FEM simulation approach to investigate electro-thermal behavior of power transistors in 3-D

A simulation approach is presented which can be used to investigate electro-thermal behavior of power transistors in variety of operating conditions. The approach is discussed in detail and demonstrated using ANSYS simulator. The power transistor is considered as a distributed voltage controlled resistor consisting of many in parallel connected cells. Because every cell has individual gate- and drain-source voltage, 3-D effects depending on geometric configuration and used materials can be observed. This is shown on a simple power transistor model for three principal electrical operating points: below TCP (temperature compensated point), at TCP and above TCP. Additionally, a mix-mode operating point is showed. The simulation results show 3-D effect of current density distribution as a function of the operating points. The results showed very good agreement with the prediction from the theory and already published results achieved by 3-D modeling approaches

ANSYS based 3D electro-thermal simulations for the evaluation of power MOSFETs robustness

Electro-thermal simulators are useful tools for introducing design and technology improvements during the design process of power MOSFET transistors. They are also helpful to predict the device behavior when operating under extreme electrical and temperature conditions and thus to predict its thermal robustness. Such simulators have to correctly take into account interactions between electrical and thermal behavior. In this paper we propose a new method to perform electro-thermal simulations of power MOSFETs using ANSYS simulator. The electrical and the thermal problem are fully coupled and iteratively solved using the FEM method. By means of a test chip, simulations and comparison with measurement have been performed in order to validate the simulation approach