WO2022255043A1 - ウェーハの外観検査装置及びウェーハの外観検査方法 - Google Patents
ウェーハの外観検査装置及びウェーハの外観検査方法 Download PDFInfo
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Definitions
- the present disclosure relates to a wafer visual inspection apparatus and a wafer visual inspection method.
- Defects on the film-forming surface of a wafer (film-coated wafer) on which a film is formed on a bare wafer are more difficult to detect than defects on bare wafers due to the influence of the film attached to the wafer. It is desired to improve the quality of film-coated wafers by detecting defects on the film-coated surface of the wafer.
- an object of the present disclosure is to propose a wafer visual inspection apparatus and a wafer visual inspection method that can improve the quality of film-coated wafers.
- An embodiment of the present disclosure for solving the above problems is as follows. [1] generating a plurality of whole images of the wafer surface including part images photographed by dividing the wafer surface into a plurality of regions along the circumferential direction; generating an average image based on the plurality of whole images; A visual inspection apparatus comprising a control unit that detects an abnormality of the wafer surface based on. [2] The appearance inspection apparatus according to [1] above, wherein the control unit generates each of the plurality of overall images based on the parts images captured with different luminances.
- the visual inspection apparatus detects an abnormality of the wafer surface based on a difference between an average luminance in a central region including the center of the wafer surface and an average luminance in a peripheral region other than the central region in the average image.
- the visual inspection apparatus according to any one of [1] to [5] above.
- [7] Generating a plurality of whole images of the wafer surface including part images photographed by dividing the wafer surface into a plurality of regions along the circumferential direction; generating an average image based on the plurality of global images; and detecting an abnormality of the wafer surface based on the average image.
- the appearance inspection method according to [7] above, further comprising generating each of the plurality of overall images based on the parts images captured at different luminances.
- the quality of the film-coated wafer can be improved.
- FIG. 1 is a block diagram showing a configuration example of an appearance inspection system according to an embodiment;
- FIG. It is a figure which shows an example of the whole image produced
- FIG. 4 is a graph showing an example of average brightness in an average image of each portion of a wafer; 4 is a flow chart showing an example procedure of an appearance inspection method according to one embodiment.
- a wafer visual inspection system 100 includes a visual inspection device 10 , an imaging device 20 , and a transport device 30 .
- the imaging device 20 or the conveying device 30 may be included in the visual inspection device 10 .
- the appearance inspection system 100 may inspect the appearance of the wafer surface including the front surface or the back surface of the wafer.
- Wafers include silicon wafers and the like.
- the appearance inspection system 100 inspects the appearance of the surface of a wafer formed by forming a thin film such as a CVD (Chemical Vapor Deposition) film on a polished wafer or an epitaxial wafer.
- the type of 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 thin film is not limited to oxide or nitride films, but may be other various materials.
- the thickness of the thin film may be, for example, approximately 250 nm to 450 nm.
- the thickness of the thin film may be 250 nm or less, or may be 450 nm or more.
- the wafer is transported to the imaging device 20 by the transport device 30, and the front surface or the back surface of the wafer is photographed by the imaging device 20.
- the imaging device 20 outputs the photographed image of the wafer to the visual inspection device 10 .
- the appearance inspection apparatus 10 inspects the appearance of the front surface or the back surface of the wafer based on the image of the wafer.
- the visual inspection apparatus 10 includes a control section 12, an input section 14, and an output section 16.
- the control unit 12 controls each component of the visual inspection apparatus 10 .
- the control unit 12 acquires information or data such as an image of the wafer from the input unit 14 .
- the control unit 12 outputs a processing result based on the information or data through the output unit 16 .
- Control unit 12 may include at least one processor.
- the processor can execute programs that implement various functions of the controller 12 .
- a processor may be implemented as a single integrated circuit. An integrated circuit is also called an IC (Integrated Circuit).
