Thermal stability of LaAlO3/Si deposited by laser molecular-beam epitaxy

Abstract

High-k gate dielectric material LaAlO3 (LAO) films were deposited directly onto silicon substrates by laser molecular-beam epitaxy. The thermodynamic stability of LAO films deposited at different substrate temperatures and of LAO films postannealed at 1000 °C was studied by high-resolution transmission electron microscopy and capacitor–voltage measurements. These studies show that the interfacial reaction between the LAO film and silicon substrate is strongly correlated to the substrate temperature and ambient conditions. In oxygen containing ambient, the interfacial reaction often occurs not only during film deposition but also during the course of postannealing. LAO films annealed at 1000 °C in nitrogen ambient have better thermal stability with silicon than LAO films annealed in oxygen ambient do. Both kinds of films remain amorphous after 1000 °C annealing.