C2F6/O-2 and C3F8/O-2 plasmas SiO2 etch rates, impedance analysis, and discharge emissions

We have investigated the feed gas compositions that result in the fastest e tch rates of SiO2 in C2F6/O-2 and C3F8/O-2 based plasmas and have independe ntly measured the radio-frequency electrical characteristics and optical em ission spectra of the plasmas. Gas phase Fourier transform infrared spectro scopy was used to quantify the perfluorocompound (PFC) emissions. Under opt imal operating conditions the C2F6/O-2 based discharges exhibited significa ntly faster etch rates than the C3F8/O-2 based discharges. At the gas compo sitions that resulted in the fastest etch rates (55 mol % O-2/C2F6 and 68 m ol % O-2/C3F8) the greatest F atom densities, the most inductive phase angl es, and the highest discharge impedance magnitudes were observed. Higher ox ygen feed gas concentrations resulted in higher PFC utilization efficiencie s and smaller quantities of plasma generated CF4. For identical f'eed gas c ompositions C2F6/O-2 based discharges produced on average 50% less plasma g enerated CF4 than C3F8/O-2 based discharges. (C) Air Products and Chemicals , Inc. - 1999. S1099-0062(99)09-072-0.