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Thin film technology and surface engineering are nowadays key components for numerous innovative products like efficient windows, flat screens, sensors or hard coatings used in tool coating and automotive applications, as well as products for everyday life. In line with the demands of surface technology, coating technology is also evolving and improving. The latest major technology jump was the introduction of pulse technology in physical vapor deposition. High power impulse magnetron sputtering is the most recent development of pulse sputtering. After approximately a decade of intense academic investigation and development we observe today a transfer of this new technology towards industrial processes.

As well as several international activities the international conference on fundamentals and applications of HIPIMS continues the success story of the HIPIMS days, initiated in 2004 at Sheffield Hallam University, UK. Becoming the only international conference especially dedicated to HIPIMS the HIPIMS conference is a venue for industrial and academic exchange on the latest developments in this fast evolving new technology. As a joint undertaking of Sheffield Hallam University SHU, Network of Competence for Industrial Plasma Surface Technology INPLAS and Fraunhofer Institute for Surface Engineering and Thin Films IST the HIPIMS conference was launched in 2010 in Sheffield, UK. With 120 delegates the impact of the new conference was underlined. The growing importance of HIPIMS technology was connected with a growth by nearly 35% to 160 participants in 2011 at the second HIPIMS conference in Braunschweig, DE. The participants were made up of equal numbers from research and development (university and research institutes) and industry. Being a global conference representatives from 25 different countries from all continents attended.

The HIPIMS conference is also in joint collaboration with the COST Action MP0804 Highly Ionized Pulse Plasma Processes (www.hipp-cost.eu). COST (European Cooperation in Science and Technology) is one of the longest-running European frameworks supporting cooperation among scientists and researchers across Europe (www.cost.eu). The COST Action MP0804 HIPP processes focuses on the fundamentals and the industrial implementation of highly ionized pulse plasmas, where HIPIMS is the most prominent and most mature technology, today.

Over 50 high level contributions, divided in 37 oral and 14 poster presentations were highly appreciated by the professional audience. The message from 2011 was that HIPIMS technology has now reached industry. In the opening session of the conference representatives from different companies reported on the latest developments in industrialization. Using HIPIMS technology, the lifetime of mills using a state of the art coating can be extended by 50%. Comparable deposition rates for coating cutting inserts on the different faces are reported. The ice-free window for automotive application is one solution just becoming available by HIPIMS technology. The talks from international experts covered a range from fundamental physics, experimental investigations, theoretically modeling to several applications and made the international conference on fundamentals and applications a success story to be continued in the following years.

Arutiun Ehiasarian and Ralf Bandorf (Conference Chairmen of HIPIMS 2010 and 2011, respectively)

Organising Committee (2010 and 2011) – Affiliations Professor Dr Papken Hovsepian (Sheffield Hallam University, Nanotechnology Center for PVD Research, UK) Professor Dr Günter Bräuer (Fraunhofer Institute for Surface Engineering and Thin Films IST/ Network of Competence INPLAS, Braunschweig, DE) Professor Dr Arutiun P. Ehiasarian (Sheffield Hallam University, Materials Research Institute, UK) Dr Ralf Bandorf (Fraunhofer Institute for Surface Engineering and Thin Films IST, Braunschweig, DE)

Main Sponsor Society of Vacuum Coaters SVC Albuquerque, New Mexico, USA

Sponsors Ionbond Netherlands BV Venlo, NL Hauzer Techno Coating BV Venlo, NL Hüttinger Elektronik GmbH + Co. KG Freiburg, DE

Conference Photos

Attendees HIPIMS Conference 2010, Sheffield, UK

Attendees HIPIMS Conference 2011, Braunschweig, Germany

All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

TiAlN was sputtered reactively by HIPIMS in the target compositions Ti/Al 33/67 and 50/50 using a modified OC Oerlikon Balzers INNOVA coating equipment. The resulting film properties like deposition rate, surface roughness, hardness, Young's modulus, wear, and film stress were analyzed as function of the nitrogen gas flow, pressure, target-substrate distance, and substrate bias. Furthermore, the films were characterized by X-ray diffraction and secondary electron microscopy of the cross section and the surface appearance. The process characteristics and film properties were compared with pulsed DC sputtering under the same conditions.

In most cases HIPIMS is used to get the highest possible ionisation of the deposition particles, which is realised by pulse durations with short on- and very long off-times. These conditions are combined with a more or less pronounced decrease in deposition rate. In this work the pulse configuration has been varied. A three dimensional matrix of parameters was spanned, made of 3 on- and 3 off-times at 4 argon partial pressures. The average power was kept constant and the data achieved were additionally compared to DC-magnetron sputtering. The experiments were carried out using 50 mm diameter targets made of Ti, powered by a MELEC SPIK1000A pulser unit. The deposition rate was measured by quartz microbalance mounted in front of the target. Peak current density and target voltage were recorded and time averaged optical emission spectroscopy (t.a.OES) measurements provided information about the ionisation conditions in the plasma. The results of the data analysis provide a coherent overview of the impact of the HIPIMS parameters as well as of their complex interrelations.

