Abstract: A method is provided for etching and removing extraneous molybdenum or debris on ceramic substrates such as semiconductor devices and also for molybdenum etching in the fabrication of molybdenum photomasks. The method employs a multi-step process using an acidic aqueous solution of a ferric salt to remove (etch) the molybdenum debris followed by contacting the treated substrate with an organic quaternary ammonium hydroxide to remove any molybdenum black oxides which may have formed on the exposed surface of treated molybdenum features in ceramic substrates. The method is environmentally safe and the waste solutions may be easily waste treated for example by precipitating the ferric salts as ferric hydroxide and removing anions such as sulfate by precipitation with lime. The method replaces the currently used method of employing ferricyanide salts which create serious hazardous waste disposal and environmental problems.

Abstract: A molybdenum etching process which reduces hazardous treatment waste is disclosed. Etchants which can be used are ferric sulfate and ferric ammonium sulfate. Waste products resulting from this etch are Fe(OH).sub.3 and CaSO.sub.4.