This invention relates to a selective etching and formation of xenon difluoride, and in particular relates to a process for selective removal of materials, such as: silicon, molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, tantalum, niobium, boron, phosphorus, germanium, arsenic, and mixtures thereof, from silicon dioxide, silicon nitride, nickel, aluminum, TiNi alloy, photoresist, phosphosilicate glass, boron phosphosilicate glass, polyimides, gold, copper, platinum, chromium, aluminum oxide, silicon carbide and mixtures thereof. The process is related to the important applications in the cleaning or etching process for semiconductor deposition chambers and semiconductor tools, devices in a micro electro mechanical system (MEMS), and ion implantation systems. Methods of forming XeF2 by reacting Xe with a fluorine containing chemical are also provided, where the fluorine containing chemical is selected from the group consisting of F2, NF3, C2F6, CF4, C3F8, SF6, a plasma containing F atoms generated from an upstream plasma generator and mixtures thereof.