Ion-assisted Si/XeF2-etching: Influence of ion/neutral flux ratio and ion energy

The Ar+ ion-enhanced Si(100)/XeF2 reaction at 300 K is studied quantitatively in a molecular beam setup. Measurements are done for XeF2-fluxes from 0.1 up to 3.4 monolayer/s, Ar+-fluxes from 8 x 10(-4) up to 8x10(-2) monolayers/s and Ar+-energies of 500, 1000 en 2000 eV. Both the XeF2 consumption and the SiFx production are measured by mass spectrometry. It is concluded that physical and chemical sputtering are the only significant ion-induced mechanisms: damage-enhanced etching and enhanced spontaneous etching can be neglected. The flux dependence of the etch process is found to be solely determined by the ratio of the ion over the neutral flux. This behavior is described by a simple kinetic model. From the energy dependence it is concluded that both the physical and the chemical sputtering contributions scale with the square root of the ion energy. The ion-enhanced Si/XeF2 reaction is most efficient for ion/neutral ratios of 0.1 and higher: 80% of the XeF2 is then consumed in the reaction process versus 10% during spontaneous etching. It is concluded from the mass spectrometer signals that under these conditions between 35% and 61% of the SIFx products are released by physical sputtering and the remainder desorbs by chemical sputtering. (C) 1996 American Vacuum Society.