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
2001-08-14
2003-11-04
Baxter, Janet (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, C430S910000, C430S914000, C430S326000, C430S327000, C430S328000, C430S330000, C430S331000, C526S313000, C526S328500
Reexamination Certificate
active
06641975
ABSTRACT:
This invention relates to a resist composition, typically chemically amplified positive resist composition, comprising a polymer in the form of a ternary copolymer of hydroxystyrene, tertiary alkyl (meth)acrylate and substitutable phenoxyalkyl (meth)acrylate as a base resin and a patterning process using the resist composition.
BACKGROUND OF THE INVENTION
While a number of recent efforts are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography 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 chemical amplification positive resists, such as those described in JP-B 2-27660, JP-A 63-27829, U.S. Pat. Nos. 4,491,628 and 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 inhibitor having acid labile groups.
For example, JP-A 62-115440 describes a resist material comprising poly-4-tert-butoxystyrene and a photoacid generator, and JP-A 3-223858 describes a similar two-component resist material comprising a resin bearing tert-butoxy groups within the molecule, in combination with a photoacid generator. JP-A 4-211258 describes a two-component resist material which is comprised of polyhydroxystyrene bearing methyl, isopropyl, tert-butyl, tetrahydropyranyl, and trimethylsilyl groups, together with a photoacid generator.
JP-A 6-100488 discloses a resist material 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-tetrahydro-pyranyloxy)styrene], and a photoacid generator.
The base resins in these resist materials bear acid labile groups on side chains. When these acid labile groups are groups such as tert-butyl and tert-butoxycarbonyl which are cleaved by strong acids, the resist pattern tends to take on a T-top profile. By contrast, when the acid labile groups are alkoxyalkyl groups such as ethoxyethyl which are cleaved by weak acids, the corresponding resins have the drawback that the pattern configuration is considerably narrowed as the time interval between exposure and heat treatment increases. Moreover, the presence of bulky groups on the side chains lowers the heat resistance of the resin and leads to an unsatisfactory sensitivity and resolution. These problems have hitherto prevented the practical implementation of either approach, and workable solutions have been sought.
To provide higher transparency and firm adhesion to substrates and to improve footing on substrates and etching resistance, JP-A 3-275149 and 6-289608 propose a resist material using a copolymer of hydroxystyrene and tertiary alkyl (meth)acrylate. The resist material of this type suffers from poor heat resistance and an indefinite pattern profile after exposure and is not satisfactory in resolution as well. Likewise, JP-A 8-101509 discloses a resist material using a ternary copolymer of hydroxystyrene, tertiary alkyl (meth)acrylate and substitutable alkyl (meth)acrylate. Merely introducing a common substitutable alkyl (meth)acrylate as the third component fails to overcome the above-mentioned problems and rather detracts from resolution. A copolymer having a phenoxyethyl group introduced into the ester group of (meth)acrylic acid is known from JP-A 2000-89460 as achieving an improvement in the run length of lithographic printing plates, but its application to chemically amplified resist materials has not been attempted.
SUMMARY OF THE INVENTION
An object of the invention is to provide a positive resist composition, especially chemically amplified positive resist composition, which is superior to prior art positive resist compositions in sensitivity, resolution, exposure latitude and process flexibility, and has a satisfactory pattern profile after exposure and high etching resistance.
It has been found that a polymer having recurring units of the following general formula (1) or (2) and having a weight average molecular weight of 1,000 to 500,000 is an effective base resin in a positive resist composition, especially chemically amplified positive resist composition. The chemically amplified positive resist composition containing a photoacid generator and an organic solvent as well as the polymer has many advantages including an increased dissolution contrast of a resist film, high resolution, improved latitude of exposure, improved process flexibility, a good pattern profile after exposure, and high etching resistance. The composition is thus suited for practical use and advantageously used in precise microfabrication, especially in VLSI manufacture.
Herein R
1
, R
2
and R
3
each are hydrogen or methyl, Z is a straight, branched or cyclic alkylene group of 2 to 10 carbon atoms, R
4
is hydrogen or a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms, which may contain an oxygen atom, R
5
is a tertiary alkyl group of 5 to 20 carbon atoms, p, q and r are positive numbers satisfying p+q+r=1.
Herein R
6
, R
7
and R
8
each are hydrogen or methyl, R
9
is a tertiary alkyl group of 5 to 20 carbon atoms, s, t and u are positive numbers satisfying s+t+u=1.
The polymer of formula (1) or (2) is a ternary copolymer of a hydroxystyrene, a tertiary alkyl (meth)acrylate and a substitutable phenoxyalkyl (meth)acrylate. When the polymer is formulated as a base resin in a resist composition along with a photoacid generator, the substitutable phenoxyalkyl (meth)acrylate introduced as the third component of the copolymer makes it possible to control the diffusion rate of the photoacid generator. As a consequence, the composition has a high resolution, forms an improved pattern profile after exposure, and exhibits high etching resistance.
Undesirably, a resist composition having formulated therein a binary copolymer of a hydroxystyrene and a tertiary alkyl (meth)acrylate forms a degraded pattern profile after exposure, is unsatisfactory in resolution and etching resistance, and leaves footings on the pattern.
In contrast, a chemically amplified positive resist composition having formulated therein the ternary copolymer of formula (1) or (2) as a base resin has substantially overcome the problems including a degraded pattern profile after exposure, the lack of heat resistance, partial pattern collapse and footings, and as a result, has a high sensitivity, high resolution, etching resistance and process flexibility.
Accordingly, the present invention, in a first aspect, provides a resist composition comprising a polymer having recurring units of the general formula (1) or (2) and having a weight average molecular weight of 1,000 to 500,000.
In a second aspect, the invention provides a chemically amplified positive resist composition comprising (A) an organic solvent, (B) the polymer of formula (1) or (2) as a base resin, and (C) a photoacid generator; or (A) an organic solvent, (B) the polymer of formula (1) or (2) as a base resin, (C) a photoacid generator, and (D) a dissolution regulator; or (A) an organic solvent, (B) the polymer of formula (1) or (2) as a base resin, (C) a photoacid generator, (D) a dissolution regulator, and (E) a basic compound.
In a third aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition onto a substrate to form a coating; heat treating the
Hirahara Kazuhiro
Kusaki Wataru
Maeda Kazunori
Nagura Shigehiro
Takeda Takanobu
Lee Sin J.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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