Temperature Effect on Vapor Phase Etching of Ground Silicon Substrate and Surface Morphology

Abstract

AbstractWe have been using the low-cost method of fabrication of epitaxial wafer for discrete devices for many years. This low-cost operation is done by eliminating the conventional but costly polishing procedure, instead of using grinding, cleaning and etching processes prior to epitaxy growth. The etching step is needed to remove any residual grinding scratches and possible remaining contamination. In this study, etching is accomplished with HCl gas at a temperature range from 1120 to 1150 °C, at atmospheric pressure. The surface analysis and inspection techniques were used to test residual grinding scratch removal and point defect density. It is found that the temperature effect on the etch rate is small, but the surface morphology with ground pattern is very sensitive to the etching temperature. The study revealed the presence of regions of temperature which the silicon surface has a minimum of grinding scratches and little etch pits. The etching temperature has strong effect on the substrate surface thereby strongly impacting subsequent epitaxial layer morphology. The different morphologies and their temperature dependence can be explained on the basis of the thermodynamics of the surface and role of surface diffusion and evaporation.