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
1999-08-09
2001-12-11
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
C430S280100, C430S287100, C430S271100, C430S313000, C430S319000, C430S323000, C430S325000, C430S326000, C430S905000, C430S906000, C430S907000, C430S910000, C526S273000, C526S288000, C526S304000, C526S307100, C526S329500, C526S329700
Reexamination Certificate
active
06329117
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a composition available for forming an anti-reflective coating such as a bottom anti-reflective coating or a light absorbing coating, a polymer used in the composition, a method for forming an anti-reflective coating or a light absorbing coating, an anti-reflective coating and a light absorbing coating formed by the method, a method for forming resist patterns and a method for integrated circuits by use of the composition.
BACKGROUND ART
In manufacturing semiconductors, finer and finer patterning of resist images has been required and attempted to attain higher integration. In order to satisfy this requirement, there have been made development and improvement of lithographic techniques using short-wavelength exposure tools such as deep-UV. As photoresists showing high performance when exposed to deep-UV, there have been known chemically amplified, deep UV (100-300 nm) positive- or negative-working photoresists. While such exposure tools in combination of the chemically amrplified, high performing photoresists enable one to pattern with less than quarter micron line width, there still remain several other problems that need to be solved in achieving such high resolutions. One such problem well known in the art is called “standing waves” arising from interference between incident light and reflected light of the incident light reflected on the substrate surface. Another problem is the difficulty in uniformly controlling the line width in single layer resist process due to thin film interference effects resulting from highly planar and non-planar substrates. Various reports have been made. For example, there are illustrated the report of M. Horn in Solid State Technology, Nov. 1991, p. 57, the report of T. Brunner, Proc. SPIE, vol. 1466 (1991), p.297, etc. In addition, as a cause which causes pattern distortions, there is the phenomenon called reflective notching which is caused by light reflected angularly from topographical features. This is discussed by M. Bolsen, G. Buhr, H. Merrem, and K. Van Werden, in Solid State Technology, Feb. 1986, p.83.
Lithographic techniques to solve the problems upon forming patterns on reflective topography include addition of dyes to the photoresists as described in U.S. Pat. Nos. 4,575,480 and 4,882,260, etc. However, when a dye is added to the photoresist to form a film having high absorption to the light of exposing wavelength, drawbacks such as decrease in resist sensitivity, difficulties during hardening processes, thinning of the resists in alkaline developers and sublimation of the dyes during baking of the films are encountered. In addition to the technique of adding dyes to photoresists, top surface imaging (TSI) processes, multilayer resists (MLR) method as described in U.S. Pat. No. 4,370,405 also help solve the problems associated with reflection but such methods are not only complex but also expensive and not a preferred method. Single layer resist (SLR) processes dominate semiconductor manufacturing because of their cost-effectiveness and simplicity.
Another strategy to eliminate the interference of lights is to reduce the substrate reflectivity through the use of so-called bottom anti-reflective coatings (BARCs). These coatings have the property of absorbing the light which passes through the photoresist and not reflecting it back and prevent the reflection by the substrate. As the bottom anti-reflective coatings, there are known inorganic types and organic types. Inorganic types include coatings of TiN, TiNO, TiW or inorganic polymer of 300 Å in thickness, as described in C. Nolscher et al., Proc. SPIE, vol. 1086 (1989), p.242, K. Bather, H. Schreiber, Thin Solid Films, 200, 93 (1991), G. Czech et al., Microelectronic Engineering, 21 (1993), p.51. In addition to these coatings, there are also known inorganic coatings such as a titanium coating, a chromium oxide coating, a carbon coating, an &agr;-silicon coating, etc. These inorganic anti-reflective coatings are usually formed by vacuum deposition, CVD, sputtering or the like. However, formation of such coatings requires accurate control of the film thickness, uniformity of film, special deposition equipment, complex adhesion promotion techniques prior to resist coating, separate dry etching pattern transfer step, and dry etching for removal. Some of the inorganic coatings can not be used in manufacturing integrated circuits due to their conductivity.
On the other hand, as the organic anti-reflective coatings, there are illustrated those formulated by adding dyes which absorb light of the exposure wavelength to a polymer coating (Proc. SPIE, Vol. 539 (1985), p.342). This dye-containing, anti-reflective coating can be formed on a substrate in the same manner as with photoresists, and does not require any special equipment as is different from the inorganic anti-reflective coatings. However, they involve such problems as 1) separation of the polymer and dye components during spin coating, 2) dye stripping into resist solvents, and 3) thermal diffusion into the resist upon the baking process. All these factors cause degradation of resist properties, and therefore the technique of adding a dye to the polymer coating to form an anti-reflective coating is not a preferred one.
Chemically binding the dyes to film forming polymers is another option. Fahey, et al. (Proc. SPIE, Vol. 2195, p.422) report to use a reaction product obtained by reacting an amino group possessing dye with the anhydride groups of poly(vinylmethyl ether-co-maleic anhydride) as the material for forming the anti-reflective coating. The problem with this type anti-reflective coating material is that the reaction between amine and the anhydride groups are not always 100% complete and this leads to presence of free amines (refer European unexamined patent application No. 0583205, page 5, lines 17-20). The remaining free amine causes poisoning at the interface between the anti-reflective coating and the resist coating especially when a chemically amplified resist is used as the resist, and this leads to a problem called footing: incomplete dissolution of the exposed resist upon development. In addition, there arises another problem that free dye molecules sublime during the baking process and deposits on the fabrication instruments and causes contamination problem as well as health hazard to the workers. One more problem of such compositions is that imide compounds are poor in their solubility and need polar solvents normally not used in photoresist formulations. It would be ideal to use the same solvent for both the photoresist and the anti-reflective coating since the same coating apparatus is often used for applying the photoresist and the anti-reflective coating. Further, the by-product of imidization reaction, water, causes coating defects during film formation.
Another system Fahey et al. propose is materials wherein a copolymer of methyl methacrylate and 9-methylanthracene methacrylate is used as the anti-reflective coating. Again this system also shows footing problem due to the diffusion of photo-generated acid into the anti-reflective coating when a chemically amplified resist is used as the resist (Proc. SPIE, Vol. 2195, p. 426) as well as intermixing of the resist material and the anti-reflective coating material. Such polymers are also insoluble in preferred solvent in the art such as propylene glycol monomethyl ether acetate (PGMEA), ethyl lactate, etc.
U.S. Pat. No. 5,234,990 discloses polysulfone and polyurea resins which possess inherent light absorbing properties at particular deep ultra violet wavelengths. These condensation products have poor film forming property on a patterned wafer and therefore bad step-coverage and also formation of cracks perhaps due to high Tg and rigid structures of such polymers. Ideally, a bottom anti-reflective coating materials should be soft for good step coverage property before baking and also hardened at least after as baking to prevent intermixing of the photoresist and the anti-reflective coating as well as diffu
Kang Wen-Bing
Kimura Ken
Padmanaban Munirathna
Pawlowski Georg
Tanaka Hatsuyuki
Banerjee Krishna
Baxter Janet
Clariant International Ltd.
Lee Sin J.
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