MACROSCOPIC MODEL FOR COLUMNAR GROWTH OF AMORPHOUS FILMS BY SPUTTER DEPOSITION

We present a macroscopic model for the growth of amorphous films produced by sputter deposition under conditions of high buffer gas pressure. Consistent with the latter assumption, we assume that incident flux approaches the surface from all angles of incidence. Explicit account is taken of two important physical effects: (i) surface diffusion and (ii) the fact that some parts of the surface will be geometrically shadowed from receiving flux by other parts of the surface. The physical variables which define the problem (e.g., deposition rate, surface diffusion constant, temperature, etc.) can be combined to form a characteristic length and a characteristic time which determine the rescaling required to reduce the problem of morphological prediction to a characterization of the initial conditions. All the well-known features of columnar growth are found and a simple physical explanation for "survival of the fittest" columns is provided.