Polymer, resist composition and patterning process

Details Polymer, resist composition and patterning process Polymer, resist composition and patterning process

2001-09-14

2004-01-06

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

C430S322000, C430S330000, C549S295000, C549S326000, C560S116000, C560S126000, C526S270000, C526S272000

Reexamination Certificate

active

06673515

ABSTRACT:

This invention relates to (i) a polymer comprising specific recurring units, (ii) a resist composition comprising the polymer as a base resin, and (iii) a patterning process 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.
For resist materials for use with a KrF excimer lasers, polyhydroxystyrene having a practical level of transmittance and etching resistance is, in fact, a standard base resin. For resist materials for use with ArF excimer lasers, polyacrylic or polymethacrylic acid derivatives and polymers containing aliphatic cyclic compounds in the backbone are under investigation. All these polymers have advantages and disadvantages, and none of them have been established as the standard base resin.
More particularly, resist compositions using derivatives of polyacrylic or polymethacrylic acid have the advantages of high reactivity of acid-decomposable groups and good substrate adhesion and give relatively satisfactory results with respect to sensitivity and resolution, but have extremely low etching resistance and are impractical because the resin backbone is weak. On the other hand, resist compositions using polymers containing alicyclic compounds in their backbone have a practically acceptable level of etching resistance because the resin backbone is robust, but are very low in sensitivity and resolution because the reactivity of acid-decomposable protective groups is extremely low as compared with those on the acrylic polymers. Since the backbone of the resin is too robust, substrate adhesion is poor. These compositions are thus impractical as well. While a finer pattern rule is being demanded, there is a need to have a resist material which is satisfactory in sensitivity, resolution, and etching resistance.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide (i) a polymer having improved reactivity, robustness and substrate adhesion, (ii) a resist composition comprising the polymer as a base resin, which has a higher resolution and etching resistance than conventional resist compositions, and (iii) a patterning process using the resist composition.
It has been found that novel polymers comprising recurring units of the following general formula (1—1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000, which are produced by the method to be described later, have improved reactivity, robustness or rigidity and substrate adhesion; that a resist composition comprising the polymer as the base resin has a high resolution and etching resistance; and that this resist composition lends itself to precise micropatterning.
In a first aspect, the invention provides a polymer comprising recurring units of the following general formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000.
Herein k is 0 or 1, m is 0, 1, 2, 3 or 4, and n is 1 or 2.
In one preferred embodiment, the polymer contains, in addition to the recurring units of formula (1-1), recurring units of the following general formula (2-1).
Herein k is as defined above; R
1
is hydrogen, methyl or CH
2
CO
2
R
3
; R
2
is hydrogen, methyl or CO
2
R
3
; R
3
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
4
is an acid labile group; R
5
is selected from the class consisting of a halogen atom, a hydroxyl group, a straight, branched or cyclic alkoxy, acyloxy or alkylsulfonyloxy group of 1 to 15 carbon atoms, and a straight, branched or cyclic alkoxyalkoxy or alkoxycarbonyloxy group of 2 to 15 carbon atoms, in which some or all of the hydrogen atoms on constituent carbon atoms may be substituted with halogen atoms; Z is a single bond or a straight, branched or cyclic (p+2)-valent hydrocarbon group of 1 to 5 carbon atoms, in which at least one methylene may be substituted with oxygen to form a chain-like or cyclic ether or two hydrogen atoms on a common carbon may be substituted with oxygen to form a ketone; and p is 0, 1 or 2.
In another preferred embodiment, the polymer contains, in addition to the recurring units of formula (1-1), recurring units of the following general formulae (2-1) and (3).
Herein k, p and R
1
to R
5
are as defined above.
In a further preferred embodiment, the polymer contains, in addition to the recurring units of formula (1-1), recurring units of the following general formula (4) alone or in combination with recurring units of the following general formula (2-1), and recurring units of the following general formula (3).
Herein k, p and R
1
to R
5
are as defined above.
In a still further preferred embodiment, the polymer contains, in addition to the recurring units of formula (1-2), recurring units of the following general formula (2-2).
Herein k, p and R
1
to R
5
are as defined above.
In a second aspect, the invention provides a resist composition comprising the polymer defined above.
In a third aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition defined above onto a substrate to form a coating; heat treating the coating and then exposing it to high-energy radiation or electron beams through a photo mask; and optionally heat treating the exposed coating and developing it with a developer.
The polymers comprising recurring units of formula (1-1) or (1-2) have high rigidity since bridged aliphatic rings are incorporated in the backbone. They show improved substrate adhesion since they have a five or six-membered ring lactone structure with a high polarity. A spacer of appropriate length introduced between the lactone structure and the rigid backbone serves to properly alleviate the rigidity which has been excessive in the prior art. Since the lactone structure moiety is spaced apart from the backbone, it can act more positively as a polar group. These factors cooperate to develop a substrate adhesion force surpassing the prior art compositions. Although low reactivity is left outstanding in the prior art, the spacer introduced allows the acid generated to diffuse, thereby improving reactivity and as an accompanying benefit, achieving a reduction of line edge roughness. Therefore, a resist composition using the polymer as a base resin satisfies all the performance factors of sensitivity, resolution and etch resistance and is very useful in forming micropatterns.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Polymers or high molecular weight compounds comprising recurring units of the following general formula (1-1) or (1-2) according to the invention are novel. The polymers have a weight average molecular weight of 1,000 to 500,000.
Herein k is 0 or 1, m is 0, 1, 2, 3 or 4, and n is 1 or 2.
More specifically, the polymers of the invention are divided into the following four subgenuses of polymers.
Subgenus (I) include polymers comprising, in addition to the recurring units of formula (1-1), recurring units of the following general formula (2-1).
Herein k is as defined above; R
1
is hydrogen, methyl or CH
2
CO
2
R
3
; R
2
is hydrogen, methyl or CO
2
R
3
; R
3
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
4
is an acid labile group; R
5
is selected from the class consisting of a halogen atom, a hydroxyl group, a straight, branched or cyclic alkoxy, acyloxy or alkylsulfonyloxy group of 1 to 15 carbon atoms, and a straight, branched or cyclic alkoxyalkoxy or alkoxycarbonyloxy group of 2 to 15 carbon atoms, in which some or all of the hydrogen atoms on constituent carbon atoms may be substituted with halogen atoms; Z is a single bond or a straight, branched or cyclic (p+2)-valent

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