Fluorocarbon high‐density plasmas. II. Silicon dioxide and silicon etching using CF4 and CHF3

We report a study of the application of CF4 and CHF3 electron cyclotron resonance (ECR) discharges to selective etching of SiO2 over Si. Due to significant fluorocarbon film deposition for plasma operation without rf sample bias in the pressure range below 10 mTorr, rf biasing is required for etching of SiO2 and Si. The rf threshold voltage for etching is 55 V for CHF3 and 35 V for CF4 at a pressure of 1 mTorr. At 100 V rf bias, silicon dioxide etch rates were greater than ≂600 nm/min in CF4 and 450 nm/min for 1000 W plasmas at 1 mTorr pressure. A plot of the oxide etch rate vs rf bias exhibits a fluorocarbon film suppression regime at low rf voltages and an oxide sputtering regime at higher rf voltages. In the fluorocarbon suppression regime, the etch rate is primarily determined by fluorocarbon deposition which results in a thin fluorocarbon film being present on the SiO2 surface during steady‐state etching. In the oxide sputtering regime, the oxide etch rate increases linearly with the ion current to t...