EQUILIBRIUM PROFILES FOR RF-PLASMA SOURCES WITH PONDEROMOTIVE FORCES

An analysis is given of the influence of the electron ponderomotive force on the equilibrium plasma profiles of partially ionized, radio frequency discharge sources. The ponderomotive force can be written as a gradient of a potential varying with the square of the RF field in the plasma and is largest for electrons. The impact of this electron ponderomotive force on density and electrostatic potential profiles is demonstrated using a one-dimensional analytic model with supporting numerical solutions and a two dimensional fluid simulation. For nearly collisionless plasmas, the ponderomotive force is valid when omega(ce)(h)/omega < 1 where omega(ce)(h) is the electron cyclotron frequency due to the RF magnetic field and omega is the RF driving frequency. In processing plasmas with parameters that satisfy this validity criteria, the equilibrium density profiles are weakly modified, For nearly collisionless processing plasmas with parameters such that omega(ce)(h)/omega > 1, the ponderomotive force, is modified by other nonlinear force terms that need to be evaluated.