JP2001109131A - UV resistant pellicle - Google Patents

Abstract

(57) [Problem] In a photolithography process using light having a wavelength shorter than 310 nm, the adhesive layer does not cause photodegradation, the pellicle film made of a fluoropolymer and the pellicle frame have high adhesive strength, and Provided is an ultraviolet-resistant pellicle having an adhesive layer having excellent workability such that distortion such as fine wrinkles does not occur at an adhesion site. An ultraviolet-resistant pellicle in which an adhesive layer is formed of a silicone adhesive and an organic fluorine-based adhesive, and a pellicle film is adhered and fixed to one end surface of the pellicle frame by the adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust-proof cover for protecting a photomask, a reticle, and the like (hereinafter, referred to as a mask) used in a photolithography process in LSI (Large Scale Integrated Circuit) manufacturing and the like, that is, a pellicle. It is. More specifically, the present invention relates to a UV-resistant pellicle.

[0002]

2. Description of the Related Art In the manufacture of LSI and the like, a semiconductor manufacturing apparatus such as a stepper (reduction projection exposure apparatus) is used for forming an integrated circuit pattern on a wafer. At this time, the pellicle having the transparent thin film is fixed to a mask for forming a circuit pattern via an adhesive layer formed on the pellicle frame on the side opposite to the film surface, whereby foreign substances are directly on the mask. Adhesion can be prevented. Therefore, even if foreign matter adheres to the pellicle in the photolithography process, the foreign matter does not form an image on the semiconductor wafer coated with the photoresist, and therefore, a short circuit or disconnection of the semiconductor integrated circuit due to the foreign matter image. Can be prevented, and the manufacturing yield of the photolithography process is improved.

Since the pellicle is exposed to the g-line (wavelength: 436 nm) or the i-line (wavelength: 365 nm) of a mercury lamp in the photolithography process, not only the pellicle film but also each part constituting the pellicle. That is, an adhesive for fixing the pellicle film to the pellicle frame and an adhesive for fixing the pellicle film to the mask are also required to have high light resistance. In recent years, with the development of large-scale integrated circuits, the image line width of integrated circuits has become extremely fine. Therefore, the mainstream of light sources for exposure of steppers has been changed from g-rays and i-rays to light having a further wavelength. Short XeCl excimer laser (wavelength 308
nm), KrF excimer laser (wavelength is 248n
m), ArF excimer laser (wavelength is 193 nm),
And fluorine lasers (wavelength is 157 nm). Therefore, when the above laser is used as an exposure light source, the pellicle film, the pellicle film adhesive (adhesive layer), the mask adhesive and the like have high light resistance such that they do not deteriorate even when exposed to the corresponding short wavelength light. Is required.

In particular, if the light resistance is insufficient, the adhesive layer formed on one end surface of the pellicle frame for bonding and fixing the pellicle film to the pellicle frame may be deteriorated due to a decrease in adhesive strength due to light deterioration. May loosen. Furthermore, the pellicle film surface becomes cloudy due to the generation of gas and volatile components from the adhesive layer due to light deterioration,
Since a crystalline foreign matter may be generated on the pattern surface of the mask to cause a serious trouble in the photolithography process, it is indispensable to form the mask with a material having high light resistance. In addition, when the pellicle film is made of a fluoropolymer, a practical adhesive force cannot be obtained with an acrylic adhesive or an epoxy adhesive because the fluoropolymer has excellent release properties. Therefore, a material that can exhibit sufficient adhesive strength to the fluoropolymer must be selected.

As an adhesive material satisfying such characteristics, a fluorocarbon siloxane composition (Japanese Patent Laid-Open No.
There is known a method using a so-called silicone composition such as a diorganopolysiloxane composition (Japanese Patent Application Laid-Open No. 5-216213). Further, Japanese Patent Application Laid-Open No. 6-67409 discloses that if the adhesive is made of the same or similar fluorine-based organic substance as the pellicle film, a long-life, high-performance pellicle can be obtained. However, when a fluorine-based organic material is used as an adhesive, it has excellent light resistance to short-wavelength light such as a KrF excimer laser and adhesion strength to a fluoropolymer-based pellicle film. Since the pellicle film is bonded (fused) by softening at each glass transition temperature or higher, the adhesive rapidly cures with cooling, and the cured adhesive layer is relatively hard.
There has been a problem that the pellicle film is hardened with distortion remaining in the bonded portion of the pellicle film and is likely to generate fine wrinkles, impairing the appearance of the pellicle and, in severe cases, becoming an air path and possibly causing foreign matter to enter.

