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

Abstract

The Ar ϩ ion-enhanced Si͑100͒/XeF 2 reaction at 300 K is studied quantitatively in a molecular beam setup. Measurements are done for XeF 2 -fluxes from 0.1 up to 3.4 monolayer/s, Ar ϩ -fluxes from 8 ϫ10 Ϫ4 up to 8ϫ10 Ϫ2 monolayers/s and Ar ϩ -energies of 500, 1000 en 2000 eV. Both the XeF 2 consumption and the SiF x 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/XeF 2 reaction is most efficient for ion/neutral ratios of 0.1 and higher: 80% of the XeF 2 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 SiF x products are released by physical sputtering and the remainder desorbs by chemical sputtering.

Sample tilting technique for preventing electrostatic discharge during high-current FIB gas-assisted etching with XeF2

“…Considering the fact that XeF 2 and Xe are ionized to XeF + , XeF þ 2 and Xe + by 30-70 eV electrons in mass spectrometers [21][22][23], high-energy SEs produced by FIB irradiation probably cause the ionization of these gases in our case. Therefore, the ionization probability of XeF 2 and Xe increases with tilting-angle.…”