High-resolution X-ray computed tomography of through silicon vias for RF MEMS integrated passive device applications

Micrometer-sized defects were non-destructively identified in some of the open TSVs (i.e. Cu plating thickness deviations, incomplete plating and large voids) using microfocus X-ray CT, which were then verified by destructive mechanical cross-sectioning. With high-resolution X-ray CT, which has almost an order of magnitude better resolution, (sub) micron-sized defects in TSVs were directly non-destructively identified and localized, without the need for further destructive inspection techniques for confirmation. The Cu plating thickness variations, in TSVs all connected to a large-area redistribution layer, were found to be design related; based on these failure analysis findings, a new electroplating procedure has been established.