Advancements in failure analysis have been made in root cause determination and stress testing methods of capacitors with extremely small (approximately 200 nm) defects. Subtrac-tive imaging has enabled a non-destructive means of locating a capacitor short site, reducing the FIB resources needed to analyze a defect.
Along with short circuit failure as a result of electrical over stress, open circuit failure resulting from corrosive damage is a relatively common event. The capacitor must be manufactured in a very clean environment to prevent contamination with any ionic species which might promote corrosion of the metal film.
Capacitor defects significantly contribute to infant and latent failures in integrated circuits. This paper will address methods of locating capacitor defects and root cause determi-nation. Keysight Technologies’ failure analysis team investigated tens of failures in an externally purchased voltage controlled oscillator (VCO).
In time these corrosive species can damage capacitors by removing film metallization, and occasionally the corrosion isolates the film from the end metallisation causing a complete open circuit failure, possibly involving overheating as the ESR increases during the failure process. Fig. 2. MPPF capacitor schematic
Therefore, failure analysis of integrated capacitors is the key to identify the root cause but, on some cases, is also a challenging task. Three case studies were discussed that includes the FA approaches and techniques that were utilized to understand the defect sites.
The failure mode of electrolytic capacitors is relatively slow and manifests over periods of months rather than seconds which can be the case with short circuit capacitor failure modes. Therefore condition monitoring may be practical and useful for these components.