Subtractive Ru Interconnect Enabled by Novel Patterning Solution for EUV Double Patterning and TopVia with Embedded Airgap Integration for Post Cu Interconnect Scaling

Fully subtractive TopVia Ru interconnects with embedded airgap have been demonstrated through spacer assisted litho-etch litho-etch (SALELE) patterning, which utilizes a novel spacer pull process to enable a wider design space than alternative spacer-is-metal (SADP-SIM) patterning approaches. Utilizing this approach, we have demonstrated good pattern fidelity and electrical yield for structures with minimum pitch at 18nm. Furthermore, we propose a novel 'TopVia' structure, where the metallization for the via is performed together with the metallization for the line below, combined with an integrated airgap. The TopVia integration scheme enables a barrier-less/liner-less via structure leading to maximum conductor volume, with greatly reduced liner thickness at the via contact. Simulation results support significant reductions in both via resistance and capacitance can be achieved by replacing conventional Cu interconnects with Ru TopVia interconnects with airgaps. We believe the combination of a SALELE with spacer pull process and top-via with embedded airgap integration is one of the most promising integration schemes to enable a Ru conductor in future technology nodes.