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
2000-11-13
2003-01-28
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
C430S281100, C430S905000, C430S909000, C430S910000, C430S914000, C430S326000, C430S327000, C430S330000, C430S311000
Reexamination Certificate
active
06511785
ABSTRACT:
TECHNICAL FIELD
This invention relates to a chemically amplified positive resist composition for forming a contact hole pattern by the thermal flow process. While a method for forming a contact hole pattern using a chemically amplified positive resist composition comprising a polymer as the base resin involves the thermal flow step of heat treating the contact hole pattern for further reducing the size of contact holes, the invention relates to the resist composition to which a compound having functional groups capable of crosslinking with the polymer is added so that the size reduction by thermal flow becomes easy to control. The invention also relates to a method for forming a microsize contact hole pattern in the manufacture of VLSIs.
BACKGROUND ART
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 0.3 &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 2-27660, JP-A 63-27829, U.S. Pat. Nos. 4,491,628 and 5,310,619, utilize a high-intensity KrF or ArF 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 resist compositions 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 62-115440 describes a resist composition comprising poly-4-tert-butoxystyrene and a photoacid generator, and JP-A 3-223858 describes a similar two-component resist composition 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 composition 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 composition comprising a polydihydroxystyrene derivative, such as poly[3,4-bis(2-tetrahydropyranyloxy)styrene], poly[3,4-bis(tert-butoxycarbonyloxy)styrene] or poly[3,5-bis(2-tetrahydropyranyloxy)styrene], and a photoacid generator.
Improvement and development efforts have been continuously made on the base resin in resist compositions of this type. JP-A 10-207066 discloses a resist composition comprising a base resin which is crosslinked with crosslinking groups having C—O—C linkages and a photoacid generator wherein the crosslinking groups are eliminated under the action of acid generated from the photoacid generator upon exposure, achieving a high contrast and high resolution.
Even when any base resin designed to enhance the resolving power is used in such chemically amplified positive resist compositions, it is yet difficult to reach a contact hole size of 0.20 &mgr;m or less. There are available no resist compositions for forming a contact hole pattern satisfying the requirement of LSI devices of the next generation.
On the other hand, the known technology of forming a contact hole size of 0.20 &mgr;m or less is to heat treat a contact hole pattern for causing the resist film to flow and reducing the contact hole size. This technology is known as thermal flow process. The use of the thermal flow process enables formation of a miniature contact hole size as fine as 0.10 &mgr;m or 0.15 &mgr;m.
In forming microsize contact holes by the thermal flow process, however, it is very difficult to control the heat treating temperature so as to provide a shrinkage matching with the desired contact hole size. That is, the thermal flow process has the drawback that even a slight variation of heating temperature brings about a substantial variation of contact hole size.
Referring to
FIG. 1
, there is illustrated in cross section a resist film
2
on a substrate
1
, a contact hole
3
being formed through the resist film
2
. The contact hole having undergone the thermal flow process has a profile as shown in
FIG. 1
, that is, a cross-sectional profile bowed at corners. The thermal flow process also has the problem that the profile of a contact hole is deteriorated.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved chemical amplification type, positive working resist composition which has controllable process adaptability relative to the heat treating temperature when a microsize contact hole pattern is conventionally formed by the thermal flow process, and thus s has satisfactory practical utility. Another object is to provide a novel and improved method for forming a contact hole pattern.
It has been fount that when a contact hole pattern is formed by the thermal flow process using a chemically amplified positive resist composition comprising a compound containing at least two functional groups of the general formulas (1)-a to (1)-c in a molecule, the overall method is improved in process control and thus practically acceptable.
Herein R
1
to R
4
are hydrogen or straight, branched or cyclic alkyl groups of 1 to 12 carbon atoms, R
5
to R
9
are independently straight, branched or cyclic alkyl groups of 1 to 12 carbon atoms, and a pair of R
1
and R
3
, a pair of R
4
and R
5
, a pair of R
5
and R
6
, a pair of R
7
and R
8
, a pair of R
7
and R
9
or a pair of R
8
and R
9
, taken together, may form a ring. For brevity sake, formulas (1)-a to (1)-c are sometimes referred to as formula (1), hereinafter.
Specifically, making the investigations to be described below, the inventor has established the method of controlling the thermal flow process.
In the inventor's experiment, a variety of base resins commonly used in conventional chemically amplified positive resist compositions were used to form resist films, which were provided with contact holes and subjected to the thermal flow process. The contact hole size was plotted relative to the heating temperature in a graph. It was found that the slope representing a change of contact hole size (to be referred to as a flow rate, hereinafter) was not so different among different base resins. Namely, changing the base resin skeleton gives no substantial difference in the flow rate. The flow rate remains substantially unchanged whether the base resin is a homopolymer or a copolymer and when the molecular weight or dispersity of the base resin is changed. This is also true when the acid labile group and other substituents are changed. The flow rate does not depend on the percent and type of substitution. Blending two or more distinct polymers brings little change of the flow rate. Through these investigations, it was found that only the flow initiation temperature, that is, the temperature at which the contact hole size becomes reduced changes with the base resin and depends on the glass transition temperature (Tg) of the base resin.
A summary of these findings can be illustrated in the graph of FIG.
2
. In
FIG. 2
, curve I denotes a low molecular weight polymer, curve II denotes polymer A, curve III denotes polymer B, curve IV denotes a blend of polymer A and polymer B, curve V denotes a polymer having crosslinking groups, curve VI denotes a high molecular weight polymer, and curve VII denotes a polymer having a high Tg. The gradient of the curve represents the flow rate.
The flow rate can be numerically represented by a change of the contact hole size per degree centigrade of the heating temperature (unit: nm/°C.). While the base resin was changed among a variety of polymers, the flow rate did not sub
Kaneko Tatsushi
Koizumi Kenji
Sakurada Toyohisa
Takemura Katsuya
Baxter Janet
Lee Sin J.
Millen White Zelano & Branigan P.C.
Shin - Etsu Chemical Co. Ltd.
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