Patent ID: 7955968

Claim:
A method of fabricating dual damascene interconnections on a substrate structure, comprising: forming a first dielectric layer over a substrate structure, where the first dielectric layer is formed from a first material which has a dielectric constant of 2.5 or less and which has a predetermined chemical composition; treating at least part of the first dielectric layer to modify the predetermined chemical composition, thereby forming a treated first dielectric layer; forming a second dielectric layer directly on the treated first dielectric layer, where the second dielectric layer is formed from the first material; partially etching the second dielectric layer and the treated first dielectric layer to form a via opening; partially etching the second dielectric layer to form a trench opening which is connected to the via opening and extends laterally beyond the via opening; treating at least part of the second dielectric layer so that the second dielectric layer has a dielectric constant that is substantially identical to the dielectric constant of the treated first dielectric layer; and forming an interconnect structure by filling the trench opening and via opening with an interconnection material.