Electromigration of Flat and Bent Copper Lines Patterned with a Plasma-Based Etch Process

Abstract

The electromigration performance of the copper line, which was patterned by a unique plasma-based etch process, was investigated with the accelerated isothermal lifetime method. The failure analysis result showed that voids originated along the copper–dielectric interface as well as at copper grain-boundary junction points. During the electromigration test, a large stress existed between the copper layer and the silicon nitride cap layer, which caused the cap layer cracking and copper extrusion. When the copper line was mechanically bent, the activation energy was lowered and the void distribution pattern was drastically changed. The lifetime of the copper line was shortened with the applied bending stress. Therefore, for large-area flexible electronics applications, the reliability of the copper interconnect line is an important factor that needs to be addressed.