Etching process of silicon dioxide with nonequilibrium atmospheric pressure plasma

An ultrahigh etch rate (14 mu m/min) Of SiO2 and a high selectivity of SiO2/Si over 200 were achieved using a microwave-excited nonequilibrium atmospheric pressure plasma source employing He, NF3, and H2O gases, which have been developed for application to microelectromechanical systems and other bionanotechnology fields. In order to clarify the etching mechanism, two diagnostic methods have been performed: (1) imaging of plasma emission with an intensified charge-coupled device camera, and (2) absorption measurements using Fourier transform infrared spectroscopy. The etching characteristics are discussed in relation to the spatial distributions of the species involved. The etch rate depended considerably on the distance between the plasma and the substrate. Some radicals generated from the feed gases reached the substrate directly, while other radicals recombined into different species, which reached the substrate. An abundance of HF molecules were produced through a reaction between radicals generated by the atmospheric pressure discharge of NF3 and H2O. From these measurements, it has been found that the HF molecules generated played a role in producing the high etch rate Of SiO2 and high etch selectivity of SiO2/Si. (c) 2005 American Institute of Physics.