Abstract
The hollow cathode has yielded high-rate low-pressure operation, with good etch selectivity and etched angle control. This paper shows that high SiO2 etch selectivity is most easily obtained at low pressure in the CF4/H2 process. The etched angle is controlled by metal film deposition which can be independent of the etch selectivity. A combined (metal+polymer) deposition and SiO2 etch process has been tested on commercial complementary metal–oxide semiconductor wafers with excellent yield and reliability results. This multiple deposition and etch process is best done in a new trielectrode hollow cathode chamber which exhibits 1 μm/min SiO2 etch rate with better than ±1% etch uniformity, an etched angle of ∼75°, and SiO2/Si selectivities of 50 (wafer edge) and 150 (wafer center). In addition, polymer deposition on surfaces near the wafer has been eliminated. The voltage and pressure dependence of Si deposition from SiH4 is described, and the hollow cathode ion bombardment is shown to give best planarization at low pressures (2 Pa) and low deposition rates (0.2 μm/min). A planarized SiO2 film is also shown.
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