Bromine/Methanol Polishing of Indium Phosphide Substrates: II. Dependence on Mechanical Parameters and Flow Rate.

The dependence of bromine/methanol polishing of InP on a number of major parameters-wafer area, applied pressure, rotational speed, and flow rate-has been studied in detail. For a 1 volume % solution, the polishing rate is linearly proportional to flow rate, inversely proportional to wafer area, and independent of pressure and rotational speed. Hence, under our experimental conditions, the polishing action is limited by transport of Br to the wafer surface, and mechanical abrasion of the wafer by the pad is significant. The surface topography is controlled by the wafer size and by a parameter nu, defined as the ratio of flow/wafer area. For nu>~.48 ml/(min cm sup 2), free etching occurs and pits form on the wafer surface. In addition, as lateral dimensions of the wafer shrink to