Etching Characteristics and Surface Analysis of Molecular Bean Epitaxy Grown p-type Aluminum Gallium Nitride With Boron Trichloride/Chlorine Gases in Inductively Coupled Plasma (ICP) Dry Etching

Report No. ARL-TR-3370
Authors: Fred Semendy, Phillip Boyd, and Unchul Lee
Date/Pages: November 2004; 21 pages
Abstract: Dry etching of magnesium doped p-type aluminum gallium nitride grown by molecular beam epitaxy (MBE) has been carried for the first time by inductively coupled plasma (ICP) system via the boron trichloride/chlorine (BCl3/Cl2) gas system with variations in chuck power, ICP power, cholrine (Cl2) ratio in Cl2/BCl3 and process pressure. Processed samples were cleaned by standard techniques, depths were measured, and etching rates and selectivity were calculated. Surface morphology of the etched samples was analyzed by atomic force microscopy (AFM) and scanning electrom microscopy (SEM). Etching rates were influenced by ICP power, and chuck power increased chlorine ratio in BCl3/Cl2 and process pressure. The increase in the etching rate is caused by an increased number of chloride radicals created by high inductive power and increased ion flux and thus, physical bombardment and chemical etching components are enhanced. In most cases, the selectivity with respect to the photo-resistance was higher than 1. AFM showed a smooth surface for the etched samples compared to the un-etched control sample. Roughness values increased initially, followed by a drop indicating the increased smoothness of the surface. Auger electron spectroscopic (AES) studies show that there is a reduction of intensity in the etched samples. Calculations indicated that the gallium/nitrogen decreased slightly in the etched sample, which indicated a very small percentage of nitrogen deficiency because of surface-induced damage by etching. This might give rise to changes in resistance and ohmic contact formation.
Distribution: Approved for public release
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Last Update / Reviewed: November 1, 2004