JP2008014768A - Defect inspection device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect inspection device and method capable of detecting a fault of the device itself. <P>SOLUTION: A storage part 207 stores reference information acquired by imaging a reference subject beforehand. A defect extraction part 205 compares comparison object information acquired by imaging the reference subject after acquiring the reference information with the reference information stored in the storage part 207, and extracts a different portion between both information as defects. A defect determination part 206 determines the occurrence of the fault of the device itself based on extraction results of the defects. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defect inspection apparatus and a defect inspection method for inspecting a defect of an inspection object.

In the manufacturing process and inspection process of semiconductor devices and flat panel displays (FPDs), the surface image of a sample (product) is captured by a CCD camera or the like to generate an image, and the comparison data and the actual image data are compared. Thus, a defect inspection apparatus for determining the quality of a sample is used. In such an apparatus, an unexpected trouble may occur for some reason during operation. At this time, it is necessary to solve the problem as soon as possible and restore the apparatus. Therefore, various proposals have been made in order to shorten the downtime from the occurrence of trouble (see, for example, Patent Documents 1, 2, and 3).
JP 2002-268721 A JP 2003-99114 A JP-A-8-161008

  However, in the apparatus that automatically inspects defects as in the above-described prior art, it is caused by the occurrence of an abnormality in the apparatus itself other than the trouble that makes the operation unusable and becomes unusable. Although there is no hindrance to the operation, a trouble that an abnormal inspection result is output and many false defective products are generated occurs. When such a trouble occurs, if the operator does not notice the abnormality of the apparatus, the work is continued as it is, and the reliability of the inspection may be lost. In addition, a large number of defective products may reduce the yield, leading to an increase in the manufacturing cost of the manufactured product.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a defect inspection apparatus and a defect inspection method capable of detecting an abnormality of the apparatus itself.

  The present invention has been made to solve the above problems, and in a defect inspection apparatus for inspecting a defect of an inspection object, an imaging means for imaging a reference subject and a reference obtained by imaging the reference subject Storage means for storing information, and determination means for determining presence / absence of abnormality of the apparatus itself based on a result of comparing the reference information with comparison target information obtained by imaging the reference subject after obtaining the reference information And a defect inspection apparatus characterized by comprising:

  Further, the present invention provides a defect inspection method for inspecting a defect of an inspection object. After acquiring a reference information by imaging a reference subject, comparison target information obtained by imaging the reference subject and the reference information The defect inspection method is characterized in that the presence / absence of abnormality of the apparatus itself is determined based on the result of comparing the above.

  When the state of the device when the reference information is acquired is different from the state of the device when the comparison target information is acquired, a difference occurs between the reference information and the comparison target information due to the difference in the state. Therefore, according to the present invention, it is possible to detect an abnormality of the apparatus itself by comparing the reference information and the comparison target information.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, a first embodiment of the present invention will be described. FIG. 1 shows the configuration of the defect inspection apparatus according to the present embodiment. In addition to the function of performing defect inspection as a normal substrate inspection apparatus, this defect inspection apparatus also has a function of performing self-diagnosis for detecting the presence or absence of abnormality of the apparatus itself. The holding unit 101 holds a substrate 1 (inspection object, subject) such as a semiconductor wafer or an FPD glass substrate. The holding rotation unit 102 rotates the substrate 1 held by the holding unit 101 in an arbitrary direction within the plane. The base unit 103 is configured to be movable with the holding unit 101 and the holding rotation unit 102 mounted thereon.

  The illuminating unit 104 causes light from the lamp to enter an optical fiber whose emission end is formed in a linear shape, and irradiates the substrate 1 held by the holding unit 101 with linear illumination light. The illumination condenser lens 105 is a cylindrical lens, and condenses the illumination light emitted from the illumination unit 104 on the substrate 1 in a plane parallel to the paper surface. The condenser lens 106 acts as a field lens in a plane perpendicular to the paper surface, and collects the reflected light reflected by the surface of the substrate 1. The filter unit 107 includes a filter group that arbitrarily selects the wavelength and polarization state of the light collected by the condenser lens 106. The imaging unit 108 includes a lens and a line sensor camera. The light that has passed through the filter unit 107 is imaged by the lens and converted into an electrical signal by the line sensor camera. At this time, imaging is performed while the base portion 103 moves together with the substrate 1 in the direction of the arrow in FIG.

  The defect inspection apparatus also includes a substrate transport unit (not shown) that mounts the substrate 1 on the holding unit 101. The illumination unit 104, the condensing lens 105, the imaging unit 108, the filter unit 107, and the condensing lens 106 are integrally supported by support members (not shown). Then, they rotate around an axis perpendicular to the paper surface passing through each optical axis intersection on the substrate.

  2 receives the electrical signal output from the imaging unit 108 via the imaging control unit 208, generates two-dimensional image information based on the electrical signal, and recognizes defects by image processing. Then, the quality of the substrate 1 is determined. The overall control unit has an apparatus control function and an image processing function. In FIG. 2, an apparatus control unit 201 controls the defect inspection apparatus to operate the apparatus. The image generation unit 202 generates image information from the electrical signal output from the imaging control unit 208. The position correction unit 203 compares the image information to be compared (comparison target image information) generated by the image generation unit 202 with the reference image information (reference image information) stored in the storage unit 207 in advance. Then, the positional deviation of the images is detected, and the captured image is moved to correct the positional relationship between the two images.

  The luminance correction unit 204 extracts the luminance of the comparison target image information whose position is corrected by the position correction unit 203, detects a difference in luminance compared with the luminance of the reference image information stored in the storage unit 207, and In order to correct the luminance difference between the two pieces of image information, the luminance of the comparison target image information is matched with the luminance of the reference image information. The defect extraction unit 205 compares the comparison target image information whose luminance has been corrected by the luminance correction unit 204 with the reference image information stored in the storage unit 207, and compares the luminance with a difference of a certain value (threshold value) or more. A certain part is determined as a defect. The defect determination unit 206 classifies the type and importance of the defect based on the luminance difference and shape information of the defect extracted by the defect extraction unit 205.

