JP2000305255A - Pellicle for fluorine excimer laser lithography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pellicle for lithography having high light transmittance to fluorine excimer laser and such light resistance that the pellicle withstands practical use by using a specified amorphous fluorine-containing copolymer as the material of a pellicle film. SOLUTION: An amorphous fluorine-containing copolymer obtained by copolymerizing a fluorine-containing radical polymerizable monomer mixture including 70-100 mol% perfluoro-2,2,-dimethyl-1,3-dioxol is used as the material of a pellicle film. Tetrafluoroethylene, trifluoroethylene, difluoroethylene, vinylidene fluoride or hexafluoropropylene may be used as a fluorine-containing radical polymerizable monomer copolymerizable with the perfluoro-2,2,- dimethyl-1, 3-dioxol but tetrafluoroethylene is preferably used. The preferred content of the perfluoro-2,2,-dimethyl-1,3-dioxol in the mixture is 85-100 mol%.

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 fluorine excimer laser lithography having excellent light transmittance to fluorine excimer laser light and realizing high resolution.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of semiconductor devices such as LSIs and VLSIs, or liquid crystal display panels, semiconductor wafers or liquid crystal original plates are irradiated with light to perform patterning. If dust adheres, the dust absorbs or reflects light, so the transferred pattern may be deformed or edges may be roughened, resulting in loss of dimensions, quality, appearance, etc. There has been a problem that the performance of the device and the liquid crystal display panel and the production yield are lowered.

[0003] For this reason, these operations are usually performed in a clean room. However, it is difficult to keep the exposure master clean at all times even in this clean room. A method of attaching a pellicle that allows it to pass well is used. According to this method, dust does not directly adhere to the surface of the exposure original plate but adheres to the pellicle film.Therefore, if the focus is adjusted on the pattern of the exposure original plate during lithography, the dust on the pellicle becomes out of focus and is transferred. It has no effect on the patterned pattern.

Conventionally, these pellicles are formed by coating a transparent pellicle film made of nitrocellulose, cellulose acetate, a fluoropolymer, or the like, which allows light to pass through well, onto a pellicle frame made of aluminum, stainless steel, or the like with a good solvent for the pellicle film. And then air-dry and adhere (JP-A-58-219
No. 023) or bonded with an adhesive such as an acrylic resin, an epoxy resin or a fluororesin (US Pat.
No. 402, JP-B-63-27707, JP-A-7-16
No. 8345), an adhesive layer made of a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin or the like is provided below the pellicle frame, and a release layer (separator) for protecting the adhesive layer is adhered. It is configured.

[0005]

In recent years, the demand for the resolution of lithography has been gradually increased, and in order to realize the resolution, light having a gradually shorter wavelength has been used as a light source. Specifically, ultraviolet light [g-line (436 nm), I-ray (365 nm)] has now shifted to far ultraviolet light [KrF excimer laser (248 nm)], and vacuum ultraviolet light [ArF excimer] will be used in the near future. Lasers (193 nm)] have been used, and it is highly likely that a fluorine excimer laser (158 nm) will be used in the future in order to achieve higher resolution.

[0006] The material of the pellicle film for the KrF excimer laser and the ArF excimer laser is, as an amorphous fluorine-containing polymer containing an ether bond, a polymer of perfluorobutenyl vinyl ether or less than 70 mol% of perfluoro- 2,2-dimethyl-1,3-dioxole and 30 mol
% Or more, such as a copolymer with tetrafluoroethylene. These amorphous fluorine-based copolymers have high transmittance in a wavelength region of 193 nm or more, and have light resistance that can withstand practical use even when irradiated with a KrF excimer laser or an ArF excimer laser.

However, these have low transmittance to the fluorine excimer laser light, and have been difficult to put to practical use. Until now, a pellicle for fluorine excimer laser lithography, which has a high transmittance with respect to irradiation of a fluorine excimer laser and has light resistance that can endure practical use, has not yet been known.

In view of this situation, the inventor has conducted intensive studies on a pellicle for lithography which has a high light transmittance with respect to a fluorine excimer laser (wavelength: 158 nm) and has light resistance that can withstand practical use and completed the present invention. did.

