JPH09145629A - Mask inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform automatic inspection with high speed by providing a photodetecting means and a moving means which are provided with a light source and a photomask in between and detects the light that the opening part of the photomask transmits, and a judging means which compares the output of the photodetecting means with a reference value. SOLUTION: A light source 1 illuminates a photomask 5 uniformly. On an X-Y stage 3, a photodetector 2 disposed near the photomask 5 is mounted, and it scans the photomask 5. A signal processing circuit 4 amplifies the output signal of the photodetector 2, shapes the waveform of the signal, and compares it with a reference value set in advance. By this, whether good or bad of the photomask 5 is judged, and the judgment result is displayed on a monitor 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask inspection of a photomask used in a display (LCD, CRT) or the like, which has many simple repeating patterns, among photomasks used in a photoetching technique (photoetching). Regarding the device.

[0002]

2. Description of the Related Art Photo-etching technology (photo etching)
This is a technique of forming a large amount of high-definition patterns by irradiating a thin film of a photosensitive resin with light such as ultraviolet rays through a photomask and utilizing the difference between the light irradiation to the photosensitive resin thin film and the presence or absence of a photochemical reaction. One of the problems of this photo-etching technique is that when foreign matter adheres to or scratches the pattern of the photomask, the defects are also transferred as a pattern to the photosensitive resin thin film, which causes a large number of defects. . Furthermore, as the pattern becomes finer and the possibility of defects due to these defects increases, regular inspection of the photomask,
It is necessary to prevent the occurrence of defects.

The conventional mask inspection apparatus inspects masks of all patterns. Therefore, a reference mask and a mask to be inspected are compared on a one-to-one basis by image recognition, and a difference is detected. A device for detecting a defect in a mask is generally used. For example, there is a technique disclosed in Japanese Patent Laid-Open No. 4-151152.

This type of device has a problem in that the hardware for recognizing a pattern in the details of an image and the software for comparing two patterns become large in scale, and the device becomes expensive. In particular, due to the increasing complexity of optical systems and the increase in processing time for comparison (generally several tens of minutes required) with the recent increase in pattern definition,
It could not be used to inspect mask defects during exposure operations in production.

[0005]

Here, in a photomask in which the same pattern is repeatedly arranged, such as a pixel pattern of a dot matrix type LCD or CRT, attention is paid to the fact that the transmitted light amount of each pixel is the same. While scanning the pixel, if the transmitted light amount of the continuous pattern opening is converted into an electric signal and measured, an abnormal amount of transmitted light of the pattern opening can be obtained with a simple device without requiring complicated processing by software. That is, defects such as foreign matter and scratches on the mask can be detected at high speed.

In view of the above points, the present invention makes it possible to automatically inspect a photomask in which the same pattern is repeatedly arranged at high speed with a simple device during an exposure operation, and a pattern defect due to a mask defect at a production site. It is an object of the present invention to provide a mask inspection device capable of reducing

[0007]

To achieve the above object, a mask inspection apparatus according to claim 1 of the present invention includes a light source for irradiating a photomask with light, and a light source sandwiching the light source and the photomask. And light receiving means for receiving light transmitted through the opening of the photomask, moving means for moving the light receiving means in parallel with the photomask, and output of the light receiving means are preset. It is composed of a determination means for making a comparison with the reference value.

A mask inspection apparatus according to a second aspect of the present invention is arranged such that a light source for irradiating a photomask with light and a position opposed to the light source with the photomask interposed therebetween, and an opening of the photomask is provided. The light receiving means receives the transmitted light, the moving means moves the photomask parallel to the light receiving means, and the determining means compares the output of the light receiving means with a preset reference value.

A mask inspection apparatus according to a third aspect of the present invention is based on the determination result of the determination means, in addition to the means constituting the mask inspection apparatus according to the first or second aspect.
It is characterized by comprising display means for displaying the quality of the photomask.

According to a fourth aspect of the present invention, in addition to the means constituting the mask inspection apparatus according to the third aspect, the mask inspection apparatus specifies the position of the defective portion of the photomask based on a reference point and displays it. The means is provided with a position specifying means for displaying the position of the defective portion.

