The results presented here show how high-speed simultaneous EBSD and EDS can be used to characterize the essential microstructural parameters in SnPb solder joints with high resolution and precision. Analyses of both intact and failed solder joints have been carried out. Regions of strain localization that are not apparent from the Sn and Pb phase distribution are identified in the intact bond, providing key insights into the mechanism of potential bond failure. In addition, EBSD provides a wealth of quantitative detail such as the relationship between parent Sn grain orientations and Pb coarsening, the morphology and distribution of IMCs on a sub-micron scale and accurate grain size information for all phases within the joint. Such analyses enable a better understanding of the microstructural developments leading up to failure, opening up the possibility of improved accelerated thermal cycling (ATC) testing and better quality control.

Solder bulging is detected on the exposed paddle of Device A after burn-in causing the affected units to fail the coplanarity criteria. The affected units show up at random burn-in board socket locations and occur with varying frequency. Potential causes are plotted through an Ishikawa diagram which reveal fusion and creep as the potential mechanisms behind the solder bulging phenomenon. This paper seeks to determine the mechanism behind the solder bulging phenomenon via a 2-step metallographic investigation through (i) material deformation characterization and (ii) deformation mechanism simulation. In material deformation characterization, visual inspection on affected units show that the solder bulge is generally circular and is located on the center of the exposed paddle. Moreover, SEM/EDX analysis reveal that the solder bulge is not caused by a foreign contaminant or a compositional anomaly in the solder plating. On the other hand, deformation mechanism simulation involves the metallographic comparison between controlled simulations of fusion and creep versus the actual unit with solder bulge. Metallographic inspection reveal that the grain size and grain shape of the solder bulge possess the characteristics of creep phenomenon. Additionally, investigation on the burn-in (BI) process conditions also supports creep over fusion as the mechanism behind the solder bulging phenomenon. The static stress induced by the socket on the package at elevated temperature caused the solder plating to creep towards the free area which is the hole on the bottom of the socket.

Since the introduction of copper metalization into mainstream semiconductor processes, new backend debug and failure analysis techniques are needed to deal with the different reaction rate and milling behavior of copper. Focused Ion Beam (FIB) systems have long been a major tool in debug and analysis of semiconductor chips. With the introduction of copper, many of the current FIB chemistries and techniques will need to be modified in order to accommodate this process. The metal etch gases currently in most FIB systems either have no effect on copper or have detrimental effects. Chlorine, iodine and bromine all will etch copper spontaneously and will undercut exposed copper lines. [1,2] The ion channeling properties of copper are also significantly greater than aluminum, which makes large area metal removal very difficult due to differential milling rates. Depending on the crystallographic grain orientation, straight sputter of copper could have up to 3 times differential milling rates. Various other FIB function will also need to be examined with regard to copper. This paper will discuss the differences in dealing with copper instead of aluminum chips. It will also offer a few application techniques and new system enhancements in dealing with copper and discuss some limitation of the current system hardware. [1]

The time delayed failure of a mesa diode is explained on the basis of dendritic growth on the oxide passivated diode side walls. Lead dendrites nucleated at the p+ side Pb-Sn solder metallization and grew towards the n side metallization. The infinitesimal cross section area of the dendrites was not sufficient to allow them to directly affect the electrical behavior of the high voltage power diodes. However, the electric fields associated with the dendrites caused sharp band bending near the silicon-oxide interface leading to electron tunneling across the band gap at velocities high enough to cause impact ionization and ultimately the avalanche breakdown of the diode. Damage was confined to a narrow path on the diode side wall because of the limited influence of the electric field associated with the dendrite. The paper presents experimental details that led to the discovery of the dendrites. The observed failures are explained in the context of classical semiconductor physics and electrochemistry.