Magnetized inductively coupled plasma etching of GaN in Cl2/BCl3 plasmas

Abstract

In this study, Cl2/BCl3 magnetized inductively coupled plasmas were used to etch GaN, and the effects of magnetic confinements of inductively coupled plasmas on the GaN etch characteristics were investigated as a function of Cl2/BCl3. Also, the effects of Kr addition to the magnetized Cl2/BCl3 plasmas on the GaN etch rates were investigated. The characteristics of the plasmas were estimated using a Langmuir probe and quadrupole mass spectrometry (QMS). Etched GaN profiles were observed using scanning electron microscopy. The small addition of BCl3 (10%–20%) in Cl2 increased the GaN etch rates for plasmas both with and without magnetic confinements. The application of magnetic confinements to the Cl2/BCl3 inductively coupled plasmas increased the GaN etch rates and changed the Cl2/BCl3 gas composition of the peak GaN etch rate from 10% BCl3 to 20% BCl3. It also increased the etch selectivity over the photoresist, while slightly reducing the selectivity over SiO2. The application of the magnetic field significantly increased positive BCl2+ measured by QMS and total ion saturation current measured by the Langmuir probe. Other species such as Cl, BCl, and Cl+ increased, whereas species such as BCl2 and BCl3 decreased with the application of the magnetic field. Therefore, it appears that the increase of the GaN etch rate in our experiment is related to the increased dissociative ionization of BCl3 by the application of the magnetic field. The addition of 10% Kr in an optimized Cl2/BCl3 condition (80% Cl2/20% BCl3) with the magnets increased the GaN etch rate about 60%. A more anisotropic GaN etch profile was obtained with the application of the magnetic field, and a vertical GaN etch profile was obtained with the addition of 10% Kr in an optimized Cl2/BCl3 condition with the magnets.