Characteristics of inductively coupled Cl₂/BCl₃ plasmas during GaN etching

In this study, the characteristics of inductively coupled Cl ₂/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 C1₂/BC1₃ 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 BCl _x⁺ 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 C1₂/10%BC1₃ 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.