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
1999-09-24
2001-08-28
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
C430S326000, C526S281000, C549S045000, C549S300000
Reexamination Certificate
active
06280898
ABSTRACT:
This invention relates to (1) a compound having a specific lactone-containing structure, (2) a polymer comprising units of the compound which is blended as a base resin to formulate a resist composition having improved substrate adhesion, adequate penetration of developer, and high etching resistance, and especially suited as micropatterning material for VLSI fabrication, (3) a method for preparing the polymer, (4) a resist composition comprising the polymer, and (5) a patterning method using the resist composition.
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. In particular, photolithography using a KrF or ArF excimer laser as the light source is strongly desired to reach the practical level as the micropatterning technique capable of achieving a feature size of 0.3 &mgr;m or less.
As the base resin in a resist material having high transmittance to light of an excimer laser, especially ArF excimer laser having a wavelength of 193 nm, polyacrylic or polymethacrylic acid derivatives and polymers comprising aliphatic cyclic compounds such as norbornene-maleic anhydride copolymers in the backbone are used. For the base resin used in chemical amplification type resist compositions, not only an acid liability closely related to resolution, but also etching resistance and substrate adhesion are required. In the above-described resins, it is intended to accomplish such distinct characteristics by using a plurality of monomers having different properties to form a complex copolymer. However, these resins are not yet satisfactory on the practical level.
More particularly, monomers having as suspending groups polycyclic hydrocarbon groups such as adamantyl, tricyclodecyl and norbornyl are used for imparting etching resistance, and monomers having as suspending groups polar groups such as hydroxyl and carboxyl groups are used for imparting substrate adhesion. However, in a system where an extremely hydrophobic monomer for imparting etching resistance and an extremely hydrophilic monomer for imparting substrate adhesion are admixed, it is difficult to effect uniform polymerization reaction. Due to side reaction, homopolymers and undesired block copolymers can form. If the polymer product thus obtained is blended in a resist composition, this resist suffers from drawbacks including uneven dissolution due to in-film delamination, pattern collapse due to peeling of highly hydrophobic sites, and swelling due to random penetration of a liquid developer to highly hydrophilic sites. Even though the etching resistance is improved, the resolution of the resist is extremely reduced.
SUMMARY OF THE INVENTION
An object of the invention is to provide (1) a lactone-containing compound capable of forming a polymer possessing a well-balanced profile of etching resistance and substrate adhesion, (2) a polymer comprising units of the compound which is blended as a base resin to formulate a resist composition having significantly improved resolution and etching resistance over prior art compositions, (3) a method for preparing the polymer, (4) a resist composition comprising the polymer as a base resin, and (5) a patterning method using the resist composition.
We have found that a novel lactone-containing compound of the general formula (1) obtained by a method to be described later is useful as a starting reactant from which a polymer possessing both etching resistance and substrate adhesion is prepared; that a resist composition using as the base resin a novel polymer obtained from the compound and having a weight average molecular weight of 1,000 to 500,000 is improved in resolution and etching resistance; and that the resist composition is very useful in precise microfabrication.
In a first aspect, the invention provides a lactone-containing compound of the following general formula (1):
wherein R
1
is hydrogen, methyl or CH
2
CO
2
R
5
, R
2
is hydrogen, methyl or CO
2
R
5
, R
3
is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R
4
is hydrogen or CO
2
R
5
, R
5
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, and X is CH
2
, CH
2
CH
2
, O or S.
In a second aspect, the invention provides a polymer comprising units of the following general formula (1a) and having a weight average molecular weight of 1,000 to 500,000,
wherein R
1
to R
4
and X are as defined above.
The polymer may further include units of at least one of the following general formulae (2a) to (10a).
Herein, R
1
and R
2
are as defined above,
R
6
is hydrogen or a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms,
at least one of R
7
to R
10
is a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms, and the remainder are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
7
to R
10
, taken together, may form a ring, and when they form a ring, at least one of R
7
to R
10
is a carboxyl or hydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms, and the remainder are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms,
R
11
is a monovalent hydrocarbon group of 3 to 15 carbon atoms containing a —CO
2
— partial structure,
at least one of R
12
to R
15
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO
2
— partial structure, and the remainder are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
12
to R
15
, taken together, may form a ring, and when they form a ring, at least one of R
12
to R
15
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO
2
— partial structure, and the remainder are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms,
R
16
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclic hydrocarbon group,
R
17
is an acid labile group, and
k is equal to 0 or 1.
In a third aspect, the invention provides a method for preparing a polymer, comprising effecting radical or anionic polymerization between a lactone-containing compound of the general formula (1) and another compound having a carbon-to-carbon double bond.
In a fourth aspect, the invention provides a resist composition comprising the polymer defined above. Preferably, the resist composition further includes a photoacid generator capable of generating an acid upon exposure to high-energy radiation or electron beams, and an organic solvent.
In a fifth aspect, the invention provides a method for forming a resist pattern comprising the steps of (i) applying the resist composition onto a substrate to form a film, (ii) heat treating the film and then exposing it to high-energy radiation or electron beams through a photo mask, and (iii) optionally heat treating the exposed film and developing it with a developer.
The polymer or high molecular weight compound comprising units of the lactone-containing compound of formula (1) has a high etching resistance and sufficient substrate adhesion and eliminates the drawbacks of prior art resist materials including uneven dissolution due to in-film delamination, pattern collapse due to peeling of highly hydrophobic sites, and swelling due to random penetration of a liquid developer to highly hydrophilic sites.
The lactone-containing compound of formula (1) possesses both polarity attributable to the lactone structure and rigidity attributable to the fused tricyclic structure within a common molecule. When copolymerization is effected using this lactone-containing compound, there is obtained a uniform polymer exhibiting a satisfactory dissolution behavior in that separation between hydrophilic sites and hydrophobic sites does not occur as a matter of principle. In t
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nishi Tsunehiro
Watanabe Osamu
Ashton Rosemary
Baxter Janet
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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