Plasma generating apparatus using magnets and method

A plasma generating apparatus which comprises:

• (a) a plasma source employing a radio frequency, including UHF or microwave, wave coupler which is metallic and non-magnetic and in the shape of a hollow cavity which can be excited in one or more TE or TM modes of resonance;
• (b) an electrically insulated chamber having a central longitudinal axis and mounted in the coupler;
• (c) gas supply means for providing a gas which is ionized to form the plasma in the insulated chamber;
• (d) a movable probe connected to and extending inside the coupler for coupling the radio frequency waves to the coupler;
• (e) a plurality of first magnets mounted around the longitudinal axis of the chamber on a ring of high permeability magnetic material so as to create magnetic cusps in the chamber which aid in confining the plasma in the chamber;
• (f) movable plate means as a sliding short in the cavity which is non-magnetic and metallic mounted perpendicular to the axis and movable towards and away from the chamber;
• (g) second magnets mounted on a sheet of high permeability magnetic material and adjacent to the plate means so as to provide magnetic cusps inside the chamber which aid in confining the plasma in the chamber;
• and
• wherein movement of the plate means and the probe in the coupler achieves the selected TE or TM mode of resonance of the radio frequency wave in the coupler and varies the resonance of the mode and wherein the radio frequency wave applied to the coupler creates and maintains the plasma at reduced pressures in the shape of an elongate plasma disk perpendicular to and surrounding the central longitudinal axis in the chamber which is confined in the chamber by the magnetic cusps.

A method for forming a plasma which comprises:

• (a) providing plasma generating apparatus including a plasma source employing a radio frequency, including UHF or microwave, wave coupler of a non-magnetic metal in the shape of a hollow cavity which can be excited in one or more TE or TM modes of resonance, including an electrically insulated chamber having a central longitudinal axis and mounted in the coupler, including a gas supply means for providing a gas which is ionized to form the plasma in the chamber, including a movable plate means of a non-magnetic metal in the cavity mounted perpendicular to the axis of the chamber and moveable towards and away from the chamber as a sliding short, including a moveable probe connected to and extending inside the coupler for coupling the radio frequency waves to the coupler, wherein movement of the moveable plate means and the probe in the coupler achieves the selected TM or TE mode of resonance of the radio frequency wave in the coupler and varies the resonance of the mode and wherein the radio frequency wave applied to the coupler creates and maintains the plasma at reduced pressures in the shape of an elongate plasma disk perpendicular to and surrounding the central longitudinal axis in the chamber, the improvement which comprises:
• a plurality of first magnets mounted on the apparatus around the longitudinal axis of the chamber on a ring of high permeability magnetic material so a to create magnetic cusps in the chamber which aid in confining the plasma in the chamber;
• and second magnets mounted on the apparatus on a sheet of high permeability magnetic material so as to provide magnetic cusps inside the chamber which aid in confining the plasma in the chamber;
• and
• (b) forming the plasma disk in the chamber confined by the magnetic cusps.

A method for forming a plasma which comprises:

• (a) providing a plasma generating apparatus which comprises a plasma source employing a radio frequency, including UHF or microwave, wave coupler which is metallic and non-magnetic and in the shape of a hollow cavity and which is excited in one or more TE or TM modes of resonance;
• an electrically insulated chamber having a central longitudinal axis and mounted in the coupler;
• gas supply means for providing a gas which is ionized to form the plasma in the insulated chamber;
• a plurality of first magnets mounted around the longitudinal axis of the chamber on a ring of high permeability magnetic material so as to create magnetic cusps in the chamber which aid in confining the plasma in the chamber;
• movable plate means in the cavity which is non-magnetic and metallic mounted perpendicular to the axis and movable towards and away from the chamber;
• second magnets mounted on a sheet of high permeability magnetic material to provide magnetic cusps inside the chamber which aid in confining the plasma in the chamber;
• and a movable probe connected to and extending inside the coupler for coupling the radio frequency waves to the coupler, wherein movement of the plate means and the probe in the coupler achieves the selected TE or TM mode of resonance of the radio frequency wave in the coupler and varies the resonance of the mode, wherein the radio frequency wave applied to the coupler creates and maintains the plasma at reduced pressures in the shape of an elongate plasma disk perpendicular to and surrounding the central longitudinal axis in the chamber which is confined in the chamber by the magnetic cusps and wherein the magnets have a field strength and position adjacent to or around the chamber sufficient to create electron cyclotron resonance in the chamber;
• and
• (b) forming the plasma disk in the chamber confined by the magnetic cusps.