Metalorganic chemical vapor deposition of aluminum oxide on Si: Evidence of interface SiO2 formation

Thin films of aluminum oxide were deposited on H-passivated Si(100) substrate using trimethylaluminum and oxygen at 0.5 Torr and 300 °C. Fourier transform infrared (FTIR) and x-ray photoelectron spectroscopic analyses of these films showed no aluminum silicate phase at the film–substrate interface. The O/Al ratio in the deposited film was found to be higher than that in stoichiometric Al2O3. On annealing the as-deposited samples in Ar at 900 °C, an absorption peak due to the transverse optical phonon for the Si–O–Si stretching mode appeared in the FTIR spectra. A combination of Z-contrast imaging and electron energy-loss spectroscopy in the scanning transmission electron microscope confirmed that the annealed samples developed a layer of silicon dioxide at the aluminum oxide–Si interface. Our results suggest that excess oxygen present in the deposited film reacts with the underlying Si substrate and forms silicon oxide.