JP4220061B2 - Periodic pattern defect inspection method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a work having a periodic pattern in which processed portions formed on a base material are periodically and repeatedly arranged, or an arrangement pitch when a processed portion formed on a base material is provided. The invention relates to a periodic pattern inspection method and apparatus for inspecting a workpiece having a pattern that gradually changes from the center of the workpiece toward the outside.
[0002]
[Prior art]
Conventionally, various inspection methods and apparatuses have been proposed in which a periodic pattern such as a shadow mask is photographed with a CCD camera, image processing is performed based on the photographed image, and a defect of a workpiece to be inspected is detected.
However, when a periodic pattern such as a shadow mask is photographed with a CCD camera, moire is caused by interference between the pixel pitch of the CCD sensor and the pitch of the processed part of the workpiece to be inspected (in the case of a shadow mask, the pitch of the hole). This moire has caused a problem that the detection accuracy is lowered during the periodic pattern inspection.
[0003]
In recent years, there has been a strong demand for higher accuracy in defect detection as the quality required from customers required for shadow masks increases.
[0004]
[Problems to be solved by the invention]
The present invention is a moiré caused by interference between the pixel pitch of a CCD sensor arranged in a CCD camera, which is an imaging means, and the pitch of a workpiece processing part to be inspected (in the case of a shadow mask, the pitch of a hole). An object of the present invention is to provide a pattern defect inspection method and apparatus that realizes highly sensitive defect detection without reducing the detection sensitivity.
[0005]
[Means for Solving the Problems]
In the defect inspection method for a pattern according to the present invention, a workpiece having a periodic pattern in which processed portions formed on a substrate are periodically and repeatedly disposed, or a processed portion formed on a substrate is disposed. A pattern defect inspection method for inspecting a workpiece having a pattern that gradually changes as the arrangement pitch of the time goes from the center of the workpiece to the outside, the step of photographing so as to resolve the processed portion, and A step of recording a multi-valued image obtained by photographing in a memory, a step of binarizing the recorded multi-valued image at a predetermined slice level, and the binarized data subjected to the binarization processing The process of performing a labeling process, which is a process for sequentially numbering connected regions on a binary image, and the addresses of pixels constituting the same label are obtained based on the label result obtained by the labeling process. A step of calculating a pixel value of the recorded multi-valued image corresponding to the address, a step of developing a representative value based on the calculation result on a memory, and the developed representative value And a step of performing a differentiation process, and a step of extracting a defect by comparing the result of the differentiation process with a slice level.
[0006]
In the calculation processing step, it is further preferable that the calculation processing step adds the pixel values of the multi-value images corresponding to the pixel addresses constituting the same label to calculate the sum for each label.
[0007]
In the step of performing the arithmetic processing, it is more desirable to calculate the sum of the pixel values of the multi-valued image corresponding to the contour address of the processing portion among the pixel values of the multi-valued image corresponding to the pixel address constituting the same label. .
[0008]
The pattern defect inspection apparatus according to the present invention arranges a workpiece having a periodic pattern in which processing parts formed on a base material are periodically repeated, or a processing part formed on a base material. A defect inspection apparatus for a pattern that inspects a workpiece having a pattern that gradually changes as the arrangement pitch of the time goes from the center of the workpiece to the outside, and an imaging unit that performs imaging so as to resolve the processing unit; A first memory for recording a multi-valued image obtained by the photographing, a binarization processing unit for binarizing the multi-valued image recorded in the first memory at a predetermined slice level, and the 2 A second memory for recording the binarized data obtained by the binarization processing unit, and a process for sequentially numbering connected areas on the binary image based on the binarized data recorded in the second memory performing the labeling process is Based on the labeling processing unit and the label result obtained by the labeling processing unit, the address of the pixel constituting the same label is obtained, and the pixel value of the multi-value image corresponding to the address is arithmetically processed to obtain a representative value. An arithmetic processing unit, a third memory that expands a representative value based on the result of the arithmetic processing in a memory, a differential processing unit that performs a differential process on the representative value expanded in the memory, and a result of the differential processing And a defect discriminating unit for extracting a defect by comparing with a slice level.
