JP2006323178A - Pellicle for lithography, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pellicle for lithography, of which the pellicle frame is not deformed with film tension even in the case of a large frame with ≥300 mm respective edge lengths, and which satisfies a specified dimensional specification and its manufacturing method. <P>SOLUTION: The pellicle is a large sized pellicle having a pellicle film held on the pellicle frame with ≥300 mm respective edge lengths, is characterized by having the pellicle film constructed with an amorphous fluoropolymer composed of a perfluorobutenyl vinyl ether polymer, wherein the tension of the pellicle film is more than 0 N/mm and less than 2×10<SP>-2</SP>N/mm, and is obtained by: diluting the amorphous fluoropolymer composed of the perfluorobutenyl vinyl ether polymer with a solvent; applying the polymer solution to a substrate; removing the solvent therefrom by heating the substrate at a temperature of ≥180°C; subsequently sticking and fixing the obtained pellicle film to a temporary frame and releasing the film from the substrate; subsequently sticking the film to the pellicle frame; and detaching the temporary frame. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lithography pellicle used as a dust mask for a lithography mask when manufacturing semiconductor devices such as LSI and VLSI and a liquid crystal display panel, and a method for manufacturing the same.

  In manufacturing semiconductors such as LSI and VLSI and liquid crystal display panels, patterning is performed by irradiating a semiconductor wafer or liquid crystal master plate with light, but dust adheres to the exposure master plate (lithography mask) used. In this case, there is a problem that the size, quality, appearance, and the like are impaired, such as dust absorbing the light or bending, the transferred pattern is deformed, the edge is rough, and the base is stained black.

  For this reason, these operations are usually performed in a clean room, but it is difficult to always keep the exposure original plate clean even in this clean room. Therefore, a pellicle that allows exposure light to pass well as dust on the surface of the exposure original plate. The method of sticking is adopted. In this case, the dust does not directly adhere to the surface of the exposure original plate but adheres to the pellicle film. Therefore, if the focus is set on the pattern of the exposure original plate at the time of lithography, the dust on the pellicle film becomes irrelevant to the transfer.

FIG. 1 is a perspective view showing the entire pellicle, and FIG. 2 is a side sectional view thereof.
The pellicle basically has the following configuration. That is, a transparent pellicle film made of nitrocellulose, cellulose acetate, fluorine polymer, etc. that transmits light used for exposure well is made of aluminum alloy such as JIS A7075, A6061, A5052, etc., stainless steel, polyethylene, etc. with black alumite treatment A pellicle film is coated with a good solvent on the upper surface of the pellicle frame, and spread and air-dried (see Patent Document 1).

  Alternatively, the pellicle film is bonded with an adhesive such as an acrylic resin, an epoxy resin, or a fluororesin (see Patent Documents 2 and 3), and a polybutene resin or polyvinyl acetate is attached to the lower surface of the pellicle frame for mounting on the exposure master. A pressure-sensitive adhesive layer made of a resin, an acrylic resin, a silicone resin, or the like, and a reticle pressure-sensitive adhesive protecting liner for the purpose of protecting the pressure-sensitive adhesive layer are provided.

JP 58-219023 A U.S. Pat. No. 4,861,402 Japanese Patent Publication No.63-27707 JP-A-9-258433 Japanese Patent Laid-Open No. 2001-42507 Utility model registration No. 2528924

  The pellicle is placed so as to surround the pattern area formed on the surface of the mask substrate, and the pattern area is isolated from the outside of the pellicle so that dust outside the pellicle does not adhere to the pattern surface.

  In recent years, pellicle is not only used as a dust-proof cover for semiconductor lithography photomasks such as LSI and VLSI, but also in TFT circuit formation process and color filter process in the manufacturing process of high definition liquid crystal display panels. In the lithography process in the formation process, it is also used for dust protection of a photomask.

The size of the conventional pellicle for semiconductor lithography was about 150 mm square at the maximum, but the pellicle used in the lithography process of the liquid crystal display panel is 330 mm × 450 mm even for small size, and about 850 mm × 1200 mm for large size become.
When this size is reached, as shown in FIG. 3, the pellicle film is first spread on a temporary frame body that does not deform due to film tension, and then the pellicle film is transferred to the pellicle frame. In particular, the long side may be deformed inward by the tension of the pellicle film, and the dimensional specification required for the pellicle may not be satisfied.

