Test-Wave Measurements of Microwave Absorption Efficiencyin a Planar Surface-Wave Plasma Reactor

Abstract

A major obstacle for experimental surface-wave (SW) excitation and propagation studies in SW plasma is the self-consistent behaviour of the latter, which does not permit continuous variation of the electron density n e . In the present study, we demonstrate how this obstacle can be overcome by an independent plasma source, in our case, an inductively coupled plasma (ICP) created by a high-power RF (13.56 MHz) generator. Through a rectangular waveguide short-circuited at its end by a movable plunger, we introduced into the ICP a weak (power less than 20 W) nonionising 2.4 GHz microwave. This permitted us to highlight important SW excitation and propagation phenomena. In particular, we confirmed the existence of the predicted [Jpn. J. Appl. Phys. 36 (1997) 4704] resonance minima in the n e dependence of the power reflection coefficient. The influence of the plunger position on the chamber matching was studied systematically and four different coupling aperture geometries were compared.