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
2000-02-22
2002-04-30
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
C430S326000, C430S910000, C430S914000
Reexamination Certificate
active
06379861
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new polymers and use of such polymers as a resin binder component for photoresist compositions, particularly chemically-amplified positive-acting resists that can be effectively imaged at short wavelengths such as 248 nm and 193 nm.
2. Background
Photoresists are photosensitive films used for transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable reagents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For a positive-acting photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less developer soluble.
In general, photoresist compositions comprise at least a resin binder component and a photoactive agent. Photoresist compositions are described in Deforest,
Photoresist Materials and Processes,
McGraw Hill Book Company, New York, ch. 2, 1975 and by Moreau,
Semiconductor Lithography, Principles, Practices and Materials,
Plenum Press, New York, ch. 2 and 4, both incorporated herein by reference for their teaching of photoresist compositions and methods of making and using the same.
More recently, chemically-amplified-type resists have been increasingly employed, particularly for formation of sub-micron images and other high performance applications. Such photoresists may be negative-acting or positive-acting and generally include many crosslinking events (in the case of a negative-acting resist) or deprotection reactions (in the case of a positive-acting resist) per unit of photogenerated acid. In the case of positive chemically-amplified resists, certain cationic photoinitiators have been used to induce cleavage of certain “blocking” groups pendant from a photoresist binder, or cleavage of certain groups that comprise a photoresist binder backbone. See, for example, U.S. Pat. Nos. 5,075,199; 4,968,581; 4,883,740; 4,810,613; and 4,491,628, and Canadian Patent Application 2,001,384. Upon cleavage of the blocking group through exposure of a coating layer of such a resist, a polar functional group is formed, e.g., carboxyl or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer. See also R. D. Allen et al.,
Proceedings of SPIE,
2724:334-343 (1996); and P. Trefonas et al.
Proceedings of the
11
th
International Conference on Photopolymers
(
Soc. Of Plastics Engineers
), pp 44-58 (Oct. 6, 1997).
While currently available photoresists are suitable for many applications, current resists also can exhibit significant shortcomings, particularly in high performance applications such as formation of highly resolved sub-half micron and sub-quarter micron features.
Consequently, interest has increased in photoresists that can be photoimaged with short wavelength radiation, including exposure radiation of about 250 nm or less, or even about 200 nm or less, such as wavelengths of about 248 nm (provided by KrF laser) or 193 nm (provided by an ArF exposure tool). Use of such short exposure wavelengths can enable formation of smaller features. Accordingly, a photoresist that yields well-resolved images upon 248 nm or 193 nm exposure could enable formation of extremely small (e.g. sub-0.25 &mgr;m) features that respond to constant industry demands for smaller dimension circuit patterns, e.g. to provide greater circuit density and enhanced device performance.
However, many current photoresists are generally designed for imaging at relatively higher wavelengths, such as I-line (365 nm) and G-line (436 nm) exposures and are generally unsuitable for imaging at short wavelengths such as 193 nm and 248 nm. In particular, prior resists exhibit poor resolution (if any image at all can be developed) upon exposure to these shorter wavelengths. Among other things, current photoresists can be highly opaque to extremely short exposure wavelengths such as 248 nm and 193 nm, thereby resulting in poorly resolved images. Efforts to enhance transparency for short wavelength exposure can negatively impact other important performance properties such as substrate adhesion, which in turn can dramatically compromise image resolution.
It thus would be desirable to have new photoresist compositions, particularly resist compositions that can be imaged at short wavelengths such as 248 nm and 193 nm. It would be particularly desirable to have such resist compositions that can provide high resolution relief images, particularly small features such as sub-0.25 &mgr;m images.
SUMMARY OF THE INVENTION
The present invention provides novel polymers and photoresist compositions that comprise the polymers as a resin binder component.
The photoresist compositions of the invention can provide highly resolved relief images upon exposure to extremely short wavelengths, particularly 248 nm and 193 nm. The photoresists of the invention preferably are chemically-amplified positive resists, which utilize photoacid-induced cleavage of pendant alkyl ester polymer groups to provide solubility differentials between exposed and unexposed areas of a resist coating layer.
In general, polymers of the invention comprise one or more ester repeat units where the ester group comprises an optionally substituted alkyl moiety having about 5 or more carbon atoms, with at least two branched carbon atoms, i.e. at least two secondary, tertiary or quaternary carbon atoms. The alkyl moiety can be a noncyclic or single ring alicyclic group. Suitable alkyl moieties include those that have one, two or more tertiary carbon atoms, and/or one, two or more quaternary carbons. References herein to a “secondary” carbon indicate the carbon atom has two non-hydrogen substituents (i.e. CH
2
RR
1
where R and R
1
are the same or different and each is other than hydrogen); references herein to a “tertiary” carbon indicate the carbon atom has three non-hydrogen substituents (i.e. CHRR
1
R
2
where R, R
1
and R
2
are the same or different and each is other than hydrogen); and references herein to a “quaternary” carbon indicate the carbon atom has four non-hydrogen substituents (i.e. CRR
1
R
2
R
3
where R, R
1
, R
2
and R
3
are each the same or different and each is other than hydrogen). See, for instance, Morrison and Boyd,
Organic Chemistry,
particularly at page 85 (3
rd
ed., Allyn and Bacon), for a discussion of those terms secondary, tertiary and quaternary. It also should be understood that references herein to “alkyl” are inclusive of linked or branched carbon chains such as alkylidene, alkylene and the like. Additionally, for purposes of the present disclosure, the keto carbon (i.e. C═O) of the ester linkage is referred to herein as the “carbonyl oxygen”, and the linked oxygen (i.e. C═O(O)) is referred to herein as the “carboxyl oxygen”, such as indicated by the following illustrative structure where the above terms are exemplified:
It is often preferred that a quaternary carbon is directly linked (i.e. covalently linked with no other interposed atoms) to the ester carboxyl oxygen, as is depicted in the above structure.
It has been found that chemically-amplified positive photoresists comprising a po
Barclay George G.
Taylor Gary N.
Trefonas, III Peter
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Shipley Company L.L.C.
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