ION FLUX AND ION POWER LOSSES AT THE ELECTRODE SHEATHS IN A SYMMETRICAL RF DISCHARGE

Ion flux and ion acceleration power have been measured at the electrode sheath in a capacitively coupled argon discharge driven at 13.56 MHz. Two independent methods have been used to evaluate the ion power. One method is based on measuring the ion current to an rf electrode and the dc component of the rf sheath voltage. The other method is based on measuring the discharge power as a function of the total discharge current. Measurements were performed at gas pressures between 3 mTorr and 3 Torr and at discharge powers between 10(-2) and 10(2) W. Over the entire range of operation the ratio of the ion to discharge current varied between 1% and 3%, whereas the percentage of the ion power loss was between a fraction of a percent and 95% depending upon the total discharge power. The series equivalent resistance corresponding to the ion power loss was found experimentally and corresponds well with predictions based on a dynamic sheath model.