Study of C2F6 overetch induced damage and the effects of overetch on subsequent SiCl4 etch of GaAs/AlGaAs

Abstract

A quantum well intermixing probe system has been used to study the damage in GaAs/AlGaAs due to exposure to C2F6 plasmas as a function of rf power. At an etching power of ≤80 W, the photoluminescence energy shift after rapid thermal processing is rf power dependent. The etch rate selectivities between SiO2 and GaAs, and between GaAs and AlGaAs were found to increase with decreasing power, while the etching of AlGaAs was inhibited at an rf power of 10 W and below. In situ reflectometry measurements during subsequent SiCl4 etching suggest that fluorocarbon contaminants are deposited on the GaAs surface during the C2F6 etch, that these contaminants protect the surface from oxidation in the air, and therefore the GaAs induction time in SiCl4 is reduced. However, during a SiCl4 etch of a GaAs/AlGaAs layered structure, these contaminants are redeposited on the AlGaAs surface resulting in an increased AlGaAs induction time, a nonconstant etch rate and surface roughening.