JPH05136236A - Pattern test device - Google Patents

Abstract

PURPOSE:To enhance inspection accuracy in relatively simple structure without increasing inspection time. CONSTITUTION:There is installed an optical unit 12 which is provided with mirrors 12a, 12b and 12c above an article 2 to be inspected. The optical unit 12 allows optical signals of patterns 16a, 16b and 16c of the article 2 and optical signals equivalent to non-pattern areas (a), (b) and (c) (pattern region) near the above patterns to enter an image sensing device 6 so that their images may be formed on a high resolution CCD line sensor 14. It is possible to detect fine defects in the pattern regions by image-processing an image signal converted photoelectrically by the image sensing device 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus for inspecting an object to be inspected having a regular pattern such as a shadow mask of a color cathode ray tube.

[0002]

2. Description of the Related Art As a general pattern inspection apparatus, for example, as shown in FIG. 11, a light source 107 and an XY table 1 are used.
06, glass plate 105, camera 101, image processing apparatus 1
08 and the output device 109, the inspection object 1
A device for inspecting pattern 04 is conventionally known. According to this apparatus, the inspection object 104 is transmitted and illuminated by the light source 107, and its image is formed on the CCD line sensor 103 in the camera 101. The image of the inspection object 104 is photoelectrically converted by the CCD line sensor 103,
A defect is detected by the image processing device 108, and the result is output by the output device 109.

Further, as a defect detection device for an object to be inspected having a regular pattern, a spectrum pattern is obtained by scanning and irradiating the pattern to be inspected with coherent light, and the spectrum pattern which exists independently is almost zero. It is known that a spectrum pattern component of a pattern to be inspected, which is obtained through a filter having a region as a pass band, is Fourier-transformed and a defect is detected from the Fourier-transformed information ( JP-A-58-
147119).

[0004]

In order to detect a minute defect by using the above-mentioned general pattern inspection apparatus, CC is used.
It is necessary to increase the resolution per pixel of the D line sensor 103, but this increases the number of pixels of the input image in the defect inspection, which causes an increase in inspection time.

Further, the detection device described in Japanese Patent Laid-Open No. 58-147119 has a complicated and expensive structure such as that the observation environment must be darkened and that vibration-proof equipment is required. There is a problem of becoming.

The present invention has been made in view of the above points, and an object thereof is to provide a pattern inspection apparatus capable of improving inspection accuracy without increasing inspection time with a relatively simple structure. To do.

[0007]

In order to achieve the above object, the present invention provides a light source for irradiating an inspected object having a pattern with light, and a light beam emitted from the inspected object according to the pattern shape of the inspected object. A pattern inspecting device, which receives a pattern optical signal and photoelectrically exchanges the pattern optical signal, and defect detecting means for detecting a defect of the pattern by image-processing the photoelectric output from the image capturing means. And an object to be inspected, an optical selecting means for optically selecting only an optical signal emitted from the pattern of the object to be inspected and a non-patterned portion in the vicinity of the pattern and entering the image pickup means is provided. It was done like this.

[0008]

Operation Only the optical signals emitted from the pattern of the object to be inspected and the non-patterned portion in the vicinity of the pattern (hereinafter referred to as "pattern area") are selectively incident on the image pickup means.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a pattern inspection apparatus according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA 'of FIG. In these figures, 1 is an XY table,
A glass plate 1a is fixed to the XY table 1. The inspection object 2 is placed on the glass plate 1a. XY
The table 1 is configured to be movable in the Y direction and the X direction in the drawing by the drive devices 3 and 4. Above the XY table 1, a first imaging device 5, an optical unit 12,
The second image pickup device 6 is provided and is fixed to the support member 7. Further, below the XY table 1, a light source 11 that emits parallel light for illuminating the inspection object 2 is arranged.