- a processor may be implemented as a plurality of communicatively coupled integrated and discrete circuits. Processors may be implemented based on various other known technologies.
- the control unit 12 may further include a storage unit.
- the storage unit stores, for example, an image of the wafer or a visual inspection result based on the image of the wafer.
- the storage 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 storage unit may include non-transitory computer-readable media.
- the storage unit stores various information, programs executed by the control unit 12, and the like.
- the storage section may function as a work memory for the control section 12 . At least part of the storage unit may be configured separately from the control unit 12 .
- the input unit 14 acquires the wafer image from the imaging device 20 and outputs it to the control unit 12 .
- the output unit 16 outputs information or data regarding the processing result in the control unit 12 .
- the input unit 14 or the output unit 16 may include a communication device that transmits and receives information or data to and from another device such as the imaging device 20 or the transport device 30.
- a communication device may be communicatively connected to other devices via a network.
- a communication device may be communicatively connected to another device by wire or wirelessly.
- a communication device may include a communication module that connects to a network or other device.
- the communication module may include a communication interface such as LAN (Local Area Network).
- the communication module may comprise a communication interface for contactless communication such as infrared communication or NFC (Near Field communication) communication.
- the communication module may realize communication by various communication schemes such as 4G or 5G.
- the communication method executed by the communication device is not limited to the examples described above, and may include other various methods.
- the input unit 14 may include an input device that receives input of information, data, etc. from the user.
- the input device may include, for example, a touch panel or touch sensor, or a pointing device such as a mouse.
- the input device may be configured including physical keys.
- the input device may include an audio input device such as a microphone.
- the output unit 16 may include, for example, a display device that outputs visual information such as images or characters or graphics.
- the display device may include, for example, an LCD (Liquid Crystal Display), an organic EL (Electro-Luminescence) display or an inorganic EL display, or a PDP (Plasma Display Panel).
- the display device is not limited to these displays, and may be configured to include other various types of displays.
- 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 be configured including other various devices.
- the output unit 16 may include an audio output device such as a speaker.
- the imaging device 20 includes, for example, a camera or an imaging device.
- the imaging device 20 photographs the wafer surface including the front surface or the rear surface of the wafer.
- the imaging device 20 may include a light source that emits illumination light that illuminates the wafer surface.
- the imaging device 20 may include, for example, an LED or a halogen lamp as a light source. In this embodiment, it is assumed that the light source is an LED.
- the light source is configured such that the illuminance of the illumination light can be changed in at least two stages.
- the light source may be configured such that the input power can be changed.
- the light source may be configured to change the wavelength or spectrum of the illuminating light.
- the light source may comprise multiple light emitting devices.
- the imaging device 20 divides the wafer surface into a plurality of regions along each of the radial direction and the circumferential direction of the wafer and photographs them. Assume that the imaging device 20 is configured as a plurality of cameras, imaging elements, or the like 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 divide the wafer surface 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 divides the wafer surface into a plurality of regions along the circumferential direction of the wafer by moving a camera or an imaging device along the circumferential direction of the wafer with respect to the wafer placed on the stage. You can take pictures. Each region may partially overlap along a radial or circumferential direction. An image obtained by photographing each region is also referred to as a parts image.
- the imaging device 20 outputs the parts image to the visual inspection device 10 .
- the imaging device 20 outputs to the visual inspection apparatus 10 information specifying the relationship between the part image and the position within the wafer surface where the part image is captured, in association with the part image.
- the transport device 30 transports the wafer to the imaging device 20 .
- the transport device 30 may transport the wafer onto the stage of the imaging device 20 .
- the transport device 30 may carry out from the imaging device 20 the wafer that has been photographed by the imaging device 20 .
- Transport apparatus 30 may comprise an arm that is moved by a drive device such as a motor.
- the transfer device 30 may include a hand, a suction unit, or the like that holds the wafer.
- the imaging device 20 captures a part image of the wafer surface.
