Reliability and copper interconnections with low dielectric constant materials

Abstract

The materials, process integration, and reliability issues in the development of multilevel electroplated Cu/polyimide on-chip interconnections are described. A combination of: good diffusion/adhesion barrier layers consisting of a metal liner plus the insulator Si3N4, and W stud/Si contacts resulted in a highly reliable IC chip. Electromigration of Cu damascene lines in both SiO2 and polyimide structures was investigated. Similar void growth was observed at the cathode ends of both the interconnect systems. However, the shapes of protrusions at the anode ends of the lines were different. Although the activation energies for both near bamboo-like Cu/SiO2 and Cu/polyimide were both 1.1 eV, the electromigration lifetime of the former was significantly longer. The difference is largely attributable to the poorer thermal conductivity of polyimide.