Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-10-07
2002-05-07
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S089000, C526S347100, C525S210000, C525S216000, C525S219000, C525S221000, C525S338000, C430S270210
Reexamination Certificate
active
06384169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel polymer having at least one type of acid labile group, terminally modified, and optionally crosslinked within a molecule and/or between molecules with crosslinking groups having C—O—C linkages. It also relates to a resist composition comprising the polymer as the base resin and a patterning process using the resist composition. This resist composition provides a much improved alkali dissolution contrast before and after exposure, high sensitivity, and high resolution, and in particular, is well reproducible as a micropatterning material for VLSI fabrication.
2. Prior Art
Deep-ultraviolet lithography, one of a number of recent efforts that are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, is thought to hold particular promise as the next generation in microfabrication technology. Deep-UV lithography is capable of achieving a minimum feature size of 0.5 &mgr;m or less and, when a resist having low light absorption is used, can form patterns with sidewalls that are nearly perpendicular to the substrate.
Recently developed acid-catalyzed chemically amplified positive resists, such as those described in JP-B 27660/1990, JP-A 27829/1988, U.S. Pat. No. 4,491,628 and U.S. Pat. No. 5,310,619, utilize a high-intensity KrF excimer laser as the deep-UV light source. These resists, with their excellent properties such as high sensitivity, high resolution, and good dry etching resistance, are especially promising for deep-UV lithography.
Such chemically amplified positive resists include two-component systems comprising a base resin and a photoacid generator, and three-component systems comprising a base resin, a photoacid generator, and a dissolution regulator having acid labile groups.
For example, JP-A 115440/1987 describes a resist comprising poly-4-tert-butoxystyrene and a photoacid generator, and JP-A 223858/1991 describes a similar two-component resist comprising a resin bearing tert-butoxy groups within the molecule, in combination with a photoacid generator. JP-A 211258/1992 describes a two-component resist which is comprised of polyhydroxystyrene bearing methyl, isopropyl, tert-butyl, tetrahydropyranyl, and trimethylsilyl groups, together with a photoacid generator.
JP-A 100488/1994 discloses a resist comprised of a polydihydroxystyrene derivative, such as poly[3,4-bis(2-tetrahydropyranyloxy)styrene], poly[3,4-bis(tert-butoxy-carbonyloxy)styrene] or poly[3,5-bis(2-tetrahydropyranyloxy)styrene], and a photoacid generator.
However, when the base resin in these resists bears acid labile groups on side chains and these acid labile groups are groups such as tert-butyl and tert-butoxycarbonyl which are cleaved by strong acids, the resin reacts with air-borne basic compounds and loses some of its activity, as a result of which cleavage of the acid labile groups arises less readily and the resist pattern tends to take on a T-top profile. By contrast, alkoxyalkyl groups such as ethoxyethyl are cleaved by weak acids, and so are little affected by air-borne basic compounds. Yet, their use also has its drawbacks, such as considerable narrowing of the pattern configuration as the time interval between exposure and heat treatment increases. Moreover, the presence of bulky groups on the side chains lowers the thermal stability of the resin, making it impossible to achieve a satisfactory sensitivity and resolution. These problems have hitherto prevented the practical implementation of either approach, and workable solutions have been sought.
The polymers described in JP-A 305025/1996 represent an attempt to resolve the foregoing problems, but characteristics of the production process render difficult the design of substituent ratios for acid labile groups and crosslinking groups. An additional shortcoming is that the production of these compounds results in the incidental formation of the crosslinking groups mentioned in JP-A 253534/1996. That is, in the design of resist compositions, polymers having various alkali dissolution rates are required, depending on the types and amounts of photoacid generators and additives selected, in addition to which the production of these polymers must be a reproducible process. However, the production methods described in the above prior-art references are subject to inherent limitations in the selection of acid labile groups and crosslinking groups, and in their substituent ratios.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a novel and improved polymer which can be used as the base resin to formulate a chemically amplified positive working resist composition which is superior to prior-art resists in sensitivity, resolution, exposure latitude, process flexibility and reproducibility, and which forms a resist pattern having excellent plasma etching resistance and outstanding thermal stability. Another object of the invention is to provide a chemically amplified positive working resist composition comprising the polymer and a patterning process using the resist composition.
We have found that a novel polymer bearing at least one type of acid labile group, modified at terminals, and optionally crosslinked within a molecule and/or between molecules with a crosslinking group having a C—O—C linkage can be produced by a method to be described later and is useful as a base resin. By blending this novel polymer as a base resin with a photoacid generator and optionally, a dissolution regulator and a basic compound, there is obtained a chemically amplified positive resist composition which is improved in that the dissolution contrast of a resist film is increased, especially a dissolution rate after exposure is increased. By further blending an aromatic compound having a group ≡C—COOH in a molecule, there is obtained a chemically amplified positive resist composition which is improved in that the resist is improved in PED stability and edge roughness on a nitride film substrate is improved. By further blending an acetylene alcohol derivative, the resist composition is improved in coating and storage stability, forms resists having high resolution, improved latitude of exposure, and improved process flexibility, and is well suited for practical use and advantageously used in precise microfabrication, especially in VLSI manufacture.
In a first aspect, the invention provides a styrene polymer represented by the following general formula (1), terminated with P, and having a weight average molecular weight of 1,000 to 500,000.
Herein, R is hydroxyl or OR
3
groups, at least one of R groups being hydroxyl, R
1
is hydrogen or methyl, R
2
is a normal, branched or cyclic alkyl group of 1 to 30 carbon atoms, R
3
is an acid labile group, letter x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, k is 0 or a positive integer, m is 0 or a positive integer, n is a positive integer, satisfying k+m+n≦5, p and q are positive numbers satisfying 0<q≦0.8 and p+q=1, with the proviso that the R
3
groups may be the same or different when n is at least 2, &Dgr; is such a number that the polymer may have a weight average molecular weight of 1,000 to 500,000, P is hydrogen, normal, branched or cyclic alkyl or alkenyl groups of 1 to 30 carbon atoms, aromatic hydrocarbon groups of 6 to 50 carbon atoms, carboxyl, hydroxyl, or groups of the following general formula (2), (3) or (4), all the terminal groups are not hydrogen at the same time,
—R
4
&Parenopenst;OH)
r
(3)
—R
4
—(OR
5a
)
r
(4)
wherein R
4
is (r+1)-valence aliphatic hydrocarbon groups or alicyclic saturated hydrocarbon groups of 1 to 30 carbon atoms, or aromatic hydrocarbon groups of 6 to 50 carbon atoms, R
5
is normal, branched or cyclic alkyl groups of 1 to 30 carbon atoms, aromatic hydrocarbon groups of 6 to 50 carbon atoms, alkoxy groups of 1 to 30 carbon atoms, or hydroxyl, R
5a
is normal, b
Junji Shimada
Shigehiro Nagura
Takanobu Takeda
Watanabe Osamu
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
Wu David W.
Zalukaeva Tanya
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