TUNGSTEN ETCHING IN LOW-PRESSURE SF6 PLASMA - INFLUENCE OF THE SURFACE-TEMPERATURE

The influence of the surface temperature on tungsten etching in a SF6 plasma diffusing from a helicon source has been studied in detail. The surface temperature dependence of the etching kinetics has been analy zed. The influence of the other parameters such as oxygen content of t he plasma and ion energy have also been considered. The etching mechan ism depends on the temperature range: the etching is partly spontaneou s at higher temperatures (T > -20 degrees C), becomes a chemical sputt ering type at intermediate temperature ( -20 degrees C < T < -40 degre es C), and a chemically enhanced physical sputtering at lower temperat ure (T < -40 degrees C). Surface analyses. by x-ray photoelectron spec troscopy provide an understanding of how the surface chemistry is modi fied with temperature.