AVS 58th Annual International Symposium and Exhibition
    Plasma Science and Technology Division Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA8
Probe Diagnostics Instrument for Laboratory and Industrial RF Plasmas

Tuesday, November 1, 2011, 4:20 pm, Room 201

Session: Plasma Diagnostics, Sensors and Control I
Presenter: Valery Godyak, RF Plasma Consulting
Correspondent: Click to Email
Contemporary probe diagnostics of low pressure rf discharge non-Maxwellian plasmas implies the measurement of electron energy distribution function, EEDF and variety of plasma parameters found as the corresponding EEDF’s integrals. There are four major problems in implementing of meaningful probe diagnostics in rf plasma reactors. They are: a) large frequency spectrum with significant amplitudes of the plasma rf potential corresponding to source and bias fundamental frequencies and their harmonics; b) low frequency noise due to plasma instability and ripples in an rf power source, c) too high impedance between the plasma and grounded chamber due to limited surface of the chamber and its contamination or/and an artificial protective coating, and d) contamination of the probe surface with a low conductive layer of the reaction products. The probe characteristic distortion caused by these factors are hardly recognized when one just follows Langmuir procedure to infer plasma parameters assuming Maxwellian EEDF, since distorted and undistorted probe characteristics look similarly. But the problem becomes apparent after double differentiation of the distorted probe characteristics (to infer the EEDF) due to error augmentation inherent to differentiation procedure. A probe diagnostic system VGPS® [1], addressing the aforementioned problems has been designed and tested in the variety of rf plasmas in basic research experiment and in different rf plasma reactors. Examples of EEDF measurements with high energy resolution (small fraction of Te) and large dynamic range (3-4 orders of magnitude) in laboratory and industrial rf plasmas, are given in this presentation.