SIZE-SCALABLE, 2.45-GHZ ELECTRON-CYCLOTRON-RESONANCE PLASMA SOURCE USING PERMANENT-MAGNETS AND WAVE-GUIDE COUPLING

A plasma is produced in 1-10 mTorr Ar using 200-700 W of power at 2.45 GHz in a 20-cm-diam vessel. Electron cyclotron resonance (ECR) condit ions are produced with an array of permanent magnets arranged over the surface of the dielectric waveguide window. No electromagnet coils ar e used. The microwave circuit is nonresonant and can be easily matched to the power source using an E-H waveguide tuner. The 20-cm-diam plas ma is 16 cm long, and is surrounded mainly by grounded metal walls. Th e plasma expands from the ECR source region at the window and complete ly fills the chamber. Measurements of the electron density, electron t emperature, and plasma space potential have been made as functions of spatial position using Langmuir probes. The denSity ranges up to 6 x 1 0(11) cm-3 and the electron temperature is in the 2 eV range. The dens ity axial and radial profiles are described by an ambipolar diffusion model which accounts for ionization in the bulk plasma. By applying th e same permanent magnet arrangement to a rectangular waveguide, rectan gular modules can be made which can be arranged in an array to produce a large-area plasma source with independent power control for each wa veguide channel.