Inhibition of tin whisker by electroplating ultra-thin Co-W amorphous barrier layer

Selecting suitable barrier layer material is one of the crucial issues for solder microbump in advanced interconnect metallization. In this work, the inhibiting effect of two barriers, Co-W and Ni, on tin whisker growth in high temperature and humidity environment (55 °C/85% RH) were studied. Low-cost electrodeposition was conducted to prepare the 200 nm amorphous Co-W barrier layer on Cu substrate. Compared with the Ni barrier layer, the amorphous Co-W barrier layer can effectively reduce the formation of intermetallic compounds during the storage process, suppressing the growth of tin whiskers and oxidative corrosion. Based on experimental results and inner stress calculation, the mitigation mechanisms of tin whisker growth within the two barrier layers were proposed, respectively, which are of great importance to further understand the behavior of tin whisker mitigation.