Width dependence of the effectiveness of reservoir length in improving electromigration for Cu/Low-k interconnects

Reservoir effect of electromigration (EM) reliability has been investigated in Cu/low-k dual-damascene interconnects with varied reservoir lengths. However, the effectiveness of the reservoir effect in improving EM reliability as a function of line width has not been studied till now. In this work, experimental studies of the reservoir effect for both narrow and wide metal lines are conducted. It is found that the reservoir effect is more effective for a narrow line. The variation of the reservoir effectiveness as a function of the reservoir length is found to be different for different line width, and atomic flux divergence (AFD) distribution in the interconnect is used to explain the experimental results with good agreement.