High voltage P-N junction diodes in silicon carbide using field plate edge termination

In this paper, we report the successful use of field plates as planar edge terminations for P+-N as well as N+-P planar ion implanted junction diodes on 6H- and 4H-SiC. Process splits were done to vary the dielectric material (SiO2 vs. Si3N4), the N-type implant (nitrogen vs. phosphorous), the P-type implant (aluminum vs. boron), and the post-implantation anneal temperature. The nitrogen implanted diodes on 4H-SiC with field plates using SiO2 as the dielectric, exhibited a breakdown voltage of 1100 V, which is the highest ever reported measured breakdown voltage for any planar ion implanted junction diode and is nearly 70% of the ideal breakdown voltage. The reverse leakage current of this diode was less than 1 x 10(-5) A/cm(2) even at breakdown. The unterminated nitrogen implanted diodes blocked lower voltages (similar to 840 V). In contrast, the unterminated aluminum implanted diodes exhibited higher breakdown voltages (similar to 800 V) than the terminated diodes(similar to 275 V). This is attributed to formation of a high resistivity layer at the surface near the edges of the diode by the P-type ion implant, acting as a junction termination extension. Diodes on 4H-SiC showed higher breakdown than those on 6H-SiC. Breakdown voltages were independent of temperature in the range of 25 degrees C to 150 degrees C, while the leakage currents increased slowly with temperature, indicating surface dominated components.