Anomalous, behavior of resistance in Al alloy interconnections stacked with Ti layers during electromigration tests

In Al alloy interconnections stacked with Ti layers, anomalous behavior of the line resistance was observed during electromigration tests. The line resistance monotonically decreased until it rapidly increased and the line failed. We found that the thickness of the Al lines, which showed the anomalous resistance change, increased uniformly between the anode end and the cathode one. This could explain the anomalous decrease of the line resistance. It was also found that in the resistance decreased lines extra Al grew on the original Al layer and it had the same crystal orientation as the original Al layer. In the case of Al lines with anti-reflective coating (ARC) of TiN/Ti (the upper/lower layer), extra Al grew not only on the original Al layer but also between ARC-TiN and Al3Ti which was formed by a reaction between the Al and Ti. (C) 1997 American Vacuum Society. [S0734-211X(97)01705-8].