JP3984367B2 - Surface defect inspection method and inspection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has a rough surface portion, and the surface portion of a sample provided with a hole portion having a concave shape inwardly connected to the surface portion of the base material by drilling or the like of the base material. The present invention relates to a method and an inspection apparatus for inspecting a shape defect in a connected hole, and more particularly, to an inspection method and an inspection apparatus for a defect in which an edge of a surface hole of a shadow mask used in a color television is missing.
[0002]
[Prior art]
Conventionally, as a method for inspecting the defect where the edge of the surface hole of the shadow mask is missing, the reflected light from the shadow mask is photographed by simply reflecting and illuminating without controlling the incident angle of the illumination light to the sample, A method for extracting surface defects by image processing is known. However, in this method, since the surface roughness of the shadow mask is rough, only a low detection sensitivity can be obtained, which is a problem.
For example, since the surface of the shadow mask substrate is rough, the portion shown in FIG. 9A is obtained as a photographed image as shown in FIG. 9B, and defect detection cannot be accurately obtained. .
As shown in FIG. 9B, the pseudo surface hole portion defective portion 119 is detected together with the surface hole portion defective portion 118.
FIG. 9A shows that the surface of the base material 111 is rough in an easy-to-understand manner.
Separately, in order to increase the detection sensitivity, the linear area photographing means and the light source are used, the linear area photographing means and the light source are arranged at a predetermined angle with respect to the shadow mask surface, and the shadow mask is obliquely inclined. There is also a method of photographing the transmitted light that has passed through.
However, in this method, it is necessary to adjust the optimum shooting angle for each type of shadow mask, and there is a problem that operation and control become complicated, and defects in all directions cannot be detected in a single inspection. Therefore, in order to detect defects in all directions, it is necessary to inspect by changing the direction a plurality of times, which is a problem in terms of quality and workability.
Furthermore, as a method for inspecting a defect in which the edge of the surface hole of the shadow mask is missing, a method for detecting a defective portion from the obtained image data obtained by transmitting and illuminating a sample and using an area sensor and a mirror (Japanese Patent Application) No. 9-139193) has already been proposed by the inventors of the present application.
However, this method using an area sensor is not suitable for increasing the resolution for increasing the inspection accuracy, and as a result, requires a lot of inspection time, and shortening of the inspection time is required.
Under these circumstances, in recent years, shadow masks are increasingly required to have a larger size and higher definition, and quality control has become important. With high detection sensitivity, relatively easy and workable operation. A good shadow mask inspection method has been demanded.
[0003]
[Problems to be solved by the invention]
As described above, more and more shadow masks are required to have a larger size and higher definition. In the shadow mask surface inspection method, a surface inspection method and an inspection apparatus with high detection sensitivity and easy workability are provided. It has come to be required.
Under such circumstances, an object of the present invention is to provide a shadow mask surface inspection method and inspection apparatus with high detection sensitivity and easy workability.
[0004]
[Means for Solving the Problems]
The method for inspecting a surface defect according to the present invention includes a sample having a periodic pattern in which a pattern having a rough surface portion and periodically formed by a hole portion having a concave shape connected to the surface portion of the base material is provided. An inspection method for inspecting a shape defect of a pattern including a hole connected to the surface portion, wherein the sample is moved relative to an imaging system and is on the optical axis of reflected bright-field illumination. Each of the imaging regions of the sample is reflected bright-field illuminated with diffused light having a light-receiving angle of 0 ° or more and 30 ° or less about the optical axis of the illumination light as a reflected bright-field illumination. After the sample surface is photographed to obtain a photographed image, the image data of the photographed image is subjected to image processing, and the fillet diameter and / or the projection area of each pattern of the periodic pattern of the sample is obtained. If the area is not within the specified range, It is characterized by being judged as a place.
In the above, the image processing of the image data of the photographed image is performed by binarizing each pixel of the image data of the photographed image at a predetermined slice level to create a binary image, and from the binary image, A fillet diameter of each pattern and / or a projected area of each pattern is obtained, and a portion where each value is not within a predetermined range is determined as a defective portion.
In the above, the sample is a shadow mask.
In general, the diameter of a figure projected in a predetermined direction is the fillet diameter.
The projected area referred to here is the area of a planar image obtained by projecting the entire recessed hole, which is a three-dimensional structure including irregularities, onto a predetermined surface. When the image data of the image is binarized, it can be expressed by the number of pixels of the value (0 to 1) of the area corresponding to the recessed hole.
