Facing the challenges in the reliability study of interconnection system as mentioned above, the most vital solution is to employ physics-based simulation and modeling. As most physical systems can be described using a set of partial differential equations, finite element method (FEM) has evolved to be a good tool in solving these partial differential equations and obtain solutions that represent the physical process of degradation of interconnection system in ULSI. As our understanding of the failure mechanisms of interconnection system increase with the help of FEM and experimentation, and the increasing power of numerical computation hardware and software, models formulated using FEM can be complex and their results are becoming closer to the reality. Hence, key influencing factors on ULSI interconnection reliability can be identified using FEM, and one can then design the interconnect system appropriately for the desired reliability.