Surface transport kinetics in low-temperature silicon deposition determined from topography evolution

Abstract

In this article, surface transport kinetics during low-temperature silicon thin film deposition are characterized using time dependent surface topography and dynamic scaling models. Analysis of surface morphology indicates that diffusion of adsorbed species dominates surface transport, with a characteristic diffusion length that increases with surface temperature. A diffusion activation barrier of $\ensuremath{\sim}0.2 \mathrm{eV}$ is obtained, consistent with hydrogen-mediated adspecies diffusion on the growth silicon surface. Samples are compared over a range of deposition temperatures (25 to $350\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ and film thickness (20 to $5000 \AA{})$ deposited using silane with helium or argon dilution, on glass and silicon substrates. Self-similar surface structure is found to depend on detailed film growth conditions, but is independent of film thickness after nuclei coalescence. For films deposited using helium dilution, static and dynamic scaling parameters are consistent with self-similar fractal geometry scaling, and the lateral correlation length increases from 45 to 150 nm as temperature increases from 25 to $150\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ These results are discussed in relation to current silicon deposition models and with topography evolution observed during low temperature growth of other amorphous material systems.