On the other hand, when a silicone-based adhesive such as a fluorocarbon siloxane composition or a diorganopolysiloxane composition is used, the adhesive strength to a fluoropolymer-based pellicle film is inferior to that of a fluorine-based organic adhesive, and Since a relatively long time is required for curing, there is a problem that the pellicle film may be loosened due to deformation or film displacement of the adhesive layer during curing.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photolithography process using light having a wavelength shorter than 310 nm, particularly when the adhesive layer is subjected to photodegradation, specifically, a gas based on decomposition or volatilization of contained components. Adhesive that does not cause clouding of the inner surface of the pellicle film and mask pattern surface due to generation, has high adhesive strength, and has excellent workability such that distortion such as fine wrinkles does not occur at the bonding part in the pellicle film bonding process It is to provide a UV resistant pellicle having a layer.

[0008]

The inventors of the present invention have conducted intensive studies on an ultraviolet-resistant adhesive for a pellicle. As a result, the silicone-based adhesive phase has a property of preventing micro wrinkles from being generated at the pellicle film bonding portion, and has a The present inventors have found that the above problems can be solved by using a system-based adhesive and an organic fluorine-based adhesive, and have reached the present invention. That is, the present invention provides: A pellicle in which a pellicle film is adhered and fixed to one end surface of a pellicle frame by an adhesive layer, wherein the adhesive layer is formed of a silicone-based adhesive and an organofluorine-based adhesive, 2. 2. The ultraviolet-resistant pellicle according to 1 above, wherein the pellicle is used in ultraviolet light having a wavelength of 150 to 310 nm. 3. The ultraviolet-resistant pellicle according to 1 above, wherein the adhesive layer has one or both of a silicone-based adhesive phase and an organic fluorine-based adhesive phase. (1) The adhesive layer according to (1), wherein the adhesive layer is mainly composed of a silicone-based adhesive phase and an organofluorine-based adhesive phase.
4. UV-resistant pellicle; The silicone-based adhesive phase and the organofluorine-based adhesive phase in the adhesive layer are respectively arranged in a form of orbiting on the pellicle frame, and the silicone-based adhesive phase and the organofluorine-based adhesive phase are directed inward on the pellicle frame. 5. The ultraviolet-resistant pellicle according to 4 above, wherein the pellicles are alternately arranged in parallel from the outside toward the outside. The ultraviolet-resistant pellicle according to 5 above, wherein a silicone-based adhesive phase is disposed on the innermost side of the pellicle frame in the adhesive layer.

Hereinafter, the present invention will be specifically described. The pellicle membrane used in the present invention includes a copolymer of tetrafluoroethylene and vinylidene fluoride, a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, and a polymer containing a cyclic perfluoroether group. "Cytop" (trade name, manufactured by Asahi Glass Co., Ltd.) and "Teflon AF" (trade name, manufactured by DuPont, USA) which is a copolymer of tetrafluoroethylene and a cyclic perfluoroether group-containing fluorine monomer.
And an organic fluorine film made of a fluorine polymer such as Above all, CYTOP and Teflon AF, which are amorphous fluoropolymers, are preferably used because they exhibit extremely good light transmittance even at short wavelength light (248 nm) as used in a KrF excimer laser stepper.

A pellicle film is formed from a solution of the fluoropolymer by a spin coating method or the like, and is stretched on one end surface of the pellicle frame via an adhesive. As the pellicle frame material, conventionally known materials can be used. For example, metals such as aluminum, aluminum alloy, anodized aluminum, and stainless steel are preferable because of excellent heat resistance. In the present invention, it is necessary to use a silicone-based adhesive and an organic fluorine-based adhesive as an adhesive for stretching the pellicle film on one end surface of the pellicle frame. Further, as a result, the width of the adhesive layer formed on the pellicle frame is preferably 0.1 to 1, more preferably 0.5 to 1, and 0.8 to 1 when the frame width is 1. 1 is particularly preferred. If the width of the adhesive layer is less than 0.1 when the frame width is set to 1, the adhesive strength becomes insufficient, which is not preferable.

