INTERFACE CHARACTERISTICS OF METAL-OXIDE-SEMICONDUCTOR CAPACITORS WITH ULTRATHIN OXIDES

MOS structures were fabricated on single-crystal as well as polycrystalline silicon. Oxidation was carried out in dry oxygen at 1000 and 1100-degrees-C. No annealing was performed either after oxidation or after metallization. The oxide thickness ranged between 35 and 490 angstrom. Admittance-voltage-frequency measurements were made on a large number of nonleaky structures to obtain the interface charge density at flatband and the interface state density vs. bandgap energy profile. As the oxide thickness increased, both the interface state density and the flatband interface charge density first decreased and then went through a maximum. The oxidation rate was also found to undergo a changeover at the same value of the oxide thickness. The observed correlation between the oxidation rate and the interface defects underscores the need to take into account the influence of the interface charge density and the built-in interfacial potential, while formulating a model for the oxidation kinetics of the initial phase.