Failure analysis defect localization of a metal stringer defect on a monolithic step-up DC-DC converter

There is a recent influx of failures on an automotive device particularly on a Monolithic Step-Up DC-DC Converter. Difficulty arises on the defect localization of the metal stringer since majority of the failing units have different electrical signatures wherein some returned units are failing at field, 0Km failure or failing at higher temperature which was either verified electrically failing at ATE (Automated Testing Equipment), curve trace verification or bench test simulation. This paper aims to show the different FA techniques particularly bench test verification, OBIRCH, Emission Microscopy, Micro probing, FIB and EDX which was utilized to pinpoint the exact failure mechanism. Also, on the wafer fabrication site, a root cause was put in place to minimize if not eliminate these kinds of failure.