Characterization of an oxygen plasma by using a Langmuir probe in an inductively coupled plasma

Oxygen plasmas were investigated by using a Langmuir probe for an inductive ly coupled plasma with various rf powers, 100 similar to 400 W, and operati ng pressures; 0.1 similar to 100 mTorr. The probe current ratio ct of the p ositive and negative currents (I-+(*)[I-e(*) + I--(*)]) increased with the generation of negative ions and had its maximum value in the;pressure regio n of 40 similar to 70 mTorr. Also, the operating pressure to achieve the ma ximum ct shifted from the low-pressure region to the high-pressure region w ith increasing input power because enhanced ion loss through positive-negat ive ion recombination.