  The storage unit 207 stores image information and the like used for defect inspection. The imaging control unit 208 drives the filter unit 107 and the imaging unit 108 and controls the rotation operations of the filter unit 107, the imaging unit 108, and the condenser lens 106 in order to perform appropriate imaging. Further, the imaging control unit 208 transmits an electrical signal of the image to the image generation unit 202. The illumination control unit 209 controls dimming of the illumination unit 104 and controls the rotation operation of the illumination unit 104 and the condenser lens 105. The holding rotation driving unit 210 drives the holding rotation unit 102. The holding drive unit 211 drives the holding unit 101. The display unit 212 is a monitor such as a liquid crystal display, and displays the inspection status and control command buttons. The operation unit 213 includes a keyboard, a mouse, a touch panel, and the like that are used by an operator to operate the apparatus. When the operator operates the operation unit 213, the operation unit 213 gives an instruction to the apparatus control unit 201. It is possible.

  Note that the apparatus control unit 201, the image generation unit 202, the position correction unit 203, the luminance correction unit 204, the defect extraction unit 205, and the defect determination unit 206 may operate by loading a program into a memory or electronic It may be a circuit.

  Hereinafter, the details of the main part of the defect inspection apparatus will be described focusing on the functions related to the self-diagnosis of the apparatus. The holding unit 101 is, for example, a vacuum chuck stage, and is movable in a state where the substrate 1 is sucked and held in accordance with a drive signal from the holding drive unit 211. The holding rotation unit 102 can rotate the substrate 1 in accordance with a drive signal from the holding rotation driving unit 210.

  In addition, since the holding unit 101 functions as a reference subject used to detect whether there is an abnormality in the apparatus itself, as illustrated in FIG. 3, image information is obtained when the reflected light of the illumination light from the illumination unit 104 is captured. A region 101A and a region 101B having different surface states are formed on the surface of the holding unit 101 so that the luminance of the center differs from that of the periphery. Further, the base portion 103 is painted with black matte so that the illumination light is not reflected. However, holes, grooves, edges and the like for vacuum suction are originally formed, but FIG. 3 is a schematic diagram in which they are omitted.

  For example, the illumination unit 104 is provided so that the illumination angle with respect to the holding unit 101 can be changed by rotation, and the substrate 1 on the holding unit 101 is irradiated with light from various angles according to a command from the illumination control unit 209. In addition, the amount of light can be changed. The filter unit 107 can switch a combined filter such as a narrowband filter, a polarization filter, or an ND filter in accordance with a command from the imaging control unit 208. When the imaging control unit 208 outputs a drive signal based on a command from the device control unit 201, the filter of the filter unit 107 can be changed as appropriate.

  The substrate transport unit (not shown) includes, for example, a part that opens and closes the lid of the carrier on which the substrate 1 is mounted and a transport robot, and takes out the substrate 1 contained in the carrier according to a command from the apparatus control unit 201 and transports it to the holding unit 101 It is possible to do.

  The image generation unit 202 receives an electrical signal generated by the imaging operation of the imaging unit 108 via the imaging control unit 208, and generates two-dimensional image information based on the electrical signal. In the storage unit 207, coordinate information and image information of a plurality of closed regions (for example, the closed regions 301 to 304 in FIG. 3) on the holding unit 101 are stored together with the entire reference image information of the holding unit 101.

  The position correction unit 203, based on the coordinate information of a plurality of closed regions instructed in advance by the device control unit 201, the closed region image information (first closed region image information) stored in the storage unit 207, The comparison target image information generated by the image generation unit 202 is compared with part of the closed region image information (second closed region image information). Further, the position correction unit 203 sequentially compares the first closed region image information and the second closed region image information while shifting the closed region in the comparison target image on the image, and performs a comparison corresponding to the closed region on the reference image. A closed region on the target image is detected. Then, based on the detected position, the position correction unit 203 moves the coordinates of the comparison target image so that the reference image and the position on the image are the same.

  The brightness correction unit 204 can change the gain and offset value of the comparison target image information so that the brightness of the reference image information and the comparison target image information in the closed region are substantially the same. The defect extraction unit 205 can generate information on the difference between the reference image information and the comparison target image information (difference image information), and extract a portion having a large luminance difference from the difference image information as a defect. At this time, a threshold value that determines how much the luminance difference is to be determined as a defect is stored in the storage unit 207, read by the apparatus control unit 201, and passed to the defect extraction unit 205.

  The defect determination unit 206 determines the type of defect, the importance of the defect, or the defect based on the information on the luminance difference of the defect extracted by the defect extraction unit 205, the information on the position where the defect occurred, and the shape information of the defect. Identify the cause of the occurrence.

  Next, a self-diagnosis method using this defect inspection apparatus will be described. FIG. 4 shows a procedure of processing related to self-diagnosis. In the data creation step (step S11) in FIG. 4, in order to perform self-diagnosis, the holding unit 101 without the substrate 1 is imaged in advance as a reference subject to generate reference image information, and the reference information serving as a reference is used as a reference. This is a step of generating from image information. After the data creation process, the inspection device performs normal inspection. The processing step (step S12) is a step of processing the newly generated comparison target image information so that it can be compared with the reference image information in a later step.

  The defect extraction step (step S13) is a step of comparing the newly generated comparison target image information with the reference image information to extract defects. If a defect is extracted in the defect extraction step, it is determined in the determination step (step S14) that an abnormality has occurred in the apparatus, and the specific cause is specified. A display process (step S15) is a process of displaying a determination result. Steps S <b> 12 to S <b> 15 are inspection processes of the apparatus itself that are started by some operation instruction or a certain period of time after performing a normal inspection.

  The details of each of the above steps will be described below. First, immediately after setting up the apparatus or immediately after replacing the lamp of the lighting unit 104, when the operator operates the operation unit 213 and inputs an execution instruction for calibration processing, a data generation step (step S11) is performed. The In this data generation step, first, the holding unit 101 moves toward the illumination light irradiation position by the illumination unit 104. During this movement, an imaging command is issued from the apparatus control unit 201 to the imaging control unit 208, and the imaging unit 108 starts imaging in response to an instruction from the imaging control unit 208 that has received the imaging command.

