JP2000338650A - Pellicle for lithography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pellicle for lithography having a high light transmittanace to fluorine excimer laser. SOLUTION: The pellicle is obtained using an amorphous fluorine-containing polymer as the material of a pellicle film. The amorphous fluorine-containing polymer is a polymer of a perfluorodioxol compound of the formula or a copolymer of a fluorine-containing radical polymerizable monomer mixture containing >=20 mol% perfluorodioxol compound. In the formula, R1 and R2 are each F or a 1-10C perfluoroalkyl and R3 and R4 are each F or a 1-10C perfluoroalkoxy but at least one of R3 and R4 is a 1-10C perfluoroalkoxy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pellicle for lithography, and more particularly to a pellicle for lithography realizing excellent light transmittance and high resolution with respect to a fluorine excimer laser beam.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of semiconductor devices such as LSIs and VLSIs, and liquid crystal display panels, patterning is performed by irradiating a semiconductor wafer or a liquid crystal original plate with light. If it adheres, the dust absorbs and reflects light, so the transferred pattern is deformed and edges are roughened, resulting in impaired dimensions, quality, appearance, etc. As a result, semiconductor devices and liquid crystal displays There was a problem that the performance of the plate and the production yield were reduced.

[0003] For this reason, the patterning work is usually performed in a clean room, but it is difficult to always keep the exposure original plate clean even in the clean room. In order to prevent contaminants such as dust from adhering to the surface of the exposure master,
A pellicle is provided as a protective film. When a pellicle is installed, contaminants do not directly adhere to the surface of the exposure master,
If the pellicle film is focused on the pattern of the exposure original during lithography, the contaminants on the pellicle will be out of focus and have no relation to the transfer of the pattern.

In a conventional pellicle, a transparent pellicle film made of nitrocellulose, cellulose acetate, or a fluoropolymer having excellent light transmittance is adhered to an upper part of a pellicle frame made of aluminum, stainless steel, or the like. A good solvent for the pellicle film or an adhesive such as an acrylic resin, an epoxy resin or a fluororesin is used (see US Pat. No. 4,861,402, Japanese Patent Publication No. 63-27707). JP, JP-A-7-168345). On one side of the pellicle frame, an adhesive layer made of a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin or the like, and a release film (separator) for protecting the adhesive layer are adhered.

[0005]

In recent years, the resolution of lithography has been gradually increased, and light with a gradually shorter wavelength has been used as a light source in order to realize a higher resolution. Specifically, conventional ultraviolet light [g
Line (436 nm) and i-line (365 nm)], but now it has shifted to far-ultraviolet light (KrF excimer laser (248 nm)), and in the future, vacuum ultraviolet light (ArF excimer laser (193 nm)) will be used. In the near future, to achieve higher resolution, a fluorine excimer laser (158 nm)
Is likely to be used.

When a KrF excimer laser or an ArF excimer laser is used, a pellicle film material may be a perfluorobutenyl vinyl ether polymer or a perfluoro-2,2-dimethyl polymer as an amorphous fluorine-based polymer having an ether bond. Copolymers of -1,3-dioxole and tetrafluoroethylene and the like have been proposed. Since these amorphous fluoropolymers show high transmittance to irradiation light in the wavelength range of 193 nm or more, they are practically used as pellicle film materials for pellicles for lithography using KrF excimer laser and ArF excimer laser. It is considered possible.

However, since the above materials have low transmittance to fluorine excimer laser light, pellicles for fluorine excimer laser lithography have not been put to practical use until now. The present invention has been made in view of such circumstances, and has as its object to provide a pellicle for lithography having a high light transmittance to a fluorine excimer laser.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies on the light absorption of the pellicle film material constituting the pellicle for lithography, and as a result, have found that the weight of the perfluorodioxole compound is high. Amorphous fluorine-based copolymer consisting of a copolymer or a fluorine-containing radical copolymerizable monomer mixture containing a perfluorodioxole compound in an amount of at least 20 mol% is a fluorine excimer. The inventors have found that they exhibit high transmittance to laser light, and have completed the present invention.
That is, the present invention relates to a pellicle for lithography using an amorphous fluoropolymer as a material of a pellicle film, wherein the amorphous fluoropolymer is a perfluorodioxole compound represented by the following structural formula (Formula 2) Or a copolymer of a fluorine-containing radical polymerizable monomer mixture containing at least 20 mol% of the perfluorodioxole compound.

