Thermal effects and electro-thermal modeling in power bipolar transistors

Dynamic electro-thermal instabilities of power devices are presented and discussed. These analyses have been made with the aim of examining hot spot onset in power cellular transistors. The temperature distributions are obtained by means of a 3D electro-thermal simulator, and the numerical results are compared with experimental dynamic thermal maps, detected by direct IR radiometric measurements with high spatial and high time resolution. By analyzing both experimental and numerical electrothermal instabilities on power cellular BJTs, we have found that the time dependent thermal distribution is a function of the device under simulation (DUS) layout and also that it is a strong function of the single cell temperature dependent current gain and the thermal interaction between the neighbouring cells.