Reliability of through-silicon-vias (TSVs) with benzocyclobutene liners

Abstract

Through-silicon-vias (TSVs) using benzocyclobutene (BCB) as insulation layers (liners) are developed and the reliability related issues with regard to mechanical and electrical aspects are investigated. The BCB TSVs are fabricated using deep etching of annular trenches on a substrate, BCB cladding forming in the deep trenches, selective etching of the silicon posts in BCB claddings, and electroplating of copper plugs. The insulation capability and the configuration stability of BCB liners are evaluated by performing a thermal shock test and comparing the leakage currents before and after thermal shock. The results show that the BCB insulation capability does not change distinctly after thermal shock. Auger electronic spectroscopy (AES) is used to characterize copper diffusion through BCB thin films after high temperature treatment, and it is found that BCB is able to prevent copper diffusion at temperatures as high as 350°C. Finite element analysis is performed to understand the thermal stress behaviors of BCB TSVs, and the simulation results show that BCB liners are able to reduce the thermal induced stresses in substrates, but increase the axial thermal expansion of copper plugs.