Impact of line spacing on microstructure and texture in damascene Cu interconnects

Microstructure and texture variation have been investigated as a function of line spacing in damascene Cu interconnects lines. Four set of specimens, with the same line width but different line spacing were examined using electron backscattered diffraction (EBSD). The results show that the average grain size gradually increases with the increasing line spacing. Boundaries with a misorientation of 55°~60° and Σ3 ones were found in higher proportion, followed by boundaries with a misorientation of 35°~40° and Σ9 boundaries. When the line spacing is lower than 2.5 μm, as the line spacing increases, the proportion of Σ3 boundaries gradually decrease, and there is little change of Σ9 boundaries. As the line spacing is higher than 2.5 μm, the proportion of Σ3 and Σ9 boundaries both increase. There is an influence of line spacing on {111} and {001} texture intensity. For a certain line width, there is a critical spacing. Below the threshold limit, {111} texture component weakened and {001} texture component enhanced with the increasing line spacing; Otherwise, {111} texture intensity increased and {001} texture intensity decreased.