JPH01191853A - Pellicle film - Google Patents

Abstract

PURPOSE:To prevent generation of interference light, to enhance ray transmittance and to increase the adhesive power between a thin transparent film and antireflection layer by forming the antireflection layer consisting of fluorine- contained poly(meth)acrylate. CONSTITUTION:The antireflection layer consisting of the fluorine-contained poly(meth)acrylate which is a copolymer of one kind of the monomer selected from formula I and at least one kind of the monomer selected from formula II is formed on one face of the thin transparent film. In formulas I and II, R<1> denotes H or methyl group, R<2> denotes a straight chain fluoroalkyl group without contg. ether oxygen; R<3> denotes H or methyl group; R<4> denotes a straight chain fluoroalkyl group contg. ether oxygen or branch fluoroalkyl group which may contain the ether oxygen. The polymer of a desired fluorine content is obtd. by properly changing the kinds of the substituents of R<1>-R<4>, copolymer compsn., etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pellicle film having an antireflection layer used in a pellicle as a dustproof cover for a photomask or reticle.

[Conventional technology]

In the semiconductor exposure process, a method has been proposed for preventing the influence of dust on the exposure process and improving productivity by using a dustproof cover called a pellicle in combination with a photomask or reticle (Japanese Patent Publication No. 54 -28
No. 716). A pellicle has a structure in which a pellicle film is stretched on one side of a pellicle frame, and is used over a photomask or reticle.

Conventionally, a single-layer thin film of nitrocellulose has been mainly used as the pellicle membrane that makes up such a pellicle, but in order to improve throughput in the exposure process, an anti-reflection layer is provided on a transparent thin film of nitrocellulose. A pellicle membrane has been proposed (Japanese Patent Application Laid-Open No. 60-2374
No. 50, JP-A-61-53601 or JP-A-61
-209449).

Among these, JP-A No. 60-237450 describes the use of fluorine-based polymers or silicone-based polymers as antireflection layers, but the fluorine-based polymers shown are tetrafluoroethylene vinylidene fluorocarbons. Ride copolymer or tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene copolymer. JP-A-61-53601 also indicates that fluorine-based polymers and silicone-based polymers can be used as antireflection layers, but the fluorine-based polymers specifically shown are tetrafluoroethylene, vinylidene, etc. It is a fluoride/hexafluoropropylene copolymer. Japanese Patent Publication No. 61-20944
No. 9 states that a fluorine-based polymer containing polyfluoro(meth)acrylate can be used as an antireflection layer, but the specific explanation is similar to the above, such as tetrafluoroethylene vinylidene fluoride.
It is a hexafluoropropylene polymer.

[Problem to be solved by the invention]

However, such a conventional pellicle film having an antireflection layer has problems in that it has low light transmittance and the adhesive strength between the transparent thin film and the antireflection layer is weak. Therefore, when the pellicle film formed on the substrate is peeled off from the substrate, it is necessary to swell and peel it off in water, which may cause wrinkles in the pellicle film when drying, and also has poor productivity.

An object of the present invention is to provide a pellicle film that can prevent the generation of interference light by preventing light reflection, has high light transmittance, has high adhesive strength with a transparent thin film, and has low adhesiveness. The goal is to provide the following.

[Means to solve the problem]

That is, in the present invention, on at least one surface of a transparent thin film,
General formula % Formula % (1) [However, R1 is H or a methyl group, and R2 is a linear fluoroalkyl group containing no ether oxygen. ] and at least one monomer selected from the following.

General formula % Formula % () [However, R3 is H or a methyl group, and R4 is a linear fluoroalkyl group containing ether oxygen or a branched fluoroalkyl group which may contain ether oxygen. ] This is an antireflection type pellicle film characterized in that an antireflection layer is formed of a fluorine-containing poly(meth)acrylate that is a copolymer with at least one type of heptamine selected from the following.

