Overview of Materials Processing and Properties of Lanthanum-Based High-k Dielectrics

Abstract

Lanthanum-based high-K dielectrics remain attractive for gate dielectric applications, in the forms of either lanthanum oxide, lanthanum silicate, or as a lanthanum addition to other dielectrics. Lanthanum oxide and silicate MIS devices have been reported to have EOT values as low as 0.5 nm under low temperature processing. After 1000 {degree sign}C, 10 sec anneals consistent with dopant activation, lanthanum silicate is shown by cross-sectional TEM to remain in the amorphous phase, with no La diffusion into the Si substrate as measured by back side SIMS. Lanthanum addition to hafnium-based dielectrics is presently of interest for the purposes of increasing the dielectric constant, and for providing threshold voltage (Vt) control for obtaining band-edge nMOSFET device operation. A 400-500 mV reduction in Vt is obtained using a lanthana cap layer on HfSiON, achieving band edge nMOSFETs with minimal mobility degradation.