High-power impulse magnetron sputtering (HiPIMS) is a promising sputtering-based ionized physical vapor deposition technique and is already making its way to industrial applications. The major difference between HiPIMS and conventional magnetron sputtering processes is the mode of operation. In HiPIMS the power is applied to the magnetron (target) in unipolar pulses at a low duty factor (andlt;10%) and low frequency (andlt;10 kHz) leading to peak target power densities of the order of several kilowatts per square centimeter while keeping the average target power density low enough to avoid magnetron overheating and target melting. These conditions result in the generation of a highly dense plasma discharge, where a large fraction of the sputtered material is ionized and thereby providing new and added means for the synthesis of tailor-made thin films. In this review, the features distinguishing HiPIMS from other deposition methods will be addressed in detail along with how they influence the deposition conditions, such as the plasma parameters and the sputtered material, as well as the resulting thin film properties, such as microstructure, phase formation, and chemical composition. General trends will be established in conjunction to industrially relevant material systems to present this emerging technology to the interested reader.Funding Agencies|Swedish Research Council (VR)|623-2009-7348
The effect of the high pulse current and the duty cycle on the deposition rate in high power pulsed magnetron sputtering (HPPMS) is investigated. Using a Cr target and the same average target current, deposition rates are compared to dc magnetron sputtering (dcMS) rates. It is found that for a peak target current density ITpd of up to 570mAcm−2, HPPMS and dcMS deposition rates are equal. For ITpd>570mAcm−2, optical emission spectroscopy shows a pronounced increase of the Cr+∕Cr0 signal ratio. In addition, a loss of deposition rate, which is attributed to self-sputtering, is observed.
In this work TiOx (x > 1.8) films are grown reactively from a ceramic TiO1.8 target employing high power pulsed magnetron sputtering (HPPMS) at a constant average target current. The effect of the pulse on/off time configuration on the target and the discharge characteristics as well as on the film properties is investigated. The target voltage (VT) increases from 480 to 650 V and the peak target current (ITp) increases from 2 to 40 A when the pulse off-time is increased from 200 to 2450 µs, while the on-time is kept constant at 50 µs. This is accompanied by an increase in the number of Ti atoms sputtered from the target, as manifested by time-resolved optical emission spectroscopy (OES) measurements. OES also manifests an increase in the ionization of the sputtered Ti atoms with increasing ITp. The above changes in the target and discharge characteristics affect the deposition rate so that the latter increases with increasing ITp up to a value of 14 A, above which the deposition rate drops. In all the cases the deposition rates are up to ∼40% higher compared to the rates achieved for films grown by dc magnetron sputtering (dcMS) which are also studied for reference. The increase in ITp from 2 to 40 A also affects the films' properties. It is shown that a drop in the surface roughness from 1.1 to 0.5 nm takes place. These values are lower than the surface roughness of films grown by dcMS (1.35 nm). Moreover, films grown by HPPMS are found to have higher densities (up to 3.83 g cm−3) and higher refractive indices (up to 2.48) in comparison to the films grown by dcMS (3.71 g cm−3 and 2.38, respectively).
A strategy that facilitates a substantial increase of carbon ionization in magnetron sputtering discharges is presented in this work. The strategy is based on increasing the electron temperature in a high power impulse magnetron sputtering discharge by using Ne as the sputtering gas. This allows for the generation of an energetic C + ion population and a substantial increase in the C + ion flux as compared to a conventional Ar-HiPIMS process. A direct consequence of the ionization enhancement is demonstrated by an increase in the mass density of the grown films up to 2.8 g/cm 3 ; the density values achieved are substantially higher than those obtained from conventional magnetron sputtering methods.
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