A novel in-situ resistance measurement to extract IMC resistivity and kinetic parameter for CoSn 3D stacks

Abstract

Cobalt based UBM (under bump metallization) has the advantages of less UBM consumption, single and ductile IMC (intermetallic compound)) and no Kirkendall voids formation which makes it interesting for 3D stacking specially in fine pitch microbumps. In this paper for first time the electrical properties of Co-Sn IMC and kinetics of IMC growth are investigated by in-situ resistance measurement. Extracted parameters are verified by conventional cross section SEM analysis. This technique has the advantages of being non-destructive, quick and accurate measurement for any UBM and solder materials for 3D applications.