Wet-etch solutions for conductive metals (e.g., copper) and metal nitrides (e.g., tantalum nitride) can be tuned to differentially etch the conductive metals and metal nitrides while having very little effect on nearby oxides (e.g., silicon dioxide hard mask materials), and etching refractory metals (e.g. tantalum) at an intermediate rate. The solutions are aqueous base solutions (e.g., ammonia-peroxide mixture or TMAH-peroxide mixture) with just enough hydrofluoric acid (HF) added to make the solution's pH about 8-10. Applications include metallization of sub-micron logic structures.