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
2000-08-25
2003-12-16
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
C430S325000, C430S326000, C430S914000, C430S921000, C430S922000
Reexamination Certificate
active
06664022
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new photoacid generator compounds (“PAGs”) and photoresist compositions that comprise such compounds. In particular, the invention relates to photoacid generator iodonium and sulfonium compounds having a cation component that comprises one or more substituents of naphthyl, thienyl or pentafluorophenyl. PAGs of the invention are preferably employed in resists imaged at short wavelengths, such as sub-300 nm and sub-200 nm, e.g. 248 nm, 193 nm and 157 nm, and ionzing radiation such as EUV, IPL, E-beam snd X-ray.
2. Background
Photoresists are photosensitive films for transfer of images to a substrate. They form negative or positive images. After coating a photoresist on a substrate, the coating is exposed through a patterned photomask to a source of activating energy such as ultraviolet light to form a latent image in the photoresist coating. The photomask has areas opaque and transparent to activating radiation that define an image desired to be transferred to the underlying substrate. A relief image is provided by development of the latent image pattern in the resist coating. The use of photoresists is generally described, for example, by Deforest, Photoresist Materials and Processes, McGraw Hill Book Company, New York (1975), and by Moreau, Semiconductor Lithography, Principals, Practices and Materials, Plenum Press, New York (1988).
Known photoresists can provide features having resolution and size sufficient for many existing commercial applications. However for many other applications, the need exists for new photoresists that can provide highly resolved images of submicron dimension.
Various attempts have been made to alter the make-up of photoresist compositions to improve performance of functional properties. Among other things, a variety of photoactive compounds have been reported for use in photoresist compositions. See, e.g., U.S. Pat. No. 4,450,360 and European Application 615163.
More recently, certain “chemically amplified” photoresist compositions have been reported. Such photoresists may be negative-acting or positive-acting and rely on multiple 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 other words, the photogenerated acid acts catalytically. 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; 4,968,851; 4,883,740; 4,810,613; and 4,491,628, and Canadian Patent Application 2,001,384. Upon selective cleavage of the blocking group through exposure of a coating layer of such a resist, a polar functional group is provided, e.g., carboxyl, phenol or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer.
SUMMARY OF THE INVENTION
We have now discovered novel photoacid generator compounds (PAGs) for use in either positive-acting or negative-acting photoresist compositions.
We have found that excessive absorbance can remain an issue for resists imaged at short wavelengths such as 193 nm, even where the resist resin is optimized for low absorbance such as by having little or no aromatic content. In particular, we have found that a targeted absorption “budget” for a short wavelength resist may be substantially consumed by the resin component alone.
PAGs of the invention can exhibit good transparency to short wavelength radiation such as 193 nm. Accordingly, PAGs of the invention are particularly useful for photoresists imaged at short wavelengths such as 193 nm and 157 nm and can add minimal absorbance amounts to the formulated resist. PAGs of the invention are also useful for imaging at longer wavelengths such as 248 nm.
PAGs of the invention are sulfonium and iodonium compounds having a cation component that comprises one or more substituents of naphthyl, thienyl, or pentafluorophenyl, or a cation component that has a sulfur ring group such a thienyl, benzothiophenium, etc. Those substituents (chromophores) provide enhanced transparency of the PAG, while maintaining effective photoacid generation properties.
More particularly, in a first aspect of the invention, sulfonium and iodonium PAGs are provided that contain at least one naphthyl substituent, preferably multiple naphthyl substituents. Preferred naphthyl-substituted PAGs of the invention include sulfonium and iodonium compounds of the following Formulae I and II:
wherein in Formulae I and II: each R is the same or different non-hydrogen substituent such as hydroxy, cyano, nitro, halogen, optionally substituted alkyl including cycloalkyl; optionally substituted alkenyl; optionally substituted alkynyl; optionally substituted alkoxy; optionally substituted alkylthio; optionally substituted alkylsulfinyl; optionally substituted alkylsulfonyl; optionally substituted alkanoyl; optionally substituted carbocyclic aryl; or optionally substituted heteroalicyclic or heteroaromatic suitably having 1-3 rings with 3-8 ring members per ring and 1-3 N
2
O or S atoms;
each n is an integer equal to 0 (where the naphthyl group has no non-hydrogen substituents) to 7, more typically 0, 1, 2, 3 or 4; and
R
1
and R
2
are the same or different and each is suitably an aromatic or non-aromatic group such as e.g. optionally substituted alkyl including cycloalkyl; optionally substituted alkenyl; optionally substituted alkynyl; optionally substituted alkoxy; optionally substituted alkylthio; optionally substituted alkylsulfinyl; optionally substituted alkylsulfonyl; optionally substituted carbocyclic aryl; or optionally substituted heteroalicyclic or heteroaromatic suitably having 1-3 rings with 3-8 ring members per ring and 1-3 N, O or S atoms, with aromatic groups typically being preferred R
1
groups;
X is a counter anion, particularly an organic anion such as a sulfonate e.g. of the formula R′SO
3
where R′ is suitably optionally substituted alkyl, particularly perfluoroalkyl typically having 1 to about 12 carbon atoms such as triflate and the like; carbocyclic aryl such as pentafluorophenylsulfonate; and the like; or X is suitably a carboxylate, e.g. groups of the formula R″COO— where R″ is optionally substituted alkyl having 1 to about 18 carbons or optionally substituted aryl such as phenyl and the like. Preferred substituents of substituted carboxylate anions include halo, particularly fluoro.
Particularly preferred compounds of the above formulae are those that have multiple naphthyl groups, such as compounds of the following Formulae IA, IB, and IIA:
wherein in each of Formula IA, IB and IIA, R, n, R1 and X are the same as defined for Formulae I and II above.
In Formulae I and II, IA, IB and IIA, a naphthyl group may be linked to the iodonium or sulfonium cation at either the 1- or 2-naphthyl positions.
In a further aspect, sulfonium and iodonium PAGs are provided that contain at least one thienyl substituent. Preferred thienyl-substituted PAGs of the invention include sulfonium and iodonium compounds of the following Formulae III and IV:
wherein in Formulae III and IV: R, R
1
and X are the same as defined in Formula I and II above;
in Formula III, m is 1, 2 or 3;
in Formula IV, m is 1 or 2; and
each n is an integer equal to 0 (where the thienyl group has no non-hydrogen substituents), 1, 2 or 3, preferably 0, 1 or 2.
Preferred PAGs of Formulae III and IV include compounds that have multiple thienyl substituents, such as compounds of the following Formulae IIIA, IIIB, and IVA:
wherein in Formulae IIIA, IIIB and IVA: each R, R
1
, n and X is the same as defined for Formnulae III and IV above.
In Formulae III, IV, IIIA, IIIB and IVA a thienyl group may be linked to the iodonium atom or sulfonium atom at the 2- or 3-thienyl ring positions.
In a further aspect, sulfonium and iodonium PAGs are pr
Cameron James F.
Pohlers Gerhard
Ashton Rosemary
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Shipley Company L.L.C.
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