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
2002-06-13
2004-06-08
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, C430S905000, C526S281000, C526S316000, C549S263000, C549S265000
Reexamination Certificate
active
06746818
ABSTRACT:
This invention relates to (i) a novel (meth)acrylate compound having a lactone structure useful as a monomer for polymerization, (ii) a polymer obtained therefrom, (iii) a photoresist composition, especially a chemically amplified photoresist composition, comprising the polymer as a base resin and suited for photolithographic microfabrication, and (iv) a patterning process using the photoresist composition.
BACKGROUND OF THE INVENTION
While a number of recent efforts are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. In particular, photolithography using a KrF or ArF excimer laser as the light source is strongly desired to reach the practical level as the micropatterning technique capable of achieving a feature size of 0.3 &mgr;m or less.
The resist materials for use in photolithography using light of an excimer laser, especially ArF excimer laser having a wavelength of 193 nm, are, of course, required to have a high transparency to light of that wavelength. In addition, they are required to have an etching resistance sufficient to allow for film thickness reduction, a high sensitivity sufficient to eliminate any extra burden on the expensive optical material, and especially, a high resolution sufficient to form a precise micropattern. To meet these requirements, it is crucial to develop a base resin having a high transparency, rigidity and reactivity. None of the currently available polymers satisfy all of these requirements. Practically acceptable resist materials are not yet available.
Known high transparency resins include copolymers of acrylic or methacrylic acid derivatives and polymers containing in the backbone an alicyclic compound derived from a norbornene derivative. All these resins are unsatisfactory. For example, copolymers of acrylic or methacrylic acid derivatives are relatively easy to increase reactivity in that highly reactive monomers can be introduced and acid labile units can be increased as desired, but difficult to increase rigidity because of their backbone structure. On the other hand, the polymers containing an alicyclic compound in the backbone have rigidity within the acceptable range, but are less reactive with acid than poly(meth)acrylate because of their backbone structure, and difficult to increase reactivity because of the low flexibility of polymerization. Additionally, since the backbone is highly hydrophobic, these polymers are less adherent when applied to substrates. Therefore, some resist compositions which are formulated using these polymers as the base resin fail to withstand etching although they have satisfactory sensitivity and resolution. Some other resist compositions are highly resistant to etching, but have low sensitivity and low resolution below the practically acceptable level.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel (meth)acrylate compound having a lactone structure useful as a monomer to form a polymer for use in the formulation of a photoresist composition which exhibits firm adhesion and high transparency when processed by photolithography using light with a wavelength of less than 300 nm, especially ArF excimer laser light as the light source. Another object of the invention is to provide a polymer obtained from the (meth)acrylate compound, a photoresist composition comprising the polymer, and a resist patterning process.
We have found that a (meth)acrylate compound having a lactone structure of formula (1), (2), (3), (4) or (5) can be prepared in high yields by a simple method to be described later, that a polymer obtained from this (meth)acrylate compound has high transparency at the exposure wavelength of an excimer laser, and that a resist composition comprising the polymer as a base resin is improved in adhesion to substrates.
In a first aspect, the present invention provides a (meth)acrylate compound having the following general formula (1).
Herein, R
1
is hydrogen or methyl, R
2
and R
3
each are hydrogen or a straight, branched or cyclic alkyl group having 1 to 15 carbon atoms, or R
2
and R
3
, taken together, may form a ring and in that event, R
2
and R
3
together represent a straight, branched or cyclic alkylene group having 2 to 15 carbon atoms, X is —CH
2
—, —CH
2
CH
2
— or —O— or two separate —H, and the broken line represents a single bond or divalent organic group that connects the norbornane ring, bicyclo[2.2.2]octane ring, 7-oxanorbornane ring or cyclohexane ring structure to the &ggr;-butyrolactone ring structure, or a structure that shares one or two constituent carbon atoms between these ring structures.
Preferred (meth)acrylate compounds have the following general formula (2).
Herein, R
1
, R
2
, R
3
, and X are as defined above, and Y is —(CH
2
)
n
— in which at least one methylene group may be replaced by an oxygen atom, and n is an integer of 0 to 6.
Also preferred are (meth)acrylate compounds having the following general formulae (3) and (4).
Herein, R
1
, R
2
, R
3
, and X are as defined above.
Also preferred are (meth)acrylate compounds having the following general formula (5).
Herein, R
1
, R
2
, R
3
, and X are as defined above.
In a second aspect, the invention provides a polymer comprising recurring units of the following general formula (6).
Herein, R
1
, R
2
, R
3
, X and the broken line are as defined above.
The polymer may further include recurring units of the following general formula (7).
Herein, R
4
is hydrogen or methyl and R
5
is a tertiary alkyl group having 4 to 20 carbon atoms, said polymer having a weight average molecular weight of 2,000 to 100,000.
In a third aspect, the invention provides a photoresist composition comprising (A) the polymer defined above, (B) a photoacid generator, and (C) an organic solvent.
In a fourth aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the photoresist composition onto a substrate to form a film; heat treating the film and then exposing it to high-energy radiation having a wavelength of less than 300 nm or electron beams through a photo mask; and optionally heat treating the exposed film and developing it with a developer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The (meth)acrylate compounds of the present invention have the general formula (1).
Herein, R
1
is hydrogen or methyl. R
2
and R
3
each are hydrogen or a straight, branched or cyclic alkyl group having 1 to 15 carbon atoms, preferably 1 to 8 carbon atoms, or R
2
and R
3
, taken together, may form a ring and in that event, R
2
and R
3
together represent a straight, branched or cyclic alkylene group having 2 to 15 carbon atoms, preferably 2 to 5 carbon atoms. X is —CH
2
—, —CH
2
CH
2
— or —O— or two separate —H. The broken line represents a single bond or divalent organic group that connects the norbornane ring, bicyclo[2.2.2]octane ring, 7-oxanorbornane ring or cyclohexane ring structure to the &ggr;-butyrolactone ring structure, or a structure that shares one or two constituent carbon atoms between these ring structures.
The invention contemplates a norbornane ring structure when X is —CH
2
—, a bicyclo[2.2.2]octane ring structure when X is —CH
2
CH
2
—, and a 7-oxanorbornane ring structure when X is —O—. And when X is two separate —H, a cyclohexane ring structure is formed as shown below.
When the broken line represents a divalent organic group, alkylene groups of 1 to 6 carbon atoms and oxaalkylene groups having 2 to 5 carbon atoms are exemplary.
Of the (meth)acrylate compounds according to the invention, those of the following formula (2) are preferred as well as those of the following formulae (3), (4) and (5).
In formula (2), Y is —(CH
2
)
n
— in which one or more methylene groups may be replaced by one or more oxygen atoms, and n is an integer of 0 to 6. R
1
, R
2
, R
3
and X are as defined above.
Illustrative, non-limiting examples of the (meth)acryl
Hasegawa Koji
Kinsho Takeshi
Watanabe Takeru
Ashton Rosemary
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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