| abstract |
A method and apparatus for generating a plasma by inductively coupling electromagnetic energy into the plasma in a vacuum chamber (100). In one embodiment, first and second antenna coils (104, 106) are disposed about the circumference of the plasma containment area. The first and second antenna coils are relatively spaced along the longitudinal axis of the plasma containment area by a distance (2). A current is generated in the first and second antenna coils through amplifiers and matching networks (102, 108; 106, 112) and a single RF generator (114). A phase shift regulating network (116) establishes a difference between the phase of the current in the first antenna and the phase of the current in the second antenna. The phase difference corresponds to the phase difference required to launch a helicon wave in the plasma. In a second embodiment, a chamber shield (118) is made of a conductive material and is coupled to the RF source such that the shield functions as an RF antenna. The shield may be coupled in series to a coil surrounding the shield to increase the resultant flux density. |