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
2001-11-28
2003-11-18
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
C430S905000, C430S914000
Reexamination Certificate
active
06649322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positive resist composition and to a positive resist base material using the same.
2. Description of the Related Art
Lithographic processes requiring the definition in the vicinity of 0.25 &mgr;m and using a chemically amplified positive resist have been launched in practical applications. Separately, with an increasing demand on semiconductor devices having reduced sizes, next-generation processes requiring fine patterns of from 0.13 &mgr;m to 0.22 &mgr;m using KrF excimer laser have been developed.
One of such conventional chemically amplified resists comprises a copolymer of p-vinylphenol and tert-butyl methacrylate as a resin ingredient (Japanese Unexamined Patent Application Publication No. 5-113667). The tert-butyl group in the resin is known as a typical acid-decomposable dissolution-inhibiting group but is insufficient in etching resistance. In next-generation processes, definition should further be improved by reducing the thickness of a resist (to 0.5 &mgr;m or below) on an anti-reflection coating. However, the use of the tert-butyl group may further deteriorate dry-etching resistance in such a thinned resist film.
When a resist layer using the aforementioned resin is formed on an anti-reflection coating on a substrate, the anti-reflection coating prevents reflected light from the substrate, and an upper part of the resist layer is therefore overexposed as compared with the lower part thereof. In addition, the acid-decomposable dissolution-inhibiting group has weak hydrophobicity, and the resulting resist layer has an insufficient insolubilized surface layer. Accordingly, the top of the resulting patterned resist becomes round.
Additionally, this type of resins only has one acid-decomposable dissolution-inhibiting group in one molecule, and the resulting resist exhibits insufficient contrast between exposed portions and unexposed portions, has deteriorated definition and resist pattern profile and cannot be applied to further miniaturized semiconductor devices.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a chemically amplified positive resist composition that can be applied to a resist having a reduced thickness, is excellent in dry-etching resistance and definition and can yield a patterned resist with a good profile (sectional shape).
The present inventors have found that the above objects can be achieved by using a positive resist composition comprising (A) a compound which generates an acid upon irradiation with active light or radiant ray, and (B) a resin which exhibits increased solubility in an alkali by action of an acid and includes a copolymer comprising (b-1) 40% to 85% by mole of a unit having an alkali-soluble group, (b-2) 3% to 25% by mole of a unit having (i) an acid-decomposable dissolution-inhibiting group and (ii) a group which accelerates dry-etching resistance, and (b-3) 3% to 40% by mole of a unit having an acid-decomposable dissolution-inhibiting group other than the units (b-1) and (b-2). The positive resist composition may further include a tertiary aliphatic lower amine, or an carboxylic acid, an oxoacid of phosphorus or a derivative thereof according to necessity. The present invention provides, in another aspect, a positive resist base material including a substrate, an anti-reflection coating formed on the substrate and having a predetermined thickness, and a resist layer formed on the anti-reflection coating, including the positive resist composition and having a predetermined thickness.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Ingredient (A)
The ingredient (A) for use in the present invention is an “acid generator”, a compound which generates an acid upon irradiation with active light or radiant ray. The ingredient (A) is not specifically limited and can freely be selected from conventional acid generators such as iodonium salts, sulfonium salts, and other onium salts, oxime sulfonate compounds, bisalkyl-, biscycloalkyl- or bisaryl-sulfonyldiazomethanes, nitrobenzylsulfonates, iminosulfonates, and disulfones.
As the ingredient (A) for use in the present invention, an onium salt having a fluoroalkylsulfonate ion as an anion can advantageously be used. This type of onium salts generates an acid having higher strength and can sufficiently decompose the acid-decomposable dissolution-inhibiting group in the ingredient (B).
Cations constituting the onium salts include, for example, diphenyliodonium or triphenylsulfonium which may optionally have a substituent. Such substituents include methyl, ethyl, propyl, n-butyl, tert-butyl, and other lower alkyl groups; and methoxy, ethoxy, and other lower alkoxy groups.
Anions constituting the onium salts are fluoroalkylsufonate ions in which part or all of the hydrogen atoms of the alkyl moiety is fluorinated. The more carbon atoms the alkyl moiety has and the less the hydrogen atoms are fluorinated (the less the proportion of fluorine atoms in the alkyl moiety is), the less the strength as a sulfonic acid is. Accordingly, a fluoroalkylsulfonate ion, in which all the hydrogen atoms of an alkyl group having from 1 to 10 carbon atoms are fluorinated, is preferred.
Such onium salts are represented by following Formulae (I) and (II):
wherein R
1
, R
2
, R
3
, R
4
and R
5
are each independently a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, or an alkoxy group having 1 or 2 carbon atoms; and X
−
is a fluoroalkylsulfonate ion.
Examples of the onium salts include, but are not limited to, trifluoromethanesulfonate or nonafluorobutanesulfonate of diphenyliodonium, trifluoromethanesulfonate or nonafluorobutanesulfonate of bis(4-tert-butylphenyl)iodonium, trifluoromethanesulfonate or nonafluorobutanesulfonate of triphenylsulfonium, trifluoromethanesulfonate or nonafluorobutanesulfonate of tri(4-methylphenyl)sulfonium, trifluoromethanesulfonate or nonafluorobutanesulfonate of tri(4-methoxyphenyl)sulfonium, trifluoromethanesulfonate or nonafluorobutanesulfonate of dimethylphenylsulfonium, and trifluoromethanesulfonate or nonafluorobutanesulfonate of methylcyclohexyl(2-oxocyclohexyl)sulfonium. Each of these onium salts can be used alone or in combination.
The amount of the ingredient (A) is from 0.5 to 20 parts by weight, and preferably from 5 to 15 parts by weight, relative to 100 parts by weight of the ingredient (B). If the amount of the ingredient (A) is out of this range, the resulting resist may not satisfactorily be patterned and may not yield a uniform resist solution.
Ingredient (B)
The ingredient (B) for use in the present invention is a resin which exhibits increased solubility in an alkali by action of an acid and includes a copolymer comprising (b-1) 40% to 85% by mole of a unit having an alkali-soluble group, (b-2) 3% to 25% by mole of a unit having (i) an acid-decomposable dissolution-inhibiting group and (ii) a group which accelerates dry-etching resistance, and (b-3) 3% to 40% by mole of a unit having an acid-decomposable dissolution-inhibiting group and being other than the units (b-1) and (b-2). The ingredient (B) has a weight average molecular weight (Mw) of preferably from 2000 to 15000 and more preferably from 3000 to 11000, a number average molecular weight (Mn) of preferably from 1000 to 10000 and more preferably from 1500 to 7000 and a molecular weight distribution (Mw/Mn) of preferably from 1.2 to 1.8 and more preferably from 1.3 to 1.7.
The unit (b-1) having an alkali-soluble group may be any unit having, for example, a phenolic hydroxyl group or a carboxyl group. The unit (b-1) may further have another substituent such as a lower alkyl group, as long as the alkali-solubility is not deteriorated. Examples of the unit (b-1) include a hydroxystyrene unit and &agr;-methylhydroxystyrene unit. By comprising 40% to 85% by mole, and preferably from 60% to 80% by mole, of the unit (b-1), the ingredient (B) exhibits appropriate alkali-solubility after exposure and can yield a resist pattern exhibiting satisfactory etching resistance and havin
Kumon Satoshi
Yukawa Hiroto
Ashton Rosemary
Sughrue & Mion, PLLC
Tokyo Ohka Kogyo Co. Ltd.
LandOfFree
Positive resist composition and positive resist base... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Positive resist composition and positive resist base..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Positive resist composition and positive resist base... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3170386