Dynamic Analysis on Underlay Microstructure for Cu/Low-k Wafer during Wire Bonding

Two major analyses were conducted in this paper. In the first, experimental procedures are accomplished to measure the tensile mechanical properties of ultra thin gold wire (=1mil) before/after electric flame-off (EFO). Characteristics of free air ball (FAB), heat affected zone (HAZ) and as-drawn wire have been carefully investigated by nanoindentation, microhardness and self-design pull test fixture. Secondary, with the obtained experimental material data, a comprehensive finite element model using software ANSYS/LS-DYNA is successfully developed to simulate the wirebonding. Dynamic analysis is performed to evaluate the overall stress distributions on the underlay microstructure of Cu/low-k wafer. Special emphasizes are focused on the Copper via and the intermetal dielectric (IMD)/undoped silica glass (USG) dielectric microstructure.