ION-BEAM-ASSISTED ETCHING OF SI WITH FLUORINE AT LOW-TEMPERATURES

The ion-assisted etching of Si with F atoms has been studied over the temperature range from 77 K to room temperature. Separately controllab le beams of F atoms and 1 keV Ar+ ions are used in an ultrahigh-vacuum environment. Neutral etch products are measured with modulated beam m ass spectrometry. The ion-assisted etch rate is seen to increase as th e temperature is decreased whereas the spontaneous etch rate goes to z ero at low temperatures. The nature of the etch products is essentiall y independent of temperature over this temperature range. Evidence is presented indicating that the spontaneous etching of Si by F atoms at 77 K is blocked by the formation and condensation of Si2F6. (C) 1994 A merican Institute of Physics.