A method and system for cleaning and/or stripping photoresist from photomasks used in integrated circuit manufacturing comprising a process and means of introducing a mixture of sulfuric acid and ozone (or a mixture of sulfuric acid and hydrogen peroxide) to the surface of a photomask while applying megasonic energy. The invention also comprises method and system comprising a process and means of introducing ozonated deionized water and/or a low temperature dilute aqueous solution (dAPM) to the surface of photomasks while applying megasonic energy. The process and apparatus also remove post plasma ashed residues and other contaminants from photomask surfaces.