The object 2 to be inspected in this embodiment is, for example, as shown in FIG. 4, a steel plate having a thickness of about 0.1 mm in which a large number of rectangular pattern holes 16 are regularly arranged. FIG. 5 is an enlarged view of a part of FIG. In the figure, the pattern hole 16 has a width BH of 100 μm and a length L.
Is about 400 μm, and the pitch PITX in the X direction is 1
The pitch PITY in the Y direction is about 700 μm. Further, (a), (b), and (c) in the same figure show the range where the pattern hole 16 does not exist. The pattern hole 16 of the inspection object 2 is not limited to a rectangle, but may be a square, an oval, a circle, or the like.

The first image pickup device 5, as shown in FIG.
The lens 9 and the CCD line sensor 10 are main components, and the CCD line sensor 10 is set to a relatively low resolution (for example, 40 μm per pixel) by an optical system.

FIG. 3 is a sectional view taken along line BB ′ of FIG.
The optical unit (optical selection means) 12 has three mirrors 1.
2a, 12b, and 12c are main constituent elements, and the second image pickup device 6 is mainly composed of the lens 13 and the CCD line sensor 14. All the mirror surfaces of the three mirrors 12a to 12c are mounted at an angle of 45 ° with respect to the horizontal plane. CCD line sensor 14 of the second image pickup device 6
Is a relatively high resolution (for example, one pixel 10
μm) is set.

FIG. 6 is a view for explaining the operation of the optical unit 12, and FIG. 6 (b) is a view of the inspection object 2 as seen from above. Here, it is assumed that the portion of the line C-C 'is imaged on the CCD sensor 14 and the vicinity of the pattern hole 16a is examined.
Only the image (optical signal) in the range of −F ′ is incident on the second image pickup device 6 and imaged on the CCD line sensor 14.
Similarly, by the mirrors 12b and 12c, G-G ', H-
Only the image in the range H'is formed on the CCD line sensor 14. Therefore, by moving the XY table 1 in the Y direction, only the areas (pattern areas) (e), (e), and (e) in FIG. 6 are imaged by the CCD line sensor 14.

As described above, the first image pickup device 5 has a low resolution and picks up an image of the entire area of the object to be inspected 2, and the second image pickup device 6 has a high resolution and has a pattern of the object to be inspected 2. Only the area is imaged.

As shown in FIG. 7, the first and second image pickup devices 5 and 6 respectively have a low resolution defect detection image processing device 1.
8 and the high resolution pattern portion defect detection image processing device 19. The image processing device 18 detects a defect only in a region of the input image excluding the pattern region, the image processing device 19 detects a minute defect in the pattern region, and inputs the detection result to the central processing unit 20. .. The central processing unit 20 outputs the result via the output device 20.

Next, referring to FIG. 8, as one example, a low resolution CCD line sensor (hereinafter referred to as "first line sensor") 10 and a high resolution CCD line sensor (hereinafter referred to as "second line sensor"). The acquisition of image data by (14) will be described more specifically. Note that FIG.
Is a diagram for explanation, and the dimension shown in the figure and the length in the figure do not necessarily have a fixed relationship. Here, the resolution of the first line sensor 10 is set to 40 μm per pixel by the optical system (resolution in the X direction), the number of pixels is 2048, and the resolution of the second line sensor 14 is set to 10 μm ( Resolution in X direction), number of pixels 51
2 is 40 μm × 2048 pixels in the X direction (81.
92mm) data is considered. The resolution in the Y direction is determined by the table feed speed in the Y direction and the scanning time interval of pixels for one line of the line sensor. It is assumed that there are five pattern rows in this 81.92 mm range as shown in FIG. 9 (C).

Assuming that the input time from one pixel of the CCD line sensor is 0.1 μsec, the first line sensor 10
Is 0.1 μsec × for capturing one line of data
It takes a time of 2048 = 204.8 μsec.

