Bias-dependent MOS transistor thermal resistance and non-uniform self-heating temperature

The relationship of the biasing condition and the self-heating effect of a multi-channel metallic oxide semiconductor field effect transistor (MOSFET) device was examined using various channel currents ranging from triode to saturation regimes. When temperature non-uniformity is generated due to transistor self-heating, the local thermal resistance is conventionally defined through the difference between the hottest local temperature and the backside temperature. It was found that the thermal resistance independence of the input power is only valid if we take into consideration the size and shape change of the heating body. We show in this paper the evolution of MOSFET self-heating through both direct thermoreflectance imaging observation and a three-dimensional analytical heat dissipation model of the device. The device thermal resistance obtained can change by a factor larger than 5 for different drain-source voltages. Even in the saturation regime, the thermal resistance of the transistor can change by 50% as a function of the bias.