To solve such a problem, there has been proposed a method for preventing deformation of the pellicle by dividing the pattern region of the photomask and attaching a plurality of small pellicles (see Patent Document 4).
In addition, as shown in FIG. 4, the pellicle remains large and is processed into a shape in which the long side of the pellicle frame protrudes outward in advance as shown in FIG. A method has been proposed in which the long side of the pellicle frame is deformed so as to be approximately linear (see Patent Document 5).

However, the method of Patent Document 4 cannot be applied to a mirror projection type exposure machine that requires a larger exposure area.
Further, the method of Patent Document 5 is reasonable at first glance, and a similar method has long been widely used when a film or a net having a tensile stress is stretched on a large frame having a long opposite side. However, in this method, for example, as described in Patent Document 6, it is not easy to produce a frame body having a shape that balances the tension of the spread material at all times, and there are problems such as accuracy and cost increase. It was.

  In view of the above-described problems, the present invention provides a lithography pellicle that can satisfy a predetermined dimensional specification without deformation of the pellicle frame due to film tension even if each side is a large size of 300 mm or more, and a manufacturing method thereof. The purpose is that.

The lithography pellicle of the present invention is a large pellicle that holds a pellicle film on a pellicle frame having a length of 300 mm or more on each side, and the pellicle film is an amorphous fluorine made of a polymer of perfluorobutenyl vinyl ether. It is made of a polymer, and the pellicle membrane has a tension of greater than 0 N / mm and less than 2 × 10 ⁻² N / mm. The pellicle frame is preferably selected from any one of JIS A5000, A6000, and A7000 aluminum alloys.

In the method for producing a pellicle for lithography according to the present invention, an amorphous fluoropolymer composed of a polymer of perfluorobutenyl vinyl ether is diluted in a solvent, applied onto a substrate, and heated at a temperature of 180 ° C. or higher to remove the solvent. After that, the obtained pellicle film is bonded and fixed to the temporary frame, peeled off from the substrate, and then attached to the pellicle frame, and the temporary frame is removed. At this time, in a state where the pellicle film is stretched on the temporary frame body, the film tension after being attached to the pellicle frame is greater than 0 N / mm by the amount of displacement of the temporary frame body that is elastically deformed by the tension of the pellicle film, The moment of inertia of the temporary frame is adjusted so that it is less than × 10 ^-2 N / mm.
The temporary frame is made of any aluminum alloy of JIS A5000, A6000, or A7000, and the sectional moment of inertia is 5 mm ⁴ or more and 3500 mm ⁴ or less.

  According to the present invention, by adopting the above configuration, a: high light resistance, b: little deformation of the pellicle frame, c: little damage to the mask at the time of breakage, etc. A large pellicle suitable for a lithography process in the production of a plate can be obtained.

  As a result of intensive studies to solve the above problems, the present inventor has made the pellicle film not to be deformed by keeping the tension of the pellicle film within a certain range, so that the pellicle film is not wrinkled or loosened. The inventors have found that it is possible to eliminate the problem, and have further studied, and have found a method for imparting a constant film tension to the pellicle film with good reproducibility. As a result, a pellicle with stable quality can be obtained.

Specifically, an amorphous fluoropolymer made of a polymer of perfluorobutenyl vinyl ether is used for the pellicle membrane, and the membrane tension of the pellicle is set to be greater than 0 N / mm and 2 × 10 ^-2 N / mm or less. Yes. In order to give this film tension to the pellicle with good reproducibility, when peeling the pellicle film from the film formation substrate, it has a predetermined moment of inertia as a peeling jig and has a dimension that can be elastically deformed by the pellicle film tension. A processed film peeling and holding frame (temporary frame) is used.
As a result, the pellicle membrane tension can always be kept constant at a desired value, and by setting the membrane tension within the above range, a pellicle can be obtained in which there is no deformation in the pellicle frame and the pellicle membrane is free of wrinkles and slack. .

