ICMCTF2016 Session G1: Advances in Industrial PVD, CVD and PCVD Processes and Equipment

Conventional magnetron sputtering cathodes use closed E X B electron drift paths to confine the secondary electrons that are generated at the target surface so that they can efficiently produce ions. The drift paths are closed because the mean free path for ionizing collisions can be many centimeters at magnetron sputtering pressures and the electrons, therefore, must typically travel distances on the order of meters in order to produce enough ions to maintain the plasma. One important consequence of closed drift paths is the formation of an erosion groove in the sputter target, or “racetrack,” which reduces the fraction of target material that can be consumed before the target must be replaced. Rotatable cylindrical magnetrons are often used to address this problem, but with considerable complexity in both cathode design and target fabrication. An alternative method that can result in excellent target utilization with planar targets and no moving parts is the open drift path cathode, in which the magnetic field is essentially uniform over the entire target surface. Open drift path designs have been used in the past, but suffer from a non-uniform sputter rate in the E X B direction as the plasma builds up. However, in the case of cathodes several meters in length that are used to sputter materials with high secondary electron yields, such as oxides, the distance needed for the plasma to reach equilibrium may be acceptably short. Moreover, the advent of dual cathode mid-frequency sputtering, which allows plasmas from adjacent cathodes to couple, and combined DC and RF sputtering, in which the plasma is generated in part by stochastic heating, may make open drift path cathodes useful in a number of applications. In this paper we present a model that describes the E X B drift distance needed for the plasma to reach equilibrium as a function of several key sputtering parameters. The predicted behavior is qualitatively compared to experimental results for dual AC coupled open drift path cathodes and a linear cathode driven with a combination of RF and DC power.

Since introduction of pulsed DC technology in early 1990s a tremendous development in industrial reactive sputtering of insulating films was recorded. Increasing demands for the efficiency of the pulsed plasma processing were stimulating power supply technology development. Thus, advanced power supply features such as fast arc management, adjustable reverse voltage or a wide adjustment range of pulse off time are key factors which enable continuous process optimization.

In this contribution the benefits of advanced pulsed-DC power technology will be illustrated with examples from industrial scale production applications. First, the reduction of the faulty wafers percentage caused by arcing will be discussed on an example of Indium-Tin Oxide layer deposition process for photovoltaic cells production. Afterwards, properties of TiO₂ coatings produced with pulsed-DC technology will be reviewed as example of reverse voltage influence on optical properties of deposited films. Finally, the flexibility of modern pulsed-DC technology will be demonstrated using performance data of dual-functionality units. It will be demonstrated how a specially extended power characteristics allows to use one unit either as a plasma power supply or as a DC/Pulsed-DC bias voltage source.

Plasma emission monitoring (PEM) has been used for a number of years to either monitor the condition or actively control vacuum processes that rely on plasma generation (e.g. Physical Vapour Deposition). This approach to monitoring the process has many advantages such as fast response time, monotonic sensor behaviour and the ability to control uniformity by monitoring different areas of the process. There are however some disadvantages, e.g. there is required a clear line of sight to the plasma that can be obscured by substrate movement, the PEM sensor can become coated by the deposited material and, of course, it can be only be used when the process itself generates a plasma.

Concepts using a remotely generated plasma were developed to address these issues. A convenient method of generating the remote plasma is to use a cold cathode pressure gauge. This sensing method, sometimes referred to as “Penning PEM”, has been used successfully to control a number of process types including non-plasma processes such as reactive E-Beam evaporation.

A new type of remote plasma sensor has been developed, which when combined with advances in miniature spectrometers can be used to perform optical plasma spectroscopy. This has the potential to facilitate its use as a low-cost, multi-purpose vacuum sensor. Presented are a number of examples of its use as an intelligent pressure gauge (penning pressure measurement in conjunction with plasma spectroscopy), etching process monitoring, vacuum quality monitoring, and reactive deposition control.

Also presented is a novel method of sensing species indirectly via the emission lines relating to the sputtered material from inside the sensor. This is shown to enable monitoring and control of processes using remote PEM that are otherwise not possible via conventional plasma spectroscopy.

A deposition rate as high as possible is a key requirement to every commercial coating process. This paper will introduce a new concept for increasing the deposition rate for HiPIMS by a drastically increased frequency of the HiPIMS pluses. The concept is based on the CemeCon door-assembly design, which avoids any cable between pulse unit and cathode, and features a full synchronization between the HiPIMS sources and a dedicated table Bias. This results in highest ionization, reduced resputtering and a so far unachieved deposition rate for HiPIMS. Case studies show how this new hardware design turns the advantages of the HiPIMS technology such as enhanced film adhesion, denser morphology and better coating uniformity all around 3D objects into user benefits for cutting tool applications.

