No abstract

The reliability of copper bonding wire in plastic mold package has been associated with the intermetallic compound formation and growth in the presence of halogen element such as chloride in epoxy molding compound.

The addition of calcium (Ca) simultaneously improves the ductility and strength of UFG Au wires. Based on the observation on stacking faults, microstructures, simulation results and significant effect of Ca on grain boundary related properties, it is inferred that segregation of Ca to stacking faults and grain boundaries has occurred to induce effective stacking fault energy (SFE) reduction and properties improvement. Considering the known greater impact of SFE in UFG/ NC metals, segregating dopants are proposed to be an effective strategy for achieving dual improvement in this class of materials. Also, dopant selection criteria for this purpose is also suggested and verified.

Wire bonding remains the dominant form of interconnection technology, and is expected to be used in 85% of total IC units worldwide by 2010. As device miniaturization continues, the diameters of wires get finer, requiring higher mechanical strength from the thin wires for handling. However, strong wires with low ductility pose an insurmountable hurdle in manufacturing because of formability issues. Therefore, strategies to attain both high strength and ductility (dual improvement) in Au wires need to be developed, a goal shared by researchers in the field of nanocrystalline (NC) and ultrafine-grained (UFG) materials. The objective of this study is to establish dopant selection criteria (in low ppm level) in Au wires to achieve the goal of dual improvement. In this thesis, the unique effect of Ca on simultaneously improving the strength (by-60%) and ductility (by-96%) of Au wires is demonstrated. Also, Ca is shown to retard high temperature creep by 4-6 times, where the activation energy, stress and grain size exponent all indicate that grain boundary (GB) diffusion mediated GB sliding creep has occurred. Also, the Hall-Petch coefficient is increased-these obvious impacts on GB-related properties have suggested the segregation tendency of Ca in Au wires. The postulation that stacking fault energy (SFE) reduction is the underlying mechanism is confirmed by statistical measurement on stacking fault (SF) width/ density, where SFE is found to be reduced from 15-50 mJ/m to 10-34 mJ/m. The observations viii