Thermal instability of low voltage power-MOSFETs

Anomalous failures which occurred inside the theoretical forward biased safe operating area of the latest generation low voltage power MOS devices are reported and analyzed. The paper outlines how some technology improvements, while increasing the current capability, can induce thermal instability phenomena at low drain currents. It is demonstrated that the thermal instability is a side effect of the progressive scaling down. In the 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 affects 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