Benzocyclobutene polymer filling of high aspect-ratio annular trenches for fabrication of Through-Silicon-Vias (TSVs)

Through-Silicon-Vias (TSVs) with polymer liners have potential improved electrical and mechanical reliability for three-dimensional (3D) packaging/integration applications. To address the challenge in fabrication of polymer liners in high aspect-ratio TSVs, we have developed a vacuum-assisted spin-coating technology for filling benzocyclobutene (BCB) polymer in high aspect-ratio annular trenches. The newly developed spin-coating technology employs spin-coating twice and vacuum treatment after each coating. The vacuum treatment removes the bubbles at the trench bottom trapped during spin-coating and curing, and facilities the formation of void-free BCB filling. The influences of the BCB viscosities and the spin-coating parameters on the filling ability are evaluated, and upon optimization annular trenches with aspect-ratio as high as 22 have been successfully filled with no void formation, thin overburden, and slight dishing. This method is also applicable to trench filling using polymers with similar properties.