Patent ID: 6984577

Claim:
A method for fabricating a damascene interconnect structure having one or more air trenches and a plurality of spaced-apart metal lines comprising: (a) fabricating the damascene structure to a via level through a processing step prior to forming contact vias, wherein step (a) comprises: depositing a first dielectric layer; depositing a first capping layer over the first dielectric layer; forming a plurality of trenches in the first capping layer and the first dielectric layer; filling the plurality of trenches with metal to form the plurality of spaced-apart-metal lines, wherein the plurality of spaced-apart metal lines are situated in the first capping layer and the first dielectric layer; depositing a second capping layer directly on the first capping layer; and depositing a second dielectric layer over the second capping layer; (b) etching one or more air trenches into the damascene structure so that the air trenches are positioned over selected metal lines, wherein the one or more air trenches are not etched into the first dielectric layer and the first capping layer, wherein the second capping layer is situated over the selected metal lines; and (c) depositing a sealing layer over the damascene structure having air trenches to seal the air trenches.