Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
1999-11-02
2001-02-13
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S191000, C430S192000, C430S193000
Reexamination Certificate
active
06187500
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-sensitivity and high-definition positive photoresist composition which is especially suitable for lithography using i-ray, and to a multilayer resist material using the composition.
2. Description of the Related Art
Positive photoresist compositions each containing an alkali-soluble resin and a quinonediazide ester have satisfactory definition, sensitivity, and etching resistance, and therefore have been applied in practice to the production of semiconductor devices and liquid crystal display devices.
With increasing demands for minitualized and high-capacity semiconductor integrated circuits (ICs), there is a strong felt need to form resist patterns in a design rule of 0.35 &mgr;m or below, more particularly 0.30 &mgr;m or below.
Even in such an ultrafine design rule, there are demands for photoresist compositions which can form resist patterns satisfactory in sensitivity, exposure margin, and focal depth range properties and having a good shape.
Such a resist pattern of 0.35 &mgr;m or below, in particular of 0.30 &mgr;m or below in line width, has been believed to be hardly formed by photolithography using i-ray (365 nm) as a light source without deteriorating the above properties. Photolithography using Kr-F excimer laser or Ar-F excimer layer which is shorter in wavelength than i-ray has therefore been proposed for the formation of such an ultrafine resist pattern.
Accordingly, a variety of photoresist compositions for excimer laser have been proposed.
The photolithography technique using excimer layer requires, however, expensive lithography systems and high costs in change of manufacturing lines, and the photoresist compositions for excimer laser are very fragile and need to be treated carefully.
Under these circumstances, demands have been made to provide means for sustaining the lithography technique using i-ray and to provide ultra-high definition photoresist compositions which can form an ultrafine resist pattern of 0.35 &mgr;m or below, particularly of 0.30 &mgr;m or below, in lithography using i-ray without deteriorating the definition, sectional shape or profile, focal depth range, and other properties.
A possible solution to the above demands is to improve alkali-soluble novolak resins to be used.
For example, Japanese Patent Laid-Open Nos. 6-202321 and 6-348007 disclose an alkali-soluble novolak resin containing units derived from m-cresol, p-cresol and 2,5-xylenol as constitutive units. The novolak resin is expected to prevent scum (resist residue after development) formation and to yield a positive photoresist composition satisfactory in definition, sectional profile, focal depth range and other properties. A photoresist composition using the novolak resin is, however, still insufficient in sensitivity, and if its sensitivity is to be increased by, for example, decreasing the molecular weight or increasing the proportion of m-cresol, the other properties, especially definition, are markedly deteriorated.
Japanese Unexamined Patent Publication No. 5-273757 discloses an alkali-soluble novolak resin obtained by condensing a mixture and formaldehyde, which mixture is composed of 30% to 98% by mole of m-cresol, 1% to 40% by mole of 3,5-dimethylphenol, and 1% to 10% by mole of polyhydroxyphenol represented by the following formula:
wherein R is a hydrogen or a lower alkyl group having 1 to 5 carbon atoms, and n denotes 1 to 3. The use of this novolak resin is expected to give a high-sensitivity positive photoresist composition satisfactory in heat resistance. Such a positive photoresist composition using the novolak resin invites, however, a large amount of scum, and is insufficient in definition, sectional profile, focal depth range and other properties, even though being satisfactory in sensitivity and heat resistance.
Furthermore, Japanese Patent Laid-Open No. 62-227144 discloses an alkali-soluble novolak resin obtained by condensation of phenols and formaldehyde, which phenols contain 6% to 94% by mole of m-cresol, and 94% to 6% of a compound represented by the following formula (except for m-cresol):
wherein X is —CH
3
, —C
2
H
5
, —C(CH
3
)
3
, —CO
2
CH
3
or —CO
2
C
2
H
5
, 3≧n≧1, and 3≧m≧1. The use of this novolak resin is expected to give a positive photoresist composition satisfactory in definition, sensitivity, and heat resistance. A positive photoresist composition using the aforementioned novolak resin is, however, inferior in sensitivity and definition, invites a large amount of scum, and is inferior in sectional profile, focal depth range and other properties, in the formation of an ultrafine resist pattern of 0.35 &mgr;m or below.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a high-definition positive photoresist composition which inhibits the formation of scum, is satisfactory in sensitivity, sectional profile, focal depth range and other properties even in a process for the formation of a resist pattern of 0.35 &mgr;m or below, especially of an ultrafine pattern of 0.30 &mgr;m or below by photolithography using i-ray.
After intensive investigations, the present inventors have achieved a solution to the above problems of conventional equivalents.
To be more specific, the invention provides, in an aspect, a positive photoresist composition including: (A) an alkali-soluble novolak resin, and (B) a naphthoquinonediazide ester, the alkali-soluble novolak resin is obtained synthetically by condensation of phenol compounds and an aldehyde or ketone, and the phenol compounds are composed of 1% to 20% by mole of a phenol compound represented by the following formula (I):
wherein R
1
is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, 30% to 95% by mole of m-cresol, and 2% to 50% by mole of 2,5-xylenol.
In the above photoresist composition, the phenol compound represented by the formula (I) may preferably be a resorcinol compound represented by the following formula (II):
wherein R
2
is an alkyl group having 1 to 5 carbon atoms.
The phenol compound represented by the formula (I) may also be a hydroquinone compound represented by the following formula (III):
wherein R
2
is an alkyl group having 1 to 5 carbon atoms.
More preferably, the phenol compound represented by the formula (I) may be hydroquinone.
Alternatively, the phenol compound represented by the formula (I) may be at least one compound selected from the group consisting of 2-methylresorcinol, 5-methylresorcinol and 2-methylhydroquinone.
The aforementioned alkali-soluble novolak resin may further include 1% to 30% by mole of at least one phenol compound selected from the group consisting of p-cresol, 3,4-xylenol, 3,5-xylenol and dimethylol derivatives of these compounds, as the phenol compounds.
In the positive photoresist composition, 1% to 25% by mole of a phenol compound represented by the following formula (IV):
wherein a denotes 0 or 1, is preferably used instead of 2,5-xylenol.
Further, the present invention provides a positive photoresist composition comprising:
(A) an alkali-soluble novolak resin, and
(B) a naphthoquinonediazide ester,
characterized in that the alkali-soluble novolak resin comprises:
1 to 20% of a unit represented by the following formula
wherein R
1
is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms,
30 to 95% of a unit represented by the following formula,
and 2 to 50% of a unit represented by the following formula.
Furthermore, the present invention provides a positive photoresist composition comprising:
(A) an alkali-soluble novolak resin, and
(B) a naphthoquinonediazide ester,
characterized in that the alkali-soluble novolak resin comprises:
1 to 20% of a unit represented by the following formula
wherein R
1
is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms,
30 to 95% of a unit represented by the following formula,
and 1 to 25% of a unit represented by the following formula.
Still further, the present invention provides the above composition, wherein the
Doi Kousuke
Hirata Atsuko
Kohara Hidekatsu
Miyagi Ken
Nakayama Toshimasa
Chu John S.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tokyo Ohka Kogyo Co. Ltd.
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