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 obtai ned. The electromigration lifetime of (111) CVD Cu is about four times long er than that of (200) CVD Cu, For Damascene CVD Cu interconnects, the elect romigration lifetime degrades for linewidths in the deep submicron range be cause the grains are confined as a result of conformal deposition in narrow trenches. In contrast, electroplated Cu has relatively larger grains in Da mascene structure, resulting in longer electromigration lifetime than CVD C u and no degradation for linewidths in the deep submicron range.