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
2002-06-20
2004-10-26
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, C430S921000, C430S923000
Reexamination Certificate
active
06808862
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive photosensitive composition used in the production process of semiconductor devices, for example, IC, in the production of circuit substrates for liquid crystals or thermal heads, or in other photofabrication processes. More specifically, the present invention pertains to a positive photosensitive composition suitable for use a far ultraviolet ray of not more than 250 nm as a light source for exposure.
BACKGROUND OF THE INVENTION
A chemically amplified positive resist composition is a pattern formation material in which an acid is generated in the exposed area upon irradiation of radiation, for example, a far ultraviolet ray, and solubility in a developer between the exposed area and unexposed area is differentiated by a reaction using the acid as a catalyst, whereby a pattern is formed on a substrate.
Since the composition is mainly composed of a resin having as a basic skeleton, poly(hydroxystyrene) that has a small absorption in a region of 248 nm, a good pattern with high sensitivity and high resolution is formed, when a KrF excimer laser is used as a light source for exposure. Thus, the composition is superior to a conventional resist composition using a naphthoquinonediazide
ovolac resin.
When a light source having a shorter wavelength, e.g., an ArF excimer laser (193 nm) is used for exposure, on the other hand, since an aromatic group-containing compound essentially has a large absorption in a region of 193 nm, the above-described chemically amplified composition is still insufficient.
The use of poly(meth)acrylate as a polymer having a small absorption in a wavelength range of 193 nm is described in
J. Vac. Sci. Technol.,
B9, 3357(1991). The polymer has, however, a problem in that resistance to dry etching ordinarily performed in a semiconductor production process is low in comparison with conventional phenolic resins having an aromatic group.
A mixed acid generator of a specific sulfonium salt (an anion having from 1 to 15 carbon atoms) and a triarylsulfonium salt is described in JP-A-2000-292917 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), a mixed acid generator of a triphenylsulfonium salt of a perfluoroalkanesulfonic acid having from 4 to 8 carbon atoms and a 2-alkyl-2-adamantyl (meth)acrylate is described in JP-A-2000-275845, and a mixed acid generator of a specific sulfonium salt (an anion having from 1 to 8 carbon atoms) and a triphenylsulfonium salt or iodonium salt of a perfluoroalkanesulfonic acid having from 4 to 8 carbon atoms is described in EP 1041442A.
As increasing fine processing of semiconductor device, it has been desired more and more for a photoresist to have a low pitch dependency, specifically, to be capable of forming good patterns in both a dense portion and a sparse portion, in addition to improved sensitivity and resolution in lithography using a chemically amplified resist for far ultraviolet ray exposure. However, means for improving the pitch dependency of chemically amplified resist for far ultraviolet ray exposure has been scarcely disclosed. The addition of an orthoester compound to a chemically amplified resist composition for a KrF excimer laser for improving the pitch dependency is just described in JP-A-11-160876.
A resist composition containing a resin based on hydroxystyrene having a high hydrophilicity and a mixture of acid generators generating acids having acidities different from each other is described in JP-A-2000-241965. However, since the hydroxystyrene structure has an excessively high absorption to light of not more than 220 nm, e.g., an ArF excimer laser (193 nm), a problem of the formation of a pattern profile called taper arises, when such a resist composition is used for the formation of resist pattern.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a positive photosensitive composition that is excellent in sensitivity and resolution.
Another object of the present invention is to provide a positive photosensitive composition that exhibits a low pitch dependency as well as excellent sensitivity and resolution.
Other objects of the present invention will become apparent from the following description.
As a result of the intensive investigations, it has been found that the above-described objects can be accomplished by using compounds generating acids having specific structures in combination to complete the present invention.
Specifically, the present invention includes the following positive photosensitive compositions:
1. A positive photosensitive composition comprising (A1) a compound that generates an alkanesulfonic acid in which the &agr;-position is substituted with a fluorine atom upon irradiation of an actinic ray or radiation, (A2) an onium salt of an alkanesulfonic acid in which the &agr;-position is not substituted with a fluorine atom, and (B) a resin that has a monocyclic or polycyclic alicyclic hydrocarbon structure and is decomposed by the action of an acid to increase a solubility rate in an alkali developing solution.
2. The positive photosensitive composition as described in item (1) above, wherein the resin of component (B) contains a repeating unit having a lactone structure.
3. The positive photosensitive composition as described in item (1) or (2) above, wherein the compound of component (A1) is a sulfonium salt.
4. The positive photosensitive composition as described in any one of items (1) to (3) above, wherein the onium salt of component (A2) is a sulfonium salt, an iodonium salt or an ammonium salt.
DETAILED DESCRIPTION OF THE INVENTION
The positive photosensitive composition according to the present invention will be described in more detail below.
<<Component (A1)>>
Any compound that generates an alkanesulfonic acid in which the &agr;-position is substituted with a fluorine atom upon irradiation of an actinic ray or radiation (hereinafter, also referred to as an acid generator) can be used as the compound of component (A1) in the present invention.
The compound that generates an alkanesulfonic acid in which the &agr;-position is substituted with a fluorine atom includes an onium salt, e.g., a sulfonium salt or an iodonium salt, an oxymesulfonate compound, an imidosulfonate compound and o-nitrobenzylsulfonate compound.
Preferred examples thereof include a sulfonium salt, which is composed of an anion portion and a cation portion, represented by the following formula (A1):
In formula (A1), R
1
, R
2
and R
3
, which may be the same or different, each independently represent an organic residue. A number of carbon atom included in the organic residue represented by R
1
, R
2
or R
3
is ordinarily from 1 to 30, and preferably from 1 to 20.
Alternatively, two of R
1
, R
2
and R
3
may be combined with each other to form a ring, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amido bond or a carbonyl group. The group formed by combining two of R
1
, R
2
and R
3
includes an alkylene group (e.g., butylene or pentylene group).
Specific examples of the organic residue represented by R
1
, R
2
or R
3
include corresponding groups in Compounds (A1-1), (A1-2) and (A1-3) described below.
Z
−
represents a counter anion, specifically an alkanesulfonic acid anion in which the carbon atom at the &agr;-position is substituted with a fluorine atom and which is represented by R
F
SO
3
−
.
The R
F
, which represents the alkane portion of the alkanesulfonic acid, is not particularly limited and includes a straight chain, branched or cyclic alkyl group having from 1 to 20 carbon atoms, e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl, tetradecyl or hexadecyl group, and preferably a straight chain, branched or cyclic alkyl group having from 4 to 16 carbon atoms.
At least one fluorine atom should be present at the &agr;-position of the alkanesulfonic acid, and the alkanesulfonic acid may also have other fluorine atoms in other portions thereof.
Preferred examples of the R
F
include a fluorine-subs
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