Electron energy control in an inductively coupled plasma at low pressures

A method of electron energy control was studied in an inductively coupled plasma that employed a multimode antenna, for high performance in device fabrication plasma processes. The electron energy was reduced by changing the azimuthal mode of a one-turn antenna from m = 0 to 2 with no notable change in electron density. Langmuir probe measurements showed that the electron energy reduction was more pronounced in the higher modes and at lower pressures. The antenna size was also a critical parameter. These results were confirmed by optical emission spectroscopy. It was found to be essential for the energy control that the distance between the induction-field reverse points is shorter than the electron free path. (C) 2000 American Institute of Physics. [S0003-6951(00)02510-9].