Hereinafter, the present invention will be described in more detail with reference to the drawings.
As shown in FIGS. 1 and 2, the pellicle of the present invention has a pellicle film stretched on the upper end surface of the pellicle frame via a pellicle film bonding adhesive. Usually, a pressure-sensitive adhesive layer for reticle adhesion is formed on the lower end surface, and a liner is detachably attached to the lower end surface of the pressure-sensitive adhesive layer.

  The size of the pellicle constituent member is about the same as that of a pellicle for a lithography process used in the manufacture of a large liquid crystal display panel among normal pellicles, and the pellicle frame size is about 300 × 300 mm to 1500 × 1500 mm. The material of the pellicle frame may be a known material, but a soft material cannot be used in consideration of deformation problems. Although it may be made of steel such as stainless steel, JIS A7075, JIS A6061, JIS A5052, etc., which are preferably lightweight aluminum alloys, are preferably used.

The surface of the pellicle frame is usually roughened by sandblasting or chemical polishing, but the present invention does not impose any restrictions on the method of roughening. For example, when an aluminum material is used, the surface may be roughened by blasting the surface with stainless steel, carborundum, glass beads or the like, and further performing chemical polishing with NaOH or the like.
The anodic oxidation treatment of the pellicle frame surface can be performed by a known method, but is generally performed in an acidic electrolytic solution. As the acidic electrolytic solution, a sulfuric acid aqueous solution, an oxalic acid aqueous solution, or the like is generally used.

At least one or more ventilation holes are formed on at least one side surface of the pellicle frame, and the size, shape, number, location, etc. of the filter are the mesh size of the filter installed in the ventilation hole, the filtration area, or the ventilation required from these. What is necessary is just to set suitably according to quantity. It is preferable not to provide a vent hole that is larger than necessary, and to form a minimum vent hole.
What is necessary is just to set suitably about the shape, the number, location, etc. of the filter for dust removal installed in a vent hole similarly to a vent hole. Examples of the material of the filter include resin (PTFE, nylon 66, etc.) metal (316L stainless steel, etc.), ceramics (alumina, aluminum nitride, etc.), and the like. In addition, a chemical filter that adsorbs or decomposes chemical substances in the environment may be provided outside the dust removal filter.

As the pellicle film, an amorphous fluorine polymer made of a polymer of perfluorobutenyl vinyl ether is used, and when the pellicle film is prepared, it is dissolved in a solvent, for example, a fluorine-based solvent or the like, and a substrate, for example, a glass substrate Just apply on top.
In order to apply on the substrate, methods such as a spin coater, a bar coater, and a die coater can be employed. Other methods may be adopted as long as the characteristics required for the pellicle film are obtained.

As the adhesive for pellicle film adhesion, those conventionally used can be used, for example, fluoropolymers such as acrylic resin adhesive, epoxy resin adhesive, silicone resin adhesive, fluorine-containing silicone adhesive, etc. Can do. Among these, a silicone resin adhesive and a fluorine-based polymer are preferable in that they have high light resistance. Specific examples of the fluorine-based polymer include fluorine-based polymer CT69 (trade name, manufactured by Asahi Glass Co., Ltd.).
Examples of the adhesive for attaching the reticle include a double-sided pressure-sensitive adhesive tape, a silicone resin pressure-sensitive adhesive, and an acrylic pressure-sensitive adhesive.

The pellicle of the present invention is obtained by spreading a pellicle film on the upper end surface of the pellicle frame through an adhesive layer for attaching a pellicle film by a normal method. Usually, an adhesive layer for attaching a reticle is provided on the lower end surface of the pellicle frame, and a release layer is further attached to the release layer so as to be peelable.
The adhesive layer for attaching the pellicle film is formed by diluting with a solvent if necessary, applying it to the upper end surface of the pellicle frame, drying and curing by heating. Examples of the method for applying the adhesive include brush coating, spraying, and a method using an automatic dispenser.
As the reticle adhesive protection liner used in the present invention, various known materials can be used, and examples thereof include PET, PTFE, PFA, PE, PC, PVC, PP, and the like. A release layer suitable for the pressure-sensitive adhesive to be used is formed on the surface.

