JP2009063365A - Inspection device and inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection device capable of easily extracting image data including the flaw of an inspection target from a large quantity of image data in a shorter time, and to provide an inspection method. <P>SOLUTION: This inspection device has an imaging camera 30 for respectively imaging a plurality of the ranges shifted in a predetermined direction of the inspection target, a compression processing part 42 for performing data compression processing at every image in a plurality of the images captured by the imaging camera 30 to form compression image data and an inspection part 44 for inspecting the presence of the flaw in the inspection target on the basis of the difference of the size of the compression image data. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection apparatus and an inspection method for inspecting an object such as a semiconductor wafer or a liquid crystal glass substrate for defects.

  In recent years, the degree of integration of circuit element patterns formed on semiconductor wafers has increased, and the types of thin films used for wafer surface treatment in semiconductor manufacturing processes have increased. Along with this, defect inspection near the edge of the wafer has become important. If there is a defect such as a foreign substance near the edge of the wafer, the foreign substance or the like will enter the surface side of the wafer in the subsequent process and adversely affect the yield of circuit elements produced from the wafer.

  Therefore, the periphery of the test object formed in a disk shape such as a semiconductor wafer (eg apex and upper and lower bevels) is observed from multiple directions to remove foreign matter and film, bubbles in the film, and wrap around the film. An inspection apparatus for inspecting the presence or absence of defects such as these has been devised (see, for example, Patent Document 1). Such an inspection apparatus has a configuration in which foreign matter or the like is detected by using scattered light generated by irradiation with laser light or the like, or a foreign object or the like is detected by forming an image of the test object in a belt shape with a line sensor. There are things of composition.

JP 2004-325389 A

  In addition, there is a configuration in which an image acquisition device partially acquires an image around the end face of a test object one by one and detects a defect such as a foreign object from a plurality of image data. When an image acquisition device having a resolution is used, the number of image acquisition (image data) becomes very large. For example, when the end face (apex) of a 12-inch wafer is observed with a 10 × objective lens, the number of image acquisition is It becomes about 1400 sheets. Extracting only image data including defects of the test object from such a large amount of image data is time consuming and difficult when checking all the images one by one.

  The present invention has been made in view of such a problem, and an inspection apparatus and an inspection method that can easily extract image data including defects of a test object from a large amount of image data in a shorter time. The purpose is to provide.

  In order to solve the above problems and achieve the object, an inspection apparatus according to the present invention includes an imaging unit that captures a plurality of ranges that are shifted in a predetermined direction in a test object, and a plurality of images that are captured by the imaging unit. A compression processing unit that performs data compression processing for each image and generates compressed image data, and an inspection unit that inspects the presence or absence of defects in the test object based on a difference in size of the compressed image data. Composed.

  In the inspection apparatus, it is preferable that the inspection unit extracts an image including the defect from the plurality of images based on a difference in size of the compressed image data.

  In the inspection apparatus, it is preferable that the inspection unit determines that the defect exists when the size of the compressed image data is larger than a predetermined threshold.

  In the inspection apparatus, it is preferable that the inspection unit estimates a defect amount of the defect by comparing the size of the compressed image data with a sample data size including predetermined defect information.

  The inspection apparatus preferably further includes a display unit that displays the inspection result of the inspection unit.

  In the inspection apparatus, the rotation drive is performed so that the outer peripheral end of the test object and the imaging unit are relatively moved in the predetermined direction with the rotational symmetry axis of the test object formed in a substantially disc shape as a rotation axis. It is preferable that the image capturing unit continuously captures an image of an outer peripheral end portion or the vicinity of the outer peripheral end portion of the test object from a direction orthogonal to the rotation axis.

  Further, the inspection method according to the present invention includes an imaging process for imaging a plurality of ranges shifted in a predetermined direction in the test object, and a data compression process for each image in the plurality of images captured by the imaging process for compression. A compression processing step for generating image data; and an inspection step for inspecting the presence or absence of defects in the test object based on a difference in size of the compressed image data.