According to a fifth aspect of the present invention, there is provided a mask inspecting apparatus, wherein in addition to the means constituting the mask inspecting apparatus according to any one of the first to fourth aspects, a light receiving means is a photomask, It is characterized by comprising a pressing means for pressing and a jetting means for jetting a compressed gas from around the light receiving means toward the photomask.

[0012]

1 shows the configuration of a mask inspection apparatus according to an embodiment of the present invention. Photomask 5 with light source 1
Are uniformly illuminated, and the XY stage 3 mounted with the photodetector 2 arranged close to the photomask 5 is scanned along the photomask 5. The signal processing circuit 4 uses the light receiver 2
The output signal of 1 is amplified, shaped, and compared with a preset reference value to determine the quality of the photomask 5, and the monitor 11 displays the determination result.

Next, the case of inspecting the photomask having the pattern shown in FIG. 2 using the mask inspection apparatus of the present embodiment will be described. The light-transmitting portion 7 is aligned with the light-shielding portion 6 and has an opening. The abnormal light-transmitting portion 8 is
The abnormal light transmitting portion 9 is a defect light transmitting portion having a reduced light transmitting area.
Is a defect light-transmitting portion in which the light-shielding portion 6 is scratched and the opening area is enlarged. In an actual dot matrix LCD, there are many cases where a simple pattern is repeated, such that the translucent portions 7 are arranged in a row × vertical direction = 640 × 480.

FIG. 3A is a sectional view of the photomask taken along line AA of FIG. 2, and FIG. 3B is taken along line BB of FIG.
3 is a cross-sectional view of the photomask in FIG. Support glass plate 1
The surface of 0 is coated with a light-shielding portion, and light-transmitting portions are arranged side by side and opened.

The photomask 5 is illuminated by the light source 1 and A
When the light receiver 2 is scanned along -A and BB, an output waveform corresponding to the opening area of each light transmitting portion is obtained. FIG.
(A) is a waveform when scanned along AA,
FIG. 4B shows a waveform when scanning is performed along BB.

If there is no defect in the pattern of the light-transmitting portion, all output waveforms are almost the same, but if the transmission area is reduced due to the adhesion of foreign matter, etc., it will be similar to the waveform in the central portion of FIG. 4 (A). The waveform becomes lower than that of the others, and if the light transmitting portion is enlarged due to a scratch or the like, the waveform becomes higher than the others as shown in the left end of FIG.

When the photodetector 2 is scanned along the entire pattern of the translucent portion in the horizontal or vertical direction of the photomask 5 by the above method, the signal processing circuit 4 causes the magnitude of the output signal of the photodetector 2 to be large. Can be easily identified by comparing with a preset reference value.

When setting the reference value, the reference value M and the reference value N are set based on the size of the light transmitting portion of the photomask, the intensity of the light source, and the sensitivity of the light receiver. However, reference value M> reference value N. If the output signal of the light receiver 2 is larger than the reference value M, it is determined that the light transmitting portion is enlarged due to a scratch or the like, and if the output signal of the light receiver 2 is smaller than the reference value N, foreign matter is attached. It is determined that the area where the light transmitting portion is reduced is defective. If the output signal of the light receiver 2 falls between the reference value M and the reference value N, it is determined as a non-defective product. The distance between the reference value M and the reference value N is determined by the error in the size of the aperture of the light transmitting portion,
Determined by acceptable deposit or scratch size.

Further, the signal processing circuit 4 counts the moving distance from the reference point in the XY plane of the photomask 5 or the number of output waveforms (pulses) when the light receiver 2 is scanned,
The location of the detected defect is specified by any one of the above or a combination thereof, and its position coordinate or pattern number is displayed on the monitor 11.

With this defect position display function, the defective portion on the mask can be easily found, and the contents of the defect can be confirmed, and the operations such as cleaning and repair can be performed easily. This enables mask inspection during the exposure operation, especially when incorporated in a production line, and further enhances the effect of the mask inspection apparatus.

In the present embodiment, there is one light receiver, but in other embodiments, a plurality of light receivers are arranged and used to reduce the number of times of scanning and the scanning time.

