Investigations on mesa width design for 4H–SiC trench super junction Schottky diodes**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFB0400502) and the National Natural Science Foundation of China (Grant Nos. U1766222 and 51777187).

Abstract

Mesa width (WM) is a key design parameter for SiC super junction (SJ) Schottky diodes (SBD) fabricated by the trench-etching-and-sidewall-implant method. This paper carries out a comprehensive investigation on how the mesa width design determines the device electrical performances and how it affects the degree of performance degradation induced by process variations. It is found that structures designed with narrower mesa widths can tolerant substantially larger charge imbalance for a given BV target, but have poor specific on-resistances. On the contrary, structures with wider mesa widths have superior on-state performances but their breakdown voltages are more sensitive to p-type doping variation. Medium WM structures (∼ 2 μm) exhibit stronger robustness against the process variation resulting from SiC deep trench etching. Devices with 2-μm mesa width were fabricated and electrically characterized. The fabricated SiC SJ SBDs have achieved a breakdown voltage of 1350 V with a specific on-resistance as low as 0.98 mΩ·cm2. The estimated specific drift on-resistance by subtracting substrate resistance is well below the theoretical one-dimensional unipolar limit of SiC material. The robustness of the voltage blocking capability against trench dimension variations has also been experimentally verified for the proposed SiC SJ SBD devices.