Improved Etched Surface Morphology in Electron Cyclotron Resonance-Reactive Ion Etching of GaN by Cyclic Injection of CH_4/H_2/Ar and O_2 with Constant Ar Flow

摘要

Electron cyclotron resonance reactive ion etching (ECR-RIE) conditions for GaN using CH_4/H_2/Ar are investigated. GaN can be etched even with continuous etching using CH_4/H_2/Ar when Ar gas of a higher flow rate is introduced, but only rough etched surfaces are obtained. A cyclic injection method using CH_4/H_2/Ar etching gas and O_2 ashing with constant Ar flow is introduced for GaN etching for the first time, and a rather high etch rate and very smooth etched surfaces are successfully obtained. The cyclic injection of CH_4/H_2 and O_2 prevents deposition of carbon polymers by oxygen plasma, and constant Ar flow removes the surface oxidized layer formed during the O_2 ashing by Ar~+ ion etching. Under the optimized etching condition, an etch rate of 34nm/min and a good morphology of etched surfaces (rms of less than 1.0 nm) are obtained.