[0005]
The surface defect inspection apparatus according to the present invention has a rough surface portion, and a sample having a periodic pattern in which a pattern composed of a hole portion having a shape that is connected to the surface portion of the substrate and is recessed inside is periodically arranged. An inspection apparatus for inspecting a shape defect of a pattern including a hole connected to the surface portion, a transport unit that moves the sample relative to the imaging system, and a linear area imaging unit that images the sample surface When photographing, the light receiving angle at which each photographing region of the sample on the sample axis on the optical axis of the reflected bright field illumination is illuminated by the reflected bright field illumination is 0 ° or more about the optical axis of the illumination light, 30 The linear illumination means that illuminates the reflected bright field with diffused light that is less than or equal to the angle, and the fillet diameter and / or projection area of each pattern of the periodic pattern of the sample is obtained from the photographed image data obtained by photographing. Each value is within the specified range. And an image processing unit that determines that the defective portion is a defective portion.
In the above, the sample is a shadow mask.
[0006]
[Action]
The surface defect inspection method of the present invention is configured as described above to periodically repeat a pattern having a rough surface portion and a hole portion having a shape that is connected to the surface portion of the base material and recessed inward. Providing a defect detection method that has high detection sensitivity and relatively good workability with an inspection method for inspecting a pattern defect consisting of a hole connected to the surface of a sample having a periodic pattern arranged Is possible.
In particular, when applied to the inspection of the shape defect of the surface hole of the shadow mask, the linear area photographing means and the linear light source are used to increase the detection sensitivity, and the linear area photographing means is at a predetermined angle with respect to the shadow mask surface. Adjust the optimal control angle of the illumination light for each product type, or light in all directions of the hole, as in the inspection method in which the light source is placed and the transmitted light that has passed through the shadow mask is photographed from an angle of the shadow mask surface. This method is practical because it does not require much inspection time as in the inspection method in which the sample is transmitted and illuminated and imaged using an area sensor and a mirror.
Specifically, the surface portion of the sample having a periodic pattern in which a pattern having a rough surface portion and connected to the surface portion of the base material and having a concave portion formed inside is periodically repeated. Is a method for inspecting a shape defect of a pattern consisting of a hole connected to a light source, and is reflected by diffused light controlled within a predetermined spread angle while moving a sample relative to an imaging system. Illuminate the field of view, photograph the sample surface with a linear region imaging means to obtain a photographed image, image-process the image data of the photographed image, fillet diameter of each pattern of the periodic pattern of the sample, and / or This is achieved by obtaining the projected area and determining that each value is not within a predetermined range as a defective portion.
That is, the surface portion of the sample surface is rough by illuminating the reflected bright field with diffused light controlled within a predetermined spread angle and photographing the sample surface with a linear region imaging means to obtain a photographed image. It is assumed that the decrease in the defect detection sensitivity from the photographed image due to the above can be almost stopped.
In particular, in the case of a sample shadow mask, each imaging region of the sample on the optical axis of the reflected bright field illumination has a light receiving angle that is illuminated by the reflected bright field illumination so that it is 0 ° or more and 30 ° or less. It is effective to control the diffused light of the reflected bright field illumination.
As the image processing of the image data of the photographed image, the image processing of the image data of the photographed image creates a binary image by binarizing each pixel of the image data of the photographed image at a predetermined slice level. There is a process of obtaining the fillet diameter of each pattern of the sample and / or the projected area of each pattern from the digitized image, and determining a defective portion as a defective portion where each value is not within a predetermined range.
[0007]
By configuring the surface defect inspection apparatus of the present invention as described above, it is possible to provide a shadow mask surface inspection apparatus having high detection sensitivity and relatively good workability.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
First, an example of an embodiment of the surface defect inspection apparatus of the present invention will be described.
FIG. 1A is a schematic diagram of a first example of an embodiment of a surface defect inspection apparatus according to the present invention, and FIG. 1B is an image of diffuse bright field illumination of the first example taken with diffused light. FIG. 2 is a diagram for explaining the system, FIG. 2 is a diagram for explaining the control of diffused light in the reflected bright field illumination of the first example, and FIG. 3 is a diagram showing surface hole defects in the shadow mask. FIG. 5 is a diagram for explaining the control of the light irradiation angle by the optical fiber, and FIG. 5 is a schematic diagram of the apparatus of the second example of the embodiment.
