Multiple steady states in a radio frequency chlorine glow discharge

Multiple steady states have been observed in a 13.56 MHz chlorine glow discharge in a parallel plate radial flow reactor. Measurements of the flux and energy distribution of positive ions bombarding the electrode are reported along with radial profiles of atomic chlorine (Cl) concentration and etch rate of polysilicon for different states of the plasma. At the same operating conditions the plasma may exist in one of two states. In one state the plasma appeared radially uniform, resulting in relatively uniform radial Cl concentration profiles and etch rate. In the other state the plasma appeared radially nonuniform with a higher intensity central region ("plasmoid"). The etch rate and Cl concentration profiles were nonuniform in the presence of the plasmoid. The plasmoid generally appeared under conditions of high power and pressure and could be eliminated by adding noble gases and/or decreasing the electrode spacing. The multiple states may be a result of the strongly electronegative nature of the chlorine discharge.