ION-ASSISTED SI XEF2 ETCHING - TEMPERATURE-DEPENDENCE IN THE RANGE 100-1000 K/

The Ar+-ion enhanced Si(100)/XeF2 reaction is studied in a multiple be am setup for silicon temperatures from 100 K up to 1000 K. The XeF2 fl ux is 2.7 monolayers/s and the Ar+ flux 0.033 monolayers/s at an energ y of 1000 eV. Both the XeF2 consumption and the SiFx production are me asured by mass spectrometry. The enhancement of the etch rate peaks ar ound 250 K as is observed in both the XeF2 and SiFx signals. The gradu al decline above 250 K is attributed to a diminished surface fluorinat ion and XeF2 precursor concentration. The dropoff below 250 K is presu mably caused by sputtering of the XeF2 precursor, as is concluded from the temperature dependence of the XeF+/XeF2+ signal ratio. Around 175 K this decrease is so strong that the ions seem to no longer enhance, but rather reduce, the etch rate. Below 150 K the ions are driving th e etch process. In this range the spontaneous process is blocked by Xe F2 condensation, but the ion-assisted process continues due to sputter ing or dissociation of the condensate. (C) 1996 American Vacuum Societ y.