JPH01219836A - Mask for projected print - Google Patents

Abstract

PURPOSE:To retain flatness of a transparent thin film facing a mask pattern and to inspect a foreign material precisely even when atmospheric pressure fluctuates by imparting a transparent substrate and placing thin films, thinner than a transparent thin film, which is placed on the wall surface of a frame bonding said thin film. CONSTITUTION:The title mask is equipped with the transparent substrate, and the thin films 12, windows are provided on the wall surfaces of the frame 11 adhering to the transparent thin films thereon at intervals, and they have the thin films 12 which are thinner than the transparent thin film. Even when the title mask is brought to a point of 2,000m is altitude and left as it is for one week, the thin films 12 expand prior to the transparent thin film because they are thinner, and weaker in tension, than the transparent thin film. Consequently the transparent thin film merely expands to outside. This phenomenon is the more remarkable and effective, as the difference of film thickness between the thin films 12 stretched in the frame 11 and the transparent thin film facing the transparent substrate becomes greater. Accordingly, the thin films 12 are better to be thinner so far as they endure a certain extent of tension. Thus, the transparent thin film facing the transparent substrate of the mask for a projected print retains its flatness against the fluctuation of atmospheric pressure, and a user recognizes debris adhering to the title mask precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention - numerically relates to an optical pattern mask;
More specifically, the present invention relates to patterned mask structures that avoid the printing of undesirable deposit particles.

[Conventional technology]

In the manufacture of integrated circuits, various devices and circuit connections are formed using photoresist masks that cover the semiconductor substrate excluding areas where etching or metallization is desired. protect the area of

Photoresist 1--The mask is formed by coating a substrate with a resist layer and then exposing the resist layer according to the pattern through ultraviolet light through the openings of the patterned mask. The light beam hardens the resist l~ layer in the irradiated area in the case of negative resists and degrades in the case of positive resists. This uncured or degraded area is then removed by a developer source that exposes a portion of the substrate, for example for a metallization process.6 Typically, the patterned mask has one surface coated with, for example, silver or It is formed of a transparent substrate with a pattern of chromium opaque areas formed thereon.

Conventionally, several types of resist printing methods have been used, but the most popular method is a reduction projection exposure method. This mask image is, for example, 5 to 20 times larger than the image formed on the substrate. This makes mask formation and inspection easier because the image is larger.

This also has the advantage that even if there is a dimensional error in the mask, the dimensional error is reduced when it is formed on the substrate, so that the error in the mask can be almost ignored. On the other hand, one drawback recognized with the projection exposure method is that
Even particles that accumulate in the transparent areas of the patterned surface of the mask are precisely focused on the plane of the substrate with optimal resolution and contrast, so that large particle images are printed onto the resist layer. This is a problem in systems that reduce image size because the relative size of the mask area is very large. This increases the likelihood that resized deposits large enough to be printed will be deposited on transparent areas of the mask pattern even in a clean room environment.

A method for avoiding printing such dust particles has been proposed in Japanese Patent Publication No. 54-28716 and the like. This involves gluing transparent thin film covers onto the surface of the mask at intervals of several cities, protecting the pattern from damage and dust, and also protecting the outer surface of the cover to the order of tens of microns. The dust is kept out of focus so that no image of the dust particles is printed when the pattern is printed on the photosensitive substrate.

[Problem to be solved by the invention]

However, in the case of the method of preventing dust transfer as described above, in order to prevent the transfer of large dust as much as possible, it is necessary to increase the distance between the mask and the transparent thin film, which makes transporting the mask difficult. There were problems such as the mask storage case becoming huge and the mask storage area expanding. Furthermore, if the distance between the mask and the transparent thin film is kept to a certain level, it is necessary to control dust that is large enough to cause defects due to transfer. A numerical method for this management is a method in which a laser beam is barely incident on the surface of a transparent thin film, and if there is dust, the scattered light is received and recognized. In this case, when the air sealed between the transparent thin film and the mask expands or contracts due to changes in atmospheric pressure, the ability to detect dust decreases. In other words, when it expands, it recognizes it as garbage even though there is no garbage there, and conversely, when it contracts, it does not recognize it even though there is garbage.

The present invention is intended to solve these problems.The purpose of the present invention is to keep the transparent thin film facing the mask pattern flat even when the atmospheric pressure fluctuates, so that foreign object inspection can be performed accurately. It is to do so.

