JPH0262542A - Pellicle for excimer laser lithography - Google Patents

Abstract

PURPOSE:To execute good lithography by using an SiO2 film as a pellicle for preventing dust in an exposing system using excimer laser light (175 to 300nm wavelength). CONSTITUTION:The SiO2 film as the pellicle has adequately 1 to 5mum film thickness in terms of strength and light transmittance. For example, the SiO2 films are formed on both surfaces of an Si single crystal substrate by passing SiH4 and N2O on the Si substrate and subjecting the same to a plasma treatment. The SiO2 on the rear surface is partly subjected to dry etching by CF4/O2, etc., and thereafter, the substrate is immersed into a soln. mixture composed of HNO3, HF, and NaNO2 to selectively etch the Si substrate, by which the self-standing SiO2 film on the front surface is easily stably formed. The resulted thin SiO2 film has high UV transmittance and allows the good transmission of the excimer laser light having 175 to 300nm.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a pellicle for excimer laser lithography,
In particular, the present invention relates to a dust-preventing pellicle for excimer laser lithography in an exposure method using excimer laser light used when manufacturing semiconductor devices such as LSI and VLSI.

(Conventional technology) Conventional LS 1. In the manufacturing of VLSI semiconductor devices, semiconductor wafers are irradiated with light to create patterns, but if there is dust attached to the exposure plate used in this case, this dust will absorb the light. Otherwise, the transferred patterning may be deformed due to the bending of the light, the edges may become rough, and the white background may become black and smeared, resulting in a disadvantage that the dimension quality and appearance are impaired.

For this reason, this type of work is usually carried out in a clean room, but even within this clean room it is difficult to keep the exposed original plate clean at all times.

This method involves attaching a thin film such as nitrocellulose or cellulose acetate, which allows the exposure light to pass easily, as a pellicle to the surface of the exposure plate to prevent dust. Because a large absorption edge appears in a short wavelength region such as 150 to 300 nm, there is a disadvantage that it cannot be used when using excimer laser lithography with a wavelength of 175 to 300 nm for exposure of semiconductor devices. There is a need for the advent of pellicles for laser lithography.

(Structure of the Invention) The present invention relates to a pellicle for excimer laser lithography that solves the disadvantages of the conventional example. It is characterized by being used as a shielding pellicle.

That is, as a result of various studies aimed at developing a pellicle for excimer laser lithography, the present inventors used a silicon oxide film as a pellicle in place of the conventionally known nitrocellulose and cellulose acetate. - 150-30 to allow light to pass through well
We discovered that it is useful as a pellicle for excimer laser lithography because it does not produce a large absorption edge even in the short wavelength range of 0 nm, and we have learned about the shape, structure, and manufacturing method of the silicon oxide thin film used as this pellicle. The present invention was completed by conducting research on the following.

The silicon oxide as the percle used in the present invention may be in the form of a thin film, which has a thickness of 0.5 μm.
It becomes more itchy and the membrane strength is insufficient when it is formed into a membrane.
If it becomes thicker than 10μ, the light transmittance will decrease, so 0.
It is necessary to have a thickness in the range of 5 to 10 .mu.m, and the preferred range is 1 to 5 .mu.m.

In addition, this silicon oxide thin film can be made by the well-known plasma CVD method or high frequency magnetron sputtering method, so it is possible to make this by flowing SiH4 gas and N20 gas onto a substrate such as silicon single crystal, and then plasma After forming a silicon oxide (SiOW) film on both sides of the Si crystal by CVD, a part of the SiO□ on the back side is dry etched with CF4102, etc., and then HNO, HF, NaN0.(7) Mixed liquid dipped shite S
By selectively etching the i-substrate, a self-supporting film of SiO2 on one surface can be easily and stably obtained.

The silicon oxide thin film obtained in this way has high ultraviolet transmittance and easily passes excimer laser light with a wavelength of 175 to 3.0 On+*, so it is considered to be particularly useful as a pellicle for excimer laser lithography. Ru.

Next, examples of the present invention will be given.

Example 1 4-inch silicon substrate 10 with a thickness of 400tim
0> side, S i H420C,C,,N,0 2,0
ooc, c, and subjected to plasma CVD to a thickness of 2μ
-, a film was formed.

The flatness (BOW) of this silicon substrate is S
The residual stress of SiO,lli was measured before and after the i O,@ formation, and it was found to be a tensile stress of 3.3 x 109 dynes/d.

Furthermore, after forming a 2" thick Sin film on the back surface of this silicon substrate using the same method as above,
F, dry etching with 10a to create a 50 mm square opening in the center of the SiO□ film on the back side, and then dry etching with 95a+Q
of HNO3 (65%), 5 mQ of HF (40%) and 1
g of NaN0. A silicon substrate was selectively etched by immersing it in a mixed solution.

A self-supporting SiO film with a diameter of 50 m and a thickness of 2t1M was obtained.

When I investigated the ultraviolet transmittance of the following items, I found that
The results shown in the figure are obtained, and the height is 5+m,
A pellicle was made by gluing and reinforcing aluminum with a wall thickness of 2 mm and a diameter of 60 m as shown in Figure 2. This pellicle was 92 mm thick with KrF excimer laser light (249 mm).
% transmittance.

Example 2 The SiH N, O gas in Example 1 was replaced with SiH42
0C,C,,0,20C,C was treated in the same manner as in Example 1, except that the surface of the silicon substrate had a thickness of 0.
A 511M SiO2 film was formed.

Next, a SiO□ film with a thickness of 0.5p was formed on the back surface of this silicon substrate in the same manner as described above, and then treated in the same manner as in Example 1 to form a SiO□ film with a thickness of 0.51p and the film to be self-supporting. When a film was made and the ultraviolet transmittance of this material was measured, the results shown in Fig. 1 were obtained, and a pellicle made from this in the same manner as in Example 1 was 74% irradiated with ArF excimer laser light (193 + an). It showed a transmittance of .

Example 3 On the silicon substrate used in Example 1, S i , H
,2QCoC,,0,50C,C, was flowed, a high frequency of 13.56 MHz was applied to the knee, and a 5 μm thick SiO2 film was formed on the knee using high frequency magnetron sputtering. , the residual reaction of the film is 1. due to tensile stress. It was 1×10′ dynes/d.

Next, a SiO□ film with a thickness of 5p is formed on the back surface of this silicon in the same manner as described above, and the following treatment is performed in the same manner as in Example 1 to form a self-supporting film of a SiO□ film with a thickness of 5−1. The transmittance was measured.

The results shown in FIG. 1 were obtained, and a pellicle prepared using the same method as in Example 1 exhibited a transmittance of 48% with ArF excimer laser light (193 nm).

[Brief explanation of the drawing]

FIG. 1 is a graph showing the ultraviolet transmittance of a silicon oxide thin film as a pellicle of the present invention, FIG. 2 is a longitudinal cross-sectional view showing the structure of the oxygen silicon thin film pellicle of the present invention, and FIG. It is a graph showing the light transmittance of a cellulose pellicle. 7゜1-◆Additional length (nm) Fig. 1 Fig. 2 Al1 tube Fig. 3

Claims (1)

[Scope of Claims] 1. A pellicle for excimer laser lithography, characterized in that a silicon oxide film is used as a dust-proof pellicle in an exposure method using excimer laser light. 2. The pellicle for excimer laser lithography according to claim 1, wherein the silicon oxide film has a thickness of 0.5 to 10 μm. 3. The pellicle for excimer laser lithography according to claim 1, wherein the excimer laser light has a wavelength of 175 to 300 nm.