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 SiO 2 /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 (HNO 3 ) and water (H 2 O) 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 HNO 3 and H 2 O vapor at various heating temperatures (708C, 908C and 1108C) of HNO 3 solution has been introduced in this work. Findings -It has been revealed that the samples annealed in HNO 3 þ H 2 O vapour ambient by various heating temperatures of HNO 3 solution; particularly at 1108C 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 HNO 3 solution increases, which is mainly attributed due to the significant reduction of carbon content at the SiC/SiO 2 interface by CvN passivation and CO or CO 2 out-diffusion. Originality/value -Despite being as a strong oxidizing agent, vaporized HNO 3 can also be utilized as nitridation and hydrogen passivation agent in high temperature thermal oxidation ambient and these advantages were demonstrated in 4H-SiC.

The Modelling of SiC Gate Oxide Thickness based on Thermal Oxidation Temperatures and Durations for High-Voltage Applications

“…Gate oxide thickness is thicker in samples treated under wet nitration conditions than under other circumstances. The oxidation rate is significantly higher when HNO3 and H2O vapour are used together during oxidation than when H2O vapour is used alone [15,20,47]. Hydrogen peroxide (H2O2) and H2O passivate Si and C dangling bonds more quickly than dry oxidation and passivate oxycarbide bonds.…”

“…N2O and NO passivate Si dangling bonds and eliminate oxycarbides linkages. However, too much nitrogen accumulation at the interface tends to lower the growth site concentration [20,48].…”

“…However, nitrogen accumulation in the interface region slows the formation of subsequent oxides in SiC, so nitrogen incorporation must be optimized to prevent too much nitrogen from accumulating at the interface region [18,19]. However, oxidation procedures like annealing and growing oxides in diluted N2O increase the reliability of gate oxides [20]. Nonetheless, the response times are really long.…”