  In the inspection method, it is preferable that in the inspection step, an image including the defect is extracted from the plurality of images based on a difference in size of the compressed image data.

  In the inspection method, it is preferable to determine that the defect is present when the size of the compressed image data is larger than a predetermined threshold in the inspection step.

  In the inspection method, it is preferable that the defect amount of the defect is estimated in the inspection step by comparing the size of the compressed image data with a sample data size including predetermined defect information.

  ADVANTAGE OF THE INVENTION According to this invention, the image containing the defect of a test object can be easily extracted in a short time from the some image which imaged the test object.

  Hereinafter, preferred embodiments of the present invention will be described. An example of an inspection apparatus according to the present invention is shown in FIG. 1, and the inspection apparatus 1 has defects (scratches, adhesion of foreign matter, etc.) at and near the end of a semiconductor wafer 10 (hereinafter referred to as wafer 10). This is to check for the presence or absence.

  The wafer 10 as a test object is formed in a thin disk shape, and a circuit pattern (not shown) corresponding to a plurality of semiconductor chips (chip regions) taken out from the wafer 10 is formed on the surface thereof. A thin film (not shown) such as an insulating film, an electrode wiring film, and a semiconductor film is formed in multiple layers. As shown in FIG. 2, an upper bevel portion 11 is formed in a ring shape inside the outer peripheral end portion on the surface (upper surface) of the wafer 10, and a circuit pattern is formed inside the upper bevel portion 11. . Further, a lower bevel portion 12 is formed symmetrically with the upper bevel portion 11 with respect to the wafer 10 on the inner side of the outer peripheral end portion on the back surface (lower surface) of the wafer 10. The wafer end face connected to the upper bevel portion 11 and the lower bevel portion 12 becomes the apex portion 13.

  The inspection apparatus 1 includes a wafer support unit 20 that supports and rotates the wafer 10, an imaging camera 30 that captures the outer peripheral end of the wafer 10 and the vicinity of the outer peripheral end, and an image of the wafer 10 captured by the imaging camera 30. On the other hand, the image processing unit 40 that performs predetermined image processing and the control unit 50 that performs drive control of the wafer support unit 20 and the imaging camera 30 are mainly configured.

  The wafer support unit 20 supports the wafer 10 on the upper surface side by being attached substantially horizontally to the base 21, the rotary shaft 22 provided vertically extending from the base 21, and the upper end of the rotary shaft 22. And a wafer holder 23. A vacuum suction mechanism (not shown) is provided inside the wafer holder 23, and the wafer 10 on the wafer holder 23 is suction-held using vacuum suction by the vacuum suction mechanism.

  A rotation drive mechanism (not shown) that rotates the rotation shaft 22 is provided inside the base 21, and the wafer holder attached to the rotation shaft 22 by rotating the rotation shaft 22 by the rotation drive mechanism. 23, the wafer 10 sucked and held on the wafer holder 23 is rotationally driven with the center (rotation symmetry axis O) of the wafer 10 as the rotation axis. The wafer holder 23 is formed in a substantially disk shape having a diameter smaller than that of the wafer 10, and includes an upper bevel portion 11, a lower bevel portion 12, and an apex portion 13 with the wafer 10 being sucked and held on the wafer holder 23. The vicinity of the outer peripheral end of the wafer 10 protrudes from the wafer holder 23.

  The imaging camera 30 is mainly composed of a lens barrel portion 31 having an enlarged photographing optical system and epi-illumination (not shown) and a camera body 33 having an image sensor 32 built therein, and illumination light by epi-illumination is magnified. The wafer 10 is illuminated via the optical system, and the reflected light from the wafer 10 is guided to the image sensor 32 via the magnification imaging optical system, and the image sensor 32 performs a two-dimensional image (two-dimensional image). Data) is detected. With such a configuration, a bright field image at or near the outer peripheral edge of the wafer 10 is obtained.

