JPH02285348A - Pellicle - Google Patents

Abstract

PURPOSE:To obtain the pellicle which has an excellent ray transmittance and is prevented of electrostatic charge by using a specific fluorine polymer having an electrical conductivity for an antireflection layer. CONSTITUTION:The pellicle has an optical thin-film body 1 and a base 2 which has this film body on one side via an adhesive layer 3 and has a tacky adhesive agent layer 4 on the end face on the side opposite thereto. The optical thin-film body 1 has the perfluoroinated polymer contg. the ionic functional group expressed by formula -SO3M (M is H, Na, K or NR4 and further R is H, lower alkyl group) in the molecule on at least one surface as the antireflection layer. The pellicle which has the high ray transmittance, is lowered in the electric resistance on the surface of the thin film and is prevented of electrostatic charge is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The purpose of this invention is to prevent foreign matter from adhering to transparent substrates (hereinafter referred to as masks) such as photomasks and reticles used in the lithography process of LSI manufacturing. Concerning the pellicle used. More specifically, the present invention relates to a pellicle that has excellent light transmittance and is antistatic.

[Prior Art] When forming fine circuit patterns on a wafer in semiconductor manufacturing, semiconductor manufacturing equipment such as a stepper is used. What is important here is the quality of the mask for forming the circuit pattern incorporated into the semiconductor manufacturing equipment. In recent years, with the development of large-scale integrated circuits, the line width has become extremely fine, and this trend is expected to continue in the future. Therefore, the quality of masks has a large impact on the operating rate and manufacturing costs of semiconductor manufacturing equipment. It's becoming a thing. In particular, it is a serious problem that foreign matter adhering to the mask reduces the yield. One way to solve this problem is to protect the mask from foreign substances by attaching a so-called pellicle (see, for example, Japanese Patent Publication No. 54-28716). On the other hand, large-scale integrated circuits are becoming more customizable, and there is a growing trend toward high-volume, low-volume production. This means that a large number of masks are used, and the need for mask storage management has increased. In this case, it is becoming recognized that storage with a pellicle attached is convenient for management.

FIG. 1 is an explanatory diagram of a pellicle used in such a place. Here, the optical thin film 1 is firmly fixed to the support frame 2 by the adhesive layer 3 without wrinkles or cracks. The supporting frame 2 has an adhesive layer 4 on the other end surface, and a protective film 5 is optionally placed thereon. Such a pellicle is used by peeling off the protective film 5 and attaching it to a mask via the adhesive layer.

By the way, thin films made of polymers and having a thickness of about 0.5 to 10 μm are generally used as optical thin film bodies, but these have extremely high electrical resistance and are therefore easily charged. When foreign matter gets stuck due to static electricity, it is extremely difficult to remove it with air blowing or the like. Alternatively, when the mask is attached, there is a risk that such foreign matter may somehow fall onto the mask surface and cause a defect in the exposure pattern.

For the purpose of preventing such static electricity, Japanese Patent Application Laid-Open No. 80-1342
No. 39 proposes a pellicle in which the optical thin film body is electrically conductive. As a method of imparting electrical conductivity to an optical thin film body, the use of a light-transmitting plastic film to which a conductive polymer is added or whose surface resistivity is lowered is described. Furthermore, 5nOz or 1nz0 is applied to the optical thin film body.
A method of attaching a transparent conductive film such as No. 3 by vapor deposition or the like is also described. However, these methods have the disadvantage that the light transmittance, which is an important specification of a pellicle, decreases.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the above-mentioned problems of conventional pellicles, and to provide a pellicle that has excellent light transmittance and is antistatic. It is said that

[Means for Solving the Problems] The present inventors have conducted various studies in order to solve the above-mentioned problems. The present invention has been completed based on the discovery that the problem can be solved by the following.

An antireflection pellicle using a polymer with a refractive index of 1.42 or less as the outermost layer as an optical thin film body was published in Japanese Patent Publication No. 1983-
It was proposed in Publication No. 22570, and further published by Tokko Sho (13-25
(Publication No. 158 proposes a pellicle in which the polymer is a fluorine-based polymer.The film thickness of these pellicles is set so that interference waves with light rays cancel each other out by meeting optical anti-reflection conditions. It is a pellicle with extremely high light transmittance.Based on these excellent light transmittances, we searched for fluorine-based polymers and as a result, we came up with the present invention.That is, the present invention It has a thin film body on one side with an adhesive attached to it,
and a support frame having an adhesive layer on the opposite end surface, the optical thin film body having a maximum of -503M (herein, M is H, Na, K or NR4).
and further R is a lower alkyl group H1), which has a perfluorinated polymer containing an ionic functional group in its molecule as an antireflection layer on at least one side. It is a pellicle that is prevented.

