An apparatus relates generally to a microelectronic device. In such an apparatus, a first substrate has a first surface with first interconnects located on the first surface, and a second substrate has a second surface spaced apart from the first surface with a gap between the first surface and the second surface. Second interconnects are located on the second surface. Lower surfaces of the first interconnects and upper surfaces of the second interconnects are coupled to one another for electrical conductivity between the first substrate and the second substrate. A conductive collar is around sidewalls of the first and second interconnects, and a dielectric layer is around the conductive collar.