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
2000-07-19
2001-11-06
Baxter, Janet (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
C430S905000, C430S909000, C430S910000, C430S325000, C430S326000, C526S313000, C526S326000
Reexamination Certificate
active
06312870
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polymers that are useful in photoresist compositions. More particularly, the present invention relates to polymers containing t-butyl cinnamate useful in photoresist compositions, which produce high resolution photoresist patterns with improved etch resistance.
2. Description of Related Art
Photoresist compositions containing copolymers of t-butyl acrylate or methacrylate, and hydroxy styrene monomers are known in the art.
The t-butyl acrylate moiety retards the alkaline solubility of the resist film in unexposed areas. In the exposed area, photogenerated acid and heat causes decomposition of the t-butyl ester group to a carboxylic acid, enhancing the alkaline solubility of the exposed area of the film. While some lithographic properties, such as shape of profile, linked to alkaline solubility improve as the amount of t-butyl acrylate is increased in the copolymer, other properties such as plasma-etch resistance suffer as the amount of hydroxy styrene is decreased.
Plasma etching is a well known method for producing microstructures on a substrate. Etching of the photoresist must be controlled and precise. Variables that must be considered during this process include power level, temperature, pressure, design, and etchant chemistry. The role of the photoresist also influences the etching process. For example, aromatic groups in a photoresist composition affects the etching stability and etch selectivity. That is, certain polymers in the photoresist composition affect the etch resistance, which is an indication of the etch selectivity. By manipulating the etch selectivity, control and precision of the etching process can be improved.
Accordingly, it is desireable to have a photoresist composition that provides desired shape and profile properties, while demonstrating improved etch resistance, i.e. etch selectivity.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a photosensitive resist composition comprising a polymer of t-butyl cinnamate, a photoacid generator, and a solvent. The polymers of t-butyl cinnamate that are useful in the present invention have monomeric units of:
wherein a 0.3 to0.9, b=0.1 to 0.7, and c=0 to 0.3; R
1
=H, methyl, or CH
2
OR
4
; R
4
=H or C1-C4 alkyl group; R
2
=H, methyl, CH
2
OR
4
, CH
2
CN, or CH
2
X; X=Cl, I, Br, F, or CH
2
COOR
5
; R
5
=C1-C4 alkyl group; and R
3
=isobornyl, cyclohexyl methyl, cyclohexyl ethyl, benzyl, or phenethyl.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides photoresist compositions containing polymers of t-butyl cinnamate that advantageously improves the resolution and shape of a photoresist pattern obtained upon exposure, while exhibiting improved etch resistance. The compositions contain polymers of t-butyl cinnamate, a photoacid generator, and a solvent.
The polymers of t-butyl cinnamate have the monomeric units of:
wherein a=0.3 to 0.9, b=0.1 to 0.7, and c=0.3; R
1
=H, methyl, or CH
2
OR
4
; R
4
=H or C1-C4 alkyl group; R
2
=H, methyl, CH
2
OR
4
, CH
2
CN, or CH
2
X; X=Cl, I, Br, F, or CH
2
COOR
5
; R
5
=C1-C4 alkyl group; and R
3
=isobornyl, cyclohexyl methyl, cyclohexyl ethyl, benzyl, or phenethyl.
These polymers can be prepared by copolymerizing t-butyl cinnamate with acetoxy styrene and subsequently converting the resulting acetoxy styrene/t-butyl cinnamate copolymer to hydroxy styrene/t-butyl cinnamate copolymer, as shown by the following reaction sequence:
The polymer of t-butyl cinnamate formed in the previously shown reaction, has the monomeric units:
where a=0.3 to 0.9; b=0.1 to 0.7; and a=b=1.0. The monomeric units are about 30 to 90 mole % hydroxy styrene and about 10 to 70 mole % t-butyl cinnamate. Preferably, there is about 50 to 90 mole % hydroxy styrene and about 10 to 50 mole % t-butyl cinnamate in the copolymer. This polymer may alternatively be prepared by directly copolymerizing hydroxy styrene with t-butyl cinnamate. This is accomplished through any known method of polymerization. For example, anionic or free radical polymerization may be used. Any of the commonly used polymerization initiators or catalysts may be used.
