JPH03210561A - Pellicle for lithography - Google Patents

Abstract

PURPOSE:To obtain the pellicle for lithography which can be used in a short wavelength region as well by using a prurane compd. film or film mixture composed of the prurane compd. and polyhydric alcohol compd. CONSTITUTION:The prurane compd. film or the film mixture composed of the prurane compd. film and the polyhydric alcohol compd. is used as the pellicle for dustproofing in an exposing system using substantially <=500nm light. Namely, the prurane compd. film or the film mixture composed of the prurane compd. film and the polyhydric alcohol compd. allows the good transmission of <=500nm light and does not generate absorption ends even in the short wavelength region of 210 to 400nm. The pellicle for lithography in the short wavelength region is obtd. in this way.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a pellicle for lithography, particularly a 500nu pellicle used in manufacturing semiconductor devices such as LSI and VLSI, or liquid crystal display boards. The present invention relates to a dust prevention pellicle for lithography in an exposure method using the following light.

(Prior art) In the production of LSI, VLSI semiconductor devices, liquid crystal display boards, etc., patterning is created by irradiating light onto semiconductor wafers or liquid crystal original plates. If this dust is attached, this dust absorbs light or bends the light, causing the transferred buttering to become deformed, the edges to become rough, and even the white background to become black and dirty, resulting in poor dimensions. This results in disadvantages such as damage to product quality and appearance.

For this reason, this type of work is usually carried out in a clean room, but since it is difficult to keep the exposure master always clean even in this clean room, it is necessary to install exposure light on the surface of the exposure master to prevent dust. A method has been adopted in which a pellicle is attached that allows the passage of light through the membrane, and a thin film of nitrocellulose, cellulose acetate, or the like is used as the pellicle.

(The problem that the invention aims to solve) However, pellicles made of nitrocellulose, cellulose acetate, etc. have a large absorption edge in the short wavelength range of 210 to 400 nm, are unstable, and yellow during use. In order to change the wavelength range of 210 nm, such as excimer laser or i-line ultraviolet rays, semiconductor devices are used during device manufacturing.
There is a disadvantage that it cannot be used for lithography such as ultra-LSIs that perform exposure at ~400 nm or high-density fine liquid crystal display boards, but the emergence of pellicles for lithography that can also be used in such short wavelength ranges. is required.

(Means for Solving the Problems) The present invention solves such disadvantages and relates to a pellicle for lithography, which is substantially 500nm.
In an exposure method using light of m or less, a pullulan compound film or a mixed film of a pullulan compound and a polyhydric alcohol compound is used as a dust-repelling pellicle.

That is, as a result of various studies by the present inventors in order to develop a pellicle for lithography that can be used in a short wavelength range,
When a pullulan compound membrane or a mixed membrane of a pullulan compound and a polyhydric alcohol compound was used in place of the conventionally known nitrocellulose or cellulose acetate,
It easily passes light of 0nm or less, and 210 to 400n
Since no absorption edge occurs even in the short wavelength range of 50 m,
We have discovered that it is useful as a pellicle for lithography in a short wavelength range of 0 nm or less, and we have disclosed the shape and structure of a pullulan compound film or a mixed film of a pullulan compound and a polyhydric alcohol compound as the pellicle, and a method for producing the same.
The present invention was completed by conducting research on the types of pullulan compounds and polyhydric alcohol compounds.

(Function) As described above, the pellicle for lithography of the present invention uses a pullulan compound film or a mixed film of a pullulan compound and a polyhydric alcohol compound. After suitably dissolving the mixture in a solvent such as cyclohexane, N,N-dimethylformamide, acetone, etc., this solution is molded by a solution caster method using a spin coater or knife coater, or the pullulan compound or It can be produced by molding a mixture of a pullulan compound and a polyhydric alcohol compound into a film-like material using a known method such as melt extrusion using a T-die method, an inflation method, or the like.

The pullulan compound used here is a type of natural polysaccharide, and it contains alkyl groups such as methyl groups and ethyl groups, hydroxyalkyl groups such as hydroxyethyl groups, hydroxypropyl groups, and dihydroxypropyl groups, acetyl groups, and propionyl groups. The polyhydric alcohol compound used here may be a derivative substituted with an acyl group, etc., or one in which part or all of the hydroxyl group has been chemically modified. Hydrolic alcohols, such as polyvinyl alcohol, vinyl ether/vinyl alcohol copolymer, ethylene/vinyl alcohol copolymer, vinyl acetate/vinyl alcohol copolymer, or those in which some or all of the hydroxyl groups of these have been chemically modified and substituted. Any material that has film forming ability may be used, but pullulan is preferred because it provides good light transmittance in the short wavelength region such as 210 to 400 nm, moisture resistance, and sufficient film temperature. Alternatively, it is preferable to react a polyhydric alcohol with acrylonitrile to cyanoethylate some or all of its hydroxyl groups. Note that the mixing ratio when mixing this pullulan compound and polyhydric alcohol compound may be within an arbitrary range.

In addition, the thickness of this pullulan compound film or mixed film of pullulan compound and polyhydric alcohol compound is preferably 0.5 μm or more in order to provide mechanical strength. Even when the surface is treated with an anti-reflection film to allow UV rays to pass through, the thickness is 30 mm.
It is desirable that the thickness be 0 μm or less.