[0009]
It is further desirable that the arithmetic processing unit calculates the sum for each label by adding each pixel value of the multi-valued image corresponding to the pixel address constituting the same label.
[0010]
More preferably, the arithmetic processing unit calculates the sum of the pixel values of the multi-valued image corresponding to the contour address of the processing unit among the pixel values of the multi-valued image corresponding to the pixel address constituting the same label.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a case where a shadow mask is used as the periodic pattern will be described.
[0012]
First, the entire apparatus will be described. FIG. 4 is a diagram for explaining the overall configuration of the periodic pattern defect inspection apparatus according to the embodiment of the present invention. This is an inspection apparatus that uses a shadow mask as an inspection target and performs transmission illumination.
[0013]
In FIG. 4, the shadow mask 44 to be inspected is placed on the transfer device 43, and the transfer control controller 46 moves the transfer device 43 in the direction of the arrow. Then, the transfer device 43 on which the shadow mask 44 is placed is passed under the CCD line sensor camera 41. At that time, the shadow mask 44 is illuminated from below the transport device 43 by the linear light source 42, and the transmitted light that passes through the hole of the shadow mask 44 placed on the transport device 43 is photographed by the CCD line sensor camera 41. To do.
Of course, the transport device is structured to illuminate the shadow mask 44 placed on the device through the light of the linear light source.
[0014]
The image processing apparatus 45 performs image processing on a signal based on the light transmitted through the hole of the shadow mask 44 obtained by the imaging, and performs defect inspection. The inspection result is displayed on the man-machine interface 47. In this embodiment, the man-machine interface 47 also serves as a transport control device.
[0015]
In the apparatus according to the embodiment of the present invention, a transmission image is used as an image captured by the CCD line sensor camera, but the captured image may be a transmission image or a reflection image.
[0016]
That is, an image obtained by photographing a pattern is obtained by arranging a photographing unit such as a CCD camera on one side of a work such as a shadow mask and arranging an irradiation light source on the other side. May be a transmission image of a processed part (a hole in a shadow mask) formed on a workpiece such as a shadow mask. Further, a reflection image in which a CCD camera or the like is arranged on one side with respect to a work such as a shadow mask, an irradiation light source is arranged on the same side, and the irradiated light is reflected by the work such as a shadow mask or the like.
[0017]
Next, the inspection method of the present invention implemented by the image processing unit of the inspection apparatus shown in FIG. 4 will be described with reference to FIG. FIG. 1 used here is a diagram for explaining a pattern defect inspection method according to an embodiment of the present invention.
[0018]
The inspection method shown in FIG. 1 will be described.
In step 1 (S1), the shadow mask to be inspected is photographed with a CCD camera at a resolution sufficient to resolve the hole as a processing part. In this embodiment, one hole is imaged so that the sensor pixels of the CCD line sensor camera correspond to 25 pixels of 5 × 5. Of course, it is not limited to this. However, if it is roughly 4 pixels (2 × 2) or about 1 pixel, moire is generated and high-precision inspection cannot be performed. On the other hand, if the number of pixels is too large, it takes a long time for image processing such as inspection when the number of pixels per hole is 10,000 or more, so that highly accurate inspection can be performed, but it is not practical.
[0019]
In step 2 (S2), the multi-valued image obtained by the photographing is recorded in the first image memory.
In step 3 (S3), binarization processing is performed at a predetermined slice level at which the multi-valued image can be set as necessary. Here, the image is recorded in a second image memory different from the first image memory in S2. However, these multi-value image data and binary image data need only be stored so as not to lose multi-value image data to be used later. In addition, the binarized area changes around the outline of the hole depending on the slice level to be set. This slice level is obtained in advance by a test.
[0020]
In step 4 (S4), a labeling process is performed based on the binarized data subjected to the binarization process. The labeling process refers to a process for sequentially numbering connected areas on a binary image. The number is stored in the memory as image data. The processing result is called a label image.
In step 5 (S5), an address of a pixel having the same label is obtained based on the processing result (herein referred to as a label result) indicated in the label image obtained by the labeling process.
[0021]
In step 6 (S6), the pixel value of the multi-value image corresponding to the address is processed. Specifically, there are two types here, which will be described below.
