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
2000-02-25
2001-07-10
Ashton, Rosemary E. (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
C560S116000, C562S498000, C526S271000, C526S272000, C526S281000
Reexamination Certificate
active
06258508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymer prepared by synthesizing a monomer having a derivative of cholic acid, deoxycholic acid or lithocholic acid bonded to norbornene, and then homopolymerizing the monomer, copolymerizing the monomer with maleic anhydride, or copolymerizing the monomer, maleic anhydride and 2-hydroxyethyl 5-norbornene-2-carboxylate and/or 5-norbornene-2-carboxylic acid, and its use as a photoresist.
2. Description of the Prior Art
As reported in U.S. Pat. Nos. 3,666,473, 4,115,128, and 4,173,470, the conventional photoresist is generally formed of a composition containing an alkali-soluble phenol- (or cresol)formaldehyde novolak resin and a substituted naphthoquinone diazide compound as a photosensitive substance. However, an integrated circuit increasingly has an enhanced integration degree, and a wavelength of the exposing machine used in a photographic lithography is, therefore, in the range of 200 nm to 300 nm which is a far ultraviolet region. A this far ultraviolet region, the photoresist containing the naphthoquinone as the photosensitive substance is too strong in light absorption, and low in sensitivity, such that it is difficult to use. As a result, it is necessary to develop a new photoresist capable of effectively being used at this far ultraviolet region.
The development of the new photoresist must be made such that various requirements for characteristics of the photoresist are satisfied, such as a high sensitivity, a contrast, a high resolution, and a dry etch resistance. Among these characteristics, the sensitivity is most important, and to increase the sensitivity, a concept of a chemical amplification was introduced. In this chemical amplification, activated species generated by a photochemical reaction serve as a catalyst, such that chemical reactions, such as a deprotection, and a cross-linking, can successively occur, whereby a total quantum yield of these reactions is high as compared with that of the initial catalyst production reaction.
Consequently, in order to attain the high sensitivity in a lithographic process for fabricating a semiconductor device, there are recently highly spotlighted chemical amplification type photoresists. Among them, polybisphenol protected with t-butoxycarbonyl group is reported as a resin with a greatest possibility, as described in U.S. Pat. Nos. 4,311,782, 4,405,708, and 4,491,628.
A study on a photoresist required for the development of a semiconductor chip of 1 G(giga) bit or more DRAM is actively progressive, now. Where an argon fluoride(ArF) excimer laser having a wavelength of 193 nm is used as an exposure source, polyvinylphenols according to the prior art can not be used, since they show a strong light absorption and a low sensitivity, due to aromatic rings included therein. As a result, the chemical amplification type photoresist with an alicyclic compound was proposed for the production of a photoresist fairly resistant to dry etch and transparent to argon fluoride excimer laser light of 193 nm wavelength. As for this photoresist, there was reported a structure, in which an aliphatic compound was bonded to a branched chain of an acrylic compound, or another structure, in which an aliphatic compound, as a dissolution inhibitor, is added to a polymer, as disclosed in U.S. Pat. Nos. 5,585,223, 5,691,111, and 5,756,850.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to prepare a polymer by synthesizing a monomer, in which a derivative of cholic acid, deoxycholic acid or lithocholic acid having a polycyclic aliphatic structure, and fairly resistant to dry etching and transparent to argon fluoride excimer laser having a wavelength of 193 nm, is bonded to norbornene, and then homopolymerizing the monomer, copolymerizing the monomer and maleic anhydride, or copolymerizing the monomer, maleic anhydride, and 2-hydroxyethyl 5-norbornene-2-carboxylate and/or 5-norbornene-2-carboxylic acid.
It is another object of the present invention to use the prepared polymer as a chemical amplification type photoresist.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The foregoing and other objects, features and advantages of the invention will be apparent to those skilled in the art to which the present invention relates from reading the following specification.
