The uniformity of the low-energy electron beam in an oxygen inductively coupled plasma.

The radial uniformity of the low-energy electron beam is measured, which is generated by a DC-biased grid in an oxygen inductively coupled plasma. The electron beam energy is radially uniform for various voltages applied to the grid and the substrate. However, the electron beam density is higher at the edge of the chamber than center. This is due to the source plasma above the grid, since the electron beam is generated from the high energy electrons in the source plasma which can overcome the potential barrier formed at the sheath. Therefore, the high density of high-energy electrons in the source plasma causes the high density of the electron beam. Since the electric field is higher at the edge of the chamber than the center due to the location of the antenna, electrons gain more energy at the edge of the chamber, causing higher electron temperature. Due to the inelastic collision in the oxygen plasma, electrons losses their energy, causing higher electron density at the edge of the chamber. Further, to discuss the effect of the electron beam on the spatial distribution of the negative ions, the electronegativity is measured radially. Since the electron beam can participate in the generation of the negative ions under the grid, the radial distribution of the negative ions can be affected by the uniformity of the electron beam.