A special failure analysis process to save some de-caped recovered cases

For some High power analog ICs, with a failure mode that some high side MOSFETs could not be turned on, they recovered after de-capsulation by fuming nitric acid, which resulted in the undetermined failure root cause. A hypothesis was proposed that there may be a foreign matter inducing gate short source in a high side MOSFET in the power die as there is no passivation covered the MOSFET. For confirming this hypothesis and avoiding recovering, a special failure analysis process was employed in a couple of cases. The hypothesis was confirmed and the failure mechanism was revealed thanks to this special failure analysis process.