Probing the stability of Al2O3/Ge structures with ion beams

Al2O3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submitted to different post-deposition annealings (PDAs) in order to probe composition modifications induced by such treatments. Nuclear reaction profiling (NRP) revealed that O incorporation depends on PDA temperature and on the employed atmosphere (water or oxygen). We also found that O from the gas phase strongly interacts with the Ge semiconductor substrate when PDA is performed with water at 500 °C. Ion scattering analyses evidenced an increase of Ge concentration throughout the Al2O3 dielectric layer and on the sample surface associated with the oxidation of the Ge substrate. These findings are explained by GeO desorption resulting from chemical reactions occurring at the dielectric/Ge interface.