A study of Si plasma etching in CF4+O2 gas with a planar-type reactor

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Abstract
The plasma etching of silicon has been performed on both electrodes with a conventional parallel‐plate‐type reactor. The optical emission intensity and the etch rate were measured as a function of O2 content in CF4 gas. These measurements were carried out both with and without silicon loading wafers on the anode. The experimental results show that the O2 contents where the etch rate and the F emission intensity show the peak value do not coincide, as was pointed out by a previous author. The relation of the F emission intensity and the etch rate on the anode is well described by the competitive mechanism between F atoms and O atoms. When the Si loading wafers are placed on the anode, the F emission intensity and the etch rate can be predicted by combining this competitive theory with a continuity equation for F atoms. On the other hand, the etching mechanism of etching on the cathode cannot be interpreted only by the competitive theory. In order to interpret it in the future, one has to take into account etching species other than F atoms and/or species assisting the etching, which have little dependence on the O2 content.