JP2001066760A - Pellicle for lithography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pellicle for lithography comprising a high performance pellicle film will not photodegrade or photolyze, even when it is irradiated with vacuum ultraviolet light of short wavelength over a long time, has a long service life and high transmittance and undergoes no change with the lapse of time. SOLUTION: Pellicle for lithography with vacuum ultraviolet light is obtained using a transparent fluoropolymer, consisting of only carbon and fluorine atoms as a film material. The transparent fluoropolymer contains a cyclic part comprising a perfluoroalkyl group of a formula (where 1<=n<=10, 10<=m<=10,000, and 10<=p<=10,000).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention requires a pellicle for lithography, that is, a pellicle for lithography used as a dust remover for manufacturing semiconductor devices such as LSIs and VLSIs or liquid crystal display panels, and particularly requires a high resolution. The present invention relates to a pellicle for lithography used for vacuum ultraviolet light exposure used in exposure.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of semiconductor devices such as LSIs and VLSIs or liquid crystal display panels, patterning is performed by irradiating a semiconductor wafer or a liquid crystal master plate with light. If there is dust on the surface, the dust will absorb light or reflect light, so the transferred pattern will be deformed,
There is a problem in that the edges are roughened, dimensions, quality, appearance, etc. are impaired, and the performance and manufacturing yield of semiconductor devices and liquid crystal display panels are reduced.

[0003] For this reason, these operations are usually performed in a clean room. However, it is difficult to keep the exposure master clean even in this clean room, so that light for exposure to remove dust is well transmitted to the surface of the exposure master. A method of attaching a pellicle to be made has been performed. In this case, the dust does not directly adhere to the surface of the exposure master, but adheres to the pellicle film.Therefore, if the focus is set on the pattern of the exposure master during lithography, the dust on the pellicle becomes independent of transfer. There is.

As shown in FIG. 1, for example, a pellicle film 1 made of nitrocellulose, cellulose acetate, fluoropolymer, or the like, which transmits light well, is provided with a pellicle frame made of aluminum, stainless steel, polyethylene, or the like. A good solvent for the pellicle film is applied to the upper part of the film 2 and air-dried for adhesion (JP-A-58-21902)
No. 3) and bonded with an adhesive such as an acrylic resin, an epoxy resin or a fluoropolymer (US Pat. No. 48
No. 61402, JP-B-63-27707,
An adhesive layer 3 made of a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin, or the like, and a release layer 4 (separator) for protecting the adhesive layer are adhered to a lower portion of the pellicle frame (see JP-A-7-168345). It is configured.

[0005]

In recent years, the resolution of lithography has been gradually increased, and light having a shorter wavelength has been increasingly used as a light source to realize the resolution. Specifically, ultraviolet light (g-line (4
36 nm) and I-rays (365 nm)) are now moving to far ultraviolet light (KrF excimer laser (248 nm)). In the near future, vacuum ultraviolet light (ArF excimer laser (193 nm)) will be used. In order to achieve higher resolution, the F ₂ excimer laser (1
58 nm) is likely to be used.

A polymer having a functional group such as a carbonyl group or a conjugated double bond absorbs light of 200 nm or more, and causes photodegradation. Therefore, an amorphous fluoropolymer that does not contain these functional groups and consists only of a saturated bond is used as a film material of a pellicle for far ultraviolet light. Since such amorphous fluoropolymer is having high transmittance to near 180 nm, it showed a large absorption for less wavelength light, not shown only very small transmittance, for example, F ₂
It is difficult to use as a pellicle film material for excimer laser (158 nm).

[0007] Even if the material is transparent in the ultraviolet region of 200 nm or more, as described above, the material often shows light absorption when the wavelength is shortened. In such a case, a high transmittance for vacuum ultraviolet light cannot be obtained, and light absorption of the resin causes light deterioration of the resin.

