Process dependence of the SiO2/Si(100) interface trap density of ultrathin SiO2 films

Abstract

The interface trap density of states Dit of ultrathin SiO2 film has been investigated as a function of process variables. The process parameters used were oxidation temperature (1000–1200 °C), oxide thickness (4–10 nm), and annealing condition, including ambient (deuterium, argon, and in vacuum), temperature (500 and 900 °C), and time (10–120 s). Analysis of as-grown SiO2 films showed that the Dit decreases with increasing oxidation temperature and/or oxide thickness. With annealing in argon or in vacuum at 900 °C, the Dit decreases exponentially at the initial stage, then starts to increase linearly with increasing time. Similar behavior was observed for 900 °C deuterium annealing. Deuterium annealing at 500 °C was more effective in the reduction of the Dit, whereas argon annealing at the same temperature did not affect the density at all. A possible model for annealing kinetics is proposed to explain the experimental results.