  The imaging camera 30 is disposed so as to face the apex portion 13 of the wafer 10 and images the apex portion 13 from a direction orthogonal to the rotation axis (rotation symmetry axis O) of the wafer 10. As a result, when the wafer 10 supported by the wafer support unit 20 is rotated, the outer peripheral portion of the wafer, that is, the apex portion 13 is relatively moved in the circumferential direction, so that the imaging camera 30 disposed so as to face the apex portion 13. Can continuously (multiple) image the apex portion 13 in the circumferential direction, and can image the apex portion 13 over the entire circumference of the wafer 10. Note that the image data captured by the imaging camera 30 is output to the image processing unit 40.

  The inspection apparatus 1 is provided with a moving device (not shown), and as shown in FIG. 2, the position where the imaging camera 30 faces the upper bevel portion 11 of the wafer 10 by the moving device (position indicated by a one-dot chain line). The position can be moved to a position facing the lower bevel portion 12 (position indicated by a two-dot chain line) or a position facing the apex portion 13 (position indicated by a solid line). As a result, the imaging camera 30 can continuously (multiple) image the upper and lower bevel portions 11 and 12 in the circumferential direction, similarly to the apex portion 13 of the wafer 10. It becomes possible to image the bevel portions 11 and 12, respectively. As described above, in this embodiment, the moving device is provided and the upper and lower bevel portions 11 and 12 and the apex portion 13 are respectively imaged. However, the present invention is not limited thereto, and the upper bevel portion 11 and the lower bevel portion of the wafer 10 are not limited thereto. 12 or three imaging cameras 30 may be provided at positions facing the apex 13. Furthermore, a tilt mechanism or the like may be provided in the wafer support unit 20 so that the upper bevel portion 11, the lower bevel portion 12, and the apex portion 13 of the wafer 10 can be imaged.

  The control unit 50 includes a control board that performs various controls, and performs operation control of the wafer support unit 20, the imaging camera 30, the image processing unit 40, and the like according to control signals from the control unit 50. The control unit 50 includes an input unit for inputting inspection parameters (threshold used for defect detection, etc.), an interface unit 51 having an image display unit, a storage unit 52 for storing image data, and the like. Are electrically connected.

  The image processing unit 40 includes a circuit board (not shown) and the like, and includes an input unit 41, a compression processing unit 42, an internal memory 43, an inspection unit 44, and an output unit 45, as shown in FIG. ing. Image data from the imaging camera 30 is input to the input unit 41, and further, inspection parameters and the like input by the interface unit 51 are input via the control unit 50.

  The compression processing unit 42 is electrically connected to the input unit 41, performs predetermined compression encoding processing to be described later on the image data from the imaging camera 30 input from the input unit 41, and the processing result (compression Data) to the internal memory 43 and the output unit 45. The inspection unit 44 is electrically connected to the internal memory 43, and an inspection process for inspecting whether there is a defect in the wafer 10 based on the difference in the data size of the compressed data by the compression processing unit 42 stored in the internal memory 43. And the processing result is output to the output unit 45. The output unit 45 is electrically connected to the control unit 50, and outputs image data of the wafer 10, an inspection processing result by the inspection unit 44, and the like to the control unit 50.

  An inspection method in the apex portion 13 of the wafer 10 using the inspection apparatus 1 configured as described above will be described below with reference to the flowchart of FIG. In addition, since each inspection method in the upper and lower bevel portions 11 and 12 of the wafer 10 is the same as the inspection method in the apex portion 13 described later, the description thereof is omitted.

  First, in step S1, an imaging step of imaging the apex portion 13 of the wafer 10 is performed. In this imaging step, the wafer 10 is placed at a predetermined position on the wafer holder 23, and the wafer 10 is sucked and held on the wafer holder 23 by a vacuum suction mechanism built in the wafer holder 23. When the wafer 10 is held on the wafer holder 23, the imaging camera 30 is moved to a position facing the apex portion 13 of the wafer 10 by a control signal from the control unit 50, and the rotation axis of the wafer 10 (rotation symmetry axis O) and The apex portion 13 is imaged from the direction that is orthogonal.

