Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2002-04-18
2004-11-02
Mohamedulla, Saleha R. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S269000, C430S271100
Reexamination Certificate
active
06811931
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
Photo-fabrication processing is widely used as a micro-precision processing method necessary in the manufacture and formation of IC lead frames, color television shadow masks, high density printed circuit boards, miniature gears and the electrodes and partitions in thin displays (LCD-PDP). The present invention relates to a photomask plate having a film surface protective layer used in this type of photo-fabrication processing. The present invention further relates to a method of manufacturing such a photomask plate having a film surface protective layer. Additionally, the present invention relates to a solution for forming a film surface protective layer used in this type of photo-fabrication processing.
In the aforementioned photo-fabrication processing, the surface to be treated is covered with a corrosion resistant film, which is then partially removed.
Next, photo-etching methods are used to chemically dissolve and remove the exposed surface. Optionally, photo-electroforming methods are used to grow a metal by electroforming.
In both of these methods, the portions of the surface which are not to be processed are covered with a corrosion resistant film, so that the processing is performed subsequent to a masking process. The masking process is typically a photographic method in which a precision made photographic image is superimposed on a photomask made of a photosensitive material which has photosensitivity to ultraviolet light. The photomask is then exposed, developed and dried. Almost all of the photomask plates used in this type of photographic method are emulsion photomasks, formed by adhering a photosensitive emulsion layer in a film state, comprising gelatin or the like as the main constituent, to the surface of a substrate.
The present invention relates to technology for forming a film surface protective layer for protecting a photomask, and in particular an emulsion photomask, of a photomask plate. 2. Background Art
Conventional photomask plates are manufactured using a CAD system, or the like, to prepare data for an exposure apparatus (such as a photo-plotter) based on a target blueprint or data Then, this data is used to perform direct writing of a pattern onto an emulsion photographic dry plate. Finally, the photographic dry plate with the pattern drawn thereon is developed, fixed, washed in water, dried, retouched, and examined.
A conventional photomask plate emulsion photomask (a film surface of a photosensitive emulsion layer), formed in this manner, comprises gelatin or the like as the main constituent. Thus, the film surface is soft and easily marked. Furthermore, other problems also exist. For example, if soiling, such as that resulting from a fingerprint, adheres to the film surface of the photomask, then subsequent removal of the soiling is difficult.
A first method of resolving this problem involves laminating an approximately 8&mgr;~12&mgr; film as a protective film onto the film surface of the photomask. However, this laminated protective film method suffers from poor sensitivity, as passage through the protective film reduces the transmittance of the ultraviolet light to approximately 50%.
A second method involves replacing the photosensitive emulsion film (emulsion photomask) with a metal film containing chromium (Cr900A) which is formed in a pattern on the surface of a glass substrate (a chrome mask) as the photomask. Chrome masks, however, are extremely expensive (between four and five times the cost of an emulsion photomask) and, consequently, suffer from being somewhat impractical.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a photomask which overcomes the foregoing problems.
It is an object of the present invention is to provide a cheap and durable photomask, by forming a second protective layer on top of an emulsion photomask produced by conventional methods. This object of the present invention overcomes the problems of the photomask being easily marked or easily soiled. Moreover, reductions in ultraviolet light transmittance, such as those observed for laminated protective films, are prevented.
Briefly stated, the present invention provides a photomask plate with a film surface protective layer characterized in that a protective layer forming solution is prepared by mixing a main constituent comprising a two-liquid cross-linked antifouling surface coating agent, prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), with a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate. This protective layer forming solution is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of the photosensitive emulsion layer (an emulsion photomask) on a substrate. The protective layer forming solution is then aged to form a film surface protective layer in a laminated manner. The resulting inexpensive and durable photomask is protected from being soiled or marked while having minimal reduction in ultraviolet light transmittance.
According to a first embodiment of the present invention, there is provided a photomask plate with a film surface protective layer, wherein a protective layer forming solution prepared by combining and mixing a mixed resin solution, comprising a fluororesin and an acrylic resin as the main constituents, and a mixed solution, comprising a polyisocyanate prepolymer as the main constituent, is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of the photosensitive emulsion layer (an emulsion photomask) on a substrate. The protective layer forming solution is then aged to form a two-liquid cross-linked film surface protective layer in a laminated manner.
This first embodiment of the present invention is characterized by the formation of a two-liquid cross-linked film surface protective layer as a second layer on the surface of a typical photomask plate produced by forming a photosensitive emulsion layer (an emulsion photomask) on a substrate. The two-liquid cross-linked film surface protective layer is a two-liquid cross-linked synthetic resin film surface protective layer produced by chemical curing when a mixed resin solution, comprising a fluororesin and an acrylic resin, and a mixed solution, comprising a polyisocyanate prepolymer as the main constituent, are mixed together and then aged. The film surface protective layer displays excellent adhesion, forms a highly durable coating on a wide variety of soft and hard materials including acrylic resins, vinyl chloride, urethane resins and glass, is a colorless and transparent liquid, displays little tendency to whiten under bending or stretching, and produces almost no reduction in the transmittance of ultraviolet light. These properties make the film surface protective layer ideal for protecting a photomask plate.
According to a second embodiment of the present invention there is provided a photomask plate with a film surface protective layer, wherein a protective layer forming solution is prepared by mixing a main constituent, comprising a two-liquid cross-linked antifouling surface coating agent prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), with a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate. The resulting protective layer forming solution is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of the photosensitive emulsion layer
Darby & Darby
Mohamedulla Saleha R.
Sineisha Co., Ltd.
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