Embedded image ^(R 1, ^{R 2} is selected from perfluoroalkyl groups consisting of fluorine atoms, or 1 to 10 carbon ^{atoms, R} 3,
R ⁴ is selected from a fluorine atom or a perfluoroalkoxy group having 1 to 10 carbon atoms, and at least one of R ³ and R ⁴ is a perfluoroalkoxy group)

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an example of the pellicle for lithography of the present invention. As shown in this figure, the pellicle for lithography of the present invention is composed of a pellicle film 1, an adhesive layer 2, a pellicle frame 3, and an adhesive layer 4, and is adhered to an exposure substrate 5 via the adhesive layer 4. To use. The pellicle film 1 contains a predetermined amorphous fluorine-containing polymer, that is, a polymer of a perfluorodioxole compound represented by the following structural formula (Chemical Formula 3) or a polymer containing 20 mol% or more of the perfluorodioxole compound. It consists of a copolymer of a fluorine radical polymerizable monomer mixture. In the following structural formula (Formula 3), R ¹ and R ² are selected from a fluorine atom or a perfluoroalkyl group having 1 to 10 carbon atoms. Examples of the perfluoroalkyl group include a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group, a perfluorooctyl group, a perfluorononyl group, and a perfluorodecyl group. You. R ¹ , R
² is preferably a fluorine atom or a trifluoromethyl group, and particularly preferably a fluorine atom. R ³ and R ⁴ are each a fluorine atom or a group having 1 to 10 carbon atoms.
Selected from perfluoroalkoxy groups consisting of Examples of the perfluoroalkoxy group include a trifluoromethoxy group, a perfluoroethoxy group, a perfluoropropoxy group, a perfluorobutoxy group, a perfluoropentoxy group, a perfluorohexoxy group, a perfluoroheptoxy group, a perfluorooctoxy group, a perfluorononyloxy group, and a perfluorononyl group. A desyloxy group is exemplified, and R ³ and R ⁴ are particularly preferably a fluorine atom or a trifluoromethoxy group. In order to make the obtained fluoropolymer amorphous, at least one of R ³ and R ⁴ needs to be a perfluoroalkoxy group, but preferably one is a perfluoroalkoxy group. Most preferred as the perfluorodioxole compound is 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole.

Embedded image

Examples of the fluorine-containing radically polymerizable monomer mixture to be copolymerized with the perfluorodioxole compound include at least one of tetrafluoroethylene, trifluoroethylene, difluoroethylene, vinylidene fluoride, and hexafluoropropylene. However, tetrafluoroethylene is particularly preferred. If the content of the perfluorodioxole compound in the fluorine-containing radically polymerizable monomer mixture is less than 20 mol%, the transmittance to the fluorine excimer laser light decreases,
Although 20 mol% or more is required, it is preferably 35 mol% or more, and more preferably 50 mol% or more. In addition,
The copolymerization of the fluorine-containing radically polymerizable monomer mixture containing the perfluorodioxole compound in an amount of 20 mol% or more may be performed according to a conventional method.

The pellicle film 1 can be prepared using the above-mentioned amorphous fluoropolymer by a generally known method. For example, an amorphous fluoropolymer solution can be formed on a smooth substrate. Is dripped and made uniform by a spin coating method, and then
There is a method in which a solvent is evaporated and a pellicle film is formed by peeling a thin film from a substrate. The thickness of the pellicle film 1 is 0.
If the thickness is less than 1 μm, the strength is insufficient.If the thickness is more than 10 μm, the transmittance of light may decrease.
m, especially 0.5 μm to 5 μm
The range of m is preferred.

For the adhesive layer 2, an adhesive such as an acrylic resin, an epoxy resin, or a fluororesin is used. The pellicle frame 3 is made of aluminum, stainless steel, or the like. Adhesive layer 4
For example, an adhesive such as a polybutene resin, a polyvinyl acetate resin, an acrylic resin, or a silicone resin is preferable. Further, the substrate for exposure 5 may be any one provided for lithography such as a reticle and a photomask.

[0013]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. (Example 1) A copolymer of 85 mol% of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole and 15 mol% of tetrafluoroethylene was mixed with a fluorinated solvent, IL-2.
63 (manufactured by Tokuyama Corporation, trade name) to give a 5% by weight solution. Next, the solution was dropped on a silicon substrate whose surface was polished, and the substrate was rotated using a spin coater. Then, the substrate was heated at 180 ° C. for 10 minutes to form a transparent thin film having a thickness of 1 μm. Was. Then, the transparent thin film was peeled off from the substrate to produce a pellicle film. Next, apply a fluororesin adhesive / Cytop to the upper end surface of the aluminum pellicle frame.
CTX-A (trade name, manufactured by Asahi Glass Co., Ltd.) was applied, and a silicone resin adhesive X-40-3004A (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the lower end surface. Then, the pellicle film was adhered to the upper end surface of the pellicle frame, and unnecessary films were cut along the outer periphery of the pellicle frame to produce a pellicle for lithography. The transmittance of the obtained pellicle for lithography to fluorine excimer laser light was 92%.

