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
2001-11-09
2004-02-10
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, C430S271100
Reexamination Certificate
active
06689535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition for forming an anti-reflective coating which is provided onto a substrate and is, in turn, overlaid with a photoresist layer in the field of photolithography, a multilayer photoresist material using the same, and a method for forming a pattern. More particularly, the present invention relates to a bottom layer anti-reflective coating composition which is capable of forming a photoresist pattern having a rectangular profile without causing any undesirable phenomena, such as footing occurred at its bottom, even when forming a hyperfine photoresist pattern using a short-wavelength light source of from vacuum ultraviolet radiation to extreme-ultraviolet radiation typified by excimer laser beams, a multilayer photoresist material using the composition, and a method for forming a pattern.
2. Description of Related Art
In general, the fabrication of semiconductor devices utilizing photolithography involves providing a bottom layer anti-reflective coating or film between a substrate and a photoresist layer (“BARC method”). This is achieved to prevent, when patterning, standing waves resulting from the reflection of exposure light at the substrate from causing notching (local deformation), etc.
Recent advances in microlithography of semiconductor integrated circuits bearing finer patterns led to the trend toward the irradiation of rays of shorter wavelengths, and excimer laser beams, such as KrF, ArF and F
2
have come into use. A variety of three-component-type compositions have been investigated as the antireflective film-forming composition, where the excimer laser beams are used as light sources for exposure. The principal components of the composition are a resin for forming a coat (base resin), a light-absorptive component for absorbing reflected light, and a crosslinking agent for thermally crosslinking these components. For example, there have been proposed photolithography undercoating materials each containing: a crosslinking agent substituted by a hydroxyalkyl or alkoxyalkyl group; a benzophenone-, diphenylsulfone-, or sulfoxide-type dye; and an acrylic resin (Japanese Patent Application Laid-Open Nos. 8-87115, 9-292715, and 10-228113, etc.).
Furthermore, in recent years, it has been proposed to provide the coat-forming resin with light-absorptive by introducing a light-absorptive substituent(s) into its molecular structure. Examples of such resins that are obtainable by such technique include: an anti-reflective coating composition composed of a binder resin containing a quinolinyl group, a quinolinyl derivative group having a cyclic substituent with nitrogen, oxygen, or sulfur as a hetero atom, a phenanthrenyl group, an acridinyl group, or an alkyleneanthryl group, and a crosslinking agent constituted of glycoluryl and the like (Japanese Patent Application Laid-Open No. 10-204328); and an anti-reflective coating composition the principal constituents of which are a resin obtained by polymerizing an epoxy resin with a dye substituted by a group having an anthracene or naphthalene ring and a crosslinking agent such as a melamine resin, a urea resin, a benzoguanamine resin, and a glycoluryl resin (WO 97/07145).
In case of a pattern with a conventional fineness, adverse effects due to standing waves can be inhibited through the use of such conventional undercoating material or coating composition described above, leading to the formation of a photoresist pattern having an improved profile. However, since the formation of finer patterns requires further improvement in processing precision, it is hard to provide fully satisfactory results. In fact, the formation of a finer pattern with a line width of not more than 0.22 &mgr;m using said conventional undercoating material or coating composition, and a KrF excimer laser beam (wavelength: 248 nm) as a light source for exposure resulted in the occurrence of footing at its bottom or T-topping, and consequently failed in providing a photoresist pattern having a rectangular cross-section to the substrate. Poor patterning may lead to degradation in resolution.
Therefore, there has arisen a pressing need to develop such an anti-reflective coating as to realize the formation of a photoresist pattern having a rectangular cross-sectional profile in relation to the substrate even when forming a hyperfine pattern using a short-wavelength ray like KrF, ArF, or F
2
laser beam as a light source.
SUMMARY OF THE INVENTION
The present invention was accomplished under such circumstances as was described above.
An object, therefore, of the present invention is to provide an anti-reflective coating composition which realizes the formation of a photoresist pattern having a rectangular cross-sectional profile in relation to the substrate without causing footing or T-topping at its bottom even when an excimer laser beam or the like is employed as a light source for achieving increased fineness of patterning of about 0.20-0.22 &mgr;m in width.
Another object of the invention is to provide a multilayer photoresist material using the anti-reflective coating composition.
Still another object of the invention is to provide a method for forming a pattern.
For achieving the objects described above, the present invention provides an anti-reflective coating composition comprising: a crosslinking agent which is at least one compound selected from nitrogen-containing compounds having an amino group(s) and/or an imino group(s) at least two hydrogen atoms of which are substituted by a hydroxyalkyl group(s) and/or an alkoxyalkyl group(s); and an acidic compound. In this composition, the crosslinking agent is such that the proportion of its low-molecular-weight component not larger than a trimer is adjusted so as to be 15 wt % or less.
Moreover, the present invention provides a multilayer photoresist material produced by forming an anti-reflective coating onto a substrate using the above-described anti-reflective coating composition and providing a photoresist layer thereon.
Furthermore, the present invention provides a method for forming a pattern which comprises forming an anti-reflective coating from the anti-reflective coating composition described above onto a substrate, providing a photoresist layer thereon, selectively exposing the photoresist layer to light, and developing the photoresist layer to give a photoresist pattern.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in further detail.
The crosslinking agent employed according to the present invention is selected from nitrogen-containing compounds having an amino group(s) and/or an imino group(s) at least two hydrogen atoms of which are substituted by a hydroxyalkyl group(s) and/or an alkoxyalkyl group(s), and that the proportion of its low-molecular-weight component not larger than a trimer has been adjusted so as to be 15 wt % or less.
Exemplified such nitrogen-containing compound include melamine-, urea-, guanamine-, acetoguanamine-, benzoguanamine-, and succinylamide compounds in which the hydrogen atoms of an amino group(s) are substituted by methylol groups, alkoxymethyl groups, or methylol and alkoxymethyl groups; and glycoluryl or ethylene urea compounds in which the hydrogen atom of an imino group is substituted.
These nitrogen-containing compounds are obtainable by, for example, allowing a melamine compound, a urea compound, a guanamine compound, an acetoguanamine compound, a benzoguanamine compound, a succinylamide compound, a glycoluryl compound, or an ethylene urea compound to react with formalin in boiling water for methylolation, or by further alkoxylating the obtained reaction product through the reaction with a lower alcohol concrete examples of which are methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol, etc.
Of these nitrogen-containing compounds, preferred ones are benzoguanamine-, guanamine-, melamine-, and urea compounds in which at least two hydrogen atoms of the amino group(s) have been substituted by methylol groups,
Iguchi Etsuko
Tanaka Takeshi
Wakiya Kazumasa
Ashton Rosemary
Tokyo Ohka Kogyo Co., LTD
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