SIMULATIONS OF MULTIPACTOR-ASSISTED BREAKDOWN IN RADIO-FREQUENCY PLASMAS

Breakdown in low pressure radio frequency (rf) plasmas is investigated with particle-in-cell simulations in a model gas based on argon. A on e dimensional model with a realistic rf-wave form is used in a range o f pressures between 1 and 50 mTorr. Dynamic scaling and electron gener ated secondaries are introduced in order to simulate breakdown realist ically, and it is possible to follow the discharge development from a few initial electrons to the steady state plasma with n(e) similar to 10(9) cm(-3). The results confirm that breakdown is controlled by the resonant multiplication of secondary electrons known as the multipacto r. For the pressures investigated, however, ionization is the main sou rce of new charges and a model based on a typical electron trajectory is introduced to account for the growth in the number of electrons in the discharge gap, The model is in good agreement with the simulation results. (C) 1996 American Institute of Physics.