Pulse length selection for optimizing the accelerated ion flux fraction of a bipolar HiPIMS discharge

Abstract

The effect on the energy distributions of metal and gas ions in a bipolar high-power impulse magnetron sputtering (HiPIMS) discharge as the negative and positive pulse lengths are altered are reported. The results presented demonstrate that the selection of the pulse lengths in a HiPIMS discharge is important in optimizing the amount of accelerated ions. A short enough negative pulse is needed so that ions do not escape to the substrate before being accelerated by the positive pulse that follows the main negative HiPIMS pulse. The length of the positive pulse should also be long enough to accelerate the majority of the ions, but a too long positive pulse depletes the process chamber of electrons so much that it makes it difficult to initiate the next HiPIMS pulse. When pulse lengths of negative and positive pulses are properly selected, the fraction of ions, both metal and gas, accelerated by the positive pulse voltage is close to 100 %.

Effect of Pulsing Configuration and Magnetic Balance Degree on Mechanical Properties of CrN Coatings Deposited by Bipolar-HiPIMS onto Floating Substrate

“…The apparently contradictory results, in terms of the effect of positive target voltage on the film's properties, reported in the literature, could be due to some different deposition conditions and/or deposition systems used (e.g., different pulsing and/or magnetic field configurations). The influence of pulsing configuration on the fraction of accelerated ions towards a grounded mass spectrometer was recently reported by Viloan et al [22]. According to their work, the fraction of ions, accelerated to energies corresponding to the full positive target potential, is close to 100% when the duration of the negative and positive pulses is properly selected.…”

“…In order to minimize the substrate's influence on the indentation data, the indentation depth was kept below 40 nm (10% of the films' thickness). Previous studies have shown that the fraction of accelerated ions during bipolar-HiPIMS strongly depends on the pulsing configuration [22]. During bipolar-HiPIMS, the fraction of accelerated ions can be accurately controlled by keeping constant the duration of negative pulse and by varying the duration of the positive pulse.…”

“…Compared to the standard HiPIMS configuration, the bipolar-HiPIMS yields more compact, denser, smoother, harder, and more adherent coatings due to a much higher energy and flux levels of the film-forming species. Furthermore, the bipolar-HiPIMS has the advantage to easily control the fraction of the accelerated ions [19,22], making it possible to finely tune the properties of the coatings deposited onto grounded substrates [19,20]. One of our most recent works shows that bipolar-HiPIMS enables an energy-enhanced deposition process of high-quality (high hardness, low coefficient of friction, good wear resistance, good adhesion to the substrate, very low surface roughness, and defect free) hydrogen-free DLC thin films on electrically insulated substrates, without using any substrate bias voltage, adhesion interfacial layer or substrate pre-treatment [23].…”

Selective Metal Ion Irradiation Using Bipolar HIPIMS: A New Route to Tailor Film Nanostructure and the Resulting Mechanical Properties

“…The selection of pulsing parameters (in both the positive and negative phases) was based on the experiments published in [11], where it is demonstrated that the application of a short negative pulse followed by a larger positive pulse maximizes the fraction of positive ions accelerated during the positive phase. As the negative pulse time is longer than the time-of-flight of the metal ions, these ions reach the substrate without being accelerated.…”

Engineered ion-bombardment as a tool in thin film deposition

“…The effect of changing the length of the negative pulse, , and the positive pulse, , is investigated in Paper III. It was observed that the accelerated ion flux fraction due to the application of Urev increases with a decrease in and a sufficient increase in [121]. A long allows more ions generated during the HiPIMS pulse to arrive at the substrate without being affected by Urev.…”