  Further, the rotation driving mechanism of the wafer support unit 20 is driven to rotate by a control signal from the control unit 50, and the wafer 10 is at a predetermined angle (an angle corresponding to polar coordinates with the center of the wafer 10 as the origin and substantially corresponds to the imaging range. Rotate only the angle. Then, each time the wafer 10 is rotated by a predetermined angle, the apex portion 13 of the wafer 10 is imaged by the imaging camera 30. Accordingly, the imaging camera 30 continuously (multiple) images the apex portion 13 in the circumferential direction, and images the apex portion 13 over the entire circumference of the wafer 10. When the imaging camera 30 continuously (multiple) images the apex unit 13, image data continuously detected by the image sensor 32 is output to the image processing unit 40 and input to the input unit 41 of the image processing unit 40. The image data is sent to the compression processing unit 42.

  Here, the image data of the apex portion 13 imaged over the entire circumference of the wafer 10 becomes a very large amount of image data (number of acquired images), and all the image data is checked one by one to determine the presence or absence of defects. Is time consuming and difficult. Therefore, as will be described later, the image data of the apex unit 13 including a defect is extracted by the image processing unit 40 (the compression processing unit 42 and the inspection unit 44).

  Next, in step S2, a compression processing step of applying predetermined compression coding to the image data of the apex unit 13 is performed. When the image data of the apex unit 13 from the imaging camera 30 is input from the input unit 41 to the compression processing unit 42, for example, for each image data of the apex unit 13 captured at every predetermined angle, for example, a known JPEG Compression processing is performed to generate compressed image data for each image data of the apex unit 13, and the generated compressed image data is output to the internal memory 43 and the output unit 45. The compressed image data output to the output unit 45 is sent to the storage unit 52 via the control unit 50 and stored in the storage unit 52.

  When the image data input from the input unit 41 to the compression processing unit 42 images the apex unit 13 in a non-defective state (not including defects), the luminance value changes between pixels because the surface of the apex unit 13 is smooth. The image data has a small amount (change in light amount). On the other hand, when the apex portion 13 including a defect is imaged, the surface of the apex portion 13 has unevenness due to a defect such as a foreign substance, and thus image data having a large change in luminance value between pixels is obtained. For example, the image data of the apex part 13 in a non-defective state (hereinafter referred to as normal part image data) is “000000000011”, and the image data of the apex part 13 including a defect (hereinafter referred to as defective part image data) is “040631824246”. In this way, it has a sequence of numbers arbitrarily assigned to the amount of change in luminance value. Therefore, when processing (compression processing) for eliminating redundancy of image data such as “000000000011” (normal part image data) “0 × 10, 1 × 2” (normal part compressed data) is performed, the normal part The data size of the image data is compressed very small. On the other hand, when the defective portion image data is compressed as described above, “0 × 2, 1, 2 × 2, 3, 4 × 3, 6 × 2, 8” (defective portion compressed data) is obtained. The data size of the partial image data is not compressed so much.

  The apex portion 13 has a smooth and substantially uniform shape in the circumferential direction of the wafer 10 (can be regarded as uniform if there is no defect), that is, the apex portion 13 is continuously arranged in the circumferential direction by the imaging camera 30. Specifically, the (multiple) captured image data is uniform image data other than defect information. Therefore, when compression processing is performed on each image data as described above, a difference occurs in the data size of each compressed data based only on the presence or absence of defects in the apex portion 13, and the defective portion compressed data is the data size of the normal portion compressed data. Bigger than.

  The compressed data compressed by the compression processing unit 42 for each image data of the apex unit 13 over the entire circumference of the wafer 10 is stored (sorted) in the internal memory 42 in the order of the data size of the compressed data. The internal memory 42 also stores in advance sample compression data including predetermined defect information (a defect amount of defects in the apex portion 13 is known).

