On the electron heating mechanism in a planar helical resonance plasma

Since a helical resonance plasma does not require a matching network, enabling high-efficiency discharges and it is a promising next-generation etch process source. An electron energy probability function (EEPF) is measured in a planar helical resonance argon plasma. A resonance occurs in the planar type helical antenna when the length of the antenna is 1/4 of the wavelength of applied power. At low pressures, the EEPF changes from a bi-Maxwellian to a Maxwellian distribution as the applied power increases from 1 to 200 W. At high pressures, the EEPF evolves from a Druyvesteyn to a Maxwellian distribution as the applied power increases. It is found that there is a change in electron heating mechanism in the planar helical resonance plasma as the applied power increases, which is very similar electron heating mechanism as in inductively coupled plasmas.