2A is a side view in the same direction as FIG. 1A, FIG. 2B is a view from the A1 side in FIG. 2A, and FIG. 2C is FIG. It is sectional drawing of the light-shielding plate (light control board) in A2-A3 of (a).
1 to 5, 110 is a sample (shadow mask), 110S is an imaging region, 111 is a base material, 113 is a front hole portion (pattern), 114 is a back hole portion, 115 is a surface portion of the base material, 118 is 120 is a linear illumination means, 121 is an illumination light source (linear light source), 125 is a light shielding plate (light control plate), 130 is a linear area photographing means (CCD line sensor camera), and 135 is A lens, 140 is an image processing unit, 160 is a stage, 180 is a half mirror, and 190 is an optical fiber.
[0009]
First, a surface defect inspection apparatus according to a first example of the embodiment will be described.
The apparatus of this example uses a shadow mask having an etched outer shape as a sample, connects to the surface portion (115 in FIG. 3) of the base material (111 in FIG. 3), and has a front hole portion (113 in FIG. 3) recessed inward. In the inspection apparatus for inspecting the shape defect of the pattern consisting of the hole connected to the surface portion of the sample having the periodic pattern in which the pattern consisting of) is periodically repeated, as shown in FIG. A stage 160 on which a sample (shadow mask) 110 is placed and moved relative to the imaging system, a linear area imaging means 130 including a CCD line sensor camera that images one surface of the sample 110, and the sample 110 during imaging And a linear illumination means 120 for illuminating a reflected bright field with diffused light having a predetermined spread angle, and each pattern of the periodic pattern of the sample from the obtained captured image data Fillet size, determine the projected area, respectively, and an image processing unit 140 for determining a predetermined fillet diameter of the predetermined pattern, and the different locations predetermined projected area as defect sites.
In the apparatus of this example, as shown in FIG. 1 (b), the optical axis L1 of the linear area imaging means 130 and the normal line upright in the imaging area of the surface of the sample 110 in the direction of the optical axis L1. When the angle θ1 is made, the angle formed by the optical axis L2 and the normal line of the linear illumination unit 120 is also θ1, and the reflected light is reflected by the diffused light controlled within a predetermined spread angle θ0 with respect to the optical axis L2. Bright field illumination. That is, the sample is photographed by controlling the luminous flux of the illumination light applied to the photographing region 110S within the predetermined spread angle θ0 with respect to the optical axis L2.
A shadow mask used in a color television prawn tube is generally perforated by etching, and a partial plane is shown in FIG. 3A and a partial cross-section is shown in FIG. 3B. In addition, a large hole is formed on one side and a small hole is formed on the other side, and a through hole is formed by both holes. Since the color television uses the large hole side of the shadow mask as a side for human observation, the hole on the large hole side is normally the front hole 113 and the hole on the small hole side is the back hole 114. they said. Here, the shape defect portion of the surface hole portion is referred to as a surface hole shape defect 118.
FIG. 3B is a view showing a cross section taken along B1-B2 in FIG.
In the case of a shadow mask, the one having good detection sensitivity due to its rough surface generally has θ0 of 0 ° or more and 30 ° or less.
[0010]
In this example, as described above, the reflected bright field illumination is performed with the diffused light within the predetermined spread angle θ0, but as shown in FIGS. 2 (a) and 2 (b), the illumination light source 121 emits light. The light is controlled by the light shielding plate (light control plate) 125 in the range of the angle θ0 incident on the imaging region 110S.
As shown in FIG. 2 (c), the light shielding plate 125 has a lattice-like plane and has a predetermined height. The light-shielding plate 125 is made of a member that absorbs light incident on this portion without being reflected. The direction of light passing through the light shielding plate 125 is limited by the interval and the height thereof.
Therefore, a light shielding plate 125 is placed between the imaging region 110S of the sample 110 and the illumination light source (linear light source) 121, and the range of the angle θ0 of the illumination light incident on the imaging region 110S is controlled within a predetermined angle. can do.
Normally, the light shielding plate 125 is black.
When detecting a surface hole defect in the shadow mask, an optical fiber 190 as shown in FIG. 4 is used in place of the light shielding plate 125 shown in FIG. 2, and the angle θ0 of the illumination light incident on the imaging region 110S is controlled. You may do it.
As shown in FIG. 4, a plurality of optical fibers are used by being bundled. However, the angle θ4 of light emitted from each optical fiber (the spread angle from the optical axis L4) depends on the material, and therefore has an appropriate angle. Select one to use.
