include a memory such as a semiconductor memory or a magnetic memory. The memory unit may include a non-transitory computer-readable medium. The memory unit stores various information and programs executed by the control unit 12. The memory unit may function as a work memory for the control unit 12. At least a part of the memory unit may be configured as a separate entity from the control unit 12.

[0014] The input unit 14 acquires an image of the wafer from the imaging device 20 and outputs the image to the control unit 12. The output unit 16 outputs information or data relating to the processing results in the control unit 12.

[0015] The input unit 14 or the output unit 16 may include a communication device that transmits and receives information or data to and from other devices such as the imaging device 20 or the transport device 30. The communication device may be communicatively connected to the other devices via a network. The communication device may be communicatively connected to the other devices by wire or wirelessly. The communication device may include a communication module that connects to the network or the other devices. The communication module may include a communication interface such as a LAN (Local Area Network). The communication module may include a communication interface for non-contact communication such as infrared communication or NFC (Near Field communication). The communication module may realize communication by various communication methods such as 4G or 5G. The communication method implemented by the communication device is not limited to the above examples and may include various other methods.

[0016] The input unit 14 may be configured to include an input device that accepts input of information or data from a user. The input device may be configured to include, for example, a touch panel or a touch sensor, or a pointing device such as a mouse. The input device may be configured to include physical keys. The input device may be configured to include a voice input device such as a microphone.

[0017] The output unit 16 may include a display device that outputs visual information such as an image, text, or a graphic. The display device may include, for example, an LCD (Liquid Crystal Display), an organic EL (Electro-Luminescence) display, an inorganic EL display, or a PDP (Plasma Display Panel). The display device is not limited to these displays and may include displays of various other types. The display device may include a light-emitting device such as an LED (Light Emitting Diode) or an LD (Laser Diode). The display device may include various other devices. The output unit 16 may include an audio output device such as a speaker.

[0018] The imaging device 20 includes, for example, a camera or an imaging element. The imaging device 20 captures an image of the wafer surface including the front or back surface of the wafer. The imaging device 20 may include a light source that emits illumination light to illuminate the wafer surface. The imaging device 20 may include, for example, an LED or a halogen lamp as the light source. In this embodiment, the light source is an LED. The light source is configured to be able to change the illuminance of the illumination light in at least two stages. The light source may be configured to be able to change the input power. The light source may be configured to be able to change the wavelength or spectrum of the illumination light. The light source may include a plurality of light-emitting devices.

[0019] The imaging device 20 photographs the wafer surface divided into a plurality of regions along the radial direction and circumferential direction of the wafer. The imaging device 20 is configured as a plurality of cameras or imaging elements arranged in the radial direction of the wafer. The imaging device 20 may include a stage on which the wafer is placed. The imaging device 20 may rotate the placed wafer by rotating the stage. The imaging device 20 may photograph the wafer surface divided into a plurality of regions along the circumferential direction of the wafer by photographing the rotating wafer from a fixed camera or imaging element. The imaging device 20 may photograph the wafer surface divided into a plurality of regions along the circumferential direction of the wafer by moving the camera or imaging element along the circumferential direction of the wafer relative to the wafer placed on the stage. The regions may overlap in part along the radial direction or circumferential direction. The images of the regions are also called part images. The imaging device 20 outputs the part images to the appearance inspection device 10. Furthermore, the imaging device 20 outputs to the appearance inspection device 10 information specifying the relationship between the part image and the position within the wafer surface where the part image was captured in association with the part image.

[0020] The transport device 30 transports the wafer to the imaging device 20. The transport device 30 may transport the wafer onto a stage of the imaging device 20. The transport device 30 may take out the wafer from the imaging device 20 after the imaging device 20 has completed photographing the wafer. The transport device 30 may include an arm that is moved by a driving device such as a motor. The transport device 30 may include a hand or an adsorption unit that holds the wafer.