The polymer of t-butyl cinnamate may be modified by including a non-alkali solubilizing monomeric unit in the polymer and/or by attaching an acid-labile group such as acetal, tertiary butoxycarbonyl (t-Boc), tetrahydropyranyl esters (THP) or butoxycarbonylmethyl (BocMe) to a portion of the hydroxy groups of the styrene to yield a polymer having the monomeric units:
wherein a=0.3 to 0.9, b=0.1 to 0.7, c=03, d=0 to 0.2, e=0 to 0.2, f=0 to 0.2, and a+b+c+d+e+f=1.0; R
1
=H, methyl, or CH
2
OR
4
; R
4
=H or C1-C4 alkyl group; R
2
=H, methyl, CH
2
OR
4
, CH
2
CN, or CH
2
X; X=Cl, I, Br, F, or CH
2
COOR
5
; R
5
=C1-C4 alkyl group; R
3
=isobornyl, cyclohexyl methyl, cyclohexyl ethyl, benzyl, or phenethyl; R
6
=methyl or ethyl; R
7
=a cyclic or acyclic group selected from a cyclic, bicyclic, linear, or branched alkyl group, halogen substituted alkyl group, aromatic group, substituted aromatic group selected from phenyl, benzyl, phenethyl, naphthyl, or naphthyl ethyl groups which groups optionally contain one or more heteroatoms such as S, O, or N; x is 0 or 1, and R
8
is H, C1-C4 alkyl group, C1-C4 alkoxy group, or an acetoxy group.
Preferably, a=0.3 to 0.7, b=01 to 0.7, c=0 to 0.3, d=0 to 0.2, e=0 to 0.2, f=0 to 0.2, and c+d+e+f=0.2 to 0.5.
The non-alkali solubilizing monomer may be, for example, styrene, 3-methyl styrene, tertiary-butyl styrene, acetoxy styrene, methyl(meth)acrylate, isobomyl (meth)acrylate, adamentyl (meth)acrylate, phenyl (meth)acrylate, phenethyl (meth)acrylate, and cyclohexyl acrylate.
In an alternate embodiment, the monomeric unit:
may be replaced with the monomeric unit:
where R
9
may be any acid-cleavable hydrocarbon group having 1-10 carbon atoms and b is defined as noted above. Examples include, but are not limited to t-amyl, 2,3-dimethyl butyl, 3-methyl pentyl, 2-methyl adamentyl, 2-ethyl adamentyl, methyl cyclohexyl, and methyl cyclopentyl.
The radiation sensitive composition includes a photoacid generator (PAG), which is also known as a photoinitiator. The function of the PAG is to produce an acid upon exposure to radiation/photolysis. The acid reacts with the polymer to produce alkali soluble carboxylic acid groups in a chemically amplified reaction.
Any suitable photoacid generator compound may be used in the photoresist composition. The photoacid generator compound may be, for example, onium salts such as diazonium, sulfonium, sulfoxonium and iodonium salts, and sulfone compounds, sulfonate compounds, sulfonimide compounds, diazomethane compounds, and disulfones. In addition, suitable photoacid generator compounds are disclosed in U.S. Pat. No. 5,558,978 and U.S. Pat. 5,468,589, which are incorporated herein by reference.
Sulfonium salts such as triphenylsulfonium perfluoro octane sulfonate and triphenylsulfonium perfluoro butane sulfonate are further examples of suitable photoacid generators. A comprehensive listing and description of sulfonium and iodonium photoacid generators that can be included in the present composition is found in U.S. Pat. 6,010,820, which is incorporated herein by reference.
Additional examples of suitable photoacid generators are phenacyl p-methylbenzenesulfonate, benzoin p-toluenesulfonate, &agr;-(p-toluene-sulfonyloxy)methylbenzoin 3-(p-toluenesulfonyloxy)-2-hydroxy-2-phenyl-1-phenylpropyl ether, N-(p-dodecylbenzenesulfonyloxy)-1,8-naphthalimide and N-(phenyl-sulfonyloxy)-1,8-napthalimide.
Other suitable photoacid generator compounds are o-nitrobenzaldehydes, which rearrange on actinic irradiation to give o-nitrosobenzoic acids such as 1-nitrobenzaldehyde and 2,6-nitr
Allyn Whewell
Eisele Jeffrey
Ferreira Lawrence
Malik Sanjay
Arch Specialty Chemicals, Inc.
Baxter Janet
Lee Sin J.
Ohlandt, Greeley, Ruggerio & Perle, LLP
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