Investigation of SiC trench MOSFET with floating islands

Abstract

The silicon carbide trench metal-oxide-semiconductor field-effect transistors (SiC UMOSFET) with P + floating island (FLI) which shields the gate oxide at the bottom of the gate trench from the high electric field during the blocking state and enhances the breakdown voltage (BV), is presented in this study using two-dimensional simulations. The effects of doping concentration, length and position of FLI on BV, electric field distribution and specific on-resistance (R on,sp) are studied, thereby providing particularly useful guidelines for the design of this new type of device when considering the breakdown of the gate oxide layer. For the suitable device design, the results indicate that BV and Baliga figure of merit are, respectively, increased by 150 and 439% compared with a conventional SiC UMOSFET. At the same time, the SiC FLI UMOSFET has smaller gate-drain capacitance and better switching performance compared with the conventional UMOSFET on the condition of the same drift layer parameters. FLI introduced have almost no influence on the recovery characteristics of body diode.

Investigation of 3.3 kV 4H-SiC DC-FSJ MOSFET Structures

“…If the electric field is larger than the critical value, the MOSFET will break down. Therefore, the structure and parameters need to be well designed [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Figure 1 b shows a schematic diagram of a MOSFET with three floating P-type structures.…”

“…The simulation results show that the breakdown voltage of the MOSFET increases as the floating P-type structure becomes deeper in the epitaxial layer. By changing the depth of the floating P-type structure, the electric field extension is enhanced so that the breakdown voltage increases [ 20 , 21 , 22 ], as shown in Figure 2 . However, when the depth of the floating P-type structure exceeds 8 μm, as seen from the vertical electric field distribution, the electric field along the PN region shown in Figure 3 a and MOS region shown in Figure 3 b becomes uneven, leading to the slightly increasing breakdown voltage; this is because the distance between the structure and the P-well is too long.…”

SiC trench MOSFET with heterojunction diode for low switching loss and high short‐circuit capability

“…With its remarkable material property of wide band gap, the SiC MOSFET has been widely used in the power systems [1][2][3]. In addition to low power loss and high operation efficiency, the SiC MOSFET is also highly required to downsize chip size and improves the reliability.…”