JPH02272550A - Pellicle and production thereof - Google Patents

Abstract

PURPOSE:To obtain the high-quality pellicle which is entirely free from defects, such as stains, and >=1mum particles even when visually inspected under a powerful strong light by completely separating an optical thin film body and a substrate by a dry process. CONSTITUTION:The pellicle constituted by extending the optical thin film having the thickness within an about 0.5 to 10mum range on a supporting frame is so formed that the stains do not exist visually sensibly on this thin film body when at least the part of the thin film body thereof to be exposed to exposing rays is irradiated with condensed light of 100W over 0 to 90 deg. angle with the film plane. For example, the pellicle which is subjected to antireflection on both surfaces and has an excellent ray transmittance is produced by applying antireflection layers on both the front and rear surfaces of the optical thin film body. Liquids, such as water, are not used at all in this production process and further, such an excess stage as to provide the source for dust generation as to application of a release agent on a substrate is not adopted. The pellicle which is absent of the sensible stain 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. This article relates to the pellicle used and its manufacturing method. More specifically, the present invention relates to a pellicle without stain defects and a method for manufacturing the same.

[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 is becoming a thing. It is particularly important 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 the trend toward high-mix, low-volume production is becoming stronger. 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 body 1 is fixed to the support frame 2 by the adhesion layer 3 without wrinkles or walnuts. The support frame 2 has an adhesive layer 4 on the other end surface, and a protective film 5 is placed on top of the adhesive layer 4. Such a pellicle is used by peeling off the protective film 5 and attaching it to a mask via the adhesive layer.

Incidentally, as semiconductor devices themselves become more and more integrated, the specifications regarding the size of foreign objects originally required for pellicles have become correspondingly stricter. Initially, it was possible to use the method based on the principle that even if the foreign matter on the pellicle was about 30 μm, it would not be focused because the mask pattern and the pellicle were separated during exposure. However, with the progress of integration to the megabit level, foreign particles even as small as 1 μm are becoming a problem in the corresponding pellicles attached to masks when manufacturing such semiconductor devices.

The foreign matter here includes not only so-called particles but also stains with a width of 1 μm. At this level, it is necessary to review the pellicle manufacturing method. The present inventors have found that the use of a liquid such as water used when separating the substrate and the optical thin film body, which is considered to be particularly essential in manufacturing, is a problem. Generally, when manufacturing a pellicle, the material forming the optical thin film is first dissolved in a solvent, and after filtering, the material is applied onto a smooth substrate, and the solvent is blown off to form a uniform optical thin film. Of course, one or more antireflection layers may also be coated on top. In the next step, the substrate and optical thin film layer are separated. In that case, for example, JP-A-58-219023 and JP-A-6
No. 1106243 each publication states that the entire substrate is immersed in water,
A method is described in which a naturally peeled optical thin film is stretched over a support frame with an adhesive.

Also, JP-A-59-206406 and JP-A-60-35
Japanese Patent No. 733 describes a method in which a support frame or a frame body with adhesive is fixed on an optical thin film body, the whole is immersed in water after it is cured, and the frame body is separated. A problem with such a method is that particles, particularly from the periphery of the applied membrane, diffuse into the water and adhere to the desired membrane surface area, degrading the quality of the pellicle. In order to avoid this, the pellicle is thoroughly washed with water, but stains become apparent during draining, resulting in a problem that a high-quality pellicle cannot be obtained. As a method that does not use water, JP-A-58-198.501 discloses that a release mold is formed on the substrate in advance to make it easier to peel off, and after forming the optical thin film layer, adhesive is applied. It describes how to fix a frame on top of it, harden it, then lift and remove the frame. In this method, there is a possibility that a part of the mold release agent is transferred to the optical thin film body, which becomes visible as particles or stains.

[Problems to be Solved by the Invention] The present invention solves the problems of conventional pellicles as described above.

The present invention aims to provide a pellicle of higher quality than before by reviewing the pellicle manufacturing process, that is, by using a new method of completely separating the optical thin film body and the substrate by a dry process.

More specifically, the object is to provide a high-quality pellicle that is free of defects such as stains and particles of 1 μm or larger even when visually inspected under a strong light source, and a method for manufacturing the same.

[Means for Solving the Problems] The present inventors have conducted various researches in order to solve the above-mentioned problems. It was discovered that this was due to an inappropriate method of peeling off the coated substrate. As mentioned above, conventional methods are based on the use of liquids such as water or the use of mold release agents that may generate dust. Even when the work was done carefully and carefully, in most cases particles were found to be on the desired film surface or stains were observed. We found a new method to solve this problem and completed the present invention.

