ICMCTF 2025 Session PP-ThP: Plasma and Vapor Deposition Processes Poster Session

In the field of metallic coatings and thin film deposition, precise control of deposition processes has become crucial. These processes are heavily dependent on the chemical/physical processes occurring on the substrate surface. Like any other surface in contact with plasma, a sheath usually develops on the substrate which pulls down the ions out of bulk plasma necessary to complete the process on the substrate. Furthermore, external RF/DC/tailored waveform biases are applied to the substrate to modify the ion behaviors. As it can affect the chemical composition, microstructure and the associated electrical properties of the thin films during plasma assisted deposition processes. Therefore, the characterization of only bulk plasma is not sufficient in providing insights necessary to understand the plasma surface interactions. A high-speed monitoring of the ion energy distribution function and ion flux can lead to enhanced understanding of the plasma surface interactions and improved process performance.

We will highlight the successful measurements done by the Semion RFEA diagnostic under different chamber and bias conditions. Such applications enabling accurate and precise control of deposition process on different materials and various plasma chemistries. It measures the ion energies hitting a surface, the ion flux, negative ions and bias voltage at any position inside a plasma chamber using an array of integrated sensors. On the other hand, the Semion pDC system measures these parameters in real time over an energy range up to 2000 eV (process dependent). It can do sub-microsecond time resolved measurements, for studying pulsed ICPs, or pulsed DC biases, as well as floating and grounded substrate conditions. The Semion Pulsed DC system is the key instrument used to measure the temporal evolution of the ion energy and flux at different times through the pulse period of a pulsed DC plasma process.These measurements are essential for establishing the correlation between the plasma inputs and the ion energy/flux which, in-turn, determines the effectiveness of the surface treatment.

Amorphous carbon thin films with low Secondary Electron Yield (SEY) are critical for applications where electron multipacting limits achievable performance. Such films are effective to mitigate electron cloud formation within the vacuum beam lines of particle accelerators such as the Large Hadron Collider and Super Proton Synchrotron at CERN. They are now also being implemented in the new Electron Ion Collider under construction at Brookhaven National Laboratory.

Research over the last decade has highlighted the significant role of hydrogen presence in the plasma discharge during deposition. Hydrogen incorporation in the films has been shown to increase the SEY, posing a key challenge in coating the extensive beam pipes for particle accelerators.

The quality of high-power impulse magnetron sputtering (HiPIMS) deposited films can often be improved through the effective use of metal-ion synchronization (MIS). However, effective synchronization requires precise measurements of the time-of-flight (ToF) of ions, such that an accelerating bias can be properly synchronized. These measurements are commonly done using time- and energy- resolved mass spectrometry but require calibrations of the transit time of ions inside of the mass spectrometer to accurately report the ToF. The transit time can be calculated by estimating the travel length in varying parts of the spectrometer (e.g. from orifice to detector) and accounting for the interactions of ions with varying electrostatic optics (such as the extractor, energy filter, mass filter, and dynode).The errors associated with these estimations can lead to nonphysical values in a HiPIMS process, such as negative ToFs, or metal ions arriving to the substrate before process gas ions. As a result, many groups emphasize that their calibrations are estimations, or relevant only at sufficiently large time steps. Here we report a practical approach to determine the transit time in the spectrometer experimentally, which was already successfully employed for multiple projects in our group.We use a bipolar HiPIMS power supply to synchronize a gating pulse to the front end of a HiDEN Analytical EQP-300 mass spectrometer. The orifice of the mass-spec (50 µm) was placed at a 12 cm working distance. ToF was then measured by applying a +70 V bias to repel ions, and a 5 µs gating pulse of -30 V to accept them. To prevent interference of the driven front end (kept at +70 V) with the HiPIMS plasma, a grounded shield is placed in front of the mass-spec head with a 1-2 mm opening. The gate was synchronized to the HiPIMS pulse by providing a trigger signal, and data was collected at 5 µs intervals by adjusting the time delay of this pulse. The time-of-flights of Ar⁺, N⁺, Al⁺ , Cu⁺ and W⁺ ions measured in this way are compared to those calculated using mass spectrometry flight tube equations.

