Mechanisms of and Solutions to Moisture Absorption of Lanthanum Oxide as High k Gate Dielectric

Abstract

Moisture absorption is a big problem of lanthanum oxide (La2O3) as a high permittivity (k) gate dielectric which can degrade properties of La2O3 films. In this study, two possible mechanisms were proposed. One is oxygen vacancies related mechanism. And the other is the intrinsic reaction between La2O3 and H2O due to the small lattice energy of La2O3. To suppress these two mechanisms of moisture absorption, two solutions were proposed respectively. One is ultraviolet (UV) ozone post treatment to suppress the oxygen vacancies related mechanisms via healing oxygen vacancies in La2O3 films. Our experiment results show that UV ozone treatment can suppress the moisture absorption of La2O3 film. The other solution is to dope larger lattice energy oxide to suppress the intrinsic moisture absorption reaction. We tried the Y2O3 doping (LaYOx film). Experiment results indicate that LaYOx films show much stronger moisture resistance than La2O3 film.