The silicone adhesive used as one of the adhesives is, for example, a diorganopolysiloxane having a crosslinkable functional group at both terminals or one terminal as a main component polymer (base polymer), A so-called curing agent (for example, an organohydrogenpolysiloxane having at least one hydrogen atom bonded to a silicon atom in a molecule, a diamine, a diisocyanate, a diol, or the like) or a catalyst (a platinum compound or titanium) capable of accelerating the reaction. Any compound may be used as long as it is a so-called siloxane-based adhesive composition to which a compound or the like is added.

The crosslinkable functional group which the base polymer has at both terminals or one terminal is a functional group capable of causing a cross-linking reaction between the base polymers in the presence or absence of a curing agent or a catalyst. Anything is fine. Examples of such a functional group include, for example, an alkoxy group, an alkenyl group, an epoxy group, an isocyanate group, a hydroxyl group, a chloro group, a bromo group, and a hydrogen atom, and those functional groups are directly bonded to a silicon atom. May not be combined. In addition, since the cross-linking reaction between the base polymers may be performed not only between the ends of the molecular chains but also between the side chains or between the side chains and the ends, a crosslinkable functional group may be added to the side chain of the base polymer accordingly. It may be given. Accordingly, examples of the organo group of the diorganopolysiloxane, which is the base polymer, include an alkyl group such as a methyl group and an ethyl group and a phenyl group, but may include a crosslinkable functional group as described above. Also,
The base polymer may be a so-called fluorocarbon siloxane in which a hydrogen atom of a functional group of the base polymer is replaced by a fluorine atom in order to increase its light resistance and affinity with a fluoropolymer pellicle film.

On the other hand, the organic fluorine-based adhesive referred to in the present invention, even if it is a fluorine-based polymer generally used for a fluorine resin or a fluorine coating material, has a practical problem with an organic fluoropolymer-based pellicle film. Any material can be used as long as it exhibits no adhesive strength.
For example, it is similar or similar to an organic fluoropolymer such as a copolymer of tetrafluoroethylene and vinylidene fluoride already described as a polymer material for a pellicle membrane, or a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride. They may be the same. Further, a copolymer containing a C—Cl bond or a C—H bond, such as a copolymer of chlorotetrafluoroethylene and a hydrocarbon vinyl ether, may be used. In particular, Cytop (a product of Asahi Glass Co., Ltd., a trade name) which is a polymer containing a cyclic perfluoroether group, and Teflon AF (a copolymer of tetrafluoroethylene and a fluorine monomer containing a cyclic perfluoroether group) (US DuPont's trade name) is used as a suitable fluorine-based adhesive. In the case of CYTOP or Teflon AF, the terminal may have an acryloyl group, an alkoxy group, a carboxyl group, or the like in order to enhance the adhesion to the pellicle frame.

As described above, according to the present invention, the adhesive phase composed of a silicone-based adhesive alone (the silicone-based adhesive phase in the present invention, hereinafter referred to as "S-phase") is formed by a fine particle at the pellicle film bonding portion. It is based on the finding that it has the property of preventing wrinkling, and in the present invention, the adhesive layer for bonding and fixing the pellicle film and the pellicle frame is formed of the silicone-based adhesive and the organofluorine-based adhesive. Need to be done. Both adhesives may be distributed in the adhesive layer in any manner as long as the required properties of the present invention are satisfied. For example, the two may be in a mixed state in the adhesive layer, or in addition to such a mixed state, an S phase and an adhesive phase composed solely of an organic fluorine-based adhesive (the organic fluorine-based adhesive in the present invention). (Hereinafter referred to as “F phase”), or both may coexist. The adhesive layer is S
A so-called phase-separated state mainly composed of a phase and an F phase may be used.

