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
1999-01-26
2004-10-12
Ashton, Rosemary (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
C430S271100, C430S325000, C528S044000, C528S069000, C528S075000, C526S271000, C526S326000, C526S319000
Reexamination Certificate
active
06803168
ABSTRACT:
TECHNICAL FIELD
This invention relates to a composition for an anti-reflective coating or a radiation absorbing coating useful for forming an antireflective coating or other radiation absorbing coating, a monomeric dye, a polymeric dye or a hardening agent compound being used in the composition, a method of forming an anti-reflective coating or a radiation absorbing coating and a method of preparing resist patterns or integrated circuits using the anti-reflective coating or radiation absorbing coating.
BACKGROUND ART
In the field of semiconductor manufacturing, to obtain integrated circuits with a higher degree of integration, miniaturization techniques of resist pattern size have been studied and development and improvement of lithographic processes using short wavelength exposure tools such as deep ultraviolet ray are proceeding. High performance resist showing good properties on deep ultraviolet exposure, as positive- or negative-working chemically amplified photoresists sensitive to deep ultraviolet (100-300 nm) are known. While such exposure tools in combination with the high performance chemically amplified resists are capable of patterning sub-quarter micron geometry, they bring in several other problems that need to be solved in achieving such high resolutions. One such problem which is well known in the art and is called “standing waves” arising from interference with incident beam and reflective beam reflected on the surface of the substrate. Another limitation is the difficulty in uniformly controlling the linewidth of the resist pattern in a single layer resist process due to thin film interference effects resulting from highly planar and non-planar substrates. Such problems are well documented. See, for example, M. Horn in Solid State Technology, November 1991, p. 57, and T. Brunner, Proc. SPIE, vol.1466, p.297 (1991). Other pattern distortions are caused by light reflected angularly from topographical features, which is called reflective notching and are discussed by M. Bolsen, G. Buhr, H. Merrem, and K. Van Werden, Solid State Technology, February 1986, p.83.
One method to overcome the above-mentioned problems is to add dyes to the photoresists as described in U.S. Pat. No. 4,575,480, U.S. Pat. No. 4,882,260 and so on. When a dye is added to the photoresist to form a photoresist film having high optical density at the exposing wavelength, drawbacks such as loss of 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. Another technique to overcome the problem of forming patterns on reflective topography is a top surface imaging (TSI) processes or multilayer resists (MLR) as described in U.S. Pat. No. 4,370,405. Such methods help to prevent the problems associated with reflectivity but are not only complex but also expensive and not a preferred method. On manufacturing semiconductors, single layer resist (SLR) processes are used commonly because of their simplicity and cost-effectiveness.
Another method to eliminate the interference of light is to reduce the substrate reflectivity through the use of so-called bottom anti-reflective coatings (hereinafter abbreviated as BARC). These coatings have the property of absorbing the light which passes through the photoresist and not reflecting it back. As these coatings, two types, inorganic and organic types are known. Inorganic type include such coatings as TiN, TiNO, TiW and inorganic polymer in the thickness of 300 Å. See, for example, C. Nolscher et al., Proc. SPIE, vol.1086, p.242 (1989), K. Bather, H. Schreiber, Thin Solid Films, 200, 93 (1991) and G. Czech et al., Microelectronic Engineering, 21, p.51, (1993). Other examples of inorganic coating are of titanium, chromium oxide, carbon and &agr;-silicon. These inorganic anti-reflective coatings are usually formed by a vacuum evaporation process, a CVD process, spattering and so on. The inorganic anti-reflective coatings,however, have such problems as require precise 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 inorganic coatings show conductivity. The conductive coating is not available for anti-reflective coating upon manufacturing integrated circuits.
Organic anti-reflective coatings have been generally formulated by adding dyes which absorb at the exposure wavelength to a polymer coating (Proc. SPIE, Vol.539(1985), p.342). The organic anti-reflective coating can be formed on a substrate by the same method as resist coating and, therefore, need not use special apparatus. Problems of such dye blended coatings include (1) separation of the polymer and dye components during spin coating, (2) migration of dye into resist solvents and (3) thermal diffusion into the resist upon the baking process. All these cause degradation of resist properties and therefore the method of forming an anti-reflective coating by using a polymer coating composition containing a dye is not a preferred method.
Chemically binding the dyes into film forming polymers is another method. Fahey, et al. (Proc. SPIE, Vol. 2195, p.422) propose to use amino group possessing dyes reacted with the acid anhydride groups of poly(vinyl methylether-co-maleic anhydride) as anti-reflective coating materials. The problem with this type of anti-reflective coating composition is that the reaction between amine and the acid anhydride group is not always 100% complete and this leads to the presence of free amines (refer EP 0583205, page 5, lines 17-20). The free amine causes poisoning of the resist at the interface between anti-reflective coating and resist, especially when a chemically amplified resist composition is used and this leads to a problem called footing. The free dye molecules also sublimes 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 have the similar solvent as the photoresist for anti-reflective coating for the reason that the photoresist and anti-reflective coating are often formed using the same coater. Further, fine particles are formed in the coating composition due to the by-product of the imidization reaction, water, to cause defects in the resist pattern.
In addition, Fahey et al. proposed another anti-reflective coating material based on a copolymer of methyl methacrylate and 9-methylanthracene methacrylate. However, when using a chemically amplified resist, this system also shows footing problems due to the diffusion of photo-generated acid into the anti-reflective coating (Proc. SPIE, Vol.2195, P.426) as well as intermixing of the resist and the anti-reflective coating. Such polymers are also insoluble in preferred solvents in the art, such as propylene glycol monomethyl ether acetate (PGMFA) and ethyl lactate.
U.S. Pat. No. 5,234,990 reports polysulfone and polyurea polymers which possess inherent light absorbing properties at deep ultraviolet wavelengths. These condensation products have poor film forming properties on a patterned wafer, and therefore, bad step-coverage and the formation of cracks perhaps due to high Tg and rigid structures of such polymers. Ideally, a bottom anti-reflective coating materials should form a soft layer with good step coverage property upon coating and also harden at least after baking, to prevent intermixing of the photoresist and anti-reflective coating layer as well as diffusion of the photo-generated acid.
Yet another European Laid-open Patent application No. 542 008 describes the use of phenolic type resin binders and melamine type cross linkers in combination with thermal or photo acid generators to harden the anti-reflective coating film after coating. Such compositio
Kang Wen-Bing
Kimura Ken
Padmanaban Munirathna
Pawlowski Georg
Tanaka Hatsuyuki
Ashton Rosemary
Clariant Finance (BVI) Limited
Kass Alan P.
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