Reactive ion etching of GaN with BCl3/SF6 plasmas

Abstract

Reactive ion etching (RIE) with BCl3/SF6 plasmas of high quality GaN films grown by low pressure metallorganic chemical vapor deposition (LP-MOCVD) is reported. A high etch rate of 2100 Angstrom min(-1) was achieved with BCl3/SF6 plasmas at gas pressure 40 mtorr, total gas flow rate 40 seem, and radio-frequency (RF) power 300 W. The parameters affecting the etch rates such as BCl3/SF6 flow ratio, total gas pressure, RF power and self-bias voltage have been studied. Results indicate that under high RF power (300 W) the radical concentration is an etch rate-limiting factor at lower BCl3/SF6 pressure (lower than 40 mtorr), while self-bias voltage (ion bombardment) is a rate-limiting factor at higher pressure (more than 40 mtorr). Under lower RF power (150 W), self-bias voltage becomes the dominant factor of etch rate. Scanning electron microscopy (SEM) shows that the etched profile is highly anisotropic, and the etched area has some columnar residues due to Al compound contamination from the Al cathode during RIE.