[0009]

That is, the present invention provides 70 to 10
Fluorine excimer using an amorphous fluorine-based copolymer obtained by copolymerizing a fluorine-containing radically polymerizable monomer mixture containing 0 mol% of perfluoro-2,2-dimethyl-1,3-dioxole as a pellicle film raw material This is a pellicle for laser lithography.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The inventors have conducted intensive studies on the light transmittance of the pellicle film for fluorine excimer laser lithography in order to solve the above-mentioned problems, and found that perfluoro-2,2-dimethyl-1,3
-Amorphous fluorinated polymer consisting of dioxole polymer or amorphous consisting of copolymer of fluorinated radical polymerizable monomer mixture containing at least 70% of perfluoro-2,2-dimethyl-1,3-dioxole It has been found that a pellicle film made of a porous fluorine-based copolymer as a raw material shows a high transmittance to fluorine excimer laser light. Using this pellicle film, they found that a pellicle for lithography exhibiting a high transmittance to a fluorine excimer laser beam could be obtained, and completed the present invention.

In the present invention, the fluorine-containing radically polymerizable monomer copolymerizable with perfluoro-2,2-dimethyl-1,3-dioxole includes tetrafluoroethylene,
Trifluoroethylene, difluoroethylene, vinylidene fluoride, hexafluoropropylene and the like can be used, and among them, tetrafluoroethylene is particularly preferred. The content of perfluoro-2,2-dimethyl-1,3-dioxole in the fluorine-containing radical polymerizable monomer mixture is 7
If the amount is less than 0 mol%, the transmittance of the pellicle for fluorine excimer laser lithography containing this as a pellicle film raw material to the fluorine excimer laser light decreases, so that 70 to 100 mol% is required, but it is more preferable.
85 to 100 mol%. In the present invention, the case where the content of perfluoro-2,2-dimethyl-1,3-dioxole is 100 mol% is a homopolymer.

In the present invention, a conventionally known method can be applied to a method for obtaining a pellicle film using an amorphous fluorine-based copolymer as a raw material. This can be obtained, for example, by dropping an amorphous fluorine-based copolymer solution on a smooth substrate, homogenizing the solution by spin coating, evaporating the solvent, and peeling the thin film from the substrate. In the present invention, if the thickness of the pellicle film is less than 0.1 μm, the strength is insufficient, while 10 μm
If the thickness is larger than m, the light transmittance may decrease. Therefore, the thickness is preferably in the range of 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

FIG. 1 is a sectional view of an example of a pellicle for fluorine excimer laser lithography of the present invention. The configuration of the pellicle for fluorine excimer laser lithography of the present invention will be described below. As shown in FIG. 1, the pellicle for fluorine excimer laser lithography of the present invention comprises a pellicle film (1), a pellicle frame (3), an adhesive layer (2) and an adhesive layer (4). To the substrate for use (5) via the pressure-sensitive adhesive layer (4). The pellicle film (1) is made of the amorphous fluorine-based copolymer of the present invention, and the pellicle frame (3) is made of conventionally known aluminum, stainless steel or the like. The adhesive layer (2) and the pressure-sensitive adhesive layer (4) may be made of any material that can bond the pellicle film (1) and the pellicle frame (3) and the exposure substrate (5) and the pellicle frame (3). The adhesive layer (2) is preferably made of an adhesive such as an acrylic resin, an epoxy resin or a fluororesin, and the adhesive layer (4) is made of a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin, or the like. Adhesives are preferred. The substrate for exposure (5) is called by a name such as a reticle and a photomask, but may be any substrate that is generally used for lithography.

As described above, the pellicle for fluorine excimer laser lithography of the present invention exhibits an excellent transmittance to a fluorine excimer laser beam. Therefore, the energy given to the substrate, for example, a silicon wafer at the time of exposure increases, which is advantageous in terms of energy.

Further, the pellicle for fluorine excimer laser lithography of the present invention exhibits a high transmittance even when irradiated with a fluorine excimer laser beam, which was impossible in the past, and does not impair the transmittance. Persistence, and therefore long pellicle life. From the above, the pellicle for fluorine excimer laser lithography of the present invention is extremely useful.

Examples of the present invention will be described below, but the present invention is not limited to these.

