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
2002-02-13
2004-12-28
Kelly, Cynthia H. (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
C430S905000, C430S909000, C430S910000, C430S325000, C430S326000, C430S327000, C430S328000, C430S330000, C430S331000, C430S296000, C526S329600, C526S328000, C526S328500, C526S280000, C526S281000, C526S332000, C526S333000, C526S266000, C526S268000
Reexamination Certificate
active
06835525
ABSTRACT:
This invention relates to (i) a polymer having a specific structure, (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 transparency 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 (meth)acrylic polymers. Since the backbone of the resin is too robust, substrate adhesion is poor. These compositions are thus impractical as well.
Both the (meth)acrylic and alicyclic backbone systems commonly have the problem of pattern disruption due to swelling of resist film. Resist compositions based on these systems have been designed so as to improve their resolution performance by increasing the difference in dissolution rate before and after exposure, and as a consequence, they eventually become highly hydrophobic. Highly hydrophobic resist compositions, when applied as a film and processed with a developer, can maintain the film tenaciously in unexposed regions and allow the film to be instantaneously dissolved in over-exposed regions, while relatively broad exposed regions therebetween allow penetration of the developer, but are kept undissolved, that is, swollen. At the very small pattern size for which ArF excimer laser is actually used, those resist compositions which allow adjacent pattern strips to be joined together and disrupted on account of swelling are rejected. While a finer pattern rule is being demanded, there is a need to have a resist material which is not only satisfactory in sensitivity, resolution, and etching resistance, but fully restrained from swelling.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide (i) a polymer having improved reactivity, robustness and substrate adhesion as well as minimized swell during development, (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) 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 as well as an appropriately high solubility and minimized swell in a developer; 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) and having a weight average molecular weight of 1,000 to 500,000:
Herein R
1
and R
2
each are hydrogen or methyl; R
3
and R
4
each are hydrogen or a straight, branched or cyclic, monovalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom, and R
3
and R
4
may bond together to form a ring, wherein R
3
and R
4
together represent a straight, branched or cyclic, divalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom; each of R
5
to R
8
is hydrogen, a hydroxyl group or a straight, branched or cyclic, monovalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom, at least one of R
5
to R
8
contains a hetero atom, any two of R
5
to R
8
may bond together to form a ring, wherein the ring-forming two R's together represent a straight, branched or cyclic, divalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom; R
9
and R
10
each are hydrogen or methyl; each of R
11
to R
14
is hydrogen or a straight, branched or cyclic, monovalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom, a pair of R
11
and R
12
, a pair of R
11
or R
12
and R
13
, a pair of R
11
and R
14
, or a pair of R
13
and R
14
may bond together to form a ring, wherein each pair represents a straight, branched or cyclic, divalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom; R
15
is hydrogen, methyl or CH
2
CO
2
R
17
; R
15
′ is hydrogen, methyl or CH
2
CO
2
R
17
′; R
15
″ is hydrogen, methyl or CH
2
CO
2
R
17
″; R
15
″′ is hydrogen, methyl or CH
2
CO
2
R
17
″′; R
16
is hydrogen, methyl or CO
2
R
17
; R
16
′ is hydrogen, methyl or CO
2
R
17
′; R
16
″ is hydrogen, methyl or CO
2
R
17
″; R
16
″′ is hydrogen, methyl or CO
2
R
17
″′; R
17
, R
17
′, R
17
″ and R
17
″′ may be identical or different between R
15
and R
16
, between R
15
′ and R
16
′, between R
15
″ and R
16
″, and between R
15
″′ and R
16
″′, respectively, and each is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
18
is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbon atoms containing a carboxyl or hydroxyl group; R
19
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing at least one partial structure selected from the group consisting of ether, aldehyde, ketone, ester, carbonate, acid anhydride, amide and imide; R
20
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing a polycyclic hydrocarbon group; R
21
is an acid labile group; k is 0 or 1; x1, x2, x3, a, b, c and d represent a molar compositional ratio of the recurring units associated therewith, satisfying x1+x2+x3+a+b+c+d=1, x1, x2, x3, a, b and c are numbers inclusive of 0, d is a number of more than 0, all of x1, x2 and x3 are not equal to 0 at the same time. Preferably, the acid labile group represented by R
21
in formula (1) is a tertiary alkyl group having a cyclic structure.
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 polymer comprising recurring units of formula (1) is a polymer based on a (meth)acrylic acid derivati
Funatsu Kenji
Nakashima Mutsuo
Nishi Tsunehiro
Tachibana Seiichiro
Kelly Cynthia H.
Lee Sin J.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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