The precursors of such polymers used as antireflection layers of the present invention are prepared from at least two monomers, at least one of which is selected from each of the following two groups: .

The first group is vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl ether) and mixtures thereof.

The second group is monomers having a sulfonyl fluoride group, which is a precursor of an ionic functional group.

More specifically, CF2-CF-0-T-CF 2-50
It is a monomer represented by the general formula 2F.

The T group in the formula is a difunctional fluorinated group consisting of 1 to 8 carbon atoms, and may be branched or unbranched.
It can have one or more ether linkages. Such monomers are described in U.S. Pat. No. 8,282,875, 304.
No. 1317, No. 8718827, and No. 85005 (disclosed in the 18th edition), examples of which include:

CF2- CFOCF2CF2 SO2FeF2- C
POCP20F (CF3)OCP20P2802 F
eF2-CP[0CF2CF (CF3)]2 0CF
2 Cr21802F CF2- CFOCF2 CF (CF20CF3)
OCP2 CF2502F CF2-CPOCP2 C1' (CF3)OCP2
CF2 CF2 S02 FeF2- Cr'OCr
By copolymerizing monomers such as '2CF20F2802F and above, a precursor of the copolymer used in the present invention can be formed. - A conventional polymerization method, such as the method used to produce tetrafluoroethylene, can be applied. However, it is desirable to have as few impurities as possible, so
For example, it is preferable to manufacture by a non-aqueous polymerization method disclosed in US Pat. No. 8,041,317. That is, it can be produced using an inert liquid such as perfluorocarbon or chlorofluorocarbon as a solvent in the presence of a free radical initiator such as perfluorocarbon peroxide or an azo compound at a temperature of 0 to 200°C and a pressure of 1 to 200 atm. .

Preferred precursors are polymers having repeat units as follows.

-(-CX2 CX2- ) , -(-CF-Cr2
-)11 =\ where m is 3 to 15, n is 1 to 1O, p is 0, ■ or 2, and X together is 4 fluorine or 3 fluorine and 1 is chlorine, Y is F, Cr
or -CF2.0CF3, q is 2 or 3.

Such perfluoropolymers include, for example, C
FZ-CF2 and Cr2- CFOCF2 CP-(
CF3) OCP20P2802 P% CF2
- CFOCP2 -CF2 802 P,
CF2 ■ CPOCP2 CF2 Cr2 8
02 P, CI'2 - CPOCP2 CF
Copolymers with (CF3)OCP2 Cr2 Cr2 SO2F, etc. can be mentioned. Among them, the most preferred are tetrafluoroethylene and perfluoro(3,6-thioxer 4-methyl-7-octensulfonyl fluoride).

These precursor fluorinated polymers with sulfonyl fluoride groups are contacted with an aqueous solution of a metal alkyl or tetraalkylammonium hydroxide or an aqueous solution to which a water-miscible organic compound, such as dimethyl sulfoxide, is added. By converting the sulfonyl fluoride groups, a fluorinated polymer having a sulfonic acid type or sulfonate ionic functional group can be obtained.

The fluorinated ionic functional group-containing polymer used as the antireflective layer of the present invention has a refractive index of about 1534 to 1.38. Among these polymers, the low refractive index satisfies the optical conditions for antireflection (Japanese Patent Publication No. 3-258
(See Publication No. 58). When an antireflection layer is formed on at least one side by coating such a polymer, an antistatic effect can be obtained. However, anti-reflection on both sides is a more preferable embodiment because the light transmittance can be further improved than when only the half side is used. Furthermore, by having an ionic functional group, the film becomes a thin film with low electrical resistance suitable for preventing static electricity, and can prevent foreign matter from attaching to the layer due to static electricity. That is, when these polymers are used in the outermost layer of an optical thin film, it is possible to provide a pellicle that has extremely good light transmittance and is antistatic.

As the material constituting the center layer of the optical thin film body 1, an inorganic substance such as quartz or a polymer can be used.

