Method of controlled surface texturization of crystalline semiconductor

Abstract

A method of forming a microscopically texturized surface on a crystalline semiconductor material is disclosed which method includes the use of a radioactive source for uniformly irradiating the surface. The radioactive source includes a plane surface having a uniform distribution of radioactive material thereon In one arrangement the radioactive source surface area is at least the size of the polished crystalline semiconductor surface to be texturized, and the radioactive source is positioned closely adjacent the polished surface for a predetermined time period for uniform irradiation of the same. If desired, the radioactive source and crystalline surface may be relatively movable during irradiation of the surface, in which case the source may be in the form of an elongated strip of sufficient length to extend beyond opposite edges of the polished surface area to be texturized. In any case, the large-surface area radioactive source produces substantially uniform distribution of damage tracks in the crystalline surface, which surface then is anisotropically etched by use of a suitable etching solution. The damage tracks provide etching sites along which etching proceeds at a greater rate than in the undamaged area. Generally the surface to be texturized comprises the (100) orientation surface of a crystalline semiconductor material, such as silicon, at which surface etching preferentially proceeds for exposure of the (111) planes which intersect the surface with fourfold symmetry. With this method a controllable size distribution of tetrahedra may be formed over a large surface.