NEW CHEMISTRY FOR SELECTIVE REACTIVE ION ETCHING OF INGAAS AND INP OVER INALAS IN SICL4 SIF4/HBR PLASMAS/

A selective reactive ion etching process which etches InP and InGaAs, but not InAlAs, using a mixture of SiCl4/SiF4/HBr gases has been devel oped. Optical emission spectroscopy shows that the dominant emitting s pecies in the plasma an HBr+, Br, and Br-2, with a weaker emission fro m SiBr and SiHBr. We believe that the bromosilanes or chlorosilanes of the form (SiHxBry,SiHxCly) are responsible for the etching of these I n-containing compounds by the formation of indium bromosilanes and ind ium chlorosilanes. Using a flow rate ratio of SiCl4/HBr of 7/15 sccm, a pressure of 100 mTorr and with de bias of 80 V, an etch rate of InGa As and InAlAs as high as 100 nm/min at room temperature was achieved w ith good surface morphology. The addition of SiF4 suppresses the etchi ng of InAlAs and the selectivity obtained can be changed by varying th e proportion of SiF4. At a flow rate ratio (SiCl4:SiF4:HBr) of 5/6/20 sccm, dc bias of less than or equal to 70 V and a pressure of 150 mTor r, the selectivity obtained is extraordinarily high (>600:1) for this material system. (C) 1995 American Institute of Physics.