| AVS 54th International Symposium | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS2-ThM |
| Session: | Plasma Diagnostics I |
| Presenter: | M.C. Petcu, Eindhoven University of Technology, The Netherlands |
| Authors: | M.C. Petcu, Eindhoven University of Technology, The Netherlands A.C. Bronneberg, Eindhoven University of Technology, The Netherlands M.A. Creatore, Eindhoven University of Technology, The Netherlands M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
In this work the investigation of an Ar - fed remote expanding thermal plasma (ETP) where NH3/SiH4 mixtures are injected downstream, is reported. Our interest is mainly focused on ion flux and ion densities measurements at different gas phase compositions. The ion and electron densities measurements using various methods and different plasma conditions have been previously reported in literature. For example, double and single cylindrical Langmuir probes have been successfully used to measure the ion density in non - depositing Ar/NH3 ETP. A limitation of Langmuir probe measurements is to determine the ion densities in depositing plasmas, e.g. Ar/NH3/SiH4 mixtures, due to the formation of a resistive layer on the probe. An alternative approach is to use a single-side electrostatic probe, as already proposed in literature. This technique is compatible with the presence of insulating layers, showing the potential for absolute ion flux determination. The method is based on the discharging of an RF-biased capacitance in series with the probe. An alternative method, based on the use of pulse shaped double-side capacitive probe to measure ion flux in Ar/NH3 and Ar/NH3/SiH4 plasma mixtures is here proposed. Our approach allows an accurate ion flux determination from the linear discharging of the capacitor connected in series with the collecting surface. Such approach could be easily implemented in a sensor for ion flux control in various discharges, e.g, in the case of a biased substrate to induce ion bombardment during film growth. When Ar/NH3 mixtures are investigated, a decrease of the ion flux from 1018 to 1016 cm-2s-1 as a function of the NH3 flow rate is measured and attributed to the consumption of Ar ions due to the charge exchange reaction between Ar ions and NH3 molecules, followed by the dissociative recombination with low energy electrons. These results are also confirmed by Langmuir probe measurements. Furthermore, the addition of SiH4 is showing an interesting behavior, i.e., a local increasing of the ion flux presently attributed to the formation of lighter ions, in conditions of high Ar ion depletion due to the high molecular gas flow rates. These measurements, together with mass spectrometry analysis, will be presented and commented in terms of plasma chemistry channels developed in an Ar/NH3/SiH4 plasma.