Amazing diffusion depth of ultra-thin hafnium oxide film grown on n-type silicon by lower temperature atomic layer deposition

Abstract

Hafnium diffusion from ultra-thin high-k gate dielectric HfO2 deposited on n+-Si substrate by atomic layer deposition at lower temperature of 150°C was investigated by using x-ray photoelectron energy spectra (XPS) analysis. The surface is the complete oxidation of HfO2, and Hf and O diffusion into Si substrate with different depths during atomic layer deposition process. Hf and O incorporation into silicon forms silicates accompany with silicides and further silicides only, respectively. An empirical formula was deduced to calculate the diffusion depth of the Hf element to 33nm. The Ni80Fe20/HfO2/Si contact resistance was dominated by tunneling current for the thicker HfO2 but limited by Schottky barrier height for the thinner HfO2 by setting 1.5nm as a watershed.