Plasma etching processes for the integration of InP based compounds on 200mm Si wafer for photonic applications

Abstract

Ar/Cl2/CH4 gas mixture has been investigated for the development of plasma etching process dedicated to the patterning of 3μm-deep InP structures integrated on 200mm SiO2 carrier wafer. The plasma process requirements are: high InP etch rates (>500nm.min-1), high InP/SiO2 selectivity (<40), anisotropic profiles and smooth bottom and sidewalls surfaces. The process development mainly focuses on the impact of the gas ratio and gas flow on the etch rates, selectivity, pattern profile and surface roughness. It is demonstrated that the CH4 flow drives the process performance and that by adjusting it properly, a narrow process window provides acceptable selectivity of 25, anisotropic profiles and smooth surface. The difficulty of the process development using Ar/Cl2/CH4 gas mixture is to combine high InP/SiO2 selectivity and anisotropic profiles since to passivate efficiently the InP sidewalls and prevent from lateral etching, it seems that a SiOC like deposition is needed, which is only possible if the SiO2 wafer is etched.