Introduction

Traditional coating methods, such as Cathodic Arc Evaporation (CAE), face challenges due to microscopic defects and other limitations. Focused Magnetic Field Magnetron Sputtering (F-MS) has emerged as a transformative solution, achieving a high ionized metal flux fraction even for large-scale targets [1]. Compared to conventional magnetron sputtering (DCMS), F-MS demonstrates a six-fold increase in power density [2]. This advantage, combined with effective cooling and prolonged duty cycles, establishes F-MS as a groundbreaking technology. Its integration into PLATIT’s PVD coating unit, Pi411, represents a significant advancement in hard protective coatings for industrial applications.

Methods

F-MS operates by moving a reduced-size magnetron longitudinally inside a tubular target (Ø110 × 510 mm). This design enables high-power sputtering of up to 30 kW and allows the deposition of dense coatings at a growth rate of 2 µm/h using a 3-fold carousel rotation system.

Results

Coatings of (Al,Cr)N deposited via F-MS exhibited stoichiometric composition, smooth surfaces, and controlled defect levels. Mechanical property tests, plasma diagnostics, and cutting tests demonstrated strong interrelationships and benefits associated with higher power levels. Notably, cutting tests confirmed the superior performance of (Al,Cr)N coatings compared to state-of-the-art CAE coatings.

Conclusion

F-MS technology represents a significant breakthrough in the coating industry, addressing the limitations of traditional methods. Its ability to achieve high plasma power densities and a high degree of ionization for large-scale targets holds immense potential to advance industrial coating practices by enhancing efficiency and enabling new applications.

[1] Hnilica, J. (2024). On direct-current magnetron sputtering at industrial conditions with high ionization fraction of sputtered species. Sur. Coat. Tech., 487, 131028. https://doi.org/10.1016/j.surfcoat.2024.131028

[2] Klimashin, F. (2023). High-power-density sputtering of industrial-scale targets: Case study of (Al,Cr)N. Mat. & Des., 237, 112553. https://doi.org/10.1016/j.matdes.2023.112553

Atomic layer deposition (ALD) is a crucial technique in microelectronics for thin film deposition due to its precise thickness control at the atomic scale, although its sustainability remains a challenge due to its high cost. This work presents the results of a customized, cost-effective and efficient thermal ALD system designed to deposit semiconducting and insulating thin films such as aluminum oxide (Al₂O₃) and zinc oxide (ZnO) films, using trimethylaluminum (TMA) and diethylzinc (DEZ) as precursors, respectively. The oxidizing agent used was hydrogen peroxide (H₂O₂).

Thin films of Al₂O₃ and ZnO were deposited on silicon and corning glass substrates at a temperature of 200°C. Ellipsometry measurements were carried out to determine the thickness, optical constants, band gap and transparency.

The results obtained indicate the presence of a thin film deposited on silicon with 1160 cycles, with a growth rate of 1 Å/cycle which is equivalent to a thickness of ~116.4 nm, as well as a refractive index of 1.76, an extinction coefficient of 0. In addition, the zinc oxide film deposited on corning glass present approximately 80% of transparency in visible region.

The system stands out for its optimized design, easy handling and low cost, which makes it a viable option for academic research and applications in electronics and nanotechnology.

High power impulse magnetron sputtering (HiPIMS) has shown significant potential for thin film deposition. This potential is evident through the enhancement of film quality, specifically in terms of increased density [1] and adhesion [2] along with the diminished requirement for high substrate temperatures [3]. To achieve the optimal deposition process, it is crucial to develop a comprehensive understanding of the plasma-surface interaction at the substrate. This includes, in particular, analyzing the energy flux (transferred power from the plasma to the surface) and its composition.

The energy flux is investigated by using a passive thermal probe (PTP) [4], a so-called non-conventional diagnostic, measuring the integral energy flux to the substrate. Insights into the composition of the energy flux are gained by applying a bias voltage to the thermal probe [4] and using a novel combination of PTP with a retarding field analyzer (RFA) [5]. This allows to measure simultaneously the ion energy distribution (IED) and to perform energy-resolved energy flux measurements. In addition, the neutral energy flux component can be quantified by repelling all charge carriers by the grid potentials. Since the energy resolution and sensitivity of the RFA is limited, the measurements of the IED are completed by energy-resolved mass spectrometry, both time-averaged and time-resolved [6].

