FORMATION OF EXTREMELY FINE PATTERN

摘要

PURPOSE:To improve the reproducibility for providing a semiconductor substrate with an extremely fine groove by means of dry etching with the use of a mask which has an inversed trapezoidal cross section and is perforated with a desired width on the bottom thereof, by interposing therebetween a thin film which has a higher etching rate than the mask layer and a lower rate than the layer to be treated. CONSTITUTION:A polycrystalline Si substrate 11 is provided thereon with a mask 12 consisting of an SiO2 film having a inversed trapezoidal cross section and having an aperture with a desired width on the bottom face. The substrate 11 is then perforated to have a fine groove passing therethrough by dry etching with the use of etching gas containing reactive elements. In this case, a resist film 13 whose etching rate is higher than that of the mask 12 but lower than that of the substrate 11 is interposed between the substrate 11 and the mask 12 before etching the substrate. According to this method, an aperture hole produced in the film 13 is undercut, but on the bottom face of the film 11 the hole has the same dimension with the aperture of the bottom face of the film 12. Accordingly the substrate 11 can be provided with an extremely fine groove being required.