JP2880721B2 - Defect inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a defect inspection apparatus for inspecting a pattern defect of an inspection object on which a parallel pattern is formed.

(Prior Art) As an object to be inspected having a parallel pattern formed thereon, there is, for example, a Nessa glass panel for a dot matrix liquid crystal display (hereinafter abbreviated as a panel). Further, pattern defects such as pinholes (hereinafter abbreviated as defects) may be formed. Accordingly, inspection for such defects is performed. FIG. 6 is a configuration diagram of such a defect inspection apparatus. In FIG. 1, reference numeral 1 denotes a panel. The panel 1 is formed by etching a Nesa film pattern 3 on a Nesa glass substrate 2, and the Nesa glass substrate 2 is formed as a parallel pattern by forming the Nesa film pattern 3. Have been. By the way, among the pattern defects, a short is a portion shown in FIG. 4 where the pattern portion of the Nesa glass substrate 2 is interrupted and the Nesa film pattern 3 is connected.
The pinhole is a portion shown in FIG. 5 where the Nesa film 3 is erroneously etched. In order to detect a defect, the panel 1 is irradiated with a laser beam and scanning is performed in the direction of the arrow (a). At this time, when the laser beam is applied to the short 4 and the pinhole 5, scattered lights 6 and 7 are generated in the short 4 and the pinhole 5. However, these scattered lights 6, 7 are detected by the optical sensor 8 to detect a defect. In this case, since the spatial light intensity distribution of the scattered light of the defect-free portion of the normal pattern and the scattered light of the defect have different directions, the optical sensor 8 detects only the scattered light at the defect. It is oriented in the direction to be.

FIG. 7 shows a defect inspection apparatus to which image processing is applied. The panel 1 is irradiated with uniform light from an illumination device 9. Then, the television camera 10 is arranged in the direction of the specularly reflected light from the panel 1, and the panel 1 is imaged. Then, the image signal output from the television camera 10 is sent to the image processing device 11, and the image processing device 11 compares the input Nesa film pattern with the input image to detect a defect.

However, the above-described devices have the following problems. That is, small scratches and foreign substances that do not become defects are present on the panel 1. Therefore, when these scratches and foreign matter are irradiated with laser light by the apparatus shown in FIG. 6, scattered light is generated as well as defects. Then, when the light intensity of the scattered light is high, it is detected as a defect although it need not be detected as a defect. For this reason, it is not possible to distinguish a flaw or a foreign substance from a defect, and the reliability of the defect inspection is low.

Although the television camera 10 is used in the apparatus shown in FIG. 7, the television camera 10 has a narrow dynamic range with respect to the light intensity. For this reason,
Unless the size of one pixel of the television camera 10 is smaller than the size of the minimum defect to be detected on the image data, it becomes difficult to detect the defect. Therefore,
When the size of the panel 1 is large and the defect is small,
The time required for defect detection of the entire panel becomes longer.

(Problems to be Solved by the Invention) As described above, it is difficult to detect a flaw or a foreign substance that does not become a defect as a defect, or to detect a small defect.

Therefore, an object of the present invention is to provide a highly reliable defect inspection apparatus capable of reliably detecting only a defect without being affected by a scratch or a foreign substance that does not become a defect.

[Means for Solving the Problems] The present invention relates to a defect inspection apparatus for inspecting a pattern defect of a test object on which a parallel pattern is formed, wherein the defect width is equal to the gap width between the patterns of the test object. A laser scanning means for scanning a laser beam having a diameter equal to or greater than this width in parallel to the pattern of the object to be inspected, and receiving the specularly reflected light from the object to be inspected to reduce the intensity of the received light. An optical sensor that converts the signal into a corresponding electrical signal; an amplifying unit that amplifies a high-frequency component of the electrical signal from the optical sensor; and a pattern defect that receives the electrical signal from the amplifying unit and determines the light intensity of the specularly reflected light. And a defect detection device for detecting the defect.

(Operation) With the provision of such a means, a laser beam having a diameter equal to or greater than the gap width between the patterns of the test object is applied to the pattern of the test object by the laser scanning means. The optical sensor receives the specularly reflected light from the test object at this time and sends an electric signal corresponding to the light intensity to the amplifying means, where the high frequency component is amplified. Then, the defect detecting means receives the electric signal from the amplifying means, determines the light intensity of the specularly reflected light, and detects a pattern defect.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a configuration diagram of a defect inspection apparatus. In the figure
Reference numeral 20 denotes a laser oscillator. A beam expander 21 is arranged in the laser output direction of the laser oscillator 20 so that the beam diameter of the laser light output from the laser oscillator 20 is enlarged. Also, this beam expander 21
A beam scanner 22 is arranged in the beam output direction, and a condenser lens 23 is arranged in the beam scanner direction of the beam scanner 22. Here, the diameter of the laser beam Q irradiated onto the panel 1 is formed to be equal to or larger than the gap width between the patterns. The scanning direction of the laser beam Q by the beam scanner 22 is parallel to the parallel pattern formed on the panel 1 as shown in FIG.

On the other hand, an optical sensor 25 is disposed in the specular reflection direction of the laser beam Q of the panel 1 through a condenser lens 24. The optical sensor 25 outputs an electric signal corresponding to the light intensity of the received laser beam. The electric signal is sent to a defect detection device 27 through an amplifier 26. In addition, this amplifier
26 has a high-pass filter function. That is, since the period during which the laser beam Q passes through the defect is extremely short, the electric signal indicating the defect when passing through the defect has a high frequency. Therefore, the amplifier 26 is set so as to amplify a frequency equal to or higher than the frequency f corresponding to the defect as shown in FIG. The defect detection device 27 is an optical sensor
Receive the electric signal from 25 and judge the light intensity of the specularly reflected light,
It has a function of detecting a defect from the light intensity.

