First measurements of the temporal evolution of the plasma density in HiPIMS discharges using THz time domain spectroscopy

Abstract

In this paper the novel technique of THz time domain spectroscopy has been applied to obtain time-resolved measurements of the plasma density in the active zone of a HiPIMS discharge with a titanium target. The obtained peak values are in the range of 10 12 -10 13 cm −3 for discharge current densities of 1 to 4 A/cm 2 at 0.5 and 2 Pa argon pressure. The measured densities show good correlation with the discharge current and voltage and the intensity of various atomic and ionic lines. The well known phases of the discharge have been identified and related to the variation of the electron density. The measurement results show that the plasma density remains nearly constant during the runaway/self-sputtering phase. Based on that it is conjectured that singly charged titanium ions are the dominant ion species during this phase.

Corrigendum: Evidence of ion energy distribution shift in HiPIMS plasmas with positive pulse (2019 Plasma Sources Sci. Technol. 28 01LT03)

“…F Avino https:/ /orcid.org/0000-0002-6206-0960 The large fraction of ionized sputtered atoms in plasmas obtained with High Power Impulse Magnetron Sputtering (HiPIMS) is making this technique very attractive for a constantly increasing number of fields [1][2][3][4][5][6]. The scientific community is devoting a significant effort to investigate and unveil the physical mechanisms of HiPIMS plasmas [7][8][9][10][11], as well as to explore the advantages with respect to well known sputtering techniques such as Direct Current Magnetron Sputtering (DCMS) [12,13]. Very recently, the effects of a positive voltage pulse (PP) applied to the target after the main negative pulse in the HiPIMS regime have started to be explored [14,15].…”

On the role of ion potential energy in low energy HiPIMS deposition: An atomistic simulation

“…In HiPIMS the overheating issue of the cathode target is resolved by applying unipolar high power pulses with a low duty cycle and at low repetition frequency, while maintaining similar time averaged power as for dcMS [1,2]. Therefore a peak electron density that is 2 -3 orders of magnitude higher than in dcMS, is achieved in the vicinity of the cathode target [5,6,7]. Due to the high electron density the ionization mean free path of the sputtered species becomes shorter and the ionization probability increases and a significant fraction of the ions reaching the substrate are ions of the film-forming species.…”

On the role of ion potential energy in low energy HiPIMS deposition: An atomistic simulation

“…In HiPIMS the overheating issue of the target is resolved by applying unipolar high power pulses with a low duty cycle [1,2]. Therefore a peak electron density 2 -3 orders of magnitude higher than in dcMS, is achieved in the vicinity of the cathode target [5,6,7]. Consequently, the ionization mean free path becomes shorter and the ionization probability of sputtered atoms by collisions with energetic electrons increases and a significant fraction of the ions reaching the substrate are ions of the film-forming species.…”