Capping layer to reduce amine poisoning of photoresist layers

An apparatus for reducing amine poisoning of photoresist layers comprises a substrate, an etch stop layer containing amines formed over the substrate, and a dense capping layer formed directly on the etch stop layer, wherein the dense capping layer substantially prevents the amines from diffusing out of the etch stop layer and into a subsequently formed photoresist layer. The dense capping layer may comprise silicon carbide, silicon carboxide, or a combination of silicon carbide and silicon carboxide. The dense capping layer may have a density greater than or equal to 2 g/cm3 and a thickness that ranges from 10 Å to 200 Å.