JPS6047740B2 - X-ray exposure mask and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photomask for X-ray exposure and a method for manufacturing the same.

The X-ray exposure process is characterized by the fact that there is no generation of secondary electrons or scattering due to dust, which are problems in conventional electron beam exposure processes, and a fine resist pattern with a high aspect ratio can be obtained.

FIG. 1 is a diagram showing the principle of an X-ray exposure apparatus. That is, it is basically divided into an X-ray generating section 1 and a sample chamber 2, and both chambers are separated by a beryllium window 3, so that the X-ray generating section 1 is always kept in a vacuum and the target 4 is not contaminated. There is.

In the X-ray generation chamber 1 in the figure, an electron beam 6 generated from an electron gun 5 collides with a target 4, and the
Line 7 occurs.

The X-rays 7 entering the sample chamber 2 through the beryllium window 3 pass through an X-ray exposure mask 8 and are deposited on a substrate 9 to be processed. The X-ray resist 10 is selectively irradiated. Here, the X-ray exposure mask 8 includes a frame 21, a tap run (supporting film) 2, as shown in detail in FIG.
2 and an X-ray absorber 23.

Conventionally, a rigid thin film such as silicon (Si) or silicon nitride (Si, No) has been used as the tap run 22. However, when exposure processing is performed using a tap run made of these rigid thin films, if the substrate to be processed is warped due to heat treatment during the manufacturing process, the mask and the substrate to be processed do not come into perfect contact, causing transfer distortion. However, accurate exposure processing was not possible. Therefore, it was proposed to use a plastic film such as polyimide as a membrane.

This structure has the advantage that not only can the mask and the substrate to be processed be brought into perfect contact with each other, but also optical alignment can be performed because the plastic film is transparent. The frame of an X-ray exposure mask in which the membrane is made of a plastic film is generally made of stainless steel or Pyrex glass.

However, although stainless steel has good processing accuracy, it has a thermal expansion coefficient of 10 x 10-6/°C, which makes it difficult to perform exposure processing on a silicon substrate (thermal expansion coefficient of 2 x 10-5/°C). , the temperature difference is large, and there is a temperature difference between the time of manufacturing the X-ray exposure mask by electron beam exposure and the time of X-ray exposure processing using the X-ray exposure mask, or if there is a long-term X-ray exposure. Sometimes, when temperature changes occur, misalignment occurs between the X-ray exposure mask and the substrate to be processed.
It is inappropriate for microfabrication.

For example, when performing an exposure process on a silicon substrate with a diameter of 100C, if the temperature difference during the process is 2 degrees Celsius, the maximum positional deviation will be about 1.6 microns. Further, although Pyrex glass has a coefficient of thermal expansion of -3.times.10@-3 / DEG C., which is close to that of silicon, it has the disadvantage that it is difficult to improve its processing accuracy.

In other cases, silicon alone is used for the frame, but it has the disadvantage of being relatively brittle.

The present invention is directed to such a conventional X-ray exposure mask. The present invention aims to provide an X-ray exposure mask that eliminates the drawbacks of the X-ray exposure mask and allows exposure processing to be performed with higher precision.

The present invention also provides a manufacturing method that can easily form the X-ray exposure mask. Therefore, according to the present invention, there is provided an X-ray exposure mask characterized in that a material having substantially the same coefficient of thermal expansion as the substrate to be processed is used as the core material of the mask frame. Further, according to the present invention, a mold having a flat central part and a substantially U-shaped groove on the periphery is prepared, and after the core material is placed in the groove of the mold, the central part of the mold is flat. A step of forming a resin layer in the ridge portion and the surrounding groove, and then removing the mold to form an X-ray absorber support membrane and a frame integrally molded at the end of the X-ray absorber support membrane. A method for manufacturing an X-ray exposure mask is provided.

That is, the present invention uses a material having almost the same coefficient of thermal expansion as the substrate to be processed as the core material of the frame of the X-ray exposure mask, and eliminates the temperature difference between mask manufacturing and transfer, or the long-term This is an attempt to solve the problem of positional deviation due to mask temperature changes during X-ray exposure.

l Another feature is that the plastic ●mask●frame is produced from a mold at the same time as membrane production, and the usual frame bonding process can be omitted.