  When the holding unit 101 crosses the illumination light, the surface of the substrate 1 is irradiated with illumination light that has been adjusted in advance so as to be incident on the holding unit 101 at an optimal angle and with an optimal amount of light, and the reflected light is applied to the imaging unit. 108 is incident. The electrical signal output from the imaging unit 108 is output to the image generation unit 202 via the imaging control unit 208. The image generation unit 202 generates two-dimensional image information (reference image information) of horizontal X pixels / vertical Y pixels based on the input electrical signal, and outputs the two-dimensional image information (reference image information) to the position correction unit 203.

  The position correction unit 203 detects a plurality of closed regions whose positions are most easily specified in the generated image. Then, the position correction unit 203 notifies the device control unit 201 of the coordinate information of the closed region. The device control unit 201 stores the coordinate information in the storage unit 207. Subsequently, the reference image information is output to the luminance correction unit 204. The luminance correction unit 204 generates luminance information from the reference image information and notifies the device control unit 201 of the luminance information. The device control unit 201 stores the luminance information in the storage unit 207. Subsequently, the reference image information is output to the defect extraction unit 205.

  The defect extraction unit 205 recognizes the defect as a defect when a defect extraction parameter used when extracting the defect by comparing the reference image information and the comparison target image information, that is, when a difference in luminance exceeding a predetermined value occurs. Set a threshold for this. This threshold value is stored in the storage unit 207 as a defect extraction parameter. The reference image information is stored in the storage unit 207 as reference information.

  Subsequently, when the apparatus control unit 201 recognizes that the normal substrate inspection is not performed and the self-diagnosis is not performed for a predetermined period, the self-diagnosis is started, and the processing step (step The process proceeds to S12). The apparatus control unit 201 reads coordinate information, luminance information, reference image information, and defect extraction parameters from the storage unit 207. Then, the apparatus control unit 201 issues a command to the holding rotation driving unit 210 and the holding driving unit 211 in a state where the substrate 1 is not mounted on the holding unit 101, and the surface of the holding unit 101 is subjected to a data creation process (step S11). It is assumed that imaging is possible under the same conditions as in FIG.

  The imaging unit 108 images the surface of the holding unit 101, and the image generation unit 202 generates comparison target image information. The position correcting unit 203 compares the image information of the closed region in the reference image with the image information of the closed region in the comparison target image based on the coordinate information notified from the device control unit 201, and compares the image information in the comparison target image. To identify a place that can be assumed to be the same as the closed region in the reference image. By performing the same operation for a plurality of closed regions in the comparison target image, how much the position of the closed region recognized as the same position in the comparison target image is shifted from the position of the closed region in the reference image. Can be measured. The position correction unit 203 moves the comparison target image based on the measurement result so that the position on the image is the same as the reference image.

  Subsequently, the position-corrected comparison target image information is output to the luminance correction unit 204. The luminance correction unit 204 detects the coordinates of the closed region in the comparison target image based on the coordinate information, and obtains the luminance value of the pixels included in the closed region. Also, the luminance correction unit 204 extracts and refers to the luminance value of the pixel included in the closed region in the reference image corresponding to the closed region from the luminance information, and the luminance distribution of the comparison target image information and the reference image information is almost equal. In order to make it uniform, a gain is applied to the luminance of the entire comparison target image information or an offset is added. As a result, even if the luminance of both is slightly changed, it is possible to correct the comparison target image information so that the luminance characteristics are almost the same as those of the reference image information. The luminance-corrected image information is output to the defect extraction unit 205.

  Subsequently, in the defect extraction step (step S13), the defect extraction unit 205 receives the defect extraction parameter and the reference image information from the apparatus control unit 201, and uses the comparison target image information and the reference image information output from the luminance correction unit 204. Difference image information is generated by comparing and taking the difference. The defect extraction unit 205 further detects a part where the luminance difference included in the difference image information exceeds the threshold indicated by the defect extraction parameter, identifies the defect, and outputs the difference image information of the part to the defect determination unit 206.

  Then, it transfers to a determination process (step S14) and defect determination is implemented. That is, it is determined what kind of cause the defect extracted in the defect extraction step (step S13) is.

  For example, when the timing of the imaging timing signal output from the imaging control unit 208 and the movement signal of the holding unit 101 output from the holding drive unit 211 are deviated, there is no difference between the reference image and the comparison target image. A difference in luminance occurs at the end in the vertical direction. If this difference exceeds the threshold indicated by the defect extraction parameter, a defect 501 as shown in FIG. 5 is detected.

  Alternatively, when the positions of the condenser lens 106 and the imaging unit 108 are moved for some reason or when an optical axis shift occurs, the position of the image is different from the original position. In the present embodiment, the positional deviation of the image is corrected by the position correcting unit 203, but the positional deviation exceeding the range assumed in advance cannot be corrected. For this reason, a difference in luminance occurs between the reference image and the comparison target image at the left and right ends. In this case, a defect 601 as shown in FIG. 6 is detected.

  Further, when the imaging unit 108 includes a line sensor camera, when an abnormality occurs in some pixels, the comparison target image is an image as if a vertical line extending in the vertical direction has been entered. When the luminance difference between the pixels on the vertical line in the comparison target image and the reference image is greater than or equal to the threshold value, the defects 701 and 702 are extracted as shown in FIG. As described above, the defect determination unit 206 determines the image abnormality caused by the abnormality of the device, estimates the cause of the abnormality of the device in consideration of the position / luminance difference / shape information of the defect, and the estimation result is obtained. Notify the device control unit 201.

  Subsequently, in the display step (step S15), a warning message is displayed on the display unit 212 together with specific abnormality contents, defect positions, and captured images.

  As described above, in the present embodiment, based on the difference between the reference image information obtained by imaging the reference subject and the comparison target image information obtained by imaging the reference subject after obtaining the reference image information, It is determined whether there is an abnormality in the device itself. If the state of the device when the reference image information is acquired is different from the state of the device when the comparison target image information is acquired, the reference image information and the comparison target image information are changed due to the difference in the state. Differences occur. Therefore, the abnormality of the apparatus itself can be detected by comparing the reference image information and the comparison target image information as in the present embodiment.

  In addition, by using the surface of the holding unit 101 as a reference subject, it is not necessary to place a sample for self-diagnosis on the holding unit 101 when performing self-diagnosis of the apparatus, and the time required for self-diagnosis can be reduced. Can do. Furthermore, the surface of the reference subject has a plurality of regions (regions 101A and 101B in FIG. 3), and the brightness of the reference subject is different so that the luminance in the image information obtained by imaging the surface of the reference subject varies from region to region. By configuring the reference subject by changing the surface state for each region, it is possible to easily detect an abnormality of the apparatus by comparing the luminance in the two pieces of image information.