EXAMPLES Example 1 85 mol% of perfluoro-2,2-
A copolymer of dimethyl-1,3-dioxole and 15 mol% of tetrafluoroethylene was converted to a fluorinated solvent, IL-263.
[Tokuyama Co., Ltd.] to give a 2% by weight solution. Next, this solution was dropped onto a silicon substrate whose surface was polished, the substrate was rotated using a spin coater, and then the substrate was heated at 180 ° C. for 10 minutes to form a transparent film having a thickness of 1 μm. Next, the thin film was peeled off from the silicon substrate to form a pellicle film. Next, a fluororesin adhesive, Cytop CTX-A (trade name, manufactured by Asahi Glass Co., Ltd.) is applied to the upper end surface of the aluminum pellicle frame, and a silicone resin adhesive, X-40-3004A [ Shin-Etsu Chemical Co., Ltd. product name]. Next, the pellicle film was attached to the upper end surface of the pellicle frame, and unnecessary films were cut along the outer periphery of the pellicle frame to complete the pellicle for lithography. The transmittance of the obtained pellicle for lithography to a fluorine excimer laser beam was 93%. Example 2 The same perfluoro-2,2-dimethyl-1,3-dioxole polymer as in Example 1 was dissolved in a fluorine-based solvent (described above) to obtain a 1% by weight solution. Next, this solution was dropped on a silicon substrate whose surface was polished, the substrate was rotated using a spin coater, and then the substrate was heated at 180 ° C. for 10 minutes to form a 1 μm-thick transparent film. Next, the thin film was peeled off from the silicon substrate to form a pellicle film. Next, in the same manner as in Example 1, a pellicle for lithography was completed. When the transmittance of the obtained pellicle for lithography to a fluorine excimer laser beam was measured, it was 95%.

Comparative Example 1 65 mol% of perfluoro-2,
A copolymer of 2-dimethyl-1,3-dioxole and 35 mol% of tetrafluoroethylene was dissolved in a fluorinated solvent (described above) to obtain a 5% by weight solution. Next, this solution was dropped on a silicon substrate whose surface was polished, the substrate was rotated using a spin coater, and then the substrate was heated at 180 ° C. for 10 minutes to form a transparent film having a thickness of 1 μm. Next, the thin film was peeled off from the silicon substrate to form a pellicle film. Next, in the same manner as in Example 1, a pellicle for lithography was completed. 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 [trade name, manufactured by Asahi Glass Co., Ltd.] was dissolved in a fluorinated solvent (described above) to prepare a 5% by weight solution. Next, this solution was dropped on a silicon substrate whose surface was polished, and the substrate was rotated using a spin coater,
Next, the substrate was heated at 180 ° C. for 10 minutes to form a transparent film having a thickness of 1 μm. Next, the thin film was peeled off from the silicon substrate to form a pellicle film. Next, in the same manner as in Example 1, a pellicle for lithography was completed. When the transmittance of the obtained pellicle for lithography to a fluorine excimer laser beam was measured, it was 2%.

[0019]

[Table 1]

As is clear from the results shown in Table 1,
A pellicle formed of a pellicle film using an amorphous fluorine-containing copolymer as a raw material, which has been conventionally used, has a low transmittance with respect to a fluorine excimer laser beam, and has been difficult to put into practical use. However, from 70 to 100 mol% of perfluoro-
A pellicle consisting of a pellicle film made of an amorphous fluorine-based copolymer obtained by copolymerizing a fluorine-containing radically polymerizable monomer mixture containing 2,2-dimethyl-1,3-dioxole is a fluorine excimer laser beam. Also showed very high transmittance. Therefore, it was found that the pellicle for fluorine excimer laser lithography of the present invention has sufficient practicality.

[0021]

According to the present invention, an amorphous fluoropolymer obtained by copolymerizing a fluorine-containing radically polymerizable monomer mixture containing 70 to 100 mol% of perfluoro-2,2-dimethyl-1,3-dioxole. By using a pellicle composed of a pellicle film made of a copolymer, fluorine excimer laser lithography can be put to practical use for the first time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a pellicle for fluorine excimer laser lithography of the present invention.

[Explanation of symbols]

 (1) pellicle film, (2) adhesive layer, (3) pellicle frame, (4) adhesive layer, (5) substrate for exposure.

Claims (2)

[Claims] An amorphous fluorine-based copolymer obtained by copolymerizing a fluorine-containing radically polymerizable monomer mixture containing 70 to 100 mol% of perfluoro-2,2-dimethyl-1,3-dioxole. Pellicle for fluorine excimer laser lithography as a pellicle film material. 2. The pellicle for fluorine excimer laser lithography according to claim 1, wherein the content of perfluoro-2,2-dimethyl-1,3-dioxol in the fluorine-containing radical polymerizable monomer mixture is 85 to 100 mol%. .