  When the compression processing unit 42 generates the compressed data of the apex unit 13 for each predetermined angle over the entire circumference of the wafer 10, in step S3, an inspection process for inspecting whether there is a defect in the apex unit 13 of the wafer 10 is performed. This inspection process is performed by the inspection unit 44 on a plurality of compressed data stored in the internal memory 43. The inspection unit 44 determines whether or not the data size of each compressed data in the apex unit 13 is larger than a predetermined threshold value stored in advance in the internal memory 43. If any data size of the compressed data of the apex portion 13 is smaller than the predetermined threshold, it is determined that the apex portion 13 of the wafer 10 imaged by the imaging camera 30 is not defective. On the other hand, if any data size of the compressed data of the apex unit 13 is larger than a predetermined threshold value, it is determined that the apex unit 13 is defective, and compressed data having a data size larger than the threshold value from a plurality of compressed data items. (Defect compression data) is extracted.

  The inspection unit 44 determines whether or not the data size of each compressed data in the apex unit 13 is larger than a predetermined threshold, and determines the data size between the compressed data and the sample compressed data stored in the internal memory 43 in advance. By comparing, the information amount of defect information included in the compressed data (defective portion compressed data), that is, the defect amount of defects in the apex portion 13 is estimated.

  The threshold value used in the inspection process is set empirically such as a value larger than the average when comparing sizes in the same type of wafer data, and is input from the interface unit 51 to control the control unit 50 and the input unit 41. To the internal memory 43. The inspection unit 44 outputs the inspection result of such an inspection process to the output unit 45, and the inspection result data output to the output unit 45 is sent to the storage unit 52 via the control unit 50 and stored therein. Stored in the unit 52.

  In step S4, based on the comparison result of the data size by the inspection unit 44 stored in the storage unit 52 by the control unit 50 and the defective portion compressed data extracted when it is determined that the apex unit 13 has a defect. A display step of displaying the inspection result such as the defect image on the image display unit of the interface unit 51 is performed. When the defective part compressed data is output from the storage unit 52 via the control unit 50, the interface unit 51 performs a decompression process on the defective part compressed data, and the decompressed defect part image (defective part image data) is displayed as an image. Displayed in the section.

  As described above, according to the inspection apparatus 1 and the inspection method according to the present embodiment, the wafer 10 (the apex portion 13 or the upper and lower bevel portions 11 and 12) is shifted every predetermined range (every predetermined angle) shifted in the circumferential direction. A compression processing unit 42 that performs predetermined compression encoding on each captured image data, and the presence / absence of a defect in the wafer 10 based on a difference in data size of each compression data generated by the compression processing unit 42 Since it is not necessary to visually observe the images of the wafers one by one because the inspection process is performed, the inspection of the wafer 10 (extraction of images including defects) can be easily performed in a shorter time. it can.

  Further, when the data size of each compressed data generated by the compression processing unit 42 is larger than a predetermined threshold value stored in advance in the internal memory 43, it is determined that the wafer 10 has a defect, thereby inspecting the wafer 10 ( Extraction of an image including a defect) can be performed automatically. As a result, it is possible to observe only an image including a defect on the image display unit of the interface unit 51 as necessary.

  Further, it is determined whether or not the data size of each compressed data generated by the compression processing unit 42 is larger than a predetermined threshold, and includes each compressed data and predetermined defect information stored in advance in the internal memory 43 (wafer) The defect amount of the wafer 10 and the defect amount of the defect are automatically determined by comparing the data size with the sample compression data and estimating the defect amount of the defect of the wafer 10. Can be detected.

  Further, as described above, the wafer 10 is rotationally driven by the wafer support unit 20, and the imaging camera 30 circulates the apex portion 13 or the upper and lower bevel portions 11 and 12 of the wafer 10 from the direction orthogonal to the rotation axis of the wafer 10. By continuously imaging in the direction, the apex portion 13 or the upper and lower bevel portions 11 and 12 of the wafer 10 can be imaged at high speed.

