KR20010088421A - Pellicle for photolithography - Google Patents

Abstract

PURPOSE: To provide a pellicle adhesive which ensures stable adhesive strength, does not cause photodegradation and decomposition, does not damage a pellicle membrane and has a long service life and high performance and a pellicle obtained by bonding a pellicle membrane to pellicle frame with the adhesive. CONSTITUTION: A pressure sensitive adhesive is used as a membrane adhesive for a pellicle which bonds a pellicle membrane comprising a fluororesin to a pellicle frame. The pressure sensitive adhesive is preferably a silicone-base adhesive. The material of the pellicle membrane is preferably a polymer of a fluorine-containing monomer having a cyclic perfluoro-ether group.

Description

Pellicle for photolithography {PELLICLE FOR PHOTOLITHOGRAPHY}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a mold-type pellicle (hereinafter referred to as a pellicle) for photolithography. In particular, when manufacturing a semiconductor device or liquid crystal display panel such as LSI, ultra LSI, etc., light having a wavelength of 500 nm or less is used as a light source. A pellicle for photolithography for dust removal protection of a photomask used for patterning exposure of a photoresist film on a substrate.

The manufacturing process of semiconductor devices, such as LSI and ultra-LSI, or a liquid crystal display panel, includes the process of patterning by irradiating a pattern pattern with the photoresist film formed on the semiconductor web or the original plate for liquid crystal display panels. In this case, if dust particles adhere to an exposure disc (hereinafter referred to as a photomask) used for patterned light irradiation, the dust particles may absorb or scatter light for exposure, so that the pattern is transferred. This deformation may cause the edges to fade, and the quality of dimensions, shapes, and the like of the patterned resist film is impaired, resulting in a decrease in the performance and manufacturing productivity of semiconductor devices, liquid crystal display panels, and the like.

For this reason, these operations are usually performed in a clean room which is damped with indoor air, but even in the cleanest dust damped clean room, it is difficult to keep the photomask completely clean, so that the surface of the photomask is dusted. In order to protect it from the adhesion of particles, a pellicle having a film that transmits light for exposure (hereinafter referred to as a pellicle film) attached to one end surface of a rigid frame (hereinafter referred to as a pellicle frame) on a photomask The method of mounting and exposing through a pellicle film is generally performed.

By placing the pellicle, the dust particles adhere to the pellicle film without directly adhering to the surface of the photomask. Therefore, if the focus is matched on the pattern of the photomask during pattern exposure, the dust particles on the pellicle film will be out of focus. The advantage is that the precision of the patterning is not affected.

Conventionally, this pellicle is coated with a good solvent of a pellicle film on the upper surface of a pellicle mold made of aluminum, stainless steel, or the like, with a transparent pellicle film made of nitrocellulose, cellulose acetate, etc., which transmits light well. (Japanese Patent Application Laid-Open No. 58-219023) Only, it is adhered with a curable adhesive such as an acrylic resin or an epoxy resin (US Patent No. 4486402, Japanese Patent Publication No. 63-27707, Japanese Patent Application Laid-Open No. 7-168345). No.), a pressure-sensitive adhesive (pressure-sensitive adhesive) layer (referred to as a reticle adhesive layer) made of polybutene resin, polyvinyl acetate resin, acrylic resin, silicone resin, etc. is provided on the lower surface of the pellicle mold, and the pressure-sensitive adhesive layer is pellicle The release paper (separator) which protects until it is used is laminated | stacked, and it is set as the finished product.

Among the materials constituting the pellicle, an adhesive (called a membrane adhesive) for adhering the pellicle film to the pellicle mold is particularly important for its performance, particularly durability, in order to be directly irradiated with light for exposure during pattern exposure. Since it is necessary to adhere the pellicle film of the ultra-thin film or less to the pellicle mold, the performance of the adhesive greatly affects the performance of the entire pellicle.

However, conventionally used curable adhesives such as acrylic adhesives and epoxy adhesives have insufficient adhesive strength, lack of reliability due to uneven flattening of the adhesive surface, and the like. In addition, it is very weak to light due to the exposure light, and if used to some extent, the adhesive hardens and decomposes, the adhesive may be a source of dust particles, the tension of the pellicle film changes, and the film may peel off from the pellicle mold. Has the drawback that cracks occur in the pellicle film.

