Die-Level Series-Connection of SiC MOSFETs and Integration of Decoupling Capacitors

Abstract:
Series connection of Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) is a viable solution to design switches for voltages that are not yet commercially available or limited for single-die devices. However, the stray inductance in the current commutation loop is larger than a single high-voltage (HV) device, due to the electrical connections of the series-connected SiC MOSFETs. Thus, instead of serializing several discrete packaged devices or power modules, which introduce significant stray inductance, this paper introduces the design of a power module with die-level series-connected SiC MOSFETs. In order to demonstrate the feasibility of this approach, a direct bond copper (DBC) layout accommodating two series-connected 1.2 kV SiC MOSFET dies to form a 2.4 kV switch has been designed. Moreover, decoupling capacitors are integrated inside the module to mitigate high-frequency current and voltage oscillations. Characterization of the power module’s inductive layout is presented in terms of FEM simulations and measurements. Finally, the switching performance of the series-connected dies is presented experimentally at a blocking voltage of 1 kV.