Microstructure and reliability of copper interconnects

The effects of texture and grain structure on the electromigration lifetime of Cu interconnects are reported. Using different seed layers, [111]- and [200]-textured CVD Cu films with similar grain size distributions are obtained. The electromigration lifetime of [111] CVD Cu is about four times longer than that of [200] CVD Cu. For Damascene CVD Cu interconnects, the electromigration lifetime degrades for linewidths in the deep submicron range because the grains are confined as a result of conformal deposition in narrow trenches. In contrast, electroplated Cu has relatively larger grains in Damascene structure, resulting in longer electromigration lifetime than CVD Cu and no degradation for linewidths in the deep submicron range.