High power pulsed magnetron sputtering (HPPMS) is an emerging technology that has gained substantial interest among academics and industrials alike. HPPMS, also known as HIPIMS (high power impulse ...

High power pulsed magnetron sputtering: A review on scientific and engineering state of the art

Cutting tools with hard coatings have been successfully employed in the industry for almost 50 years. Nowadays, 85% of all cemented carbide tools are coated. There is an increasing demand for ever more efficient tools driven by the use of new workpiece materials as well as the demand for increased productivity of manufacturing processes. A historical review of the development of CVD and PVD processes shows a continuous improvement of successful coating materials through adjustments of the chemical composition and the coating architecture. Especially nanostructured PVD coatings managed to establish themselves on the market surprisingly quickly. Cutting tools are an excellent example for how the development of coated products is traced methodologically by means of a holistic view over the application. The demand for innovative tooling concepts will continue to exist in the future, as will the high potential for this aim to be achieved through high-performance coatings on improved cutting materials with adjusted tool design.

High-performance coatings for cutting tools

High Power Impulse Magnetron Sputtering (HiPIMS) is a coating technology that combines magnetron sputtering with pulsed power concepts. By applying power in pulses of high amplitude and a relatively low duty cycle, large fractions of sputtered atoms and near-target gases are ionized. In contrast to conventional magnetron sputtering, HiPIMS is characterized by self-sputtering or repeated gas recycling for high and low sputter yield materials, respectively, and both for most intermediate materials. The dense plasma in front of the target has the dual function of sustaining the discharge and providing plasma-assistance to film growth, affecting the microstructure of growing films. Many technologically interesting thin films are compound films, which are composed of one or more metals and a reactive gas, most often oxygen or nitrogen. When reactive gas is added, non-trivial consequences arise for the system because the target may become “poisoned,” i.e., a compound layer forms on the target surface affecting the sputtering yield and the yield of secondary electron emission and thereby all other parameters. It is emphasized that the target state depends not only on the reactive gas' partial pressure (balanced via gas flow and pumping) but also on the ion flux to the target, which can be controlled by pulse parameters. This is a critical technological opportunity for reactive HiPIMS (R-HiPIMS). The scope of this tutorial is focused on plasma processes and mechanisms of operation and only briefly touches upon film properties. It introduces R-HiPIMS in a systematic, step-by-step approach by covering sputtering, magnetron sputtering, reactive magnetron sputtering, pulsed reactive magnetron sputtering, HiPIMS, and finally R-HiPIMS. The tutorial is concluded by considering variations of R-HiPIMS known as modulated pulsed power magnetron sputtering and deep-oscillation magnetron sputtering and combinations of R-HiPIMS with superimposed dc magnetron sputtering.

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Tutorial: Reactive high power impulse magnetron sputtering (R-HiPIMS)

A semiconductor substrate processing system includes a chamber that includes a processing region and a substrate support. The system includes a top plate assembly disposed within the chamber above the substrate support. The top plate assembly includes first and second sets of plasma microchambers each formed into the lower surface of the top plate assembly. A first network of gas supply channels are formed through the top plate assembly to flow a first process gas to the first set of plasma microchambers to be transformed into a first plasma. A set of exhaust channels are formed through the top plate assembly. The second set of plasma microchambers are formed inside the set of exhaust channels. A second network of gas supply channels are formed through the top plate assembly to flow a second process gas to the second set of plasma microchambers to be transformed into a second plasma.

