Accurate temperature estimation in large DMOS transistors using a semi-empirical thermal conductivity model

A method for improving the temperature estimation accuracy in large DMOS transistors based on a semi-empirical fitting model for the Si thermal conductivity is presented. The model is used in the analytical solution of the 3D transient heat equation. The performances of the method are further improved by taking into account the power metallisation using a simple RC thermal model. Measurement results show that using this approach, not only the peak temperature, but also the temperature distribution across the device are accurately estimated.