Development of compact electron cyclotron resonance plasma source

Abstract

Although it is well known that electron cyclotron resonance (ECR) produced plasmas are efficient, high-density sources and have potential applications in industry, a compact ECR plasma source still remains to be developed. This paper discusses the development of a novel, compact ECR plasma source (CEPS) that is both portable and easily mountable on a chamber of any size. The design of the CEPS is based on our detailed investigations of microwave coupling into a plasma loaded conducting waveguide and its subsequent absorption by the ECR process. It treats the plasma source section of the CEPS like a plasma loaded waveguide which can support a number of guided plasma waves that are both resonant (resonating at ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> ≈ ω), and non-resonant (propagating through the ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> ≈ ω layer). Also, these modes suffer a reversal of polarization along the radius (from right hand polarized to left and vice versa) so that both azimuthal modes m = + 1 (RCP on axis) and m = - 1 (LCP on axis) are absorbed with equal ease. The design of the CEPS uses a fully integrated microwave line (including a quartz, microwave window) for operation at 2.45 GHz, 800 Watts, cw. The required magnetic field is produced by a set of suitably designed NdFeB ring magnets. The paper discusses the development of the CEPS in light of the above physics issues and presents characterization results using a single CEPS. These CEPS were developed for very large volume plasma production and up to twelve such sources have also been used for producing plasma in a large volume plasma system (diameter ≈ 1m, height 1.55 m).