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
2002-03-28
2004-02-24
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
Reexamination Certificate
active
06696218
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a chemical amplification type positive photo resist composition to be used for fine processing of semiconductors.
In recent years, with high degree of integration for integrated circuits, demands for a fine pattern in submicron order formed with high precision have been increased. Under the circumstances, excimer laser lithography has been marked since it enables the production of 64M DRAM and 1 G DRAM. A chemical amplification type resist that takes advantage of the chemical amplification effect of acid catalysts is being adopted as a resist suitable for such excimer laser lithography process. In the chemical amplification type resist, acid generated from an acid generating agent at a irradiation-exposed portion under exposure to radiation behaves as a catalyst in a reaction caused by a subsequent heat treatment (post exposure bake; hereinafter sometimes abbreviated as “PEB”) to change solubility of the irradiation-exposed portion in an alkali developer, thereby providing a positive or a negative pattern.
Since such resist is required to exhibit a high resolution, a composition for the resist typically has a high transparency at the exposure wavelength. The resist typically used for KrF excimer laser lithography is a poly(p-hydroxystyrene) based resin wherein a part of the phenolic hydroxyl group is protected by a group cleavable due to the action of an acid. However, there has been raised a problem that the application of the resist with high transparency to a substrate without low reflectance ratio at a resist/substrate interface leads to a generation of standing wave in a resist layer, and a side wall of a resulting fine pattern formed from the resist layer has a wavy form. Since a form of the sidewall of fine pattern affects on a precision of fine processing, it is desired that the sidewall be evenly formed.
An object of the present invention is to provide a chemical amplification type positive resist composition that enables a resist pattern free from deformation in a side wall thereof and excellent in evenness, and is excellent in sensitivity as well as resolution and suitable for lithography using excimer laser beams such as Krf.
SUMMARY OF THE INVENTION
The present inventors have conducted intensive studies for attaining the above object, and have found that excellent capabilities are achieved by mixing a specific compound with a positive resist composition comprising a resin that can become soluble in an alkaline medium and an acid generating agent. The inventors have accomplished the present invention based on the finding and extensive researches.
More specifically, the present invention provides a chemical amplification type positive resist composition comprising a resin which has a polymerization unit derived from p-hydroxystyrene and a polymerization unit having a group unstable against acid, and is insoluble or hardly soluble in an alkaline medium itself but becoming alkaline-soluble after the acid-unstable group being cleaved by the action of the generated acid (hereinafter, the resin will be sometimes referred to as “resin that can become alkaline-soluble”); an acid generating agent; and at least one compound selected from compounds represented by the following formula (I).
wherein R
1
and R
2
each independently represents an alkyl group having 1 to 15 carbon atoms, an alkyl group having 1 to 8 carbon atoms wherein at least 3 hydrogen atoms are substituted by fluorine atoms, or an aryl group having 6 to 10 carbon atoms.
DESCRIPTION OF THE EMBODIMENTS
The composition of the present invention is characterized in containing a resin that can become alkaline-soluble, a radiation-sensitive acid generating agent and at least one of the compounds represented by the above formula (I). The compounds represented by the formula (I) may be used alone or in combination of two or more. The composition of the present invention achieves the effect of improving pattern form and evenness by using the specific compound(s) without deteriorating sensitivity and resolution.
In the formula (I), R
1
and R
2
each independently represent an alkyl group having 1 to 15 carbon atoms, an alkyl group having 1 to 8 carbon atoms wherein at least 3 hydrogen atoms are substituted by fluorine atoms, or an aryl group having 6 to 10 carbon atoms.
Specific examples of the compounds represented by the formula (I) include the following compounds.
The chemical amplification type resist composition of the present invention contains, in addition to at least one of the compounds represented by the formula (I), comprises a resin that can become alkaline-soluble as a binder component and an active compound that generates an acid by irradiation as a radiation-sensitive component. It takes advantage of catalysis of the acid generated from the irradiation-sensitive component at a irradiation beam-exposed portion. Generally, in a chemical amplification type positive resist, acid generated at a radiation beam-exposed portion is diffused by subsequent thermal treatment (post exposure bake) to cause cleavage of a protecting group in the resin or the like as well as to regenerate acid, thereby making the irradiation-exposed portion alkaline-soluble. The resin used as the binder component in the present invention is a binder resin that has a protecting group capable of being cleaved by acid, and originally is insoluble or hardly soluble in alkaline medium itself but becomes alkaline-soluble after the protecting group has been cleaved by the action of an acid.
Examples of the resin that has the protecting group capable of being cleaved by the action of an acid and originally is insoluble or hardly soluble in alkaline medium itself but becomes alkaline-soluble after the protecting group has been cleaved by the action of an acid may be: a polyvinylphenol resin; a polyisopropenylphenol resin; a resin in which a hydroxy group of the polyvinylphenol resin or the polyisopropenylphenol resin is partly converted to form an alkylether; a resin prepared by introducing a protecting group capable of being cleaved by the action of an acid into a resin having a phenol skeleton, such as a copolymer of vinylphenol or isopropenylphenol and other polymeric unsaturated compounds; a resin prepared by introducing a protecting group capable of being cleaved by the action of an acid to an alkaline-soluble resin such as those having a (meth)acrylic acid skeleton and the like.
Examples of the group having dissolution inhibiting capability against an alkaline developer but unstable against acid include: a group with its quaternary carbon bound to an oxygen atom such as tert-butyl, tert-butoxycarbonyl or tert-butoxycarbonylmethyl; an acetal group such as tetrahydro-2-pyranyl, tetrahydro-2-furyl, 1-ethoxyethyl, 1-(2-methylpropoxy)ethyl, 1-(2-methoxyethoxy)ethyl, 1-(2-acetoxyethoxy)ethyl, 1-{2-(1-adamantyloxyl)ethoxy}ethyl or 1-{2-(1-adamantanecarbonyloxy)ethoxy}ethyl; or a residue of a non-aromatic cyclic compound such as 3-oxocyclohexyl, 4-methyltetrahydro-2-pyrrone-4-yl (derived from mevalonic lactone), 2-methyl-2-adamantyl or 2-ethyl-2-adamantyl.
The groups described above will substitute hydrogen of the phenolic hydroxyl group or the carboxyl group.
The protecting group can be introduced into the alkaline-soluble resin having a phenolic hydroxyl group or a carboxyl group by a reaction for introducing the protecting group employing a known esterifying reaction. Alternatively, the resin may be obtained by copolymerization using an unsaturated compound having such group as a monomer
Preferred examples of the polymerization unit having a group unstable against acid include a polymerization unit represented by the following formula (II):
wherein R
3
represents an alkyl group having 1 to 4 carbon atoms, and R
4
represents an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 5 to 7 carbon atoms, or R
3
and R
4
may be combined to form a tetramethylene chain.
Further, examples of the polymerization unit having a group unstable against acid
Ichimura Kunihiro
Namba Katsuhiko
Okudaira Tsugio
Suetsugu Masumi
Uetani Yasunori
Baxter Janet
Sumitomo Chemical Company Limited
Thornton Yvette C.
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