In recent years, fluorine resins excellent in light transmittance and light resistance have been used as materials for pellicle films. However, since fluorine resins have high releasability, practical adhesive strength cannot be obtained with conventional acrylic adhesives and epoxy adhesives.

Therefore, a method of adhering a pellicle film to a pellicle mold by irradiating ultraviolet rays using an adhesive made of a photoreactive resin has been proposed. However, in an adhesive made of a photoreactive resin, a larger adhesive force is obtained than a conventional acrylic adhesive or epoxy adhesive, and it cannot be said to exhibit sufficient adhesive strength yet. Moreover, having photoreactivity means that an adhesive agent hardens with light especially an ultraviolet-ray, and cannot anticipate the light resistance with respect to an ultraviolet-ray at all. Therefore, it is hard to find what is suitable as an adhesive agent for pellicle membranes used under ultraviolet irradiation.

In addition, when the manufacturing process of a pellicle is considered, when photoreactive resin is used for an adhesive agent, such as ultraviolet-ray should be irradiated uniformly over the whole cross section of a pellicle mold | work, operation will become unexpectedly complicated.

Moreover, although it bonds by heating using the adhesive which consists of fluororesins, the method of sticking the pellicle film which consists of a fluorine-type resin by a solvent to a pellicle mold is also proposed. Using this method, a fairly strong adhesive force is obtained. However, in the case of adhesion by heating, there is a problem that the pellicle film in the vicinity of the pellicle mold is elongated and thinned by heat, and the light transmittance of the portion is changed. Moreover, when the manufacturing process is taken into consideration, there are also problems that it is difficult to control the temperature constantly and that the heating and cooling takes time. In addition, in the case of adhesion by a solvent, delicate adjustment of the amount of solvent is necessary, and therefore, skill is required in order to obtain a stable adhesion effect.

The present invention has been made in view of the above problems, and by selecting a suitable membrane adhesive, a pellicle having high light resistance is provided.

In order to solve the said subject, the pellicle of this invention uses an adhesive as an adhesive agent (membrane adhesive agent) which adhere | attaches a pellicle film | membrane to the cross section of a pellicle mold. Such a pressure-sensitive adhesive is also referred to as a pressure-sensitive adhesive, an adhesive that exhibits adhesive force by applying a light pressure at a short time at room temperature, and has the feature that the performance of the adhesive force does not depend on physical and chemical changes.

It is preferable that the pellicle film to which this invention is applied is a film which consists of fluorine-type resin, and it is especially preferable that it is a polymer of the fluorine-containing monomer which has a cyclic perfluoroether group. It is preferable that the adhesive used as a membrane adhesive is a silicone type adhesive.

Embodiment of invention

The present inventors have found that the light resistance of a pellicle can be improved remarkably by using an adhesive as a membrane adhesive. Further, it was found that, by using the pressure-sensitive adhesive, even if the material of the pellicle film is fluorine-based, stable adhesive strength can be obtained, and there is no fear of deterioration or photodegradation of light.

When the pressure-sensitive adhesive is used as the adhesive for the pellicle film made of a fluorine-based resin, the adhesive strength is large, and the pellicle film can adhere to the pellicle mold by adhering the film, thereby significantly increasing the productivity.

As an adhesive, it is very preferable to use a silicone type adhesive.

The present invention first found that a silicone pressure sensitive adhesive could be used as an adhesive of a photomask and a pellicle mold, that is, a reticle adhesive, but the use of the pressure sensitive adhesive for bonding the pellicle film and the pellicle mold was not expected there.

When the silicone pressure sensitive adhesive is used as the membrane adhesive between the pellicle film and the pellicle mold, the adhesive force is exhibited only by adhering the film, which not only increases the productivity dramatically but also is substantially inferior to light, so that a stable adhesive force can be estimated. Long service time and high performance pellicle can be produced.

When the material of the pellicle film is a fluorine resin, when a silicone pressure sensitive adhesive is used as the membrane adhesive, it is possible to add to the above advantages and obtain a high adhesive strength that cannot be obtained with other adhesives.

