ICMCTF2015 Session G2-2: Advances in Deposition Eqiuipment and Processes

CVD is an industrially well-established technology for hard coatings. For tooling applications CVD systems have been introduced into industrial production for almost 50 years. And from the very beginning up to now the CVD technique was under a big evolution with respect to productivity, accuracy and versatility. While in the last decades TiN, TiC, MT-TiCN and Al₂O₃ coatings were the main focus, the tool manufacturing industries have generated a growing demand for novel material applicable for large scale production.

The progress achieved in the CVD technology leaded to higher reliability and precision allowing narrow production tolerances for the tooling industry. Moreover it opened doors to more versatility. For instance it allows using the well-defined conditions needed to coat for instance highly textured (0001) Al₂O₃, AlTiN or nano composites.

Beside these the most important requirement on today’s CVD equipment`s is: to offer the users individual extensions like additional precursors or components to give them the opportunity for developing new coatings.

This presentation describes a new design of low pressure plasma system aimed at high volume, inline manufacturing environments. The novel approach combines a linear plasma source with a substrate platform that translates through the plasma zone. The linear source is based on a parallel plate diode system powered by dual frequency RF and kHz energy. Generated plasma passes through a slit-style aperture, creating a confined yet isotropic Plasma Curtain. Excellent plasma density uniformity is obtained along the linear axis of the source, and substrates are translated under the plasma curtain to achieve uniformity along its perpendicular axis.

The wide format design overcomes many of the existing limitations of low pressure plasma such as staging time and uniformity of process. Also, scale-up beyond a meter in source length has demonstrated no loss in uniformity along its axis. The concept also tackles the limitations of atmospheric plasma, requiring low consumption of reactant gases (and therefore minimal gas abatement), and full process parameter control and monitoring. In addition there are no issues of plasma density attenuation as a function of distance from the source.

Gas plasma applications such as cleaning/etching, coating by PECVD and enhancing bondability by surface energy activation are ideal applications for this system. Process speeds are measured in nm/m/min. For SiO₂ deposition by PECVD, rates of 400nm/m/min, with a uniformity of <3.5% can readily be achieved. PTFE-like coatings can be deposited at the same 400nm/m/min rate with 5% uniformity. Thermal SiO₂ etch rates of at 500nm/m/min with a uniformity of 8.5% have also been demonstrated.

Pulsed laser deposition (PLD) has been under active development for several decades but has still only limited applications in industrial thin film processing. Its technical merits like stoichiometry control and good flexibility for processing wide range of materials are well known and accepted. The traditional PLD techniques, relying mainly on low repetition rate lasers, point sources and nanosecond pulse length may not offer possibilities for large-scale or large-area coating with the high throughput, reliability, homogeneity, and reproducibility required in industrial processes. Furthermore, thin film quality, particle formation and freedom to use e.g. heat sensitive substrate materials may limit their use. Currently, first industrial applications for PLD are in e.g. high temperature superconductors (YBCO) and PZT.

Recently, thin-film coating technology has been developed which is based on ultra-short pulsed laser deposition (USPLD) using high repetition rate lasers. Technology is relying on high power lasers with optical path containing polygon scanners and telecentric lens. This approach creates line source allowing feasibility for scale-up to large surface area coating with high productivity and uniformity.

This paper presents thin-film properties of selected metallic and ceramic materials produced by ultrashort pulse durations (0,65-10 ps), ultra fast repetition rates (up to 40 MHz) and scanning widths up to 120 mm using 200W lasers. Results of technological benefits including low thermal budget, excellent adhesion, stoichiometry control from target to thin film and control of porosity are presented. Influence of laser pulse energy and intensity distribution, fluence, process gas pressure and substrate temperature are investigated with selected metallic and ceramic materials like Cu, aluminium oxide and titanium dioxide.

Industrial feasibility is demonstrated by high productivity and good uniformity using industrial scale production unit. Using high power laser and precise process control USPLD technology shows scalability and industrial potential with flexibility to adjust for batch, sheet-to-sheet or roll-to-roll processing in full-scale processing systems. Applications for this technology where the intrinsic benefits can be utilized range from high temperature superconductors and PZT to metallizing, Li batteries, wear resistant and hard coatings, MEMS, sensors and photovoltaics.

