Optimization of 1700-V 4H-SiC Semi-Superjunction Schottky Rectifiers With Implanted P-Pillars for Practical Realization
G.W.C. Baker, Peter Michael Gammon, Arne Benjamin Renz, Oliver James Vavasour, C.W. Chan, Yunyi Qi, Tian Xiang Dai, Fan Li, L. Zhang, Viren Kotagama, Vishal Ajit Shah, Philip Mawby, Marina Antoniou
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- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {BD}}$ </tex-math></inline-formula> , and hard, snappy, switching characteristics. The optimized SiC semi-SJ comprises a 7- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> SJ region above 2- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> of conventional drift region. An angled trench sidewall ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> ), 10° off vertical, introduces a graded charge profile throughout the n-pillar, which widens the implantation window by 34%, while maintaining a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {BD}}$ </tex-math></inline-formula> of ~2.1 kV and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ \mathrm{\scriptscriptstyle ON},\text {SP}}$ </tex-math></inline-formula> 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%.