Thermal instability of low voltage power-MOSFETs

Anomalous failures occurred inside the theoretical Forward Biased Safe Operating Area of the last generation low voltage Power MOS devices are reported and analyzes. The paper outlines as some technology improvements, while increasing the current capability, can induce thermal instability phenomena at low drain currents. In the paper it is demonstrated that the thermal instability is a side effect of the progressive scaling down. In latest devices, in fact, due to the high current capability, the rated current is obtained with a gate voltage very close to the threshold voltage. This afflicts the thermal stability of modern low voltage Power MOS devices that, although more efficient and compact, are less robust leading to more effective circuit design techniques.