Feasibilities on diffusion between copper and tin utilizing variable frequency microwave (VFM) cure on micro-bump interconnections

Abstract

Micro Cu bump with tin-cap is one of the candidate interconnections for 3D stacked LSI. First, it was found the diffusion between copper and tin at the curing in variable frequency microwave (VFM) oven was faster than at the heating on a hot-plate. Moreover, IMC between tin and copper after the low-temperature bonding as Cu6Sn5 transit to approximately uniform Cu3Sn by curing in VFM oven. Then, the possibilities on the micro-joint with the VFM cure were found out. This work was performed under the management of ASET supported by NEDO.