Effects of contact area on mechanical strength, electrical resistance, and electromigration reliability of Cu/Low- k interconnects

The measurement result of mechanical strength from a back end of the line (BEOL) Cu/low- k interconnect is reported and correlates with the electrical resistance and electromigration reliability of the interconnect structure with increased via contact areas. A Cu interconnect structure in ultralarge scale integration circuits forms vias between successive layers by removing material in the top surface of the lower interconnect, extending the via feature down into the lower interconnect and creating cone-shaped apertures. The increased via contact area increases the overall mechanical toughness of the BEOL interconnect, reduces the electrical contact resistance, and enhances the electromigration resistance of the integrated circuit. © 2010 The Electrochemical Society.