Thus, the angle θ0 of the illumination light incident on the imaging region 110S can be controlled within 20 °.
[0011]
Next, a surface defect inspection apparatus according to a second example of the embodiment will be briefly described.
The surface defect inspection apparatus of the second example shown in FIG. 5 illuminates the illumination light from the illumination light source 121 in the imaging region 110S of the sample 110 via the half mirror 180, and its optical axis is substantially on the surface of the sample 110. Irradiation is performed so as to be substantially vertical, and reflected light from the imaging region 110S of the sample 110 is incident on the linear region imaging means 130 including a CCD line sensor camera via the half mirror 180, so that the sample 110 As in the case of the apparatus shown in FIG. 1, the light shielding plate is disposed between the half mirror 180 and the illumination light source 121 in order to control the angle θ0 of the illumination light incident on the imaging region 110S. (Light control plate) 125 is arranged.
[0012]
Next, an example of an embodiment of the surface defect inspection method of the present invention will be described.
Also, this replaces the description of the processing of the image processing unit of the inspection apparatus shown in FIG.
In this example, the surface defect inspection apparatus of the shadow mask is inspected using the surface defect inspection apparatus of the first example shown in FIG. 1, and is simply based on FIG. 6 while referring to FIG. explain.
FIG. 6 is a process flow diagram of this example.
In FIG. 6, S110 to S140 indicate processing steps.
First, as shown in FIG. 1A, the sample 110 is placed on the stage 160 with the shadow mask (sample) 110 placed on the stage 160 with the surface hole side to be inspected facing up. Reflected bright field illumination is performed with diffused light controlled within a predetermined spread angle (θ0 in FIG. 1B) while being relatively moved, and the inspection area on the sample surface is formed by the linear area imaging means 130. Take a picture to get a picture. (S110)
Since this is a shadow mask measurement, θ0 is set to 0 ° or more and 30 ° or less from the rough state of the surface. For other samples, the value of θ0 is determined corresponding to the rough state of the surface. It is preferable.
The movement of the stage 160 is appropriately determined based on the relationship between the inspection area of the sample 110 and the visual field captured by the linear area imaging unit 130.
For example, FIG. 7A shows the direction of movement of the visual field captured by the linear region imaging unit 130 when the width of the visual field 130S captured by the linear region imaging unit 130 is narrower than the width of the inspection region of the sample 110. A predetermined inspection region of the sample can be photographed by assuming that is indicated by an arrow.
Further, the inspection area of one sample 110 may be photographed by two linear area imaging means 130. When two linear area imaging means 130 in FIG. 7 are used, FIG. As shown in the figure, the imaging field of view 130S can be approximately double that of the single linear area imaging means 130. The moving direction of the field of view taken by each of the linear area imaging means 130 can be taken in the direction of the arrow, and a predetermined inspection area of the sample can be taken.
[0013]
Next, the obtained image data of the captured image is binarized. (S120)
For example, the value of the image data at each position of the pixel column in C1-C2 in FIG. 8B showing a part of the shadow mask is as shown in FIG.
The value of each pixel in FIG. 8A is compared with a level (slice level SL) of a predetermined value, and 1 of more pixels (of course, other predetermined values 2 and 3 may be used) By setting the value of a pixel below the value level to 0, binary image data in which each pixel is divided into two regions according to the value can be obtained.
The pixel column of the binarized image data corresponding to the C1-C2 location in FIG. 8B is, for example, as shown in FIG.
It can be seen that the number of 0-valued continuous pixel columns at the position of the surface hole shape defect (also referred to as “egre defect”) is larger than that of the normal hole part (pattern) 113.
Next, with regard to the binarized image data obtained by binarizing each pixel obtained in this way, the X direction is set in a predetermined direction, and the hole (pattern) as shown in FIG. By projecting in the Y direction, fillet diameters in the X and Y directions are obtained. (S130)
Alternatively, with regard to the binarized image data in which each pixel is binarized, for each hole (pattern) as shown in FIG. Count the number to determine the projected area of the surface hole. (S130)
In general, the diameter of a figure projected in a predetermined direction is a fillet diameter.
Next, when each value is not within a predetermined range with respect to the fillet diameter and projected area in the X direction and Y direction of each hole (pattern) obtained, that part is extracted as a defective part. (S140)
[0014]
In this way, a defect in the surface hole portion of the shadow mask is detected from the photographed image. In the case of the method of this example, the diffused light controlled within a predetermined spread angle (θ0 in FIG. 1B). The detection sensitivity is high by performing defect detection on the basis of a photographed image obtained by illuminating the reflected bright field with the linear region imaging means 130 and photographing the inspection area of the sample surface.
