Research on p-GaN/AlGaN high sidewall verticality and low damage etching applied to enhanced GaN HEMTs devices

A fast ICP (inductively coupled plasma) etching followed by slow ALE (atomic layer etching) etching method is proposed to achieve high sidewall perpendicularity and low damage etching of the p-GaN/AlGaN interface for enhanced GaN HEMTs devices. Firstly, the effects of parameter changes such as upper electrode power, lower electrode power, chamber pressure and gas flow rate on the verticality of the p-GaN/AlGaN interface and the damage degree of AlGaN in ICP etching were investigated. After several experiments, the optimal parameters for ICP etching were obtained as follows, chamber pressure of 15mt, upper electrode power of 450w, lower electrode power of 50w, chlorine flow rate of 90sccm, nitrogen flow rate of 25sccm, oxygen flow rate of 4sccm, argon flow rate of 50sccm, and etching time of 45s. The verticality of the sidewall of the p-GaN/AlGaN interface after etching under the optimal process parameters of ICP dry etching is 75-77°, the root mean square roughness of the etched surface is 0.607 nm, and there are micro-grooves on the sidewall of the p-GaN/AlGaN interface. The new proposed method can achieve 81° of P-GaN sidewall perpendicularity, 0.397nm root mean square roughness of etched surface, smoother etched sidewall and no microgrooves, and significantly improved etching effect.