Correlation of Interface Characteristics to Electron Mobility in Channel- implanted 4H-SiC MOSFETs

To study mobility limiting mechanisms in (0001) 4H-SiC, lateral n-channel MOSFETs in p-implanted wells on n-type epitaxial layers were manufactured and additionally selectively shallow implanted with different nitrogen (N) doses in the channel region. The mobility was found to be limited by Columbic scattering at low electric fields. Further surface roughness scattering was considered as a possible mobility degradation mechanism at high electric fields. First investigations of the SiC surface by atomic force microscopy (AFM) in the channel region after implantation, annealing, and gate oxide removal revealed a rather rough topology. This could lead to fluctuations in the surface potential at the SiC/SiO2 interface, thus accounting in part for surface roughness scattering.