Design and fabrication of high breakdown voltage 4H-SiC Schottky barrier diodes with floating metal ring edge terminations

In this paper, the use of floating metal ring (FMR) edge termination (ET) structure to improve breakdown voltage (VBD) 4H-SiC Schottky barrier diodes (SBDs) is reported. Influence of the FMR's parameters, such as the number and width of metal rings, the space between two neighboring metal rings, etc., on surface electric filed distribution and breakdown voltage were studied. Two-dimensional simulation results reveal that the induced potential voltage on FMR increases with decreasing the distance to the main electrode, which is beneficial to reduce surface electric field intensity. As compared to the diode without ET design, about 142% improvement in VBD of SBDs has been realized in SBDs with a 2-ring FMR ET structure. In experiments, the same Schottky metal including Al, Ti, Ni, and Au has been used for both the main electrode and FMR structure. 4H-SiC SBDs with 1-3 FMRs ET design have been successfully fabricated and VBD in the range of 476-1080 V has been achieved. Comparisons between the calculated and experimental results were made and a good agreement has been obtained.