Improvement of process uniformity in recessed gate AlGaN/GaN HFET by selective etching of in-situ Si sub(x)N sub(y) on AlGaN

• Published in: Japanese Journal of Applied Physics 2014-01, Vol.53 (4S), p.04EF05-1-04EF05-4
• Main Authors: Ko, Hwa-Young, Park, Jinhong, Lee, Hojung, Jo, Youngje, Song, Misun, Jang, T
• Format: Article
• Language: English
• Subjects: Aluminum gallium nitrides; Devices; Etching; Gallium nitrides; Gas flow; Gates; Selectivity; Threshold voltage; Variability
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.53.04EF05

The effects of in-situ Si sub(x)N sub(y) etching were investigated by comparing the uniformity of threshold voltage on recessed gate AlGaN/GaN heterostructure field effect transistor (HFET) devices with in-situ grown Si sub(x)N sub(y) passivation. By varying O sub(2) ratio in total gas flow, etch rate and selectivity of Si sub(x)N sub(y) and AlGaN were changed significantly. The etch rate of AlGaN was reduced by adding O sub(2) in gas mixture, which caused the formation of AlO sub(x) and GaO sub(x) on the surface during etching process. The etch rate of in-situ Si sub(x)N sub(y) was decreased with increasing O sub(2) ratio. By this relationship, the highest selectivity was obtained with 30% O sub(2) ratio in total gas flow and selectivity was increased from 5:1 to 100:1. Using this optimized etching condition, the standard deviation of threshold voltage on AlGaN/GaN recess gate HFET was improved from 0.60 to 0.18 on 6-in. processed wafer.