In the present invention, a pellicle film formed on a large-sized substrate is bonded to a film surface with a temporary frame having substantially the same size as the substrate, and the film is peeled off from the substrate with the temporary frame. Further, after applying an adhesive to the pellicle frame, the film peeled off by the temporary frame is attached to the adhesive surface.
The material of the temporary frame is not particularly limited as long as the film can be peeled off from the substrate without hindrance, but the dimensions are determined by the Young's modulus determined by the material so that a desired pellicle film tension can be finally obtained. It is necessary to design so that a desired moment of inertia of the cross section can be obtained from the shape. As a result, the temporary frame body bends inward according to the tension of the film, and is always stabilized at a constant film tension. In this state, the pellicle film having a desired film tension can be obtained by replacing the pellicle film from the temporary frame body to the pellicle frame.

FIG. 5 shows an example of an embodiment of the present invention.
Kariwakutai 1, the value of the second moment is in the range of 5mm ⁴ ~3500mm ^4, peeled-off pellicle film was from the substrate to Kariwakutai 1 is stretched. The temporary frame 1 is deformed by bending its long side inward due to the tension of the pellicle film. Due to this deformation, the film tension after attaching the pellicle frame becomes 0 to 2 × 10 ⁻² N / mm. A pellicle can be obtained by adhering a pellicle frame to which a film adhesive has been applied in advance to this pellicle film, and cutting and removing unnecessary films around the pellicle frame. Since the stretched pellicle film retains the film tension when peeled from the temporary frame 1, a pellicle having a desired film tension can be obtained.

The temporary frame necessary for obtaining a desired film tension can be appropriately designed by the following method.
The amount of deformation of the large pellicle frame is defined as the amount of deformation in the inner direction at the center of the side of the frame.
δ = PL ⁴ / 384EI
Is required. P is the film tension, E is the Young's modulus of the frame, I is the secondary moment of section of the frame, and L is the side length of the temporary frame. In addition, the moment of inertia of the cross section is
I = hW ^3/12
It is represented by h is the height of the pellicle frame, and W is the width of the pellicle frame.

The film tension σ ₁ affixed to the pellicle frame after deformation of the temporary frame is relaxed by the amount obtained by multiplying the displacement δ by the elastic coefficient of the film. That is, it is expressed by the following formula.
σ ₁ = σ ₀ −kδ = σ ₀ − (kPL ⁴ / 384EI) = σ ₀ − (kPL ⁴ / 32Ebh ³ )
Here, σ ₀ is the film tension when there is no deformation of the temporary frame, and k is the elastic coefficient of the film. However, if σ ₁ ≧ 0, the film material is elastically deformed, and the temporary frame is in a range where plastic deformation is not caused by film tension, any film tension between σ ₁ ≈0 and σ ₁ = σ ₀ Can be held on the pellicle.
Therefore, since the relaxed film tension obtained by deformation of the temporary frame body determines the Young's modulus if the material of the temporary frame body is determined, the shape and dimensions of the temporary frame body, that is, the moment of inertia of the cross section and the side of the temporary frame body Will be determined by the length of.

The value of the moment of inertia of the cross section can be determined arbitrarily depending on the size of the required temporary frame, but in the assumed large liquid crystal pellicle, the size of the temporary frame is estimated to be about 1400 mm on a side. preferably a 5mm ⁴ ~3500mm ^4.
FIG. 6 is a graph showing the relationship between the cross-sectional secondary moment and the amount of deformation of the temporary frame when the side length is 900 mm, 1000 mm, and 1400 mm. If the second moment of section is 3500 mm ⁴ or more, the amount of deformation of the temporary frame is too small, and the film tension after the pellicle frame is stretched cannot be adjusted to a predetermined value. On the other hand, if the cross-sectional secondary moment of the temporary frame is too small, the deformation becomes too large, and when the pellicle film is attached to the pellicle frame, the film is slackened or wrinkled.

