Superior thermal stability of redistribution layer tailored by nanotwinned copper and the influence on wafer warpage

Nanotwinned copper has been got widely attention in microelectronics because it simultaneously demonstrate high strength, high conductivity, superior thermal stability, which makes it a very promising candidate to replace the position of common copper in the next generation of IC and packaging materials. The redistribution layer, a key process of wafer level packaging, was tailored by pulse electrodeposited nanotwinned copper in this paper. Quite different in-situ measured warpage characteristics was revealed during thermal cycling from room temperature to 300 °C, evidencing the superior thermal stability of nanotwinned copper. Further microstructure analyze proofed that irreversible twin boundary evolution rather than grain boundary evolution during annealing accounts for the thermal stability.