High power impulse magnetron sputtering discharge

Abstract

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique, which is easily scalable and has been successfully introduced into various industrial applications. The authors give an overview of the development of the HiPIMS discharge, and the underlying mechanisms that dictate the discharge properties. First, an introduction to the magnetron sputtering discharge and its various configurations and modifications is given. Then the development and properties of the high power pulsed power supply are discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Finally, some of the models that have been developed to gain understanding of the discharge processes are reviewed, including the phenomenological material pathway model, and the ionization region model.

Study of magnetic iron nitride thin films deposited by high power impulse magnetron sputtering

“…[1][2][3][4] As compared to dc-MS, the plasma density in HiPIMS is of the order of 10 19 m −3 , about 2 orders of magnitude larger than that in dc-MS. [2] In HiPIMS plasma, number of ionized species exceeds neutrals. [2,5] These characteristic properties of HiPIMS plasma results in improving film qualities such as film density, hardness, surface roughness, better adhesion, dense microstructure etc. Moreover, due to high metal ionization this technique has a better scope for controlling film properties deposited via reactive sputtering.…”

A phenomenological model for the description of rotating spokes in HiPIMS discharges

“…These characteristics are particularly desirable since they allow film growth control and ensure high film quality (see e.g. [2], [3] and references therein). In a HiPIMS system a very high peak power density (several kW/cm 2 ) is delivered to a conventional magnetron in a pulsed fashion: a large bias is applied to the target in short pulses of duration of a few hundred microseconds with a low duty cycle (0.5-5%).…”

Strategy for tuning the average charge state of metal ions incident at the growing film during HIPIMS deposition

“…Since electron impact is the primary ionization mechanism in HIPIMS plasmas, 12 the ionization rate is a strong function of the shape of the electron-energy distribution function g(Ee), which for a steady-state plasma has an approximately Maxwellian form,…”

“…18 Thus, the original energy distribution of sputter-ejected atoms is preserved since these species undergo few or no collisions due to strong plasma rarefaction. 12 During the later phase of HIPIMS pulses (τ > 150 µs),…”

“…Since ionization of sputter-ejected species in HIPIMS discharges is predominantly due to electron impact, 12 / is strongly affected by the plasma density in front of the target, which is in turn directly proportional to the maximum target current density jmax. 13 , and hence a low probability of sputter-ejected metal atom ionization (the mean ionization distance is inversely proportional to ne).…”