Roughening in Plasma Etch Fronts of Si(100)

Abstract

A novel etch front roughening phenomenon has been observed in the plasma etching of Si(100). The morphology exhibits a network structure with holes which coarsen with etech time, and a wavelength selection with a characteristic spatial frequency decreasing with time. The average local slope is invariant while the vertical roughness grows as $w\ensuremath{\sim}{t}^{\ensuremath{\beta}}$, with $\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.91\ifmmode\pm\else\textpm\fi{}0.03$. We suggest a nonlocal Langevin equation based on the redistribution of the reactant gas flux by local morphological features. Numerical calculations give results consistent with our experiments.