Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2000-02-29
2002-07-23
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S192000, C430S193000, C430S315000
Reexamination Certificate
active
06423463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive resin composition. More particularly, the present invention relates to an alkali-developable positive-tone photosensitive resin composition for forming a thick film which is suitably used for photofabrication, such as formation of bumps or wiring, or fabrication of interlayer dielectric, circuit protective films, or precision parts in the manufacture of circuit boards or mounting of a semiconductor or electronic parts on circuit boards, to a photosensitive resin film, and to a method of forming bumps using the same.
2. Description of Background Art
Photofabrication is a generic term for a technique of manufacturing various precision parts. In photofabrication, a photosensitive resin composition is applied to a substrate, that is, the surface of a processed object. The film is patterned by a photolithographic technique. The substrate is then subjected to an electroforming technique such as chemical etching, electrolysis etching, or electroplating individually or in combination using the patterned film as a mask to form precision parts. At present, photofabrication is the mainstream of precision microfabrication.
In recent years, LSIs have been highly integrated and rapidly switched over to the application of specific integrated circuits (ASIC) to deal with downsized electronic equipment. Therefore, multiple-pin thin film mounting has been demanded for installing LSIs in electronic equipment. Bare chip mounting by a tape automatic bonding (TAB) method and flip chip method has attracted attention. In such a multiple-pin mounting method, it is necessary to arrange connecting terminals, which are projection electrodes with a height of 20 &mgr;m or more (“bumps”), on the substrate with high precision. Considering further downsizing of LSIs in the future, bumps must be formed with higher precision and a narrower pitch.
The following characteristics are required for photosensitive resin compositions used for forming bumps: capability of forming a film with a thickness of 20 &mgr;m or more; patterned films having adhesion to substrates; plating resistance and good wettability with a plating solution at the time of plating for forming bumps; and capability of being easily removed by a removing solution after plating. To deal with transition to narrower pitch bumps along with highly integrated LSIs, high resolution and an excellent pattern shape in which the sidewall of the resist pattern is almost vertical are required for materials for forming bumps.
The patterned film must exhibit no cracks during plating or on washing with water and drying after plating. If cracks occur in the patterned film during plating, plating is deposited in an undesirable area, thereby causing a short circuit. If cracks occur in the patterned film after plating and it is necessary to replate to provide an adequate plating thickness, plating is deposited in the cracks during replating. This results in plating with a bad shape. Accordingly, inhibiting the occurrence of cracks during or after plating is an important requirement for photosensitive resin compositions used for forming thick plating.
However, conventional photosensitive resin compositions comprising a novolac resin, a compound containing a naphthoquinonediazido group, and other additives used as materials for forming bumps are unsatisfactory, particularly in inhibiting the occurrence of cracks. Cracks easily occur in patterned films made from such photosensitive resin compositions due to fragility. Moreover, such patterned films are removed from the substrates because of poor adhesion.
As countermeasures for solving such problems, use of polymers with a comparatively low glass transition temperature such as polyvinyl ether or acrylic resins as plasticizers has been considered. Alkali-soluble photosensitive resin compositions comprising a novolac resin, a naphthoquinonediazido group-containing compound, and polyvinyl ether are known in the art. Such photosensitive resin compositions are disclosed in U.S. Pat. No. 3,634,082, Japanese Patent Publication No. 16049/1971, and the like. Japanese Patent Publication No. 54169/1993 discloses a mixture of a novolac resin photoresist and polyvinyl methyl ether used as a material for removing the level differences in thin-film magnetic heads. However, polyvinyl ether which is soluble in an alkaline developer decreases the contrast of the photosensitive resin composition as a resist and worsen the pattern shape.
Japanese Patent Application Laid-open No. 207057/1998 discloses a positive-tone photoresist composition which comprises acrylic resins in order to mainly improve the plating resistance. This technology decreases occurrence of cracks. However, a large amount of acrylic resins added to inhibit cracks decreases the contrast as a resist and worsens the pattern shape.
An object of the present invention is to provide a photosensitive resin composition suitable for forming bumps or wiring, which is capable of producing a uniform film with a thickness of 20 &mgr;m or more, exhibits high resolution, excellent plating shape, no plating spotting out, and no cracks in the film during plating or on washing with water and drying after plating, by adding polyvinyl ether and a polyphenol derivative compound to a photosensitive resin composition comprising a novolac resin. A further object of the present invention is to provide a photosensitive resin film and a method of forming bumps using the composition.
SUMMARY OF THE INVENTION
In order to achieve the above object, the present invention provides a photosensitive resin composition comprising (A) a novolac resin with a weight average molecular weight (polystyrene-reduced value by a GPC method) of 2,000-30,000, (B) a polyvinyl lower alkyl ether, (C) a polyphenol derivative compound with a molecular weight of 200-1,000, and (D) a compound containing a naphthoquinonediazido group.
In a preferred embodiment, the above photosensitive resin composition comprises 5-60 wt % of the naphthoquinone diazido group-containing compound (D) for 100 wt % of a resin component comprising 30-90 wt % of the novolac resin (A), 5-60 wt % of the polyvinyl lower alkyl ether (B), and 3-40 wt % of the polyphenol derivative compound (C).
The present invention also provides a photosensitive resin film which is prepared by applying any one of the above-described photosensitive resin compositions to a substrate, and then drying the applied resin composition.
Furthermore, the present invention provides a method for forming projection electrodes on a substrate, comprising applying any one of the above-mentioned photosensitive resin compositions to a substrate for an electronic part; patterning the applied composition; and electroplating the substrate to a thickness of 20-100 &mgr;m, thereby forming the projection electrodes which function as connecting terminals in the completed electronic part.
The present invention will be described in more detail below.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT
(A) Novolac Resin
The novolac resin (A) used in the present invention is prepared by the addition condensation of an aromatic compound having a phenolic hydroxyl group (hereinafter referred to as “phenols”) with aldehydes preferably in a ratio of 1 mol of the phenols to 0.7-1 mol of aldehydes in the presence of catalysts. As examples of the phenols, phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphonol, o-butylphenol, m-butylphenol, p-butylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 3,6-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, p-phenylphenol, resorcinol, hydroquinone, hydroquinone monomethyl ether, pyrogallol, fluoroglycynol, hydroxydiphenyl, bisphenol A, gallic acid, gallic acid ester, &agr;-naphthol, and &bgr;-naphthol can be given. As examples of aldehydes, formaldehyde, paraformaldehyde, furfural, benzaldehyde, nitrobenzaldehyde, and acetaldehyde can be given. As acid catalysts, hydrochloric acid, ni
Hirose Kouichi
Mochizuki Isamu
Oota Masaru
Sato Hozumi
Yokoyama Yasuaki
Chu John S.
JSR Corporation
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