Example 2 A polymer of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole was dissolved in a fluorinated solvent, IL-263 (trade name, manufactured by Tokuyama Corporation). 3
% Solution. Next, the solution was dropped on a silicon substrate whose surface was polished, and the substrate was rotated using a spin coater, and then the substrate was heated at 180 ° C. for 10 minutes to form a transparent thin film having a thickness of 1 μm. . Then, the transparent thin film was peeled off from the substrate to produce a pellicle film. Hereinafter, a pellicle for lithography was produced in the same manner as in Example 1. The transmittance of the obtained pellicle for lithography to a fluorine excimer laser beam was 95%.

Example 3 50 mol% of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole and 50 mol%
ALGOFL copolymer with mol% tetrafluoroethylene
Dissolve ON AD (Audimont, Italy, trade name) in fluorinated solvent, IL-263 (Tokuyama, trade name)
A 6% by weight solution was obtained. Next, this solution was dropped on a silicon substrate whose surface was polished, and the substrate was rotated using a spin coater. Then, the substrate was heated at 180 ° C. for 10 minutes,
A transparent thin film having a thickness of 1 μm was formed. Then, the transparent thin film was peeled off from the substrate to produce a pellicle film. Less than,
A pellicle for lithography was produced in the same manner as in Example 1. The transmittance of the obtained pellicle for lithography to a fluorine excimer laser beam was 89%.

Comparative Example 1 65 mol% of perfluoro-2,2
-A copolymer of dimethyl-1,3-dioxole and 35 mol% of tetrafluoroethylene was dissolved in a fluorinated solvent, IL-263 (trade name, manufactured by Tokuyama Corporation) to prepare a 5% by weight solution. Next, the solution was dropped on a silicon substrate whose surface was polished, and the substrate was rotated using a spin coater.
The substrate was heated at 180 ° C. for 10 minutes to form a 1 μm-thick transparent thin film. Then, the transparent thin film was peeled off from the substrate to produce a pellicle film. Hereinafter, a pellicle for lithography was produced in the same manner as in Example 1. The transmittance of the obtained pellicle for lithography to a fluorine excimer laser beam was 58%.

(Comparative Example 2) A polymer of perfluorobutenyl vinyl ether, Cytop CTX-S (trade name, manufactured by Asahi Glass Co., Ltd.) was dissolved in a fluorinated solvent, IL-263 (trade name, manufactured by Tokuyama Corp.) % Solution. Next, the solution was dropped on a silicon substrate whose surface was polished, and the substrate was rotated using a spin coater.
By heating for 1 minute, a transparent thin film having a thickness of 1 μm was formed. Then, the transparent thin film was peeled off from the substrate to produce a pellicle film. Hereinafter, a pellicle for lithography was produced in the same manner as in Example 1. The transmittance of the obtained pellicle for lithography to fluorine excimer laser light was 2%.

As is apparent from the above results, the pellicle using the pellicle film made of the amorphous fluorine-containing (co) polymer, which has been conventionally used, has a transmittance to the fluorine excimer laser beam. It was found that practical application as a pellicle for fluorine excimer laser lithography was difficult. On the other hand, it was found that the pellicle for lithography of the present invention has a high transmittance to fluorine excimer laser light, and is sufficiently practical as a pellicle for fluorine excimer laser lithography.

[0019]

According to the pellicle for lithography of the present invention,
Since it shows an excellent transmittance to a fluorine excimer laser beam, energy applied to a substrate such as a silicon wafer at the time of exposure is increased, and the transmittance is not impaired for a long time. In addition, since little light is absorbed, the light resistance is also excellent. Therefore, the present invention is extremely useful as a pellicle for lithography using a fluorine excimer laser, which has been difficult to put into practical use conventionally.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a pellicle for lithography.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pellicle film 2 Adhesive layer 3 Pellicle frame 4 Adhesive layer 5 Exposure substrate

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 2H095 BA07 BC33 4J100 AC22Q AC24Q AC25Q AC26Q AC27Q AR32P BB07P BB18P CA01 CA04 DA62 JA32 JA43

Claims (3)

[Claims] 1. A pellicle for lithography using an amorphous fluoropolymer as a material of a pellicle film,
The amorphous fluorine-based polymer may be a polymer of a perfluorodioxole compound represented by the following structural formula (Formula 1) or a fluorine-containing radical polymerizable monomer mixture containing the perfluorodioxole compound in an amount of 20 mol% or more. A pellicle for lithography, which is a polymer. Embedded image ^(R 1, ^{R 2} is selected from perfluoroalkyl groups consisting of fluorine atoms, or 1 to 10 carbon ^{atoms, R} 3,
R ⁴ is selected from a fluorine atom or a perfluoroalkoxy group having 1 to 10 carbon atoms, and at least one of R ³ and R ⁴ is a perfluoroalkoxy group) 2. The method of claim 1, wherein the perfluorodioxole compound is 2,2,4-trifluoro-5-trifluoromethoxy-
The pellicle for lithography according to claim 1, which is 1,3-dioxole. 3. The pellicle for lithography according to claim 1, which is a pellicle for fluorine excimer laser lithography.