Current-Induced Phase Partitioning in Eutectic Indium-Tin Pb-Free Solder Interconnect
Structural changes from high-density electric currents were examined in a eutectic In-Sn/Cu interconnect. Under electrical loading, Sn and In migrated in opposite directions, creating a partition of the Sn- and In-rich phases between the anode and the cathode. At the anode, a net gain of Sn atoms resulted in the formation of massive, columnar hillocks on the surface, but a net loss of In led to dissolution and disappearance of the In-rich intermetallic layer. At the cathode, the exodus of Sn left valleys adjacent to the In-rich regions on the surface, while the amount of the In-rich phase grew, due to the net influx of In at the expense of the In-rich intermetallic layer.
Key wordsIn-Sn solder electromigration current stressing hillocks interface
Support for this study was provided by the Chinese Natural Sciences Foundation, grant # 50228101, and the National Basic Research Program of China, grant # 2004CB619306. The authors also owe special thanks to Dr. Warke, Q.L. Yang and others in the Microelectronics Laboratory at IMR for their assistance.
- 2.J.W. Morris, J.L. Goldstein Freer, and Z. Mei, JOM 45, 25 (1993).Google Scholar
- 6.C.J. Thwaites, Atlas of Microstructures of Industrial Alloys, in The Metals Handbook, ed. R.F. Mehl (The American Society for Metals: Metals Park, 1972), pp. 317–320.Google Scholar
- 14.S.G. Epstein, in Liquid Metals: Chemistry and Physics, Ed. S.Z. Beer, Marcel Dekker, New York, pp. 537–584 (1972).Google Scholar