Polymers, resist compositions and patterning process

Details Polymers, resist compositions and patterning process Polymers, resist compositions and patterning process

2001-06-01

2003-09-23

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

C430S296000, C430S313000, C430S323000, C430S326000, C430S327000, C430S328000, C430S330000, C430S905000, C430S907000, C528S033000, C528S036000

Reexamination Certificate

active

06623909

ABSTRACT:

This invention relates to polymers useful as the base polymer in resist compositions suited for microfabrication, especially chemical amplification resist compositions. It also relates to resist compositions comprising the polymers, and a patterning process using the same.
BACKGROUND OF THE INVENTION
In the drive for higher integration and operating speeds in LSI devices, the pattern rule is made drastically finer. The rapid advance toward finer pattern rules is grounded on the development of a projection lens with an increased NA, a resist material with improved performance, and exposure light of a shorter wavelength. In particular, the change-over from i-line (365 nm) to shorter wavelength KrF excimer laser (248 nm) brought about a significant innovation, enabling mass-scale production of 0.18 micron rule devices. To the demand for a resist material with a higher resolution and sensitivity, acid-catalyzed chemical amplification positive working resist materials are effective as disclosed in U.S. Pat. No. 4,491,628 and U.S. Pat. No. 5,310,619 (JP-B 2-27660 and JP-A 63-27829). They now become predominant resist materials especially adapted for deep UV lithography.
Resist materials adapted for KrF excimer lasers enjoyed early use on the 0.3 micron process, went through the 0.25 micron rule, and currently entered the mass production phase on the 0.18 micron rule. Engineers have started investigation on the 0.15 micron rule, with the trend toward a finer pattern rule being accelerated. A wavelength change-over from KrF to shorter wavelength ArF excimer laser (193 nm) is expected to enable miniaturization of the design rule to 0.13 &mgr;m or less. Since conventionally used novolac resins and polyvinylphenol resins have very strong absorption in proximity to 193 nm, they cannot be used as the base resin for resists. To ensure transparency and dry etching resistance, some engineers investigated acrylic and alicyclic (typically cycloolefin) resins as disclosed in JP-A 9-73173, JP-A 10-10739, JP-A 9-230595 and WO 97/33198.
With respect to F
2
excimer laser (157 nm) which is expected to enable further miniaturization to 0.10 &mgr;m or less, more difficulty arises in insuring transparency because it was found that acrylic resins are not transmissive to light at all and those cycloolefin resins having carbonyl bonds have very low light transmittance. It is known from Critical issues in 157 nm lithography: T. M. Bloomstein et al., J. Vac. Sci. Technol. B 16(6), November/December 1998, that siloxane polymers and silsesquioxane polymers are more advantageous for light transmission improvement. These polymers have a possibility to use as the resist base resin from which a multilayer resist pattern is formed using an oxygen plasma. If they have a high dry etching selectivity, it is believed that this, combined with a possibility of slimming as compared with conventional resists, considerably mitigates the burden associated with light transmission.
However, those polymers having phenol groups introduced for enhancing the dissolution contrast to alkali have a window for light absorption in proximity to a wavelength of 160 nm, so the absorption is somewhat improved, but far below the practical level. Those polymers having carboxylic acid introduced are further reduced in light transmittance because of light absorption based on carbonyl groups. It was found in conjunction with single layer resists that reducing carbon-to-carbon unsaturated bonds as typified by benzene rings and carbon-to-oxygen double bonds as typified by carbonyl groups is essential for insuring a light transmittance (see International Work Shop 157 nm Lithography MIT-LL, Boston, Mass., May 5, 1999). Because of an ability to form a thin film, silicone-containing polymers are advantageous in light transmittance over single layer resists, but yet required to essentially increase light transmittance in order to increase the resolution.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel polymer having a high transmittance to an excimer laser beam in the vacuum ultraviolet region corresponding to a wavelength of up to 300 nm, especially an F
2
excimer laser (157 nm), Kr
2
excimer laser (146 nm), KrAr excimer laser (134 nm) and Ar
2
excimer laser (121 nm), and EUV (8-13 nm), and useful as the base polymer in a resist composition, especially chemical amplification resist composition. Another object is to provide a resist composition, especially chemical amplification resist composition comprising the polymer, and a patterning process using the same.
Based on the belief that a fluorinated alcohol is compliant with both light transmittance and etching resistance, the inventor attempted to introduce a fluorinated alcohol into a silicone-containing polymer. The inventor has found that a resist composition having light transmittance and etching resistance is obtained using a resin based on a polysilsesquioxane containing a fluorinated alcohol partially substituted with acid labile groups.
In a first aspect, the invention provides a polymer comprising recurring units of the following general formula (1).
wherein R
1
is a straight, branched or cyclic divalent hydrocarbon group of 1 to 20 carbon atoms or a bridged cyclic hydrocarbon group, R is hydrogen atom or an acid labile group, and letters m and n are in the range: 0≦m≦3, 0≦n≦3 and 1≦m+n≦6.
In a second aspect, the invention also provides a polymer comprising recurring units of the following general formula (2).
wherein R
1
is a straight, branched, cyclic or bridged cyclic divalent hydrocarbon group of 1 to 20 carbon atoms, R
2
is an acid labile group, R
3
is a straight, branched or cyclic, substituted or unsubstituted, monovalent hydrocarbon group of 1 to 20 carbon atoms, and letters m, n, p, q, r, s, t, and u are in the range: 0≦m≦3, 0≦n≦3, 0<p<1, 0<q<1, 0≦r<1, 0≦s<1, 0≦t<1, 0≦u<1, 1≦m+n≦6, and p+q+r+s+t+u=1.
In a third aspect, the invention provides a resist composition comprising the polymer of formula (1) or (2).
In a fourth aspect, the invention provides a chemical amplification, positive resist composition comprising (A) the polymer of formula (1) or (2), (B) an organic solvent, and (C) a photoacid generator. The resist composition may further include (D) a basic compound and/or (E) a dissolution inhibitor.
In a fifth aspect, the invention provides a process for forming a pattern, comprising the steps of applying the resist composition defined above onto a substrate to form a coating; heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photo-mask; optionally heat treating the exposed coating, and developing the coating with a developer.
Also provided is a process for forming a multilayer resist pattern, comprising the steps of forming a pattern according to the above process, and etching the pattern with an oxygen plasma to be ready for further processing.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Polymer
According to the invention, the polymers or high molecular weight compounds are defined as comprising recurring units of the following general formula (1) or (2).
wherein R
1
is a straight, branched, cyclic or bridged cyclic divalent hydrocarbon group of 1 to 20 carbon atoms, R is hydrogen atom or an acid labile group, R
2
is an acid labile group, R
3
is a straight, branched or cyclic, substituted or unsubstituted, monovalent hydrocarbon group of 1 to 20 carbon atoms, and letters m, n, p, q, r, s, t, and u are in the range: 0≦m≦3, 0≦n≦3, 0<p<1, 0<q<1, 0≦r<1, 0≦s<1, 0≦t<1, 0<u<1, 1≦m+n≦6, and p+q+r+s+t+u=1.
Herein R
1
is a straight, branched, cyclic or bridged cyclic divalent hydrocarbon group of 1 to 20 carbon atoms, preferably 2 to 16 carbon atoms, typically alkylene group. Illustrative examples of R
1
include methylene, ethylene, propylene, butylene, cyclope

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