RELATION BETWEEN THE RF DISCHARGE PARAMETERS AND PLASMA ETCH RATES, SELECTIVITY, AND ANISOTROPY

The ion energy transport 'ellipsoid' generated by the electric field across the plasma sheath is shown to induce anisotropic etch reactions and, under certain circumstances, to 'enhance' the intrinsic chemical etch selectivity. The plasma sheath electric field is shown to be determined by observable rf discharge parameters. The rf discharge is reduced to an equivalent circuit, which relates the time averaged plasma body and sheath electric fields to the rf discharge parameters of plasma geometry, current or power and discharge excitation frequency. We find two regimes of excitation frequency, for otherwise identical conditions, generating much larger sheath electric fields below than above the ion plasma frequency.