New approaches for the assessment of stress-induced voiding in Cu interconnects

Stress-induced voiding (SIV) in copper interconnects was studied during high temperature storage (HTS). Stressvoids were observed in the Cu-line under dual-damascene (DD) vias and W-plugs, respectively. In both cases medium failure times are decreasing exponentially with increasing stress temperature. On structures with W-plugs two voiding modes with different activation energies were observed, on Cu-lines with DD-vias a monomodal behavior only. Design features such as line width, length or via-to-line overlap have a strong influence on SIV. Based on the presented data a method is proposed that allows the approximation of SIV-limited lifetime under operation conditions.