Alternative Chemistries for Chamber Cleans to Reduce Perfluorocompound (PFC) Emissions

Due to their long atmospheric lifetimes and strong infrared absorption, perfluorocompounds (PFCs) have the potential to profoundly affect the radiative heating capacity of the earth. The semiconductor industry depends heavily on PFCs for chamber cleaning and film etching. Two alternative chemistries for chamber cleaning are reviewed in this paper; nitrogen trifluoride (NF3) and chlorine trifluoride (CIF3). Nitrogen trifluoride shows promise as an alternative to C2F6 in silicon oxide chamber cleans, because it offers higher utilization rates and decreased gas mass requirements. NF3 also has a lower global warming potential than C2F6, resulting in a substantially lower global warming impact for the process. The price of NF3 is currently high, resulting in increased operating costs for the process. Chlorine trifluoride, which has no global warming potential, may be an alternative chemistry for cleaning tungsten and silicon nitride chambers. CIF3 also shows some promise as an alternative chemistry for etch processes, because it can provide anisotropic etching of silicon surfaces. While CIF3 shows promise as an alternate chemistry, detailed process descriptions for CIF3 are not readily available to make estimates of gas usage, gas emissions, or cost.