[0022]
In the first calculation process, the calculation process of S6 adds the pixel values of the multi-valued image corresponding to the address to calculate a sum for each label, and uses the sum as a representative value of the hole portion of the shadow mask. Decide. However, an average value obtained from the sum may be used as a representative value.
[0023]
In the second calculation process, the calculation process of S6 adds the pixel values of the multi-valued image corresponding to the address to calculate the sum of the contours of the shadow mask holes, and based on the sum, the shadow mask It is determined as the representative value of the hole. Of course, an average value obtained from the sum of the contours of the holes may be used as a representative value.
[0024]
In step 7 (S7), the representative value based on the calculation result is developed two-dimensionally on the image memory. That is, based on the label result, the representative value of the hole is developed on the third image memory in the order of the pattern of the hole of the shadow mask.
[0025]
Further, S6 and S7 will be described with reference to FIG.
FIG. 2A shows an image obtained by superimposing an image obtained by photographing a pattern (a part) of the hole 21 of the shadow mask on the memory 22. Here, there are 14 holes. An area indicated by a ruled line drawn vertically and horizontally so as to overlap the image of the hole 21 is the memory 22, and “□” surrounded by the ruled line is a pixel 23 indicating a memory for one pixel.
[0026]
When the labeling process is performed, one label 24 (for example, “1”) is assigned to each hole 21 that is a connected area, and the label is recorded in the pixel on the memory 22 corresponding to the hole. Here, since there are 14 holes, labels “1” to “14” are given to each hole 21. Then, based on the address of the pixel with the same label, the sum is obtained by adding the pixel values of the multi-valued image that has already been captured and recorded in the first image memory. This is the representative value of the hole.
[0027]
Corresponding to each hole 21 shown in FIG. 2A, a storage area 26 on the third image memory 25 shown in FIG. 2B is prepared in two dimensions. That is, the storage area 26 is used in accordance with the arrangement order of the holes 21.
The total (representative value of the hole 21) is transferred into the third image memory 25 in accordance with the arrangement order of the holes 21, recorded in the storage area 26 on the third image memory 25, and expanded in two dimensions. To do.
[0028]
In step 8 (S8), differentiation processing is performed on the representative values developed in the two dimensions. In particular, differentiation processing is not limited, but here, an operation for obtaining a difference from an adjacent image is performed.
In step 9 (S9), a defect is extracted by performing a slice process at a preset slice level on the result of the differential process.
[0029]
By performing such a step, it becomes possible to inspect a defect generated in a periodic pattern such as a shadow mask with high accuracy.
[0030]
Next, a block diagram of the inspection apparatus will be described based on FIG. FIG. 3 is a diagram for explaining a block configuration of the periodic pattern defect inspection apparatus according to the embodiment of the present invention.
[0031]
A shadow mask transmission image is taken by a CCD camera which is the input unit 31 of the inspection apparatus. The photographic signal is converted into digital image data (multi-valued image data) by the A / D converter 32 and then stored in the image memory 300 as multi-valued image data. The image memory is prepared as a plurality of image memory substrates, and here, the one image memory substrate is used.
[0032]
The multilevel image is binarized at a predetermined slice level set in advance by the binarization processing unit 33. Based on the binarized data thus obtained, the labeling processing unit 34 assigns a number to the connected area of the image and records it in the memory.
[0033]
In the addition processing unit 35, the address of the pixel in the connected region that constitutes the same label is obtained based on the label result obtained by the labeling process, and the pixel value of the multi-valued image corresponding to the address is added to the representative value. As a result, the sum for each connected region is calculated. Here, as described above, the calculated value may be the sum of the values of the addresses constituting the contour of the hole portion to which the label result is attached.
[0034]
The sum of the pixel values calculated by the addition processing unit 35 is developed in a two-dimensional manner on one image memory board on the image memory 300 as an image with the representative value of each connected region (hole). At the time when the image is obtained, an image in which the influence of moire is eliminated is obtained. In the pass / fail judgment unit 37, the image is subjected to differential processing to emphasize the defective portion, and defect extraction is performed at a preset slice level.
