JPH04237056A - Pellicle - Google Patents

Abstract

PURPOSE:To provide the pellicle superior in light resistance and free from occurrences of dust and uneven adhesion. CONSTITUTION:The pellicle comprises a pellucle frame and a pellicle film set up on one side with the frame and coated on the other side with a hot melt adhesive comprising a block copolymer consisting of both side blocks of styrene polymers and a middle block of an ethylene-butylene copolymer or ethylene-propylene copolymer, an aliphatic petroleum resin, and a liquid paraffin and having a melt viscosity of <=10000psc.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention prevents foreign matter such as dust from adhering to photomasks, reticles, etc. (hereinafter simply referred to as masks) used in the photolithography process in the manufacturing process of semiconductor devices such as ICs and LSIs. Regarding pellicles used for the purpose of

0002

[Prior Art and Problems to be Solved by the Invention] In the photolithography process, a mask is used in which a circuit pattern is formed on the surface of a glass plate using a vapor-deposited film of chromium, etc., and the circuit pattern is placed on a silicon wafer coated with a resist. The work of transcribing is performed. In this step, if exposure is performed with foreign matter such as dust attached to the circuit pattern on the mask, the foreign matter will also be transferred onto the wafer, resulting in a defective product. In particular, when the exposure is performed using a stepper, there is a high possibility that all the chips formed on the wafer will be defective, and adhesion of foreign matter to circuit patterns such as masks is a big problem. In order to solve this problem, pellicles have been developed and started to be used in recent years.

[0003] A pellicle is generally made of an aluminum pellicle frame with a transparent film made of nitrocellulose or the like stretched on one side, and can be attached onto a mask by pasting double-sided adhesive tape on the other side. ing. According to this,
This prevents foreign matter from entering from the outside, and even if foreign matter were to adhere to the film, it would not cause any problems as it would be transferred out of focus during exposure, but the pellicle would be pressed during attachment. As a result, foreign matter may be generated from the foam in the intermediate layer of the double-sided adhesive tape, which is a problem.

[0004]Also, it is also possible to use a double-sided adhesive tape whose intermediate layer is a hard film such as PET, or to directly apply an adhesive instead of the double-sided adhesive tape.
In this case, the generation of dust and the like due to the pressure applied during adhesion is improved, but uneven adhesion occurs during adhesion, creating an air path, which is undesirable as a cause of dust generation.

Since pellicles are often used in a state where they are irradiated with ultraviolet rays, the adhesive is also exposed to a large amount of ultraviolet rays, so conventional products with improved stability against direct sunlight may suffer from decreased adhesive strength, discoloration, etc. Furthermore, due to deterioration of the adhesive, the adhesive itself becomes a dust generator and contaminates the closed space inside the pellicle.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have completed the present invention as a result of intensive research. That is, the present invention is characterized in that, in a pellicle consisting of a pellicle frame and a pellicle membrane stretched on one side of the frame, the following adhesive (a) is applied to the adhesive surface of the other side of the pellicle frame. The present invention provides a pellicle that allows for

(a) A block copolymer (A) in which both end block portions are made of a styrene polymer and a central block portion is made of an ethylene-butylene copolymer or an ethylene-propylene copolymer, an aliphatic petroleum resin ( A hot melt adhesive comprising B) and liquid paraffin (C) and having a melt viscosity of 10,000 cps or less at a temperature of 160°C.

The block copolymer (A) as the base resin constituting the hot-melt adhesive used in the present invention has block parts at both ends made of styrene polymer and block part in the center made of ethylene-butylene polymer. This is a block copolymer made of a polymer, or a block copolymer in which the block portions at both ends are made of a styrene polymer and the block portion in the center is made of an ethylene-propylene copolymer. The block copolymer is obtained by hydrogenating a block copolymer in which the block portions at both ends are made of styrene polymer and the block portion in the center is made of butadiene and/or isoprene to reduce diene bonds.

When the central block portion is butadiene, a block copolymer in which the central block portion is an ethylene-butylene copolymer can be obtained by hydrogenation. When the central block part is isoprene, a block copolymer in which the central block part is an ethylene-propylene copolymer can be obtained by hydrogenation.

