JPH0687045B2 - Automatic pit inspection system for transparent objects - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic pit inspection apparatus for a transparent object for inspecting pits, that is, pits, which are fine holes occurring on the surface of a transparent object. .

Conventional technology Inspection work for microscopic defects on the surface of an object with a microscope
In many cases, a microscopic image is visually inspected, which requires a lot of labor and time. Moreover, there was a great deal of personal error and fatigue by the measurer, and there was a great demand for automation of visual inspection.

An automatic inspection system combining an optical microscope with an automatic XY stage with an automatic focusing mechanism, a TV camera, and a computer has recently been announced as a device that responds to this (Hiroshi Nishizuka: Latest Visual Inspection). Inspection automation: Pages 151-163: 1986/8/28 published by Techno System Co., Ltd. This device converts a microscope image into a digital image and
It is digitized and recognized as an image of the object surface.

However, the automation of visual inspection by conventional microscopes was limited to simply inspecting the surface of the object such as the crystal structure of the IC wafer and the surface defects of the IC chip. Even if an attempt was made to inspect a defect, that is, a pit, it was impossible to simply distinguish the foreign matter adhering to the surface from the pit, and it was impossible to use for such a purpose.

As an example where pit inspection is required, there are increasing opportunities to handle equipment that uses radiation, especially neutrons, and equipment that secondarily generates neutrons, but at that time, personal exposure dose measurement for fast neutrons used Solid state track detectors for home use (Michika; Applied Physics vol.53 no.8 p681 1984).

The measurement is carried out by etching the small radiation damage produced on the plastic plate with, for example, sodium hydroxide, enlarging the etch pits under a microscope, and visually counting. However, what is observed in the field of view of the microscope is the surface image of the object to be inspected, and foreign matter other than the etch pits and the trajectory of radiation other than fast neutrons are also included, and their determination is difficult.

Therefore, at the time of visual inspection, if you observe by displacing the focus of the microscope toward the inside of the object to be inspected by about 10 to 50 microns,
The pits and the images other than the pits can be easily discriminated from each other, and thus both are discriminated. That is, both the pit and foreign matter images on the surface of the object to be inspected are observed as a circular or annular dark part with respect to the peripheral part, but the focus of the microscope is shifted toward the inside of the object to be inspected by 10 to 50 microns. Then, in the internal image of the pit, the brightness of the central portion becomes large, that is, it becomes bright, but the central portion is also observed as a black region in the foreign matter adhering to the surface.

A typical example is shown in FIG. In FIG. 2, the image on the surface of the object to be inspected is shown in the left column, the defocused internal image corresponding to the image in the left column is shown in the center column, and the judgment is shown in the right column. The results are shown.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device for identifying foreign matter and pits on the surface of a transparent object and automatically detecting only the pits.

Means for Solving the Problems The constitution of the first invention of the present application for solving the above problems is as follows.

I. A stage on which an object to be inspected made of a transparent object is placed, and b. A microscope provided to face the object to be inspected mounted on the stage, and c. A light source which is provided on the opposite side of the stage with respect to the stage, and which projects the transmitted light of the object to be inspected into the microscope. A moving mechanism for moving the stage and the microscope relative to each other in a plane direction of the surface of the object to be inspected and in a direction perpendicular to the surface direction; A television camera that outputs an image of the inspected portion of the inspected object captured by the microscope as a video signal; An A / D converter for digitally converting the video signal, a binarization circuit for extracting a black area in which the brightness of the image is equal to or less than a predetermined threshold value, and an arithmetic unit for obtaining the center coordinates of each black area. , The digital data obtained by the digital conversion, the binarized data obtained by the binarization circuit, and the brightness data of the internal image obtained by moving the focus inward of the inspection object by the moving mechanism. And an image processing device including a memory for storing A discriminator that compares the luminance in the vicinity of the center of the black area on the surface of the inspection object with the luminance of the internal image of the inspection object in the corresponding area, and determines that the internal image is brighter when it is a pit. Ji. An pit automatic inspection apparatus for a transparent object, comprising: an adder that adds the pit determination results sequentially obtained by the determination unit.

When the pits of the object to be inspected have a certain pattern, it is possible to further rationalize the above first invention, and this is the second invention having the following configuration. .

