Abstract: An etching solution for a metal hard mask. The etching solution comprises a mixture of a dilute HF (hydrofluoric acid) and a silicon containing precursor. The etching solution also comprises a surfactant agent, a carboxylic acid, and a copper corrosion inhibitor. The etching solution is selectively toward etching the metal hard mask material (e.g., Titanium) while suppressing Tungsten, Copper, oxide dielectric material, and carbon doped oxide.

Abstract: By providing a silicon containing precursor, such as methyl triethoxysilane, to a phosphoric etch bath, wafers containing nitride may be selectively etched without unduly impacting other silicon containing underlying layers.