Design and Fabrication of FlexConnects: A Cost-Effective Implementation of Compliant Chip-to-Substrate Interconnects

Abstract

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. This paper presents two concepts to address this. First, an innovative, cost-effective fabrication process to realize compliant interconnects is proposed. Sequential lithography and electroplating processes with up to two masking steps are utilized. Such an approach potentially reduces the cost of fabricating compliant interconnects. Second, an innovative approach to designing compliant interconnects is proposed to improve electrical performance without compromising on mechanical reliability. The new approach uses parallel/multiple electrical paths as part of the compliant interconnect design. These concepts are integrated to realize a new compliant interconnect technology called FlexConnects. Utilizing the proposed fabrication process parallel-path FlexConnects are realized at a 100-mum pitch. Numerical simulations are used to demonstrate that the electrical performance of parallel-path FlexConnects (self inductance of ~ 37 pH) is enhanced without compromising on mechanical performance, validating the use of parallel/multiple electrical paths in the interconnect design.