High aspect ratio metal-polymer composite structures for nano interconnects

This paper presents a novel low-temperature process that combines high-aspect-ratio polymer structures with electroless copper plating to create laterally compliant MEMS structures. These structures are evaluated as IC-package interconnects that can lead to reliable, low-cost and high-performance nano wafer-level packaging. High-aspect-ratio low CTE polyimide structures with low stress, high toughness and strength were fabricated using plasma etching, This dry etching process was tuned to yield a wall angle above 80 degrees leading to an aspect ratio higher than 4. The etching process also leads to roughened sidewalls for selective electroless plating on the sidewalls of the polymer structures. Simulations of these fabricated structures show tremendous reduction in the stresses at the interfaces and superior reliability as IC-package nano interconnects. Metal-coated polymer structures from MEMS fabrication techniques can provide low-cost high-performance solutions for wafer-level-packaging.