Low-pressure etching of nanostructures and via holes using an inductively coupled plasma system

A high-density inductively coupled plasma source has been used for the fabrication of nanostructures in GaAs and via holes in InP. High etch rates, smooth vertical sidewalls, and high selectivity to a Ni mask have been demonstrated with a pure Cl-2 plasma at very low pressure, down to 0.10 mTorr. At a pressure of 0.12 mTorr; a GaAs etch rate of 582 nm/min, and a selectivity of 146 to a Ti/Ni mask were obtained. Higher stage powers or low pressures induced more damage in GaAs. Horizontal distributed Bragg reflector structures were fabricated in GaAs with mirror widths of 150 nm, spaces of 700 nm, and a depth of 2.3 mu m Etching at a pressure of 0.12 mTorr resulted in a higher normalized etch rate compared to etching at 1.30 mTorr in trench widths ranging from 95 nm to 2 mu m. Via holes were etched in InP to depths >360 mu m. Vertical sidewalls and high etch rates (4.0 mu m/min) were achieved with selectivity of 302 to a Ti/Ni mask at a pressure of 0.5 mTorr. The effect of the aspect-ratio-dependent etching was investigated. It was found that the aspect ratio of the via hole, and not the hole diameter, is mostly responsible for the reduced etch rate in deep trenches. (C) 1999 The Electrochemical Society. S0013-4651(98)04-035-X. All rights reserved.