[Means to solve the problem]

The projection printing mask according to the present invention is a projection printing mask in which a transparent thin film is provided at intervals on at least one surface of a transparent substrate on which a pattern having an opaque area and a transparent area is formed. A window is provided on the wall surface of the frame to which the substrate and the transparent thin film are bonded, and the window has a thin film thinner than the transparent thin film.

〔Example〕

Examples of the present invention will be shown below in comparison with conventional examples.

In a laboratory at an altitude of 100 m, adhesive is applied to a transparent thin film on a transparent substrate. In other words, two square transparent substrates of -13aa are prepared, and one is coated with plastic as shown in Figure 2. Frame 21 (Thickness: 3, Width: 7, Long side: 12
(2) Glue the short sides (10CXI) with adhesive so that there are no gaps. On the other sheet, as shown in Figure 1, the long side of the frame is 10 (2) x 50111, and the short side is 80
A single window in the X5 state is provided, and a thin film 12 having a thickness of 0.2 microns is adhered thereto so as not to sag, and is then adhered to a transparent substrate with an adhesive so that there is no gap. Here, the thin film 12 does not need to be transparent, but may be made of polyoxyethylene terephthalic acid, which is commercially available under the trade name Mylar.
Membranes of polymers such as nitrosululose and parylene are suitable. Then the thickness 2 of said two frames 21.11
With enough tension to not tear the micron transparent RJ film,
Glue. This transparent iM is made of mylar, which is the same material as the thin film 12 described above.

〔Effect of the invention〕

The two transparent substrates described above were taken to a point at an altitude of 2000 m and left for one week. As a result, the transparent thin film facing the transparent substrate on which the window was provided and the thin film was stretched remained flat, but the transparent thin film on the side where the window was not provided on the frame remained flat.
It expanded about 2 degrees. This is because due to the drop in atmospheric pressure, the pressure of the air sealed between the transparent substrate and the transparent thin film became higher than the external pressure, so the transparent thin film expanded outward until it became equal to the tension of the transparent thin film. On the other hand, if a window is provided in the frame and a thin film is stretched, this thin film is thinner than the transparent thin film and has weaker tension, so it expands preferentially than the transparent thin film, and as a result, the transparent thin film It almost never swells outward.

This phenomenon is more pronounced and effective as the difference in thickness between the thin film stretched on the frame and the transparent thin film facing the transparent substrate is larger. Therefore, the thin film stretched on the frame can withstand a certain amount of tension. As for thickness, the thinner the better.

Experimental research has shown that a uniform film of at least 0.2 microns or more can withstand atmospheric pressure fluctuations as in the example. In addition, the thickness of the transparent thin film facing the transparent substrate should be such that it does not substantially affect the optical path of the projection device, and the thicker the better. A shift of this magnitude only causes a shift of 0.4 microns l~, which is not a problem with the reduction projection exposure method. The thickness of the transparent thin film can be 2 microns or more, and the difference can be up to 1.8 microns or more. By further investigating and optimizing films of other polymers, this difference can be made even greater, and thus is an object of the present invention. This improves the effect of preventing the transparent thin film facing the transparent substrate from expanding or contracting due to changes in atmospheric pressure.

In addition, in the embodiment, an example was shown in which the air pressure in the sealed air is higher than the external pressure, but it goes without saying that the same effect can be obtained when the air pressure is lower than the external pressure.

As described above, the present invention maintains the flatness of the transparent thin film facing the transparent substrate of the projection printing mask against atmospheric pressure fluctuations, making it possible to accurately recognize attached dust.
As a result, it is possible to improve the yield.

[Brief explanation of the drawing]

FIG. 1 is a projected view of a frame for bonding a transparent substrate and a transparent thin film of a projection printing mask according to an embodiment of the present invention, and FIG.
A projection view of a processing example of a frame for bonding a transparent substrate and a transparent thin film of a conventional projection printing mask is shown. 11.21...Frame 12...Thin film or above, Ying A-eup 2nd hard

Claims (1)

[Claims] In a projection printing mask in which transparent thin films are provided at intervals on at least one surface of a transparent substrate on which a pattern having opaque areas and transparent areas is formed, the transparent substrate and the transparent thin film are bonded. A mask for projection printing, characterized in that a window is provided on a wall surface of a frame, and the window has a thin film thinner than the transparent thin film.