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
2001-01-12
2003-11-04
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
C430S905000, C526S272000, C526S281000
Reexamination Certificate
active
06641974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemically amplified resist composition useful for a micro-engineering process using various radiations including far ultraviolet ray (e.g., KrF excimer laser and ArF excimer laser), X-ray (e.g., synchrotron radiation) and charged particle beams (e.g. electron beam) and, more particularly, to a chemically amplified resist composition comprising (A) a polymer for resist having an acid labile group, (B) a photoacid generator, and (C) a low molecular weight additive for increasing dry etching resistance and resolution of the pattern.
2. Description of the Related Art
In the fabrication of semiconductor devices, a resist is applied on a substrate such as silicon wafer to form a coating and exposed to radiations to form a pattern, after which the resist is developed to form a positive or negative pattern, i.e., an image is created by lithography.
As the LSI and VLSI technologies in the fabrication of semiconductor integrated circuits tend toward higher integration, higher density, miniaturization and higher speed, a rule of submicron (less than 0.2 micron) is required for the fineness of pattern. Accordingly, the lithography light sources are shifting towards shorter wavelength from the existing g- or i-line band and there is an increasing interest in the lithography using far UV radiations, KrF or ArF excimer laser, X-ray or electron beams.
Near UV radiations including i-line have been mainly used in the existing lithography process but are known insufficient to form sub-quarter (0.25) micron patterns. For the formation of sub-quarter micron patterns, the attention is focused on radiation sources in the shorter wavelength band including far UV radiations such as excimer lasers, X-ray and electron beams, and particularly KrF or ArF excimer laser.
Resist compositions suitable for the excimer laser lithography comprise a polymer component having an acid labile group, a component generating an acid upon irradiation with a radiation (hereinafter, referred to as “photoacid generator”), and a solvent. Such resists comprising the resist compositions undergo chemical amplification due to the photoacid generator in the lithography and will be hereinafter referred to as “chemically amplified resist”.
For example, chemically amplified resist compositions containing a polymer having a ter-butyl ester group of carboxylic acid or a ter-butylcarbonyl group of phenol, and a photoacid generator are disclosed in Japanese Patent Application Kokoku No. 2-27,660. These resist compositions have such an advantage that the catalytic action of the acid generated under irradiation of a radiation causes the tert-butyl ester group or tert-butylcarbonyl group of the polymer decomposed to leave a hydroxyl group, which makes the exposed area of the resist very soluble in an alkaline developing solution.
However, chemically amplified resists used in the KrF excimer laser lithography are mostly composed of a phenol resin as a base material containing aromatic rings and unsuitable for use in the ArF excimer laser because the aromatic rings in the phenol resin absorb lots of the ArF excimer laser. In an attempt to overcome this problem, many studies have been made on polyacrylate derivatives as a matrix resin having less absorption of the ArF excimer laser than the phenol resin (See. Japanese Patent Laid-Open Kokoku No. 4-226,461, Proc. SPIE, 1996, vol. 2724, p. 377).
Polyacrylate absorbs less radiation having a wavelength falling within the ArF excimer laser region but is adversely inferior in the dry etching resistance. To solve this problem, there have recently been made many studied on the method for improving the etching resistance of the resist with an alicyclic derivative introduced to the side chain of the polyacrylate, in which case the hydrophobic property of the alicyclic derivative deteriorates the affinity to the developing solution. The adhesion between the resist and the substrate is an important factor in formation of less than 0.2 micron patterns. So, the existing polyacrylate matrix resin contains a carboxylic acid at the side chain in order to enhance the adhesion to the substrate (See. Proc. SPIE, 1997, vol. 3049, p. 126). However, an excess of the carboxylic acid increases the solubility of the polyacrylate resin in the alkaline aqueous solution and causes a need of varying the concentration of the alkaline developing solution.
An example of matrix resin that has improved dry etching resistance and hydrophilic property may include a copolymer of anhydrous maleic acid and olefin (See. Proc. SPIE, 1997, vol. 3049, p. 92). The anhydrous maleic acid possesses the hydrophilic property and acts as a promoter enabling copolymerization with the olefin monomer at low temperature and low pressure. Also, the olefin monomer may contain various substituents at the side chain to enhance dry etching resistance and resolution (See. Proc. SPIE, 1998, vol. 3333, p. 463).
Recently, low molecular weight additives for use in the resist composition containing a copolymer resin of anhydrous maleic acid and olefin monomers are being watched with keen interest so as to improve the residual coating property, increase dry etching resistance and reduce refining effect in the formation of patterns (Korean Patent Laid-Open No. 98-064842; and Proc. SPIE, 1998, vol. 3333, p. 73).
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a chemically amplified photoresist sensitive to the far UV radiations including KrF or ArF excimer laser and, more particularly, a chemically amplified resist composition which has a high transparency to the ArF excimer laser to provide high resolution and sensitivity of the photoresist and is excellent in adhesion to the substrate, dry etching resistance and developing property due to a low molecular weight additive having a ring structure with an acid-labile acetal or ketal group.
To achieve the above object of the present invention, there is provided a chemically amplified positive photoresist composition comprising:
a multi-component copolymer represented by the formula 1 and having a polystyrene-reduced weight average molecular weight (Mw) of 3,000 to 50,000 and a molecular weight distribution (Mw/Mn) of 1.0 to 3.0;
a low molecular weight additive represented by the formula V;
an acid generator; and
a solvent,
[Formula 1]
wherein X and Y independently comprise a repeating unit selected from the group consisting of monomers represented by the formulas (II), (III) and (IV):
wherein R
1
is a hydrogen atom, a normal, branched, monocyclic or polycyclic alkyl group having 1 to 20 carbon atoms, or a normal, branched, monocyclic or polycyclic alkyl carbonyl group having 1 to 20 carbon atoms, including acetyl group, t-butyl oxycarbonyl group, cyclohexane carbonyl group, adamanthane carbonyl group and bicyclo[2,2,1]heptane methyl carbonyl group; R
2
is a hydrogen atom, a hydroxyl group, a carboxyl group, an alkyl or alkoxy group having 1 to 20 carbon atoms, an alkyl or alkoxy group containing a hydroxyl or carboxyl group, a normal or branched alkyloxycarbonyl or alkoxyalkylcarbonyl group, or a monocyclic or polycyclic alkyloxycarbonyl group; R
3
is a hydrogen atom, or a normal, branched, monocyclic or polycyclic alkyl group having 1 to 20 carbon atoms, including methyl group, ethyl group, t-butyl group, isopropyl group, adamanthyl group, and bicyclo[2,2,1]heptane methyl group; and l, m, n and o are independently a number representing the repeating unit of the polymer and satisfying 0≦l/(l+m+n+o)≦0.5, 0≦m/(l+m+n+o)≦0.5, 0≦n/(l+m+n+o)≦0.35, 0.4≦o/(l+m+n+o)≦0.6, and 0.15≦(l+m)/(l+m+n+o)≦0.5,
[Formula V]
wherein R
4
and R
5
are the same as or different from each other and each represents a normal, branched, monocyclic or polycyclic alkyl group having 1 to 20 carbon atoms; and R
6
is a hydrogen atom, or a normal, branched, monocycl
Kim Jae Young
Park Joo Hyeon
Baxter Janet
Clarke Yvette M.
Davidson Davidson & Kappel LLC
Korea Kumho Petrochemical Co. Ltd.
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