Investigation of CF 3 I as an Environmentally Benign Dielectric Etchant

In this study, trifluoroiodomethane (CF 3 I), 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 CF 3 I and C 2 F 6 /O 2 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 CF 3 I: O2 ratio. Destruction efficiencies of CF 3 I at different processing parameters were evaluated. Depending on the flow rate, rf power, and chamber pressure, utilization efficiency of CF 3 I varied from as low as 10% to as high as 68%. CF 4 , C 2 F 6 , COF 2 , and CO 2 were the predominant by-products found in the exhaust stream; however, their concentrations were very low compared to the traditional process employing C 2 F 6 /O 2 mixtures.