Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1999-01-29
2002-01-15
Ashton, Rosemary (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S280100, C430S281100, C430S287100
Reexamination Certificate
active
06338936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a photosensitive material to be used in the production of semiconductors, the production of printed circuit boards, and the working of a metallic article and more particularly to a photosensitive resin composition which is destined to form an etching resist useful for metalworking as in the production of a printed circuit board and the production of the shadow mask for a cathode ray tube. This invention further relates to a photosensitive resin composition useful for the formation of a varying sort of resin adhesive layer, the formation of a resist film such as an etching resist or a solder resist in a printed circuit board, and particularly the formation of a resin insulating layer containing via holes in the production of a multi-layer printed circuit board. This invention also relates to a method for the formation of a resist pattern or a resin insulating pattern using the photosensitive resin composition, and more particularly to a method for forming a positive resist pattern or resin insulating pattern by exposing to an active energy ray or actinic radiation a layer of the composition applied to a substrate thereby giving rise to a tack-free coating film, without inducing evaporation of an organic solvent, then subjecting the coating film to selective exposure to an active energy ray shorter in wavelength than the active energy ray mentioned above and to a heat treatment, and thereafter developing the exposed coating film with an aqueous alkaline solution.
2. Description of the Prior Art
The etching resists which are used for the formation of circuit patterns in the production of printed circuit boards or for the metalworking are classified under the pattern printing type and the developing type. As the etching resist of the pattern printing type, the composition which has varnish as a main component thereof is used, which varnish being formed by dissolving a petroleum resin or a polycarboxylic acid resin in an organic solvent. When this etching resist is printed in a prescribed pattern on a substrate and then thermally dried, it forms a coating film which is capable of resisting the etching agents. The pattern printing, however, has the problem that it is incapable of forming a fine circuit the desirability of which has been finding growing recognition in recent years.
The etching resists of the developing type are classified under the dry film type and the liquid type. Each of these types is further classified by the kind of a peeling liquid or remover under the solvent peeling type and the alkali peeling type. However, the restriction imposed on the use of the solvent peeling type has been gaining in severity on account of the problem of environmental pollution.
As a photosensitive dry film of the alkali peeling type, the film of the composition which, as disclosed in Japanese Patent Publication No. 3-68,376, has an ethylenically unsaturated compound, a photopolymerization initiator, and a film-forming polymer as main components thereof has been known. Since this film, for the sake of maintaining due strength, requires to possess a thickness of not less than 25-50 &mgr;m, it exhibits the maximum attainable resolution of about 30 &mgr;m at most and, consequently, entails the problem of being unable to form a fine pattern with resolution higher than the level just mentioned.
As a photosensitive liquid resist of the alkali peeling type, the composition which comprises the varnish having a polycarboxylic acid resin dissolved in an organic solvent, an ethylenically unsaturated compound, and a photopolymerization initiator has been known. The liquid resist formed by applying the composition to a substrate is enabled to acquire such resolution as approximating closely to 10 &mgr;m by controlling the thickness of the applied layer of the composition. Since this composition requires liquefaction with an organic solvent, however, it has the problem of entailing environmental pollution.
The photosensitive resin compositions mentioned above are the negative type. When such a composition is adopted in the production of a multilayer printed circuit board, therefore, it inevitably poses the problem that the layer of the composition deposited on a substrate must be etched after the through holes formed in the substrate have been protected with a hole filling ink, for example. Specifically, the through holes in the substrate must be blocked up in advance with the hole filling ink because part of the layer of the photosensitive resin composition deposited on the substrate which has entered the through holes escapes being hardened even when the layer is exposed to light and the unhardened part of the composition, on being exposed to the action of development, flows out of the through holes. The hole filling ink which is a substance of the thermally drying type, however, has the problem that the thermal drying thereof consumes much time and the dried coating film of the ink fails to acquire fully satisfactory smoothness. In the field of the metalworking technology, the problem of inferior dimensional accuracy arises because the negative film of the composition to be used has a remarkedly different thermal expansion coefficient from metal.
The adoption of a positive type photoresist, therefore, has been gaining in popularity in the formation of a circuit pattern on a printed circuit board or the fabrication of a shadow mask which demands accuracy.
In the positive type etching resists being developed at present, naphthoquinone diazide compounds are usually adopted as photosensitive substances. Since the naphthoquinone diazide compounds are expensive, their adoption is problematic in terms of cost. In the formation of a very fine pattern, they possibly offer no fully satisfactory resolving power.
Published Japanese Patent Application, KOKAI (Early Publication) No. (hereinafter referred to briefly as “JP-A-”) 6-295,064 discloses the photosensitive composition which comprises a polymer containing a carboxyl group (polycarboxylic acid resin), a compound containing two or more vinyl ether groups in the molecule thereof, and a compound capable of generating an acid on exposure to an active energy ray. The coating film formed of this composition, when heated (primary heating), is insolubilized in a solvent or an aqueous alkali solution because the polycarboxylic acid resin is cross-linked by the addition reaction of the carboxyl group with the vinyl ether group. The insolubilized coating film, when further exposed to an active energy ray and then heated (secondary heating), the exposed part is again solubilized in the solvent or the aqueous alkali solution because the cross-linked structure is severed by the catalytic action of the acid generated in consequence of the exposure to the active energy ray. The resist pattern aimed at is formed by removing the exposed part by the developing treatment.
It may well be concluded that the composition which contains in combination the polycarboxylic acid resin, the multifunctional vinyl ether compound, and the compound capable of generating an acid on exposure to the active energy ray as mentioned above can basically answer the recent demand for the formation of very fine circuit patterns. Since this composition contains the multifunctional vinyl ether compound, however, it has the problem that the resist coating suffers the sensitivity and the resolving power thereof to be altered by the heating conditions and the like. Specifically, since the multifunctional vinyl ether compound which functions as a cross-linking agent for the polycarboxylic acid resin in the composition has high volatility, it is liable to volatilize during the course of the primary heating and change its content in the coating film. As a result, the composition has the problem that it fails to retain the sensitivity and the resolving power constant because the conversion of the carboxyl group and the vinyl ether group (the density of cross-linkage of the polycarboxylic acid resin) is varied by the condition
Ichikawa Miyako
Saito Teruo
Sasaki Masaki
Ashton Rosemary
Rader & Fishman & Grauer, PLLC
Taiyo Ink Manufacturing Co., Ltd.
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