Commercially used coatings for cutting tools are frequently of the Ti_1-xAl_xN type. Adding Si to the composition is a proven technique for machining materials such as titanium and nickel based materials. The study shows how a dedicated HiPIMS multilayer film design considerably improves the adhesion characterised by outstanding scratch loads and provides an appropriate toughness to support ultra-hard TiSiN layers. SEM cross sections show a dense morphology of HiPIMS coatings. Performed nanoindenter test data reveal how HiPIMS films combine high hardness and relatively low Young’s modulus indicating a high coating toughness in a way most favourable for metal cutting.

Indexable inserts account for about 60% of the worldwide metal cutting market. HiPIMS accelerates the trend of using PVD sputter coatings for inserts by a hitherto unknown evenness of the coating distribution all around flank and rake face as well as a perfect film formation at the cutting edge. Case studies show how the effective bombardment of the growing film with highly ionized species further improves the wear resistance for e.g. cast iron machining.

The combination of arc evaporation and HIPAC (classical HiPIMS) as two high ionized deposition processes opens new horizons in tailoring of coating architectures.This enables to generate advanced multilayer, nanomultilayer and nanocomposite coatings. The arc evaporation itself is limited to specific cathode material properties (mostly metal alloys). HIPAC magnetron sputtering processes can be used to atomize and ionize materials which are difficult to evaporate or not evaporable by cathodic arc. The HIPAC magnetron specific materials are used both in the hybrid phase and for deposition of a functional top layer. One characteristic feature of the hybrid process is that the direct arc evaporation with constant current is combined with the pulsed HIPAC process running at specify pulse patterns. Besides the possibility of steering of coating compositions, architecture and morphology also the plasma discharge is changing against the plasma of each individual process. In fact the coating growth conditions are modified in the hybrid process. Selected process features of the hybrid process, selected coating architectures and application results will be presented.

Reactive sputtering and plasma activated chemical vapor deposition (PACVD) both are versatile techniques to deposit high quality coatings on tools and parts. They provide coatings of a wide variety of compositions and structures, including nitrides, carbides, oxides, and also complex compounds. Especially for the coating of parts, i.e. non-flat substrates, the magnetron sputtering technique is established in typical batch coating devices, where substrates rotate during coating processes of typically several hours duration. In contrast, electron beam evaporation (EB-PVD) is a high rate technique mainly established in large area coating of flat substrates, for example metallic strips. So far, few facilities allow application of high rate electron beam evaporation for the coating of 3D-parts. However, EB-PVD in combination with sputtering and PACVD opens up the possibility of highly effective coating processes also for 3D-shaped substrates.

NOVELLA, a novel laboratory equipment for the coating of 3D-parts is a platform that integrates all three coating technologies in a single coating device. Including a load lock and a versatile substrate transport system, it allows establishing direct process sequences of different deposition technologies.

Two examples of material systems will be presented, where combination techniques promise to unite tailored structure with very high deposition rates. On the one hand, carbon-based coatings with multilayer structures are deposited in EB-PVD-PACVD combination processes. These layer systems promise high wear resistance and low friction properties. However, substrate temperature during coating needs attention to achieve optimum properties. On the other hand, stabilized zirconia coatings are conceived to provide thermal, chemical and wear resistance at high temperatures. For these coatings, tailored phase formation can be achieved in pulsed reactive co-sputtering processes as well as in reactive EB-PVD processes by proper choice of deposition parameters and fine tuning of the composition. The formation of specific crystalline phases for certain compositions will be presented for the ternary systems Al-Zr-O and Y-Zr-O. The sputtered coating is completely dense, without voids or open grain boundaries and forms a stable protective coating on the substrate, However, the deposition rate is relatively low. The reactive electron beam evaporation has a factor of hundred higher rate and is therefore suitable to deposit thicker coatings on the dense base layer. Combining both techniques in a single device will allow matching of the structures at the interface.

Chemical vapor deposition coatings on an industrial scale have evolved with the increased requirements demanded by the final applications. The improved coating performance have been realized through a combination of factors related to a better understanding of coating processing, material science and equipment platform. The improved coating process control has allowed researchers and industrialists to reliably broaden the CVD technology leading to further refinements and improvements to commercial CVD coatings. Essential quality criteria are uniformity, reproducibility of film properties, integrity of the surfaces (particles, pores) and adhesion.

This paper deals with innovations on CVD equipment, that are mandatory to produce high quality coatings that meet the demands of the final application. Additional to this also the importance of the process and modules flexibility and equipment safety will be discussed. Specific examples of CVD developments as related to new coating structures as well as enhanced and expanded equipment capability will be presented.