The pellicle manufacturing method of the present invention will be specifically described below.
First, a polymer dissolved in a solvent is applied onto a large substrate by a spin coat method or the like. Further, the film is dried at a temperature near the boiling point of the solvent to form a pellicle film. Next, an adhesive is applied to a temporary frame that is approximately the same size as the substrate and is bonded to a pellicle film formed on the substrate. After bonding, the temporary frame is peeled off from the substrate, and the pellicle film is transferred to the temporary frame.

A deflection amount corresponding to the tension of the transferred pellicle film is generated in the temporary frame. At this time, when the cross-sectional second moment of the temporary frame body is set so that the film tension is 0 to 2 × 10 ^-2 N / mm when the pellicle film is spread on the pellicle frame, the temporary frame body The stretched pellicle film has a value corresponding to a film tension of 0 to 2 × 10 ⁻² N / mm after stretching on the pellicle frame.
The pellicle film spread on the temporary frame body is adhered to the pellicle frame with an adhesive, and unnecessary film portions around the pellicle frame are cut and removed with a cutter to obtain a pellicle having a film tension within a predetermined range.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
(Example 1)
First, an aluminum alloy pellicle frame made of material A5052 having an outer dimension of 474 mm × 782 mm × long side width 7.0 mm, short side width 6.0 mm, and thickness 5.5 mm was prepared. Ten vent holes with a diameter of 0.5 mm were provided in the center of one side of the pellicle frame. After cleaning the surface of the pellicle frame, glass beads were used, and the surface was roughened by surface treatment for 1 minute with a sandblasting apparatus having a discharge pressure of 1.5 kg / cm ² .

Next, after treatment for 10 seconds in a NaOH treatment bath and washing, anodization was performed at a conversion voltage of 10 V (1.3 A) in a 14% aqueous sulfuric acid solution at a liquid temperature of 18 ° C. Thereafter, the inner surface of the pellicle frame was coated with 1 μm of a silicone adhesive using a spray coating apparatus. Further, a filter having a width of 9.5 mm, a height of 2.5 mm, and a thickness of 300 μm, having a material of PTFE and a dust filtration size of 0.1 μm to 3.0 μm and 99.9999%, was attached to the vent hole provided in advance.
On the other hand, an aluminum alloy pellicle frame made of a material A7075-T651 having an outer dimension of 800 mm × 920 mm × 6 mm and a thickness of 6 mm was prepared as a temporary frame for the pellicle film.

Next, Cytop CTX809 (trade name, manufactured by Asahi Glass Co., Ltd.) was dissolved in a fluorine-based solvent, Fluorinert FC-75 (trade name, manufactured by 3M USA) to prepare a solution having a concentration of 8%. A transparent pellicle film having a film thickness of 4 μm was formed on the surface of a quartz glass substrate having an external dimension of 850 mm × 1200 mm mirror-polished by using a spin coater.
An epoxy adhesive Araldai Rapid (trade name, manufactured by Showa Polymer Co., Ltd.) was applied to the temporary frame and adhered to the pellicle on the substrate, and the pellicle film was peeled off from the substrate.

A silicone pressure-sensitive adhesive was applied to one end surface of the pellicle frame, and was dried and cured by heating at 100 ° C. for 10 minutes. A silicone-based adhesive was also applied to the other end surface of the pellicle frame, and was dried and cured by heating at 100 ° C. for 10 minutes. A PET liner was prepared and pasted with an adhesive using a liner pasting apparatus having an image processing positioning mechanism using a CCD camera.
The pellicle frame thus finished was brought into close contact with the surface of the Cytop film peeled off from the temporary frame, and the pellicle frame was heated with an IR lamp to bond the pellicle frame and the film. At this time, the pellicle frame and the temporary frame body were attached to a fixing jig with the adhesive surface of the pellicle frame facing upward, and were fixed so as not to be relatively displaced.

Next, the temporary frame frame located outside the pellicle frame is pulled up and fixed, and a cutter is applied along the periphery of the adhesive part of the pellicle frame with a tension of 0.5 g / cm applied to the film part outside the pellicle frame. The unnecessary film portion outside the pellicle frame was cut off and removed while moving.
When the deflection of the completed pellicle toward the inside of the pellicle frame was measured using a surface plate and a gap gauge, it was 100 μm or less near the center of the two long sides and 50 μm or less on the short side. In addition, there was no slack or wrinkle on the membrane.