In the present invention, “S phase and F phase”
The phrase "mainly composed of phases" means that the two are not compatible. In this case, the structure in which both are compatibilized exists only locally at the interface between the two phases. Conversely, the above-described state is referred to as “phase-separated state” in the present invention. In the present invention, the S phase composed of a silicone-based adhesive has the property of preventing the occurrence of fine wrinkles in the pellicle film bonding portion, and the F phase composed of an organic fluorine-based adhesive has high adhesion to a fluoropolymer-based pellicle film. In order to make full use of the advantages of both, it is preferable that the adhesive layer has an S phase and an F phase, and the above advantages of the S phase and the F phase are maximized. In order to make the best use of the adhesive layer, it is preferable that the adhesive layer is in a so-called phase-separated state mainly composed of both phases.

As described above, the case where the adhesive layer is mainly composed of the S phase and the F phase is also satisfied if the requirements of the present invention are satisfied.
The phase and the F phase may be arranged in any manner in the adhesive layer. However, in order to take advantage of the small wrinkle preventing property of the S phase and the high adhesion of the F phase to the fluorine film as described above, both phases are required. Are preferably arranged in a circling manner on the pellicle frame, and the S phase and the F phase are preferably arranged alternately in parallel from the inside to the outside on the pellicle frame. Further, the pellicle film micro-wrinkles at the bonding portion naturally occur at a portion bonded to the innermost adhesive layer on the pellicle frame. Therefore, the S phase is arranged at the innermost position on the pellicle frame in the adhesive layer. Is particularly preferred.

However, even when the S phase and the F phase are applied around the pellicle frame as described above, a part of the S phase is replaced by the F phase within a range satisfying the requirements of the present invention. Or there may be places where the S phase and the F phase are mixed. Similarly, in the F phase, a part thereof may be replaced with the S phase, or there may be a portion where the S phase and the F phase are mixed. In the adhesive layer, the S phase and the F phase are "S / F / S / F / ..." or "F / S / F / S / ..." from the inner side to the outer side on the pellicle frame. ") May be arranged alternately in parallel, but in consideration of the adhesive application step, a three-phase parallel structure such as" S / F / S "or" S / F / S "is substantially used. A two-phase parallel structure such as F "is preferred. In particular, in order to utilize the anti-wrinkle property of the S phase and the high adhesive property of the F phase, and to simplify the adhesive application process, “S / F” is used from the inner side to the outer side of the frame.
It is particularly preferable to arrange two phases in parallel as described above.

The adhesive layer in the present invention may be formed through any process.
As a method of forming an adhesive layer mainly composed of a phase and an F phase, a method of sequentially applying a silicone-based adhesive and an organic fluorine-based adhesive on a frame sequentially, or a method of applying a mixture of both adhesives There is a method in which the low compatibility between the silicone polymer and the fluorine polymer is used to form a phase-separated state in a soft state, and then the film is bonded and cooled (cured). In order to control to a desired form, the former sequential alternate coating method is preferable. In the present invention, the weight ratio of the silicone adhesive and the organofluorine adhesive used for forming the adhesive layer is 5%.
/ 95 to 95/5 are preferred, and 20/80 to 70/30
Is more preferable, and 35/65 to 50/50 is particularly preferable. If the silicone-based adhesive is less than 5% by weight of the entire adhesive, fine wrinkles are likely to occur in the pellicle film bonding portion, which is not preferable. Not preferred.

In the present invention, in the adhesive layer, S
When the phase and / or the F phase are arranged in such a manner as to go around on the pellicle frame, the width of the S phase when the width of the adhesive layer on the frame is 1 is 0.01 to
0.95 is preferable, 0.10 to 0.70 is more preferable, and 0.20 to 0.50 is particularly preferable. If the width of the S phase is less than 0.01, generation of minute wrinkles cannot be sufficiently prevented, and if it is more than 0.95, the adhesive strength becomes insufficient, which is not preferable. Similarly, when the width of the adhesive layer on the frame is 1, the width of the F phase is preferably 0.05 to 0.99, more preferably 0.20 to 0.90, and 0.30 to 0.90.
0.80 is particularly preferred. When the width of the F phase is less than 0.05, the adhesive strength becomes insufficient, and when the width is more than 0.99, fine wrinkles are easily generated on the adhesive surface, which is not preferable.

