In-Situ Monitoring by Mass Spectrometry for GaAs Etched with An Electron Cyclotron Resonance Source

Abstract

Quadrupole mass spectrometry (QMS) has been used as an in-situ diagnostic technique for GaAs etched with an electron cyclotron resonance source. Changes in the detected signal intensities for reactive species and etch products have been related to corresponding changes in the etch rate as several process parameters were varied. The detected 75As+ and to a lesser degree, 35C1+ and 70C12+, were observed to follow etch rate as microwave power, rf power, source to sample distance, temperature, and pressure were varied. The self-induced dc bias (IVdcl) determines the etch rate dependence on etch time. The time delay before saturation of the monitored 75As+ signal corresponding to a constant etch rate is inversely proportional to IVdcl. The addition of N2/O2 in a 4:1 ratio to constitute 15% of the total discharge resulted in a 95% decrease in the intensity of the monitored 75As+ signal. The measured etch rate decreased by 75%.