Search

A reactive high-power impulse magnetron sputtering (HiPIMS) process using a titanium target in a mixture of Ar/O2 has been investigated for different modes of operation including pure argon, metallic, transition, and compound mode. The trends and changes in the plasma density ne and the effective electron temperature Teff, have been measured by the time-resolved Langmuir probe technique. The same experimental process conditions have also been studied using a recently developed reactive ionization region model (R-IRM), making it possible to compare the acquired experimental results with the model results. It was found that trends in the plasma density and mean electron energy as measured by the Langmuir probe are in good agreement with the results obtained from the R-IRM model for different pulse discharge current densities. The effective electron temperature generally increases with an increasing oxygen flow rate. It is likely due to a reduction of sputtered Ti, due to compound formation on the target, which forces the discharge to increase the electron energy to increase the ionization rate of the process gas (Ar/O2) to maintain a high HiPIMS discharge current. Small variations in the plasma density were detected between the middle part of the plasma pulse as compared to the end of the plasma pulse, when transitioning from the metal mode to the poisoned mode. It is found that the time-evolution of the electron density is rather well correlated with the discharge current waveform. On the other hand, the mean electron energy did not change significantly between the middle and the end of the plasma pulse. For the lower pulse discharge current, both the model and experimental data have shown a slight increase in the plasma density with increasing O2 mass flow rate. [ABSTRACT FROM AUTHOR]

The oxygen dynamics in a reactive Ar/O2 high power impulse magnetron sputtering discharge has been studied using a new reactive ionization region model. The aim has been to identify the dominating physical and chemical reactions in the plasma and on the surfaces of the reactor affecting the oxygen plasma chemistry. We explore the temporal evolution of the density of the ground state oxygen molecule O2(Xµ ∑-g, the singlet metastable oxygen molecules O2 (aµΔg) and O2(bµ ∑-g, the oxygen atom in the ground state O(³P), the metastable oxygen atom O(¹D), the positive ions O+2 and O+, and the negative ion O-. We furthermore investigate the reaction rates for the gain and loss of these species. The density of atomic oxygen increases significantly as we move from the metal mode to the transition mode, and finally into the compound (poisoned) mode. The main gain rate responsible for the increase is sputtering of atomic oxygen from the oxidized target. Both in the poisoned mode and in the transition mode, sputtering makes up more than 80% of the total gain rate for atomic oxygen. We also investigate the possibility of depositing stoichiometric TiO2 in the transition mode. [ABSTRACT FROM AUTHOR]

High power impulse hollow cathode sputtering is studied as a means to produce high fluxes of neutral and ionized sputtered metal species. A model is constructed for the understanding and optimization of such discharges. It relates input parameters such as the geometry of the cathode, the electric pulse form and frequency, and the feed gas flow rate and pressure, to the production, ionization, temperature and extraction of the sputtered species. Examples of processes that can be quantified by the use of the model are the internal production of sputtered metal and the degree of its ionization, the speed and efficiency of out-puffing from the hollow cathode associated with the pulses, and the gas back-flow into the hollow cathode between pulses. The use of the model is exemplified with a special case where the aim is the synthesis of nanoparticles in an expansion volume that lies outside the hollow cathode itself. The goals are here a maximum extraction efficiency, and a high degree of ionization of the sputtered metal. It is demonstrated that it is possible to reach a degree of ionization above 85%, and extraction efficiencies of 3% and 17% for the neutral and ionized sputtered components, respectively. [ABSTRACT FROM AUTHOR]