DFG Sonderforschungsbereich Transregio 87: Pulsed high power plasmas for synthesising nanostrucutured functional layers
The chair of Theoretical Electrical Engineering has two subprojects in the SFB-TR 87 funded by the DFG.
Subproject C4: Kinetic simulation of technical plasmas in the frequency range from DC to MW
Project manager: Dr. Denis Eremin
The characteristics of plasma assisted separation processes depend on the flow as well as the energiy and angular distribution of the particles that impinge on the substrate. In the low-pressure range (< 10 Pa), the particles can only be calculated kinetically. In the first phase of the project, we plan to further develop the electromagnetic Particle-In-Cell-Code, which is used to simulate capacitive discharges. The kinetic simulations of RF, MW, and HPPMS discharges will be performed on graphic cards. However, since MW and HPPMS plasmas have different characteristics than RF plasmas, new algorithms have to be developed and implemented. The old algorithms will either be supplemented or completely replaced. For an improved resolution of the thinner edge layers, adaptive particle algorithms have to be developed on non-uniform grids. To simulate MW discharges, the electromagnetic fields have to be calculated with the FDTD method. As of yet, this is based on the Darwin approximation of the Maxwell equation. After implementing, verifying, and validating the numerical tools, the developed Codes will be used for the analysis of the physics as well as the optimisation of the according experimental units from all research areas of SFB-TR 87.
Subproject C5: Electron dynamics of magnetised high power plasmas, especially HPPMS
Project manager: Prof. Dr. Ralf Peter Brinkmann
Many layer deposition processes, e.g. High Power Pulsed Magnetron Sputtering (HPPMS), use magnetised high power plasmas at low pressure. In this regime, fluid dynamic models are not valid and have to be replaced by kinetic models. The state of technology is represented by self consistent Particle-in-Cell/ Monte Carlo simulations. The effort of such simulations, however, scales quadratic with the plasma density; in the HPPMS regime they can only be used for simple model systems.
C5 wants to develop an alternative kinetic algorithm that is also evaluable for realistic HPPMS plasmas. The electron component is the main focus here; Ions and neutral particles are part of subproject C8. in the past period, the important basics were worked out. A kinetic model of electron dynamics was developed and linked to a rate equation system for the ions and neutral particles. With this global model, the distribution of electron energy in the active area of a high power magnetron was researched for realistic parameter areas. The distribution turned out to be substantially bimodal, a minority of energetic elektrons is faced with a dominant thermal component.
For this thermal component, a kinetic theory was developed and mapped onto a formal, two-dimensional, kinetically easily accessible equation system via extensive pertubative calculations. Parallely, the interaction of magnetised electrons with a static plasma edge layer was researched, resulting in gaining adequate constraints. In the upcoming funding period, a Monte Carlo model is planned to b realised for the energetic electrons. Linking both electron models to the heavy particles model, will enable an efficient and realistic simulation of HPPMS process for the first time. In doing so, fundemental phenomena of magnetised plasma processes (e.g. the cross-field transport, modes of an electron heating, and the spontaneous appearance of so-called spokes) are supposed to be researched from first principles. Additionally, a predictive simulation of industrial plants significant for coating processes is to be carried out with regards to their size and time scales.
C5 also concerns itself with the plasma edge theory and the model-based plasma diagnostics.