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
2001-09-08
2004-06-15
Ashton, Rosemary (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, C430S906000, C430S907000
Reexamination Certificate
active
06749986
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention includes new polymers and use of such polymers as a resin component for photoresist compositions, particularly chemically-amplified positive-acting photoresist compositions. Polymers and resists of the invention are particularly useful for imaging with short wavelength radiation, such as sub-200 nm and preferably about 157 nm. Polymers of the invention contain photoacid-labile groups that are substituted by one or more electron-withdrawing groups, and more particularly, where groups alpha to an acidic site are substituted by one or more electron-withdrawing groups.
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. 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.
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 193 nm. 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 m) features that respond to constant industry demands for smaller dimension circuit patterns, e.g. to provide greater circuit density and enhanced device performance.
Recently, use of an F
2
excimer laser imaging source which provides radiation having a wavelength of about 157 nm, has been considered as a route to manufacture of even smaller features. See, generally, Kunz et al., SPIE Proceedings (Advances in Resist Technology), vol. 3678, pages 13-23 (1999).
SUMMARY OF THE INVENTION
The invention provides new resins that comprise one or more groups alpha to an acidic site (e.g. an alcohol, an amine or a hydroxyl amine) that are substituted by one or more electron-withdrawing groups. References herein that electronegative groups are “alpha” to an acidic site means that the electronegative groups are substituents of atoms (typically carbon) that are immediately adjacent to and covalently bonded to an acidic group such as alcohol (>COH), amine (e.g. >NH), or hydroxylamine (e.g. >NOH).
Resins of the invention preferably also comprise a substituted photoacid-labile deblocking group such as an ether, acetal, ketal, formal (H
2
CO—), triethers, tetrathers, esters and other deblocking group. Those deblocking groups may comprise and linked the acidic site (e.g. alcohol, amine hydroxylamine), i.e. the acidic site will be present in a protected or in “latent acid form” as part of the deblocking group, where the deblocking group is cleaved in the presence of photoacid to provide the acidic group. For example, an alcohol or hydroxyl amine can be reacted with a vinyl ether such as ethyl vinyl ether to provide an acetal group, which will undergo a cleavage reaction in the presence of photogenerated acid.
Preferably, the acidic-group containing substituent is linked by multiple single bonds or “tethers” to the polymer backbone, e.g. 2 or 3 separate single bond linkages. Such multiple bond linkages can increase plasma stability as a plurality of bonds must be broken before a volatile fragment is released.
Specifically preferred acidic groups of polymers of the invention include those of the following Formulae (I), (IA) and (IB):
wherein in Formula (I), R, R′ and R″ are each independently hydrogen, a functional group for attachment to a polymer, e.g. carboxy, alcohol, alkyl e.g. C
1-6
alkyl, a chemical bond, and the like; or other non-hydrogen substituent such as an electron-withdrawing group such as those groups identified below for X and Y, an alkyl group such as C
1-6
alkyl, alkoxy such as C
1-6
alkoxy, and the like, with at least one of R, R′ and R″ being a functional group for attachment to a polymer, and preferably two or each of R, R′ and R″ are functional groups for attachment to a polymer;
at least one of X and Y, and preferably both of X and Y, are electron-withdrawing groups such as halogen (preferably fluorine, cyano, haloalkyl such as haloC
1-12
alkyl particularly fluoroalkyl such as —CF
3
and other C
1-8
perfluoroalkyl, and the like; and at least one of X′ and Y′, and preferably both of X′ and Y′, are electron-withdrawing groups such as halogen preferably fluoro, cyano, haloalkyl and the like. If one of X, Y, X′ and/or Y′ are not an electron-withdrawing group, then suitably they may be hydrogen, alkyl such as C
1-6
alkyl, alkoxy preferably C
1-6
alkoxy, and the like. Preferably at least one or both of X and Y is fluoro, and preferably at least one or both of X′ and Y′ is fluorine.
and wherein in Formula (IA) above each R is independently selected from the same group as defined for R, R′ and R″ in Formula (I) above;
and X, Y, X′, and Y′ are the same as defined for the same substituents in Formula (I) above. In Formula (IA) above, preferably at least one or both of X and Y is fluorine, and preferably at least one or both of X′ and Y′ is fluorine.
and wherein in Formula (IB) above each R is independently selected from the same group as defined for R, R′ and R″ in Formula (I) above;
and X, Y, X′, and Y′ are the same as defined for the same substituents in Formula (I) above. In Formula (IB) above, preferably at least one or both of X and Y is fluorine, and preferably at least one or both of X′ and Y′ is fluorine.
Polymers of the invention may contain a variety of groups. For example, polymers of the invention suitably may contain polymerized cyclic olefin units such as optionally substituted norbornene units; acrylate groups (which includes methacrylate groups herein) such as methyl methacrylate, ethyl methacrylate and other alkyl acrylates, and the like; cyano groups such as provided by polymerization with acrylonitrile or methacrylonitrile; and the like.
Polymers of the invention also may contain a variety of aromatic groups, preferably substituted with one or more electron-withdrawing groups to reduce undesired absorbance of the short wavelength radiation such as 157 nm by the aromatic group. More particularly suitable are polymers that contain phenyl repeat units, which units have one or more electron-withdrawing ring substituents such as halogen particula
Szmanda Charles R.
Taylor Gary N.
Ashton Rosemary
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Shipley Company L.L.C.
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