Modeling, simulation and validation of the electro-thermal interaction in power MOSFETs

Nowadays, power MOSFETs are massively used in most low and medium voltage power applications. Particularly, they are increasingly employed in automotive Smart Power switches enhancing energy efficiency, safety and comfort in latest generation cars. The electro-thermal interaction observed in power MOSFETs is the driving cause of thermal instability, which substantially limits their SOA, hence their robustness. A 3-D FEM-based electro-thermal simulation technique has been developed and implemented in order to predict device behavior under critical operating conditions experienced in the harsh automotive environment. Simulation requires an appropriate prior electro-thermal modeling of the device elementary cell. Experimental measurements with opportune test devices have been performed to validate the electro-thermal simulator. Furthermore, an innovative modeling strategy for the epitaxial layer of a trench power MOSFET has been developed and studied. Finally, the novel FEM tool has been profitably used to analyze currently relevant issues in modern power MOSFETs, such as the impact of their technological shrinking trend on device robustness.