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
1999-06-11
2004-06-15
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
C430S326000, C430S910000, C430S914000, C430S271100, C430S272100, C430S311000
Reexamination Certificate
active
06749983
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.
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 reaching of photoresist compositions and methods of making and using the same.
More recently, “chemically-amplified” resists have become of increased interest, especially 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 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 base soluble functional group is provided, e.g., carboxylic acid or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer.
Also recently interest has increased in photoresists that can be photoimaged with short wavelength radiation, including exposure radiation having wavelengths of about 250 nm or less, or even about 200 nm or less, such as wavelengths of about 248 nm and 193 nm. Such photoresists offer the potential of forming images of smaller features than may be possible at longer wavelength exposures.
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-micron and sub-half micron features.
For example, many current chemically-amplified positive resists require use of relatively strong photogenerated acids and/or use of a relatively high temperature post-exposure bake (PEB) treatment to conduct the desired deprotection reaction.
However, in many instances, use of photoacid generators that produce weaker photoacids and use of relatively low PEB temperatures (e.g. 110° C. or less) would be a significant advantage. For example, if the desired deprotection chemistry could be carried out with a weaker acid, a wider range of photoacid generators could be potentially employed. Moreover, the industry continually seeks use of lowered post-exposure-bake temperatures because of uniformity considerations.
It thus would be desirable to have new photoresist compositions, particularly positive resist compositions that can be effectively imaged at short wavelengths, particularly sub-200 nm wavelengths such as 193 nm. It would be particularly desirable to have new chemically amplified positive photoresist compositions that employ photoacid generators that produce weaker photoacids and that can be activated with relatively low PEB temperatures.
SUMMARY OF THE INVENTION
The present invention provides novel polymers that contain repeating units that include acid-labile moieties that undergo a deprotection or cleavage reaction in the presence of photogenerated acid. The invention also includes photoresist compositions that comprise a photoactive component and a resin binder component that includes such a polymer with acid-labile moieties. Preferred photoresists of the invention are chemically-amplified positive resists that are imaged with deep UV wavelengths, including sub-300 nm and sub-200 nm wavelengths such as 248 nm and 193 nm.
Polymers of the invention include one or more structural groups that preferably are capable of reducing the temperature dependence of deprotection of the polymer's acid-labile moieties. That is, preferred polymers include moieties that can provide anchimeric assistance with photoacid-induced cleavage of the acid-labile leaving groups of the polymer. Such anchimeric assistance, also known as neighboring group participation, typically involves stabilization of a carbocation intermediate generated during deprotection of the polymer's acid labile groups.
Preferred polymer moieties that can provide anchimeric assistance in a photoacid-induced cleavage reaction will exhibit a value, A, of anchimeric assistance that is greater than the value, A, of achimeric assistance provided by pendant polymer moieties of —C(═O)Oadamantyl, —C(═O)Onorbornyl, or —C(═O)O cyclohexyl, with the same model compounds used to determine the value A of the preferred polymer moiety of the invention as well as the value A of —C(═O)Oadamantyl, —C(═O)Onorbornyl, or —C(═O)O cyclohexyl. The A of anchimeric assistance is defined to mean herein the value A as measured by the following rate constant ratio:
A
=
k
-
k
0
k
0
wherein that value A is the measured anchimeric assistance, k and k
o
are observed rate constants of test and model compounds respectively. The model compound is chosen to be as structurally akin to the test compound as possible. Thus for example, to determine value A for polymer moieties of —C(═O)Oadamantyl, the condensation product of adamanylacrylate could be the test compound and the model compound could be the condensation product of t-butylacrylate and having approximately the same molecular (M
w
) and dispersity as the test compound of the adamantylacrylate polymer. Again, that same model compound would then be used to determine the value A for the preferred polymer moiety being considered. For a discussion of such determination of anichimeric assistance values, see N. S. Isaacs, Physical organic chemistry, ch. 13, particularly pages 646-650 thereof(2d edition, 1995, Longman Scientific & Technical, Essex, U.K.), incorporated herein by reference.
More specifically, pendant photoacid-labile groups that contain esters of bridged alicyclic groups will be suitable, particularly acid-labile esters of optionally substituted isobornyl. Other suitable bridged acid-labile esters include e.g. esters of fenchol, pinenol, 3,2,0 bridged-systems and 2,2,1-bridged systems. Esters of optionally substituted heteroatom-containing groups are also preferred, particula
Szmanda Charles R.
Taylor Gary N.
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Huff Mark F.
Lee Sin J.
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