Dynamic repulsion of surface steps during step flow etching: Controlling surface roughness with chemistry

The development of surface roughness during step flow etching of vicinal one- and two-dimensional surfaces was investigated using kinetic Monte Carlo simulations. The two-dimensional simulations were performed on an unreconstructed Si(lll) lattice and were designed to model aqueous silicon etching. In one dimension, the etching of a surface with noninteracting steps leads to a progressive roughening of the surface. In contrast, steps on a two-dimensional surface dynamically repel one another during etching, even when the steps are noninteracting. Dynamic step-step repulsion is the consequence of a feedback mechanism that is induced by step collisions and mediated by the morphology of the etching step and the presence of etch pits. The stability of this feedback mechanism to morphological perturbations is analyzed. During step flow etching, feedback can be enhanced either by increasing the roughness of the steps or the density of pits on the etched surface. Under certain conditions, etching can produce step distributions that are more regular than the corresponding equilibrium distribution. The implications of this observation on the production of very flat surfaces by etching are discussed. (C) 1998 American Institute of Physics.