Pulsed dc Magnetron Discharges and their Utilization in Plasma Surface Engineering

Abstract

Fundamental aspects of magnetron operation in two types of practically interesting discharges, i.e. in highpower unipolar pulsed dc magnetron discharges for ionized high-rate sputtering and in asymmetric bipolar pulsed dc magnetron discharges for reactive sputtering, were investigated on the basis of time-resolved plasma diagnostics. We present the results obtained using time-resolved optical emission spectroscopy and time-and energy-resolved mass spectroscopy in high-power unipolar pulsed dc magnetron discharges at a repetition frequency of 1 kHz, an argon pressure of 1 Pa and an average target power loading in a pulse up to 500 W/cm 2 . The main aim was to study complex ionization mechanisms of sputtered Cu atoms and working gas (Ar) atoms, and to characterize energy distributions of Cu + and Ar + ions and their fractions in ion fluxes to a substrate during pulses. Some results achieved with a grooved target at the frequencies up to 50 kHz are discussed. We report also on the results obtained using energy-resolved mass spectroscopy and time-resolved Langmuir probe measurements in asymmetric bipolar pulsed dc magnetron discharges at repetition frequencies of 100 kHz and 350 kHz, an argon pressure of 0.53 Pa and a mean discharge power of 300 W. They explain a complex correlation between the pulsed plasma dynamics and the enhanced ion bombardment of growing films in these discharges. Some new development trends in the field of the dual pulsed dc magnetron sputtering are outlined.

A review comparing cathodic arcs and high power impulse magnetron sputtering (HiPIMS)

“…While not the first publication in this field, it can be considered seminal as the concept of ionization of sputtered target atoms was clearly demonstrated with a conventional planar magnetron operated at common average power and without any assisting discharge. High metal ion fluxes and a high degree of ionization obtained this way were soon confirmed by other groups [82][83][84][85][86][87].…”

High power impulse magnetron sputtering discharge

“…Since the target current is much higher for an HiPIMS discharge than for a dcMS discharge the rarefaction effect is expected to be much more pronounced. This phenomena has been demonstrated experimentally for an HiPIMS discharge by Alami et al 199 and Vlček et al 173,246 Using optical emission spectrometry Vlček et al 173,246 see almost an order of magnitude decrease in the density of atomic argon but slightly less dramatic decrease in the density of argon ions roughly 50-70 ls into a 200 ls long pulse while sputtering Cu target. Liebig et al 203 apply 2D OES to explore the spatial and temporal behavior of the argon working gas and also observe gas rarefaction.…”

Evolution of the plasma composition of a high power impulse magnetron sputtering system studied with a time-of-flight spectrometer

“…The evolution of metal species (atoms, ions) in the plasma has been demonstrated using optical emission spectroscopy 1 (OES), optical absorption spectroscopy 4 (OAS) and particle spectrometry 3,20 using so-called plasma analyzers, which are combined energy and mass spectrometers. Such methods are powerful but have limitations, for example, the optical intensity used by OES is a convolution of the density of radiating particles and their excitation conditions, and interpreting the signal height of different species in plasma analyzers is based on certain assumptions for particle transmission and detector efficiency.…”