Design and Optimization of SiC Super-Junction MOSFET Using Vertical Variation Doping Profile

In this paper, uniformly doped drift region of silicon carbide (SiC) super-junction (SJ) MOSFET is replaced with vertical variable doping profile (VVD) to achieve a better tradeoff between breakdown voltage (BV) and specific ON-resistance (R _sp,on ). While it is known that the SJ device consists of two vertical columns of nand p-type, SJ VVD feature lies in increasing the doping concentration from top to bottom in the N-column and viceversa in the P-column within the drift region. The proposed SJ VVD allows Rsp, on to reduce further due to increased average doping concentration in conducting N-column and BV to increase further due to shifting of an electric field from corners to the center of the drift region. BV and Rsp,on improved by 10% in an SJ VVD MOSFET and these parameters follow linear relationship similar to SJ MOSFET. The 2-D numerical simulations from Synopsys TCAD are used for investigating the static and dynamic characteristics of the device. In addition to 30% improvement in Baliga figure of merit, 35% improvement is obtained over SJ MOSFET in turn on and turn off switching energies for a clamped inductive circuit at 1200 V-20 A. Improved dynamic characteristics of SJ VVD can be attributed to reduction in gate charge (Q _g ) and miller capacitance (c _rss ) compared to SJ MOSFET.