The present invention is to prepare a monomer, in which a derivative of cholic acid, deoxycholic acid, or lithocholic acid, which is a substance belonging in a steroid system, is bonded to norbornene, and to prepare a polymer by homopolymerizing the monomer, copolymerizing the monomer and maleic anhydride, or copolymerizing the monomer, maleic anhydride, and 2-hydroxyethyl 5-norbornene-2-carboxylate and/or 5-norbornene-2-carboxylic acid, and also to use the polymer as a chemical amplification type photoresist.
The monomer having a derivative of cholic acid, deoxycholic acid, or lithocholic acid belonging in a steroid system, which derivative is bonded to norbornene, is synthesized by the following two reaction steps. The first step is a reaction to synthesize a derivative of cholic acid, deoxycholic acid or lithocholic acid. With the first reaction, an acid group of cholic acid, deoxycholic acid or lithocholic acid is converted into a protecting group which is left by an acid. Such a first reaction is carried out at alternative temperatures of 0° C. and room temperature, under atmospheric pressure for about 24 hours. Thereafter, the second reaction is to react the protecting group-formed derivative of cholic acid, deoxycholic acid or lithocholic acid, with norbornene derivative such as 2-chloro-carbonyl-5-norbornene, at a temperature of 0° C. under atmospheric pressure for one to two hours, and then at room temperature under atmospheric pressure for five to six hours, thereby to give a compound in which a derivative of cholic acid, deoxycholic acid or lithocholic acid is bonded to norbornene. Alternatively, the protecting group-formed derivative of cholic acid, deoxycholic acid or lithocholic acid may also react with an acryloylchloride vinyl derivative at a temperature of 0° C. under atmospheric pressure for one to two hours, and then at room temperature under atmospheric pressure for five to six hours, and the resulting product is subjected to a Diels-Alder reaction, thereby to give a compound in which the derivative of cholic acid, deoxycholic acid or lithocholic acid is bonded to norbornene.
The produced monomer, in which the derivative of cholic acid, deoxycholic acid or lithocholic acid is bonded to norbornene, is homopolymerized using a radical polymerization, copolymerized with maleic anhydride using a radical polymerization, or copolymerized with maleic anhydride and 2-hydroxyethyl 5-norbornene-2-carboxylate and/or 5-norbornene-2-carboxylic acid using a radical polymerization. Examples of radical polymerization initiators useful for the radical polymerization include benzoyl peroxide, 2,2′-azobisisobutyronitrile, acetyl peroxide, lauryl peroxide, and di-t-butyl peroxide. Moreover, examples of solvents useful for the radical polymerization include benzene, toluene, tetrahydrofuran, and a combination of two or more of these solvents. The polymerization is carried out in a sealed glass tube ampule at 50 to 70° C. for 6 to 30 hours.
The monomer, in which the derivative of cholic acid, deoxycholic acid, or lithocholic acid is bonded to norbornene, has the following formula I:
where R
1
and R
2
each represent H, CH
3
, OH, CH
2
OH, CO
2
CH
3
, or CO
2
C(CH
3
)
3
with which norbornene is substituted, R
3
represents (CH
2
)
n
O(n=0 to 3), CO(CH
2
)
n
O(n=0 to 3), or COO(CH
2
)
n
O(n=0 to 3), R
4
and R
5
each represent H, OH, OCOCH
3
, OCO (CH
2
O)
n
CH
3
(n=1 to 10), OCO(CH
2
CH
2
O)
n
CH
3
(n=1 to 7), or OCOO(CH
2
,CH
2
O)
n
CH
3
(n=1 to 7), R
6
represents H, C (CH
3
)
3
, CH (CH
3
)O(CH
2
)
n
CH
3
(n=1 to 3), or a tetrahydropyranyl protecting group.
Meanwhile, the polymer prepared by homopolymerizing the m
Kim Jin Baek
Lee Bum Wook
Ashton Rosemary E.
Jenkens & Gilchrist a Professional Corporation
Korea Advanced Institute of Science and Technology
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