Near threshold sputtering of Si and SiO2 in a Cl2 environment

Abstract

Si sputtering yields and Si to SiO2 etch rate ratios have been determined by measuring the depth of the etched craters after Ar+ ion bombardment. The experiments have been performed with energies down to 50 eV both with and without Cl2. Surprisingly high Si sputtering yields are obtained in a Cl2 environment by low-energy Ar+ ions. Hence, the influence of Cl2 on the Si sputtering mechanism is much larger for low ion energies than for high ion energies. Whereas the Si sputtering yield is enhanced by the presence of Cl2, the SiO2 sputtering yield is hardly affected. Therefore, large differences in the etch rate (high selectivities) between Si and SiO2 are obtained at low ion energies.