Optimization of 1700-V 4H-SiC Semi-Superjunction Schottky Rectifiers With Implanted P-Pillars for Practical Realization

Abstract

A class of vertical 1700 V 4H-silicon carbide (SiC) semi-superjunction (SJ) Schottky diodes have been simulated and optimized to ensure practical and cost-effective realization. The proposed structures could be realized using an n-type drift region of 9-μm and etching trenches partway through this region to form the required mesa regions. P-pillars are then created through implantation into both the trench sidewalls and trench bottom. This semi-SJ topology overcomes problems with conventional SJs that span the full drift region (full-SJs), namely a narrow charge-balance window required to achieve the maximum VBD, and hard, snappy, switching characteristics. The optimized SiC semi-SJ comprises a 7-μm SJ region above 2-μm of conventional drift region. An angled trench sidewall (α), 10° off vertical, introduces a graded charge profile throughout the n-pillar, which widens the implantation window by 34%, while maintaining a VBD of 2.1 kV and a RON, SP comparable to a vertical full-SJ. Further advantages of the proposed semi-SJ, over a full-SJ, include a reduced trench aspect ratio and two orders of magnitude lower leakage current. Furthermore, the graded charge profile in the n-pillar gradually depletes the drift region, suppressing ringing and reducing the peak reverse recovery current by 50%.