On Electron Heating, Deposition Rate, and Ion Recycling in the High Power Impulse Magnetron Sputtering Discharge

The magnetron sputtering discharge [1] is a plasma discharge-driven physical vapor deposition technique [2], where the film-forming species are released from a solid target, that is utilized in a range of industries. In magnetron sputtering a static magnetic field is maintained in the target vicinity, which effectively increases the residence time of electrons. The electron confinement results in a dense plasma that provides ions to the sputter process. When the magnetron sputtering discharge is driven by high power unipolar pulses of low repetition frequency, and low duty cycle, it is referred to as high power impulse magnetron sputtering (HiPIMS) discharge [3]. HiPIMS delivers high degree of ionization of the sputtered material to the deposition process, while being compatible with existing magnetron sputtering deposition systems. However, there is drawback, HiPIMS operation results in lower deposition rate than dc magnetron sputtering discharge when operated at the same average power. The ionization region model (IRM) is a time-dependent volume-averaged plasma chemical model of the ionization region (IR), located in the close vicinity of the target racetrack, defined by the confining magnetic field. It is based on the time-dependent global plasma chemistry model and was developed to study the discharge behavior during a HiPIMS pulse and the afterglow. The IRM has been applied to study various processes, such as gas rarefaction and refill processes, and the electron heating mechanisms, in an argon HiPIMS discharge with an aluminum target, and the feasibility of ionizing carbon in a discharge with a graphite target [4]. Here, we summarize some of the key findings including the electron power absorption processes, working gas rarefaction, ion composition and ion recycling.  

[1] J. T. Gudmundsson, Plasma Sources Sci. Technol. 29, 113001 (2020).
[2] J. T. Gudmundsson, A. Anders, and A. von Keudell, Plasma Sources Sci. Technol. 31, 083001 (2022).
[3] J. T. Gudmundsson, N. Brenning, D. Lundin, and U. Helmersson, J. Vac. Sci. Technol. A 30, 030801 (2012).
[4] M. A. Raadu, I. Axnäs, J. T. Gudmundsson, C. Huo, and N. Brenning, Plasma Sources Sci. Technol. 20, 065007 (2011).
[5] H. Eliasson, M. Rudolph, N. Brenning, H. Hajihoseini, M. Zanáška, M. J. Adriaans, M. A. Raadu, T. M. Minea, J. T. Gudmundsson, and D. Lundin, Plasma Sources Sci. Technol. 30, 115017 (2021).

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