That is, the present invention provides a pellicle in which an optical thin film body having a thickness within the range of approximately 0.5 μm to 10 μm is stretched over a support frame, in which at least a portion of the optical thin film body exposed to exposure light is This pellicle is characterized in that no stains become visible to the naked eye under conditions where the film surface is irradiated with a condensing light of 100 W or more over an angle of 0° to 90°.

Furthermore, it is also a pellicle in which an antireflection coating is applied to at least one side of the optical thin film body.

The method for manufacturing such a high quality pellicle according to the present invention requires the following steps. Namely, (1) a step of dissolving the material forming the optical thin film body in a solvent, applying it on the substrate after filtration, and blotting off the solvent to form a uniform optical thin film body; (2) having the above-mentioned optical thin film body on the top surface; a step of fixing the substrate and pressing a frame having an adhesive layer on at least one end surface with an elastic body interposed thereon with the adhesive layer facing downward; (2) Lifting the frame and removing the optical thin film from the substrate; Step of transferring to a frame: ■Prepare a support frame with adhesive applied to the end surface, and place the support frame with the side with the adhesive facing down on the optical thin film body transferred to the frame. These are the step of curing the adhesive, and (2) the step of cutting off the excess optical thin film.

It is a preferable embodiment to coat one or more antireflection layers on the optical thin film body subsequent to the above step (2) in order to improve the light transmittance.

Further, following the step (1) above, one or more antireflection layers are applied to the back surface of the optical thin film body, thereby completing a pellicle having antireflection layers on both sides. Of course, a pellicle with excellent light transmittance that prevents screen reflection can also be produced by applying an antireflection layer to both the front and back sides of the pellicle following the step (1) above.

The major feature of the pellicle manufacturing method according to the present invention is that it does not use any liquid such as water, and it also eliminates the need for extra steps such as applying a mold release agent on the root of the word, which is a source of dust generation. Therefore, it is possible to create a pellicle in which the stain of the present invention does not become a subject matter.

The important points of the present invention are the steps (1) to (2), and the frame used here has an adhesive layer with an elastic body interposed therebetween on at least one end surface.

The material of such a frame may be any material as long as it has appropriate flexibility, and metals, alloys, resins, etc. can be used. It is preferable that the optical thin film body transferred after the step (2) is stretched tightly and that the flatness is maintained at a certain level or higher, and a material capable of so-called shape memory also provides a preferable material for the frame body. Generally, a frame made of resin is preferable in terms of cost. Such materials include, for example, polystyrene, polystyrene copolymers, polycarbonate I, various polymer compositions having aromatic rings, heterocycles, alicyclic groups, or halogen groups other than polystyrene, melamine resins, and phenolic resins. , or various thermosetting resins such as epoxy resins, alicyclic or aromatic isocyanates and/or urethane-forming compositions consisting of these and polyols, vinyl copolymers including acrylics, polyesters (including alkyds) Examples include polymers, silicone resins, and hydrocarbon resins.

The width and thickness of the crushed body are determined mainly by the size of the substrate and the desired pellicle film, but are determined within a range that ensures flatness in the taut state. For example, when the optical thin film body is thick, the tension of the film is large, so a crushed body having a large width and thickness is preferable. Of course, if the material is strong, it may be thin. Roughly, a frame having a width and thickness of 1 to 50a++n is used. Also, the shape is round or square,
It has a shape such as an octagon. It is preferable to have a shape that matches the shape of the substrate in order to collect the film more efficiently.

The frame has an adhesive layer on one end surface with an elastic body interposed therebetween. The elastic body having an adhesive layer is held in a frame by an adhesive or an adhesive. The adhesive layer is made of acrylic, rubber, vinyl, epoxy, silicone, or the like. Examples of the elastic body include rubber or foam, such as butyl rubber, chloroprene rubber, foamed polyurethane, and foamed polyethylene. Especially if the coating substrate is made of a rigid material such as glass,
Materials other than those with sufficient elasticity are inappropriate. A preferred embodiment of such a tape is a so-called double-sided adhesive foam tape. However, there are cases where the elasticity is insufficient, so it is more preferable to provide an elastic body with an appropriate thickness. Of course, this layer can be made into multiple layers depending on the case.

The suitable strength of the adhesive will depend on the properties of the optical film. As long as the thin film body is made of a material that easily adheres, it may have relatively weak adhesive strength. However, for example, when adhering to fluorine-based materials that are very difficult to adhere to, it is necessary to use an adhesive with a fairly strong adhesive force. In general, it is preferable that the adhesion strength is 100 g/25 mIn or more according to the test method according to JIS Z 0237.
It is more preferable if it is 1000g/25mm or more.