Hardness, toughness, and adhesion are today among the most important characteristics of PVD (Physical Vapor Deposition) coatings for machining tools that are used for highly demanding hard, high-speed, and dry machining. The continued development and improvement of materials constantly creates new and more demanding challenges for machining tools. In particular, materials that are especially hard or difficult to machine, materials that are prone to stress hardening, and materials with low heat conductivity require coatings with high thermal and oxidation stability in addition to the properties already mentioned. With a view to these properties, the new HiPIMS technology is currently being used to develop a new generation of coatings with significantly improved properties compared to conventional coatings. They are able to process hard-to-machine materials such as nickel-based alloys and stainless austenitic steels at lower costs – with comparatively significantly improved machining parameters and considerably less tool wear.

AlTiN and CrN coatings were deposited in hybrid DOMINO platforms by magnetron sputtering (DC-MS, DC-MS+HCP-MS, HCP-MS) and vacuum arc evaporation. The ion cleaning was done by the AEGD process. The coating rates and the energy efficiency of both deposition processes were compared. The roughness effects of the different coating types were discussed. Preliminary results of the change of pulse characteristics during simultaneously running of HCP-MS plus vacuum arc evaporation are shown.

Highly ionized pulse plasma processes (HIPP processes), like high power impulse magnetron sputtering (HIPIMS) also known as high power pulse magnetron sputtering (HPPMS), modulated pulse power sputtering (MPP), as well as further modifications involving increased ionization in sputtering have been investigated and matured within the last decade. On European level a concerted action focusing the efforts and bringing together the leading experts was set up and is actually promoting the transition of HIPP processes to industry. Besides the well know approaches of HIPIMS/HPPMS and MPP further modifications for ionized PVD are under development. This paper focuses on HIPP processes and new technological approaches besides the well-known "big players". New approaches combining technologies like hollow cathodes in different modifications, coils for inductive coupling, arc sources for "gasless sputtering" or a modified process for constant-current HIPIMS will be presented.

Sputtering magnetic materials with magnetron based systems has the disadvantage of field quenching and variation of alloy composition with target erosion. The advantage of eliminating magnetic fields in the chamber is that this enables sputtered particles to move along the electric field more uniformly. Inductively coupled impulse sputtering (ICIS) is a form of high power impulse magnetron sputtering (HIPIMS) without a magnetic field where a high density plasma is produced by a high power radio frequency (RF) coil in order to sputter the target and ionise the metal vapour. In this emerging technology, the effects of power and pressure on the ionisation and deposition process are not known. The setup comprises of a 13.56 MHz pulsed RF coil pulsed with a duty cycle of 25 %. A pulsed DC voltage of 1900 V was applied to the cathode to attract Argon ions and initiate sputtering. Optical emission spectra (OES) for Cu and Ti neutrals and ions at constant pressure show a linear intensity increase for peak RF powers of 500 W – 3400 W and a steep drop of intensity for a power of 4500 W. Argon neutrals show a linear increase for powers of 500 W – 2300 W and a saturation of intensity between 2300 W – 4500 W. The influence of pressure on the process was studied at a constant peak RF power of 2300 W. With increasing pressure the ionisation degree increased. The microstructure of the coatings shows globular growth at 2.95×10⁻² mbar and large-grain columnar growth at 1.2×10⁻¹ mbar. Bottom coverage of unbiased vias with a width of 0.360 μm and aspect ratio of 2.5:1 increased from 15 % to 20 % for this pressure range. The current work has shown that the concept of combining a RF powered coil with a magnet-free high voltage pulsed DC powered cathode is feasible and produces very stable plasma. The experiments have shown a significant influence of power and pressure on the plasma and coating microstructure.

In this paper specific advantages and disadvantages of different pulse magnetron sputtering processes (unipolar, bipolar and HIPIMS) as well as current and potential fields of application will be discussed. On the examples of ZrN, Ti and TiO2 the typical effects and their influence on film properties occurring during the transition from classical medium frequency pulse magnetron sputtering to high energy pulse sputtering will be described. The discharge current density was varied between 0.2 and 3.5 A/cm². Aspects of energy feed-in and reactive process control in the transition mode will be considered. Furthermore the influence of rising ionisation on the occurrence of crystalline phases and on mechanical, optical and photocatalytic properties of the layers will be presented. The paper concludes with a placement of the processes related to other PVD-processes that is based on further own experimental results and evaluation of dependencies as well as considering published results of other groups regarding pulse magnetron sputter processes of high power density for the deposition of hard coatings and TCO.

