Chemical and Physical Roles of Individual Reactive Ions in Si Dry Etching

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Abstract
Chemical and physical sputtering yields of silicon by fluorocarbon ions such as F+, CF+, CF2 +, CF3 + and C+ were investigated as a function of incident ion energy. Yield measurements over the 100–3000 eV incident ion energy range were performed through the use of mass-selected single species ion beam etching and in situ quartz crystal oscillator in an ultrahigh vacuum atmosphere. It was found that Si surface was fully covered with carboneous polymer and carbon in the cases of CF+ and C+ irradiation in the energy ranges of 100–700 eV and 100–2500 eV, respectively. Small quantity of carbon accumulation was also observed in the CF2 + ion beam irradiation of silicon in the 100–200 eV region, on the other hand, no carbon accumulation took place for F+ and CF3 + ion beam cases. In conventional Si dry etching by a CF4 gas plasma, since low energy (less than 1000 eV) fluorocarbon ions impinge the etched surface, it can be concluded that suppression of silicon etch rates mainly arises from the incidence of C+ and CF+ ion species.

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