In still another embodiment, the light receiver is fixed and the photomask is scanned by the XY stage. As a result, the distance between the light source and the light receiver becomes constant, and the inspection can be performed without being affected by the unevenness of illumination of the light source.

In order to improve the accuracy of defect inspection,
It is desirable that the distance between the photomask 5 and the light receiver 2 be as narrow as possible. However, by narrowing the distance, the light receiver may be affected by a mechanical tilt error between the photomask 5 and the XY stage 3 or a deflection due to the weight of the photomask 5. 2 may come into contact with the photomask 5 and cause scratches.

In order to prevent the occurrence of the above scratches, in another embodiment, a mechanism for pressing the photodetector 2 against the photomask 5 and a jet of compressed gas such as air or nitrogen gas from around the photodetector 2. , A mechanism for separating the light receiver 2 from the photomask 5. The light receiver 2 is pressed against the photomask 5 by a spring, compressed air, or a motor drive, and a compressed gas is ejected from around the light receiver 2. As a result, the light receiver 2 and the photomask 5
As the distance between and becomes narrower, the pressure of the jetted compressed gas becomes stronger and acts so as to separate the two, and as the distance between the light receiver 2 and the photomask 5 becomes wider,
The pressure of the compressed gas that jets out weakens and acts so as to contract between the two. Therefore, by adjusting the force pressing the photodetector 2 against the photomask 5, the distance between the two can be kept constant, and the occurrence of scratches can be prevented.

[0025]

As described above, according to the first aspect of the present invention,
Alternatively, since the mask inspection apparatus according to claim 2 can inspect a photomask for defects at high speed with a low-cost and simple device, it can be incorporated into a production line to prevent pattern defects due to mask defects. it can.

In the mask inspection apparatus according to the third aspect of the present invention, the operator can immediately take appropriate measures by displaying the quality of the photomask on the display means.

In the mask inspection apparatus according to claim 4 of the present invention, by displaying the position of the defective portion of the photomask on the display means, the operator can take appropriate measures corresponding to the defective portion of the photomask. You can

According to the mask inspection apparatus of the fifth aspect of the present invention, by keeping the distance between the photomask and the light receiving means constant, it is possible to perform the defect inspection stably without damaging the photomask.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a mask inspection apparatus of the present invention.

FIG. 2 is a diagram showing a pattern of a photomask.

3A is a sectional view of the photomask taken along the line AA of FIG. 2, and FIG. 3B is a sectional view of the photomask taken along the line BB of FIG.

4A is a waveform when scanned along AA in FIG. 2, and FIG. 4B is a diagram showing a waveform when scanned along BB in FIG.

[Explanation of symbols]

 1 light source 2 light receiver 3 XY stage 4 signal processing circuit 5 photomask 6 light-shielding portion 7 light-transmitting portion 8 abnormal light-transmitting portion 9 abnormal light-transmitting portion 10 supporting glass plate 11 monitor

Claims (5)

[Claims] 1. A light source for irradiating a photomask with light, a light receiving unit arranged at a position opposed to the light source with the photomask interposed therebetween, and receiving light transmitted through an opening of the photomask, the light receiving unit. A mask inspection apparatus comprising: a moving unit that moves the unit in parallel with the photomask; and a determining unit that determines and compares the output of the light receiving unit with a preset reference value. 2. A light source that irradiates a photomask with light, a light receiving unit that is disposed at a position facing the light source with the photomask sandwiched therebetween, and receives light that has passed through an opening of the photomask. A mask inspection apparatus comprising: a moving unit that moves a mask in parallel with the light receiving unit; and a determining unit that compares and determines the output of the light receiving unit with a preset reference value. 3. The mask inspection apparatus according to claim 1, further comprising display means for displaying the quality of the photomask based on the determination result of the determination means. 4. The mask inspection apparatus according to claim 3, further comprising position specifying means for specifying the position of the defective portion of the photomask based on the reference point and displaying the position of the defective portion on the display means. . 5. A photomask, comprising: a pressing means for pressing the light receiving means against the photomask; and a jetting means for jetting a compressed gas from around the light receiving means toward the photomask. Item 5. The mask inspection apparatus according to any one of items 4.