Semiconductor Processing System Having Multiple Decoupled Plasma Sources

The nitrides of most of the group IVb-Vb-VIb transition metals (TiN, ZrN, HfN, VN, NbN, TaN, MoN, WN) constitute the unique category of conductive ceramics. Having substantial electronic conductivity, exceptionally high melting points and covering a wide range of work function values, they were considered for a variety of electronic applications, which include diffusion barriers in metallizations of integrated circuits, Ohmic contacts on compound semiconductors, and thin film resistors, since early eighties. Among them, TiN and ZrN are recently emerging as significant candidates for plasmonic applications. So the possible plasmonic activity of the rest of transition metal nitrides (TMN) emerges as an important open question. In this work, we exhaustively review the experimental and computational (mostly ab initio) works in the literature dealing with the optical properties and electronic structure of TMN spanning over three decades of time and employing all the available growth techniques. We critically evaluate the optical properties of all TMN and we model their predicted plasmonic response. Hence, we provide a solid understanding of the intrinsic (e.g. the valence electron configuration of the constituent metal) and extrinsic (e.g. point defects and microstructure) factors that dictate the plasmonic performance. Based on the reported optical spectra, we evaluate the quality factors for surface plasmon polariton and localized surface plasmon for various TMN and critically compare them to each other. We demonstrate that, indeed TiN and ZrN along with HfN are the most well-performing plasmonic materials in the visible range, while VN and NbN may be viable alternatives for plasmonic devices in the blue, violet and near UV ranges, albeit in expense of increased electronic loss. Furthermore, we consider the alloyed ternary TMN and by critical evaluation and comparison of the reported experimental and computational works, we identify the emerging optimal tunable plasmonic conductors among the immense number of alloying combinations.

Conductive nitrides: Growth principles, optical and electronic properties, and their perspectives in photonics and plasmonics

Alumina coatings were reactively deposited on steel substrates by pulsed magnetron sputtering at substrate temperatures (Ts) of 330–760 °C. Investigations into the structure and morphology of the layers were made via XRD and SEM techniques, respectively. As to the layer properties, the hardness was determined by nanoindentation, and the residual stresses were derived from the bending of the coated substrates. At substrate temperatures of less than 330 °C the Al2O3 layers are amorphous to X-rays, whereas γ-Al2O3 is detected at a substrate temperature Ts ≈ 480 °C. A further increase in substrate temperature to 560 °C results in the formation of a pronounced texture of γ-Al2O3. A phase mixture of textured γ- and α-Al2O3 is deposited at Ts ≈ 690 °C. At Ts ≈ 760 °C the layer consists completely of α-Al2O3 with crystallite sizes of about 1 μm. The occurrence of the crystalline γ phase at 480 °C is linked with a pronounced increase in hardness from 10 to 19 GPa. The layer hardness of pure α-Al2O3 amounts to 22 GPa and corresponds to the hardness of the bulk material.

Effect of the substrate temperature on the structure and properties of Al2O3 layers reactively deposited by pulsed magnetron sputtering

With the introduction of the bipolar pulsed dual magnetron sputtering (BP-DMS) technique, a wide range of opportunities has opened up for the deposition of insulating layers such as Al 2 O 3 as well as of conductive compound layers such as Ti x Al 1− x N. In BP-DMS, two magnetrons in a pair alternately act as a cathode and an anode; during the cathode phase, the target is sputter-cleaned, hence ensuring a metallic surface during the anode phase and a stable long-term operation. At high-enough frequencies (25–50 kHz), possible electron charging of insulating layers will be suppressed and the otherwise troublesome phenomenon of arcing will be limited. The BP-DMS method has made it possible to deposit hard (>2000 HV ) nanocrystalline γ-Al 2 O 3 textured in the [440] direction at substrate temperatures as low as 700 °C, which is a much lower temperature than the conventional chemical vapor deposition (CVD) temperatures (1000–1050 °C) for the deposition of the Al 2 O 3 polymorphs α and κ. In this paper, a study of the process, in terms of recording the process characteristic data and evaluating the influence of magnetic field, has been done. For a set of parameters, cemented carbide cutting inserts have been coated and tested. Inserts with a double layer of γ-Al 2 O 3 and TiAlN or TiN have been evaluated in cutting operations such as turning, threading, and end-milling, often with machining conditions (cutting data) more suitable for physical vapor deposition (PVD)- than CVD-coated tools. Some results are presented in this paper. It has been shown that the addition of a 2-μm-thick γ-Al 2 O 3 layer decreases the wear rate. The γ-Al 2 O 3 /TiAlN (TiN)-coated inserts exhibit tool lives longer than the single-coated inserts especially at higher cutting speeds.

