Electrical/Mechanical Modeling, Reliability Assessment, and Fabrication of FlexConnects: A MEMS-Based Compliant Chip-to-Substrate Interconnect

Compliant free-standing structures can be used as chip-to-substrate interconnects. Such ldquocompliant interconnectsrdquo are a potential solution to the requirements that will be imposed on chip-to-substrate interconnects over the next decade. However, cost of implementation and electrical performance limit compliant interconnects. In our previous work, we have proposed a new compliant interconnect technology calledFlexConnectto address these concerns with compliant interconnects. An innovative cost-effective MEMS-based fabrication process is used to fabricate these compliant interconnects. Sequential lithography and electroplating processes with up to two masking steps are utilized. Utilizing the proposed fabrication process, in this paper,FlexConnectsare realized at a 100-mum pitch. High-frequency modeling of the electrical parasitics of the interconnect is performed. Through finite-element-based models, the advantage of using multiple electrical paths as part of the interconnect design is shown from a thermomechanical reliability perspective. Finally, taking advantage of the MEMS-based photolithographic fabrication process, a heterogeneous combination ofFlexConnectsand column interconnects is proposed. This approach is shown to be an additional avenue to attain improved electrical performance without compromising mechanical performance.