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
2001-06-25
2004-05-04
Hamilton, Cynthia (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
C525S418000, C525S419000, C525S474000, C525S475000, C525S477000, C525S478000, C525S479000, C528S035000, C528S026000, C528S032000, C528S010000, C528S041000, C430S296000, C430S325000, C430S326000, C430S286100, C430S280100, C430S287100, C430S285100
Reexamination Certificate
active
06730453
ABSTRACT:
This invention relates to high molecular weight silicone compounds (or silicone polymers) suitable as base resins in resist compositions which lend themselves to fine processing in the manufacture of semiconductor devices or the like; resist compositions which are appropriate when high energy radiation such as deep UV, KrF excimer laser radiation (248 nm), ArF excimer laser radiation (193 nm), electron beam or x-ray is used as a light source for exposure; and a patterning method.
BACKGROUND OF THE INVENTION
As the LSI technology tends toward higher integration and higher speed, further refinement of pattern rules is required. The light exposure currently employed as versatile technology is now approaching to the essential limit of resolution which is dictated by the wavelength of a light source. It is generally recognized that in light exposure using g-line (436 nm) or i-line (365 nm) as a light source, a pattern rule of about 0.5 &mgr;m is the limit. LSIs fabricated by this technique have a degree of integration equivalent to 16 mega-bit DRAM at maximum. At present, LSIs fabricated in the laboratory have reached this stage. It is urgently required to develop a finer patterning technique.
One of approaches for making finer patterns is to use exposure light of a shorter wavelength in forming resist patterns. For the mass production process of 256 mega-bit (working size up to 0.25 &mgr;m) DRAM (dynamic random access memory), active research works are now made to substitute a KrF excimer laser of lower wavelength (248 nm) for the i-line (365 nm) as the light source for exposure. However, for the manufacture of DRAM with a degree of integration of 1 G or greater requiring further finer processing technology (working size up to 0.2 &mgr;m), a light source of further shorter wavelength is needed. In particular, photography using an ArF excimer laser (193 nm) is now under consideration.
In the case of lithography using light of a short wavelength of 220 nm or shorter as typified by an ArF excimer laser, in order to form fine patterns, photo-resists are required to have new properties which cannot be met by conventional materials. For this reason, since Ito et al. proposed a chemically amplified positive resist composition comprising a polyhydroxystyrene resin whose hydroxyl group is protected with a tert-butoxycarbonyloxy group (t-Boc group), known as PBOCST, and a photoacid generator in the form of an onium salt, a number of high sensitivity, high resolution resist compositions have been developed. Although these resist compositions have high sensitivity and high resolution, formation of a fine pattern having a high aspect ratio is deemed difficult when the mechanical strength of the resultant pattern is taken into account.
A number of resist compositions using polyhydroxystyrene as a base resin and having sensitivity to deep-UV, electron beams and x-rays are known in the art. These resist compositions rely on a single layer resist technique although a two-layer resist technique is advantageous in forming high aspect ratio patterns on stepped substrates. Because of such outstanding problems of substrate steps, light reflection from substrates, and difficult formation of high aspect ratio patterns, the known resist compositions are far from practical use.
It is known that the two-layer resist technique is advantageous in forming high aspect ratio patterns on stepped substrates. It is also known that in order to develop two-layer resist films with conventional alkali developers, silicone polymers having hydrophilic groups such as hydroxyl and carboxyl groups are required. Since silicone polymers having hydroxyl groups directly attached thereto, however, undergo crosslinking reaction in the presence of acid, it is difficult to apply such silanols to chemically amplified positive resist materials.
Recently, as the silicone based positive resist material capable of solving these problems, chemically amplified silicone based positive resist materials comprising polyhydroxybenzylsilsesquioxane, known as a stable alkali soluble silicone polymer, in which some phenolic hydroxyl groups are protected with t-Boc groups, and photoacid generators combined therewith were proposed (Japanese Patent Application Kokai (JP-A) No. 118651/1995 and SPIE, Vol. 1952 (1993), 377).
However, the polymers used in these silicone resist materials have aromatic rings, which cause substantial light absorption at a wavelength of 220 nm or shorter. Thus these prior-art resins as such cannot be applied to photography using light of a short wavelength of 220 nm or shorter. Since the majority of exposure light is absorbed at the surface of resist, exposure light does not penetrate through the resist to the substrate, failing to form a fine resist pattern. (See Sasago et al., “ArF Excimer Laser Lithography (3)—Resist Rating —,” the preprint of the 35th Applied Physics Society Related Union Meeting, 1P-K4 (1989)).
One exemplary phenyl group-free base resin for silicone based positive resist materials is disclosed in JP-A 323611/1993. Since all hydrophilic groups such as carboxyl and hydroxyl groups necessary to enable alkali development have been protected in this base polymer, many protective groups must be decomposed before exposed areas can be dissolved in the developer. Then the amount of photoacid generator added to this end is increased and the sensitivity is exacerbated. In addition, the decomposition of many protective groups has the high possibility of causing a change of film thickness and generating stresses or bubbles in the film. A resist material having high sensitivity and suited for fine patterning is not available.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel silicone polymer useful as a base resin of a positive resist composition which has a high sensitivity and resolution, is advantageously applicable to the two-layer resist technique suitable for forming high aspect ratio patterns, and can form a heat resistant pattern; a resist composition comprising the polymer as a base resin; and a pattern forming method.
We have found that a high molecular weight silicone compound (often simply referred to as silicone polymer) comprising recurring units of the general formula (1) shown below and having a weight average molecular weight of 1,000 to 50,000, or a high molecular weight silicone compound in which some or all of the hydrogen atoms of carboxyl groups or carboxyl groups and hydroxyl groups in the silicone compound of formula (1) are replaced by acid labile groups of at least one type, as well as a positive resist composition comprising the silicone polymer and a photoacid generator added thereto, or a negative resist composition comprising the silicone polymer, a photoacid generator and a compound crosslinkable under the action of acid, especially resist compositions further comprising a dissolution inhibitor in addition to the photoacid generator, and the resist compositions further comprising a basic compound are effective for increasing the dissolution contrast of resist and especially a dissolution rate after exposure; that the resist compositions further comprising a compound having a group represented by ≡C—COOH in a molecule is effective for improving the PED stability of resist and the edge roughness on nitride film substrates; and that the composition is further improved in ease of coating and storage stability by further blending an acetylene alcohol derivative. Therefore, silicone base resist compositions according to the invention have high transparency, high resolution, improved latitude of exposure, process adaptability, and practical applicability, and are very useful as ultra-LSI resist materials advantageous for precise micro-processing. The present invention is predicated on these findings.
In a first aspect, the invention provides a high molecular weight silicone compound comprising recurring units represented by the following general formula (1) and having a weight average molecular weight of 1,000 to 50,000. Some or all of the hydrogen atoms of carb
Hatakeyama Jun
Ishihara Toshinobu
Kaneko Ichiro
Nagura Shigehiro
Nakashima Mutsuo
Hamilton Cynthia
Millen White Zelano & Branigan P.C.
Shin - Etsu Chemical Co. Ltd.
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