Next, the operation of the apparatus configured as described above will be described.

When the laser light is output from the laser oscillator 20, the diameter of the laser light is expanded by the beam expander 21 and sent to the beam scanner 22. The laser beam Q is scanned by the beam scanner 22 in parallel to the parallel pattern of the panel 1, and is focused by the condenser lens 23 to a diameter equal to or larger than the gap width between the patterns. Irradiated on top. Then, the specularly reflected light from the panel 1 is condensed by the condensing lens 24 and irradiated on the optical sensor 25. The optical sensor 25 outputs an electric signal corresponding to the light intensity of the received specularly reflected light. This electric signal passes through the amplifier 26, in which only the high-frequency component is amplified and passed to the defect detection device 27. by the way,
As shown in FIG. 2, the electric signal from the optical sensor 25 when the laser beam Q passes through the scanning position s1 is shown in FIG.
As shown in the figure, the open defect 28 where the Nesa film pattern 3 is separated
The level decreases when passing through (a1), and also decreases when passing through the pinhole 5 (a2). The optical sensor 25 when the laser beam Q passes through the scanning position s2
The electric signal from is short-circuited as shown in FIG.
The level rises when passing through (a3). Therefore, the defect detection device 27 determines that the light intensity of the specular reflection light has decreased due to the decrease in the level of the electric signal from the optical sensor 25 and that the light intensity of the specular reflection light has increased due to the increase in the electric signal level. . Then, the defect detection device 27 determines the allowable level range of the normal portion of the electric signal level and the optical sensor 25.
The respective defects 4, 5, and 28 are detected by comparing the electric signal level with the electric signals.

By the way, as shown in FIG. 5, when there is a scratch 29 or a foreign substance 30 which is not regarded as a defect on the panel 1, scattered light is generated at the scratch 29 or the foreign substance 30 by the irradiation of the laser beam Q. Since the gap width between the patterns is equal to or larger than the gap width, the scattered light from the flaw 29 and the foreign matter 30 smaller than the gap width does not change the light intensity of the regular reflection light.

As described above, in the above-described embodiment, the laser beam Q formed to have a diameter equal to or larger than the gap width between the patterns of the panel 1 is scanned in parallel to the pattern, and the panel at this time is scanned. The regular reflection light is received by the optical sensor 25 and the pattern defect is detected from the light intensity. Therefore, a slight change in the light intensity of the regular reflection light can be detected, and a very small defect such as a short circuit of about 2 μm can be detected. Can be detected. In addition, even if there are small scratches 29 and foreign substances 30 that do not become defects, these scratches 29 and foreign substances 30 are not erroneously detected as defects. In addition, since the laser beam is formed to have the same or larger gap width between the patterns, the time required for defect inspection of the entire panel 1 can be reduced.

Further, since the electric signal from the optical sensor 25 is amplified by the amplifier 26 to amplify the high-frequency component and sent to the defect detection device 27, it corresponds to a defect when the laser beam Q having an extremely small beam diameter passes through the defect in a very short time. To detect high-frequency components and detect defects with high accuracy.

The present invention is not limited to the above-described embodiment, and may be modified without departing from the gist thereof. For example,
The object to be inspected is not limited to the panel 1 but can be inspected as long as a parallel pattern is formed of substances having different reflectances.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to provide a highly reliable defect inspection apparatus capable of detecting a defect with high accuracy without being affected by a scratch or a foreign substance that does not become a defect.

[Brief description of the drawings]

1 to 5 are views for explaining one embodiment of a defect inspection apparatus according to the present invention, wherein FIG. 1 is a configuration diagram, FIG. 2 is a diagram showing laser beam scanning, and FIG. Is a diagram showing characteristics of a high-pass filter function of the amplifier, FIG. 4 is a schematic diagram of an electric signal when a defect is detected, FIG. 5 is a diagram showing scattered light of a portion that does not become a defect, FIG. 6 and FIG. FIG. 7 is a block diagram of the prior art. DESCRIPTION OF SYMBOLS 1 ... Panel, 2 ... Nesa glass substrate, 3 ... Nesa film pattern, 4 ... Short, 5 ... Pinhole, 20 ... Laser oscillator, 21 ... Beam expander, 22 ... Beam scanner, 23, 24 ... Condenser lens, 25 ... Optical sensor, 2
6 ... Amplifier, 27 ... Defect detection device, 28 ... Open defect.

Claims (1)

(57) [Claims] 1. A defect inspection apparatus for inspecting a pattern defect of an inspection object on which a parallel pattern is formed, wherein the inspection device is formed to have a size equal to or larger than a gap width between patterns of the inspection object. Laser scanning means for scanning a laser beam in parallel with the pattern of the object to be inspected; and an optical sensor for receiving specularly reflected light from the object to be inspected and converting the light into an electric signal corresponding to the light intensity of the received light Amplifying means for amplifying a high-frequency component of the electric signal from the optical sensor; and a defect detecting means for receiving the electric signal from the amplifying means and judging the light intensity of the regular reflected light to detect the pattern defect. A defect inspection apparatus, comprising: