Electrical potentials in RF discharges

Abstract

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.

Ion bombardment effects on microcrystalline silicon growth mechanisms and on the film properties

“…1͑b͒. [25][26][27] Finally, imposing a dc bias on the rf electrode acts on the voltage drop across the grounded electrode sheath namely the plasma potential V p , and is therefore an additional way to vary the energy of the ions impinging on the substrate. If the applied dc bias voltage is lower than the self-bias voltage on the rf electrode, the plasma potential is consequently lowered to ensure the ion current balance on both electrodes.…”

Making a geometrically asymmetric capacitive rf discharge electrically symmetric

“…In standard CCRF discharges, a geometric asymmetry ͑A p A g ͒ leads to the generation of a dc self-bias voltage to ensure equal fluxes of positive and negative charges to each electrode on time average. [3][4][5][6] Based on an analytical model, Heil et al 7 derived an expression for ,…”

Study of the effect of different plasma-enhanced chemical vapour deposition reactor configurations on the properties of hydrogenated amorphous silicon thin films

“…To relate V DC to the areas of the electrodes we used the expression derived by Song et al (1990) : In this case the grid placed in front of the electrode stays always close to the¯oating potential V f , during the electrical oscillations of the rf powered grid.…”