The pullulan compound film or the mixed film of a pullulan compound and a polyhydric alcohol compound according to the present invention has high ultraviolet transmittance and can also transmit light in the short wavelength range of 210 to 400 nm, so it can be used as a pellicle for lithography in the short wavelength range. In this case, it is preferable to use it by adhesively fixing it to a frame made of aluminum or the like.

(Example) Next, examples of the present invention will be given.

Example 1. Comparative Example A 5% acetone solution of cyanoethyl pullulan whose viscosity at 20°C of a 20% dimethylformamide solution is 300 cp was cast onto a smooth glass plate using a knife coater with a clearance of 50 μl, dried at room temperature for 24 hours, and then cast at 60°C. It was dried for 2 hours at 100° C. for 1 hour.

Next, this cyanoethyl pullulan thin film was adhered to the end face of an aluminum frame with an inner diameter of 130 mm coated with an epoxy adhesive, Araldite Rapid [part name manufactured by Showa Kobunshi Co., Ltd.], and after curing for 1 hour, the entire glass plate was bonded. I immersed it in water and took out the film that naturally peeled off from the 5-minute diameter glass plate. After air-drying it, I cut off the part of the film that protruded from the outside of the aluminum frame.
A thin film having a uniform tension and a thickness of 1.3 μm was obtained as a pellicle for lithography.

Next, when we examined the light transmittance of this thin film, it showed a transmittance of 90% or more in the 240-500n hazy wavelength range, and it was 436n 98.8% for 365n I-line, 98.6% for 249n excimer laser.
It shows a transmittance of 2%, and the transmittance at 210n is 88
%, and it was confirmed to be an excellent pellicle because it did not yellow during use.

However, for comparison, nitrocellulose HIG-20
A pellicle for lithography with a thickness of 1.4 μm obtained by processing in the same manner as above except that an ethyl acetate solution of [part name manufactured by Asahi Kasei Industries, Ltd.] was used had a g-line transmittance of 97.9 at 436 μm. %, the transmittance of the 385 nm i-line was 97.5%, but the transmittance of the 249 nm excimer laser was 4.
It was low at 1.1% and could not be used as a pellicle because it yellowed during use of i-line.

Example 2 Pullulan 50% by weight and polyvinyl alcohol 50% by weight
The mixture was completely cyanoethylated using acrylonitrile to make a 5% solution of methyl ethyl ketone, which was cast onto a smooth glass plate using a knife coater with a clearance of 1 mm, dried at 40°C for 24 hours, and then cast at 70°C for 4 hours. The film was dried at 100° C. for 2 hours, and then immersed in water to allow the film to peel off naturally to form a film with a thickness of 240 μm.

Next, this film body is adhered to the end face of the aluminum using an epoxy adhesive (described above) so that it is smooth, and the part that protrudes outside the aluminum frame is cut off to create a pellicle for lithography, and this film transmits light. When I checked the rate, it was 90 in the wavelength range of 240 to 500 na+.
% or more, and with anti-reflection treatment on both sides of the film, the 436nm G-line is 95.0%, and the 365nm G-line is 95.0%.
The 249 nm excimer laser showed a light transmittance of 94.3%, and the 249 nm excimer laser showed a light transmittance of 90.8%.This laser also has sufficient mechanical strength, and the pellicle does not yellow during use. .

Example 3 A mixture of 40% by weight of pullulan and 60% by weight of partially saponified polyvinyl alcohol (degree of saponification 80%) was cyanoethylated in the same manner as in Example 2 to prepare a 5% dimethylformamide solution, and this was used to conduct the experiment. A pellicle for lithography with a thickness of 1.5 μm was made in the same manner as in Example 1, and the light transmittance of this material was examined, and it was found to be 260~
It shows a transmittance of 90% or more in the wavelength range of 500 nm, and has anti-reflection treatment on both sides of the film), 98.0% for the G-line of 436nL, 97.3% for the I-line of 365nl,
It is 90.6% with a 249nm excimer laser, which also means that the pellicle does not yellow during use.
It was confirmed that it is an excellent pellicle for lithography.

(Effects of the Invention) As described above, the pellicle for lithography of the present invention uses a pullulan compound film or a mixed film of a pullulan compound and a polyhydric alcohol compound as a dust-repelling pellicle. It has a high light transmittance for ultraviolet light in the short wavelength range of 500 nm and does not yellow during use, so it can be used as a pellicle for exposure of large-scale integrated circuits such as LSI and VLSI, or ultra-fine liquid crystal display board circuits. It is said to be useful, and furthermore, because of its excellent light transmittance, it can be expected to shorten the exposure time and improve the strength of the pellicle film by increasing the thickness.

Claims (1)

[Scope of Claims] 1. A pellicle for lithography, characterized in that a pullulan compound film or a mixed film of a pullulan compound and a polyhydric alcohol compound is used as a dust-repelling pellicle. 2. The pellicle for lithography according to claim 1, wherein the pullulan compound is cyanoethyl pullulan. 3. The pellicle for lithography according to claim 1, wherein the polyhydric alcohol is cyanoethyl polyvinyl alcohol.