In the present invention, the transparent thin film serving as the main body of the pellicle membrane may be any film having a high average light transmittance at a wavelength of 350 to 450 nm used for exposure, but cellulose such as nitrocellulose, ethylcellulose, cellulose propionate, etc. Derivative thin films are preferred, and among these, nitrocellulose is preferred from the viewpoint of average light transmittance between 350 and 4501 and film strength. Nitrocellulose is 11-12.5%, especially 11.5-12.2
% nitrification degree (N%), and 150,000 to 350,
000, special 4. Those having an average molecular weight (weight average, My) of -170,000 to 320,000 are preferred.

Here, the average light transmittance is a value obtained by taking the same number of peaks and valleys of interference waves of light transmittance occurring between 350 and 450 nm and averaging them.

The thickness of the transparent thin film is selected so that the transmittance for the target wavelength between 350 and 450n is high, but the currently used exposure wavelength of 436nm+405n+
To increase the transmittance for +365 nm, 2.
In order to increase the transmittance to 85 μm and 436 nm, 0.865 μ- is selected.

The antireflection layer formed on such a transparent thin film has the general formula (%) (where R1 is H or a methyl group, and R2 is a linear fluoroalkyl group containing no ether oxygen. ] and at least one monomer selected from the following.

General formula % Formula % () [However, R3 is H or a methyl group, and R4 is a linear fluoroalkyl group containing ether oxygen or a branched fluoroalkyl group which may contain ether oxygen. ] It consists of a fluorine-containing poly(meth)acrylate which is a copolymer with at least one monomer selected from the following, and the types of substituents R1 to R4.

A polymer having a desired fluorine content can be produced by appropriately changing the copolymer composition and the like.

R2 in the general formula (1) has 2 to 1 carbon atoms;
4 is preferably a linear fluoroalkyl group.

Specifically, -CH2CF, -CH,C2F,,
-CH2C, F7゜-co, C4Fs, -C11□C
, F engineeringz--CHFCFzs--CHFCF□7゜-C
I12C,Fl, -CI12C,. F21, -CH,
CH2CF, .

-CH,Cl2C,F,, -C)12CI2C3F,
, -C112C82C4F,.

-CH,C112C,Fyu,, -CI(,CH,C,
F□st -CH, CH2C, F□7゜-CH, CH,
C, Fl, -C112CI12C Eng. F2□, -CH
I(CF2)2u.

-C1l, (CF2), H, -CH, (CF, ), H,
-CH, (CF2), H.

-CHI2(CF,)10)1. -CH, CF, CHF
Examples include CF3°-CH, CF2CHF (CF, )sH, and the like.

In addition, R4 in the general formula (n) has 3 to 1 carbon atoms.
A linear fluoroalkyl group containing an ether oxygen or a branched fluoroalkyl group that may contain an ether oxygen is preferable, and specifically, -CH(CF, )2. −(CIl□)s OCF (
CF, )2.

-(CI, ), , OCF (CF, )! .

-C142CF(CF,)CIIFCF(CF3)2.
-CH2CF(C,F5)CH(CF3)2゜-CF(
CF, )CHFCF(CF3), -CF(C,F,
)CI(CF,),.

-C)l, CF (C,F?)CH(CF3)CF
(CF3)2.

-CH2C(CF3>(C4Fs)CH(CF,
)! .

-CH, CF (C, F engineering 1) CH (CF3) 2.

-C1(2CF(CF,)CI(CF3)C(CF3)
(C,F,),.

-CH2(CF2), 0CF1. -CH2(CF2
), QC, Fs.

-C11□(CF2)20C,F,.

For example, Particularly preferable R4 is R4.

(However, R', R@ are H or methyl groups, and may be the same or different, respectively, R7, R1, C, Hllll
is -F, -CF,, -CF2CF,, -CF(C
F,)2. -CF, CF(CF, )2, or -CF
(CF, )CF (CF3), which may be the same or different, R7 and R1 or 8%, R2
Both O's cannot be -F. Specifically, -CH2-CF (CF, )CHFCF (CF,
), .

-CIl, CF (C2Fs)CH(CF, )z
.

For example, Such R4 is a branched fluoroalkyl group derived from a di- or trimer of hexafluoropropylene.

