This paper describes a technique for measurign the ion current at a semiconductor wafer while it is beign processed in a hgih-density plasma reactor. the technique does nto require the application of any voltage other than the rf bias voltage which is normally applied to wafers, thus avoiding any prossible perturbations to the plasma. IT relies on external measurements of the radio-frequency current and voltage at the wafer electrode. There is no need for any probe to be inserted into the plasma. To test the technique, comparisons were made with de measurements of ion current at a bare aluminum electrode, for argon discharges at 1.33 Pa, iion current densities of 1.3-13mA/cm sup 2, rf bias frequencies of 0.1-10 MHz, and rf bias voltages from 1 V to 200 V. Additional tests showed that ion current measurements could be obtained by the rf technique in electronegative gases and when electrically insulating layers or wafers were on the electrode.
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