High Temperature Modeling and Characterization of 6H SiC MOSFETs

(Abstract) SiC offers the potential to provide high power, high temperature electronics. Our two-dimensional is used to model the current voltage characteristics of a 6H-SiC MOSFET as a function of temperature, from 25C to 200C. (Intro) In our previous paper[1], we developed a new detailed mobility model for Silicon Carbide (SiC) MOSFETs. The new model explicitly accounts for the contribution of ionized impurities, surface phonons, interface states and surface roughness scattering, as well as high fields as a function of position and temperature. We then used numerical methods to design a new two-dimensional device simulator specifically for SiC MOSFETs. The new device simulator was based on the drift-diffusion model of carrier transport. Using the new simulator, we demonstrated agreement of the model predictions and measurements for 6H SiC MOSFETs at room temperature only. In this communication, we expand upon our previous work by applying our device model to MOSFETs operating at high temperatures. We compare the model predictions with the actual device measurements from room temperature to 200C. From the combined use of the model and experiment, we present a quantified description of the role of temperature-dependent interface trap occupation and its effect on SiC MOSFET operation. (Method) We experimentally characterized 4μm 6H SiC MOSFETs[1] at room temperature, 100 and 200C. One interesting feature was that as the temperature increases, the measured drain current increased, and the threshold voltage decreased. Other researchers reported similar results[2]. Of course, this is contrary to what is normally observed in standard silicon devices. In this work we explain this behavior by relating temperature dependent device performance to mobility and interface state charging. Using Matheson’sxxx rule the inverse of the total low-field mobility can be written as the sum of the inverses of the individual mobility mechanisms.