Alkyl group-containing (meth) of general formula (II) combined with fluorine-containing (meth)acrylate monomer of general formula (1)
The mixing ratio of acrylate monomers is preferably 70 mol% or less, preferably 5 to 40 mol%. In particular, a range in which the fluorine content of the copolymer is 50% by weight or more is preferable; in this range, a layer that is transparent, has a high average light transmittance, and does not cause color unevenness or whitening due to glabellar disorder can be obtained. It will be done.

When the fluorine content in the copolymer is less than 50% by weight,
When a transparent thin film such as a cellulose derivative is formed, it is attacked and color unevenness occurs, and the minimum light transmittance at wavelengths between 350 and 4500 is less than 90%, the average light transmittance decreases, and the transmission by interference light is reduced. The undulation of the rate fluctuation becomes sharper, and the wavelength dependence of the transmittance becomes stronger.

The above-mentioned fluorine-containing poly(meth)acrylate, which becomes the antireflection layer, is formed on one or both sides of a transparent thin film such as a cellulose derivative, and the film thickness is 1/4 nm of the wavelength of the target light. (n is the refractive index) is preferable.

In order to manufacture a pellicle film having an antireflection layer according to the present invention, taking the case of a cellulose derivative transparent thin film as an example, in the case of a single-sided antireflection type pellicle film, the process is performed as follows.

That is, first, a cellulose derivative solution is supplied onto a smooth substrate such as glass, and a transparent thin film of the cellulose derivative is formed by a rotational film forming method. The cellulose derivative is dissolved in a good solvent, and a solution that has been purified by filtration or the like is used. As a solvent, methyl ethyl ketone, methyl isobutyl ketone,
Ketones such as methyl ethyl ketone and acetone, lower fatty acid esters such as butyl acetate and isobutyl acetate, and mixed solvents of the aforementioned ketones or esters with isopropyl alcohol and the like are used. The thickness of the transparent thin film formed can be changed as appropriate by changing the viscosity of the solution and the rotation speed of the substrate.

The cellulose derivative transparent thin film formed on the substrate is dried by means such as hot air or infrared lamp irradiation to remove residual solvent.

Next, supplying the fluorine-containing poly(meth)acrylate copolymer solution onto the dried cellulose derivative thin film,
An antireflection layer made of a fluoropolymer is formed by the rotational film forming method in the same manner as the cellulose derivative thin film. At this time, the solvent for dissolving the fluorine-containing poly(meth)acrylate copolymer is aromatic halogen compounds, fluoroalkylated alcohols, hexafluoropropylene oligomers,
Fluorinated cyclic ether compounds and the like are used.

Specifically, H (CF, ), CH, OH, CF, (CF, ), CH,
Oh.

F(CF2-CF,), CH2CH20H, CF3CF
2CH20H.

Among these, meta-xylene hexafluoride, propatool pentafluoride, pencitrifluoride and the like are particularly preferred.

By using these specific solvents, a fluorine-containing poly(meth)acrylate copolymer solution with good rotary film forming properties can be obtained, and an antireflection solution made of a fluorine-containing poly(meth)acrylate copolymer can be obtained. When forming the layer, it is possible to prevent the adverse effects of dissolving or swelling the cellulose inducer thin film serving as the base layer.

The thickness of the antireflection layer can be controlled by appropriately changing the solution viscosity, the rotation speed of the substrate, etc., similarly to the cellulose derivative thin film.

On the other hand, in the case of a double-sided anti-reflection pellicle film.

A fluorine-containing poly(meth)acrylate copolymer solution is placed on a smooth substrate such as glass (however, the solvent is not particularly limited to the above-mentioned solvents, and any solvent that can dissolve the copolymer may be used)
is supplied, a fluorine-containing poly(meth)acrylate copolymer thin film is formed by a rotary film forming method, and the remaining solvent is removed by drying by means such as hot air or infrared lamp irradiation.

