Modification of plasma-etched profiles by sputtering

Two-dimensional etch profiles are modeled for plasma etching, The etch rate dependence on the angle of incidence of the bombarding ions on the etched surface has a sputtering-type yield, The etch profile is advanced in time b y an evolution equation for an etch rate proportional to the modified ion e nergy flux, Approximate analytical expressions for the etch rates are deriv ed as a product of the etch rates in the absence of the sputtering-type yie ld and a weighting factor that depends on the angle the ion drift velocity makes with the normal to the wafer surface, The weighting factor is determi ned from experimental measurements of the angular dependence of ion beam et ching by sputtering, These etch rates are valid when the ratio of the ion d rift speed to the ion thermal speed is large compared to one. The etching i s modeled In the ion flux-limited regime for simplicity, The modifications of the shape of etch profiles of a long rectangular trench and a waveguide structure or strip are treated.