Copolymer resin, preparation thereof, and photoresist using...

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

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C560S120000, C522S113000, C526S318000

Reexamination Certificate

active

06348296

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a copolymer resin for a photoresist used with an ultra-shortwave light source such as KrF or ArF, a process for preparation thereof, and a photoresist using the same. More specifically, it relates to a photoresist resin wherein a 2,3-t-butyl-5-norbornene-2,3-dicarboxylate unit has been introduced into a norbornene-maleic anhydride copolymeric structure. The photoresist is preferably used in lithography processes using KrF(248 nm) or ArF(193 nm) light sources which are typically used in the manufacture of 1G or 4G Dynamic Random Access Memory (“DRAM”) semi-conductor integrated circuits.
2. Description of the Prior Art
In general, etching resistance, adhesiveness, and low light absorption at 193 nm wavelength are required for a copolymer resin to be useful as a photoresist for ArF light sources. The copolymer resin is also preferably developable by using 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution. However, it is very difficult to synthesize a copolymer resin satisfying all these properties. Up to the present time, many researchers have focused their studies on novolac type resins to increase transparency at 193 nm wavelength and increase etching resistance. Researchers at Bell Labs have tried to introduce an alicyclic unit to the backbone chain of the copolymer resin in order to enhance etching resistance. For example, a copolymer resin has been suggested in which the backbone chain has norbornene, acrylate and maleic anhydride substituents, as represented by the following Formula I:
In the copolymer resin of Formula I, the maleic anhydride portion (identified by the letter A) is used for polymerizing the alicyclic olefin unit. However, the maleic anhydride portion is very soluble in 2.38% aqueous TMAH solution, even if it has not been exposed to the ArF light source, so that ‘top loss’ phenomenon (the top of the pattern being formed in a round shape) occurs in practical photoresist patterning. Thus, the copolymer resin of Formula I cannot be used as a photoresist for ArF sources.
In order to prevent such dissolution, it has been proposed to greatly increase the value of “y” in Formula I, thereby increasing the tert-butyl substituent. However, an increase in “y” causes a relative decrease in the value of “z”. The relative decrease of the “z” portion, which enhances sensitivity and adhesiveness with the substrate, causes disadvantages in practical patterning in that the photoresist tends to be removed from the wafer so that a pattern cannot be formed.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a 2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate unit having two protective groups is introduced into a norbornene-maleic anhydride copolymer structure, resulting in a copolymer resin having a high transparency at 193 nm wavelength and high etching resistance. The copolymers of the present invention can be easily prepared by conventional radical polymerization, and prevent top loss phenomenon, exhibit enhanced adhesive strength and show excellent resolution of 0.13 &mgr;m in patterning applications.
It is an object of the present invention to provide a copolymer resin comprising a 2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate unit.
It is another object of the present invention to provide a process for preparing the copolymer resin comprising a 2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate unit.
It is still another object of the present invention to provide a photoresist comprising the above norbornene-maleic anhydride copolymer resin.
It is still further object of the present invention to provide a semiconductor element manufactured by using the above copolymer resin as a photoresist.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a copolymer resins comprising a 2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate unit, represented by the following Formula III:
The copolymer resins according to the present invention preferably include the following norbornene-maleic anhydride copolymer resins:
(1) Poly[2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate/2-hydroxyethyl-5-norbornene-2-carboxylate/maleic anhydride/5-norbornene-2-carboxylic acid] copolymer resin (molecular weight: 3,000-100,000) having the following Formula IV:
wherein, the ratio x:y:z is (0.001-99%):(0-99%):(0-99%);
(2) Poly[2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate/2-hydroxyethyl-5-norbornene-2-carboxylate/maleic anhydride/mono-methyl cis 5-norbornene-endo-2,3-dicarboxylic acid] copolymer resin (molecular weight: 3,000-100,000) having the following Formula V;
wherein, the ratio x:y:z is (0.001-99%): (0-99%): (0-99%);
(3) Poly[2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate/2-hydroxypropyl-5-norbornene-2-carboxylate/maleic anhydride/5-norbornene-2-dicarboxylic acid] copolymer resin (molecular weight: 4,000-100,000) having the following Formula VI:
wherein, x is a mole % of 0.001-99%, more preferably is 0.5-99%, and y and z are independently a mole % of 0.1-99%; and
(4) Poly[2,3-di-t-butyl-5-norbornene-2,3-dicarboxylate/2-hydroxypropyl-5-norbornene-2-carboxylate/maleic anhydride/mono-methyl cis 5-norbornene-endo-2,3-dicarboxylate] copolymer resin (molecular weight: 4,000-100,000) having the following
wherein, the ratio x:y:z is (0.001-99%): (0-99%): (0-99%).
The copolymer resin of Formula IV can be prepared according to the present invention by reacting 2,2-di-t-butyl-5-norbornene-2,3-dicarboxylate, 2-hydroxyethyl-5-norbornene-2-carboxylate, maleic anhydride and 5-norbornene-2-carboxylic acid in the presence of a conventional polymerization initiator, as below illustrated in Reaction Scheme I.
The copolymer resin of Formula V can be prepared according to the present invention by reacting 2,2-di-t-butyl-5-norbornene-2,3-dicarboxylate, 2-hydroxyethyl-5-norbornene-endo-2,3-dicarboxylic acid, maleic anhydride and mono-methyl cis-5-norbornene-endo-2,3-dicarboxylic acid in the presence of a conventional polymerization initiator, as below illustrated in Reaction Scheme II.
The copolymer resin of Formula VI can be prepared according to the present invention by reacting 2,2-di-t-butyl-5-norbornene-2,3-dicarboxylate, 2-hydroxypropyl-5-norbornene-2-carboxylate, maleic anhydride and 5-norbornene-2-carboxylic acid in the presence of a conventional polymerization initiator, as below illustrated in Reaction Scheme III.
The copolymer resin of Formula VII can be prepared according to the present invention by reacting 2,2-di-t-butyl-5-norbornene-2,3-dicarboxylate, 2-hydroxypropyl-5-norbornene-2-carboxylate, maleic anhydride and mono-methyl cis-5-norbornene-endo-2,3-dicarboxylic acid in the presence of a conventional polymerization initiator, as below illustrated in Reaction Scheme IV.
The aforementioned copolymer resins (Formulas IV to VII) can be prepared according to the present invention by a conventional polymerization process such as bulk polymerization or solution polymerization. Preferred polymerization initiators used in the present invention include benzoyl peroxide, 2,2′-azobisisobutyronitrile(AIBN), acetylperoxide, laurylperoxide, tert-butylperacetate, di-t-butyl peroxide, or the like. As a solvent, cyclohexanone, methyl ethyl ketone, benzene, toluene, dioxane, and/or dimethylformamide may be used individually, or in a mixture.
In the process for preparing the copolymer resin according to the present invention, general polymerization conditions, including temperature and pressure of radical polymerization, may vary depending upon the properties of the reactants, but it is preferable to carry out the polymerization reaction at a temperature between 60° C. and 200° C. under nitrogen or argon atmosphere for 4 to 24 hours.
The copolymer resin photoresist composition according to the present invention can be prepared using a conventional process for forming a photoresist composition; that is, by mixing the resin with a conventional photoacid generator in the presence of an organic solvent to form a photoresist solution. This pho

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