Radio frequency reactive sputter etching—control of etch rates

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Etch rate variability in a reactive sputter-etching process can come from many factors, and here the etching of SiO2 in CHF3 is used in a study of the effects of various parameters on the etch rate, although other materials are also considered. It is found that this SiO2/CHF3 combination is remarkably insensitive to chamber pump-out time and the initial chamber condition, at least at high applied rf voltages (1.5 kV peak to peak). However, the gas pressure, flow rate, applied rf voltage, and the target electrode configuration do have a strong effect on rates. This latter result is shown to agree with presently available data on the capacitance of sputtering glow discharges. An etch rate reproducibility of ±2% over a period of four months has been demonstrated.