Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2001-12-06
2004-12-28
Kelly, Cynthia H. (Department: 1752)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S176000, C528S192000, C525S326100, C525S330300, C525S333300, C525S192000, C526S313000, C526S328000, C526S329200, C526S346000, C526S329400, C526S329600, C430S270100
Reexamination Certificate
active
06835804
ABSTRACT:
This invention relates to a method for preparing a polymer and a resist composition, typically chemically amplified positive resist composition comprising the polymer, which composition exhibits a remarkably increased contrast of alkali dissolution rate before and after exposure, a high sensitivity, high resolution, good definition of pattern profile, and minimized edge roughness and lends itself to the microfabrication of VLSI'S.
BACKGROUND OF THE INVENTION
While a number of recent efforts are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. Deep-UV lithography is capable of achieving a minimum feature size of 0.5 &mgr;m or less and, when a resist having low light absorption is used, can form patterns with sidewalls that are nearly perpendicular to the substrate.
Recently developed acid-catalyzed chemical amplification positive resists, such as those described in JP-B 2-27660, JP-A 63-27829, U.S. Pat. Nos. 4,491,628 and 5,310,619, utilize a high-intensity KrF excimer laser as the deep-UV light source. These resists, with their excellent properties such as high sensitivity, high resolution, and good dry etching resistance, are especially promising for deep-UV lithography.
Such chemically amplified positive resists include two-component systems comprising a base resin and a photoacid generator, and three-component systems comprising a base resin, a photoacid generator, and a dissolution inhibitor having acid labile groups.
For example, JP-A 6-289608 disclose resist materials using a copolymer of hydroxystyrene and (meth)acrylic tertiary ester. The resist materials of this type suffer from poor heat resistance and an indefinite pattern profile after exposure and are not satisfactory in resolution as well. This is partly because only two approaches are available for the synthesis of copolymers of hydroxystyrene and (meth)acrylic tertiary ester. One approach involves polymerizing an acetoxystyrene monomer with a (meth)acrylic tertiary ester monomer and deblocking acetoxy sites on the resulting polymer. The other approach is direct polymerization of a hydroxystyrene monomer with a (meth)acrylic tertiary ester monomer (see JP-A 61-291606). In these approaches, only radical and cationic polymerizations are possible and the resultant polymers have a very broad molecular weight distribution.
Under the current progress toward higher resolution, it would be desirable to have a resist material exhibiting good definition of pattern profile after exposure and minimized edge roughness.
SUMMARY OF THE INVENTION
An object of the invention is to provide a positive resist composition, especially chemically amplified positive resist composition, which is superior to prior art positive resist compositions in sensitivity, resolution, exposure latitude and process flexibility, and has a satisfactory pattern profile after exposure and minimized edge roughness. Another object is to provide a method for preparing a polymer which is useful as a base resin in the resist composition.
It has been found that a polymer comprising recurring units including hydroxystyrene and (meth)acrylic tertiary ester of the general formula (2) shown below, which is obtained by polymerizing an acetal group-blocked hydroxystyrene monomer with a (meth)acrylic tertiary ester monomer to form a polymer comprising recurring units of the general formula (1) shown below, and effecting selective deblocking reaction on the polymer in the presence of an acid catalyst, and especially a polymer comprising recurring units of the general formula (2) which is obtained by effecting deblocking reaction on a polymer comprising recurring units of the general formula (1) obtained by an anionic polymerization process, in the presence of an acid catalyst, is an effective base resin in a resist composition. The resist composition comprising the polymer has many advantages including an increased dissolution contrast of a resist film, high resolution, exposure latitude, process flexibility, a good pattern profile after exposure, and minimized edge roughness. The composition is thus suited for practical use and advantageously used in microfabrication, especially in VLSI manufacture.
In one aspect, the invention provides a method for preparing a polymer comprising recurring units of the following general formula (2), the method comprising the step of effecting deblocking reaction on a polymer comprising recurring units of the following general formula (1) in the presence of an acid catalyst.
Herein, R
1
and R
4
each are hydrogen or methyl; R
2
and R
3
each are a straight or branched alkyl group of 1 to 10 carbon atoms, or R
2
and R
3
, taken together, may form a ring; R
5
is hydrogen, a hydroxyl group, straight or branched alkyl group having 1 to 10 carbon atoms, substitutable alkoxy group having 1 to 10 carbon atoms, halogen atom or acid labile group; R
6
and R
7
each are hydrogen, a methyl group, alkoxycarbonyl group having 2 to 10 carbon atoms, cyano group or halogen atom; R
8
is a tertiary alkyl group of 4 to 20 carbon atoms; n is 0 or a positive integer of 1 to 4, p is a positive number, q and r each are 0 or a positive number, q and r are not equal to 0 at the same time; p1 is a positive number, p2 is 0 or a positive number, and p1+p2=p.
Preferably, the polymer comprising recurring units of formula (1) has been produced by an anionic polymerization process.
In another aspect, the invention provides a method for preparing a polymer comprising recurring units of the following general formula (2′), the method comprising the step of introducing acid labile groups into phenolic hydroxyl groups on the polymer comprising recurring units of formula (2) prepared by the method of the first aspect.
Herein R
0
is an acid labile group, p11 is 0 or a positive number, p12 is a positive number, p11+p12=p1, R
1
to R
8
, n, p1, p2, q and r are as defined above.
In a further aspect, the invention provides a resist composition comprising the polymer comprising recurring units of the general formula (2) obtained by the method of the first aspect.
One preferred embodiment is a chemically amplified positive resist composition comprising (A) an organic solvent, (B) the polymer comprising recurring units of the general formula (2) or (2′) obtained by the above method as a base resin, and (C) a photoacid generator. The resist composition may further include (D) a dissolution inhibitor and/or (E) a basic compound.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Method
The method for preparing a polymer according to the invention is to produce a polymer or high molecular weight compound comprising recurring units of the following general formula (2) from a polymer or high molecular weight compound comprising recurring units of the following general formula (1). For the sake of brevity, these polymers are simply referred to as polymer of formula (1) or (2) and more simply as polymer (1) or (2).
Herein, R
1
and R
4
each are hydrogen or methyl; R
2
and R
3
each are a straight or branched alkyl group of 1 to 10 carbon atoms, or R
2
and R
3
, taken together, may form a ring; R
5
is hydrogen, a hydroxyl group, straight or branched alkyl group having 1 to 10 carbon atoms, substitutable alkoxy group having 1 to 10 carbon atoms, halogen atom or acid labile group; R
6
and R
7
each are hydrogen, a methyl group, alkoxycarbonyl group having 2 to 10 carbon atoms, cyano group or halogen atom; R
8
is a tertiary alkyl group of 4 to 20 carbon atoms; n is 0 or a positive integer of 1 to 4, p is a positive number, p1 is a positive number, p2 is 0 or a positive number, and p1+p2=p, q and r each are 0 or a positive number, q and r are not equal to 0 at the same time.
Examples of the straight or branched alkyl group include methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl and tert-butyl. When R
2
and R
3
together bond with the carbon an
Takeda Takanobu
Watanabe Osamu
Kelly Cynthia H.
Lee Sin J.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co., LTD.
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