US Patent 11195750 Etch profile control of interconnect structures

A method of forming a semiconductor structure includes forming an etch stop layer on a substrate, forming a metal oxide layer over the etch stop layer, and forming an interlayer dielectric (ILD) layer on the metal oxide layer. The method further includes forming a trench etch opening over the ILD layer, forming a capping layer over the trench etch opening, and forming a via etch opening over the capping layer.