X-ray computed tomography for nano packaging - a progressive NDE method

The challenge of nano-packaging requires new nondestructive evaluation (NDE) techniques to detect and characterize very small defects like transportation phenomenon, Kirkendall voids or micro cracks. Imaging technologies with resolutions in the sub-micron range are the desire. High end semiconductor industries today deal with functional structures down to 32 nm and below. ITRS roadmap predicts an ongoing decrease of the "DRAM half pitch" over the next decade. Nano-packaging of course is not intended to realize pitches at the nanometer scale, but has to face the challenges of integrating such semiconductor devices with smallest pitch and high pin counts into systems. System integration (SiP, SoP, Hetero System Integration etc.) into the third dimension is the only way to reduce the gap between semiconductor level and packaging level interconnection. To control the necessary technologies a selection of suitable and effective non-destructive evaluation methods is absolutely vital. The task of these methods is not only to identify any impurities on the package surface, but also to look as deep as possible into the package volume. Available non-destructive evaluation methods (NDE) for such kind of packaging are for example X-ray microscopy, X-ray computed tomography, ultrasonic microscopy and thermal microscopy. The paper will focus on X-ray nano focus computed tomography. It will discuss the potentials and limits of X-ray NDE techniques and the sample preparation, illustrated by the investigation of a complete system in package device (SiP). More examples like cracks in solder joints, vias in PCBs and interposers, realized with voxel sizes from 10 μm down to 800 nm have already been presented by us at last year's EPTC (see &).