Demonstration of 20µm pitch micro-vias by excimer laser ablation in ultra-thin dry-film polymer dielectrics for multi-layer RDL on glass interposers

This paper describes the first demonstration of 8-10μm diameter micro-vias at 20μm pitch in ultra-thin dry-film polymer dielectrics to achieve high-density and low-cost redistribution layers (RDL) on panel-based glass and organic interposers. A polymer dielectric dry-film, ZEONIF ZS100, at 10μm thickness was double side laminated on thin and low CTE glass and organic substrates. Micro-via arrays at 20μm pitch were formed by 248nm KrF excimer laser ablation using mask projection scanning, and metallized by a semi-additive process (SAP) using electroless and electrolytic copper plating, with no chemical-mechanical polishing to form fully filled via structures. Fully-filled micro-vias at 20um were achieved using processes scalable to large panels for low-cost and high-density 2.5D and 3D interposers.