Electromigration resistance and mechanical strength

A brief review is given of models which propose a correlation between electromigration resistance and the mechanical strength of thin film interconnects. In an attempt to achieve metallurgical strengthening and improved electromigration resistance, aluminum films were implanted with oxygen ions. Preliminary electromigration tests online arrays patterned from these films resulted in lifetimes comparabel to the standard Al films. The lack of improvement is attributed to enhanced hillock/whisker growth during electromigration in the implanted interconnects. This behavior is coincident with a lower compressive strength in similarly treated continuous films at elevated temperatures as measured by the substrate curvalure technique