Roughening in plasma etch fronts of Si(100)

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 similar to t(beta), with beta = 0.91 +/- 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, [S0031-9007(99)09388-6].