- the imaging device 20 changes the illuminance of the illumination light in three stages, and captures the parts image at each illuminance.
- the number of levels of illuminance may be two or four or more. That is, the imaging device 20 changes the illuminance of the illumination light in a plurality of stages, and captures the parts image at each illuminance.
- the imaging device 20 generates a part image by photographing the wafer surface illuminated with the illumination light of each illumination intensity by varying the illumination intensity of the illumination light.
- the imaging device 20 generates three types of parts images when changing the illuminance of the illumination light in three stages. By changing the illuminance of the illumination light, the brightness of the part images corresponding to each illuminance differs from each other.
- the illuminance of the illumination light can be set based on the type or thickness of the thin film deposited 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 may be set to 500,000 lux or more.
- the illuminance of 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 may be set to 500 Watts or more.
- the control unit 12 of the visual inspection apparatus 10 acquires, from the input unit 14, a part image obtained by photographing the wafer surface illuminated by the illumination light of each illuminance by the imaging device 20.
- the control unit 12 arranges the acquired part images at each photographing position based on the information specifying the positions within the wafer surface where the part images were photographed, so that the entire wafer surface is displayed as shown in FIG. 2, for example.
- the control unit 12 generates an overall image 40 for each illuminance.
- the control unit 12 When the parts image is captured with three types of illuminance, the control unit 12 generates one whole image 40 corresponding to each illuminance. That is, the control unit 12 generates three whole images 40 .
- the control unit 12 may acquire, from the input unit 14, a part image of the wafer surface illuminated by the imaging device 20 with illumination light of different wavelengths or spectra. Controller 12 may generate global image 40 for each wavelength or spectrum.
- the parts images include a first parts image 41, a second parts image 42, a third parts image 43, a fourth parts image 44, and a fifth parts image 45.
- the first part image 41 corresponds to an image obtained by dividing the outermost region of the wafer surface into a plurality of regions in the circumferential direction.
- the second part image 42, the third part image 43, and the fourth part image 44 are arranged along the circumferential direction in areas located on the second, third, and fourth turns inside the outermost periphery of the wafer surface. It corresponds to an image captured by dividing it into multiple areas.
- the fifth part image 45 corresponds to an image of an area located in the center of the wafer surface.
- control unit 12 may remove images of particles included in each part image. Particles are a general term for foreign matter adhering to the wafer surface.
- control unit 12 may interpolate the images between the parts images.
- the control unit 12 may interpolate the image using an algorithm for interpolating missing portions of the image.
- Algorithms for interpolating missing portions of an image may include various algorithms such as algorithms using neural networks.
- the control unit 12 generates an average image 50 illustrated in FIG. 3 based on the multiple whole images 40 . Specifically, the control unit 12 performs differentiation processing on each of the plurality of whole images 40 to generate a plurality of differential images.
- the control unit 12 may perform differentiation processing using a filter such as a first-order differentiation filter, for example.
- the control unit 12 generates an average image 50 by superimposing a plurality of differential images. In other words, the control unit 12 can generate the average image 50 by performing differential processing on the entire images 40 with different luminances and superimposing them.
- Objects extracted by visual inspection system 100 may be emphasized by overlaying different brightness global images 40 . Also, the object to be extracted by the appearance inspection system 100 can be emphasized by performing differentiation processing.
- the imaging device 20 may set the illuminance of the illumination light so that the object to be extracted by the visual inspection system 100 is emphasized.
- the control unit 12 may select a differentiation processing algorithm such that the object to be extracted by the visual inspection system 100 is emphasized.
- the control unit 12 may generate the average image 50 by performing differentiation processing or superimposition processing on the entire image 40 generated for each wavelength or spectrum.
- the control unit 12 can detect streak-like abnormalities based on the average image 50 .
- a streak anomaly is also referred to as a primary anomaly. Further, based on the average image 50, the control unit 12 can detect film unevenness on the wafer surface. The uneven film anomaly is also referred to as a secondary anomaly. It is assumed that 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 (second abnormality).
