(310d) 3-Dimensional Monte Carlo Profile Simulation and Experimental Measurements of Surface Roughness Under Plasma Etching

Surface roughening on Si and SiO₂ were experimentally measured and modeled in the 3-Dimensional Monte Carlo profile simulator as a function of etching chemistry, ion incidence angle and amount of etching time. Experimental data and modeling results were in good quantitative agreement in terms of etching yield and roughness level, suggesting the incorporated mixing-layer kinetics model is able to accurately account for the chemistry taking place on various substrates and plasma chemistries. Morphologically, all films displayed transverse striation at intermediate ion angle, and parallel striation at grazing ion angle in Ar sputtering or low polymerizing C₄F₈/Ar chemistry. The transition from transverse to parallel striation at different ion angles were captured with the profile simulator by combining the curvature-dependent sputtering with surface diffusion suggested by B-H model, through which the impinging ions deliver more energy to the surface in depressions relative to elevations. It was demonstrated experimentally and in modeling that the ripple formation is sensitive to the amount of etching: transverse striation on single-crystal Si at 60^◦ ion angle gave way to parallel striation as etching persisted. The surface roughening mechanism at grazing angle at 75^◦ ion angle was proposed as the micromasking mechanism which effectively roughens the surface with both clean net-etching region and sporadically polymer-rich net-deposition region.