In the Center for Non-equilibrium Processes we have developed several types of RF systems. The main characteristics that connects all of these, in geometry and volume significantly different devices, is that all can be applied in the plasma treatments of sensitive materials.
We have two large scale low pressure capacitively coupled asymmetric plasma reactors (~0.5 m3 and ~2 m3). Both have axially placed aluminum rod that serves as powered electrode while grounded electrode is chamber wall itself. This geometry allows stable plasma conditions without streamers, which is suitable for treatment of sensitive samples that can withstand vacuum. Recently, another plan parallel CCP RF system is constructed with the shower-head electrode. Diameter of the electrodes is 12 cm with the gap that can be adjusted in the range of few centimeters up to 15 cm. Several diagnostic techniques are used in characterization of these systems: Langmuir probe, mass spectroscopy, OES, actinometry and derivative probes.
Nominal forwarded power is not equal to the power transmitted to the plasma and therefore for all reactors we have employed derivative probes, placed directly on central rod, to precisely determine (with an error of less than 1 W) how much power is supplied to the discharge. In order to completely understand plasma chemistry mass spectrometer was used. Electron and ion densities and electron energy distributions in plasmas were measured by Langmuir probe. OES provided information about distinctive lines and actinometry method was used for determination of densities of oxygen species.