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Abstract
Nitrogen trifluoride (NF3) is a stable and non-flammable gas that is commonly used in a chamber cleaning process in the manufacture of semiconductors. Research at Infineon Technologies AG's 300 mm wafer manufacturing facility was conducted to optimize the NF3-based process used to clean Novellus Altus Concept 3 CVD chambers following tungsten deposition. Their goal was to reduce gas costs and/or shorten the time required to clean the CVD chamber. Their strategy was to construct response surfaces for perfluorocompound emissions and clean times as a function of NF3 gas flow, Ar/NF3 ratio, pressure and temperature. The purpose of the chamber clean is to volatilize the tungsten residue as WF6. Byproducts of the NF3 clean are non-utilized NF3, WF6, F2 and HF. Observing NF3 in the effluent indicates the start of the chamber clean. While clean times are the same or faster as the baseline process, the optimized processes must also effectively clean the CVD chamber.