Design and Fabrication of High Voltage Silicon Carbide Symmetric Blocking Switch for FREEDM Smart Grid

This research focuses on the development of symmetric blocking Silicon Carbide (SiC) power device for fault interruption devices (FID) of FREEDM smart grid. The high voltage SiC symmetric blocking bipolar switches can greatly simplify the power circuits and provide low forward voltages.;One of the most challenging aspects in developing a symmetric blocking device is to design an feasible edge termination technique for the SiC material. The Orthogonal Positive Bevel (OPB) termination formed by blade sawing was proposed to overcome all the fabrication difficulties in SiC processing. This concept has been experimentally verified by the fabrication of a 1kV symmetric blocking NPN structure that used conventional single-zone junction termination extension (JTE) for forward blocking and the OPB termination for reverse blocking.;As the power switches in the FID may need to withstand the short-circuit current for tens of microseconds, their current saturation capabilities are very important. In order to understand the limitations of SiC devices at short-circuit operation, the short-circuit behaviors of commercial 1200V class SiC MOSFET and normally-off SiC JFET have been studied and analyzed. It was found that the JFET gate structure is much more robust and more suitable for FID application due to preferably needed current saturation capability.;A 10kV Symmetric Blocking Field Controlled Diode has been designed using parameters based on the available 150mum P-epi wafer with TCAD tools. A novel buried 3-zone JTE was designed for forward blocking and the OPB termination for reverse blocking.