- a mode for detecting a streak-like abnormality (first abnormality) is also referred to as a first mode.
- a mode for detecting a film unevenness abnormality (second abnormality) is also referred to as a second mode. The operation of each of the first mode and the second mode will be described below.
- the control unit 12 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 whole image 40 and the average image 50 .
- the control unit 12 may obtain the difference between each of the plurality of whole images 40 having different luminances and the average image 50 .
- the control unit 12 may take a difference between the overall image 40 and the average image 50 in at least one brightness.
- a 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 .
- pixels with high brightness represented in white
- the control unit 12 may extract pixels that have become white by the binarization process as detection candidate pixels 54 .
- the control unit 12 may extract, as detection candidate pixels 54, pixels whose brightness is equal to or higher than a predetermined value in the difference image 52.
- the predetermined value that serves as a reference for extracting the detection candidate pixel 54 is also called a first threshold.
- the control unit 12 may binarize the difference image 52 based on the first threshold. For example, the control unit 12 may perform binarization in which pixels with luminance equal to or higher than the first threshold are white and pixels with luminance lower than the first threshold are black.
- the control unit 12 extracts detection candidate pixels 54 in the difference image 52, as illustrated in FIG. In FIG. 5, a set of detection candidate pixels 54 is expressed with an emphasized outline.
- the control unit 12 approximates a figure represented by a set of detection candidate pixels 54 with a straight line. For example, the control unit 12 detects the longitudinal direction of the detection candidate pixel 54 and extracts a straight line along the longitudinal direction as the approximate straight line 56 . This process is also called a straight line approximation process.
- the control unit 12 extracts a combination of approximate straight lines 56 having the same slope or a slope difference equal to or smaller than a predetermined value.
- This processing is also referred to as same-slope extraction processing.
- the predetermined value that serves as a reference for extracting a combination of approximate straight lines 56 is also referred to as a second threshold.
- a combination of the extracted approximate straight lines 56 is surrounded by a dashed rectangle and is also referred to as an extracted straight line 58 .
- the control unit 12 may regard the extracted straight line 58 as a streak-shaped abnormality.
- the control unit 12 may output information indicating that the streak-shaped abnormality has been detected to the output unit 16 to notify the user. Further, the control unit 12 may detect the detection candidate pixel 54 corresponding to the extraction straight line 58 as abnormal.
- the control unit 12 generates detection candidate pixels 54 (see FIG. 4 or 5) emphasized by the difference image 52 and approximate straight lines 56 (see FIG. 5) generated based on the detection candidate pixels 54. may be overlaid on the average image 50 to produce the resulting image 60 .
- the control unit 12 may highlight and display the detection candidate pixel 54 corresponding to the extraction straight line 58 extracted in FIG. Further, the control unit 12 may emphasize and display the extraction straight line 58 as the detection straight line 64 in the result image 60 .
- the control unit 12 may notify the user of the visual inspection result by displaying the result image 60 on the output unit 16 .
- the control unit 12 may cause the output unit 16 to display the entire image 40 or the average image 50 .
- control unit 12 can detect the film unevenness abnormality (second abnormality) based on the brightness of the average image 50 .
- FIG. 1 An example of film unevenness within the wafer surface is shown in FIG.
- An average image 50 of the wafer surface with film unevenness is represented as a film unevenness image 70 .
- the brightness of a central region 72 near the center of the wafer surface is low. That is, the central region 72 is represented in a color close to black.
- the brightness of the peripheral region 74 near the edge of the wafer surface is high. That is, the peripheral area 74 is represented in a color close to white.
- the control unit 12 In the average image 50, the control unit 12 generates an image by averaging the brightness of pixels at positions corresponding to the first parts image 41 to the fifth parts image 45 in FIG.
