High homogeneity 25 cm low-energy rf ion source with inherent electron compensation

A 25 cm single-grid low-energy rf ion source with inherent electron compensation is described and characterized. Measurements were carried out using Ar and CF(4) filling gas. The dependence of the ion beam current to the target as well as the current partition between the beam fast and slow ions on the rf discharge pressure for both filling gases is discussed. The unique ability of generation of coinciding ion and electron flows is demonstrated and the measured ion and electron energy distribution functions are presented as well. The developed broad ion beam source is able of providing 0.5-5 mA/cm(2) current density in the low ion energy range of 50-250 eV, with possibility of independent current density and energy control. It is shown that complementing the rf plasma source with a profiling electrode allows for CF(4) ion source operation attaining +/-5% ion beam uniformity over 250 mm in diameter. The presented CF(4) etching test results exhibit the possibility of highly directional anisotropic Si and SiO(2) etching utilizing the developed single grid rf ion source.