These diagnostics have been applied to compare HiPIMS and DC magnetron sputtering processes with same gas pressure and average power sputtering a planar copper target in argon atmosphere. In total, the mean energy flux to the substrate is lower in HIPIMS operation. Hence, temperature sensitive substrates are better protected. Normalizing the energy flux to the deposition rate, which is lower in HiPIMS as well, gives a higher value for the energy flux per adatom in HiPIMS, which can be attributed to the higher kinetic energy of sputtered particles. The dependence of the energy flux on the excitation mode (DC, HiPIMS), the HiPIMS pulse parameters, as well as on power and pressure is investigated. The advantages and limitations of the diagnostics used are discussed.

[1] J. Alami et al., J. Vac. Sci. Technol. A 23 (2005) 278–280.

[2] R. Bandorf et al., Surf. Coat. Technol. 290 (2016) 77-81.

[3] E. Wallin et al., Europhysics Letters 82 (2008) 36002.

[4] H. Kersten et al., Thin Solid Films 377–378 (2000) 585–591.

[5] F. Schlichting and H. Kersten, EPJ Techniques and Instrumentation 10 (2023) 19.

[6] J. Benedikt et al., J. Phys. D: Appl. Phys. 45 (2012) 403001.

Hydrogen production through water electrolysis provides clean source of energy and the process has a zero-carbon emission cycle. Different performance parameters have been focused to improve the hydrogen production but equally important is the oxygen evolution reaction at the anode side which is the other half cell reaction in the process. Half-cell reaction at anode side has the problems of slower reaction kinetics, complex chlorine oxidation, cost and the degradation of electrode materials like RuO₂/IrO₂, and low current densities which do not meet industrial requirements.

We have used DC magnetron sputtering to deposit Ni-Fe bimetallic thin films over SS-316 substrate as efficient and cost-effective anode material. Ni-Fe bimetallic compounds have been reported to be used in this type of process but unlike the traditionally reported wet chemical synthesis techniques, we have used PVD technique to have superior control over micro structure for better performance and to avoid chemical waste.

In a novel effort we have deposited thin films with 200 nm thickness through DC magnetron sputtering. Thin targets of Invar and Ni with 1 mm thickness were sputtered under 10 bar Argon pressure to minimize the paramagnetic behavior of Ni and Fe. Different compositions were achieved by varying the sputtering power on Ni target from 500-1200 W while Invar was sputtered at fixed power of 1000 W. Compositions were achieved in the range of 20-40 atomic % Fe in Ni which were analyzed through Energy Dispersive Spectroscopy (EDS). Scanning Electron Microscopy (SEM) analysis showed that films had columnar structure which increases the available surface area. Atomic force microscopy (AFM) analysis showed very low roughness of the films in the range of 1-2 nm. X-Ray diffraction (XRD) analysis showed the presence of FeNi₃ phase which has an efficient performance in the reversible oxidation-reduction reactions at anode.

Electrochemical testing techniques including linear sweep voltammetry (LSV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed in a three-electrode cell with Ag/AgCl saturated in KCl reference electrode, graphite counter electrode and 1 M KOH electrolyte. Composition of Fe₂₄Ni₇₆ (24 atomic % Fe in Ni) was found to be the optimum composition as it achieved remarkable current density of 335 mAcm^-2 while operating at overpotential of 1.7 mV vs RHE which is the benchmark overpotential beyond which Chloride oxidation becomes thermodynamically possible. EIS analysis showed that Fe₂₄Ni₇₆ composition has the least charge transfer resistance (R_CT) with uniformity and behavior close to an ideal capacitor.

Silicon carbide (SiC) has a wider band gap enrgy than silicon (Si), enabling efficient operation in high-temperature environments. Its strong Si-C bonds also provide exceptional physical and chemical stability. These properties make SiC an ideal material for power semiconductor devices, including insulated gate bipolar transistors (IGBTs), Schottky barrier diodes, and metal-oxide-semiconductor field-effect transistors (MOSFETs).

SiC etching is traditionally performed using SF₆, CF₄, and CHF₃ plasmas. However, these gases have stable molecular structures, leading to high global warming potentials (GWPs) and long atmospheric lifetimes. Recognized as greenhouse gases under the Kyoto Protocol, their emissions are subject to reduction targets outlined in the Paris Agreement. To minimize environmental impact, there is a growing need for low-GWP alternatives in SiC etching.

