C_2F_6/O_2 and C_3F_8/O_2 Plasmas SiO_2 Etch Rates, Impedance Analysis, and Discharge Emissions

摘要

We have investigated to feed gas compositions that result in the fastest etch rates of SiO_2 in C_2F_6/O_2 and C_3F_8/O_2 based plasmas and have independently measured the radio-frequency electrical characteristics and optical emission spectra of the plasmas. Gas phase Fourier transform infrared spectroscopy was used to quantify the perfluorocompound (PFC) emissions. Under optimal operating conditions the C_2F_6/O_2 based discharges exhibited significantly faster etch rates than the C_3F_8/O_2 based discharges. At the gas compositions that resulted in the fastest etch rates (55 mol % O_2/C_2F_6 and 68 mol % O_2/C_3F_8) the greatest F atom densities, the most inductive phase angles, and the highest discharge impedance magnitudes were observed. Higher oxygen feed gas concentrations resulted in higher PFC utilization efficiencies and smaller quantities of plasma generated CF_4. For identical feed gas compositions C_2F_6/O_2 based discharges produced on average 50% less plasma generated CF_4 than C_3F_8/O_2 based discharges.