Effects of plasma conditions on the etch properties of AlGaN

In this study, etchings of III-nitrides such as GaN, AlGaN, and InGaN were performed using planar inductively coupled Cl-2/BCl3 plasmas. Especially, etch properties of AlxGa1-xN were investigated as a function of inductive power, bias voltage, substrate temperature, and pressure. Etch rates of GaN were higher than those of AlGaN and InGaN regardless of plasma conditions for the Cl-2-rich plasmas. The increase of the Al composition in the AlGaN decreased the etch rate because of higher bond strength between Al and N and Al-oxidation. The enhancement of AlGaN etch rates could be obtained by the addition of BCl3 to Cl-2 gas and the decrease of the pressure. Plasma diagnostics and surface analysis were performed to understand the etch mechanism of AlGaN. The effective removal of Al from the surface of AlGaN during the etching appears to be important in increasing the AlGaN etch rates. (C) 2000 Elsevier Science Ltd. All rights reserved.