Study of 4H-SiC Superjunction Schottky Rectifiers with Implanted P-Pillars

Abstract:

This paper discusses the study of 4H Silicon Carbide (4H-SiC) Schottky rectifier structures based on the superjunction (SJ) principle. The effects of device geometry have been investigated to optimise the trade-off between breakdown voltage (V_BD), specific on-resistance (R_ON,SP), and the ion-implantation fabrication window, so ensuring the final design is practically realisable. In this study, both full-SJ and semi-SJ (SSJ) layouts improve the V_BD-R_ON,SP trade-off to below the 4H-SiC unipolar limit. In comparison to a conventional planar Schottky diode, full SJ structures, with p-pillars that traverse the full length of the n-drift region, have a 7x improvement in R_ON,SP for a 50-100 V reduction in V_BD. In comparison, the SSJ structure is composed with the combination of the SJ structure and an n-bottom assist layer (BAL), which adds 2-μm of n-drift below the SJ pillars. The SSJ structure demonstrates a 5x improvement in R_ON,SP for a 300 V increase in V_BD, for the same aspect ratio. Most favourably, the SSJ structure also has an ion-implantation processing window 60% higher than the full SJ device, offering better anti-charge-imbalance characteristics. In both full and semi layouts, a trench sidewall angled (α) at 80^o was considered optimal, resulting in a slightly higher V_BD and R_ON,SP, and a wider processing window, compared to vertical (90^o) sidewalls.

• Periodical: Materials Science Forum (Volume 963)
• Pages: 539-543
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.963.539
• Online since: July 2019
• Authors: G.W.C. Baker*, Chun W. Chan, Tian Xiang Dai, A. Benjamin Renz, Fan Li, Vishal Ajit Shah, Philip Andrew Mawby, Peter Michael Gammon
• Keywords: 4H-SiC, Schottky Barrier Diode, Semi-Superjunction, Superjunction (SJ)

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