Microanalysis of silicon protrusions with a titanium cap formed via surface melting and solidification under applied tensile stress

Abstract

Silicon (Si) protrusions with a peculiar-shaped cap at their top were microanalyzed using scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD) and scanning Auger electron spectroscopy/microscopy. The Si protrusions were formed on a Si(111) substrate via the process of surface melting by DC resistive heating above 1000 °C and solidification under applied tensile stress. The protrusions were micro-sampled by the techniques with focused ion beam, and their cross-sectioned planes were examined by SEM with EBSD. The analysis revealed that the Si protrusions were epitaxially grown as a single crystal on the Si(111) substrate and deposition of titanium (Ti) resulted in formation of the cap as Ti precipitation with other minor impurities. The formation mechanism of the Si protrusion was discussed in terms of surface melting flow in the non-uniform temperature distribution under stress via electromigration, diffusion suppression due to stress-induced steps, and solidification including freezing point depression of the melted Si with the impurities.