(Invited) Requirements for Highly Accurate Multiphysics Modeling of SiC Power MOSFETs and Power Modules

Tuesday, 3 October 2017: 08:30
Chesapeake B (Gaylord National Resort and Convention Center)
U. Grossner, B. Kakarla, T. Ziemann, J. Muting, R. Stark, and I. Kovacevic-Badstuebner (ETH Zurich)
With the current needs towards achieving significantly higher power density and energy efficiency of power conversion, the industry is highly interested in replacing mature Silicon devices with the emerging Silicon Carbide (SiC)-based technology in the new generation of power electronics systems. Multi-physics modelling represents a very important design step used to evaluate and confirm the potential of SiC devices in a wide-range of power electronics applications before any prototypes are constructed. It enables a detailed assessment of SiC technology with respect to different performance aspects including dynamics, thermal capabilities, and robustness against abnormal operating conditions. As a prototypical example, this paper presents a highly accurate modelling procedure for analyzing short-circuit (SC) capabilities of a commercial SiC power MOSFET (80mΩ, 1.2kV). First, the actual MOSFET structure is modeled in Synopsys Sentaurus TCAD tool suite and calibrated to match the I-V and C-V MOSFET characteristics, taking into account the mobility degrading effects and interface states at the SiC/SiO2 interface. In the next step, TCAD mix-mode simulations are performed using the developed physical model to gain a better understanding of the design parameters like cell pitch, channel length and p-base doping concentration and their impact on the MOSFET SC and dynamic characteristics considering temperature dependencies and design constraints. Accordingly, a trade-off analysis between improved SC capabilities and a good MOSFET dynamic performance will be discussed, which can be further used as a guideline for developing an optimized MOSFET structure. Moreover, a detailed three-dimensional electromagnetic model of the SC measurement setup will be presented in order to identify the influence of the circuit parameters on the current profile of the Device-Under-Test (DUT) during the SC events and to optimize the measurement setup. For a comparison between the measured and simulated MOSFET waveforms, coupling of electrical and electromagnetic domains will be performed in LTSpice, Saber and TCAD mix-mode tool. As a result, this paper will demonstrate the accuracy of three device models side-by-side: the compact device model implemented in LTSpice, the behavioral model of Saber, and the TCAD numerical model. Finally, the paper emphasizes the requirements for a very accurate and efficient multi-domain modelling procedure that can be integrated in the overall development process of SiC power MOSFETs.

Fig. 1 A comprehensive analysis of short-circuit (SC) capabilities of a commercial SiC power MOSFET (80mΩ, 1.2kV) based on a multi-physics modelling approach.