Structural and electrical properties of the interfacial layer in sputter deposited LaAlO3/Si thin films

In order to investigate the effects of the sputter deposition parameters and the influence of the post-deposition thermal treatment on the LaAlO3/Si interface, Rutherford Backscattering Spectrometry (RBS), ion channeling, Nuclear Reaction Analysis (NRA), X-ray Photoemission Spectroscopy (XPS), Capacitance–Voltage measurements and Spectroscopic Ellipsometry (SE) were performed on LaAlO3/Si or RuO2/LaAlO3/Si Metal-Oxide-Semiconductor (MOS) structures. RBS-channeling revealed that the Si surface damage due to sputtering deposition at LaAlO3/Si interface is reduced when increasing the deposition pressure, between 0.5 and 5 Pa, and when annealing the films in 1 atm of O2 at 450 °C. XPS spectra were correlated to RBS and NRA measurements. Even if the formation of a low-κ interfacial layer is demonstrated by SE measurements, high deposition pressure and post-deposition annealing in O2 at 600 °C were found to be the best procedure to improve the electrical characteristics of MOS structures in terms of fixed charge and slow trap densities. For these parameters, the κ value was found to be 14, and the equivalent interfacial thickness was estimated to be 1.3 nm, which is lower that most of the previously reported values.