Study of interfacial oxide layer of LaAlO3 gate dielectrics on Si for metal-insulator-semiconductor devices

Lanthanum aluminate (LAO) thin films were deposited on silicon by pulsed-laser deposition. It was found that oxygen partial pressure played an essential role in the formation of an interfacial layer. The films deposited in nitrogen at a pressure of 20 Pa had no interfacial layer. However, an interfacial layer was observed in the films deposited in 1 x 10-2 Pa atmosphere. According to the thickness of the LAO film and interfacial layer and the measured capacitance, it could be deduced that the interfacial layer was not pure SiO2. Auger electron spectroscopy, secondary ion mass spectroscopy and X-ray photoelectron spectroscopy depth analyses indicated that the interfacial layer was La-Al-silicate rather than pure silicon oxide and that the La and Al concentrations in the interfacial layer had gradients from the LAO layer to the substrate. (orig.)