- the images obtained by averaging the brightness of the positions corresponding to the respective parts images from the first part image 41 to the fifth parts image 45 are the first brightness average image 81 to the fifth brightness average image. up to 85.
- the control unit 12 classifies the images for calculating the luminance average image into five groups, but the control unit 12 may classify the images into four or less groups, or six or more groups. .
- the control unit 12 calculates the average brightness of each image from the first average brightness image 81 to the fifth average brightness image 85 .
- the control unit 12 normalizes the average brightness. In this embodiment, assuming that the average brightness of the second average brightness image 82 is unlikely to vary between wafers, the control unit 12 sets the average brightness of the second average brightness image 82 to 100%, and the average brightness of the other images. was standardized.
- the image serving as a reference for normalization is not limited to the second average luminance image 82, but may be other images such as the first average luminance image 81, the third average luminance image 83, the fourth average luminance image 84, or the fifth average luminance image 85. It can be an image. Normalized average luminance is also referred to as normalized average luminance. When the normalized average luminance is below the determination threshold, the control unit 12 determines that the wafer has a film unevenness abnormality.
- FIG. 10 An example of the calculation result of the normalized average luminance is shown as a graph in FIG.
- the horizontal axis of the graph in FIG. 10 represents the wafer in-plane position.
- “Outermost circumference” represents a position corresponding to the first parts image 41 .
- “Second round” represents the position corresponding to the second parts image 42 .
- “Third Round” represents a position corresponding to the third parts image 43 .
- “Fourth round” represents a position corresponding to the fourth parts image 44 .
- a “central portion” represents a position corresponding to the fifth parts image 45 .
- the vertical axis represents the normalized average luminance calculated based on the luminance average image at each position.
- the determination threshold is represented by X%.
- a graph in which the normalized average luminance at each position is represented by a circle ( ⁇ ) has a normalized average luminance of X% or more at all positions.
- the control unit 12 determines that the abnormal film unevenness has not occurred in the wafer corresponding to the graph in which the normalized average brightness is represented by circles.
- the normalized average luminance at each position is represented by triangles ( ⁇ )
- the normalized average luminance is less than X% at some positions.
- the control unit 12 determines that the abnormal film unevenness has occurred in the wafer corresponding to the graph in which the normalized average luminance is represented by triangles. That is, the control unit 12 can compare the normalized average luminance with the determination threshold to determine whether or not the film unevenness abnormality has occurred.
- the decision threshold may be set to various values such as 80% or 90%.
- the control unit 12 of the visual inspection apparatus 10 may execute the visual inspection method including the procedure of the flowchart illustrated in FIG. 11 .
- the visual inspection method may be realized as a visual inspection program executed by a processor that constitutes the control unit 12 .
- the visual inspection program may be stored on a non-transitory computer-readable medium.
- the control unit 12 acquires a parts image (step S1).
- the control unit 12 generates the overall image 40 based on the parts 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 detect in the first mode (step S4). When detecting in the first mode (step S4: YES), the control unit 12 proceeds to step S5. If not detected in the first mode (step S4: NO), the control unit 12 proceeds to step S7.
- the control unit 12 When detecting in the first mode, the control unit 12 takes the difference between the whole image 40 and the average image 50 to generate a difference image 52 (step S5).
- the control unit 12 detects the first abnormality (striped abnormality) based on the difference image 52 (step S6).
- the control unit 12 may execute binarization processing, or linear approximation processing and same-slope extraction processing in the procedure of step S6. After executing the procedure of step S6, the control unit 12 proceeds to the procedure of step S9.
- control unit 12 When detecting in the second mode, the control unit 12 calculates the average luminance at each position within the wafer surface (step S7). The control unit 12 detects a second abnormality (film unevenness) based on the calculated average luminance (step S8). After executing the procedure of step S8, the control unit 12 proceeds to the procedure of step S9.
- 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 of FIG.
