Wire Boning Process Failure Risk Estimation of the Cu/low-k Structure using the Transient Finite Element

This research establishes a set of transient finite element models to represent the mechanical impacts during the w/b process [1]. Moreover, a finite element model of the BEOL structure, which consisted of 7 layers of copper metal stacks and an aluminum pad to represent the current frequent-used technology, is established to investigate the stress pattern. The results show that both the Cu/low-k design and the w/b process parameters, including the free-air ball (FAB) size and w/b capillary, influence the maximum stress of the Cu/low-k structure. It is suggested that the w/b process of Cu/low-k structure should be precisely controlled, compared to the conventional w/b process of the Al/SiO4 structure, to maintain the low stress level of the Cu/low-k structure.