Numerical methods and time-dependent physical models for the design and diagnostic of pulsed-dc magnetrons

Pulsed DC operation of magnetrons is a relatively new sputtering technique that significantly improves the properties of deposited layers. The understanding and control of phenomena taking place during pulsed DC sputtering requires new time-resolved methods of investigation. This thesis presents a comprehensive development of new methods for magnetron design and time-resolved plasma diagnostic, based on Monte Carlo simulations and timeresolved plasma physical models derived for a pulsed DC opposed target magnetron discharge with rectangular geometry. The numerical methods have been developed and benchmarked by the author through extensive numerical experiments. A representative set of application examples is included. The time-resolved physical models for the pulse-on and pulse-off time discharge are based on the experimental data obtained by the author, which are presented as a basis for the interpretation. The experimental data are obtained using new time-dependent diagnostic methods combining: I-V characteristics and waveforms, time and space-resolved Optical Emission Spectroscopy (OES) and time and space-resolved Ion Energy Spectra (IBS). The following original algorithms and new time-resolved plasma diagnostic methods arc presented: • Algorithm and method for Monte Carlo simulation of ion transport in the magnetron discharge, based on an original non-Runge-Kutta routine developed for calculating charged particles’ trajectories in complex, position dependent, magnetic and electric fields. The Monte Carlo simulation is used for evaluating the intensity of the pre-sheath electric field through calculations of the travel time to targets of Ar ions. The time-scale for the sputtering and selfsputtering processes is also evaluated. A new method for time-resolved plasma diagnostic in pulsed DC discharges based on time and space-resolved OES using an acousto-optic spectrometer. The described method indicates the applicability conditions for electron temperature evaluations based on timeresolved OES. the procedure and interpretation of results. Based on time and space-resolved OES evaluations of electron temperatures, a model of the physical phenomena taking place in the pulsed DC discharge during the pulse-on time is developed. A new method for time-resolved analysis of the Ion Energy Spectra at the substrate region in pulsed DC discharges using a mass-energy analyser. Experimental results and data analysis are presented and an original physical model for plasma behaviour during the pulse-off time is developed, explaining the mechanism for the observed increase in the ion flux and energy at substrate during pulsed DC discharges. The described model explains for the first time the above effects and allows the control of the ion flux and energy at the substrate from the choice of the pulsed DC duty cycle. The developed plasma models and time-resolved diagnostic methods are discussed for nonferromagnetic(copper) and ferromagnetic (iron) targets and the observations are correlated in order to infer a global understanding of phenomena taking place in the pulsed DC discharge and at the substrate region