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
2003-02-25
2004-11-02
Schilling, Richard L. (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
C430S907000, C430S914000
Reexamination Certificate
active
06811947
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive resist composition suitable for use in a microlithography process, for example, the production of VLSI and high capacity microtips, and in other photofabrication processes. More particularly, the present invention relates to a positive resist composition capable of forming a highly precise pattern using a vacuum ultraviolet ray of not more than 160 nm.
BACKGROUND OF THE INVENTION
The degree of integration of integrated circuits has recently become much higher, and the processing of ultra-fine patterns having a line width of a quarter micron or below is required in the production of semiconductor substrate, for example, VSLI. As one means for the formation of fine pattern, it is known to make an exposure light source for use in the production of resist pattern shorter.
For instance, in the production of semiconductor device having the degree of integration up to 64 Mbits, an i-line (365 nm) of high pressure mercury lamp has been employed as the light source. As a positive resist corresponding to the light source, a large number of compositions containing a novolac resin and a naphthoquinone diazide compound as a photosensitive substance have been developed. These compositions have achieved full success in the processing of line width up to about 0.3 &mgr;m. Also, in the production of semiconductor device having the degree of integration of 256 Mbits or more, a KrF excimer laser beam (248 nm) is employed as the light source in place of the i-line.
In recent years, for the purpose of the production of semiconductor device having the degree of integration of 1 Gbit or more, as a light source having shorter wavelength, the use of an ArF excimer laser beam (193 nm) and further, the use of an F2 excimer laser beam (157 nm) have been investigated in order to form a pattern of not more than 0.1 &mgr;m.
In response to such a trend of using light source having a shorter wavelength, constituents of the resist materials and structure of compounds used for the constituents have been greatly changed.
As a resist composition for exposure using the KrF excimer laser beam, a composition in which a resin including a basic skeleton of poly (hydroxystyrene) that has a small absorption in the region of around 248 nm and being protected by an acid-decomposable group is used as the main component and a compound that generates an acid upon irradiation of a far ultraviolet ray (a photo-acid generator) is used in combination, that is, a so-called chemical amplification resist has been developed.
Also, as a resist composition for exposure using the ArF excimer laser beam (193 nm), a chemical amplification resist using an acid-decomposable resin in which an alicyclic structure that does not have an absorption in the region of around 193 nm is introduced into the main chain or side chain thereof has been developed.
It has been found in case of using an F2 excimer laser beam (157 nm), however, that since the above-described alicyclic group-containing resin still has a large absorption in the region of around 157 nm, it is insufficient for obtaining the desired pattern of not more than 0.1 &mgr;m. In such circumstances, it is reported that a resin having a fluorine atom (a perfluoro structure) introduced therein has sufficient transparency in the region of around 157 nm in
Proc. SPIE.,
Vol. 3678, page 13 (1999). Structures of effective fluorine resins are also proposed, for example, in
Proc. SPIE.,
Vol. 3999, page 330 (2000), ibid., page 357 (2000), ibid., page 365 (2000) and WO 00/17712. Thus, investigations of resist composition including the fluorine resin have been made.
However, the resist composition for exposure using an F2 excimer laser beam containing such a fluorine resin has problems, for example, line edge roughness and developing time dependency. Therefore, it is desired to resolve these problems.
The term “line edge roughness” used herein means a phenomenon wherein an edge between a line pattern of resist and a surface of substrate irregularly fluctuates in the direction vertical to the line due to the characteristics of resist. When the pattern is observed from just above, the edge is uneven (approximately from several nm to several dozen nm). Since the unevenness is transferred to the substrate in an etching step, the large unevenness causes a defect in electric properties thereby resulting in yield reduction.
The term “developing time dependency” used herein means a degree of change in pattern size depending on the fluctuation of developing time. When the developing time dependency is large, the pattern size uniformity in a wafer is degraded and control of the developing process becomes difficult.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a positive resist composition suitable for using an exposure light source having a wavelength of not more than 160 nm, particularly an F2 excimer laser beam (157 nm).
Another object of the present invention is to provide a positive resist composition, which exhibits sufficient transmittancy in case of using an exposure light source of 157 nm and has small line edge roughness and developing time dependency.
Other objects of the present invention will become apparent from the following description.
As a result of the intensive investigations on the above-described characteristics of positive resist composition, it has been found that the objects of the present invention can be accomplished by using the specific composition described below to complete the present invention.
Specifically, the present invention includes the following configurations:
(1) A positive resist composition comprising (A) a resin, which is decomposed by the action of an acid to increase solubility in an alkali developing solution, having a repeating unit represented by formula (Y) shown below, (B) a compound capable of generating an acid upon irradiation of an actinic ray or radiation, and (C) a solvent.
In formula (Y), R
1
to R
6
, which may be the same or different, each represent a hydrogen atom, a fluorine atom, an alkyl group or a substituted alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, provided that at least one of R
1
to R
6
is a fluorine atom.
L represents a hydrogen atom or a group decomposable upon the action of an acid.
n represents 1 or 2. When n is 2, two R
1
's to R
6
's and L's may be the same or different from each other.
A represents a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a cyano group or a trifluoromethyl group.
The structural formula (YA) shown below represents a benzene ring structure hydrogenated at least partially.
DETAILED DESCRIPTION OF THE INVENTION
The present invention also includes the following preferred embodiments.
(2) The positive resist composition as described in item (1) above, wherein the compound capable of generating an acid upon irradiation of an actinic ray or radiation of (B) is (B1) a compound capable of generating an organic sulfonic acid upon irradiation of an actinic ray or radiation.
(3) The positive resist composition as described in item (2) above, which further comprises (B2) a compound capable of being decomposed upon irradiation of an actinic ray or radiation to generate a carboxylic acid.
Now, the compounds for use in the positive resist composition of the present invention are described in detail below.
[1] Resin (Component (A))
In the positive resist composition of the present invention, a resin, which is decomposed by the action of an acid to increase solubility in an alkali developing solution, having a repeating unit represented by formula (Y) shown below is used as a resin of Component (A).
In formula (Y), R
1
to R
6
, which may be the same or different, each represent a hydrogen atom, a fluorine atom, an alkyl group or an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, provided that at least one of R
1
to R
6
is a fluorine atom. L represents a hydrogen atom or a group decomposabl
Kanna Shinichi
Mizutani Kazuyoshi
Sasaki Tomoya
Fuji Photo Film Co. , Ltd.
Schilling Richard L.
Sughrue & Mion, PLLC
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