SiO 2 Etching using high density plasma sources

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Plasma characteristics of a M=0 type helicon wave plasma source and an UHF type plasma source were comparatively studied for the purpose of applying in SiO 2 etching processes. Helicon wave and UHF type plasma sources were operated at the excitation frequencies of 13.56 and 500 MHz, respectively. Optical emission spectroscopic data pointed out that the concentration of the CF 2 radical is higher in the UHF type plasma source than in the helicon wave plasma source. This indicates that the degree of dissociation of the feed gases is lower in the UHF type plasma source. The ion saturation current obtained with the UHF type plasma source is almost independent of the pressure. Therefore, the etch rate shows less variation with the applied pressure. In addition, the RIE lag also shows only a smaller change with the applied pressure. On the other hand, the ion current density and the etch rate obtained with the helicon wave plasma source show a considerable change with the pressure. These data demonstrate that the UHF type plasma source provides a wider process window for SiO 2 etching than the helicon wave plasma source.