Thereafter, the same operation as above was performed on this thin film to form a 3-layer mixture of fluorine-containing poly(meth)acrylate copolymer/cellulose derivative/fluorine-containing poly(meth)acrylate copolymer.
A double-sided anti-reflection pellicle film with a layered structure can be manufactured.

In this manner, the single-sided or double-sided antireflection pellicle film formed on the substrate is peeled off from the substrate for use as a pellicle. In this case, for example, a frame-shaped jig coated with cellophane tape or adhesive is applied to the outermost layer of a laminated film formed on a substrate, that is, a thin film of fluorine-containing poly(meth)acrylate copolymer that is in contact with the outside air. After adhering, it can be directly peeled off from the substrate by lifting cellophane tape or a frame-shaped jig from one end by hand or mechanical means. At this time, since the interlayer adhesive force between the cellulose derivative layer and the fluorine-containing poly(meth)acrylate copolymer layer is strong, the film is peeled off without separation, and a pellicle film having an antireflection layer is obtained. The pellicle membrane thus manufactured is attached to a frame to form a pellicle.

〔Effect of the invention〕

The pellicle film having the antireflection layer of the present invention has an antireflection layer of 350 to 4
The minimum light transmittance between wavelengths of 50 nm is improved, and fluctuations in light transmittance due to interference of reflected light are also reduced.
The average light transmittance is also improved, and the throughput in the exposure process is improved. In addition, since the adhesive force between the transparent thin film and the antireflection layer is strong, even if it is directly peeled off from the film-forming substrate, it can be peeled off in a laminated state. Furthermore, a fluorine-containing (meth)acrylate monomer containing a linear fluoroalkyl group and a fluorine-containing (meth)acrylate monomer containing a branched fluoroalkyl group
Since a copolymer with an acrylate monomer is used, the light transmittance is improved compared to the case of a polymer of a fluorine-containing (meth)acrylate monomer containing only a linear or branched fluoroalkyl group, and it has a low tackiness. An anti-reflective film is formed and dust is removed.

Foreign matter such as dust is difficult to adhere to.

〔Example〕

An embodiment of the present invention will be described below.

Example 1, Comparative Example 1 Nitrocellulose was dissolved in methyl isobutyl ketone to form a 6% by weight solution. On the other hand, C) 1. has a branched fluoroalkyl group synthesized from a dimer of 80 mol% perfluorooctylethyl acrylate and hesafluoropropylene. =CHC00C)l, CF(CF,)C)IF
A copolymer with 20 mol% of cF(CF,)2(l(FP-DA) [fluorine content: 61.8% by weight]) was dissolved in meta-xylene hexafluoride to make a 1.0% by weight solution.

By a spin coating method, the above nitrocellulose solution is dropped onto a quartz substrate to form a nitrocellulose thin film, and dried.
The above fluorine-containing polymer solution was dropped onto this, and
Dry by spinning for 60 seconds at pm. The pellicle film thus obtained was peeled off from the substrate and framed in a predetermined frame to obtain a pellicle having an antireflection layer on one side.

The light transmittance of the above pellicle was measured using a spectrophotometer (Shimadzu 11UV-240) for the anti-reflection coating, and the light transmittance is shown in Figure 1, and the minimum light transmittance and average transmittance at 350 to 450 nm are measured. are shown in Table 1.

In addition, the above pellicle membrane was attached to the fixing plate with the nitrocellulose membrane surface facing the fixing plate and the antireflection layer side facing the atmosphere, and a 7'/14 steel ball was attached to the antireflection layer surface at 31°C.
．． It was pressed for 50 seconds with a pressing force of 6 g.

Thereafter, the steel ball was pulled apart, and the force required to pull it apart was measured with a sensor (Sansui-type push-type tack measuring device) and determined as the adhesive force. Table 1 shows the average values measured 10 times using this method.

On the other hand, FIG. 2 shows the light transmittance obtained by measuring the spectral characteristics of a pellicle made solely of nitrocellulose (Comparative Example 1). The minimum light transmittance was 84% and the average transmittance was 92%.