  In addition, by comparing the reference image information and the comparison target image information and extracting defects caused by the abnormality of the apparatus, it is possible to more suitably detect the presence or absence of an abnormality in the imaging system or the illumination system.

  In addition, by executing a self-diagnosis of the apparatus while the apparatus is on standby due to a lot change or the like, it is possible to detect an abnormality of the apparatus without affecting the substrate inspection. In addition, by performing the self-diagnosis described above regularly, it is possible to quickly notify the operator of an abnormal failure on the device side and notify the operator of the abnormality, and prompt the operator for a corrective action and reduce the downtime of the device. can do.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 8 is a plan view of the holding unit 101 according to the present embodiment. On the surface of the holding unit 101, pins 801 for holding the substrate 1 in contact with a small area are arranged. In addition, a plurality of holes for vacuum suction (not shown) are formed near the center of the surface of the holding portion 101, and the space between the edge contacting the edge of the substrate and the pin 801 is reduced by vacuum suction. By using the pressure, it is possible to hold the back surface of the substrate 1 on the surface of the holding portion 101 while supporting the back surface with a small area. Further, in a region where the plurality of pins 801 are uniformly arranged, pin groups 802 to 806 in which the arrangement of the pins is changed so as to be a mark are formed in one place in the central portion and four places in the peripheral portion. Yes.

  Hereinafter, a self-diagnosis method according to this embodiment will be described with reference to FIGS. FIG. 9 shows details of the data generation step (step S11) of FIG. In the data generation step (step S11), the position correction unit 203 detects a closed region including at least one of the pin groups 802 to 806 serving as landmarks from the reference image information obtained by imaging the holding unit 101. The coordinate information and the reference image information of the closed region are transferred to the device control unit 201 and stored in the storage unit 207 (step S111). Subsequently, the reference image information is output to the luminance correction unit 204.

  The luminance correction unit 204 detects the luminance of the reference image information in the closed region based on the coordinate information, and notifies the device control unit 201 of the luminance information. This luminance information is stored in the storage unit 207 (step S112). Subsequently, the reference image information is output to the defect extraction unit 205.

  The defect extraction unit 205 recognizes the defect as a defect when a defect extraction parameter used when extracting the defect by comparing the reference image information and the comparison target image information, that is, when a difference in luminance exceeding a predetermined value occurs. A threshold value is set for this (step S113). This threshold value is stored in the storage unit 207 as a defect extraction parameter. The reference image information is stored in the storage unit 207 as reference information.

  Subsequently, in the processing step (step S <b> 12), the imaging unit 108 images the surface of the holding unit 101, and the image generation unit 202 generates comparison target image information. The position correction unit 203 compares the image information of the closed region in the reference image with the image information of the closed region in the comparison target image based on the coordinate information, and determines the closed region in the reference image in the comparison target image. Identify locations that can be assumed to be the same.

  Then, the position correction unit 203 moves the comparison target image so that the position on the image is the same as the reference image. In this embodiment, since a unique pin array serving as a mark exists in the closed region, it is easy to detect the pin array even in image processing, and more accurate alignment is possible. The comparison target image information subjected to the alignment is output to the luminance correction unit 204, and the luminance correction is performed by the luminance correction unit 204.

  Subsequently, in the defect extraction step (step S13), the defect extraction unit 205 compares the comparison target image information with the reference image information, and generates difference image information by taking the difference. The defect extraction unit 205 further detects a part where the luminance difference included in the difference image information exceeds the threshold indicated by the defect extraction parameter, identifies the defect, and outputs the difference image information of the part to the defect determination unit 206.

  When a pin 801 arranged on the surface of the holding unit 101 or a pin group 802 to 806 serving as a mark is displaced, a defect is detected. Therefore, the timing at the time of imaging, the movement of the optical system, the abnormality of the imaging unit Etc. can be detected in the same manner as in the first embodiment. Since the determination step (step S13) and the display step (step S14) are the same as those in the first embodiment, the description thereof is omitted.

  According to the present embodiment, it is possible to obtain the same effect as that of the first embodiment by slightly changing the surface shape of the holding unit 101, and it is possible to accurately correct the abnormality of the apparatus while suppressing the manufacturing price of the holding unit 101. Can be captured. Even if there is no specific pin arrangement in the closed region, if sufficient alignment is possible, the specific pin arrangement is not necessary. Abnormalities can be detected.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 10 is a plan view of the holding unit 101 according to the present embodiment. Similar to the second embodiment, pins 1001 are arranged on the surface of the holding unit 101, and further, pin groups 1002 to 1005 in which the arrangement of the pins is changed are provided at specific locations.

  Furthermore, rectangular high reflectivity regions 1006 to 1010 having a relatively high reflectivity are provided at the central portion and the peripheral portion of the surface of the holding portion 101. The reflectivity in the high reflectivity regions 1006 to 1010 is substantially uniform, and when the imaging unit 108 images the surface of the holding unit 101, the high reflectivity regions 1006 to 1010 are imaged as rectangles having uniform luminance values. It can be done. Since all of the five high reflectance regions are created to have the same reflectance, there are five rectangular portions with uniform luminance in the image.

  Also, a resolution chart 1011 whose height is adjusted to be the same height as the surface of the substrate 1 when the substrate 1 is mounted on the holding unit 101 around the holding unit 101 on the surface of the base unit 103. 1014 is installed. In the resolution (or resolving power) charts 1011 to 1014, a plurality of W / B (White / Black) patterns are formed vertically and horizontally at a spatial frequency corresponding to the resolving power of the imaging optical system, and the difference in luminance is compared. Thus, the resolving power of the optical system can be relatively measured.

  FIG. 11 shows the configuration of the image processing unit 109 according to the present embodiment. In the present embodiment, a luminance detection unit 214 and a resolution measurement unit 215 are added as compared to the image processing unit 109 (FIG. 2) according to the first and second embodiments. The luminance detection unit 214 measures luminance values in the image information of the high reflectance regions 1006 to 1010, and detects the average luminance and luminance distribution of each region.

