Plasma etching of III-nitrides in ICl/Ar and IBr/Ar plasmas

Abstract

Two new plasma chemistries, ICl/Ar and IBr/Ar, were investigated for dry etching of III-nitrides. Under electron cyclotron resonance conditions, we examined the effect of plasma composition, and source and chuck power on etch rates and surface morphology. The etch rate of InN proved to be the most sensitive of the materials investigated to the plasma composition and ion density in ICl plasmas. The GaN, InN, and InGaN etch rates reached ∼13 000, 11 500, and 7000 Å/min, respectively, at 250 W rf chuck power and 1000 W microwave source power for ICl discharges. The etch rates in IBr plasmas were somewhat slower than in ICl. The etched surface of GaN was found to be smooth, with no significant preferential loss of N from the surface at low rf powers in either chemistry. There was no significant residue on the GaN surfaces after etching in IBr/Ar, and only slight chlorine contamination on the surfaces etched in ICl/Ar. Selectivities of 5–10 for GaN over InN, AlN, or InAlN were achieved in ICl/Ar, but were <4 under all conditions with IBr/Ar.