Multizone Gradient-Modulated Guard Ring Technique for Ultrahigh Voltage 4H-SiC Devices With Increased Tolerances to Implantation Dose and Surface Charges

Abstract

An area efficient multizone gradient-modulated guard ring (MGM-GR) edge termination technique is proposed, fabricated, and analyzed for 10-kV class silicon carbide devices without extra process steps or masks, which provides a better tradeoff between near ideal blocking capabilities and technological process complexity. The edge termination region is divided into multiple zones by employing MGM-GR technique, which forms a similar linearly graded doping profile to relieve the amount of electric field crowding at the periphery of the active area and achieve a maximum blocking voltage with wide tolerance to implantation dose. The proposed device shows not less than a 35% reduction in edge termination area in comparison with a conventional equally spaced ring at a breakdown voltage of 10 kV. Moreover, MGM-GR shows good tolerances to breakdown voltage for total implant dose and interface charges. With the application of MGM-GR technique to SiC MOSFET with a 100- $\mu \text{m}$ -thick N− epilayer doped to $5 \times 10^{14}$ cm $^{-3}$ , the measured breakdown voltage is 13.6 kV at $10~\mu \text{A}$ . This voltage is nearly 95% of the theoretical value calculated for a 1-D structure. Simulated and measured characteristics show that MGM-GR structure is a candidate for an ultrahigh voltage power device to maximize power density and driving down system complexity.