The resolution measurement unit 215 detects a change in the pattern luminance of the resolution charts 1011 to 1014 in the reference image information and the comparison target image information for each pixel of the line sensor, thereby detecting a pseudo luminance change sampled discretely. Predict the resolving power of the optical system and output it as a measured value. An example of the measurement of the resolving power is given below. Assuming that the luminance of each W / B pattern is I (w) and I (b), the luminance change rate I (f) expressed by the following equation is measured for the pattern having each spatial frequency to Relative values can be evaluated.
I (f) = (I (w)-I (b)) / (I (w) + I (b))

  For example, assuming that the value of I (f) is 0.2 or more, it is evaluated how many spatial frequencies of the vertical and horizontal resolution charts are resolved. The maximum spatial frequency or chart number that is resolved is the resolution value.

  Next, a self-diagnosis method according to this embodiment will be described with reference to FIGS. A data creation process is executed at the time of device setup or lamp replacement. FIG. 12 shows details of this data creation process. First, in the luminance unevenness information detection step (step S21), the luminance detection unit 214 detects the luminances of the high reflectance regions 1006 to 1010 in the reference image information obtained by imaging the surface of the holding unit 101, and the respective regions. Measure the average brightness, maximum brightness, minimum brightness, brightness distribution, etc. The measurement result is stored in the storage unit 207 as luminance information.

  Subsequently, in the resolution measurement step (step S22), the resolution measurement unit 215 measures the resolution of the resolution charts 1011 to 1014 based on the reference image information. The measurement result is stored in the storage unit 207 as resolution information. Similarly to steps S111 to S113 of FIG. 9 in the second embodiment, in steps S23 to S25, coordinate information, luminance information, and defect extraction parameters of the closed region are created and stored in the storage unit 207.

  FIG. 13 shows the operation during actual device operation. First, the apparatus control unit 201 determines whether or not the next inspection is reserved for the substrate 1 (step S31). If there is a next inspection reservation, the inspection is promptly executed (step S32). After this inspection is completed, the process returns to step S31 again. On the other hand, if the next examination reservation has not been entered, the apparatus control unit 201 determines whether or not a specified set time has elapsed since the previous self-diagnosis (step S33).

  If the specified set time has not elapsed since the previous self-diagnosis, the process returns to step S31 again. On the other hand, if the specified set time has elapsed since the previous self-diagnosis, the device control unit 201 determines that self-diagnosis is necessary. As a result, the device enters the self-diagnosis mode, and the processing step (step S34). Is executed.

  In the processing step, the apparatus control unit 201 reads necessary parameters from the storage unit 207 and notifies the luminance detection unit 214 of them. The luminance detection unit 214 detects the luminance of the high reflectance regions 1006 to 1010 in the comparison target image information generated by new imaging. Since these five areas are manufactured to have the same luminance, a difference in luminance in these areas means that an abnormality has occurred in the apparatus.

  For example, when the main surface of the holding unit 101 is inclined with respect to the horizontal plane, a phenomenon occurs in which the illumination light does not reach the imaging unit 108 and becomes dark even when reflected by the surface of the holding unit 101. In particular, when only one side of the main surface of the holding unit 101 is bent, the brightness of the five high reflectance regions is detected differently. The luminance detection unit 214 notifies the apparatus control unit 201 of luminance information of these high reflectance regions, and outputs comparison target image information to the resolution measurement unit 215.

  The resolution measuring unit 215 measures the resolving power of the resolution charts 1011 to 1014 in the reference image information and notifies the apparatus control unit 201 of the numerical data. For example, if the interval between components included in the optical system has changed for some reason, it is detected as a focus abnormality, so the numerical value of the resolving power also differs from the reference image information. In particular, in the optical system, an abnormality is likely to occur in the peripheral portion of the surface of the holding unit 101. Therefore, it is possible to accurately detect an abnormality in the apparatus by observing the resolving power at four locations in the peripheral portion.

  Subsequently, a defect extraction step (step S35) is performed. In the defect extraction step, the defect extraction unit 205 receives the luminance information detected by the luminance detection unit 214, the resolution information detected by the resolution measurement unit 215, and the luminance information and resolution information stored in the storage unit 207. Based on the information received from 201, it is determined whether or not there is an abnormality in the apparatus.

  In the determination regarding luminance, the defect extraction unit 205 determines that the variation in luminance of the high reflectance regions 1006 to 1010 detected in the processing step is out of the luminance distribution indicated by the luminance information stored in the storage unit 207. It is determined that there is an abnormality in the device. In the determination regarding the resolving power, the defect extracting unit 205 compares the numerical value of the resolving power detected in the processing step with the numerical value of the resolving power indicated by the resolving power information stored in the storage unit 207, and the difference between the two is determined as the defect extraction. If the threshold value indicated by the parameter is exceeded, it is determined that the device is abnormal. Further, the defect extraction unit 205 determines whether there is an abnormality in the image based on the difference image information between the reference image information and the comparison target image information. Subsequently, the determination process (step S36) and the display process (step S37) are executed in the same manner as in the first and second embodiments.

  According to the present embodiment, it is possible to accurately perform self-diagnosis while the apparatus is on standby for inspection, and it is possible to execute self-diagnosis of the apparatus without affecting the production amount. Furthermore, by detecting unevenness of brightness and resolution, abnormalities such as abnormal tilting of the holding unit 101, abnormal focus caused by deviations in the optical system spacing, and asymmetrical resolution such as one-sided blur due to optical system decentering. Etc. can be detected.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In this embodiment, a reference subject (for example, a bare wafer) provided with substantially uniform brightness of reflected light is used. FIG. 14 shows the configuration of the image processing unit 109 according to the present embodiment. In the present embodiment, position correction and luminance correction of image information are not performed. Further, the luminance detection unit 214 creates a histogram (luminance distribution) according to the luminance frequency in the reference image information. Furthermore, the defect extraction unit 205 determines whether there is an abnormality in the apparatus based on the histogram.

  Hereinafter, a self-diagnosis method in this embodiment will be described. This processing procedure is the same as in FIG. First, in the data creation step (step S11), the luminance detection unit 214 analyzes the luminance of a predetermined area in the reference image information obtained by imaging the surface of the substrate 1, and creates a histogram thereof. The obtained histogram is stored in the storage unit 207 together with other information.

