Effects of wet-oxidized 4H-SiC annealed in HNO3/H2O vapour

Abstract

Purpose – The high density of defects mainly attributed to the presence of silicon oxycarbides, residual C clusters, Si- and C-dangling bonds at or near the SiO2/SiC interface degrades the performance of metal-oxide-semiconductor (MOS) devices. In the effort of further improving the quality and enhancement of the SiC oxides thickness, post-oxidation annealed by a combination of nitric acid (HNO3) and water (H2O) vapor technique on thermally grown wet-oxides is introduced in this work. The paper aims to discuss these issues. Design/methodology/approach – A new technique of post-oxidation annealing (POA) on wet-oxidized n-type 4H-SiC in a combination of HNO3 and H2O vapor at various heating temperatures (70°C, 90°C and 110°C) of HNO3 solution has been introduced in this work. Findings – It has been revealed that the samples annealed in HNO3 + H2O vapour ambient by various heating temperatures of HNO3 solution; particularly at 110°C is able to produce oxide with lower interface-state density and higher breakdown voltage as compared to wet-oxidized sample annealed in N2 ambient. The substrate properties upon oxide removal show surface roughness reduces as the heating temperature of HNO3 solution increases, which is mainly attributed due to the significant reduction of carbon content at the SiC/SiO2 interface by C=N passivation and CO or CO2 out-diffusion. Originality/value – Despite being as a strong oxidizing agent, vaporized HNO3 can also be utilized as nitridation and hydrogen passivation agent in high temperature thermal oxidation ambient and these advantages were demonstrated in 4H-SiC.