I. A stage on which an object to be inspected made of a transparent object is placed, and b. A microscope provided to face the object to be inspected mounted on the stage, and c. A light source that is provided on the side opposite to the microscope with respect to the stage, and that projects the transmitted light of the object to be inspected into the microscope. A moving mechanism for moving the stage and the microscope relative to each other in a plane direction of the surface of the object to be inspected and in a direction perpendicular to the surface direction; A television camera that outputs an image of the inspected portion of the inspected object captured by the microscope as a video signal; An A / D converter for digitally converting the video signal, a binarization circuit for extracting a black area in which the brightness of the image is equal to or less than a predetermined threshold value, and an arithmetic unit for obtaining the center coordinates of each black area. An image processing device comprising a digital data obtained by the digital conversion and a memory for storing data of an internal binary image obtained by moving a focal point inward of the object by the moving mechanism; ． A judging device for judging a pit when the internal region of the inspection object corresponding to the vicinity of the center of the black region on the inspection object surface is white in the binarized image; An pit automatic inspection apparatus for a transparent object, comprising: an adder that adds the pit determination results sequentially obtained by the determination unit.

It is an automatic pit inspection device for transparent objects.

In the first aspect of the invention, in the vicinity of the surface of the object to be inspected, the brightness in the vicinity of the center coordinates of the area extracted as the black area and the focus of the microscope in the same area are measured inwardly of the object to be inspected. The brightness is compared to determine the pit.

On the other hand, in the second aspect of the present invention, in the vicinity of the center coordinates of the black region extracted near the surface of the object to be inspected, the focus of the microscope is shifted toward the inside of the object to be inspected, and the binarized image near the corresponding center coordinates. If is white, it is determined to be a pit.

Function In the apparatus according to the first aspect of the present invention configured as described above, each defect on the surface of the object to be inspected is first supplemented as a black region of the surface image, and the luminance near the center coordinates of each supplemented black region is obtained. , Then, at the center point of each corresponding black area, the focus of the microscope is shifted inward of the object to be inspected,
The brightness of the internal image in the vicinity of the center coordinates is measured, and compared with the original brightness, when the latter brightness is brighter, the defect is determined to be a pit, and the other images are determined to be other defects. It

Furthermore, in the second aspect of the present invention, when the internal binarized image corresponding to the vicinity of the center coordinates of the black area is white, it is processed as a pit, and when it is black, it is determined to be another defect.

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

FIG. 1 is an overall configuration diagram for explaining the configuration of an embodiment of the present invention.

FIG. 3 is a flow chart showing an image processing procedure for each screen in the embodiment of the first invention.

In Fig. 1, X that can be automatically moved in the X, Y, and Z axis directions
The to-be-inspected object 1 set on the -Y-Z stage 3 is transmitted and illuminated by a light source 5 provided on the opposite side of the microscope 2 with respect to the stage 3. By the automatic operation of the driving device 4, the focus of the microscope 2 is adjusted to the surface of a predetermined image of the inspection object (FIG. 3, s2). The microscope 2 captures and magnifies the surface image of the inspection object. The television camera 6 converts the received microscopic image into a video signal.

In the image processing device 7, the video signal from the television camera 6 is converted into an A / D converter (analog / digital converter) 8
Is converted into a digital signal by and stored in the memory 9 (s3). To make the image information into two-dimensional digital data, it is spatially sampled into M × N pixels, and the density information of each pixel is quantized into L bits. Further, the digital data taken in is binarized by a binarization circuit 10 with a predetermined threshold value and is extracted as a black area (s4). The binarized data is also stored in the memory 9. The arithmetic unit 11 reads the binarized data from the memory 9, finds the barycentric coordinates of each area (s5), and measures the brightness thereof (s6). In this embodiment, the center of gravity is used as the center coordinate. The image recognized as a black area contains foreign matter in addition to the pits.

The XYZ stage 3 moves in the Z-axis direction, the focus of the microscope is shifted toward the inside of the body to be inspected (s7), and the brightness is measured (s8). The movement is automatically performed by the drive device 4. The amount of movement depends on the depth of the pit, but in the case of the radiation etch pit, 10 to 50 μm is suitable. The obtained internal image is processed in the same manner as the case of the surface image and stored in the memory 9 as digital data.

In the determiner 12, the brightness of the center of gravity of the black area in the surface image and the brightness of the internal image corresponding to this are read from the memory 9 and compared, and the brightness of the internal image is
If it is brighter than a specified threshold value ε, it is judged as a pit (s9). The judgment is repeated for all black areas (s9). The determination is repeated for all black areas (s11). If the determination result is a pit, the adder 13
In step S10, the total number of pits is sequentially added to obtain the total number (s10).

