X-RAY PHOTOELECTRON SPECTROSCOPIC STUDY OF THE INTERACTION OF LOW-ENERGY CARBON-IONS WITH GAAS AND INP

To simulate the low energy ion bombardment that occurs in reactive ion etching (RIE) using alkanes, GaAs and InP were exposed to 20, 100, and 500 eV carbon ions, using a mass-separated carbon ion beam in an ultrahigh vacuum chamber. The InP sample structure consisted of a 40 angstrom ultrathin, epitaxial InP layer on InGaAs. The changes induced by ion bombardment and the effects of subsequent damage-removal treatments were determined by in situ polar-angle dependent x-ray photoelectron spectroscopy. Initially, carbon ion irradiation caused minor sputtering of the semiconductors and preferential removal of the group V constituents, with concurrent formation of carbon-semiconductor phases. The depth of these phases and the extent of the damage increased with increasing bombardment energy. An amorphous carbon residue formed after further bombardment. Several damage removal techniques were applied to the carbon bombarded surfaces. It was found that heating was ineffective in annealing the damage, although surface Fermi level movements were observed. Ozone oxidation did not remove the residual carbon efficiently, yet the underlying semiconductor components were readily oxidized. Hydrogen ion bombardment was effective in removing the carbon bombardment induced damage. The implications of these results for alkane based RIE processes are discussed.