If the material of the pellicle film is a polymer of a fluorine-containing monomer having a cyclic perfluoroether group, more preferable results can be obtained. When the material of such a pellicle film is selected and the present invention adheres to the pellicle mold using a silicone pressure sensitive adhesive, a pellicle having the maximum adhesive performance of the pressure sensitive adhesive used in the present invention can be produced, and the pellicle film has a fluorine resin. It is possible to provide a high-performance pellicle that fully utilizes such excellent transparency, film strength, and light resistance.

Hereinafter, the present invention will be described in more detail.

As a material of the pellicle film used for the pellicle of this invention, as a specific example of the fluorine-type resin in which the fluorine-type resin which has the characteristic of high light resistance to an ultraviolet-ray is used, PTFE (polytetrafluoroethylene), PFA (perfluoroalkyl vinyl ether, Tetrafluoroethylene copolymer), FEP (fluorinated ethylene propylene) copolymer, etc. are mentioned.

It is more preferable to use the polymer of the fluorine-containing monomer which has a cyclic perfluoroether group as a material of a pellicle film among fluorine-type resin. As a specific example of the polymer of the fluorine-containing monomer containing a cyclic perfluoroether group, the fluororesin "Teflon AF" (brand name) by Du Pont, "Cytoph" (brand name) by Asahi Glass, etc. are mentioned.

When fluorine resin is used for the pellicle film material, it is difficult to obtain a strong adhesive effect as a normal adhesive due to the low surface energy of fluorine resin.

However, if it is an adhesive which has the characteristic that it can adhere | attach even on the surface with low surface energy, it can bond strongly enough. Examples of the pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, butadiene pressure-sensitive adhesives, and the like.

Especially, when a silicone adhesive is used as an adhesive agent for a pellicle film | membrane, very strong adhesive force is obtained. When the fluorine-based resin film is adhered to the pellicle mold with a silicone pressure sensitive adhesive, even if the peeling test of the bonded portion is performed, the film breaks first, and peeling of the bonded portion is often unobservable. In this case, the thickness of the pressure-sensitive adhesive layer is preferably in the range of 5 µm to 100 µm.

A pellicle produced by adhering a pellicle film to a pellicle mold using a silicone-based adhesive as an adhesive, the pellicle film is uniformly adhered to the pellicle mold with high adhesive strength, and there is no occurrence of wrinkles, deformation, looseness, etc., and excellent light resistance. Therefore, it can be a high-performance pellicle that can withstand long time use.

As a specific example of silicone pressure sensitive adhesive, commercial items, such as X-40 type | system | group adhesive from Shin-Etsu Chemical Co., Ltd., KR type | system | group adhesive, are mentioned.

In addition, some adhesives conventionally used need to be subjected to a special post-treatment step to cure to develop an adhesive force, but such adhesives depend on the conditions of the post-treatment step. For example, in the case of an adhesive made of an ultraviolet curable resin, the adhesive force depends on the intensity of the ultraviolet ray and the irradiation time, and when the fluorine resin is heated and cured, the adhesive force depends on the heating temperature and the heating time. However, in the case of a silicone pressure sensitive adhesive, when a pellicle film is adhere | attached, adhesive force expresses immediately, the hardening process which expresses such an adhesive force becomes unnecessary, and a stable adhesive force can be obtained early.

Since the pellicle is used under ultraviolet irradiation, its constituent material requires ultraviolet light resistance. The silicone pressure sensitive adhesive exhibits very high ultraviolet light resistance and has high performance as a membrane adhesive.

EXAMPLE

Hereinafter, the Example of this invention is shown.

Example 1

As the membrane adhesive, a silicone pressure sensitive adhesive [X-40-3068: manufactured by Shin-Etsu Chemical Co., Ltd.] was dissolved in toluene so as to have a concentration of 5% by weight, and a rectangular aluminum product pellicle mold (150 mm X 120 mm) The toluene solution was apply | coated to the upper surface of X6 mm and the mold thickness of 2 mm). Thereafter, the pellicle mold was heated at 150 ° C. for 15 minutes to evaporate toluene, thereby forming an adhesive layer having a thickness of 30 μm. At this point, the silicone pressure-sensitive adhesive layer coated as a membrane adhesive showed adhesiveness on its surface.