By automatically operating the X-Y-Z stage 3 while changing the field of view of the microscope 2, the operation of the flowchart shown in FIG. Output device 1
4, output to a printer, for example.

FIG. 4 is a flowchart showing an embodiment of the second invention.

The microscope image of the surface of the inspected object 1 taken by the microscope 2 and the television camera 6 (s22, s23 in Fig. 4) is digitally converted, binarized and extracted as a black area (s2).
Four). This includes defects other than the pits to be detected.

The center of gravity is obtained as the center coordinates of the extracted black area (s25). By the automatic operation of the XYZ stage 3, the focus of the microscope 2 is moved to the inside of the DUT 1 (s2
6), the captured image (s27) is 2 at the specified threshold.
It is valued (s28). The color of the binarized image inside the inspection object corresponding to the vicinity of the center coordinates of the black region on the inspection object surface extracted earlier is determined (s29), and if it is white, it is counted as a pit (s30). The same operation is repeated for all black areas on the screen (s31).

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to automatically count the number of pits of a transparent object, which has conventionally relied on visual inspection, while distinguishing it from other defects.

Furthermore, since the image of the pit is circular, by combining the operations of obtaining the roundness of the shape of the black area on the surface of the object to be inspected, and identifying and judging based on a certain standard, surface scratches can be made simultaneously. Etc. can be identified.

In the second aspect of the present invention, it is possible to use a binary image processing device that is easier and cheaper to manufacture than the grayscale image processing device.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, and FIG.
FIG. 2 is a block diagram showing the overall concept, FIG. 2 shows a binarized image and an example of its determination, FIG. 3 is an operation flowchart of the first invention, and FIG. 3 is an operation flowchart in the invention of FIG.

Claims (2)

[Claims] 1. A. A stage on which an object to be inspected made of a transparent object is placed, and b. A microscope provided to face the object to be inspected mounted on the stage, and c. A light source which is provided on the opposite side of the stage with respect to the stage, and which projects the transmitted light of the object to be inspected into the microscope. A moving mechanism for moving the stage and the microscope relative to each other in a plane direction of the surface of the object to be inspected and in a direction perpendicular to the surface direction; A television camera that outputs an image of the inspected portion of the inspected object captured by the microscope as a video signal; An A / D converter for digitally converting the video signal, a binarization circuit for extracting a black area in which the brightness of the image is equal to or less than a predetermined threshold value, and an arithmetic unit for obtaining the center coordinates of each black area. , The digital data obtained by the digital conversion, the binarized data obtained by the binarization circuit, and the brightness data of the internal image obtained by moving the focus inward of the inspection object by the moving mechanism. And an image processing device including a memory for storing A discriminator that compares the luminance in the vicinity of the center of the black area on the surface of the inspection object with the luminance of the internal image of the inspection object in the corresponding area, and determines that the internal image is brighter when it is a pit. Ji. An automatic pit pit inspection apparatus for transparent objects, comprising: an adder that adds the pit determination results sequentially obtained by the determination unit. 2. A. A stage on which an object to be inspected made of a transparent object is placed, and b. A microscope provided to face the object to be inspected mounted on the stage, and c. A light source that is provided on the side opposite to the microscope with respect to the stage, and that projects the transmitted light of the object to be inspected into the microscope. A moving mechanism for moving the stage and the microscope relative to each other in a plane direction of the surface of the object to be inspected and in a direction perpendicular to the surface direction; A television camera that outputs an image of the inspected portion of the inspected object captured by the microscope as a video signal; An A / D converter for digitally converting the video signal, a binarization circuit for extracting a black area in which the brightness of the image is equal to or less than a predetermined threshold value, and an arithmetic unit for obtaining the center coordinates of each black area. An image processing device comprising a digital data obtained by the digital conversion and a memory for storing data of an internal binary image obtained by moving the focal point inwardly of the inspection object by the moving mechanism; ． A judging device for judging a pit when the internal area of the object under test corresponding to the vicinity of the center of the black area on the surface of the object under test is white in the binarized image; An automatic pit pit inspection apparatus for transparent objects, comprising: an adder that adds the pit determination results sequentially obtained by the determination unit.