[0021] (Operation example of visual inspection system 100) In the visual inspection system 100, the imaging device 20 captures part images of the wafer surface. In this embodiment, the imaging device 20 changes the illuminance of the illumination light to three levels and captures part images at each illuminance. The number of illuminance levels may be two or four or more. That is, the imaging device 20 changes the illuminance of the illumination light to multiple levels and captures part images at each illuminance. The imaging device 20 generates part images by capturing images of the wafer surface illuminated with illumination light of each illuminance by varying the illuminance of the illumination light. When the imaging device 20 changes the illuminance of the illumination light to three levels, it generates three types of part images. By changing the illuminance of the illumination light, the luminance of the part images corresponding to each illuminance differs from one another.

[0022] The illuminance of the illumination light may be set based on the type or thickness of the thin film formed on the wafer surface. The illuminance of the illumination light may be set, for example, between 100,000 lux and 500,000 lux. The illuminance of the illumination light may be set to less than 100,000 lux or to 500,000 lux or more. The illuminance of the illumination light may be set as the power input to the light source. The power input to the light source may be set, for example, between 100 watts (W) and 500 watts (W). The power input to the light source may be set to less than 100 watts or to 500 watts or more.

[0023] The control unit 12 of the appearance inspection device 10 acquires from the input unit 14 part images of the wafer surface illuminated by the imaging device 20 with illumination light of each illuminance. Based on information specifying the positions on the wafer surface where the part images were captured, the control unit 12 arranges the acquired part images at each capture position to generate an overall image 40 that appears to have captured the entire wafer surface, as shown in FIG. 2, for example. The control unit 12 generates an overall image 40 for each illuminance. When the part images are captured at three types of illuminance, the control unit 12 generates one overall image 40 corresponding to each illuminance. That is, the control unit 12 generates three overall images 40.

[0024] The control unit 12 may acquire part images from the input unit 14, the part images being images of the wafer surface illuminated with illumination light of different wavelengths or spectra by the imaging device 20. The control unit 12 may generate an overall image 40 for each wavelength or spectrum.

[0025] In Fig. 2, the part images include a first part image 41, a second part image 42, a third part image 43, a fourth part image 44, and a fifth part image 45. The first part image 41 corresponds to an image obtained by dividing an area located on the outermost periphery of the wafer surface into a plurality of areas along the circumferential direction and photographing the area. The second part image 42, the third part image 43, and the fourth part image 44 correspond to images obtained by dividing an area located on the second, third, and fourth periphery inside the outermost periphery of the wafer surface into a plurality of areas along the circumferential direction and photographing the area. The fifth part image 45 corresponds to an image obtained by photographing an area located in the center of the wafer surface.

[0026] The control unit 12 may remove images of particles included in each part image when generating the whole image 40. Particles are a general term for foreign matter attached to the wafer surface.

[0027] When there is an area where the wafer surface is not photographed between each of the part images constituting the entire image 40, the control unit 12 may interpolate the image between each of the part images. The control unit 12 may interpolate the image using an algorithm for interpolating a missing part of the image. The algorithm for interpolating a missing part of the image may include various algorithms such as an algorithm using a neural network.

[0028] The control unit 12 generates an average image 50 illustrated in FIG. 3 based on the multiple overall images 40. Specifically, the control unit 12 performs a differential process on each of the multiple overall images 40 to generate multiple differential images. The control unit 12 may perform the differential process using a filter such as a first-order differential filter. The control unit 12 generates the average image 50 by superimposing the multiple differential images. That is, the control unit 12 can generate the average image 50 by performing a differential process on the overall images 40 of different luminances and superimposing them. By superimposing the overall images 40 of different luminances, the object extracted by the appearance inspection system 100 can be emphasized. In addition, by performing the differential process, the object extracted by the appearance inspection system 100 can be emphasized. Conversely, the imaging device 20 may set the illuminance of the illumination light so that the object extracted by the appearance inspection system 100 is emphasized. The control unit 12 may select an algorithm for the differential process so that the object extracted by the appearance inspection system 100 is emphasized.

[0029] The control unit 12 may perform a differentiation process or a superposition process on the overall image 40 generated for each wavelength or spectrum to generate an average image 50.