As a method for indicating that the adhesive layer contains the S phase and / or the F phase, various analysis means can be considered. A simple analysis method is a micro infrared absorption spectrum method (micro IR method). ). Specifically, when microscopic IR measurement is performed on various portions of the adhesive layer, in addition to the mixed IR spectrum of the S phase and the F phase, the IR spectrum of the S phase alone or the IR spectrum of the F phase alone is obtained at the sampling location. Can be obtained. The adhesive layer of the present invention may contain a conventionally known filler, antioxidant, antioxidant, ultraviolet absorber, etc. for the purpose of improving the thermal stability, light resistance, or mechanical strength of the cured product. I do not care.

In the present invention, the thickness of the adhesive layer is 0.5
It is preferably from 500 to 500 m, more preferably from 10 to 300 m, particularly preferably from 50 to 200 m. If the thickness of the adhesive layer is less than 0.5 μm, there is a high possibility that the adhesive layer is too thin and the adhesion between the pellicle film and the pellicle frame becomes insufficient. On the other hand, if the thickness exceeds 500 μm, it is difficult to flatten the adhesive layer, and microwrinkles on the adhesive surface tend to occur, which is not preferable. The pellicle of the invention is particularly preferably used in the ultraviolet in the range from 150 to 310 nm. If the wavelength of the light is shorter than 150 nm, the adhesive layer is significantly deteriorated, which is not preferable.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically below with reference to examples and comparative examples.

EXAMPLES (Assembly of Pellicle) On one end surface of a pellicle frame made of rectangular aluminum of 150 × 120 mm (width 2)
mm), 20% by weight of CYTOP fluorine solvent solution (concentrated CTX-109A: trade name, manufactured by Asahi Glass Co., Ltd.) over the entire area of 1.5 mm width from the outside to the inside of the frame.
Is applied from a syringe at room temperature, and then
The solvent was removed (boiling point: 100 ° C.) by drying under an atmosphere of ° C. The thickness of the fluorine adhesive layer after drying was 150 μm. Subsequently, a normal temperature moisture-curable silicone-based adhesive SUP is applied to the entire area of the remaining 0.5 mm width inside the frame.
ER, X8008 Clear (trade name, manufactured by Cemedine Co., Ltd.) was applied from a syringe at room temperature to a thickness of 150 μm. In this case, the weight ratio of Cytop and SUPER, X8008 clear, which were substantially used for forming the adhesive layer, was 80/20. Next, the pellicle frame coated with the adhesive is quickly heated on a hot plate at 120 ° C., and a Cytop film (CTX-809SP2: trade name of Asahi Glass Co., Ltd.) obtained by spin coating is coated with the adhesive. Press gently against the pellicle frame surface, immediately remove it from the hot plate, and
Hold for hours. Twenty-four hours later, the pellicle was assembled by cutting off the excess film and attaching a mask adhesive on the pellicle frame opposite to the surface on which the adhesive was applied. FIG. 1 shows a schematic partial sectional view of the obtained pellicle.

(Evaluation of Pellicle) The appearance of the assembled pellicle was evaluated by observing the bonding surface with a stereoscopic microscope (20 ×), and a minute wrinkle generated at a “wrinkle” (boundary between the adhesive layer) of the pellicle film. "Was counted.
Further, in order to compare the adhesive strength between the adhesive layer and the pellicle film, air jetted from a nozzle having an inner diameter of 0.6 mmφ is blown at an angle of 45 ° with respect to the film surface from the lower part of the pellicle film surface to an arbitrary pellicle film adhesion site ( Adhesion is performed while gradually increasing the air pressure in the range of 0.5 to 5.0 kg / cm ² by using a method of spraying 10 seconds each (the distance from the nozzle tip to the bonding site is 10 mm). The measurement was performed by comparing the average values of the air pressure at 10 points when the film was peeled off from the surface.