Comparative Example 2 The same procedure was carried out except that trifluoroethyl acrylate (67 mol%) and perfluorooctylethyl acrylate (33 mol%) [fluorine content 52.8% by weight] were used in the fluorine-containing copolymer of Example 1. In the same manner as in Example 1, a pellicle was obtained in which a single-layer antireflection layer was formed on one side of a nitrocellulose membrane. The spectral characteristic measurement results and Example 1
Table 1 shows the results of adhesive strength measured in the same manner as above.

Table 1 Example 2 In Example 1, 90 mol% of perfluorooctylethyl acrylate and IIFP-DA were added to the fluorine-containing copolymer.
The same procedure as in Example 1 was carried out except that 10 mol% [fluorine content: 62.1% by weight] was used. Its minimum light transmittance is 91.5%, average transmittance is 96%, and adhesive strength is 4.5
It was g.

Example 3 In Example 1, CH2=C(CH,
)C00C)12CF(CF,)CH(CF,)C(C
2Fs) The same procedure as in Example 1 was carried out except that 10 mol% of 2CF3 (fluorine content: 62.5% by weight) was used. Its minimum light transmittance is 92%, average transmittance is 96-97%
The adhesive force was 5.2 g.

Example 4 Purful weight% in the fluorine-containing copolymer in Example 1]
(b) The same procedure as in Example 1 was carried out except that m was used.

Its minimum light transmittance is 90.5% and average transmittance is 94.
5%, and the adhesive strength was 3.1 g.

Example 5 Nitrocellulose was dissolved in methyl isobutyl ketone to make a 6% by weight solution. Further, a copolymer of 80 mol% perfluorooctylethyl acrylate and 20 mol% IIFP-DA [fluorine content 61.8% by weight] was dissolved in meta-xylene hexafluoride to form a 1.0% by weight solution.

Using a spin coating method using a quartz substrate, the fluorine-containing polymer solution was first dropped onto the substrate, rotated at 500 rpm for 60 seconds, and then dried. A nitrocellulose solution was dropped onto this to form a thin film, which was then dried, and a fluorine-containing polymer solution was further dropped onto this to form a thin film at 500 rpm.
Rotate for a second and then dry. This pellicle having single-layer antireflection layers on both sides could be peeled off smoothly from the substrate. The spectral characteristics measurement results of this pellicle are 350~450r+
The minimum light transmittance at m is 95%, and the average transmittance is 9
It was 7-98%.

Moreover, the adhesive strength was 4.7 g.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing light transmittance. Agent: Patent attorney Sei Yanagi Hara

Claims (4)

[Claims] (1) On at least one side of the transparent thin film, there is a general formula▲mathematical formula, chemical formula, table, etc.▼...(I) [However, R^1 is H or a methyl group, and R^2 contains ether oxygen. It is a straight-chain fluoroalkyl group. ]
At least one monomer selected from general formula ▲ mathematical formula, chemical formula, table, etc. ▼ (II) [However, R^3 is H or a methyl group, and R^4 is a linear fluorocarbon containing ether oxygen. It is a branched fluoroalkyl group which may contain an alkyl group or an ether oxygen. ] An antireflection type pellicle film comprising an antireflection layer made of fluorine-containing poly(meth)acrylate which is a copolymer with at least one monomer selected from the following. (2) The pellicle membrane according to claim 1, wherein the transparent thin film is a cellulose derivative thin film. (3) The pellicle membrane according to claim 2, wherein the cellulose derivative is nitrocellulose, ethylcellulose, or cellulose propionate. (4) In the general formula [II], R^4 is a ▲ mathematical formula, chemical formula, table, etc. [However, R^5 and R^6 are H or a methyl group, and may be the same or different, R^7, R^8, R^
9, R^1^0 is -F, -CF_3, -CF_2CF_
3, -CF(CF_3)_2-CF_2CF(CF_3
)_2, or -CF(CF_3)CF(CF_3)_
2, each may be the same or different, but R^7
and R^8, R^9, and R^1^0 cannot both be -F. ] The pellicle membrane according to any one of claims 1 to 3, which is represented by: