PERFORMANCE-CHARACTERISTICS OF A MICROWAVE PLASMA SOURCE USING AN AXIAL MIRROR AND MULTIPOLE MAGNETIC-FIELDS

The performance characteristics of a microwave plasma source are presented. The plasma source consists of two chambers: chamber 1 generates a high-density plasma over which a magnetic field is applied at electron cyclotron resonance condition or greater, and chamber 2 makes the plasma uniform in its lower region by surrounding the peripheral region with magnetic multipole line-cusp fields. Plasma parameters were measured with a movable Langmuir probe located 1 cm above a plasma grid which is attached at the bottom of chamber 2. The dependence of plasma parameters on the magnetic field configuration, gas pressure and microwave power were examined, and radial distributions were measured. Uniform high-density plasmas over a 9-cm-diam area were produced on the plasma grid in a suitable magnetic field configuration, and uniformity was maintained over a wide pressure range. The uniform density region was determined by the magnetic multipole fields existing in chamber 2's peripheral region. The ion beam current density evaluated from the extracted ion beam correlated well with the ion saturation current density estimated from the plasma parameters.