Formation of subsurface Al2O3 layers in aluminium by oxygen ion implantation

The use of high-dose oxygen ion implants to create buried, insulating SiO2 layers in silicon has been reported by many groups. In contrast, only a few groups have studied ion-implanted oxide layers on and in aluminium films. We have investigated the formation of subsurface Al2O3 layers in bulk, polycrystalline aluminium. In particular, we implanted (1-16) x 1017 atoms cm-2 using low current densities of 180 keV O2+ near room temperature. Depth distributions of oxygen and aluminium were determined using both Auger-electron spectroscopy combined with argon-ion sputtering and helium-ion backscattering. For oxygen fluences greater than about 8 x 1017 atoms cm-2 our analyses revealed subsurface layers of Al2O3 were formed with thicknesses that increased with implanted dose. We combined our results with those from the aluminium film literature to propose a formation process. (orig.)