Optimization Design of Isolation Rings in Monolithically Integrated 1200V SiC Transistor and Antiparallel Diode for Improved Blocking Voltage

Abstract

Monolithic integration of antiparallel diode with power transistor offers unique advantages for wide bandgap (WBG) power devices. However, the blocking voltage degradation issue stands in the way in the development of the integrated devices. This paper presents the design, fabrication, and verification of a monolithically integrated SiC BJT and antiparalleled junction barrier Schottky (JBS) diode (BJT/JBS), which has achieved a blocking voltage very close to that of the individual transistor or diode. It introduces isolation rings into the border region, separating the transistor and diode. The design was first validated successfully by TCAD simulations, and then some integrated device samples were fabricated to experimentally verify the feasibility of the isolation rings in improving their blocking voltages. Besides, the fabrication of the 4H-SiC-integrated BJT/JBS switch adopted a single metal, single thermal treatment process to form ohmic contacts on p+ regions and Schottky contacts on the N-epilayer simultaneously. Hence, there was not any additional step added to the SiC BJT baseline process. A breakdown voltage of 1340 V at a leakage current of 10 $\mu \text{A}$ is experimentally observed, and the simulation results and design optimization are discussed.