Optical and mass spectroscopic analysis of SF6 RIE plasmas for modelling of poly-silicon etching

SF sub 6 RIE plasmas during poly-silicon etching are investigated by optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS). The variations of the feed gas flow and the silicon substrate area are used to derive a simple model function for the poly-Si etchrates. It suggests a combination of pure chemical etching by atomic fluorine and chemically enhanced sputtering by the predominant positive ions, namely SF plus sub 3. A reaction probability of atomic fluorine with poly-Si is found to be about 0.04.