Influence of local thermal dissipation on electromigration in an Al thin-film line

Abstract

To improve the reliability of Al thin-film lines in integrated circuits, the influence of local thermal dissipation on electromigration (EM) was investigated. By performing current stressing experiments on Al thin-film lines with a special design, the unique distribution of hillocks/voids around four representative zones was found. The underlying mechanism was explained by investigating the corresponding atomic flux divergence according to finite element analyses. Such unique distribution of hillocks/voids, differing from the general EM phenomenon with hillocks at anode and voids at cathode, indicates the influence of local thermal dissipation induced by the voltage-measuring pads. Moreover, by changing the position of the voltage-measuring pads in the Al thin-film line, it was found that when the position of local thermal dissipation is farther from the center of the line, the EM resistance is higher. This finding provides a valuable insight for improving the EM resistance of Al thin-film lines and therefore enhancing the reliability of the corresponding devices.