Analysis of ultrathin SiO2 interface layers in chemical vapor deposition of Al2O3 on Si by in situ scanning transmission electron microscopy

The development of Al2O3 as an alternative gate dielectric for microelectronic applications depends on the ability to grow a high-quality nanoscale thin film that forms an atomically abrupt interface with Si. Here, the combination of in situ Z-contrast imaging, electron energy loss spectroscopy and x-ray photoelectron spectroscopy of amorphous Al2O3 films grown by metalorganic chemical vapor deposition shows that excess oxygen incorporated into the film routinely reacts with the Si substrate to form an amorphous SiO2 interface layer during postdeposition annealing. The intrinsic oxygen-rich environment of all films grown by such techniques and the necessity of postdeposition processing in device applications implies that control and optimization of the SiO2 interface layers could be of utmost interest for high-κ dielectric stacked structures.