Whisker growth in Sn and SnPb thin films under electromigration

• The growth of whiskers in Sn and SnPb thin films were systematically investigated.
• Fast whiskers growth was observed in the Sn thin film with small size of grain.
• The determined critical sample length for Sn whisker growth is about 82.2 μm.
• The addition of Pb is thought to inhibit the growth of need-like whisker effectively.

The growth of whiskers under electromigration in Sn and SnPb thin films deposited by magnetron sputtering were systematically investigated in this work. Fast whisker growth was observed in the Sn thin film which results from the small size of grain. And with decreasing the sample length or current density, both the mean length and density of the whiskers decrease in the Sn thin films. The determined critical sample length for Sn whisker growth is about 82.2 μm, which is larger than the value obtained in stripe samples. When Pb is added, three different layers form in the SnPb thin film. And due to the high sample temperature Pb becomes the dominant diffusion element. The addition of Pb is thought to inhibit the growth of need-like whisker effectively, which is benefit to reduce the failure of interconnection.