A Simple Ion Flux Estimation in a Low Pressure R.F. Plasma (13.56 MHz)

(Received 9 April 1996, revised 25 September 1996, accepted 10 January 1997)

Abstract
A new application of the sputtering rate measurement is given in this paper. In fact, by measuring the sputtering rate of different materials fixed on the radio frequency (r.f.) biased electrode, it is possible to determine easily ion flux that falls onto this biased electrode. This study is realized in a low pressure (0.4 Pa) argon planar r.f. discharge system (13.56 MHz). This sputtering method is interesting to have informations about the deposition process in physical vapour deposition. In order to demonstrate the validity of this method, experiments have been carried out in two reactors, each one with different geometrical parameters and the results obtained have been compared and confirmed using the Child-Langmuir law. The ion flux increases as a function of the incident r.f power (0-300 W). The values obtained range from 10 ¹⁸ to 10 ¹⁹ ions m ^-2 s ^-1. These results in an argon plasma are applied to estimate incident ion flux in a nitrogen atmosphere. Finally, we show that it is possible to evaluate the incident ion flux by measuring the sputtering rate when the plasma is densified using either an auxiliary hot cathode discharge or an additional magnetic field. These experimental cases correspond respectively to r.f. triode ion plating or r.f. magnetron sputtering.