An Inclusive Structural Analysis on the Design of 1.2kV 4H-SiC Planar MOSFETs

Abstract

A detailed structural analysis of 1.2 kV 4H-SiC MOSFETs with accumulation mode channel is reported in this paper. 1.2 kV SiC MOSFETs with a variety of cell designs were fabricated and compared with respect to the output and transfer characteristics, and blocking behaviors. All the design rules, such as channel length, JFET width, contact openings, gate-to-source overlap, and cell pitch were investigated to clearly provide the quantitative impact on the static performances. 2D-simulation was also conducted to support experimental results. As a result, it turned out that the channel length is the most determining factor for the specific on-resistance, resulting in 0.364 $\text{m}\Omega $ -cm2 increase per $0.1~ {\mu }\text{m}$ increase in the channel length. However, the channel potential is also largely dependent on the channel length such that the leakage current tends to increase with short channel design. The enhanced doping in the JFET region with a current spreading layer (CSL) is essential for achieving a narrower JFET width, which satisfies all static performances, as well as device reliability and ruggedness. Methods to further improve the trade-off characteristics using other design aspects are discussed in this paper.

Keywords

• Silicon Carbide
• 4H-SiC
• MOSFET
• current spreading layer (CSL)
• 2D-simulation
• design consideration