Effects of N2 addition on chemical dry etching of silicon oxide layers in F2∕N2∕Ar remote plasmas

Abstract

In this study, chemical dry etching characteristics of silicon oxide layers were investigated in the F2∕N2∕Ar remote plasmas. A toroidal-type remote plasma source was used for the generation of remote plasmas. The effects of additive N2 gas on the etch rates of various silicon oxide layers deposited using different deposition techniques and precursors were investigated by varying the various process parameters, such as the F2 flow rate, the additive N2 flow rate, and the substrate temperature. The etch rates of the various silicon oxide layers at room temperature were initially increased and then decreased with the N2 flow increased, which indicates an existence of the maximum etch rates. Increase in the oxide etch rates under the decreased optical emission intensity of the F radicals with the N2 flow increased implies that the chemical etching reaction is in the chemical reaction-limited regime, where the etch rate is governed by the surface chemical reaction rather than the F radical density. The etch rates of the silicon oxide layers were also significantly increased with the substrate temperature increased. In the present experiments, the F2 gas flow, the additive N2 flow rate, and the substrate temperature were found to be the critical parameters in determining the etch rate of the silicon oxide layers.