Etching Efficiency for Si and SiO2 by CF+x, F+, and C+ Ion Beams Extracted from CF4 Plasmas

Fluorocarbon (CF+x), fluorine (F+), and carbon (C+) ion beams with highcurrent density (50<Ji<800 μA/cm2) were irradiated to Si and SiO2surfaces to investigate the influence of the ion species on the etchingefficiency. The ion beams were extracted from magnetized helicon-wave CF4plasmas operated in pulsed modes. The CF+3 beam had the largest etchingefficiency for Si at the same beam energy. When the same data weresummarized as a function of the momentum of the incident ion beam, thedifference in the etching efficiency became small, although the CF+3 beamstill had a slightly larger etching efficiency. On the other hand, theetching efficiency for SiO2 by the CF+3 beam was larger than that by theother ion beams in the low-momentum region. In addition, in the low-momentumregion, the etching efficiency for SiO2 by CF+3 was larger than that forSi. These results suggest the high chemical reactivity of CF+3 with SiO2,leading to the high etching selectivity of SiO2 over underlying Si in thefabrication of semiconductor devices.