When pressing the above-mentioned frame onto a substrate having an optical thin film body with the adhesive facing downward, it is possible to cover the top surface of the crushed body and use a roller or other means from above, or simply press the frame body with the adhesive facing downward. Force can be applied from the top. The point is that the optical thin film and the frame must be integrated over the entire end face of the frame.

Next, the process begins in which the frame is lifted using pliers or a suitable jig. Before or after placing the frame, a gas such as air may be injected between the thin film and the substrate at part or all of the peripheral end surface of the optical thin film to make lifting easier. One way to make this easier is to make a cut between the thin film body and the substrate on a part of the end face or the entire circumference and then lift it up. However, if the substrate has a smooth and clean surface, the optical thin film can be peeled off from the substrate and transferred to the frame side very easily.

The next step is to integrate the support frame and the optical thin film body transferred to the frame body. That is, adhesive is placed on the support frame, and the parts are integrated via the adhesive surface. As the support frame, aluminum alloy, plastic, etc. can be used. Its size is approximately 1 to 8 inches in diameter or 1 to 8 inches square, corresponding to the size of the mask, and its height is approximately 2 to 110ff1I. Examples of adhesives include natural products such as dextrin and starch;
Thermoplastic adhesives such as vinyl acetate resin and acrylic resin,
Thermosetting adhesives such as amino resins, phenolic resins, and epoxy resins; thermosetting adhesives such as amino resins, phenolic resins, and epoxy resins; rubber adhesives such as polychloroprene and nitrile rubber; and the like can be used. Furthermore, regarding the curing type of these adhesives, various types such as ultraviolet curing type, heat curing type, and instant curing type can be used.

It is preferable to use an adhesive that generates as little dust as possible.

The next step is a step of separating the optical thin film body transferred to the frame and the optical thin film body fixed to the support frame. A method of physically cutting with a cutter or the like or a method of cutting with a laser or the like can be used.

As the optical thin film body, a single layer body or a body having an antireflection layer can be used. Inorganic materials such as quartz and polymers can be used as the material for the film constituting the central layer. The polymer can be selected from materials with high light transmittance when formed into a thin film, such as polyethylene terephthalate, cellulose esters, polyethylene terephthalate, cellulose esters, polycarbonate, polyvinyl butyral, and polymethyl methacrylate.

In particular, commonly preferred materials include nitrocellulose, cellulose acetate, cellulose acetate butyrate,
Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate or a mixture thereof is used. These can be dissolved in a suitable solvent, filtered through a filter, applied onto a substrate by a suitable coating method such as spin coating, blade coating, roll coating, etc., and the solvent can be blown off by means such as heating.

As the material for the antireflection layer, inorganic substances such as M g F 2 and polymers such as polystyrene and Teflon can be used.

The manufacturing method according to the present invention makes it possible to produce a pellicle of extremely high quality, but since the assembly method does not use water, it is characterized by the fact that no stains appear. It is extremely difficult to check such stains. This is because if the width is about 3 μm, it is easy, but it becomes 1 μm or less. According to the detection method of the present inventors, by keeping the surroundings dark,
In other words, the condensing light is placed obliquely to the film surface of the optical thin film body.
It is characterized by irradiating light while changing the angle from 0° to 90" and visually checking the reflected light. In this case, even if there is a minute stain or particle of 1 μm or less, it can be detected. , if they exist on the film surface, their presence can be confirmed visually.As a light source, it is preferable to use a condensing light of 100W or more.Another method is to use a powerful condensing light. There is also a method of applying the pellicle to the membrane surface and observing it with a microscope.The pellicle of the present invention and its manufacturing method do not reveal defects such as stains even by such a method.

The pellicle is housed in a clean case to prevent dust from adhering to it until it is ready for use. When used in a stepper, a pellicle is often installed not only on the image side of the mask but also on other areas, since the influence of foreign substances is extremely sensitive.

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

[Examples] Example 1 Nitrocellulose (manufactured by Asahi Kasei Kogyo, H-1/2) was dissolved in ethyl lactate to a concentration of 12 mm%.