(Example 2)
As the pellicle frame, an aluminum alloy pellicle frame made of material A7075-T651 with an outer dimension of 474 mm x 782 mm x 6.5 mm and a thickness of 7 mm is used, and as a temporary frame body of the pellicle film, the outer dimension is 800 mm x 920 mm x 5 mm, thickness A pellicle was produced in the same manner as in Example 1 except that an aluminum alloy pellicle frame made of 5 mm material A6061-T651 was used.
When the deflection of the completed pellicle toward the inside of the pellicle frame was measured using a surface plate and a gap gauge, it was 100 μm or less near the center of the two long sides and 25 μm or less on the short side. Further, no slack or wrinkle was generated on the film.

(Comparative Example 1)
As the pellicle frame, an aluminum alloy pellicle frame consisting of A5052 with outer dimensions 474 mm × 782 mm × long side width 7.0 mm, short side width 6.0 mm, thickness 5.5 mm is used. A pellicle was produced in the same manner as in Example 1 except that an aluminum alloy pellicle frame made of A6061-T651 having a size of × 920 mm × 12 mm and a thickness of 10 mm was used.
When the deflection of the completed pellicle was measured using a surface plate and a gap gauge, the film was free of slack and wrinkles, but it was 1000 μm near the center of the two long sides and 200 μm on the short side. It was.

The results are shown in Table 1 together with examples and comparative examples, including examples conducted under other conditions. In the table, ○ in the displacement column indicates that the pellicle frame has not been bent (displaced), and ○ in the film appearance column indicates that the pellicle film has no slack or wrinkles. The unit of the sectional moment is mm ⁴ and the unit of the film tension is 10 ⁻² N / mm. The unit of other numerical values is mm.

  The pellicle of the present invention is suitably used for semiconductor lithography, particularly in a TFT circuit forming exposure process for manufacturing a large liquid crystal display and a color filter forming exposure process.

It is a perspective view showing the whole pellicle. It is a sectional side view of the pellicle shown in FIG. It is a figure explaining the subject of the conventional pellicle film. It is a figure explaining the stretching method of the conventional pellicle film. It is a figure explaining the expansion method of the pellicle film | membrane by this invention. It is a graph which shows the relationship between a section secondary moment and the amount of deformation of a temporary frame.

Claims (5)

A large pellicle that holds a pellicle film on a pellicle frame having a length of 300 mm or more on each side, the pellicle film is made of an amorphous fluoropolymer made of a polymer of perfluorobutenyl vinyl ether, and the tension of the pellicle film A pellicle for lithography, characterized in that is greater than 0 N / mm and less than 2 × 10 ⁻² N / mm. 2. The pellicle for lithography according to claim 1, wherein the pellicle frame is made of any one of JIS A5000 series, A6000 series, and A7000 series aluminum alloys. Amorphous fluoropolymer composed of a polymer of perfluorobutenyl vinyl ether is diluted in a solvent and coated on a substrate, heated at a temperature of 180 ° C. or higher to remove the solvent, and the resulting pellicle film is temporarily framed. A method for producing a pellicle for lithography, characterized by being bonded and fixed to a body, peeled off from a substrate, then attached to a pellicle frame, and a temporary frame body removed. With the pellicle film stretched on the temporary frame body, the film tension after being attached to the pellicle frame is greater than 0 N / mm due to the amount of displacement of the temporary frame body that is elastically deformed by the tension of the pellicle film, 2 × 10 ^The method for manufacturing a pellicle for lithography according to claim 3, wherein the moment of inertia of the cross section of the temporary frame is adjusted to be less than ^-2 N / mm. 5. The lithography according to claim 3, wherein the temporary frame is made of an aluminum alloy of any of JIS A5000 series, A6000 series, and A7000 series, and a cross-sectional secondary moment value is 5 mm ⁴ or more and 3500 mm ⁴ or less. Pellicle manufacturing method.

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