Reactive ion beam etching of SiO2 and polycrystalline silicon

Reactive ion beam etching experiments using a collimated ion beam and the gases CF4, C2F6, and C3F8 have been conducted. At a beam current density of 0.4 mA/cm2 and ion energies from 0.5 to 1 keV the etch rates of SiO2 and polycrystalline silicon were 650 and 65 A/min, respectively, with C2F6 and C3F8. The etch selectivity was 10 to 1 for these gases though less than 2 to 1 for CF4. No undercutting was observed using this method.