Demonstration of 10-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m Microvias in Thin Dry-Film Polymer Dielectrics for High-Density Interposers

Abstract

This paper describes the demonstration of 10-µm diameter interlayer vias with 3.5-µm wide re-distribution layer copper wiring in a unique dry-film polymer dielectric, ZEONIF ZS100 (ZS100), suitable for panel-based high-density organic and glass interposers. The uniqueness of polymer dielectric includes low dielectric constant, low dielectric loss, low moisture uptake, and low surface roughness. The dry-film polymer dielectric was laminated on thin and low coefficient of thermal expansion organic or glass cores using double-side vacuum lamination processes. The ultrasmall microvias were drilled with 248-nm KrF excimer laser. Metallization by electroless and electrolytic copper plating successfully achieved formation of fully filled vias and copper traces simultaneously without any chemicalmechanical polishing. The processes demonstrated in this paper enable interposers with much finer bump pitch than current organic package technology. In addition, the processes can be scaled to large panels leading to lower cost than the previous work in fine pitch Si interposers fabricated through back-endof-line wafer processes.Index Terms-Excimer laser, fine pitch via, fine pitch wiring, microvia, thin dielectric film.

A novel production process for 10 μm microvias.

“…In general, there exist only couple of works which have reported the formation of ultra small microvia. In [3] and [4], the authors have affirmed the success of 10 µm microvias in 10 µm thick dry film dielectric with 248 nm KrF excimer laser on ZS100 polymer. On the other hand, this process is still semi-additive process (SAP) where Cu seed layer is initiated and etched afterward.…”