Examples of the polymer include polyethylene terephthalate, cellulose esters, polycarbonate, polymethyl methacrylate, polyvinyl butyral, and the like. Particularly commonly preferred materials include nitrocellulose,
Cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate are used.

As the support frame 2, aluminum alloy, plastic, ceramics, etc. can be used. Its size is about 1 to 8 inches in diameter or 1 to 8 inches square, depending on the size of the mask, and its height is about 2 to 1O2.

Many adhesive layers can be used as the adhesive layer 3. For example, natural products such as dextrin and starch, thermoplastic adhesives such as vinyl acetate and acrylic resins, thermosetting adhesives such as amino resins, phenolic resins, and epoxy resins, and rubber adhesives such as polychloroprene and nitrile rubber are used. be. Furthermore, there are various types of adhesives such as ultraviolet curing type, heat curing type, and instant curing type. Of course, it is desirable to have a material that generates less dust.

As the material for the adhesive layer 4, so-called double-sided calculus tape, which is a foamed or non-foamed tape provided with a sticky agent on both sides, is used. Furthermore, polymers that are calculable and elastic are also suitably used. For ease of attachment to the mask, it is preferable that the elastic body forms part of the layer.

The pellicle is stored in a clean case until it is ready for use, to prevent dust from adhering to it. When used in a stepper, the influence of foreign objects is extremely sensitive, so a pellicle must be attached not only to the image side of the mask but also to other surfaces.
There are many.

The present invention will be explained in more detail with reference to Examples below.

[Example] Example 1 N-proper tool 45 in a 1-liter autoclave with a stirrer
hl, 300ml of water and 8g of a powdered copolymer of tetrafluoroethylene and perfluoro(3,6-thioxer-4-methyl-7-octensulfonyl fluoride) whose functional group has been hydrolyzed into the 15O3Na type. The mixture was heated to 240° C. for 18 hours with stirring, and then cooled to room temperature to obtain a clear solution.

The above fluorinated ion exchange polymer solution was applied using a spin coater to both sides of a separately prepared 2.6 μm nitrocellulose thin film.

An optical thin film body having antireflection layers of about 800 on both sides was obtained.

A urethane acrylate adhesive (manufactured by Three Bond ■, 3052C) was applied to a support frame made of an aluminum alloy, and the adhesive was applied to the optical thin film, and was cured and fixed by ultraviolet curing. Double-sided adhesive tape (manufactured by 3M Oki, 42B2) was attached to the opposite end of the support frame to form a pellicle.

This pellicle exhibited a light transmittance of 99.5% for g-line and i-line. In addition, it was possible to remove the foreign matter very easily by air blowing after diluting it.

Example 2 A pellicle was made in a manner similar to Example 1, except that another fluorinated ion exchange polymer solution was made as described below.

n-Propa Tool 20 in a 1-alternate autoclave with a stirrer
0m1. 160ml of methanol, 400ml of water, and 8g of a powdered copolymer of tetrafluoroethylene and perfluoro(3,6-thioxer-4-methyl-7-octensulfonyl fluoride) whose functional group has been hydrolyzed into the 1503H type. After heating at 220°C for 3 hours while stirring, the mixture was cooled to room temperature and left to stand. The liquid layer was separated into two layers, and the lower density upper layer was removed, and 80 gr of trimethyl phosphate was added to the lower transparent solution and stirred to obtain a homogeneous solution.

This pellicle also had a light transmittance comparable to that of Example 1, and also had an excellent antistatic effect.

[Effects of the Invention] As explained above, the pellicle of the present invention has high light transmittance, and the electrical resistance of the thin film surface is reduced, so that charging can be prevented, so even if foreign matter adheres to the thin film surface, It can be removed into the container by air blowing or the like.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a general pellicle. In the figure, 1 is an optical thin film body, 2 is a support frame, 3 is an adhesive layer, 4 is a double-sided adhesive tape, and 5 is a protective film.

Claims (1)

[Claims] In a pellicle comprising an optical thin film body and a support frame having the optical thin film body on one side via an adhesive and having an adhesive layer on the opposite end surface, the optical thin film body is generally Formula - SO_3M (where M is H, Na, K or NR_4
and R is H, a lower alkyl group), and further comprises a perfluorinated polymer containing an ionic functional group in the molecule, as an antireflection layer on at least one side. anti-static pellicle.