This solution was passed through a 0.2 μm filter, applied onto a smooth glass substrate (20On+nφ) using a spin coater, and dried by heating. Round ring outer diameter 19g++vφ,
Prepare a Teflon frame with a width of 5ml and a thickness of 511L11, and tape double-sided foam tape (manufactured by 3M Oki,
42B2) was pasted. The foam tape side of the crushed body was pressed onto the nitrocellulose thin film coated on the substrate, and the frame was then lifted up on a bench. The nitrocellulose membrane was transferred to a crushed body in a taut state and collected. When the optical thickness was measured, it was 2.8 μm.A light-curing type methacrylate ester adhesive (manufactured by Loctite ■, 349) was spread on a rectangular support frame made of aluminum alloy with external dimensions of 120 m1W x 98 mm. It was transferred to a frame and placed with the coated side facing down on the nitrocellulose film surface, and was cured and fixed by irradiating ultraviolet rays from the bottom surface. Next, a cutter knife was applied to the outer periphery of the frame and a careful cut was made to create a pellicle.

A condensing light (manufactured by Olympus Oki, WA-
No stains were observed even when observed by diagonally applying LSH). Further, even when the surface was inspected using a laser beam surface inspection machine (manufactured by Hitachi Engineer Frame ■, HL D-100) at a photomal voltage of G50V, no equivalent particles were detected.

Example 2 Nitrocellulose (manufactured by Asahi Kasei ■, H-174) was dissolved in ethyl lactate to form a 19% by weight solution.

In addition, a terpolymer of TFE/HFP/VdF (T F
E-50.1% by weight, RF P-29.2% by weight, V
dF -20,7m;%, n = 1.35),
Per70 rho 2-methyl-1-oxy73-thiacyclohexane-3,3-dioxide dissolved in 0.6% by weight
It was made into a solution.

A silicon wafer (8 inches) was set in a spin coater, and the nitrocellulose solution filtered through a 0.2 μm filter was dropped to form a uniform nitrocellulose coating on the wafer. After drying the wafer by heating, the TFE/HFP/VdF ternary copolymer solution was further dropped onto the wafer, followed by spin coding and air drying to form an antireflection layer.

Outer diameter of round ring made of high density polyethylene: 194 Inra
φ, width 5 mm, thickness 3), prepare a crushed body with holes in two places, first apply double-sided tape (manufactured by 3M■, 5T-416P) whose base material is polyester to the end surface, and then paste a I attached the neoprene rubber and the same double-sided tape as above. Such a frame was placed on the substrate with the coated film, then covered with a lid and pressed well with a roller. After scraping the edges of the coated area with a cutter, I inserted an insertion jig into the hole in the frame and lifted the frame. The membrane was transferred to the frame and collected.

Next, the above TFE/HFP/VdF terpolymer solution was dropped onto the film surface on the substrate side, spin coated and air dried to form an antireflection layer. A support frame was fixed in the same manner as in the example, and the outer peripheral surface of the support frame was cut with a cutter knife to create a pellicle that was anti-reflective on both sides. Even through the same inspection as in Example 1, no particles were detected, and no stains were apparent.

Comparative Example Instead of using the frame of Example 1.2, it was immersed in water,
The pellicle was created using conventional methods of separating the membrane and substrate. This pellicle was inspected in the same manner as in Example 1, and stains were detected at the edge of the film surface, and about 100 particles were also confirmed.

[Effects of the Invention] As explained above, the pellicle of the present invention has extremely few defects such as particles or stains on the film surface, and therefore can provide a pellicle suitable for the megabit era.

[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. Figure 1 Patent Applicant Asahi Kasei Electronics Co., Ltd. Agent Patent Attorney Hide Komatsu Agent Patent Attorney Hiroshi Asahi

Claims (5)

[Claims] (1) In a pellicle in which an optical thin film body having a thickness within the range of approximately 0.5 μm to 10 μm is stretched over a support frame, at least the portion of the optical thin film body exposed to the exposure light beam is heated to 100 W or more. Focusing light at 0° to 90° to the film surface
A pellicle characterized in that stains do not become visible to the naked eye under conditions of irradiation over an angle of . (2) (1) A step of dissolving the material forming the optical thin film body in a solvent, applying it on the substrate after filtration, and evaporating the solvent to form a uniform optical thin film body. (2) The above-mentioned optical thin film body A process of fixing a substrate having an upper surface and pressing a frame having an adhesive layer on at least one end surface with an elastic body interposed thereon with the adhesive layer facing downward. (3) Lifting the frame and transferring the optical thin film from the substrate to the frame. (4) Prepare a support frame with an adhesive applied to the end surface, place the support frame with the side with the adhesive facing down on the optical thin film body transferred to the frame, and apply the adhesive. hardening process 5. The method for manufacturing a pellicle according to claim 1, further comprising the step of: (5) cutting off excess optical thin film.