Mechanisms of sputtering of Si in a Cl2 environment by ions with energies down to 75 eV

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Abstract
Sputtering of Si in a Cl2 environment by Ar+ and Xe+ ions with energies down to 75 eV has been investigated. Mass spectra and time‐of‐flight distributions of the sputtered species have been measured. Under 75‐eV Ar+‐ion bombardment of the Si target, SiCl, SiCl2, SiCl3, and/or SiCl4 are sputtered. When increasing the ion energy the SiCl4 contribution decreases in comparison with SiCl. This is caused by the fact that the newly formed Si‐Cl compounds are sputtered at a high rate compared to the rate of SiCl4 formation. Time‐of‐flight distributions indicate that under 100‐eV Ar+‐ion bombardment the species are not sputtered by a collision‐cascade mechanism. The spectra can be fitted by Maxwell–Boltzmann distributions at a high (>2000 K) temperature. Increasing the Ar+‐ion energy to approximately 250 eV the time‐of‐flight spectra of the sputtered species change from Maxwell–Boltzmann‐like into spectra as expected for a collision‐cascade mechanism. For low‐energy Xe+ ion bombardment the sputtered species also show Maxwell–Boltzmann time‐of‐flight distributions. The change from Maxwell–Boltzmann to collision‐cascade distributions occurs at higher ion energies than for Ar+‐ion bombardment. The results obtained for low ion energies are discussed in terms of evaporation from an ion‐induced hot spot.

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