On the other hand, the second line sensor 14 is shown in FIG.
As shown in (C), if only the pattern area with the width W = 1024 μm is imaged, one line is 1024 μm ×
5 = 5120 μm, that is, 10 μm × 512 pixels,
0.1μsec x 5 to capture data for one line
12 = 51.2 μsec is required. Therefore, when the table on which the inspection object is placed is moved at a constant speed in the Y direction, the first
The data for four lines can be captured from the second line sensor 14 within the time for capturing the image data for one line from the line sensor 10. Within a period of time when the image data for one line is captured from the first line sensor 10, Y
When the table is moved by 40 μm in the direction, the table is moved by 10 μm within a time when the image data for one line is taken in by the second line sensor 14. As a result, the resolution of the image data by the first line sensor 10 in the X and Y directions is 40 μm × 40 μm, and the resolution of the image data by the second line sensor 14 in the X and Y directions is 10 μm ×.
It becomes 10 μm. That is, according to the present embodiment, it is possible to perform a highly accurate inspection of a pattern area (area where it is necessary to detect a minute defect) in the same time as an inspection using a low resolution CCD line sensor. It is possible to improve the inspection accuracy without increasing the inspection time.

The above description is an example, and the resolution of the second line sensor 14 is set higher than that of the first line sensor 10 with respect to the resolution in the Y direction, but the resolutions of both line sensors are made equal. (However, in this case, improvement in defect detection accuracy in the Y direction cannot be expected). It is necessary to select appropriate resolutions in the X and Y directions of the first and second line sensors 10 and 14 depending on the pattern size, pattern pitch, and defect detection accuracy of the inspection object.

In the present embodiment, the image data of the entire object to be inspected is fetched by the low-resolution first image pickup device 5, but only the image data of the region other than the pattern region may be fetched. Good. In that case,
As shown in FIG. 9, the optical unit 12 'is newly provided at a position corresponding to the optical unit 12, the first imaging device 5 is provided at a position corresponding to the second imaging device 6, and the optical unit 12' is Only the image of the area other than the pattern area may be configured to enter the first imaging device.

Further, since the optical unit 12 needs to be manufactured according to the pitch, width, etc. of the pattern holes of the inspection object 2, when inspecting a plurality of inspection objects having different pattern hole pitches, widths, etc. As shown in FIG. 10, an assembly 30 in which units 31 to 33 corresponding to the optical unit 12 of FIG. 5 are integrally configured, and a drive device 34 that drives the units 31 to 33 in the Y direction of the drawing are provided, and the units 31 to 33 are provided. The image of the area selected by any of the above may be input to the imaging device 6.

[0023]

As described in detail above, according to the present invention,
Since only the optical signals emitted from the pattern of the object to be inspected and the non-patterned portion (patterned area) near the pattern are selectively incident on the image pickup means, high precision can be achieved only for a portion where a minute defect needs to be detected. Defects can be detected, and the inspection accuracy can be improved without increasing the inspection time.

[Brief description of drawings]

FIG. 1 is a plan view of a pattern inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.

FIG. 3 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 4 is a plan view of an object to be inspected.

FIG. 5 is a diagram showing a part of FIG. 4 in an enlarged manner.

FIG. 6 is a diagram for explaining the operation of the optical unit (12).

FIG. 7 is a block configuration diagram of an image processing unit.

FIG. 8 is a diagram for explaining the acquisition of image data by the imaging device.

FIG. 9 is a plan view of a pattern inspection apparatus according to another embodiment of the present invention.

FIG. 10 is a diagram showing a modification of the optical unit.

FIG. 11 is a diagram showing a configuration of a conventional pattern inspection apparatus.

[Explanation of symbols]

 1 XY table 2 object to be inspected 5 imaging device 6 imaging device

Claims (1)

[Claims] 1. A light source for irradiating an inspected object having a pattern with light, and an image pickup means for receiving a pattern optical signal emitted from the inspected object according to a pattern shape of the inspected object and photoelectrically exchanging the signal. A pattern inspection apparatus comprising: a defect detection unit that detects a defect in the pattern by performing image processing on a photoelectric output from the image capturing unit, wherein the inspection target is between the image capturing unit and the inspection target. 2. A pattern inspection apparatus comprising: an optical selection unit that optically selects only the pattern and the optical signal emitted from the non-patterned portion in the vicinity of the pattern and enters the image pickup unit.