FOCUSED GA ION-BEAM ETCHING OF SI IN CHLORINE GAS

Etch yield (the number of removed atoms per ion) of Si by showered Ga ion-beam-assisted etching with Cl2has been measured as functions of gas molecule flux impinged on the sample surface and incident ion flux. It is shown that these results are in good agreement with a theoretical model in which a volatile compound of SiCl4is created proportionally to the coverage of adsorbed chlorine molecules during ion irradiation. The maximum etch yield reaches 47 and 36 Si atoms/ion for 20 and 5 keV Ga ion, which are nearly proportional to the energy transferred from the incident ion to a lattice system of Si. This etching model is extended to the case of engraving by raster scanning of a focused Ga beam and compared with the experiment. The trends of both results coincide with each other, though the higher ion flux produces a Ga condensation layer which decreases the etch yield. © 1990 IOP Publishing Ltd.