Provided are methods for processing semiconductor substrates to remove high-dose ion implanted (HDI) photoresist structures without damaging other structures made of titanium nitride, tantalum nitride, hafnium oxide, and/or hafnium silicon oxide. The removal is performed using a mixture of an organic solvent, an oxidant, a metal-based catalyst, and one of a base or an acid. Some examples of suitable organic solvents include dimethyl sulfoxide, n-ethyl pyrrolidone, monomethyl ether, and ethyl lactate. Transition metals in their zero-oxidation state, such as metallic iron or metallic chromium, may be used as catalysts in this mixture. In some embodiments, a mixture includes ethyl lactate, of tetra-methyl ammonium hydroxide, and less than 1% by weight of the metal-based catalyst. The etching rate of the HDI photoresist may be at least about 100 Angstroms per minute, while other structures may remain substantially intact.