Abstract
A new rf sputter etching configuration is described which enables SiO2 rates as high as 12 nm s−1 (0.72 μm min−1) to be obtained at CF4 pressures as low as 0.1 Pa (0.75 mTorr) with 3.8–6.4 Wcm−2 and 1.5 kVp-p applied to the etched sample. Comparing these etch rates with standard reactive sputter etching at 1.5-kV peak-to-peak applied rf voltage, the present etch rates are a factor of 100 higher at 0.1 Pa (0.75 mTorr) and a factor of 10 higher at 10 Pa (75 mTorr). The new configuration consists of two closely spaced opposing electrodes, connected electrically together as an etching target. These electrodes correspond to the ‘‘hollow cathode’’ used in dc discharges, and an intense discharge forms in between them. Here the etching properties of this configuration are demonstrated using CF4 over a 0.1–10-Pa pressure range and with the applied rf voltage varied from 0.5 to 1.5 kV peak-to-peak.
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