METHYL RADICAL ETCHING OF COMPOUND SEMICONDUCTORS WITH A SECONDARY AFTERGLOW REACTOR

While halogen-based dry etching processes are well established for silicon devices, many compound semiconductors have insufficiently volatile halides for successful conventional dry etch processing. These elements, found in groups II B. III A. IV A. V A. and VI A of the Periodic Table, do form volatile organometallic compounds. A secondary afterglow reactor, in which atomic fluorine produced in a microwave discharge is reacted with methane downstream of the discharge, has been used to etch HgCdTe, CdTe, InP, InSb, and GaAs at temperature-dependent rates between 100 Å and 1000 A/min. This etching is purely chemical and without ion bombardment, and it shows crystallographic orientation dependence on the etch rate. The activation energies for etching in a methyl/atomic hydrogen ambient range from 2.3 and 7.2 kcal/ mol. CdTe (111)B etched faster, smoother, and with a higher activation energy than CdTe(100), which produced a surface with submicron texturing. Specular surfaces were observed with CdTe, InP, InSb, and GaAs, although the HgCdTe etched with significant roughness. © 1990, American Vacuum Society. All rights reserved.