Airgap vias in electrical interconnects

Abstract

Multiple interconnect structures with reduced TDDB susceptibility and reduced stray capacitance are disclosed. The structures have one or more pairs of layers (an upper and a lower layer) that form layered pairs in the structure. In each of the upper and lower layers, dielectric material separates an upper pair of interconnects from a lower pair of interconnects or from other conductive material. Pairs of vias pass through the dielectric and mechanically and electrically connect the respective sides of the upper and lower sides of the interconnect. A gap of air separates all or part of the pair of vias and the electrical paths the vias are within. In alternative embodiments, the airgap may extend to the bottom of the vias, below the tops of the lower pair of interconnects, or deeper into the lower layer. Alternative process methods are disclosed for making the different embodiments of the structures.