Silicon Surface Smoothening Dynamics: Diffusion and Desorption

Abstract

Silicon surface evolution during annealing was investigated by atomic force microscopy (AFM) in a mixture of hydrogen (H2) and hydrogen chloride (HCl). The power spectrum density (PSD) calculated by experimental data was fitted to the analytical results of a continuum surface dynamics equation to determine the surface relaxation mechanism. The coexistence of two mechanisms was revealed, i.e., silicon surface diffusion and silicon desorption by chlorine adatoms, whose relative contribution depended on the HCl concentration. Thus, we proposed a unified model of silicon surface dynamics under pure H2 and HCl atmosphere, which sufficiently clarified the PSD evolution and allowed the determination of the diffusion and desorption reaction constants. Specifically, the evolution of the desorption reaction constant with increasing HCl concentration suggested a complex desorption path.