Characterization of rapid thermally nitrided SiO2/Si interface by the conductance technique

Abstract

Device quality SiO2 films with a thickness of 15 nm have been thermally nitrided in NH3 by a rapid thermal processing technique. The properties of the interface between these films and a Si substrate have been investigated by a conductance technique. The results show that the nitridation increases the density and time constant of interface states and enhances the fluctuation of surface potential, but changes the hole capture cross section only slightly. Specifically, nitridation introduces a peak of interface states at 0.25 eV below midgap and the energy dependency of hole capture cross section is suppressed. Using a patchwork model, the surface potential fluctuation can be well simulated and a surface charge nonuniformity with a long-wavelength distribution may exist. These are consistent with the fact that nitridation induces a high oxide charge density. Experimental data show that all these properties depend on nitridation time and temperature.