Passivation of the SiC gate-oxide interface using remote microwave plasmas

A well-known challenge in fabricating a SiC MOSFET switch is attaining a low density of defects on the gate oxide/SiC interface. The typical high temperature thermal oxide process leaves carbon impurities at the SiC/SiO$_2$ interface which cause high densities of defect states. The result is a decrease in channel conductivity, thus decreasing device efficiency. We have investigated two approaches to this problem involving treatment with atomic species generated by remote microwave plasma. First, a plasma passivation technique was analyzed employing atomic nitrogen to extract the carbon impurities from the interface. Second, an O$_2$ plasma was used to grow an initial highly-structured SiO$_2$ layer on the SiC surface using a low temperature slow-growth process. Results will be presented including the effects of these plasma processes on SiC MOSFET optimization along with the role that atomic nitrogen and oxygen plays in each plasma process.