PVD-Al2O3-coated cemented carbide cutting tools

Crystalline Al 2 O 3 layers with hardness values up to those of pure corundum (22 GPa) were produced by reactive pulsed magnetron sputtering of aluminum. Used for the purpose was a dual magnetron system with a bipolar pulsed square-wave power supply in the MF range. Via a variation of pulse parameters it was possible to exert an influence on the plasma density and therefore on the layer properties obtained. It is shown that the pulsed power supply substantially reduces the temperature needed for the deposition of crystalline alumina, i.e., especially of α-Al 2 O 3 . Irrespective of the chosen working point, the coating process can be performed in a stable long-term manner without the occurrence of hysteresis effects. Both plant and process are upscaled to the conditions of industrial application with respect to productivity and three-dimensional substrates. In addition, an adhesion-improving sublayer of another material can be applied; e.g., (Ti,Al)N, etc. Hence, facility is provided to coat not only hard metal components (e.g., cemented carbide inserts) with a hard layer of alumina but also temperature-sensitive materials such as tool steel.

The deposition of hard crystalline Al2O3 layers by means of bipolar pulsed magnetron sputtering

In this work, the composition and the microstructure of two-phase hard coatings have been varied by reactive pulsed co-sputtering of two target materials to produce nanocomposite structures. Two material systems have beenstudied for their potential of improved properties induced by phase segregation: the nitride system Ti-Al-N and the oxide system Al-Zr-O. Both systems combine well-established hard coating materials and hold the potential for nanocomposite formation. The nitride system is known to exhibit enhanced properties when the composition Ti 1 - x Al x N is in the range x=0.5...0.7. Pulse magnetron sputtering allows tuning of the composition in this range by varying the pulse durations of the two materials sputtered. nc-(Ti,Al)N/nc-AlN films with hardness up to 38 GPa have been produced by optimising composition and microstructure. In the oxide system, nc-Al 2 O 3 /ZrO 2 coatings with γ-phase Al 2 O 3 of hardness about 30 GPa are obtained only when the ZrO 2 content is below 8 at.%. With increasing zirconia content the films become amorphous and exhibit hardness of 10 GPa. At low alumina content, crystalline zirconia is stabilized in its tetragonal phase exhibiting hardness of 17 GPa.

Nanocomposite oxide and nitride hard coatings produced by pulse magnetron sputtering

The present invention describes a coated cutting tool for metal machining. The coating is formed by one or more layers of a refractory compound of which at least one layer of fine-grained, crystalline γ-phase alumina, Al 2 O 3 , with a grain size of less than 0.1 μm. The Al 2 O 3 layer is deposited with a bipolar pulsed DMS technique (Dual Magnetron Sputtering) at substrate temperatures in the range 450° C. to 700° C., preferably 550° C. to 650° C., depending on the particular material of the tool body to be coated. Identification of the γ-phase alumina is made by X-ray diffraction. Reflexes from the ( 400 ) and ( 440 ) planes occurring at the 2θ-angles 45.8 and 66.8 degrees when using Cu κα radiation identify the γ-phase Al 2 O 3 . The alumina layer is also very strongly textured in the [( 440 )]-direction. The Al 2 O 3 layer is virtually free of cracks and halogen impurities. Furthermore, the Al 2 O 3 layer gives the cutting edge of the tool an extremely smooth surface finish.

Fred Fietzke

Papers

Effect of the substrate temperature on the structure and properties of Al2O3 layers reactively deposited by pulsed magnetron sputtering

PVD-Al2O3-coated cemented carbide cutting tools

The deposition of hard crystalline Al2O3 layers by means of bipolar pulsed magnetron sputtering

Nanocomposite oxide and nitride hard coatings produced by pulse magnetron sputtering

PVD Al2O3 coated cutting tool