Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Utility Patent
1998-10-06
2001-01-02
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S328000, C430S330000
Utility Patent
active
06168908
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a cured film and a process for forming the same. More specifically, it relates to a process for forming a cured film pattern by coating a radiation sensitive resin composition on a thermosetting resin composition which is not sensitive to radiation and patterning the lower layer thermosetting resin composition, which is useful as a protective film, flattening film and interlayer insulating film of electronic parts, particularly an interlayer insulating film for liquid crystal display elements, integrated circuit elements and solid image pick-up elements.
On an electronic part such as a liquid crystal display element, integrated circuit element or solid image pick-up element, a flattening film for securing flatness for the surface of the electronic part, a protective film for preventing deterioration or damage, and an insulating film for keeping electric insulation are formed. In a thin film transistor liquid crystal display element and integrated circuit element, an interlayer film for insulating laminar wires from each other is further provided.
Due to a recent trend toward an increase in the densities of the above elements and wires in the above elements, a resin composition which can provide a film having a low dielectric constant is desired. Further, there is a case where transparency is required for an interlayer insulating film as a more important factor. Particularly, for an insulating film used in a liquid crystal display element, transparency is an essential factor. To form a transparent electrode on the insulating film, heat resistance is also an important factor.
However, when a conventional radiation sensitive resin is heated at a high temperature to form an interlayer insulating film, for example, the oxidation of the resin takes place due to the high acidity of a sensitizer contained in the resin and a film having sufficient transparency cannot be obtained. Further, the obtained film has a high dielectric constant due to high polarity.
It is therefore an object of the present invention to provide a process for forming a cured film having a low dielectric constant and excellent flatness, heat resistance, solvent resistance, transparency, insulating properties and process allowance.
Other objects and advantages of the present invention will become apparent from the following description.
The inventors of the present invention have conducted intensive studies on the above problems and have found that the above problems can be solved by using a combination of specific resin compositions.
According to the present invention, the above objects and advantages of the present invention can be attained by a process for forming a cured film, which comprises the steps of:
(1) coating an alkali-soluble thermosetting resin composition on a substrate, and baking it;
(2) coating a radiation sensitive resin composition on the coated film, and baking it;
(3) exposing the radiation sensitive resin composition on the substrate to radiation through a predetermined mask and baking it;
(4) carrying out development with an alkaline developer;
(5) immersing the substrate carrying the coated films in a stripping solution to remove the upper layer film; and
(6) heating the lower layer film of alkali-soluble thermosetting resin remaining on the substrate to obtain a cured film pattern.
The present invention will be described in detail hereinafter. A description is first given of the radiation sensitive resin composition and alkali-soluble thermosetting resin.
Radiation Sensitive Resin Composition
In the process of the present invention, the radiation sensitive resin composition preferably comprises an alkali-soluble resin, particularly a novolak resin, polyvinylphenol or copolymer of vinylphenol and other olefin copolymerizable therewith, a radiation sensitive compound, a solvent and other additives as required.
The novolak resin is obtained by polycondensing a phenol with an aldehyde in the presence of an acid catalyst. Illustrative examples of the phenol include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenyl, m-ethylphenyl, p-ethylphenol, o-butylphenol, m-butylphenol, p-butylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, p-phenylphenol, hydroquinone, catechol, resorcinol, 2-methylresorcinol, pyrogallol, &agr;-naphthol, &bgr;-naphthol, bisphenol A, dihydroxybenzoic ester, gallic ester, o-nitrophenol, m-nitrophenol, p-nitrophenol, o-chlorophenol, m-chlorophenol, p-chlorophenol and the like. Of these compounds, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,3,5-trimethylphenol, resorcinol and 2-methylresorcinol are preferred. These phenols may be used alone or in combination of two or more.
Illustrative examples of the aldehyde to be polycondensed with the phenol include formaldehyde, trioxan, paraformaldehyde, benzaldehyde, acetaldehyde, propylaldehyde, phenylaldehyde, &agr;-phenylpropylaldehyde, &bgr;-phenylpropylaldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, o-chlorobenzaldehyde, m-chlorobenzaldehyde, p-chlorobenzaldehyde, o-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, o-methylbenzaldehyde, m-methylbenzaldehyde, p-methylbenzaldehyde, o-ethylbenzaldehyde, m-ethylbenzaldehyde, p-ethylbenzaldehyde, p-n-normalbutylaldehyde, furfural, 1-naphthaldehyde, 2-naphthaldehyde, 2-hydroxy-1-naphthaldehyde and the like. Of these, formaldehyde is particularly preferred. These aldehydes may be used alone or in combination of two or more. The aldehyde is generally used in an amount of 0.7 to 3 moles, preferably 0.7 to 2 moles, based on 1 mole of the phenol.
As the acid catalyst may be used hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid or the like. The amount of the acid catalyst used is 1×10
−4
to 5×10
−1
mole based on 1 mole of the phenol.
Water is generally used as a reaction medium in the polycondensation reaction but a hydrophilic solvent may be used as a reaction medium when the phenol used in the polycondensation reaction does not dissolve in an aqueous solution of an aldehyde and the reaction is carried out in a heterogeneous system at the beginning of the reaction. The solvent used in this case is an alcohol such as methanol, ethanol or butanol; or a cyclic ether such as tetrahydrofuran or dioxane. The amount of the reaction medium used is preferably 20 to 100 parts by weight based on 100 parts by weight of the reaction raw materials.
The polycondensation reaction temperature can be suitably adjusted according to the reactivity of the reaction raw materials but is generally 10 to 200° C. After the end of the polycondensation reaction, the temperature is generally raised to 130 to 230° C. to remove the unreacted raw materials, the acid catalyst and the reaction medium remaining in the system, a volatile content is distilled off at a reduced pressure, and the novolak resin is collected.
The weight average molecular weight (to be referred to as “Mw” hereinafter) in terms of polystyrene of the novolak resin is generally in the range of 2,000 to 20,000, preferably 3,000 to 15,000. When the Mw is more than 20,000, it may be difficult to coat the composition on a wafer uniformly, and developability and sensitivity may lower. When the Mw is less than 2,000, the alkali resistance of it as the upper layer film may lower.
A polyvinylphenol and a copolymer of vinylphenol and other olefin copolymerizable therewith may also be used as the alkali-soluble resin as described above.
The copolymer may be a copolymer obtained by preparing a copolymer of t-butoxystyrene or acetoxystyrene and other olefin copolymerizable therewith and hydrolyzing it.
Illustrative examples of the other olefin copolymerizable with vinylphenol (or t-butoxystyrene or acetoxystyrene) include (meth)acryloyl group-containing radical polymerizable compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-buty
Endo Masayuki
Suzuki Masayoshi
Utaka Tomohiro
Barreca Nicole
Huff Mark F.
JSR Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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