Design and fabrication of high voltage 4H-SiC Schottky barrier diodes
A novel design of mesa-etch termination and Superjunction JBS diode structure has been proposed and optimized. The new mesa-etch termination can achieve over 90% of ideal maximal breakdown voltage within a wide sidewall implant dose window (~9e16 cm⁻³). Besides the high tolerance on implant dose, the proposed design also exhibits high tolerance on the etch sidewall angle: minimal maximum breakdown voltage was observed with etch sidewall angle variations. The Superjunction JBS diode can obtain both 96.4% maximum super junction breakdown voltage and 76.6% JBS Schottky surface electric field reduction. The super junction maximal breakdown voltage is 1.5 times large as the conventional Schottky diode breakdown voltage and the leakage current is logarithmically related to the surface electric field. The superior breakdown voltage represents a large improvement on the power rectifier performance. Based on these structure improvements, vertical 4H-SiC Schottky Diodes have been fabricated and tested. Vertical 4H-SiC Schottky Diode without any edge termination has a breakdown voltage as large as 692 V and exhibits an on-state specific resistance as small as 7.9 mΩ*cm². Such breakdown voltage is much higher than simulation results. In the meantime, on-state resistance is also much larger than the simulation results. The mechanism for these improved power rectifier performances will be furthered investigated in future studies.