PROCESS DEPENDENCE OF THE SIO2/SI(100) INTERFACE TRAP DENSITY OF ULTRATHIN SIO2-FILMS

The interface trap density of states D(it) of ultrathin SiO2 film has been investigated as a function of process variables. The process parameters used were oxidation temperature (1000-1200-degrees-C), oxide thickness (4-10 nm), and annealing condition, including ambient (deuterium, argon, and in vacuum), temperature (500 and 900-degrees-C), and time (10-120 s). Analysis of as-grown SiO2 films showed that the D(it) decreases with increasing oxidation temperature and/or oxide thickness. With annealing in argon or in vacuum at 900-degrees-C, the D(it) decreases exponentially at the initial stage, then starts to increase linearly with increasing time. Similar behavior was observed for 900-degrees-C deuterium annealing. Deuterium annealing at 500-degrees-C was more effective in the reduction of the D(it), 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.