The pellicle membrane was produced as follows. That is, the commercially available fluorine-type resin cytotope CTX-S which is a polymer of the fluorine-containing monomer which has a cyclic perfluoroloether group [Asahigarasu Co., Ltd. brand name], and its solvent CTsolv 180 [Asahigarasu Co., Ltd. product name are manufactured. ] To give a solution of 5% by weight concentration. Subsequently, this solution was applied to a silicon substrate having a diameter of 200 mm and a thickness of 1.2 mm by spin coating, and dried by heating at 200 ° C. for 15 minutes to form a transparent thin film having a thickness of 1 μm. This thin film was peeled off from the substrate to obtain a pellicle film.

The obtained pellicle film was first adhered to the pellicle mold in which the layer of the silicone pressure sensitive adhesive was formed in a cross section without looseness, and the unnecessary film portion found from the mold was cut to complete the pellicle.

The adhesive strength between the pellicle film and the pellicle mold was measured, and a value of 1.471 kN / cm (150 gf / cm) was obtained. However, since this is a value when the film is broken, the actual adhesive strength is assumed to be larger than this value.

Comparative Example 1

As the membrane adhesive, a pellicle was completed in the same manner as in Example 1 except that a photoreactive ultraviolet curable acrylic resin was used, and after the pellicle film was adhered, the adhesive layer was irradiated with ultraviolet rays for 5 minutes to cure the adhesive. The development of adhesion required a working time of about 5 minutes.

When the adhesive strength between the pellicle film and the pellicle mold was measured, the pellicle film was not damaged and exhibited a value of 0.343 kN / cm (35 gf / cm).

Comparative Example 2

Cytope CTX-A (trade name, manufactured by Asahigarasu Co., Ltd.) was dissolved as a membrane adhesive in CT solv 180 (elution), a solvent for it, and the solution was added to the cross section of the pellicle mold in a solution having a concentration of 8% by weight. After application | coating, the solvent was evaporated suitably, the pellicle membrane was adhere | attached on the pellicle mold, and the pellicle mold and pellicle membrane were adhere | attached by heating for 5 minutes. The development of adhesion required about 5 minutes of working time. Experimental conditions other than that were completed in the same manner as in Example 1 to complete the pellicle.

Adhesion strength between the pellicle film and the pellicle mold was measured and found to be 1.471 kN (150 gf / cm). However, since this is a value when the film is broken, the actual adhesive strength is estimated to be larger than this value.

As can be seen from the above test results, by using a silicone pressure-sensitive adhesive in the membrane adhesive, a post-treatment step is required to express the adhesive force, and the manufacturing process can be simplified. In addition, the adhesive strength showed a value larger than the breaking strength of the film, and very strong adhesion was possible. On the other hand, when photoreactive resin is used for an adhesive, adhesive force does not reach a silicone adhesive, it requires 5 minutes for expression of adhesive force, and does not reach a silicone adhesive in terms of productivity. In the case where Cytope CTX-A was used as the membrane adhesive, the adhesive strength was obtained with a value equivalent to that of the silicone pressure-sensitive adhesive. However, expression of the adhesive force also required 5 minutes, and the manufacturing process was complicated compared with the silicone pressure-sensitive adhesive.

As described above, according to the present invention, a sufficiently large adhesive strength is obtained by using an adhesive instead of the conventional curable adhesive as a membrane adhesive for bonding the pellicle film and the pellicle mold. In particular, by using a silicone pressure sensitive adhesive, a sufficiently large adhesive strength is obtained by adhering the pellicle film to the pellicle mold. That is, since the process by which adhesive force is expressed is unnecessary, it contributes greatly to the improvement of the productivity of a pellicle. In addition, since the silicone pressure sensitive adhesive has high light resistance to ultraviolet light used as light for pattern exposure in photolithography, it can exhibit a strong adhesive effect over a long period of time even for a fluorine resin-made pellicle film used for pellicle.

Claims (4)

A pellicle for photolithography comprising a pellicle mold made of a rigid material, an adhesive layer formed on one end surface of the pellicle mold, and a pellicle film inserted into the pellicle mold by inserting the pressure-sensitive adhesive layer. The pellicle for photolithography according to claim 1, wherein the pellicle film is a film of a fluorine resin. The pellicle for photolithography according to claim 1 or 2, wherein the pellicle film is a film of a polymer of a fluorine-containing monomer having a cyclic perfluoroether group. The pellicle for photolithography according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive is a silicone pressure-sensitive adhesive.