[0010] In each of the block copolymers, the ratio of the styrene blocks at both ends to the central ethylene-butylene copolymer block or ethylene-propylene copolymer block is 15 to 1.
It is desirable that the polymerization ratio is 30/85 to 70.

[0011] The molecular weight of the block copolymer is 10,000 to 5
00,000, preferably 20,000 to 350,000, more preferably 50,000 to 80,000. When the molecular weight is less than 10,000, the strength of the adhesive is low and creep is likely to occur. On the other hand, when the molecular weight exceeds 500,000, the melt viscosity becomes high, which is not preferable.

The above block copolymers may be used alone or in combination of two or more. A particularly desirable block copolymer for use in the present invention is a block copolymer in which the block portions at both ends are made of a styrene polymer and the block portion in the center is made of an ethylene-butylene copolymer.

In order to reduce the melt viscosity of this block copolymer, a liquid rubber may be added. As the liquid rubber, liquid polyisobutylene or liquid butyl rubber having few unsaturated bonds is preferable in consideration of ultraviolet resistance. Furthermore, those obtained by hydrogenating these liquid rubbers to eliminate unsaturated bonds can also be preferably used.

Aliphatic petroleum resin (B) used in the present invention
Examples include n-pentene, iso-pentene, isoprene, pentadiene, methylbutene, 2-methylbutene-
1 and 2, polymers and copolymers such as cyclopentadiene, softening point 20-100°C, molecular weight 400-100
0. Further, these polymers in which unsaturated bonds are hydrogenated can also be used satisfactorily.

[0015] The liquid paraffin (C) used in the present invention is a mixture of liquid saturated hydrocarbons with high purity, and is compliant with JIS
Any material specified in K2231-83 can be used.

The hot melt adhesive used in the present invention can be produced by melt-mixing the above materials. The mixing ratio is 100 parts by weight of the block copolymer (A), 50 to 400 parts by weight of the aliphatic petroleum resin (B), and 50 to 200 parts by weight of the liquid paraffin (C). Up to 50% by weight of liquid rubber can be mixed in.

[0017] If the amount of the aliphatic petroleum resin (B) added is less than 50 parts by weight, the tackiness will be insufficiently improved. Moreover, if it exceeds 400 parts by weight, rubber elasticity is lost, which is not preferable. Liquid paraffin (C) reduces the melt viscosity of the final adhesive,
Since it is added for the purpose of improving processability and initial adhesiveness, if it is less than 50 parts by weight, processability such as adhesive coating properties will be poor and initial adhesiveness will not be improved. 20 again
If it exceeds 0 parts by weight, liquid paraffin will seep out from the adhesive and cause contamination of the mask, which is not preferable. Addition of up to 50% of the block copolymer (A) is sufficient for improving the fluidity of the block copolymer (A) using liquid rubber, and addition of more than 50% is not preferable because the holding power decreases.

[0018] The method for producing a hot melt adhesive is to roll,
A hot melt adhesive can be made by melting and mixing using a known mixer such as a kneader. The mixing temperature is 1
50°C to 200°C is preferred.

[0019] The hot melt adhesive of the present invention has a temperature of 160°C.
The melt viscosity at °C must be 10,000 cps or less; if it exceeds 10,000 cps, the viscosity will be high and processability will be poor when applied to the pellicle frame, and the hardness of the applied adhesive will increase, making it difficult to air pass when pasting. This is not desirable.

It is preferable to further add an ultraviolet absorber, an ultraviolet stabilizer, an antioxidant, etc. to the hot melt adhesive of the present invention in order to improve the ultraviolet resistance. Preferred ultraviolet absorbers include benzotriazole and benzophenone, preferred UV stabilizers include hindered amines, and preferred antioxidants include hindered phenols. The larger the amount added, the better the effect, but if it is too large, the additive will precipitate on the surface of the adhesive and cause dust generation, so it is desirable that the total amount of additives be 3% or less.

