Sputtered Species Ionisation and Hysteresis Behaviour of Reactive High Power Impulse Magnetron Sputtering
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| Year of publication | 2019 |
| Type | Conference abstract |
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| Description | The hysteresis curve of reactive high power impulse magnetron sputtering (HiPIMS) discharge is generally reduced in width and shifted towards lower reactive gas supplies compared to reactive direct current magnetron sputtering (dcMS), or the hysteresis behaviour can be entirely suppressed resulting in deposition of stoichiometric compound films with a high-rate. We present evolutions of titanium atom and ion ground state number densities in HiPIMS discharge with oxygen admixture for a constant average applied power and pulse duration, while the repetition frequency is varied. The absolute ground state number densities of sputtered species are determined from optical-emission signal utilising effective branching (EBF) method [1, 2]. The sputtered species ionisation fraction increases with the degree of target poisoning. The increase is attributed to the combination of three effects: a longer residual time of sputtered particles in the magnetised plasma region; a higher maximal discharge current; higher electron temperature. Further, the hysteresis curve shape changes with the change of the repetition frequency. The higher the sputtered species ionisation fraction, the bigger the difference in the hysteresis curve shape. The hysteresis behaviour of reactive HiPIMS is modelled utilising a modified Berg model. The back-attraction of the sputtered species to the target is incorporated into the Berg model. The results from simulations match good the measured ones proving that the back-attraction of sputtered metal ions is the main effect causing the hysteresis curve reduction and shift in reactive HiPIMS compared to reactive dcMS. |
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