This study explores the use of heptafluoroisopropyl methyl ether (HFE-347mmy) as a plasma etchant for SiC. With a GWP of approximately 530, HFE-347mmy significantly reduces environmental impact compared to SF₆, CF₄, and CHF₃. The etching characteristics were investigated by varying the HFE-347mmy/O₂ flow-rate ratio and adjusting the bias voltage. Additionally, radical concentrations, surface composition, and substrate roughness were analyzed to elucidate the etching mechanism.

Optical emission spectroscopy (OES) is a non-invasive tool that enables plasma monitoring without affecting the plasma state. It operates by analyzing light emitted from excited atoms or ions within the plasma. This analysis provides information about the chemical composition and energy state of the plasma thus allowing for the prediction of process results. Researchers have conducted studies analyzing OES signals during deposition process to predict deposition characteristics such as growth rate, film thickness, uniformity. However, research on predicting the refractive index, which is one of the important deposition characteristics, has been limited. In this study, the deposition rate and refractive index of silicon nitride (SiN_x) were predicted using OES signal analysis in plasma enhanced chemical vapor deposition (PECVD) with trisilylamine (TSA), NH₃, and N₂ gases. The deposition rate was correlated with the I_N2+/I_N2 and I_Ha/I_Hb line ratio, which can estimate the electron temperature, as the deposition rate is influenced by the electron temperature that activates dissociation and ionization. The refractive index determined by the N/Si ratio in SiN_x film was correlated with the ratio of SiH and NH radicals in the plasma transferred to the film. The relative radical densities were investigated using the I_SiH/I_N2 and I_NH/I_N2 line ratios, known as actinometry, after demonstrating the overlap of electron energy distribution function (EEDF) and excitation cross sections. The deposition rate (R² = 0.85, MAPE = 3.66%) and refractive index (R² = 0.95, MAPE = 0.27%) investigated in linear regression analysis showed very high prediction accuracy.

A pre-hydrogen plasma trimming treatment was applied on p-type germanium (Ge) metal oxide semiconductor device as a surface engineering process, which significantly improve the interface quality between p-type Ge and alloy-like hafnium nitride buffer layer. Generally, a post interfacial layer treatment is difficult to affect the defect distribution located at the bottom interface. Therefore, a pre-plasma treatment is well discussed in this work. After detailed analyzing material and electrical characteristics, the sample after the pre-hydrogen plasma trimming treatment exhibits lower equivalent oxide thickness, lower interface trap density, narrower frequency dispersion, better uniformity and reliability. This improvement can be attributed to the reduction of both border traps and surface roughness. It is believed that this research will provide an important reference for the high mobility Ge based device fabrication.

The lack of high-mobility p-type metal oxide materials has become a critical bottleneck in the development of amorphous oxide semiconductor (AOS)-based PN junctions. Recently, the emergence of high hole mobility tellurium has been successfully applied in high-performance, stable p-type thin-film devices and complementary logic circuits, demonstrating significant potential for integration into AOS-based PN junctions. However, the electronic transport mechanisms in AOS-based PN junctions remain unclear. In this study, p-type tellurium-based oxide films and n-type indium-based oxide films were successfully deposited at room temperature to construct AOS-based PN junctions. The structural and material properties were systematically analyzed using techniques such as X-ray photoelectron spectroscopyand transmission electron microscopy, and the electronic conduction mechanisms within the AOS-based PN junctions were thoroughly investigated. The results confirm the feasibility of AOS-based PNjunctions and provide valuable technical insights for applications in photodetectors and solar cells.

Aluminium is an attractive material for bipolar plates for polymer electrolyte membrane fuel cells due to its low weight, excellent thermal and electrical conductivity, as well as good recyclability. However, to achieve the necessary low contact resistance and corrosion stability, a suitable surface coating is needed. We could previously show that the corrosion current can be significantly reduced from 20 to 0.2 μA·cm^-2 by coating the Al surface with a thin film of Ti. The coated surfaces, however, exhibited limited durability during potentiostatic testing because of a large number of defects in the Ti layer.

