Study of interfacial oxide layer of LaAlO_3 gate dielectrics on Si for metal-insulator-semiconductor devices

摘要

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 SiO_2. 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.