Further, the light resistance of the adhesive layer was evaluated by applying 500 W of xenon-mercury to a pellicle attached at 1 kg / cm ² to a quartz glass mask via an adhesive provided on the side opposite to the film surface of the pellicle frame. Using a lamp,
1000J in total energy from the top of the pellicle
/ Cm ² (using an UV sensor UV25 manufactured by Oak Co., Ltd., which has the maximum light sensitivity at a wavelength of 250 nm), and visually observe the presence or absence of fogging on the pellicle film surface and mask surface after irradiation under a condensing lamp. It was evaluated by doing. Table 1 shows the evaluation results. Adhesive strength is 2.7kg / cm
² , and no fine wrinkles on the bonding surface and no fogging on the film surface and the mask surface after the irradiation of ultraviolet rays were observed.

[0025]

[Comparative Example 1] On one end surface of pellicle frame (width 2 mm)
In the above, 20% by weight of a CYTOP fluorine solvent solution (CTX-109A)
Is concentrated at room temperature from a syringe, dried under a 150 ° C. atmosphere and desolvated (boiling point: 100 ° C.) to form an adhesive layer (thickness: 1).
A pellicle was assembled in the same manner as in the example except that the thickness was 50 μm), and the same evaluation as in the example was performed. Table 1 shows the results. The adhesive strength was 2.7 kg / cm ² , and no fogging was observed on the film surface and the mask surface, but there were many fine wrinkles (28 places) on the adhesive surface.

[0026]

Comparative Example 2 On one end surface of pellicle frame (width 2 mm)
, A room-temperature moisture-curable silicone-based adhesive SUPER, X8
008 Clear (trade name, manufactured by Cemedine Co., Ltd.) is applied around the syringe at room temperature to form an adhesive layer (150 μm in thickness).
A pellicle was assembled in the same manner as in the example except that m) was formed, and the same evaluation as in the example was performed. Table 1 shows the results. No fine wrinkles on the bonding surface and no haze on the film surface and the mask surface were observed, but the bonding strength was 1.4 kg / cm ² .

[0027]

[Table 1]

[0028]

According to the present invention, the adhesive layer is lightly degraded.
Specifically, the inner surface of the pellicle film and the mask pattern surface are not clouded due to gas generation based on decomposition or volatilization of contained components, and the adhesion between the pellicle film made of fluoropolymer and the pellicle frame is good, and the pellicle is also good. It is possible to provide an ultraviolet-resistant pellicle having an adhesive layer excellent in workability such that distortion such as fine wrinkles does not occur in an adhesion portion in a film adhesion step.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of a pellicle having an adhesive layer mainly composed of a silicone-based adhesive phase and an organic fluorine-based adhesive phase in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pellicle film 2 Adhesive layer 3 Organofluorine adhesive phase 4 Silicone adhesive phase 5 Frame 6 Mask adhesive

Continuation of the front page (72) Inventor Eiji Honda 1-3-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture F-term in Asahi Kasei Kogyo Co., Ltd. 2H095 BA07 BB30 BC33 BC39 4J004 AA02 AA06 AA11 AB01 CA05 CB03 CC02 CE03 EA06 FA04 FA05

Claims (6)

[Claims] 1. A pellicle in which a pellicle film is adhesively fixed to one end surface of a pellicle frame by an adhesive layer,
A UV-resistant pellicle, wherein the adhesive layer is formed of a silicone-based adhesive and an organic fluorine-based adhesive. 2. The ultraviolet-resistant pellicle according to claim 1, wherein the pellicle is used in an ultraviolet light having a wavelength of 150 to 310 nm. 3. The ultraviolet-resistant pellicle according to claim 1, wherein the adhesive layer has one or both of a silicone-based adhesive phase and an organic fluorine-based adhesive phase. 4. The ultraviolet-resistant pellicle according to claim 1, wherein the adhesive layer mainly comprises a silicone-based adhesive phase and an organic fluorine-based adhesive phase. 5. The silicone-based adhesive phase and the organofluorine-based adhesive phase in the adhesive layer are arranged so as to go around on a pellicle frame, and the silicone-based adhesive phase and the organofluorine-based adhesive phase are pellicle-based. The ultraviolet-resistant pellicle according to claim 4, wherein the pellicles are alternately arranged in parallel from an inner side to an outer side on the frame. 6. The ultraviolet-resistant pellicle according to claim 5, wherein a silicone-based adhesive phase is disposed on the innermost side of the pellicle frame in the adhesive layer.