Physics of helicon discharges

Abstract

Because of their high density, low-pressure discharges ionized by helicon waves are being studied for their possible use in cluster tools for the fabrication of next-generation computer chips. How helicon waves are related to whistler waves and waves in a plasma-filled waveguide is explained, and the mystery of the high ionization efficiency is outlined. Experimental data on the waves and the equilibrium properties of the discharge are shown, and the status of our current understanding of the physical processes therein is summarized. The importance of kinetic effects and of a short-wavelength mode arising at low magnetic fields is evaluated. Applications of helicon discharges to such diverse fields as plasma accelerators, microwave generators, and tokamak physics are illustrated. Low-temperature plasma physics is often considered a discipline so different from high-temperature plasma physics that there is little overlap, but these studies show that the techniques developed in fusion and space plasma physics can be applied to technological plasmas as well.