In reactive High Power Impulse Magnetron Sputtering (HIPIMS) of oxides, target effects such as reduced surface oxidation during pulse off time, increased implantation of reactive gas due to the higher discharge voltage as compared to normal DC sputtering, and enhanced target cleaning during on time are considered to be responsible for the differences compared to reactive DC sputtering. These effects are assumed to cause changes in the target oxide coverage and hence lead to the hysteresis shifts observed in experimental studies. In this contribution, the target processes are simulated using the binary collision approximation code TRIDYN. Using an Al target sputtered in Ar+O₂ mixture as a model system, a range of pulse configurations is simulated for different oxygen partial pressures. The results indicate that the target effects alone are not sufficient to explain the observed shift of hysteresis and its frequency dependence.

Highly ionized pulse plasma processes (HIPP processes) like High Power Impulse Magnetron Sputtering HIPIMS and Modulated Pulse Power MPP have matured in recent years. Current research focuses on the development for industrial processes. HIPP processes offer a tool for tailoring the film properties and to improve hardness, density, refractive index, and further properties beyond state of the art. Alumina coatings are used besides application in cutting tools as insulator for electric and sensor applications. This paper focuses on the process development of an industrial process for deposition of alumina with improved properties regarding the use as insulator. Concerning productivity a high rate deposition process is required for economic production. Therefore, the deposition rate must be increased or the film properties improved in a way that thinner films exceed reference films prepared with state of the art technology. MPP in comparison to a mid-frequency (MF-) process was investigated and the resulting rates are reported. The films were prepared without feedback control in the transition regime close to the threshold of the oxide mode. Regarding the insulating properties the films were characterized by their critical leakage field strength. MPP films with less than 1 μm thickness showed a critical leakage field strength up to 2.9 V/nm. The SEM cross sections of the prepared films showed a dense glassy structure for all the HIPP films.

In this paper a new technique is proposed for precise doping control of ZnO:Al thin films deposited in reactive High Power Impulse Magnetron Sputtering (HIPIMS). An auxiliary aluminum electrode was added to a reactive Ar/O₂ pulsed magnetron with planar Zn target in order to obtain a controlled doping of ZnO films. Al neutral density in gas phase has been controlled by the discharge current and the biasing voltage on the auxiliary electrode (which influence the ion bombardment of the electrode) and measured by laser resonant absorption spectroscopy. The fraction of Al dopant in the deposited films was estimated by X-ray Photoelectron Spectroscopy (XPS) measurements. The goal of this work was to correlate Al density measured in the gas phase with Al concentration in the deposited films. It was also investigated the effect of the aluminum concentration on the structural, electrical and optical properties of ZnO:Al thin films deposited by HIPIMS. The internal microstructure and chemical composition of the deposited films was examined by X-ray difractometry (XRD) and X-ray Photoelectron Spectroscopy (XPS). The optical properties of the deposited films were studied by UV/VIS and photoluminescence spectroscopy.

2.5 μm thick TiAlCN/VCN coatings were deposited by reactive HIPIMS process. XTEM showed gradual evolution of the structure of the coating with thickness. The initial structure is nanoscale multilayer with sharp interlayer interfaces. This transforms to nanocomposite of TiAlCN and VCN nanocrystalline grains surrounded by C-rich tissue phase and finally changes to an amorphous carbon rich Me-C phase. Energy-resolved mass spectrometry revealed that HIPIMS plasma is a factor of 10 richer in C¹⁺ ions, and therefore more reactive, as compared to the plasma generated by standard magnetron discharge at the same conditions. The peculiar structure evolution in HIPIMS is is attributed to target poisoning effect.

We report for the first time on instabilities of High Power Impulse Magnetron Sputtering Plasmas (HIPIMS) which are likely to be of the generalised drift wave type. They are characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron and causes periodic shifts in floating potential. The azimuthal mode number m depends on plasma current, plasma density, and gas pressure. The structures rotate in × direction at velocities of ~10 kms⁻¹ and frequencies up to 200 kHz. Collisions with residual gas atoms slow the rotating wave down, whereas the elevated plasma density accelerates it. The instabilities result in intermittent modulated particle fluxes with significant magnitude transported away from the cathode.

Laser-induced fluorescence (LIF) combined with resonant optical absorption spectroscopy (ROAS) were utilized for characterization of the Ar-Ti high-power impulse sputtering (HIPIMS) discharge at working pressures of 5 and 20 mTorr. The LIF measurements were performed during the plasma off-time. It was shown that the time-behavior of the measured densities depends strongly on the working pressure in the reactor as well as on the distance from the magnetron target. ROAS measurements indicates that the absolute ground state level density of Ti can reach ≈ 10¹¹ cm⁻³ (at 20 mTorr, 10 μs pulse, and 12 kW of applied power per pulse). Generally, the obtained results indicate highly non-uniform spatial and temporal behavior of the sputtered species such as Ti and Ti⁺, which correlate with the results previously obtained in the other magnetron discharges.