[0035]
【The invention's effect】
As described above, by implementing the present invention, high accuracy can be achieved without being affected by sensitivity reduction due to moire caused by interference between the pixel pitch of the CCD sensor that captures the periodic pattern and the pitch of the shadow mask holes. Defect detection can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a defect inspection method for a periodic pattern according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a defect inspection method for a periodic pattern according to an embodiment of the present invention. FIG. 3A is a diagram for explaining an image after the labeling processing; FIG. 3B is a diagram for explaining an image in a memory when a defect is extracted; FIG. 3 is a defect inspection of a periodic pattern according to the embodiment of the present invention; FIG. 4 is a diagram for explaining the block configuration of the apparatus. FIG. 4 is a diagram for explaining the overall configuration of the periodic pattern defect inspection apparatus according to the embodiment of the invention.
30 ... Image processing CPU
DESCRIPTION OF SYMBOLS 31 ... Input part 32 ... A / D conversion part 33 ... Binarization process part 34 ... Labeling process part 35 ... Addition process part 36 ... Differentiation process part 37 ... Pass / fail judgment part 38 ... Image processing apparatus 39 ... Output part 300 ... Image memory

Claims (6)

A workpiece having a periodic pattern in which processed portions formed on a base material are periodically and repeatedly disposed, or an arrangement pitch when a processed portion formed on a base material is disposed is a central portion of the workpiece A pattern defect inspection method for inspecting a workpiece having a pattern that gradually changes from the outside to the outside, the step of photographing so as to resolve the processed portion, and a multi-value image obtained by the photographing in a memory and recording, and performing binarization with the recorded multi-valued image a predetermined slice level, based on the binary data the binarization processing, in order to connecting region on the binary image A step of performing a labeling process, which is a numbering process, a step of obtaining an address of a pixel constituting the same label based on a label result obtained by the labeling process, and the corresponding to the address A step of calculating pixel values of the recorded multi-valued image, a step of expanding a representative value based on the calculation result on a memory, a step of performing a differentiation process on the expanded representative value, and the differentiation And a step of extracting a defect by comparing the result of the processing with a slice level.   2. The periodic pattern defect according to claim 1, wherein the sum of each pixel value is calculated by adding each pixel value of the multi-valued image corresponding to the pixel address constituting the same label to calculate the sum for each label. Inspection method.   The calculation processing step according to claim 1, wherein among the pixel values of the multi-value image corresponding to the pixel address constituting the same label, the sum of the pixel values of the multi-value image corresponding to the contour address of the processing unit is calculated. A defect inspection method for periodic patterns characterized by the above. A workpiece having a periodic pattern in which processed portions formed on a base material are periodically and repeatedly disposed, or an arrangement pitch when a processed portion formed on a base material is disposed is a central portion of the workpiece A defect inspection apparatus for a pattern that inspects a workpiece having a pattern that gradually changes from the outside to the outside, and that records a multi-valued image obtained by the imaging unit for imaging so as to resolve the processing unit A binarization processing unit that binarizes a multilevel image recorded in the first memory at a predetermined slice level, and a binary obtained by the binarization processing unit A second memory for recording the digitized data, and a labeling processing unit for performing a labeling process which is a process for sequentially numbering the connected areas on the binary image based on the binarized data recorded in the second memory; , The labeling concerned An arithmetic processing unit that obtains an address of a pixel constituting the same label based on the label result obtained by the processing unit and performs arithmetic processing on the pixel value of the multi-value image corresponding to the address to obtain a representative value; A third memory that develops a representative value based on the processed result in a memory; a differentiation processing unit that performs a differentiation process on the representative value developed in the memory; and a slice level for the result of the differentiation process A defect inspection device for periodic patterns, comprising: a defect determination unit that extracts defects by comparison.   5. The defect inspection of a periodic pattern, wherein the arithmetic processing unit according to claim 4 calculates a sum for each label by adding each pixel value of a multi-value image corresponding to a pixel address constituting the same label. apparatus.   The arithmetic processing unit according to claim 4 calculates the sum of the pixel values of the multi-valued image corresponding to the contour address of the processing unit among the pixel values of the multi-valued image corresponding to the pixel address constituting the same label. A defect inspection apparatus for a periodic pattern.

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