In the case where a resin thin film is used as the pellicle film, there is a problem that the film thickness decreases and the transmittance decreases as the film deteriorates with light. In addition, radicals in the polymer chain are cut and recombined, and the refractive index of the polymer changes. Such changes in transmittance and refractive index cause uneven illuminance on a wafer to be exposed, and adversely affect lithography.

Further, since the pellicle film is a very thin film, it causes interference with light serving as a light source for lithography. Therefore, at the time of manufacturing the pellicle, the film thickness is controlled so as to maximize the transmittance by calculating light interference. However, when the film thickness changes due to light irradiation, interference deviates, the transmittance decreases, and there is a problem that irradiation unevenness occurs on the wafer.

The present invention has been made in order to solve such problems, and has a long life without light deterioration or decomposition even when irradiated with a short wavelength vacuum ultraviolet light for a long time, and It is a main object to provide a pellicle made of a high-performance pellicle film having a high light transmittance and no change.

[0011]

In order to achieve the above object, a pellicle for lithography according to the present invention is a pellicle used for lithography, wherein a transparent fluoropolymer comprising only carbon atoms and fluorine atoms is used as the film material. It is characterized by being used.

As described above, when a transparent fluoropolymer composed of only carbon atoms and fluorine atoms is used as a pellicle film material, it does not contain oxygen atoms, particularly ether bonds (C—O—C). A pellicle for lithography comprising a high-performance pellicle film having a long life without being degraded or decomposed even when irradiated with light for a long time and having a high light transmittance and no change with time can be provided.

In this case, it is preferable that the transparent fluoropolymer composed of only carbon atoms and fluorine atoms contains a cyclic portion composed of a perfluoroalkyl group represented by the following general formula [1]. Since such a fluoropolymer contains a cyclic portion as a constituent component, it becomes amorphous and has even more excellent transparency, has a high light transmittance of short-wavelength ultraviolet light, and does not change with time. Therefore, a pellicle for lithography comprising a long-lived, high-performance pellicle film that does not deteriorate or decompose even when irradiated with a short-wavelength vacuum ultraviolet light for a long time can be formed.

[0014]

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In this case, it is preferable that the transparent fluoropolymer comprising only carbon atoms and fluorine atoms contains a perfluoroalkyl group in the side chain of the cyclic portion represented by the following general formula [2]. Such fluoropolymers also
Since it contains a cyclic portion consisting only of carbon atoms and fluorine atoms and its side chains as constituents, it is amorphous, has high transparency, and has a higher light transmittance for short-wavelength vacuum ultraviolet light, and does not change with time. Therefore, it is possible to form a pellicle for lithography comprising a long-lived, high-performance pellicle film that does not undergo photodegradation or decomposition even when irradiated with short-wavelength ultraviolet light for a long time.

[0016]

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The pellicle for lithography of the present invention can be used for vacuum ultraviolet light. That is, as the demand for the resolution of lithography has increased, light of a short wavelength has come to be used as a light source in order to realize the resolution, but the pellicle for lithography of the present invention is particularly suitable for vacuum ultraviolet light of a short wavelength. ArF excimer laser (193 nm) and F ₂ excimer laser (158
nm), the pellicle can be a pellicle for lithography comprising a high-performance pellicle film with a long life without causing light degradation or decomposition.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. The present inventors have conducted intensive studies to solve the above problems, and found that a pellicle for vacuum ultraviolet light can be solved by using a transparent fluoropolymer composed of only carbon atoms and fluorine atoms as a film material thereof, The present invention has been completed by ascertaining various conditions.

That is, the present inventors have studied the use of a 180 nm amorphous fluoropolymer used for KrF excimer laser or ArF excimer laser lithography.
As a result of various studies on the following large absorption for vacuum ultraviolet light, it was found that the ether bond (C-O-C) in the above-mentioned amorphous fluoropolymer was a major cause of light absorption of 180 nm or less. .

