Influence of different coil geometries on the spatial distribution of the plasma density in planar inductively coupled plasmas

The radial distributions of the electron density and the relative atomic argon excited state density have been investigated by means of Langmuir probes and optical emission spectroscopy, respectively, in planar inductively coupled plasmas. The plasma source is a modified Gaseous Electronics Conference RF Reference Cell [P. J. Hargis et al., Rev. Sci. Instrum. 65, 140 (1994)]. Two different planar coil geometries, a five-turn spiral coil and a one-turn circular coil, were investigated for a variety of plasma parameters. Additionally, we investigated the effect of different powering configurations of the spiral coil and an electrostatic shield between the coil and the plasma. We found that the coil geometry and power configuration of the coil influences the radial distribution of the electron density in the region close to the coil only, while in the region close to the lower electrode the radial distribution is dominated by diffusion. copyright 1997 The American Physical Society