Electromigration induced resistance decrease in Sn conductors

The resistance of thick film (2 mum) Sn conductors deposited onto Ni/Cr underlays was found to decrease several percent during electromigration stressing. The application of dc was necessary to initiate the resistance decrease. Equivalent ac current (rms values equal) did not produce the effect and extensive aging at elevated temperature did not either, indicating that the effect is not purely thermally induced. It is suggested that the reduction in the electromigration induced chemical potential from reductions in resistivity associated with reorientation of the microstructure is responsible for the effect. (C) 2003 American Institute of Physics.