Cu/Polyimide Multilayer Interconnections Fabricated by Nanoimprint at Every Lithography Process

Abstract

In this study, Cu/polyimide multilayer interconnections (dual-damascene) approach based on a UV-assisted thermal nanoimprint technique at every lithography process was demonstrated aiming at developing a low-cost fabrication process for high-density interconnections in polyimide. The dual-damascene process can be simplified by nanoimprint using a multi-tiered mold, and realize fine interconnections using a soluble polyimide block copolymer with a high formability and low shrinkage during a polyimide patterning process. Three-layered Cu/polyimide structures with a minimum wire-width of 5 μm were fabricated in the polyimide by performing subsequent Cu electroplating and chemical mechanical polishing (CMP). The feasibility of the process was thus verified. The electric resistances values of the fabricated three-layered interconnections measured by a four-terminal method showed linear increase as a function of the number of interconnection vias. Heat resistance test at 260 °C which corresponded to reflow soldering process was also evaluated; less than 1.2%-increasing ratio of electric resistance was obtained in the case of 3-cycle heating.