Evaluation of Interface SiOx Transition Layer in Ultrathin SiO2 Film by Oscillatory Tunneling Current-Voltage Characteristics in Photo-CVD SiO2-Si Diode

Abstract

The interface transition layer in ultrathin SiO2 film is characterized by analyzing the oscillatory tunneling current. SiO2 thin films are deposited on atomically flat Si at low temperature (300°C) by photo-induced chemical vapor deposition (photo-CVD) and their electrical characteristics are investigated. The electrical characteristics of the SiO2/Si diode are improved by annealing in O2 atmosphere under ultraviolet irradiation, and the current becomes small and equivalent to that of a thermally grown oxide. Tunneling current through the ultrathin gate oxide is observed to exhibit oscillatory behavior in the Fowler-Nordheim (FN) tunneling region, which results from the interference of the incident and reflected electron waves at the SiO2/Si interface. It is clarified from theoretical calculation of the tunneling current that the amplitude and phase of the oscillatory current are strongly affected by the transition layer thickness. It is concluded that the interface transition layer of photo-CVD SiO2 film is thinner than that of thermally grown SiO2 film from analysis of the amplitude of the oscillatory profile.