[0030] The control unit 12 can detect a streak-like abnormality based on the average image 50. The streak-like abnormality is also referred to as a first abnormality. The control unit 12 can detect a film unevenness abnormality on the wafer surface based on the average image 50. The film unevenness abnormality is also referred to as a second abnormality. The control unit 12 can operate in a mode for detecting a streak-like abnormality (first abnormality) and a mode for detecting a film unevenness abnormality (second abnormality). The mode for detecting a streak-like abnormality (first abnormality) is also referred to as a first mode. The mode for detecting a film unevenness abnormality (second abnormality) is also referred to as a second mode. The operation of each of the first and second modes will be described below.

[0031] <Example of operation in the first mode> When operating in the first mode, the control unit 12 generates a difference image 52 illustrated in FIG. 4 as an image obtained by taking the difference between the entire image 40 and the average image 50. The control unit 12 may take the difference between each of a plurality of entire images 40 having different luminance and the average image 50. The control unit 12 may take the difference between the entire image 40 and the average image 50 at at least one luminance. The difference image 52 illustrated in FIG. 4 is an image obtained by further binarizing the difference between the entire image 40 and the average image 50. In the difference image 52, pixels having a high luminance (represented by white) are also referred to as detection candidate pixels 54. The control unit 12 may extract pixels that have become white by the binarization process as the detection candidate pixels 54. In the difference image 52, the control unit 12 may extract pixels having a luminance equal to or greater than a predetermined value as the detection candidate pixels 54. The predetermined value that is the reference for extracting the detection candidate pixels 54 is also referred to as a first threshold value. The control unit 12 may binarize the difference image 52 based on the first threshold value. For example, the control unit 12 may perform binarization such that pixels with a luminance equal to or greater than a first threshold value are converted to white, and pixels with a luminance less than the first threshold value are converted to black.

[0032] The control unit 12 extracts detection candidate pixels 54 from the difference image 52, as exemplified in Fig. 5. In Fig. 5, the set of detection candidate pixels 54 is expressed with emphasized contours. The control unit 12 approximates a figure represented by the set of detection candidate pixels 54 with straight lines. For example, the control unit 12 detects the longitudinal direction of the detection candidate pixels 54, and extracts a straight line along the longitudinal direction as an approximated straight line 56. This process is also called straight line approximation process.

[0033] As illustrated in Fig. 6, the control unit 12 extracts a combination of approximate straight lines 56 that have the same slope or a slope difference equal to or smaller than a predetermined value from among the approximate straight lines 56. This process is also called an identical slope extraction process. The predetermined value that is the reference for extracting a combination of approximate straight lines 56 is also called a second threshold value. The extracted combination of approximate straight lines 56 is represented by being surrounded by a dashed rectangle, and is also called an extracted straight line 58.

[0034] The control unit 12 may regard the extracted straight line 58 as a streak-like abnormality. When the control unit 12 detects the extracted straight line 58, the control unit 12 may output information indicating that a streak-like abnormality has been detected to the output unit 16, and notify the user. Furthermore, the control unit 12 may detect the detection candidate pixel 54 corresponding to the extracted straight line 58 as an abnormality.

[0035] As exemplified in Fig. 7, the control unit 12 may generate a resultant image 60 by superimposing the detection candidate pixels 54 (see Fig. 4 or Fig. 5) highlighted by the difference image 52 and an approximation line 56 (see Fig. 5) generated based on the detection candidate pixels 54 on the average image 50. The control unit 12 may highlight and display the detection candidate pixels 54 corresponding to the extraction line 58 extracted in Fig. 6 as detection pixels 62 in the resultant image 60. The control unit 12 may also highlight and display the extraction line 58 as a detection line 64 in the resultant image 60. The control unit 12 may notify the user of the appearance inspection result by causing the output unit 16 to display the resultant image 60.

[0036] The control unit 12 may cause the output unit 16 to display the entire image 40 or the average image 50 .

[0037] <Example of operation in the second mode> When the control unit 12 operates in the second mode, it can detect the film unevenness abnormality (second abnormality) based on the luminance of the average image 50.

[0038] An example of film unevenness within a wafer surface is shown in Figure 8. An average image 50 of a wafer surface having film unevenness is displayed as a film unevenness image 70. In the film unevenness image 70, a central region 72 close to the center of the wafer surface has low brightness. In other words, the central region 72 is displayed in a color close to black. Moreover, a peripheral region 74 close to the edge of the wafer surface has high brightness. In other words, the peripheral region 74 is displayed in a color close to white.