Thus, a pellicle film material was made of a fluoropolymer consisting of only carbon atoms and fluorine atoms and having no ether bond. In order to obtain a high transmittance, the material must be transparent. For this reason, by forming a cyclic portion in a fluoropolymer consisting of only carbon atoms and fluorine atoms and making it amorphous, transparency is obtained. Was expressed. Further, by introducing a perfluoroalkyl group into the side chain of the cyclic portion, the crystallinity can be further deteriorated. As a result, it has been found that a pellicle having high transmittance even with respect to F ₂ excimer laser light (158 nm) can be obtained.

This will be described in more detail below. The amorphous fluoropolymer used for the KrF excimer laser or the ArF excimer laser lithography is, for example, a wavelength of 180 nm or more in the case of Cytop [trade name of Asahi Glass Co., Ltd.] represented by the general formula [3]. Shows a high transmittance at a wavelength of less than 180 nm,
It has large absorption in the wavelength range of nm to 160 nm.

[0022]

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In order to investigate the cause of the absorption, the absorption spectra of various fluorine monomers and the investigation by computer simulation showed that the ether bond existing in the above-mentioned polymer, that is, the presence of an oxygen atom was 140 to
It turned out to be the cause of the large absorption at 160 nm. In other words, a fluoropolymer having no ether bond has no absorption even at a wavelength of 180 nm or less, and the F ₂ excimer laser light (15
(8 nm), a pellicle made of a high-performance pellicle film having a long life without light deterioration or decomposition and having high light transmittance and no change with time can be provided.

Various polymers can be used as the fluoropolymer consisting only of carbon atoms and fluorine atoms which do not contain oxygen atoms, but polymers having a cyclic portion have poor crystallinity and have higher light transmittance. Therefore, it is convenient to achieve the object of the present invention.

For example, it is preferable that the transparent fluoropolymer composed only of carbon atoms and fluorine atoms contains a cyclic portion composed of a perfluoroalkyl group represented by the following general formula [1]. This transparent fluoropolymer can be obtained by radical polymerization of a linear perfluoroalkyl monomer having two double bonds in its molecular structure. Since such a fluoropolymer contains a cyclic portion as a constituent component, it becomes amorphous, has excellent transparency, has a high light transmittance of short-wavelength vacuum ultraviolet light, and does not change with time. Therefore, a pellicle for lithography comprising a long-lived, high-performance pellicle film that does not deteriorate or decompose even when irradiated with a short-wavelength vacuum ultraviolet light for a long time can be formed.

[0026]

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Further, it is preferable that the transparent fluoropolymer comprising only carbon atoms and fluorine atoms contains a perfluoroalkyl group in a side chain of a cyclic portion represented by the following general formula [2]. A transparent fluoropolymer containing a perfluoroalkyl group in the side chain of the cyclic moiety has two molecules in its molecular structure.
It can be obtained by radical polymerization of a perfluoroalkyl monomer having two double bonds and having a side chain perfluoroalkyl group between the two double bonds.
Such a fluoropolymer also contains a cyclic portion consisting only of carbon atoms and fluorine atoms and its side chains as constituents, so that it is amorphous and has higher transparency, and the light transmittance of short-wavelength vacuum ultraviolet light is higher. High and does not change over time. Therefore, a pellicle for lithography comprising a long-lived, high-performance pellicle film that does not undergo photodegradation or decomposition even when irradiated with vacuum ultraviolet light of a short wavelength for a long time can be formed.

[0028]

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[0029]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and comparative examples, but the present invention is not limited to these examples. (Example 1) A polymer having a cyclic portion represented by the following general formula [4] was used as a fluoropolymer composed of only carbon atoms and fluorine atoms. This polymer was dissolved in a solvent, Fluorinert FC-43 (trade name, manufactured by 3M Company) to obtain a 2% solution. Next, this solution was formed on a silicon substrate whose surface was polished as a transparent film having a thickness of 1 μm using a spin coater. Thereafter, the thin film was peeled off from the silicon substrate and attached to an aluminum pellicle frame to obtain a pellicle.

