NUMERICAL-SIMULATION OF THE EVOLUTION OF NANOMETER-SCALE SURFACE-TOPOGRAPHY GENERATED BY ION MILLING

Ion milling has been used to transfer the nanometer scale, periodic pa ttern of a protein crystal (''S-layer'') into the supporting substrate . At the same time, etch pits, attributable to the presence of surface contamination, evolve in random areas of the substrate not covered by the S-layer (''off-S-layer''). Using the theory of ripple topography proposed by Bradley and Harper, a computer simulation of hole formatio n based on curvature dependent sputtering and surface self-diffusion h as been formulated. To determine the validity of this model as applied to the patterning process, profiles of actual etch pits have been obt ained using atomic force microscopy, and the simulation has been used to evolve these profiles in time. Even with a number of simplifying as sumptions in place, the model simulates the experimental data quite we ll. (C) 1998 American Vacuum Society. [S0734-2101(98)03003-6].