Stock material or miscellaneous articles – Structurally defined web or sheet – Physical dimension specified
Reexamination Certificate
1998-12-14
2002-01-29
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Physical dimension specified
C428S421000, C428S422000, C428S447000, C430S005000
Reexamination Certificate
active
06342292
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to an organic thin film obtained by forming an organic thin film on a substrate followed by peeling the film therefrom, and a process for producing an organic thin film, which comprises forming an organic thin film on a substrate, followed by peeling the film therefrom, where the peeling can be made easily.
2) Description of the Related Art
One example of organic thin film obtained by forming an organic thin film on a substrate, followed by peeling the film therefrom is a pellicle, which can be used by fixing it to a photo mask or a reticle used in the photolithographic process in the production of semiconductor integrated circuits, and the photo mask or reticle will be hereinafter referred to merely as “mask”.
The pellicle is a dust cover for photomasks or reticles for use in production of large-scale integration circuits and substrates for liquid crystals.
The pellicle is provided above the mask at a specific distance from the mask. Thus, even if fine foreign matters, etc. are attached to the pellicle in the photolithographic process, none of their images is projected on a photoresist-coated semiconductor wafer. That is, by protecting a mask by a pellicle, short circuits, disconnection, etc. of semiconductor integrated circuits can be protected, thereby improving production yields of photolithographic process, and furthermore reducing number of mask cleaning operations, which leads to prolonged mask life. It is the pellicle that can attain such effects.
Light source for irradiation in the photolithographic process includes an ultrahigh pressure mercury lamp, and its g line (&lgr;=436 nm), h line (&lgr;=405 nm) and i line (&lgr;=365 nm) are used as emission lines for the irradiation.
With recent technological progress in the semiconductor industry, integrated circuits of higher density and higher degree of integration are now available and projection patterns with smaller line width and interline distance on a wafer are also now available. Consequently, light sources for irradiation with shorter wavelength are utilized now. For example, far ultraviolet rays (Deep UV) by an excimer laser of krypton fluoride (KrF), argon fluoride (ArF), etc. can be used. To meet the light sources of shorter wavelength, light-stable pellicles transparent to such higher energy radiation beams are now keenly desired.
To meet such requirements, pellicles composed of fluorine-based materials or silicon-based materials have been proposed. The materials include, for example, fluorine-based materials such as tetrafluoroethylenehexafluoropropylene-vinylidene fluoride copolymers (JP-B-63-27707), fluorine-based polymers having a perfluoro-alkyl ether ring structure, i.e. CYTOP (trademark of a product commercially available from Asahi Glass Co., Ltd., Japan), Teflon AF (trademark of a product commercially available from E.I. du Pont de Nemours & Co., Inc., USA), etc., and polymeric organosilicone compounds such as polytrimethylvinylsilane, etc. (JP-A-2-230245), etc.
A reflection-preventing single, double or multiple layer can be provided on one side or both sides of a pellicle.
Materials proposed for a reflection-preventing layer(s) as an outermost layer(s) include, for example, tetrafluoroethylene-vinylidene fluoridehexafluoro-propylene polymer (JP-A-61-209449), polyfluoroacrylate (JP-A-1-100549), fluoropolymer having a ring structure on the principal chain, i.e. Teflon AF (trademark of a product commercially available from E.I. du Pont de Nemours & Co., Inc., USA, JP-A-3-39963), CYTOP (trademark of a product commercially available from Asahi Glass Co., Ltd., Japan), etc.
Most of the materials for the outermost reflection-preventing layer are fluorine-containing polymers or inorganic fluorine materials such as calcium fluoride, magnesium fluoride, etc. Most of materials for a transparent thin film layer (central layer) are cellulose derivatives such as nitrocellulose, cellulose acetate propionate, carbonated acetyl cellulose, etc.
Such a pellicle has been so far produced by forming a film from such pellicle materials as mentioned above on a smooth substrate of glass, quartz, Si wafer or the like, followed by peeling it therefrom. A pellicle composed of fluorine-based materials or silicon-based materials, when formed on the substrate, has a high adhesiveness to the substrate, so that the film is hard to peel from the substrate, thereby leading the film to breaking or wrinkling.
When a pellicle film is to be formed on a substrate by forming the outermost reflection-preventing layer and so on successively in this order, the outermost reflection-preventing layer is hard to peel from the substrate, because it is composed of fluorine-based materials and consequently has a high adhesiveness to the substrate.
So far proposed methods for peeling the film from the substrate include, for example, a method for peeling by dipping into water (JP-A-58-219023; JP-A-60-2035733; JP-A-2-64, etc.), a method for peeling by dipping in a chemical solution and then in water (JP-A-56-83941), a method for peeling from a substrate in a wet state (JPA-62-39859), a method for peeling in an atmosphere at a relative humidity of 60% or higher (JP-A-6-67410), a method for peeling upon cooling to 5° C. or lower (JP-A-1-1-66045), etc.
However, peeling by the above-mentioned methods have such problems as deterioration of light transmissivity, uneven film thickness, etc. Particularly, dipping into water or chemical solution has such problems as contamination of pellicle films and deterioration of light transmittance. Peeling in a wet state or in an atmosphere at a relative humidity of 60% or higher has such problems as unevenness of film thickness (color unevenness and difficult process control besides the problem of deteriorated light transmittance due to the fouling of pellicle film. Furthermore, peeling upon cooling to 5° C. or lower has such problems as a failure to obtain desired effects, depending on pellicle materials, process complication, etc.
Substrate that has been once peeled off the pellicle film has such a problem as contamination of substrate surface, and thus the film-peeled substrate must be cleaned or repolished before its reuse.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a wrinkle-free organic thin film having a high light transmittance and a uniform film thickness and also to provide a process for producing an organic thin film readily peelable from the substrate, the substrate being repeatedly reusable as a recycle substrate, as distinguished over the above-mentioned prior art.
As a result of extensive studies to solve the above-mentioned prior art problems, the present inventors have found that a wrinkle-free organic thin film having a high light transmittance and a uniform film thickness can be obtained by forming an organic thin film on the surface of a substrate having a contact angle of the surface to water of 90° or higher, or particularly an organic thin film comprising a fluorine-based material or a silicon-based material on a substrate having a specific silicon compound on the surface, thereby making the formed organic thin film readily peelable from the substrate, and the substrate that has been peeled off the film repeatedly reusable as a recycle substrate, and have established the present invention.
A first aspect of the present invention is to provide an organic thin film obtained by forming an organic thin film on the surface of a substrate having a contact angle of the surface to water of 90° or higher, followed by peeling the film therefrom.
A second aspect of the present invention is to provide an organic thin film obtained by forming an organic thin film comprising a fluorine-based material or a silicon-based material on the surface of a substrate having a layer comprising a silicon compound having a perfluoroalkyl group formed on the surface, followed by peeling the film therefrom.
A third aspect of the invention is to provide an organic thin film according to the fir
Honda Eiji
Yamaguchi Tomoki
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Nakarani D. S.
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