Investigation of CF₃I as an environmentally benign dielectric etchant

In this study, trifluoroiodomethane (CF₃I), a non-global-warming gas, has been investigated as a substitute for typical PFC's currently used in wafer patterning and CVD chamber cleaning processes. Dielectric films consisting of plasma enhanced chemically vapor deposited silicon dioxide and silicon nitride were comparatively etched in CF₃I and C₂F₆/O₂ plasma environments. The etch rate of these films was ascertained as a function of applied rf power, etchant gas flow rate, reaction chamber pressure, and CF₃I: O₂ ratio. Destruction efficiencies of CF₃I at different processing parameters were evaluated. Depending on the flow rate, rf power, and chamber pressure, utilization efficiency of CF₃I varied from as low as 10% to as high as 68%. CF₄, C₂F₆, COF₂, and CO₂ were the predominant by-products found in the exhaust stream; however, their concentrations were very low compared to the traditional process employing C₂F₆/O₂ mixtures.