Thin polymer dry-film dielectric material and a process for 10 um interlayer vias in high density organic and glass interposers

This paper describes the first demonstration of 10 μm diameter interlayer vias in low-moisture uptake and low surface-roughness dry film polymer dielectric for multi-layered re-distribution layer (RDL) structures to achieve 50 μm bump pitch in high density organic and glass interposers. A new series of polymer dry films, ZS-100, at 10 μm thickness were deposited on thin and low CTE organic or glass cores using double-sided vacuum lamination processes. The ultra-small vias were fabricated by 248nm KrF excimer laser drilling, followed by electroless and electrolytic copper plating. Fully-filled via structures were successfully fabricated without any chemical-mechanical polishing. The processes demonstrated in this paper achieve much finer bump pitch than current organic packages, and can be scaled to large panels leading to lower cost than previous work in fine pitch Si interposers using back-end of line (BEOL) wafer processes.