Electromigration and integration aspects for the copper-SiLK system

Abstract

In this study, the thermal characteristics and electromigration (EM) resistance of two dielectrics, SiLK(TM) and SiO2, are investigated to evaluate the feasibility of low dielectric-constant SiLK for intermetal. dielectric applications. Liftoff patterning was employed to fabricate the Cu interconnect for the EM test, and the Taguchi method was used in the experimental design to identify the key parameters for a successful liftoff. It was shown that the thermal impedance of the metal lines passivated with SiLK is 14% higher than that of metal lines passivated with SiO2. On the basis of the thermal impedance and temperature rise of the interconnect, it was concluded that the major heat transfer path is via the underlayer dielectric to the Si substrate. The activation energy of EM for Cu passivated with SiLK is smaller, and the EM lifetime is shorter than that of Cu passivated with SiO2. Possible mechanisms are discussed.