Reactive sputtering by SF6 cluster ion beams

Reactive gas cluster ion beams were formed by an adiabatic expansion of SF6 with He mixture through a Laval nozzle and their reactive sputtering effects with solid surfaces have been studied. Si, W and Au samples were irradiated with SF6 cluster ion beams at an energy of 20 keV. Due to the chemical reaction of SF, clusters with Si and W, sputtering yields of Si (1300 atoms/ion) and W (320 atoms/ion) were dramatically enhanced compared with those by Ar cluster ions (Si: 24, W: 35 atoms/ion). Sputtering yields of SF6 cluster ions increased exponentially with the increase of acceleration energy, on the contrary, those of Ar cluster ions were proportional to the energy. Chemical reaction is the predominant sputtering process at an energy of around 5 keV. A Si(100) surface irradiated with SF6 cluster ions was quite smooth, because of the smoothing effect of cluster ions.