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
2002-12-20
2004-07-27
Huff, Mark F. (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, C430S914000, C430S326000, C430S909000, C430S910000, C430S271100, C430S272100, C430S925000
Reexamination Certificate
active
06767688
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new photoresist compositions that contain a halogenated salt. Preferred resists of the invention contain an ammonium or alkyl ammonium salt that has a halogenated anion component such as a halogenated alkyl sulfonate or carboxylate anion component.
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.
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.
It thus would be desirable to have new photoresist compositions, particularly resist compositions that can be imaged at short wavelengths such as 248 nm or 193 nm. It would be particularly desirable to have such resist compositions that can provide high resolution relief images.
SUMMARY OF THE INVENTION
The present invention provides new photoresist compositions that contain a halogenated organic salt, particularly a compound having a halogenated anion component and an ammonium (amine) or alkyl ammonium cation component.
More particularly, resists of the invention in general comprise a resin, a photoactive component such as one or more photoacid generator compounds, and a halogenated organic salt. The organic salt is typically basic (alkaline), particularly a pKa of about 4 or higher (larger number), more preferably a pKa of 5, 6, 7, 8, or 9 or higher.
Preferred halogenated organic salt additive compounds of resists of the invention are relatively small molecules, more particularly having a molecular weight of less than about 1000, 800 or 700 daltons, more preferably a molecular weight of less than about 600, 500, 400, 300 or 200 daltons. Preferred halogenated organic salt additive compounds of resists of the invention typically will have a molecular weight of at least about 40 or 50, more typically at least about 60, 70, 80, 90 or 100. Preferred halogenated organic salt additive compounds are non-polymeric.
Particularly preferred haloganted organic salts are ammonium and alkyl amine salts, e.g. compounds of the formula NH
4
. M and (C
1-12
alkyl)
m
(H)
n
N. M where M is an organic counter that is halogenated, preferably fluorinated and may be preferably perfluorinated, m is 1 to 4, n is 0 to 3, and the sum of m and n is 4.
Preferred organic counter ions (such as M of the above formulae) are alkylsulfonates, particularly halogenated alkylsulfonates such as those of the formula C
1-24
alkylSO
2
O— or C
1-16
alkylSO
2
O——where the alkyl group has one or more halogen substituents, preferably one or more fluoro substituents, and the alkyl group may be preferably a perfluoroalkyl substituent. Suitable organic counter ions M also include halogenated alkyl carboxylates such as those of the formula C
1-24
alkylCOO— or C
1-16
alkylCOO— where the alkyl group has one or more halogen substituents, preferably one or more fluoro substituents, and the alkyl group may be preferably a perfluoroalkyl substituent.
We have surprisingly found that addition of such a halogenated organic salt (e.g. a halogenated alkylsulfonate or alkylcarboxylate amine salt) to a photoresist can significantly increase lithographic performance of the photoresist, including with respect to photospeed, reduced line edge roughness, reduced footing, reduced post-exposure bake sensitivity, and/or increased depth of focus. See, for instance, the data set forth in the examples which follow.
The photoresists of the invention preferably are chemically-amplified positive resists, which utilize photoacid-induced cleavage of pendant polymer groups of the resin binder to provide solubility differentials between exposed and unexposed areas of a resist coating layer. Preferred deblocking polymers for use as a resin binder component of resists of the invention include acrylate resins that have pendant ester groups that can react to provide polar acid groups in the presence of photogenerated acid.
For imaging at wavelengths greater than 200 nm, a resist suitably contains a resin that comprises aromatic groups, such as phenyl groups, particularly phenolic groups. Alkylacrylate/phenolic copolymers are particularly preferred, such as polymers that comprise repeat units of polymerized vinyl phenol and an alkyl acrylate such as t-butylacrylate or t-butylmethacrylate.
For imaging at 193 nm, resists of the invention suitably comprise a resin component that is substantially free of any phenyl or other aromatic groups. For example, preferred polymers contain less than about 5 or 1 mole percent aromatic groups, more preferably less than about 0.1, 0.02, 0.04 or 0.08 mole percent aromatic groups, and still more preferably less than about 0.01 mole percent aromatic groups. Particularly preferred polymers are completely free of aromatic groups. Aromatic groups can be highly absorbing of sub-200 nm radiation and thus are undesirable for polymers used in photoresists of the invention for short wavelength imaging applications.
In addition to a resin,
Cameron James F.
Teng Gary Ganghui
Thackeray James W.
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Huff Mark F.
Lee Sin J.
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