Conventionally, in the manufacture of semiconductor devices, micro-processing by lithography using a photoresist composition has been carried out. The micro-processing is a processing method including forming a thin film of a photoresist composition on a semiconductor substrate such as a silicon wafer, irradiating actinic rays such as ultraviolet rays through a mask pattern on which a pattern for a semiconductor device is depicted, developing it to obtain a photoresist pattern, and etching the semiconductor substrate using the photoresist pattern as a protective film. However, in recent progress in high integration of semiconductor devices, there has been a tendency that shorter wavelength actinic rays are being used, i.e., ArF excimer laser beam (wavelength 193 nm) have been taking the place of i-line (wavelength 365 nm) or KrF excimer laser beam (wavelength 248 nm). Along with this change, influences of random reflection and standing wave off a substrate have become serious problems. Accordingly, it has been widely studied to provide an anti-reflective coating between the photoresist and the substrate (Bottom Anti-Reflective Coating, BARC).
As the anti-reflective coating, inorganic anti-reflective coatings made of titanium, titanium dioxide, titanium nitride, chromium oxide, carbon or α-silicon and organic anti-reflective coatings made of a light-absorbing substance and a polymer compound are known. The former requires an installation such as a vacuum deposition apparatus, a CVD (chemical vapor deposition) apparatus or a sputtering apparatus. In contrast, the latter is considered advantageous in that it requires no special installation so that many studies have been made. For example, mention may be made of the acrylic resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule and the novolak resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule (see, for example U.S. Pat. Nos. 5,919,599 and 5,693,691).
The physical properties desired for organic anti-reflective coating materials include high absorbance to light and radioactive rays, no intermixing with the photoresist layer (being insoluble in photoresist solvents), no diffusion of low molecular substances from the anti-reflective coating material into the topcoat resist upon coating or heat-drying, and a higher dry etching rate than the photoresist (see, for example, Tom Lynch et al., “Properties and Performance of Near UV Reflectivity Control Layers”, US, in Advances in Resist Technology and Processing XI, Omkaram Nalamasu ed., Proceedings of SPIE, 1994, Vol. 2195, p. 225-229; G. Taylor et al., “Methacrylate Resist and Antireflective Coatings for 193 nm Lithography”, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 174-185; and Jim D. Meador et al., “Recent Progress in 193 nm Antireflective Coatings, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 800-809).
In recent years, miniaturization of process dimension in lithography process by use of KrF excimer laser beam or ArF excimer laser beam, that is, miniaturization of photoresist pattern to be formed is progressing. With the progress in the miniaturization of photoresist pattern, it is desired to make photoresist thinner in order to avoid collapse of photoresist pattern. When the photoresist is used in a form of thin film, it is desired that an organic anti-reflective coating used together with it can be removed for a short time in order to depress reduction in film thickness of the photoresist layer in a step of removing the organic anti-reflective coating by etching. That is, for reduction in time for etching removing step, it is required that any organic anti-reflective coating can be used in a form of thinner film, or that the organic anti-reflective coating has a larger selection ratio of etching rate with photoresist than the prior one.
By the way, a hitherto technique of anti-reflective coatings has been mainly considered on lithography process with irradiation light having a wavelength of 365 nm, 248 nm or 193 nm. As a result of such consideration, light absorbing components and light absorbing groups effectively absorbing light of each wavelength are developed, and they come to be utilized as one component of an organic anti-reflective coating composition. For example, it is known that chalcone dies prepared by condensation of 4-hydroxyacetophenone with 4-methoxybenzaldehyde are effective for irradiation light having a wavelength of 365 nm (see, for example Japanese Patent Laid-open No. Hei 11-511194), it is known that naphthalene group-containing polymers having a specific structure have high absorbance for irradiation light having a wavelength of 248 nm (see, for example Japanese Patent Laid-open No. Hei 10-186671), and it is known that resin binder compositions containing phenyl unit are excellent for irradiation light having a wavelength of 193 nm (see, for example Japanese Patent Laid-open No. 2000-187331).
