The effects of mixing molecular gases on plasma parameters in a system with a grid-controlled electron temperature

Plasma parameter variations as a function of a mixing ratio in an electron temperature control system using a grid are investigated. Under the grid, the electron temperature, as well as electron density, is a strong function of a mixing ratio. The electron temperature decreases with a mixing ratio of molecular gases (O-2 and CF4), and the large inelastic cross section of molecular gas is the reason for the decrease in the electron temperature. When the length of sheath around the grid wires is comparable to the space between the grid wires, only 10% mixing of CF4 decreases the electron temperature to 0.8 eV in 10 mTorr Ar/CF4 plasma. (C) 2002 American Institute of Physics.