SIO2 MASK EROSION AND SIDEWALL COMPOSITION DURING CH4 H-2 REACTIVE ION ETCHING OF INGAASP/INP/

SiO2 mask erosion has been studied during CH4/H-2 reactive ion etching of InGaAsP/InP double heterostructures. The amount of mesa mask narro wing at a pressure of 100 mT, normalized for an etch depth of 3.5 mum, is approximately 0.4-0.6 mum and decreases slightly with increasing s elf-bias voltage. It is not strongly dependent on the sidewall angle o f the mask or CH4 concentration. Mask residue deposits on the etched s idewall under conditions of relatively high CH4 concentration and low power density. Auger electron spectroscopic analysis of the sidewall s hows that the deposit contains a significant amount of elemental Si, w hich suggests a mechanism for mask erosion in which SiO2 is reduced to Si in the hydrogen/hydrocarbon-rich environment of the plasma.