In addition, it is known that tris(hydroxyalkyl)isocyanurate substituted with aromatic compound or alicyclic compound is used as a broad UV absorber (see, for example Japanese Patent Laid-open No. Hei 11-279523), and that a curing composition contains cyanuric acid as a polymerizable organic compound (see, for example Japanese Patent Laid-open No. Hei 10-204110). An anti-reflective coating composition containing cyanuric acid derivative is also known (see, for example WO 02/086624). Further, it is disclosed that a polyester synthesized from 1,3,5-tris(2-hydroxyethyl)cyanuric acid is used for an anti-reflective coating (see, for example EP 1298492 A and EP 1298493 A).
In recent years, lithography process with F2 excimer laser (wavelength 157 nm) being a light source having a shorter wavelength comes to be regarded as next-generation technology in place of that with ArF excimer laser (wavelength 193 nm). It is considered that the former process permits micro-processing of process dimension not more than 100 nm, and at present its development and research have been actively carried out from the aspects of apparatus and material, etc. However, most of the research on material relate to photoresist, and it is an actual condition that the research on organic anti-reflective coatings is little known. This is because components effectively absorbing light having a wavelength of 157 nm, that is light absorbing components having a strong absorption band at 157 nm are little known.
It is considered that as irradiation light provides process dimension not more than 100 nm. Therefore, it is also considered that a photoresist is used in a form of thin film having a thickness of 100 to 300 nm that is thinner compared with the prior one. Organic anti-reflective coatings used along with such a photoresist in a form of thin film require the followings: they can be used in a form of a thin film; and they have a high selectivity of dry etching for photoresist. And, it is considered that organic anti-reflective coatings are required to have a large attenuation coefficient k so that they could be used in a shape of thin film having a thickness of 30 to 80 nm. In a simulation with PROLITH ver. 5 (manufactured by Litho Tech Japan; expected and ideal values are used as optical constants (refractive index, attenuation coefficient) of the photoresist), an anti-reflective coating having a base substrate made of silicon with a thickness of 30 to 80 nm can have second minimum thickness (about 70 nm), and in this case the coating has an attenuation coefficient k of 0.3 to 0.6 and a reflectance from substrate of 2% or less, thus has a sufficient anti-reflective effect. In addition, a similar simulation in which silicon oxide is used as base substance and a thickness of silicon oxide varies between 100 nm and 200 nm results in that attenuation coefficient k of 0.4 to 0.6 is required in order to exert a sufficient anti-reflective effect with an anti-reflective coating having a thickness of 70 nm. For example, in case where attenuation coefficient k is 0.2, reflectance from substrate varies between 5% and 10%, and in case where attenuation coefficient k is 0.4, reflectance from substrate varies between 0% and 5%. Consequently, it is considered that in order to exert a sufficient anti-reflective effect, a high attenuation coefficient k, for example 0.3 or more is required. However, any material for organic anti-reflective coatings satisfying such an attenuation coefficient k have been little known.
Under such circumstances, it is demanded to develop organic anti-reflective coatings efficiently absorbing reflection light from a substrate and thereby having an excellent anti-reflective effect. Further, photoresists for lithography process for which irradiation light from F2 excimer laser are used are actively examined at present, and therefore it is considered that many kinds of photoresists will be developed in future. And, it is considered that a method of changing attenuation coefficient so as to suit required characteristics of each photoresist, for example a method of changing attenuation coefficient k comes to be important.
The present invention relates to a composition for forming anti-reflective coating, which has a strong absorption of light at a short wavelength, particularly light at wavelength of 248 nm, 193 nm or 157 nm. In addition, the present invention provides a composition for forming anti-reflective coating, which can be used in a lithography process for manufacturing a semiconductor device carried out by using irradiation light from KrF excimer laser (wavelength 248 nm), ArF excimer laser beam (wavelength 193 nm) or F2 excimer laser (wavelength 157 nm). Further, the present invention provides an anti-reflective coating for lithography which effectively absorbs reflection light from a substrate when irradiation light from KrF excimer laser, ArF excimer laser beam or F2 excimer laser is used for micro-processing, and which causes no intermixing with photoresist layer, can be rapidly removed in the following removal step, and has a high dry etching rate compared with the photoresists. In addition, the present invention provides a method of forming an anti-reflective coating for lithography by using the composition for forming anti-reflective coating, and a method of forming a photoresist pattern.