Reliability characterization of a soot particle sensor in terms of stress- and electromigration in thin-film platinum

In this work we present a systematic investigation of various failure mechanisms for thin-film platinum heater structures and interdigitated electrodes as components of a resistive type soot particle sensor. We study the role of stress-migration and electromigration and their interaction for the reliability of these sensors. The influence of a titanium adhesion layer and gases from the ambient atmosphere are also studied. Lifetime determination and optical and scanning electron microscopy are applied for samples which have experienced different load conditions to understand qualitatively and quantitatively the phenomena. The aim of this work is to enable time-to-failure prediction and thus provide guidelines for limiting temperature and current density in the actual sensor to ensure its stability over lifetime. We use dedicated, application-related test structures to ensure that the results are applicable to sensor lifetime estimations.