Patent ID: 8866297

Claim:
A structure comprising: a substrate; a first metal line and a second metal line over the substrate, with a space therebetween, wherein the first metal line comprises: a metal-containing feature; and a dielectric barrier layer comprising an edge portion contacting a sidewall of the metal-containing feature, and a top portion contacting a top surface of the metal-containing feature; a first air gap on a sidewall of the first metal line and in the space, wherein an edge of the first metal line is exposed to the first air gap, with the edge of the first metal line being a vertical straight edge, and wherein the first air gap has a tapered profile, with lower widths of an upper portion of the first air gap increasingly greater than upper widths of the upper portion of the first air gap; a second air gap on a sidewall of the second metal line and in the space, wherein an edge of the second metal line is exposed to the second air gap, wherein the dielectric barrier layer further comprises a bottom portion extending underlying the first and the second air gaps; and a dielectric material comprising a lower portion in the space and between the first and the second air gaps, wherein the lower portion of the dielectric material is over and in contact with the bottom portion of the dielectric barrier layer.