Atomic Layer Deposition (ALD) has been slowly gaining acceptance in the field of thin film deposition. There are many benefits of ALD, however, in terms of deposition rates and management of reactive gas species in complex 3D structures there is still a long road ahead.

A particular area of growth has been Plasma Enhanced ALD (PEALD). PEALD has been introduced in order to lower the temperature requirements for the ALD process and also in order to control the properties of the ALD deposited film. The industrialization of such process presents a number of challenges. In PEALD, it is of interest to control the nature and degree of interaction of such plasmas with the surface chemistry. Plasma sources which can control the energy of the ion beam are of special interest. From the point of view of industrialization, Linear Ion Sources (LIS) could help move ALD processes into mass production. LIS’s have been slowly pushing their way through into vacuum coating technology market for over 15 years. Only last year a small circular ion source, which can replicate the functional properties of large LIS’s was introduced. This development enables a rapid transition from prototyping to manufacturing. The use of such a source is interesting for PEALD as the processes developed in the lab could be easily implemented at an industrial level.

The present paper will present the development PEALD processes using such a circular ion source.

For over a decade now, several generations of hard, wear-resistant coatings have evolved from industrial coating units using lateral (LARC^®) and central (CERC^®) cylindrical rotating arc cathodes PVD technology, or a combination of these two. From the beginning, nanolayered and nanocomposite coatings were in the focus, while recent developments involved their toughness optimization by structural design on the nano- and microscale.

This contribution will outline recent progress made in adapting these successful multi-zone Quad Coatings^4® to wet-cutting applications in difficult to machine materials, such as nickel-base alloys. Advances were also achieved using both nanolayered and nanocomposite Cr-based Quad Coatings^4® in high-productivity hobbing. A further example of productivity increase in modern metalworking processes is the use of optimized, nanolayered Cr-based coatings for steel sheet fine blanking applications.

Recently, the family of cylindrical rotating cathodes has been complemented by two new members. The first one is the SCiL^® option, a high-rate cylindrical, rotating central magnetron which can be flexibly fitted into PLATIT’s medium-size arc coating equipment. Among others, this technology allows for the deposition of droplet-free ceramic coatings such as TiB₂, at a high degree of process control using a novel, dense magnetron plasma. Cutting tests will be shown in order to demonstrate the excellent adhesion and cutting behavior of this coating in aluminum alloys.

Secondly, a newly designed type of magnetic field for LARC^® cathodes is introduced, that allows for an even higher control of the reactive arc evaporation process. Using the new, very smooth nanolayered and nanocomposite Ti-based coatings derived from these new LARC^® cathodes, advances were achieved for dry hard milling of hardened tool steel molds and dies, using indexable cutting inserts.

PVD processes are widely used to deposit nearly all kinds of coatings on many different substrate materials. Therefore, different groups all over the world are also working on quantitative diagnostics and simulation tools in order to characterize the different zones from target to substrate the particles have to pass before they contribute to the coating itself. In this work, the different physical processes from the sputter event at the target, the particles transport through the magnetized high density zone, the transport through the thinner glow phase to the point of the substrate and the growing layer, are studied by a combination of diagnostic and simulation tools. As diagnostic tools, a combined absorption - emission spectroscopy is applied in order to evaluate on one hand electron density, electron temperature and gas temperature and on the other to determine ground state metal densities, particle fluxes and the corresponding energies. These optical methods are supported by electrostatic probe measurements, TRIDYN-simulation for sputter efficiency, Monte-Carlo simulation for particle transport and profilometer measurements combined with micro balance measurements to obtain the deposited mass. All methods applied together allow for a comprehensive view of the total process and deliver important insight into target poisoning, particles transport behavior, degree of ionization and many other aspects. Finally, a short comparison of different PVD processes like classical magnetron sputtering, HiPIMS and multi frequency capacitive coupled (MFCCP) sputtering will be given.