Suspended Photoresist Thin Film for Fabrication of Through Silicon Vias

This paper outlines a novel technique for using suspended photoresist thin-film coating in the fabrication of through silicon vias (TSVs). Photoresist thin film formed through self-assembly on a water surface is transferred to a wafer surface and patterned to be suspended on previously fabricated through-vias as sacrificial layer. After a seed layer is deposited and the photoresist film is chemically removed, the through-vias are filled by backside electroplating. In our experiment, 300-500-nm-thick AZ5214 photoresist thin films were successfully suspended on through-vias up to 60 μm in diameter, providing planer cover plates for 300-nm-thick Cu seed layer deposition. This technique may serve as a promising route for front-side chemical-mechanical polishing-free and postdevice processes in the fabrication of TSVs.