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
2000-11-14
2003-02-25
Baxter, Janet (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
C430S286100, C430S905000, C430S910000, C526S242000, C526S171000, C560S120000
Reexamination Certificate
active
06524765
ABSTRACT:
This invention relates to (1) a polymer having specific acid lability-imparting units, (2) a resist composition comprising the polymer as a base resin, providing a high dissolution contrast before and after exposure, and especially suited as micropatterning material for VLSI fabrication, and (3) a patterning process using the resist 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 transmittance 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 freedom of polymerization. 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 (1) a polymer having improved reactivity and rigidity, (2) a resist composition comprising the polymer as a base resin and achieving significantly surpassing sensitivity, resolution and etching resistance over prior art compositions, and (3) a patterning process using the resist composition.
It has been found that a polymer comprising recurring units of the following general formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000 possesses both high rigidity and reactivity, and that a resist composition using the polymer as a base resin has a high sensitivity, high resolution and high etching resistance and is very useful in precise microfabrication.
Accordingly, the invention provides a polymer comprising units of the following general formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000.
Herein R
1
is an acid labile group, R
2
is hydrogen or a straight or branched alkyl group of 1 to 4 carbon atoms, Z is a tetravalent hydrocarbon group of 2 to 10 carbon atoms, and k is equal to 0 or 1.
In one preferred embodiment, the polymer comprises units of at least one of the following general formulae (2-1) to (3-2).
Herein R
1
, R
2
and k are as defined above, and z1 to z3 are integers of 0 to 4.
In a further preferred embodiment, the polymer comprises units of at least one of the following general formulae (4-1) to (8-1).
Herein k is as defined above; at least one of R
3
to R
6
is a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms, and the remainders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
3
to R
6
, taken together, may form a ring, and when they form a ring, at least one of R
3
to R
6
is a carboxyl or hydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms, and the remainders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms; at least one of R
7
to R
10
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO
2
— partial structure, and the remainders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
7
to R
10
, taken together, may form a ring, and when they form a ring, at least one of R
7
to R
10
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO
2
— partial structure, and the remainders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms; R
11
is hydrogen, methyl or CO
2
R
13
; R
12
is hydrogen, methyl or CH
2
CO
2
R
13
; R
13
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
14
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclic hydrocarbon group; R
15
is an acid labile group; and X is CH
2
or an oxygen atom.
In another aspect, the invention provides a resist composition comprising the above-defined polymer as a base resin.
In a further aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition of claim 4 onto a substrate to form a coating; heat treating the coating and then exposing it to high-energy radiation or electron beams through a photo mask; and optionally heat treating the exposed coating and developing it with a developer.
The units of formula (1-1) or (1-2) each have two acid labile group-blocked carboxylic acid sites per fused ring skeleton. The polymer having these units has a substantially high dissolution rate in a basic developer in the deblocked state as compared with prior art polymers comprising units having only one blocked carboxylic acid. The use of these units insures a sufficiently high dissolution rate in the deblocked state even when units for imparting another property (e.g., units for imparting substrate adhesion) are introduced in a substantial proportion. This suggests that both a high dissolution contrast and a firm substrate bond are accomplished. The resist composition having the polymer formulated as the base resin has a high sensitivity, resolution and etching resistance and eliminates the drawbacks of prior art resist compositions including poor resolution upon micropatterning, peeling, and pattern extinction after etching.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Polymer
The polymer or high molecular weight compound of the invention is defined as comprising units of the following general formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000.
In the above formulae, k is equal to 0 or 1. Accordingly, the formulae (1-1) and (1-2) can be represented by the following formulae (1-1-1) to (1-2-2).
Herein R
1
is an acid labile group. R
2
is hydrogen or a straight or branched alkyl group of 1 to 4 carbon atoms, examples of which include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl and tert-butyl. Z is a tetravalent hydrocarbon group of 2 to 10 carbon atoms.
The units of the general formula (1-1) or (1-2) are preferably units of the following general formulae (2-1) to (3-2):
Herein R
1
, R
2
and k are as defined above, and z1 to z3 are integers of 0 to 4, preferably 0 t
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nishi Tsunehiro
Tachibana Seiichiro
Baxter Janet
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
Thornton Yvette C.
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