- the control unit 12 may perform both detection in the first mode and detection in the second mode.
- the control unit 12 may detect the first mode first, detect the second mode first, or detect the first mode and the second mode in parallel. may
- an image emphasizing the abnormalities on the wafer surface of the film-coated wafer can be generated.
- the quality of the film-coated wafer can be improved.
- the quality of film-coated wafers can be improved.
- appearance inspection system 10 appearance inspection device (12: control unit, 14: input unit, 16: output unit) 20 Imaging device 30 Conveying device 40 Overall image (41 to 45: 1st to 5th part images) 50 average image 52 difference image (54: detection candidate pixel, 56: approximate straight line, 58: extracted straight line) 60 result image (62: detection pixel, 64: detection straight line) 70 film unevenness image (72: central region, 74: peripheral region) 81 to 85 1st to 5th luminance average images
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Abstract
Description
[1]
ウェーハ面を円周方向に沿って複数の領域に分けて撮影したパーツ画像を含む前記ウェーハ面の複数の全体画像を生成し、前記複数の全体画像に基づいて平均画像を生成し、前記平均画像に基づいて前記ウェーハ面の異常を検出する制御部を備える、外観検査装置。
[2]
前記制御部は、前記複数の全体画像それぞれを、異なる輝度で撮影した前記パーツ画像に基づいて生成する、上記[1]に記載の外観検査装置。
[3]
前記制御部は、前記平均画像と前記全体画像との差分をとった差分画像に基づいて前記ウェーハ面の異常を検出する、上記[1]又は[2]に記載の外観検査装置。
[4]
前記制御部は、前記差分画像において輝度が第1閾値以上である画素を検出候補画素として抽出し、前記検出候補画素の中から前記ウェーハ面の異常を検出する、上記[3]に記載の外観検査装置。
[5]
前記制御部は、前記検出候補画素の位置に基づいて近似直線を生成し、前記近似直線の傾きの差が第2閾値以内になる前記近似直線の組み合わせに対応する前記検出候補画素を異常として検出する、上記[4]に記載の外観検査装置。
[6]
前記制御部は、前記平均画像のうち、前記ウェーハ面の中心を含む中央領域における平均輝度と、前記中央領域以外の周辺領域における平均輝度との差に基づいて前記ウェーハ面の異常を検出する、上記[1]から[5]までのいずれか1つに記載の外観検査装置。
[7]
ウェーハ面を円周方向に沿って複数の領域に分けて撮影したパーツ画像を含む前記ウェーハ面の複数の全体画像を生成することと、
前記複数の全体画像に基づいて平均画像を生成することと、
前記平均画像に基づいて前記ウェーハ面の異常を検出することと
を含む外観検査方法。
[8]
前記複数の全体画像それぞれを、異なる輝度で撮影した前記パーツ画像に基づいて生成することを更に含む、上記[7]に記載の外観検査方法。
以下、本開示の一実施形態に係るウェーハの外観検査システム100及び外観検査装置10が図面を参照して説明される。図1に示されるように、ウェーハの外観検査システム100は、外観検査装置10と、撮像装置20と、搬送装置30とを備える。撮像装置20又は搬送装置30は、外観検査装置10に含まれてもよい。