  Subsequently, the defect extraction unit 205 determines that the luminance included in the histogram is normal, and determines at least two threshold values C and D in order to set a luminance range in which luminance not included in the histogram is determined to be abnormal. Those threshold values are stored in the storage unit 207 as defect extraction parameters.

  Subsequently, in the processing step (step S12), the luminance detection unit 214 analyzes the luminance of a predetermined area in the comparison target image information obtained by imaging the surface of the substrate 1, and creates a histogram thereof. The created histogram is output to the defect extraction unit 205.

  Subsequently, in the defect extraction step (step S13), the defect extraction unit 205 performs histogram quality determination processing. Specifically, the apparatus control unit 201 reads defect extraction parameters from the storage unit 207 and passes them to the luminance detection unit 214. The luminance detection unit 214 determines whether or not the luminance frequency is outside the range of the threshold C to the threshold D when the threshold C and the threshold D included in the defect extraction parameter are applied to the histogram created in the processing step. to decide.

  For example, as shown in FIG. 15A, when the luminance frequency is within the luminance range between the threshold C and the threshold D, the defect extraction unit 205 determines that the defect is normal. As shown in FIG. 15B, when the luminance frequency is distributed outside the luminance range between the threshold C and the threshold D, the defect extraction unit 205 determines that the defect is abnormal. The determination result by the defect extraction unit 205 is stored in the storage unit 207 as inspection result information separately for normal and abnormal.

  Subsequently, in the determination step (step S14), the defect determination unit 206 performs a histogram defect presence determination process. Specifically, the defect determination unit 206 receives the inspection result information from the apparatus control unit 201 and determines whether the apparatus is normal or abnormal based on the result of the histogram quality determination process indicated by the inspection result information.

  Subsequently, the determination result is displayed in the display step (step S15). Specifically, as a result of the determination, if the device is abnormal, the defect determination unit 206 sends a warning command to the display unit 212 via the device control unit 201. The display unit 212 displays a warning message based on the warning command.

  The following can be considered as specific abnormalities that can be detected in the determination step. When the imaging unit 108 includes a line sensor camera, when the holding unit 101 moves in a uniaxial direction and the shake occurs in the holding unit 101, a change in luminance appears according to the location in the image. Generally, when the shake of the holding unit 101 is up and down, it is called pitching, and when the shake of the holding unit 101 is left and right, it is called yawing. However, when the shake of the holding unit 101 is pitching, the luminance changes depending on the position in the vertical direction of the image. Thereby, a horizontal line-like defect is detected as an image.

  Also, when the shake of the holding unit 101 is yawing, a horizontal line-like defect is detected as an image, but the luminance value in the left-right direction of the defect is different. When the holding unit 101 repeats the movement, defects may occur in different places, or the defect generation state may change depending on the moving speed, and the speed of the holding unit 101 is changed according to the drive signal of the holding drive unit 211. From a plurality of captured images, it can be estimated that an abnormality due to pitching or yawing has occurred.

  Further, when the holding unit 101 itself is tilted, the image becomes dark as a whole, or the luminance changes in the tilt direction of the holding unit 101. In particular, when the portion above the holding rotation unit 102 is tilted, if the inspection is performed by rotating the holding rotation unit 102 with a drive signal from the holding rotation driving unit 210, the direction of luminance change changes. It is possible to detect which direction the part 101 is inclined.

  In addition, when the optical system is tilted, a brightness gradient in a specific direction is generated in the image regardless of the rotation direction or the moving speed of the holding unit 101. Therefore, a result of imaging while changing a plurality of driving conditions of the holding unit 101 From this, it is possible to infer abnormality of the optical system.

  In addition, as an abnormality that occurs in the illumination unit 104, a position shift of the entire illumination unit 104, a lamp deterioration, a lamp misalignment, and the like can be considered. When the abnormality is a lamp position shift, a luminance gradient occurs in the image regardless of the conditions of the holding unit 101, as in the case where the abnormality is an inclination of the optical system. In the present embodiment, if the apparatus has a plurality of illuminations (not shown), the abnormality in illumination can be detected by the occurrence of a luminance change in specific illumination, even though there is no change in luminance in other illuminations. .

  When the abnormality is lamp deterioration, the luminance is lowered over the entire image, and the luminance histogram is shifted to the lower luminance side as a whole. Therefore, the deterioration of the lamp can be detected by detecting the shift of the histogram to the low luminance side. In addition, lamp misalignment is a problem that occurs when replacing the lamp, and the lamp misalignment is detected by detecting that the brightness uniformity does not satisfy certain conditions for each area of the image when the lamp is replaced. It becomes possible to do.

  As described above, in this embodiment, the luminance distribution in the reference image information is compared with the luminance in the comparison target image information, and whether or not the luminance in the comparison target image information is included in the luminance distribution in the reference image information. Is determined. Thereby, the various abnormalities described above can be detected.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. In the present embodiment, as shown in FIG. 16, a plurality of reflecting portions 1601 to 1603, which are rotated with the trace direction of the imaging unit 108 as a rotation axis so as to have different reflection angles, are gradually changed in the vicinity of the holding unit 101. Has been placed. These reflection units 1601 to 1603 serve as reference subjects for detecting whether or not the apparatus itself is abnormal.

  The reflection units 1601 to 1603 are continuously arranged on the line along the trace direction (signal reading direction of the image sensor) by the imaging unit 108. The reflection units 1601 to 1603 are mechanically connected to the holding unit 101 and are driven in accordance with the driving operation of the holding unit 101. Note that the holding unit 101 can be stopped even during the driving operation.

  The imaging unit 108 includes a light condensing unit having an optical system capable of condensing reflected light from the reflecting units 1601 to 1603 and a line sensor camera capable of tracing one line. The configuration of the image processing unit 109 according to the present embodiment is the same as that in FIG. 14, but the image generation unit 202 generates image information for one line based on an electrical signal output from the line sensor camera of the imaging unit 108. (See FIG. 16).