[0015]
【The invention's effect】
The present invention, as described above, has a rough surface portion, and a sample having a periodic pattern in which a pattern composed of holes having a shape that is connected to the surface portion of the base material and is recessed inside is periodically arranged. It is possible to provide a defect detection method that has a high detection sensitivity and relatively good workability in an inspection method for inspecting a shape defect of a pattern composed of a hole portion connected to the surface portion. At the same time, it is possible to provide an inspection apparatus capable of performing such an inspection method.
As a result, it is possible to cope with the higher quality of shadow masks and the mass production of high quality products.
[Brief description of the drawings]
FIG. 1A is a schematic diagram of a first example of an embodiment of a surface defect inspection apparatus according to the present invention, and FIG. 1B is a diagram of reflected bright field illumination of the first example. FIG. 2 is a diagram for explaining an imaging system using diffused light. FIG. 2 is a diagram for explaining control of diffused light of reflected bright field illumination in the first example of the embodiment of the surface defect inspection apparatus of the present invention. 3 is a diagram showing a surface hole defect of a shadow mask. FIG. 4 is a diagram for explaining control of an irradiation angle of light by an optical fiber. FIG. 5 is a second embodiment of a surface defect inspection apparatus according to the present invention. FIG. 6 is a flow diagram of an example of an embodiment of the surface defect inspection method of the present invention. FIG. 7 is a diagram for explaining the movement of the visual field of the linear region photographing means. FIG. 9 is a diagram for explaining the binarization processing of image data. FIG. 9 is a diagram for explaining a conventional inspection method.
110 Sample (shadow mask)
110S imaging region 111 base material 113 surface hole part (pattern)
114 Back hole part 115 Surface part 118 of base material Front hole part defective part 119 Pseudo front hole part defective part 120 Linear illumination means 121 Illumination light source (linear light source)
125 Shading plate (light control plate)
130 Linear area imaging means (CCD line sensor camera)
135 Lens 140 Image Processing Unit 160 Stage 180 Half Mirror 190 Optical Fiber

Claims (5)

From the hole portion connected to the surface portion of the sample having a periodic pattern in which a pattern having a rough surface portion and connected to the surface portion of the base material is formed by periodically repeating a pattern formed of a hole portion having a concave shape. An inspection method for inspecting a shape defect of a pattern in which each imaging region of the sample on the optical axis of the reflected bright field illumination is reflected in the reflected bright field while moving the sample relative to the imaging system. The reflected bright field illumination is performed with diffused light whose illumination angle is 0 ° or more and 30 ° or less around the optical axis of the illumination light, and the sample surface is photographed by the linear region imaging means to obtain a photographed image. After obtaining the image data of the photographed image, the fillet diameter and / or the projection area of each pattern of the periodic pattern of the sample is obtained, and a place where each value is not within a predetermined range is determined as a defective place. Table characterized by judging Inspection method for surface defects.   2. The image processing of the image data of the photographed image according to claim 1, wherein each pixel of the image data of the photographed image is binarized at a predetermined slice level to create a binarized image, and the sample image is generated from the binarized image. A method for inspecting a surface defect, characterized in that a fillet diameter of each pattern and / or a projected area of each pattern is obtained, and a portion where each value is not within a predetermined range is determined as a defect portion.   3. The surface defect inspection method according to claim 1, wherein the sample is a shadow mask. From the hole portion connected to the surface portion of the sample having a periodic pattern in which a pattern having a rough surface portion and connected to the surface portion of the base material is formed by periodically repeating a pattern formed of a hole portion having a concave shape. An inspection apparatus for inspecting a shape defect of a pattern, a transport unit for moving a sample relative to an imaging system, a linear area imaging means for imaging a sample surface, and reflecting a sample surface during imaging Each sample area on the optical axis of the bright field illumination is reflected by the diffused light whose angle of light received by the reflected bright field illumination is 0 ° or more and 30 ° or less around the optical axis of the illumination light. The linear illumination means for visual field illumination and the captured image data obtained by photographing are used to determine the fillet diameter and / or projection area of each periodic pattern of the sample, and the respective values are not within a predetermined range. Image that determines the location as a defective location An apparatus for inspecting surface defects, comprising: an image processing unit.   5. The surface defect inspection apparatus according to claim 4, wherein the sample is a shadow mask.

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