Ion-assisted etching of silicon by SF6

Sputtering of silicon by 3-keV Ar+ ions in the presence of a molecular SF6 beam has been investigated by mass spectrometry and time-of-flight measurements. At temperatures below 100 K chemical reactions are induced between the silicon and an adsorbed layer of SF6 under ion bombardment leading to newly formed molecular products. The main products formed are SiFx′ (x=0–4) and a small amount of SiSFy compounds (y=0–2). The kinetic energies of these molecular species are for the major part in the 0.1-eV region which excludes evaporation at substrate temperature to be a dominant mechanism for erosion. An effective sputtering yield for silicon of approximately 15 is obtained.