Plasma Nitridation of HfO2 Gate Dielectric on p-GaAs Substrates

Abstract

Plasma nitridation (PN) method has been used for nitrogen incorporation in HfO2 based gate dielectrics for future GaAs-based CMOS devices. It has been demonstrated that the introduction of nitrogen in HfO2 on p-GaAs improves the interface quality and bulk oxide properties. X-ray photoelectron spectroscopy and transmission electron microscopy results show that the plasmanitridation of HfO2 effectively suppresses the interfacial oxide formation and elemental out diffusion of As during thermal treatment. Such suppression of out-diffusion led to a substantial enhancement in the overall dielectric properties of the HfO2 film. It has been found that the metal-oxide-semiconductor device characteristics such as interface-state-density, accumulationcapacitance, hysteresis, and leakage current improve for nitrided HfO2 films on p-GaAs. An equivalent-oxide-thickness of 3.5 nm and leakage current density of 10-6 Acm-2 has been achieved at VFB -1 V, for nitrided-HfO2 films. In addition, the effects of nitrogen in HfO2 on band alignments have also been studied.