A poly-diagnostic study of bipolar high-power magnetron sputtering: role of electrical parameters

Abstract

Ion acceleration in a bipolar high-power impulse magnetron sputtering discharge working with Ar gas and using a Ti cathode has been investigated. The multiple discharge diagnostic approaches have been implemented, including the target and substrate current probe measurements, mass spectrometry and laser-induced fluorescence. In particular, the current waveforms were analysed in detail, showing the particularities of the current evolution during the negative (plasma) and positive voltage pulses. It is shown that the substrate current during the positive voltage pulse reveals two peaks, corresponding, as suggested, to two groups of the positive ions repulsed from the cathode by the applied positive potential. These observations correlate well with the mass spectrometry measurements as well as with the two-dimensional ion density mapping performed for several discharge conditions by laser-induced fluorescence imaging technique.

On the relationship between the plasma characteristics, the microstructure and the optical properties of reactively sputtered TiO2 thin films

“…In the HiPIMS and BPH cases, the samples were called HIP26A, BPH26A, HIP70A, and BPH70A, with the numbers corresponding to peak current values during the negative pulse, I P − = 26 A and I P − = 70 A, respectively. For clarity, this notation was utilized in the rest of the paper while further information about the definition of BPH parameters can be found elsewhere [30]. In the BPH case, the delay between the negative and the positive pulses, τ ± , was fixed at 10 µs and the positive pulse width, τ + , was fixed at 250 µs.…”

“…In the BPH case, the negative (plasma) pulse, necessary for sputtering and ionizing the metal atoms, is followed by a positive voltage pulse to accelerate the positive ions towards the substrate surface [26]. Plasma diagnostics of BPH discharges [26][27][28][29][30][31][32] as well as the analysis of film properties [33] have been reported in the literature.…”

Analysis of a second peak of electron density observed in high-power impulse magnetron sputtering plasma using a Langmuir probe

“…A bi-polar HIPIMS, 14,[30][31][32][33][34] applying a reverse positive pulse at the end of the negative pulse during the HIPIMS discharge, is gaining a great deal of interest. However, there are few reports regarding the relationship between the reverse positive voltage pulse parameter and the behavior of HIPIMS plasma.…”

Engineered ion-bombardment as a tool in thin film deposition

“…2.16. Other studies also observed a shift of the ion energies with an increase in Urev [25,117,120,124,125], though some works exhibit accelerated peaks that are a few tens of eV less than Urev [27,28,126]. The dominant thermal peak is also observed to decrease with the application of the positive pulse since most of these slow-moving ions get accelerated by the potential drop.…”

“…These factors are dependent on parameters such as the current density and on the pulsing procedure applied. Michiels et al [120] varied the peak current density of the main HiPIMS pulse, which resulted in an increase of the substrate peak current detected during the positive pulse indicating an increase in the amount of ions arriving at the substrate. The effect of changing the length of the negative pulse, , and the positive pulse, , is investigated in Paper III.…”