[0039] The control unit 12 generates an image by averaging the luminance of pixels at positions in the average image 50 corresponding to each of the first part image 41 to the fifth part image 45 in Fig. 2. For example, as shown in Fig. 9, the images by averaging the luminance of pixels at positions corresponding to each of the first part image 41 to the fifth part image 45 are represented as a first luminance average image 81 to a fifth luminance average image 85. In this embodiment, the control unit 12 classifies the images for which the luminance average image is calculated into five groups, but may also classify the images into four or fewer groups, or into six or more groups.

[0040] The control unit 12 calculates the average brightness of each of the first brightness average image 81 to the fifth brightness average image 85. The control unit 12 normalizes the average brightness. In this embodiment, the control unit 12 assumes that the average brightness of the second brightness average image 82 is unlikely to vary between wafers, and normalizes the average brightness of the other images by setting the average brightness of the second brightness average image 82 to 100%. The image serving as the standard for normalization is not limited to the second brightness average image 82, and may be other images such as the first brightness average image 81, the third brightness average image 83, the fourth brightness average image 84, or the fifth brightness average image 85. The normalized average brightness is also referred to as the normalized average brightness. When the normalized average brightness is below the judgment threshold, the control unit 12 judges that a film unevenness abnormality occurs on the wafer.

[0041] An example of the calculation results of the normalized average brightness is shown as a graph in FIG. 10. The horizontal axis of the graph in FIG. 10 represents the position on the wafer. "Outermost circumference" represents the position corresponding to first part image 41. "Second lap" represents the position corresponding to second part image 42. "Third lap" represents the position corresponding to third part image 43. "Fourth lap" represents the position corresponding to fourth part image 44. "Center" represents the position corresponding to fifth part image 45. The vertical axis represents the normalized average brightness calculated based on the brightness average image at each position.

[0042] Here, the judgment threshold is represented by X%. In the graph in which the normalized average brightness at each position is represented by a circle (○), the normalized average brightness is X% or more at all positions. In this case, the control unit 12 judges that no film unevenness abnormality has occurred in the wafer corresponding to the graph in which the normalized average brightness is represented by a circle. On the other hand, in the graph in which the normalized average brightness at each position is represented by a triangle (△), the normalized average brightness is less than X% at some positions. In this case, the control unit 12 judges that a film unevenness abnormality has occurred in the wafer corresponding to the graph in which the normalized average brightness is represented by a triangle. That is, the control unit 12 can compare the normalized average brightness with the judgment threshold and judge whether a film unevenness abnormality has occurred. The judgment threshold may be set to various values ​​such as 80% or 90%.

[0043] (Example of visual inspection procedure) The control unit 12 of the appearance inspection apparatus 10 may execute an appearance inspection method including the procedure of the flowchart exemplified in Fig. 11. The appearance inspection method may be realized as an appearance inspection program executed by a processor constituting the control unit 12. The appearance inspection program may be stored in a non-transitory computer-readable medium.

[0044] The control unit 12 acquires a part image (step S1). The control unit 12 generates an overall image 40 based on the part image (step S2). The control unit 12 generates an average image 50 based on the overall image 40 (step S3). The control unit 12 determines whether to perform detection in the first mode (step S4). If the control unit 12 detects in the first mode (step S4: YES), the control unit 12 proceeds to the procedure of step S5. If the control unit 12 does not detect in the first mode (step S4: NO), the control unit 12 proceeds to the procedure of step S7.

[0045] When detecting in the first mode, the control unit 12 calculates the difference between the entire image 40 and the average image 50 to generate a difference image 52 (step S5). The control unit 12 detects a first abnormality (a streak-like abnormality) based on the difference image 52 (step S6). Specifically, the control unit 12 may execute a binarization process, or a straight-line approximation process and a uniform gradient extraction process in the procedure of step S6. After executing the procedure of step S6, the control unit 12 proceeds to the procedure of step S9.

