Ether, polymer, resist composition and patterning process

Details Ether, polymer, resist composition and patterning process Ether, polymer, resist composition and patterning process

2002-01-16

2003-09-23

Pezzuto, Helen L. (Department: 1713)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S579000, C568S667000, C526S258000, C526S266000, C526S271000, C526S282000, C526S319000, C526S332000

Reexamination Certificate

active

06624335

ABSTRACT:

This invention relates to (i) an ether compound, (ii) a polymer comprising specific recurring units, (iii) a resist composition comprising the polymer as a base resin, and (iv) 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) an ether compound capable of forming a polymer having improved substrate adhesion, (ii) a polymer having improved reactivity, robustness and substrate adhesion, (iii) a resist composition comprising the polymer as a base resin, which has a higher resolution and etching resistance than conventional resist compositions, and (iv) a patterning process using the resist composition.
It has been found that novel ether compounds of formula (1) below which are produced by the method to be described later can form polymers having improved substrate adhesion, and that novel polymers obtained therefrom and having a weight average molecular weight of 1,000 to 500,000 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 an ether compound of the following general formula (1).
Herein R
1
is hydrogen or a straight, branched or cyclic alkyl group of 1 to 6 carbon atoms, R
2
is a straight, branched or cyclic alkyl group of 1 to 6 carbon atoms, R
3
is hydrogen or an acyl or alkoxycarbonyl group of 1 to 15 carbon atoms in which some or all of the hydrogen atoms on the constituent carbon atoms may be substituted with halogen atoms, k is 0 or 1, m is an integer from 0 to 3, and n is an integer from 3 to 6.
In a second aspect, the invention provides a polymer comprising recurring units of the following general formula (1-1) or (1-2) derived from the ether compound of the above formula (1) and having a weight average molecular weight of 1,000 to 500,000.
Herein k, m, n, and R
1
to R
3
are as defined above.
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
4
is hydrogen, methyl or CH
2
CO
2
R
6
; R
5
is hydrogen, methyl or CO
2
R
6
; R
6
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
7
is an acid labile group; R
8
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 alkoxycarbonyloxy or alkoxyalkoxy 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 Z, k, p and R
4
to R
8
are as defined above, and Y is an oxygen atom or NR
9
wherein R
9
is a straight, branched or cyclic alkyl group of 1 to 6 carbon atoms.
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 Y, Z, k, p and R
4
to R
9
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 Z, k, p and R
4
to R
8
are as defined above.
In a third aspect, the invention provides a resist composition comprising the polymer defined above.
In a fourth aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition 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 ether compounds of formula (1) are highly polar due to the inclusion of a hydroxyl, acyloxy or alkoxycarbonyloxy group as well as an ether structure. The polymers comprising recurring units of formula (1-1) or (1-2) derived from the ether compounds thus exhibit improved substrate adhesion. The polymers also have high rigidity since bridged aliphatic rings are incorporated in the backbone. A carbon chain of an appropriate length introduced between the ether structure and the rigid backbone serves to properly alleviate the rigidity which has been excessive in the prior art. Since the ether 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 carbon chain 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
Ether
The ether compound of the invention has the following general formula (1).
Herein R
1
is hydrogen or a straight, branched or cyclic alkyl group of 1 to 6 carbon atoms. Exemplary alkyl groups include methyl, ethyl, n-propyl

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