  In the embodiment described above, the apex portion 13 and the like are imaged over the entire circumference of the wafer 10, but the present invention is not limited to this, and a desired angular position in the apex portion 13 and the like is controlled by the operation control of the control unit 50. You may make it image only about a range. Thereby, the presence or absence of a defect can be inspected only in a desired angular position range in the apex portion 13 or the like. Further, such inspection is not limited to the outer peripheral end portion of the wafer 10 or the vicinity of the outer peripheral end portion, and for example, it is possible to inspect a glass substrate or the like, and particularly to a test object whose surface form is substantially uniform. It is effective to apply this embodiment to this.

  Further, in the above-described embodiment, an amplification type two-dimensional solid-state imaging device such as a CCD or CMOS can be used as an image sensor of the imaging camera 30, and a one-dimensional sensor such as a line sensor can also be used. In the case of using a one-dimensional sensor, if the image signal obtained while moving the wafer 10 by a predetermined angle is converted into a single image and then subjected to compression processing, the same processing as in the case of using the two-dimensional sensor can be performed thereafter. . Moreover, although the bright field image was imaged in this embodiment, it is applicable also to a dark field image.

It is a schematic block diagram of the inspection apparatus which concerns on this invention. It is a side view which shows the outer periphery edge part vicinity of the wafer which is a test object. It is a control block diagram which shows the image process part which comprises the said test | inspection apparatus. It is a flowchart which shows the inspection method which concerns on this invention.

Explanation of symbols

1 Inspection device 10 Wafer (test object)
20 Wafer support part (relative movement part)
30 Imaging camera (imaging part)
40 Image processing unit 42 Compression processing unit 44 Inspection unit 50 Control unit 51 Interface unit (display unit)

Claims (10)

An imaging unit that images each of a plurality of ranges shifted in a predetermined direction in the test object;
A compression processing unit that performs data compression processing for each image in a plurality of images captured by the imaging unit and generates compressed image data;
An inspection apparatus comprising: an inspection unit that inspects the presence or absence of a defect in the object based on a difference in size of the compressed image data.   The inspection apparatus according to claim 1, wherein the inspection unit extracts an image including the defect from the plurality of images based on a difference in size of the compressed image data.   The inspection apparatus according to claim 1, wherein the inspection unit determines that the defect is present when a size of the compressed image data is larger than a predetermined threshold.   4. The inspection unit according to claim 1, wherein the inspection unit estimates a defect amount of the defect by comparing the size of the compressed image data with a sample data size including predetermined defect information. The inspection apparatus according to one item.   The inspection apparatus according to claim 1, further comprising a display unit that displays an inspection result by the inspection unit. A relative movement unit that rotationally drives the outer peripheral end of the test object and the imaging unit so as to move relative to each other in the predetermined direction with a rotational symmetry axis of the test object formed in a substantially disc shape as a rotation axis. In addition,
The said imaging part continuously images the outer peripheral edge part of the said test object, or an outer peripheral edge part from the direction orthogonal to the said rotating shaft, The any one of Claims 1-5 characterized by the above-mentioned. The inspection device described in 1. An imaging step of imaging each of a plurality of ranges shifted in a predetermined direction in the test object;
A compression processing step for generating compressed image data by performing data compression processing for each image in a plurality of images captured by the imaging step;
And an inspection step of inspecting the presence or absence of a defect in the object based on a difference in size of the compressed image data.   8. The inspection method according to claim 7, wherein, in the inspection step, an image including the defect is extracted from the plurality of images based on a difference in size of the compressed image data.   9. The inspection method according to claim 7, wherein in the inspection step, it is determined that the defect exists when the size of the compressed image data is larger than a predetermined threshold value.   The defect amount of the defect is estimated by comparing the size of the compressed image data with a sample data size including predetermined defect information in the inspection step. The inspection method according to one item.

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