On the relative importance of physical and chemical sputtering during ion-enhanced etching of silicon by XeF₂

Product translational energy distributions have been used in previous studies as a diagnostic of surface reaction enhancement mechanisms under ion bombardment. Haring and co-workers [R. A. Haring, A. Haring, F. W. Saris, and A. E. de Vries, Appl. Phys. Lett. 41, 174 (1982)] have taken an E-2 dependence for SiFx species desorbing during ion-enhanced etching of silicon as evidence for the importance of physical sputtering. In this work, the translational energy distribution of SiF 4 desorbing from the surface of silicon during spontaneous etching by XeF2 has been obtained from modulated beam measurements. The distribution deviates markedly from a thermal distribution at the surface temperature and exhibits an E-2 dependence at high energy. Observation of this energy dependence both with and without ions suggests that translational energy distributions may not provide a unique signature for chemical and physical sputtering.