  The luminance detection unit 214 detects the luminance in the image information for one line and generates luminance information (luminance line profile) including the luminance for one line. In order to remove the influence of noise, the image generation unit 202 continuously captures electric signals for a plurality of lines to generate image information for a plurality of lines, and the luminance detection unit 214 performs luminance in the image information for the plurality of lines. May be detected and averaged to generate luminance information for one line.

  The defect extraction unit 205 determines whether there is an abnormality in the apparatus based on the luminance information obtained from the reference image information and the luminance information obtained from the comparison target image information. The determination result by the defect extraction unit 205 is stored in the storage unit 207 as inspection result information separately for normal and abnormal.

  Next, a self-diagnosis method in this embodiment will be described. This processing procedure is the same as in FIG. First, a data creation process (step S11) is performed. The holding unit 101 is driven by the holding driving unit 211 that has received an instruction from the apparatus control unit 201, and the holding unit 101 moves to the irradiation position of the illumination light. Then, the angle of any of the illumination unit 104, the condensing lens 106, and the imaging unit 108 is adjusted so that the reflected light from the reflection unit 1601 enters the line sensor camera of the imaging unit 108.

  Then, the image generation unit 202 captures one line of electrical signals traced by the line sensor camera of the imaging unit 108, and generates image information (reference image information). The luminance detection unit 214 generates luminance information from the reference image information. Since imaging is performed using a line sensor camera, a pixel on which reflected light is incident can be specified for each reflection unit. In the storage unit 207, luminance information of a portion corresponding to the reflection unit 1601 is stored in the storage unit 207 as a history.

  The defect extraction unit 205 recognizes the defect as a defect when a defect extraction parameter used when extracting the defect by comparing the reference image information and the comparison target image information, that is, when a difference in luminance exceeding a predetermined value occurs. Set a threshold for this. This threshold value is stored in the storage unit 207 as a defect extraction parameter. Also for the reflection units 1602 and 1603, luminance information is generated in the same manner as described above, and the luminance information of portions corresponding to the respective reflection units is stored in the storage unit 207.

  Subsequently, in the processing step (step S12), the image generation unit 202 captures again the electrical signal for one line traced by the line sensor camera of the imaging unit 108, and generates image information (comparison target image information). The luminance detection unit 214 generates luminance information from the comparison target image information and outputs the luminance information to the defect extraction unit 205.

  Subsequently, in the defect extraction step (step S13), the defect extraction unit 205 receives the luminance information and defect extraction parameters stored in the storage unit 207 from the apparatus control unit 201, and the luminance information stored in the storage unit 207. Are compared with the newly generated luminance information. That is, the defect extraction unit 205 calculates a difference in luminance value for each pixel of each luminance information, and when the difference is larger than a predetermined threshold indicated by the defect extraction parameter, the defect extraction unit 205 collects the holding unit 101, the illumination unit 104, and the collection unit. It is determined that an abnormality has occurred in the angular relationship between the optical lens 106 and the imaging unit 108. The result of determination by the defect extraction unit 205 is stored in the storage unit 207 as a history.

  Subsequently, in the determination step (step S14), the defect determination unit 206 determines whether the apparatus is normal or abnormal based on the determination result by the defect extraction unit 205. As a result of the determination, if the apparatus is abnormal, the defect determination unit 206 sends a warning command to the display unit 212 via the apparatus control unit 201 in the display step (step S15). The display unit 212 displays a warning message based on the warning command. According to this embodiment, it is possible to detect an abnormality of a mechanism for changing the imaging angle.

  In the present embodiment, the reference object has three types of reflection angles by making the reflection angles of the three reflecting portions different from each other. However, the reference subject has more reflection angles. It is possible. The reflective portion 1701 shown in FIG. 17A has three surfaces around the longitudinal axis, and is configured such that the angle of each surface with respect to the reference surface changes according to the position in the longitudinal direction (FIG. 17). 17 (b)). As a result, the reflected light can be detected for all the rotatable angles of the illuminating unit 104, and the intensity of the reflected light with respect to the rotating angle can be detected as position information. It becomes possible to do.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described. In the present embodiment, a plurality of reflecting portions 1801 to 1803 that are formed so as to have different wavelengths of reflected light as shown in FIG. These reflection units 1801 to 1803 serve as a reference subject for detecting whether there is an abnormality in the apparatus itself. In the filter unit 107 of FIG. 1, in order to generate luminance information for each reflection unit, a bandpass filter (not shown) (hereinafter referred to as a BP filter) that can be replaced corresponding to the reflected light wavelength of each reflection unit. Are arranged). The configuration of the image processing unit 109 according to this embodiment is the same as that shown in FIG.

  Hereinafter, a self-diagnosis method in this embodiment will be described. This processing procedure is the same as in FIG. First, a data creation process (step S11) is performed. The holding unit 101 is driven by the holding driving unit 211 that has received an instruction from the apparatus control unit 201, and the holding unit 101 moves to the irradiation position of the illumination light. Then, the angle of any of the illumination unit 104, the condenser lens 106, and the imaging unit 108 is adjusted so that the reflected light from the reflection unit 1801 enters the line sensor camera of the imaging unit 108. Subsequently, by setting the filter unit 107 to a predetermined BP filter, luminance information is generated only in the reflection unit corresponding to the predetermined BP filter among the reflection units, and stored in the storage unit 207. Then, by sequentially rotating the BP filter, information when bright brightness is obtained at the reflecting portion corresponding to each BP filter is stored.

  Subsequently, in the processing step (step S12), the image generation unit 202 captures again the electrical signal for one line traced by the line sensor camera of the imaging unit 108, and generates image information (comparison target image information). The luminance detection unit 214 generates luminance information from the comparison target image information and outputs the luminance information to the defect extraction unit 205.

  Subsequently, in the defect extraction step (step S13), the defect extraction unit 205 receives the luminance information and defect extraction parameters stored in the storage unit 207 from the apparatus control unit 201, and the luminance information stored in the storage unit 207. Are compared with the newly generated luminance information. That is, the defect extraction unit 205 calculates a difference in luminance value for each pixel of each luminance information, and determines that an abnormality has occurred in the BP filter if the difference is larger than a predetermined threshold indicated by the defect extraction parameter. To do. The result of determination by the defect extraction unit 205 is stored in the storage unit 207 as a history. Subsequent steps are the same as those in the fifth embodiment. According to this embodiment, it is possible to detect an abnormality in the BP filter and an abnormality in its operation mechanism.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and includes design changes and the like without departing from the gist of the present invention. . For example, in the first embodiment, two types of regions having different surface states are formed in the holding unit 101. However, as in the fourth embodiment, a bare wafer is used as a reference subject, and the surface thereof is used. The above two types of regions may be formed. Further, the shape of the special region formed on the surface of the reference subject is not limited to the shape shown in FIG. 3, and may be other shapes.

