Elimination of Native Ge Dielectrics at Ge/High-k Dielectric Interfaces for Ge MOS Devices

Abstract

This paper presents a spectroscopic study of interfacial bonding and substrate gate/dielectric reactions for crystalline Ge-high-K gate dielectric hetero-structures. A novel processing sequence has been developed for (i) depositing HfO2 and Hf Si oxynitrides (HfSiON) onto N-passivated Ge(111) and (100) substrates, designed to prevent subcutaneous oxidation of the Ge substrate during dielectric deposition, and then (ii) eliminating N from Ge-N interfacial bonds during 650-800oC rapid thermal annealing in Ar. This approach has been motivated by spectroscopic studies that have shown that the band-gaps of GeO2 and Ge3N4 are reduced with respect to their Si counterparts and cannot be used as interfacial layers (ILs) either: (i) on n-type Ge substrates, or (ii) in n-MOSFETs in which a p-type Ge substrate is inverted. Changes in interface bonding as a function of post-deposition annealing for G/HfO2 Ge/HfSiON, and Ge/HfSiON/HfO2 stacks have been studied by X-ray absorption and photoelectron spectroscopy revealing (i) conduction and valence band edge defects, as well as (ii) significant process induced changes in these defect densities.