Fine pitch copper wire bond process development for dual damascene Cu metallized chips

With the improvements in integrated circuit (IC) features, it becomes necessary to make a transition to a low resistive interconnect material. Copper (Cu) is preferred as an alternate interconnect material for high performance devices. The objective of the current research work is to develop a reliable fine pitch Cu wire bonding on a Cu metallized chip. Capillary design, Free Air Ball (FAB) study and process optimization are important for realizing a reliable Cu/Cu wirebond. Dual damascene Cu metallized test chip has been designed and fabricated. A cleaning process is developed and wire bonding process optimization has been carried out. Surface analysis by Auger electron spectroscopy (AES) and ball shear tests indicate unambiguously that the cleaning process has significant influence on the removal of Cu oxide and other contamination. With the new cleaning process and wire bond optimisation, a reliable Cu/Cu wire bond process is developed. The details of cleaning process and wire bond techniques are discussed in this paper.