ELECTRICAL POTENTIALS IN RF DISCHARGES

A theory is presented of the electrical nature of capacitatively coupled RF discharges of the type commonly encountered in microcircuit fabrication. Using arguments bearing on ion and electron fluxes associated with the cathode and anode, an expression is developed relating the ratio of the DC self-bias, VDC, and the applied RF voltage, V0, to the relative electrode areas, and a formula is given for the plasma potential. Good agreement is achieved for a range of experimental data of V0, VDC and plasma potential and the observed relationship in the work of Coburn and Kay (1972) between the ratio of the sheath voltages and the electrode area ratio is convincingly reproduced. The theory promises considerable predictive power which may be of value for the design of RF reactors, especially with regard to the control of ion impact energies at substrate surfaces. © 1990 IOP Publishing Ltd.