Polarity dependence in Cl2-based plasma etching of GaN, AlGaN and AlN

Smith, M. D., Li, X. , Uren, M. J., Thayne, I. G. and Kuball, M. (2020) Polarity dependence in Cl2-based plasma etching of GaN, AlGaN and AlN. Applied Surface Science, 521, 146297. (doi: 10.1016/j.apsusc.2020.146297)

Abstract

This work compares Cl2-based inductively-coupled plasma (ICP) etching of N-polar and III-polar AlxGa1-xN, including GaN and AlN. For the etch processes of this study, etch rates of AlxGa1-xN decreased with increasing Al:Ga alloy ratio. A 750 W ICP power, 175 W platen power Cl2/Ar ICP process exhibited etch rates in the range 160–450 nm/min for AlxGa1-xN with the precise rate depending on alloy composition and material polarity, and etch rate selectivity between AlN and GaN of 3.0 for III-polar material and 1.6 for N-polar material. Cl2/Ar/O2 processes with 650 W ICP power and 50 W platen power showed an overall reduction in etch rate in the range 2–360 nm/min for AlxGa1-xN with precise rate depending on alloy composition and material polarity. These O2 containing chemistries demonstrated significantly greater etch rate selectivity for N-polar materials (8–80) compared to III-polar materials (1.8–1.9). A correlation between GaN etch rate, surface roughening and selectivity was observed, and the possible reasons behind the polarity dependence of etch rate selectivity are discussed.

• Item Type: Articles
• Additional Information: This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) Grant GaN-DaME (EP/P00945X/1).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Li, Dr Xu and Smith, Dr Matthew and Thayne, Prof Iain
• Authors: Smith, M. D., Li, X., Uren, M. J., Thayne, I. G., and Kuball, M.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Applied Surface Science
• Publisher: Elsevier
• ISSN: 0169-4332
• ISSN (Online): 1873-5584
• Published Online: 20 April 2020