Process for forming a damascene structure

A method of forming a damascene structure, the method comprising:

• depositing a bilayer comprising a first dielectric layer and a second dielectric layer onto a barrier layer of a substrate wherein the first dielectric layer has a dielectric constant higher than the second dielectric layer, and wherein the second dielectric layer is a low k dielectric material comprising Si, C, O and H;
• forming a first layer of photoresist onto the second dielectric layer and patterning a via feature, wherein the via feature exposes a portion of the second dielectric layer;
• exposing the substrate to a first reactive ion etching process, wherein the first reactive ion etch process anisotropically removes the exposed portion of the second dielectric layer to expose a portion of the first dielectric layer;
• exposing the substrate to a second reactive ion etching process, wherein the second reactive ion etch process anisotropically removes the exposed portion of the first dielectric layer to expose a portion of the baffler layer;
• stripping the first photoresist layer, polymers and post etch residues from the substrate;
• applying a planar coating of an anti-reflective layer to the substrate and forming a second photoresist layer onto the anti-reflective layer, wherein the second photoresist layer is patterned to form a trench feature, wherein the trench feature exposes a portion of the anti-reflective layer;
• exposing the substrate to a third reactive ion etching process, wherein the third reactive ion etching process anisotropically removes the exposed portion of the anti-reflective layer and partially removes a portion of the underlying second dielectric layer;
• stripping the anti-reflective layer, the photoresist, polymers and post etch residues from the substrate;
• and
• exposing the substrate to a fourth reactive ion etching process, wherein the fourth reactive ion etching process anisotropically removes the exposed portion of the baffler layer.