Next, the present invention will be explained in detail using examples. A specific embodiment of the present invention has a manufacturing process shown in FIG.
This will be explained in more detail.

In this example, polyimide was used as the plastic material for the membrane, and silicon (Si) was used as the core material of the mask frame. First, as shown in FIG. 3a, a mold 33 made of metal or glass is prepared which has a flat central portion 31 and a groove 32 having a U-shaped cross section at the peripheral edge. Next, as shown in FIG. 3B, a core material 34 made of silicon is placed in the groove 32 of the mold 33.

At this time, the core material 34 is accommodated in a state floating above the groove bottom by a plurality of protrusions (not shown) provided at the groove bottom. Next, a monomer solution is spin-coated onto the mold 33 to cover the core material 34 in the groove 32 and to form a monomer film 35 on the central flat portion 31. This state is shown in figure c. Next, heat treatment is performed to convert the monomer film 35 into polyimide, and then the mold 33 is removed.

This state is shown in Figure d. Next, polyimide film 36
An electron beam resist layer is formed on one surface of the electron beam resist, a desired pattern is exposed to light on the electron beam resist, and a resist pattern 37 is formed by performing a phenomenon treatment.

This state is shown in figure e. Thereafter, a film 38 of an X-ray absorber such as gold (Au) is selectively applied to the surface of the polyimide film 36 that is not covered with the resist pattern 37 by a plating method or a combination of a vapor deposition method and a lift-off method. Form.

This state is shown in figure f. As a result, the X-ray exposure mask according to the present invention having the structure shown in FIG. 3f is completed.

Here, the mold 33 can be removed by applying a mold release agent to the inner surface of the mold 33 in advance and releasing the mold, or by etching the mold 33 itself. That is, the mold 33 is made of glass or aluminum (A1) as described above.
), copper (Cu), etc., the mold can be removed with hydrofluoric acid or the like without etching the polyimide film. According to the present invention, there is provided an X-ray exposure mask in which the core material of the frame has substantially the same coefficient of thermal expansion as the substrate to be processed. Therefore, the X by electron beam exposure
Even if there is a temperature difference between the time of manufacturing the radiation exposure mask and the time of X-ray exposure processing using the X-ray exposure mask, or even if a temperature change occurs during the X-ray exposure processing, The X-ray exposure mask and the substrate to be processed expand and contract by approximately the same amount, and there is no risk of misalignment of the exposure pattern.

Moreover, since the core material of the frame is fixed and formed at the same time as the membrane is formed, the manufacturing process can be simplified, and
The mechanical strength can be further increased as a mask for line exposure.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the general structure of the X-ray exposure device, Figure 2
The figure is a cross-sectional view showing the general structure of an X-ray exposure mask used in the X-ray exposure apparatus, and FIG. 3 is a process cross-sectional view showing the manufacturing process of the X-ray exposure mask according to the present invention.

Claims (1)

[Claims] 1. In an X-ray exposure mask having an X-ray absorber film selectively formed on a film that transmits X-rays, the core material is made of silicon, and the covering layer of the core material is made of silicon. An X-ray exposure mask characterized in that it is a plastic mask frame made of polyimide integrally molded with the film. 2. A core material made of Si of a mask frame is housed and arranged in a groove having a flat central part and a projection provided at the peripheral edge and the bottom of the groove, with the core material made of Si of the mask frame floating above the bottom of the groove by the projections. Step: Spinning a plastic film forming solution onto the mold, filling the groove and covering the core material, and forming a film on the central flat part, followed by heat treatment to form a plastic film made of polyimide. forming a plastic mask frame, the core material of which is coated with polyimide, and removing the plastic film from the mold;
A method for manufacturing an X-ray exposure mask, comprising the step of selectively forming an X-ray absorber film on the surface of the plastic film made of the polyimide.