Morphology of etch-pits on HF-HNO3-H2O vapor-etched diamond wire sawn multi-crystalline silicon wafers

Abstract

We have experimented with vapor-etching texturization of diamond wire sawn multi-crystalline silicon wafers, with the vapor from the thermal evaporation of a HF-HNO3-H2O solution, focusing on the effect of the solution temperature on the surface morphology. The average depth of removal in etching, light reflectivity and surface profile are tracked as well. Three regimes of the solution temperatures are identified. They are featured by weak etching, shallow etch-pits forming and deep dual-scale etch-pits forming, from the range of low, medium to high solution temperatures, respectively. Light reflectivity on the textured surface with the dual-scale etch-pits can be reduced to 14%. It is proposed that the etching reaction is actually caused by liquid droplets condensed from the vapor, rather than by the vapor itself. This may explain the localized etching leading to deep etch-pits, the temperature effects and the formation of the texture with dual-scale etch-pits, in the present vapor etching.