[0030]

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When the transmittance of the pellicle was measured,
High transmittance was exhibited even at a wavelength of 0 nm or less, and as high as 95% at 158 nm, which is the wavelength of the fluorine excimer laser.

Example 2 As a fluoropolymer consisting of only carbon atoms and fluorine atoms, a polymer containing a cyclic portion represented by the following general formula [5] and having a side chain in the cyclic portion was used. This polymer is dissolved in Fluorinert F
It was dissolved in C-43 [trade name of 3M Company] to make a 2% solution.
Subsequently, a 1 μm-thick transparent film was formed on the silicon substrate whose surface was polished using a spin coater. Thereafter, the thin film was peeled off from the silicon substrate and attached to an aluminum pellicle frame to obtain a pellicle.

[0033]

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When the transmittance of this pellicle was measured,
High transmittance was exhibited even at a wavelength of 0 nm or less, and as high as 97% at 158 nm, which is the wavelength of the fluorine excimer laser.

(Comparative Example 1) Cytop (see the above-mentioned general formula [3]) was used as a film material in the solvent CTsolv. 18
0 (trade name, manufactured by Asahi Glass Co., Ltd.) to give a 5% solution. Next, this solution was formed on a silicon substrate whose surface was polished as a transparent film having a thickness of 1 μm using a spin coater. Thereafter, the thin film was peeled off from the silicon substrate and attached to an aluminum pellicle frame to obtain a pellicle. When the transmittance of this pellicle was measured, it showed a high transmittance at a wavelength of 180 nm or more.
It showed large absorption at wavelengths of 170 nm. Fifteen
The transmittance for 8 nm showed a very low value of 2%.

As described above, the pellicle made of a fluoropolymer having an ether bond is 180
It exhibits large absorption at wavelengths below nm and has only a very low transmittance at 158 nm, which is the wavelength of F ₂ excimer laser, and thus does not have the function of an actual pellicle for vacuum ultraviolet light. However, as shown in Example 1, a pellicle made of a fluoropolymer composed of only carbon atoms and fluorine atoms, which has no oxygen atom and has no ether bond in the fluororesin, has a large absorption even at a wavelength of 180 nm or less. And has a very high transmittance even at 158 nm. Therefore, if a fluoropolymer consisting of only carbon atoms and fluorine atoms is used, it has a long life without light degradation or decomposition even with F ₂ excimer laser lithography, and has a high light transmittance and high aging without change over time. A high-performance pellicle can be provided.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

[0038]

As described in detail above, according to the present invention,
By using a fluoropolymer consisting of only carbon atoms and fluorine atoms, which has no oxygen atoms in the fluororesin and has no polyester bond as the pellicle film, high light can be obtained even with a shorter wavelength F ₂ excimer laser. It is possible to supply a high-performance pellicle having a transmittance and a long life without light degradation or decomposition.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of a pellicle.

[Description of Signs] 1 ... pellicle film, 2 ... pellicle frame, 3 ... adhesive layer,
4 ... release layer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H095 BA07 BC33 4J100 AC26P AR03Q BB07Q BB12Q BB18Q CA04 DA62 JA32 JA43

Claims (4)

[Claims] 1. A pellicle for lithography, wherein a transparent fluoropolymer composed of only carbon atoms and fluorine atoms is used as a film material of the pellicle used for lithography. 2. The transparent fluoropolymer comprising only carbon atoms and fluorine atoms, comprising a cyclic moiety comprising a perfluoroalkyl group represented by the following general formula [1]. Pellicle for lithography. Embedded image 3. The transparent fluoropolymer comprising only carbon atoms and fluorine atoms contains a perfluoroalkyl group on a side chain of a cyclic portion represented by the following general formula [2]. A pellicle for lithography according to claim 2. Embedded image 4. The pellicle for lithography according to claim 1, wherein the pellicle for lithography is for vacuum ultraviolet light.