Thermal stability of HfN compounds on HfO₂/SiO₂ gate stacks

Abstract

The thermal stability of HfN compounds on HfO2/SiO2 gate stack has been investigated. Before annealing, HfN and HfSiN were found to have a work function of a band-edge N metal. Films have very good thermal stability as measured by Rutherford backscattering. Gate stack high temperature instabilities were observed to occur at the SiO2/Si interface because of the high oxygen solubility of HfN and HfSiN which tends to reduce the underlying SiO2 layer. Attempts to improve the high temperature gate stack stability by incorporating oxygen into the Hf compounds to reduce its oxygen solubility produced some SiO2 interfacial layer re-growth and a work function shift toward mid gap. copyright The Electrochemical Society.