US Patent 8003516 BEOL interconnect structures and related fabrication methods

Methods for forming voids in BEOL interconnect structures and BEOL interconnect structures. The methods include forming a temporary feature on a top surface of a first dielectric layer and depositing a second dielectric layer on the top surface of the first dielectric layer. The temporary feature is removed from the second dielectric layer to define a void in the second dielectric layer that is laterally adjacent to a conductive feature in the second dielectric layer. The void operates to reduce the effective dielectric constant of the second dielectric layer, which reduces parasitic capacitance between the conductive feature and other conductors in the BEOL interconnect structure.