ION ENERGY EFFECTS ON SURFACE-CHEMISTRY AND DAMAGE IN A HIGH-DENSITY PLASMA ETCH PROCESS FOR GALLIUM-ARSENIDE

Etch product chlorides from a gallium arsenide substrate subjected to a high density Cl-2/Ar plasma etching process have been sampled in sia l to determine regions of process space commensurate with ion-driven s urface chemistry. Experimental results show three distinct surface che mistry regimes as the ion energy is increased: thermal chemistry for e nergies <50 eV, ion-assisted chemistry for energies of 50-200 eV, and sputtering for energies above 200 eV. Further, ion energies above 200 eV result in unrecoverable pinning of the surface Fermi level whereas at lower ion energies the surface Fermi level returns to the pre-etch condition with in situ Cl-2/Ar plasma passivations.