Responses of electron shading consistently indicating low-energy ion effect [ICP etching]

The responses of electron shading to bias frequency and source pulsing in a Cl₂ inductively coupled plasma (ICP) etch process have been studied. A newly devised test structure, a MOS capacitor with SiO₂-shaded antenna, enabled us to extract a “pure” electron shading response. Whereas the damage in a CW plasma was independent of the bias frequency, the damage was reduced with lower-frequency bias when the plasma was pulsed. All the results, including bias voltage dependence, consistently indicates the neutralization of negative charge on the sidewall by low-energy ions