| dc.description.abstract | As the speed and function of the CPU continuous to increase, I/O count (Input-Output) also increases dramatically. According to the semiconductor roadmap, by 2007 the current density for each C4 solder bump will exceed 104 A/cm2. Two EM failure modes have been reported. The first one is voiding, which occurs at the solder/compound interface. The second EM failure mode is the EM-induced dissolution of the Cu metal bond pad or the Cu trace lines. The current density and the stressing temperature are the critical parameters for various EM failure modes. We found that the critical EM parameters, the current density and the stressing temperature, significantly influence various EM failure modes, for example, Cu consumption, voids formation and asymmetric interfacial compound formation in our experimental results. From the experimental results in this study, we build up a detail mechanism of EM effect on flip-chip Cu/Sn solder joint by analyzing the Cu atomic flux step by step. EM-induced Cu consumption, voids formation, and asymmetric interfacial compound formation can be well-defined and explained by this mechanism. Finally, we can define Z* of Cu in the Sn matrix is around 130 and establish a map for EM failure mode. The failure map is of important to those who design the flip-chip joint structure with an excellent reliability.
In chapter 2, we investigate the Cu/Sn interface of flip-chip solder joints under current stressing. From the experimental results with different current densities at different temperatures, we find out the critical factors influence on flip-chip Cu/Sn solder joints and obtain important parameters for calculating EM flux. In chapter 3, we successfully fabricate crystalline Cu3Sn and Cu6Sn5 bulk compounds by liquid-electromigration method. Also, we observe EM effect on the Cu6Sn5 compound. Then, we discuss the detail mechanism of EM effect on Sn/Cu flip-chip solder joint and show how the atomic flux be calculted in every step in chapter 4. Moreover, voids formation, EM-induced Cu consumption, and asymmetric IMC formation can be well-defined by the equating atomic fluxes. Finally, we can define Z* of Cu and establish a failure map for EM failure mode in chapter 5. | en_US |