  In addition, a reflection part in which a plurality of regions having different surface states are formed may be arranged near the holding part 101 and used as a reference subject. Furthermore, as a result of the determination by the defect extraction unit 205, when it is determined that a defect has occurred, a warning message notifying the occurrence of an abnormality may be displayed on the display unit 212.

  Further, the defect inspection apparatus may be configured by appropriately combining the individual techniques included in the first to sixth embodiments.

It is a block diagram which shows the structure of the defect inspection apparatus by the 1st Embodiment of this invention. It is a block diagram which shows the structure of the whole control part with which the defect inspection apparatus by the 1st Embodiment of this invention is provided. It is a top view of the holding part with which the defect inspection apparatus by the 1st Embodiment of this invention is provided. It is a flowchart which shows the procedure of the process which the defect inspection apparatus by the 1st Embodiment of this invention performs. It is a reference drawing which shows the defect detected in the 1st Embodiment of this invention. It is a reference drawing which shows the defect detected in the 1st Embodiment of this invention. It is a reference drawing which shows the defect detected in the 1st Embodiment of this invention. It is a top view of the holding part with which the defect inspection apparatus by the 2nd Embodiment of this invention is provided. It is a flowchart which shows the procedure of the process which the defect inspection apparatus by the 2nd Embodiment of this invention performs. It is a top view of the holding part with which the defect inspection apparatus by the 3rd Embodiment of this invention is provided. It is a block diagram which shows the structure of the image process part with which the defect inspection apparatus by the 3rd Embodiment of this invention is provided. It is a flowchart which shows the procedure of the process which the defect inspection apparatus by the 3rd Embodiment of this invention performs. It is a flowchart which shows the procedure of the process which the defect inspection apparatus by the 3rd Embodiment of this invention performs. It is a block diagram which shows the structure of the image process part with which the defect inspection apparatus by the 4th Embodiment of this invention is provided. It is explanatory drawing for demonstrating the self-diagnosis method of the apparatus in the 4th Embodiment of this invention. It is explanatory drawing for demonstrating the structure of the reflection part with which the defect inspection apparatus by the 5th Embodiment of this invention is provided. It is explanatory drawing for demonstrating the other structural example of the reflection part with which the defect inspection apparatus by the 5th Embodiment of this invention is provided. It is explanatory drawing for demonstrating the structure of the reflection part with which the defect inspection apparatus by the 6th Embodiment of this invention is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Holding part (reference | standard subject), 102 ... Holding | maintenance rotation part, 103 ... Base part, 104 ... Illumination part, 105 ... Illumination condensing lens, 106 ... Condensing lens, DESCRIPTION OF SYMBOLS 107 ... Filter part, 108 ... Imaging part (imaging means), 109 ... Image processing part, 201 ... Apparatus control part, 202 ... Image generation part, 203 ... Position correction part, 204... Brightness correction unit 205 205 Defect extraction unit 206 Defect determination unit (determination unit) 207 Storage unit (storage unit) 208 Imaging control unit 209 Illumination control unit, 210: holding rotation driving unit, 211 ... holding driving unit, 212 ... display unit, 213 ... operation unit, 214 ... luminance detection unit, 215 ... resolution measurement Part

Claims (11)

In defect inspection equipment that performs defect inspection of inspection objects,
Imaging means for imaging a reference subject;
Storage means for storing reference information obtained by imaging the reference subject;
Determination means for determining presence / absence of abnormality of the device itself based on a result of comparing the reference information with comparison target information obtained by imaging the reference subject after obtaining the reference information;
A defect inspection apparatus comprising:   The defect inspection apparatus according to claim 1, further comprising a holding unit that holds the inspection object, wherein a surface of the holding unit is the reference subject.   The reference information and the comparison target information are image information of the reference subject, and the determination unit determines presence / absence of abnormality of the apparatus itself based on a difference between the comparison target information and the reference information. The defect inspection apparatus according to claim 1 or 2.   The surface state of the reference subject varies from region to region so that the surface of the reference subject has a plurality of regions, and the luminance in image information obtained by imaging the surface of the reference subject varies from region to region. The defect inspection apparatus according to claim 3.   4. The structure according to claim 3, wherein a plurality of structures serving as marks made of the specific structures are formed in a region where the plurality of specific structures are uniformly arranged on the surface of the reference subject. Defect inspection equipment.   The reference subject includes a plurality of regions formed so that luminance in image information is uniform, and the reference information and the comparison target information are in image information obtained by imaging the plurality of regions. The defect inspection apparatus according to claim 1, wherein the defect inspection apparatus has luminance.   The defect inspection apparatus according to claim 1, wherein the reference subject includes a resolution chart, and the reference information and the comparison target information are luminances in image information of the resolution chart.   The reference information is information indicating a luminance distribution in the image information of the reference subject, and the comparison target information is luminance information in the image information of the reference subject. 2. The defect inspection apparatus according to 2.   The reference subject includes a plurality of reflecting portions having different reflection angles, the reference information and the comparison target information are image information of the reference subject, and the determination unit includes the comparison target information and the reference information. 3. The defect inspection apparatus according to claim 1, wherein presence / absence of abnormality of the apparatus itself is determined based on a difference in luminance of the reflection unit.   The reference subject includes a plurality of reflecting portions having different reflected light wavelengths, the reference information and the comparison target information are image information of the reference subject, and the determination unit includes the comparison target information and the comparison target information. The defect inspection apparatus according to claim 1, wherein presence / absence of abnormality of the apparatus itself is determined based on a difference in luminance of the reflection unit in the reference information.   In a defect inspection method for inspecting a defect of an inspection object, based on a result of comparing the reference information with comparison target information obtained by imaging the reference subject after imaging the reference subject and acquiring reference information A defect inspection method characterized by determining whether there is an abnormality in the apparatus itself.

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