[0046] When detecting in the second mode, the control unit 12 calculates the average brightness at each position on the wafer surface (step S7). The control unit 12 detects the second abnormality (film unevenness abnormality) based on the calculated average brightness (step S8). After executing the procedure of step S8, the control unit 12 proceeds to the procedure of step S9.

[0047] The control unit 12 outputs the detection result in the first mode or the second mode (step S9). After executing the procedure of step S9, the control unit 12 ends the execution of the procedure of the flowchart in FIG. 11. The control unit 12 may execute both the detection in the first mode and the detection in the second mode. The control unit 12 may execute the detection in the first mode first, may execute the detection in the second mode first, or may execute the detection in the first mode and the detection in the second mode in parallel.

[0048] As described above, the appearance inspection system 100, the appearance inspection device 10, and the appearance inspection method according to the present embodiment can generate an image that emphasizes an abnormality on the wafer surface of a film-coated wafer. As a result, the quality of the film-coated wafer can be improved.

[0049] Although the embodiments according to the present disclosure have been described based on the drawings and examples, it should be noted that a person skilled in the art can make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications or alterations are included in the scope of the present disclosure. For example, the functions included in each component or each step can be rearranged so as not to be logically inconsistent, and multiple components or steps can be combined into one or divided. Although the embodiments according to the present disclosure have been described mainly with respect to the device, the embodiments according to the present disclosure can also be realized as a method including steps executed by each component of the device. The embodiments according to the present disclosure can also be realized as a method, a program, or a storage medium on which a program is recorded, executed by a processor included in the device. It should be understood that these are also included in the scope of the present disclosure.

[0050] The graphs included in this disclosure are schematic and do not necessarily correspond to the actual scale. [Industrial Applicability]

[0051] According to the embodiments of the present disclosure, the quality of the film-coated wafer can be improved. [Explanation of symbols]

[0052] 100 Visual Inspection System 10 Appearance inspection device (12: control unit, 14: input unit, 16: output unit) 20 Imaging device 30 Transport device 40 Overall image (41~45: 1st to 5th part images) 50 Average Images 52 Difference image (54: detected candidate pixel, 56: approximate line, 58: extracted line) 60 Result image (62: detected pixel, 64: detected line) 70 Film irregularity images (72: central area, 74: peripheral area) 81~85 1st to 5th average brightness images

Claims

1. a control unit that generates a plurality of whole images of the wafer surface including part images obtained by dividing the wafer surface into a plurality of regions along a circumferential direction, generates an average image based on the plurality of whole images, and detects an abnormality on the wafer surface based on the average image, The control unit generates each of the plurality of overall images based on the part images captured under different shooting conditions.

2. The visual inspection apparatus according to claim 1 , wherein the control unit generates each of the plurality of whole images based on the part images captured at different luminance levels.

3. 3. The visual inspection apparatus according to claim 1, wherein the control unit detects an abnormality on the wafer surface based on a differential image obtained by calculating a difference between the average image and at least one of the plurality of overall images.

4. 4. The visual inspection apparatus according to claim 3, wherein the control unit extracts pixels in the difference image whose luminance is equal to or greater than a first threshold value as detection candidate pixels, and detects an abnormality on the wafer surface from among the detection candidate pixels.

5. 5. The visual inspection device according to claim 4, wherein the control unit generates approximate lines based on positions of the detection candidate pixels, and detects, as an anomaly, the detection candidate pixels corresponding to a combination of the approximate lines whose difference in slope of the approximate lines is within a second threshold value.

6. 6. The visual inspection apparatus according to claim 1, wherein the control unit detects an abnormality on the wafer surface based on a difference between an average brightness in a central region of the average image including a center of the wafer surface and an average brightness in a peripheral region other than the central region.

7. generating a plurality of whole images of the wafer surface including part images obtained by dividing the wafer surface into a plurality of regions along a circumferential direction and capturing the part images; generating an average image based on the plurality of overall images; detecting anomalies on the wafer surface based on the average image; Including, The appearance inspection method, in which, in generating the plurality of overall images, each of the plurality of overall images is generated based on the part images photographed under different photographing conditions.

8. The appearance inspection method according to claim 7 , further comprising: generating each of the plurality of whole images based on the part images captured at different luminance levels.

Images