The Effect of Polyimide Passivation on the Electromigration in Sputtered Copper Films

Electromigration damage (EMD) is one of the major causes for the failures of interconnect. In this study, the electromigration of Cu with polyimide passivation is investigated with an isothermal resistance change method. Resistance decreases in passivated samples caused by diffusion of polyimide ingredients into copper are observed. Polyimide passivation enhances the lifetime of the Cu metallization (sputtered copper films). The lifetime of passivated copper films are from 1.1 to 29 times those of the unpassivated ones, depending on the passivation materials and the current stressing conditions. Rigidity of the passivation is found to be the controlling factor for lifetime improvement. In addition, the adhesion strength between the Cu and the polyimide is studied in this work. An interlayer TiWN promotes the adhesion between the Cu and the polyimide interface. Key words: