ELECTRONIC STATES AT SI-SIO2 INTERFACE INTRODUCED BY IMPLANTATION OF SI IN THERMAL SIO2

Interface traps due to excess Si introduced into the SiSiO2 system by ion implantation are investigated. Implanted oxides are shown to have interface traps at or slightly above the Si conduction band edge with densities proportional to the density of off-stoichiometric Si at the SiSiO2 interface. Diluted oxygen annealing is shown to result in physical separation of interface traps and equilibrium substrate electrons, demonstrating that "interface" states are located within a 0.5 nm thick layer of SiO2. Possible charge trapping mechanisms are discussed and the effect of these traps on MOS transistor characteristics is described using a sheet charge model. © 1990.