High Voltage P-N Junction Diodes in Silicon Carbide Using Field Plate Edge Termination

Abstract

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 1×10⁻⁵ A/cm² even at breakdown. The unterminated nitrogen implanted diodes blocked lower voltages (~840V). In contrast, the unterminated aluminum implanted diodes exhibited higher breakdown voltages (~80OV) than the terminated diodes (~275V). 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 °C to 150 °C, while the leakage currents increased slowly with temperature, indicating surface dominated components.