Fabrication and microstructure evolution of preferred oriented nanotwinned copper by pulse electroplating for RDL in WLP

Nanotwinned copper is drawing widely attention for it simultaneously demonstrates high strength, high ductility, and high conductivity. It will be very beneficial to microelectronics in many respects, one of which is redistribution layer in wafer level packaging. We take advantage of (111) preferred oriented nanotwinned copper to fabricate 2-poly-1-metal (2P1M) redistribution layer in wafer level packaging. Nanotwinned copper was deposited by pulsed electroplating. Texture of copper can be controlled by seedlayer, thickness of films, or patterns, and texture can be observed by X-ray diffraction. Microstructure and the evolution of copper after annealing were studied by focused ion beam, scanning electron microscopy, and transmission electron microscopy.