Graphoepitaxy of silicon on fused silica using surface micropatterns and laser crystallization

Abstract

Uniform crystallographic orientation of silicon films, 500 nm thick, has been achieved on amorphous fused silica substrates by laser crystallization of amorphous silicon deposited over surface-relief gratings etched into the substrates by reactive ion etching. The gratings had a square-wave cross section with a 3.8 μm spatial period, a 100–nm depth and corner radii of about 5 nm. The 〈100〉 directions in the silicon were parallel to the grating to within ±18°, and perpendicular to the substrate plane to within ±2.5°. A simple model for the graphoepitaxy process is presented. Sheet resistivity of phosphorous doped graphoepitaxial silicon was 2.5 times larger than that of bulk silicon of the same doping. Graphoepitaxy is a new application of microstructure fabrication that may lead to new combinations of substrates and overlayer films, and perhaps to three-dimensionally integrated electronic devices and other novel configurations.