Observation of Substrate Silicon Incorporation into Thin Lanthanum Oxide Film during Rapid Thermal Annealing

Abstract

Lanthanum oxide (La2O3) has been proposed as the promising gate dielectric material for future complementary metal-oxide-semiconductor (CMOS) technology. However, unlike the conventional homopolar materials such as silicon oxide or silicon nitride, La2O3 is more ionic and in particular at the La2O3/Si interface is less thermally stable. This work investigates the chemical and compositional variations of La2O3 thin film on the silicon substrate during rapid thermal annealing by using angle-resolved x-ray photoelectron spectroscopy (ARXPS) measurements. Results show that thermal annealing at temperatures above 500 °C would result in the incorporation of substrate Si atoms deep into the bulk of the La2O3 film and forming silicate phases both at the interface and in the bulk. These effects would result in the characteristic degradation of CMOS devices.