Low damage dry etching of III-V materials for heterojunction bipolar transistor applications using a chlorinated inductively coupled plasma

Etching of InGaAs and InP in inductively coupled plasma (ICP) using SiCl4 w as studied for heterojunction bipolar transistor (HBT) applications. Low sa mple temperature was used to minimize etching isotropy and to reduce group V element desorption. The low ion energy etching process results in a damag ed layer thickness of a few Angstrom. Auger electron spectroscopy results o n InP demonstrate a very thin layer of nonstoichiometric material. The natu re of the etching mask impacts the surface contamination: local contaminati on effects due to sputtering are observed. For such low ion energy process, the sample preparation before ICP etching is shown to be very important fo r surface roughness, as observed by atomic force microscopy. Various prepar ation schemes have been investigated, before ICP etching, for reduction of the surface degradation resulting from ICP etching. It is shown that the be st results in terms of roughness and etch-rate are obtained with a silicon nitride mask and surface oxidation by ultraviolet ozonization before a wet desoxidation immediately preceding the ICP etching. An ICP process was used successfully for partly etching the base mesa of HBT structures. No signif icant difference with wet etching was observed in terms of induced damage a nd HBT current gain. (C) 1999 American Vacuum Society. [S0734-2101(99)22004 -0].