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
2002-03-27
2003-02-11
Lambkin, Deborah C. (Department: 1626)
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, C526S281000, C549S300000
Reexamination Certificate
active
06517994
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lactone ring-containing (meth)acrylate ester compound which is a novel compound not known in the prior art and a polymeric compound thereof as well as to a photoresist composition containing the polymer as the base resinous ingredient and a photolithographic resist patterning method by using the photoresist composition.
Along with the trend in recent years in the technology of semiconductor devices such as LSIs toward higher and higher degrees of integration and higher and higher working velocities, the technology of photolithographic resist patterning is continuedly required to accomplish further upgrading in respect of fineness of resist patterning to meet the modern pattern design rule. As is generally understood, ultrafine patterning of a resist layer having a fineness of as fine as 0.3 &mgr;m or even finer required in the next-generation technology can be accomplished by the so-called deep ultraviolet photolithography using ultraviolet light of a very short wavelength such as KrF excimer laser beams, ArF excimer laser beams and the like as the patterning exposure light although such an ultrafine resist patterning technology is still under development.
It is of course that the photoresist composition used in such a deep UV photolithographic process by using excimer laser beams or, in particular, ArF excimer laser beams of 193 nm wavelength as the patterning exposure light is required to have very high transparency to the light of the wavelength. In addition, the requirements for the photoresist composition include high etching resistance to withstand etching even with a decreased thickness of the resist layer, high sensitivity to the exposure light to decrease the load on the expensive optical system for exposure and, inter alia, high pattern resolving power in order to give a patterned resist layer having high fidelity to the extremely fine photomask pattern. In order to satisfy all of these requirements, the photoresist composition must be formulated by using a film-forming base resin having high transparency to the exposure light, high rigidity and high reactivity in combination. Although a variety of proposals and attempts have been made to obtain such a resinous compound, none of the resinous compounds known in the art can meet these requirements and none of the currently available photoresist compositions are suitable for use in the deep UV photolithographic process.
Examples of known resinous polymeric compounds having high transparency to the deep UV light include copolymers of a monomer mixture containing an acrylic or methacrylic acid derivative and polymers having monomeric units derived from an aliphatic cyclic compound originating in a norbornene compound. None of these polymeric compounds, however, can satisfy all of the requirements for the resinous ingredient in a photoresist composition for the deep UV photolithographic patterning technology. For example, while it is a relatively easy matter to obtain a (meth)acrylic acid derivative-based copolymeric resin having high reactivity because the copolymer is susceptible to the introduction of highly reactive monomeric units or to the increase of acid-dissociable solubility-reducing substituent groups, the main chain structure of the resin molecules renders it extremely difficult to enhance rigidity of the resin. On the other hand, the polymeric resin having an alicyclic monomeric structure in the main chain is satisfactory in respect of rigidity but the reactivity with an acid cannot be high enough as compared with the (meth)acrylate-based copolymeric resins and the reactivity cannot be increased easily due to the low versatility in polymerization.
In addition, the hydrophobicity of the main chain structure thereof is so high that adhesion of the photoresist layer to the substrate surface cannot be strong enough. Accordingly, a photoresist composition prepared by using these resins as the base resin cannot simultaneously satisfy the requirements for the sensitivity, pattern resolution and etching resistance. Namely, some of the photoresist compositions are acceptable in respect of the sensitivity and pattern resolution but unacceptably poor in respect of the etching resistance while the others exhibit good etching resistance but are poor in the sensitivity and pattern resolution.
SUMMARY OF THE INVENTION
Accordingly, the primary object of the present invention completed in view of the above described problems and disadvantages in the prior art is to provide a novel and improved photoresist composition suitable for use in the deep UV photolithographic resist patterning process by using UV light having a wavelength of 300 nm or shorter or, in particular, ArF excimer laser beams of 193 nm wavelength as the patterning exposure light as well as a deep UV photo-lithographic resist patterning method by using the improved photoresist composition. The secondary object of the present invention is to provide a novel polymeric resinous compound suitable for use as a base resin ingredient in the photoresist composition for the deep UV photolithographic resist patterning method as well as a novel monomeric compound from which the aforementioned resinous compound can be prepared by polymerization.
Thus, firstly, the monomeric compound provided by the present invention, which is a novel compound not known in the prior art or not described in any literatures, is 3-(meth)acryloyloxymethyl-2,6-norbornane carbolactone as a norbornyl (meth)acrylate ester compound having a lactone ring structure as represented by the general formula (1) below;
in which R
1
is a hydrogen atom for the acrylate compound or a methyl group for the methacrylate compound.
Secondly, the present invention provides a novel polymeric compound suitable as the base resinous ingredient in a deep UV photoresist composition, which consists of recurring monomeric units, forming the main chain structure, comprising the units represented by the general formula (1a) below:
in which R
1
is a hydrogen atom or a methyl group, and preferably having a weight-average molecular weight in the range from 2000 to 100000 when the intended application thereof is as a base resin in a photoresist composition.
Thirdly, the present invention provides a copolymeric resinous compound suitable for use as a base resin in a deep UV photoresist composition, comprising two types of recurring monomeric units in combination including the monomeric units of the first type represented by the above given general formula (1a) and monomeric units of the second type represented by the general formula (2a) below:
in which R
1
has the same meaning as defined above and R
2
is a tertiary alkyl group or tertiary cycloalkyl group having 4 to 20 carbon atoms.
Fourthly, the present invention provides a novel photoresist composition suitable for the deep UV photolithographic resist patterning process, which comprises, as a uniform solution:
(A) a base resin which is a polymer comprising the recurring monomeric units represented by the above given general formula (1a) or a copolymer comprising two types of the recurring monomeric units represented by the above given general formulas (1a) and (2a);
(B) a radiation-sensitive acid-generating compound; and
(C) an organic solvent as a solvent for the components (A) and (B).
Fifthly, the present invention provides a novel deep UV photolithographic resist patterning method which comprises the steps of:
i) coating a substrate with the above defined photoresist composition in the form of a solution to form a coating layer of the solution;
ii) drying the coating layer to form a dried photoresist layer on the substrate surface;
iii) patternwise exposing the dried photoresist layer to ultraviolet light having a wavelength not exceeding 300 nm;
iv) optionally, subjecting the photoresist layer to a post-exposure baking treatment; and
v) developing the photoresist layer with an aqueous alkaline solution to patternwise dissolving away the photoresist layer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Lambkin Deborah C.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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