ELECTRON-CYCLOTRON-RESONANCE PLASMA-ETCHING OF ALGAN IN CL-2 AR AND BCL3/AR PLASMAS/

A comparison of etch rates for AlxGa1-xN alloys was performed in Cl-2/ Ar and BCl3/Ar electron cyclotron resonance plasmas. The etch rates we re generally found to decrease with increasing AlN concentration, due to the increasing average bond strengths at higher Al compositions. Th e fastest rates were found in the Cl-2/Ar chemistry, with rates of sim ilar to 3500 Angstrom/min for GaN, 1700 Angstrom/min for AlN, 2500 Ang strom/min for Al0.31Ga0.69N, and 3300 Angstrom/min for Al0.2Ga0.8N. Th e etched surfaces were also smoother with the Cl-2/Ar plasma chemistry than the BCl3/Ar plasma chemistry. The etch selectivities for GaN ove r Al0.2Ga0.8N, Al(0.3)1Ga(0.69)N, and AlN were quite low, less than or equal to 5 for all conditions, and this is due to the ion-driven natu re of the removal mechanism.