Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2002-03-05
2003-11-04
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...
C430S165000, C430S193000, C430S326000
Reexamination Certificate
active
06641972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoresist composition for use in the formation of thick films, as well as to a photoresist film and a method of forming bumps using the photoresist film. Specifically, the invention relates to an alkali-developable positive photoresist composition that is suitable for photofabrication such as bump formation, wiring, interlayer insulating film formation, circuit protective film formation and processing and manufacture of precision parts, carried out when circuit substrates are manufactured and semiconductors and electronic parts are packaged on the circuit substrates.
2. Description of the Related Art
The photofabrication is a generic term for techniques in which a photosensitive resin composition is coated on the surfaces of process articles and the coating films formed are patterned by photolithography, followed by chemical etching or electrolytic etching using the patterns as masks, or electroforming chiefly using electroplating, any of which are applied alone or in combination, to fabricate various precision parts. This is prevalent in the current precision fine processing techniques.
With the downsizing of electronic equipment, there are a rapid progress toward higher integration of LSIs and toward ASIC (application specific integrated circuits), and a demand for multipin thin-film packaging for mounting LSIs on electronic equipment, where the bare chip packaging carried out by the TAB system or flip-chip system has attracted notice. In such multipin packaging, protruded electrodes of 20 &mgr;m or more in height, called bumps serving as connecting terminals, must be arranged on the substrate in a high precision, and it has become more required to make the bumps higher in precision so as to be adaptable to any further miniaturization of LSIs in future.
In addition to the formation of the connecting terminals, a rewiring process is performed to form wiring between the chip and the connecting terminals in many cases. In this procedure, the wiring is patterned with the use of a thick resist film about 5 to about 20 &mgr;m in thickness.
Photoresists for the formation of thick films are used as materials for the formation of such bumps or for rewiring. The term “photoresist for the formation of thick films” (hereinafter referred to as “thick-film photoresist”) used herein means and includes resists that can form films having a thickness of at least about 5 &mgr;m on substrates. The thick-film photoresists must satisfy various requirements. For example, they must be capable of forming a film having a thickness of at least 5 &mgr;m, must have adhesion to the substrates, must be resistant to plating solutions and have good wettability to the plating solution upon metal plating for the formation of the bumps, must be capable of forming a metallic composition as a result of plating corresponding to the shape of the resist pattern, and must easily be striped with stripping solutions after plating. They also should be resistant to the plating process itself and be resistant to a plurality of plating procedures, since the plating technique becomes more advanced, and a plural plating procedures are repeated in plating process or the plating process is performed under more severe conditions.
No conventional thick-film photoresist compositions satisfy the above requirements. When a thick-film photoresist has poor adhesion to a substrate during development, the resulting patterned resist becomes liable to peel off during development with a reducing size of the pattern. A thick-film photoresist having poor resistance to plating solution induces the deformation or cracking of the patterned resist during immersing in plating solutions or during cleaning. A metallic layer which is formed by plating and does not correspond to the shape of the patterned resist induces bulging.
Japanese Patent Laid-Open Nos. 10-207057, 2000-39709, and 2000-250208 disclose thick-film photoresist compositions for use in the formation of bumps or wiring. However, these thick-film photoresist compositions cause bulging of a metallic layer obtained by plating after development and do not yield satisfactory patterns, as in the conventional equivalents. These compositions also have poor resistance to the plating process itself, cause chipping or cracking of the resist during cleaning operation after plating, and a plurality of plating procedures cannot be repeated using the same patterned resist.
In addition, using the conventional thick-film photoresist compositions, the resulting formed bumps push aside the thick-film photoresist, become bulged and have deteriorated rectangular shapes. The dimensions of the formed bumps are not in exact accordance with those of the mask pattern upon exposure due to the bulging of bumps or the deteriorated dimensional accuracy of the patterned resist. Thus, bumps cannot stably be formed.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a positive photoresist composition that is suitable for the formation of thick films, as well as to provide a photoresist film and a method of forming bumps using the photoresist film. The positive photoresist composition exhibits good adhesion to substrates during development and high resistance to plating solution, can be satisfactorily developed with alkali developing solutions, can satisfactorily be striped from the substrate in unexposed portions, can form a plated metallic layer stably having a rectangular cross section, is highly resistant to plating processes and is suitable as a material for the formation of bumps.
Specifically, the present invention provides, in an aspect, a positive photoresist composition for the formation of a thick film 5 to 100 &mgr;m in thickness. The composition includes an alkali-soluble novolak resin (A), an alkali-soluble acrylic resin (B), and a quinonediazido-group-containing compound (C), and the alkali-soluble acrylic resin (B) includes 30% to 90% by weight of a constitutional unit (b1) derived from a polymerizable compound having an ether bond;and 2% to 50% by weight of a constitutional unit (b2) derived from a polymerizable compound having a carboxyl group.
The composition may include 100 parts by weight of the alkali-soluble novolak resin (A), 5 to 50 parts by weight of the alkali-soluble acrylic resin (B), and 5 to 100 parts by weight of the quinonediazido-group-containing compound (C).
The alkali-soluble acrylic resin (B) preferably has a weight average molecular weight of 10000 to 800000.
The quinonediazido-group-containing compound (C) preferably includes a quinonediazidosulfonyl ester of a compound represented by following Formula (1) or (2):
wherein R
1
, R
2
, R
3
, R
4
, R
5
, R
6
and R
7
are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms or a substituted or unsubstituted cycloalkyl group having 4 to 8 carbon atoms.
The present invention provides, in another aspect, a photoresist film being formed on a substrate by the application of the positive photoresist composition and having a thickness of 5 to 100 &mgr;m.
In addition and advantageously, the present invention provides a method of forming bumps. The method includes the steps of applying the positive photoresist composition on a substrate of an electronic part to thereby form a resist film as a coating, irradiating the resist film with active light or radiant ray through a mask having a predetermined pattern, developing the exposed resist film, and plating the portions from which the resist film has been removed.
The positive photoresist composition according to the present invention is suitable for the formation of thick films, exhibits good adhesion to substrates during development and high resistance to plating solution, can be satisfactorily developed with an alkali developing solution, can be satisfactorily striped from the substrate in unexposed portions, can form a plated metallic layer stably having a rectangular cross section, is highly resistant to pla
Komano Hiroshi
Misumi Kouichi
Okui Toshiki
Saito Koji
Chu John S.
Tokyo Ohka Kogyo Co. Ltd.
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