The method for manufacturing the pellicle of the present invention is to stretch a pellicle membrane made of nitrocellulose or the like on one side of a pellicle frame made of an aluminum alloy or the like, and to apply the hot melt adhesive in a molten state to the other side. It can be manufactured by applying the adhesive using a syringe or the like, and then performing secondary processing using a hot plate or the like to make the adhesive surface flat.

[0022]

Effects of the Invention The pellicle according to the present invention is stable against ultraviolet rays, can be used for long periods of time under ultraviolet irradiation, does not reduce adhesive strength due to deterioration of the adhesive, does not generate dust from the adhesive, and can be used as a mask. It is possible to obtain a pellicle that completely adheres to the surface of the pellicle, has no air path, and completely prevents dust from entering from outside the pellicle.

[0023]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

Example 1 A block copolymer in which the block portions at both ends are made of a styrene polymer and the block portion in the center is made of an ethylene-butylene copolymer (composition ratio of ethylene-butylene copolymer and styrene polymer: Ethylene-butylene/styrene = 7
5/25, molecular weight 70,000) 100 parts by weight of liquid rubber, 25 parts by weight of polyisobutylene (Tetrax 5T manufactured by Nippon Petrochemical Co., Ltd.), and 225 parts by weight of cyclopentadiene petroleum resin Escorez E5300 (manufactured by Tonex Corporation) as aliphatic petroleum resin. A hot melt adhesive was obtained by melting and mixing 150 parts by weight of liquid paraffin in a kneader at 180°C. This adhesive had a viscosity of 6300 cp at 160°C.
It was s. This hot melt adhesive is applied to the pellicle frame with a syringe kept at a temperature of 160°C to a thickness of 0.
After coating to a thickness of 5 mm, the coated surface was flattened to obtain a pellicle. Evaluation of Ultraviolet Resistance A pellicle obtained by applying an adhesive was attached to a quartz glass plate for a mask at a weight of 1 kg/cm 2 for evaluation.

Light source: Ushio Inc. ultra-high pressure mercury lamp (500W) Filter: Corning CSO-52 Irradiation amount: 4300
J/cm2/day Irradiated surface temperature: approximately 50°C The pellicle was irradiated with ultraviolet rays under the above conditions, and the adhesive strength and appearance of the adhesive were evaluated. The results are shown in Table 1.

Example 2 The ultraviolet absorber Tinuvin 326 (manufactured by Ciba Geigy) was added to the hot melt adhesive of Example 1.1.
5wt% Ultraviolet stabilizer Tinuvin 144 (manufactured by Ciba Geigy) 0.
The same procedure as in Example 1 was carried out except that 5 wt % of the antioxidant Irganox 1010 (manufactured by Ciba Geigy) and 1.0 wt % of the antioxidant were added. Table 1 shows the evaluation of ultraviolet resistance.

Comparative Example 1 A block copolymer in which both end block portions are made of styrene polymer and the central block portion is made of butadiene polymer (composition ratio of butadiene polymer and styrene polymer: butadiene/styrene = 75/25, Molecular weight 70000) 100
Parts by weight include 25 parts by weight of polyisobutylene (Tetrax 5T, manufactured by Tonex Corporation) as liquid rubber, and 225 parts by weight of aliphatic petroleum resin Clearon P-105 (manufactured by Yasushi Kogyo Co., Ltd.).
A hot melt adhesive was obtained by melt-mixing 150 parts by weight of liquid paraffin. This hot melt adhesive was applied to a pellicle frame in the same manner as in Example 1 to obtain an adhesive-attached pellicle. The ultraviolet test was conducted in the same manner as in Example 1 and the results are shown in Table 1.
Shown below.

[0028]

[Table 1]

Claims (1)

[Claims] 1. A pellicle consisting of a pellicle frame and a pellicle membrane stretched on one side of the frame, characterized in that the adhesive surface of the other side of the pellicle frame is coated with the following adhesive (a). pellicle. (a) A block copolymer (A) in which both end block parts are made of a styrene polymer and a central block part is made of an ethylene-butylene copolymer or an ethylene-propylene copolymer, an aliphatic petroleum resin (B), Liquid paraffin (C
) with a melt viscosity of 10,000c at a temperature of 160°C.
A hot melt adhesive having a ps or less.