An efficient metrology to sense micro-metal contamination in fine-pitch package

In the infant mortality (IM) experiment and the final test (FT) of IC reliability, the screening capability for the contaminated metal particles is generally over than the size, W × L ∼ 120 × 120 um
²
. For the smaller size of these metal particles in ICs, the IM test is inferior. Using an efficient test metrology combining the IM test and the soak test to stress the sampled SRAM (Static random access memory) ICs, the smaller contaminated metal size with scanning electron microscope was measured, about W × L = 15 × 120 um
²
. The composition of metal particle with energy-dispersive X-ray (EDX) in material analysis exhibited two main peaks attributed to manganese (Mn) and ferrum (Fe). In speculation, the humidity effect after the soak test provided the electro-chemical reaction environment between two neighboring IC pins, spacing 130 um, in the fine pitch package. The IM test enhancing the electrical field accelerated this electro-chemical reaction. Therefore, even though the smaller contaminated metal particles exist, they with the double-combination test still can be screened out. Due to this effort, the risk selling ICs to customers is tremendously reduced. The assembly houses after information feedback are able to trace the root causes in production line and improve the package yield.