Growth and Characterization of Alternative Gate Dielectrics by Molecular-Beam Epitaxy

Abstract

In this work, we have investigated conditions to grow epitaxial La2O3 and Sc2O3 thin films directly on (111) Si as well as epitaxial LaScO3 thin films on (100) Si using an alkaline earth oxide buffer layer. The films were structurally characterized by reflection high-energy electron diffraction (RHEED) during growth and four-circle x-ray diffraction (XRD) and high-resolution plan-view and cross-section TEM, including Z-contrast TEM after growth. The epitaxial La2O3 thin films grew with the following epitaxial relationship (0001) La2O3 // (111) Si La2O3 // [112] Si with 1 additional rotational twin variant. Sc2O3 thin films grew epitaxially with a cube-on-cube orientation relationship on (111) silicon. It was not possible to achieve epitaxial LaScO3 thin films without the use of an alkaline earth buffer layer. The epitaxial orientation relationship between the orthorhombic LaScO3 and the underlying Si was (101) LaScO3 // (001) Si and [010] LaScO3 // [110] Si.