Characteristics of inductively coupled Cl2/BCl3 plasmas during GaN etching

Abstract

In this study, the characteristics of inductively coupled Cl2/BCl3 plasmas during GaN etching were estimated using plasma mass spectrometry by measuring the relative amounts of positive ions, neutrals, and etch products. The results showed that the enhancement of GaN etch rates for Cl2/BCl3 plasmas could be related to the formation of Cl radicals and reactive ions such as Cl2+ and BCl2+ measured by the mass spectrometry during GaN etching. These Cl radicals are responsible for chemisorption and BClx+ and Cl2+ for chemical and/or physical sputtering. Ion assisted chemical desorption seems to be generally enhanced by the addition of BCl3 to Cl2 and also with the increase of pressure. Also, the abundance of BCl2+ in the Cl2/10%BCl3 plasmas appears to be important in GaN etching compared to pure Cl2 plasma. Ga+, GaCl2+, and N2+ were observed during GaN etching as the etch products and the intensities of these ion etch products were correlated with the trend of the GaN etch rate.