外観検査システム100において、撮像装置20は、ウェーハ面のパーツ画像を撮影する。本実施形態において、撮像装置20は、照明光の照度を3段階に変更し、各照度においてパーツ画像を撮影する。照度の段階数は、2であってもよいし4以上であってもよい。つまり、撮像装置20は、照明光の照度を複数の段階に変更し、各照度においてパーツ画像を撮影する。撮像装置20は、照明光の照度を異ならせることによって、各照度の照明光で照らしたウェーハ面を撮影したパーツ画像を生成する。撮像装置20は、照明光の照度を3段階に変更する場合、3種類のパーツ画像を生成する。照明光の照度が変更されることによって、各照度に対応するパーツ画像の輝度が互いに異なる。
制御部12は、第1モードで動作する場合、全体画像40と平均画像50との差分をとった画像として、図4に例示される差分画像52を生成する。制御部12は、輝度が異なる複数の全体画像40それぞれと平均画像50との差分をとってもよい。制御部12は、少なくとも1つの輝度における全体画像40と平均画像50との差分をとってもよい。図4に例示される差分画像52は、全体画像40と平均画像50との差分を更に2値化した画像である。差分画像52において、輝度が高い(白で表される)画素は、検出候補画素54とも称される。制御部12は、2値化処理によって白になった画素を検出候補画素54として抽出してよい。制御部12は、差分画像52において、輝度が所定値以上の画素を検出候補画素54として抽出してもよい。検出候補画素54を抽出する基準となる所定値は、第1閾値とも称される。制御部12は、第1閾値に基づいて差分画像52を2値化してもよい。例えば、制御部12は、第1閾値以上の輝度の画素を白にして第1閾値未満の輝度の画素を黒にする2値化を実行してよい。
制御部12は、第2モードで動作する場合、平均画像50の輝度に基づいて膜むら異常(第2異常)を検出できる。
外観検査装置10の制御部12は、図11に例示されるフローチャートの手順を含む外観検査方法を実行してもよい。外観検査方法は、制御部12を構成するプロセッサに実行させる外観検査プログラムとして実現されてもよい。外観検査プログラムは、非一時的なコンピュータ読み取り可能な媒体に格納されてよい。
10 外観検査装置(12:制御部、14:入力部、16:出力部)
20 撮像装置
30 搬送装置
40 全体画像(41~45:第1~第5パーツ画像)
50 平均画像
52 差分画像(54:検出候補画素、56:近似直線、58:抽出直線)
60 結果画像(62:検出画素、64:検出直線)
70 膜むら画像(72:中央領域、74:周辺領域)
81~85 第1~第5輝度平均画像
Claims (8)
- ウェーハ面を円周方向に沿って複数の領域に分けて撮影したパーツ画像を含む前記ウェーハ面の複数の全体画像を生成し、前記複数の全体画像に基づいて平均画像を生成し、前記平均画像に基づいて前記ウェーハ面の異常を検出する制御部を備える、外観検査装置。
- 前記制御部は、前記複数の全体画像それぞれを、異なる輝度で撮影した前記パーツ画像に基づいて生成する、請求項1に記載の外観検査装置。
- 前記制御部は、前記平均画像と前記全体画像との差分をとった差分画像に基づいて前記ウェーハ面の異常を検出する、請求項1又は2に記載の外観検査装置。
- 前記制御部は、前記差分画像において輝度が第1閾値以上である画素を検出候補画素として抽出し、前記検出候補画素の中から前記ウェーハ面の異常を検出する、請求項3に記載の外観検査装置。
- 前記制御部は、前記検出候補画素の位置に基づいて近似直線を生成し、前記近似直線の傾きの差が第2閾値以内になる前記近似直線の組み合わせに対応する前記検出候補画素を異常として検出する、請求項4に記載の外観検査装置。
- 前記制御部は、前記平均画像のうち、前記ウェーハ面の中心を含む中央領域における平均輝度と、前記中央領域以外の周辺領域における平均輝度との差に基づいて前記ウェーハ面の異常を検出する、請求項1から5までのいずれか一項に記載の外観検査装置。
- ウェーハ面を円周方向に沿って複数の領域に分けて撮影したパーツ画像を含む前記ウェーハ面の複数の全体画像を生成することと、
前記複数の全体画像に基づいて平均画像を生成することと、
前記平均画像に基づいて前記ウェーハ面の異常を検出することと
を含む外観検査方法。 - 前記複数の全体画像それぞれを、異なる輝度で撮影した前記パーツ画像に基づいて生成することを更に含む、請求項7に記載の外観検査方法。
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