Difficulties of the microscopic theory of leakage current through ultra‐thin oxide barriers: point defects

Abstract

AbstractWe use a combination of first‐principles density functional theory and non‐perturbative scattering theory to investigate the effect of point defects on the hole leakage current through ultra thin oxide films. In particular, we consider O vacancies and B interstitial in monoclinic HfO2; five different defects are considered: (1) O vacancy at a three‐ and (2) a four‐coordinated O site located in the HfO2 region, (3) O vacancy along a Hf–O–Si bond and (4) along a Si–O–Si bond at the Si/HfO2 interface, and (5) an interstitial Batom in the HfO2 region. We find that the neutral bulk vacancies and an interface vacancy along theSi–O–Si bond have little impact on the leakage current. On the contrary, an interface vacancy along the Hf–O–Si bridge and an interstitial B atom in the HfO2 region introduce states in the Si band gap and in the region just below the Si valence band edge thus strongly enhancing the leakage current at a low bias. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)