Chemical amplification type resist composition

Details Chemical amplification type resist composition Chemical amplification type resist composition

2001-01-17

2003-11-25

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

C430S176000, C430S286100, C430S905000, C430S909000, C526S313000, C526S242000, C528S497000

Reexamination Certificate

active

06653044

ABSTRACT:

This invention relates to chemical amplification type resist compositions.
BACKGROUND OF THE INVENTION
While a number of efforts are currently being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, lithography is thought to hold particular promise as the microfabrication technology. Deep UV, electron beam and x-ray lithography processes enable micropatterning to a feature size of 0.2 &mgr;m or less.
The recently developed, acid-catalyzed, chemical amplification type positive resist materials (see JP-B 2-27660 and JP-A 63-27829) utilize a high-intensity KrF excimer laser as the deep UV light source and are expected to comply with the deep UV lithography because of their many advantages including high sensitivity, resolution and dry etching resistance. For instance, JP-B 6-266112 and JP-A 8-101509 disclose hydroxystyrene and methacrylate copolymers. A need exists for a resist material capable of utilizing a high-intensity ArF excimer laser.
When micropatterning to a finer feature size is required, these resist materials fail to form a pattern of the desired line width or are unsatisfactory in sensitivity and resolution. There is a demand for a further improvement.
SUMMARY OF THE INVENTION
An object of the invention is to provide a chemical amplification type resist composition which is improved in sensitivity, resolution, exposure latitude, process adaptability and reproducibility over prior art resist compositions and is capable of forming a resist pattern having good plasma etching resistance and heat resistance.
It has been found that a chemical amplification type resist composition using a base resin having a narrow dispersity (or polydispersity index) as obtained by a specific method to be described later is improved in resolution, exposure latitude, and process adaptability. This composition is advantageous in practical application and precise micropatterning and thus best suited as a resist material for the manufacture of VLSIs.
The base polymers previously developed for resist use have a wide dispersity and contain low molecular weight components because of their polymerization technique, especially radical polymerization, not considered to be living polymerization. Paying attention to the dispersity of a polymer, the inventor has found that when a polymer having a narrow dispersity, especially a polymer from which a low molecular weight component has been removed by fractionation, is formulated in a chemical amplification type resist composition as the base resin, the resulting resist composition has a noticeably increased contrast of alkali dissolution rate before and after exposure, high sensitivity, high resolution and is suited as a micropatterning resist material for the manufacture of VLSIs.
According to the invention, there is provided a chemical amplification type resist composition comprising a polymer having a molecular weight dispersity of 1.0 to 1.5, and especially 1.0 to 1.4. The polymer is a polymer comprising recurring units of formula (1) and recurring units of formula (2), a polymer comprising recurring units of formula (2), a polymer comprising recurring units of formula (2) and recurring units of formula (4), a polymer comprising recurring units of formula (3), or a polymer comprising recurring units of formula (4), the formulas being shown below.
Herein R
1
is an alkyl, alkoxyalkyl, acetyl or carbonylalkoxy group, each unit may be of one type or a mixture of at least two types, p is a positive number, q is 0 or a positive number, satisfying 0<p/(p+q)≦1.
Herein R
2
is hydrogen or methyl, and R
3
is a tertiary hydrocarbon group of 4 to 30 carbon atoms.
Herein R
4
is a tertiary hydrocarbon group of 4 to 30 carbon atoms, R
5
to R
8
are independently selected from the group consisting of a hydrogen atom, ester group, alkoxycarbonylalkyl group, lactone group, carboxyl group, and cyclic acid anhydride group, or two of R
5
to R
8
, taken together, may form a cyclic lactone group or acid anhydride group, r is a positive number, s is 0 or a positive number, satisfying 0<r/(r+s)≦1.
Herein R
9
is a tertiary hydrocarbon group of 4 to 30 carbon atoms, and n is equal to 0 or 1.
In one preferred embodiment, the polymer having a molecular weight dispersity of 1.0 to 1.5 has been fractionated from a starting polymer containing a low molecular weight component by dissolving the starting polymer in a good solvent, admitting the resulting solution into a poor solvent, and fractionally removed the low molecular weight component in the starting polymer. The poor solvent and the good solvent are preferably selected in accordance with the starting polymer from the group consisting of water, acetone, ethyl acetate, methyl acetate, diethyl ether, tetrahydrofuran, cyclohexanone, diethylene glycol dimethyl ether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate, ethyl lactate, methanol, ethanol, isopropyl alcohol, pentane, hexane, toluene, benzene, and xylene.
By virtue of the narrow dispersity effect of the polymer, the chemically amplified resist composition having the narrow dispersity polymer formulated therein is improved in performance as compared with prior art base resins having a wide dispersity. As compared with base resins obtained by radical polymerization of hydroxystyrene and methacrylate, for example, a base resin having a dispersity narrowed to about 1.4 provides an improved resolution. Also since the low molecular weight fraction is removed from the polymer, the resist pattern shape is precisely defined and the stability as resist is improved.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The chemical amplification type resist composition of the invention comprises a polymer comprising recurring units of formula (1) and recurring units of formula (2), a polymer comprising recurring units of formula (2), a polymer comprising recurring units of formula (2) and recurring units of formula (4), a polymer comprising recurring units of formula (3), or a polymer comprising recurring units of formula (4).
Herein R
1
is an alkyl, alkoxyalkyl, acetyl or carbonylalkoxy group, each unit may be of one type or a mixture of at least two types, p is a positive number, q is 0 or a positive number, satisfying 0<p/(p+q)≦1.
Herein R
2
is hydrogen or methyl, and R
3
is a tertiary hydrocarbon group of 4 to 30 carbon atoms.
Herein R
4
is a tertiary hydrocarbon group of 4 to 30 carbon atoms, R
5
to R
8
are independently selected from the group consisting of a hydrogen atom, ester group, alkoxycarbonylalkyl group, lactone group, carboxyl group, and cyclic acid anhydride group, or two of R
5
to R
8
, taken together, may form a cyclic lactone group or acid anhydride group, r is a positive number, s is 0 or a positive number, satisfying 0<r/(r+s)≦1.
Herein R
9
is a tertiary hydrocarbon group of 4 to 30 carbon atoms, and n is equal to 0 or 1.
More particularly, the alkyl groups represented by R
1
are preferably straight, branched or cyclic alkyl groups of 1 to 20 carbon atoms, especially 1 to 10 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl, and cyclohexylethyl. The alkoxyalkyl groups represented by R
1
are preferably straight, branched or cyclic groups of 2 to 20 carbon atoms, especially 2 to 10 carbon atoms, for example, straight or branched acetal groups such as 1-methoxyethyl, 1-ethoxyethyl, 1-n-propoxyethyl, 1-isopropoxyethyl, 1-n-butoxyethyl, 1-isobutoxyethyl, 1-sec-butoxyethyl, 1-tert-butoxyethyl, 1-tert-amyloxyethyl, 1-ethoxy-n-propyl, 1-cyclohexyloxyethyl, methoxypropyl, ethoxypropyl, 1-methoxy-1-methylethyl, and 1-ethoxy-1-methylethyl; and cyclic acetal groups such as tetrahydrofuranyl and tetrahydropyranyl. Of these, ethoxyethyl, butoxyethyl and ethoxypropyl are preferred. The carbonylalkoxy groups represented by R
1
are preferably those of 2 to 20 carbon atoms, especially 2 to 10 carbon a

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