This contribution analyses formation of defects in Ti thin films deposited by magnetron sputtering. Cross-sectional analysis revealed that these defects are initiated already at the Al/Ti interface and enhanced during the deposition. Ti growth by High Power Impulse Magnetron Sputtering and by direct current Magnetron Sputtering on different Al surfaces and on Si is investigated to identify the effect of the surface and growth conditions on the film growth.

As the demand for lightweight and advanced core components increases across various industry, there is a growing need for difficult-to-machine materials and high-precision machining. High-precision machining is particularly crucial in advanced industries such as automotive, aerospace, and medical fields. Hard coating technology applied to cutting tools is a key technology that directly impacts tool life and the quality of machined products, with arc ion plating coating method being widely utilized. Arc ion plating technology is the most widely used deposition method in these industries due to its high ionization efficiency and ion energy, resulting in rapid deposition rates, excellent adhesion, high hardness, and the ability to form uniform coating layers on complex-shaped components. However, defects (called as droplets) generated by the discharge mechanism can be deposited in the coating layer, causing defects inside the coating. These defects may lead to reduced component life and decreased quality of machined products.

This study analyzes the characteristics of nitride coatings based on the control of arc ion plating process parameters. Additionally, cutting tools with these coatings were subjected to life tests. Based on the experimental results, we will discuss optimization strategies for the arc ion plating process, the resulting changes in coating film characteristics, and the performance improvements of cutting tools.

Acknowledgment:

This research was supported by the Korea SMEs and Startups Agency (KOSME) grant funded by the Ministry of SMEs and Startups (RS-2024-00510381, Development of Ion Etching Technology and Nitride Coating Process for Arc Ion Plating System in Precision Machining).

Nickel-based superalloys such as Inconel 718 are widely used in the aerospace and energy industries due to their excellent heat resistance and ability to maintain mechanical properties at temperatures exceeding 700°C. However, these materials are notoriously very difficult to machine due to severe work hardening during cutting and material adhesion to the tool edge, which causes deformation and damage. To enhance the wear resistance and edge durability of PVD-coated cutting tools in Inconel machining, extensive research has been conducted on machining methods and coatings, but an optimal solution has yet to be achieved.

PVD coatings for cutting tools are typically deposited using sputtering or cathodic vacuum arc (CVA) processes, both of which have limitations for Inconel machining. Sputtering produces smooth coatings but suffers from lower hardness and productivity. CVA enables high deposition rates and dense coatings, but the process releases droplets that increase surface roughness, reducing cutting performance. In Inconel machining, it has been reported that work material can fill voids around droplets, leading to film damage.

A previous study by KOBELCO compared AlCrN coatings deposited using a conventional arc evaporation source and a novel “μ-ARC” source. The μ-ARC process was found to significantly reduce surface roughness and micro-particles (MPs), improving durability in cutting tests. However, due to the chemical reactivity between AlCrN and nickel-based materials, Cr-containing coatings are generally unsuitable for Inconel machining. Instead, TiAlN and TiAlN+X coatings are more commonly applied.

In this study, TiAlN and TiAlN+X coatings were deposited using both conventional and μ-ARC evaporation sources. The effects of the evaporation source and metal X addition on the film’s microstructure, mechanical properties, and crystal structure were analyzed. Based on these evaluations, optimal deposition conditions for carbide end mills were determined, and the machining performance of TiAlN and TiAlN+X coated tools in Inconel cutting was assessed. Additionally, thermal stability and adhesion resistance of the coatings were evaluated. The results confirm that μ-ARC coatings exhibit improved adhesion resistance and thermal stability, leading to enhanced cutting performance in Inconel machining. These findings contribute to the development of high-performance coatings for improved tool longevity and efficiency.

Inconel is a material with low thermal conductivity, making it challenging to machine due to the high cutting edge temperature and rapid tool wear. To extend tool life, coating performance is crucial. Although various coatings have been developed for machining Inconel, an optimal solution has yet to be established.

Common coating processes for cutting tools include cathodic vacuum arc (CVA), sputtering, and chemical vapor deposition (CVD), each with its limitations. Sputtering produces smooth coatings but suffers from lower hardness and productivity. CVD coatings offer excellent toughness at high temperatures, making them suitable for turning; however, their intrinsic tensile stress makes them less ideal for milling. The arc process enables dense coatings with high compressive stress and high productivity, but excessive droplet deposition increases surface roughness, reducing cutting performance. In Inconel machining, it has been reported that work material can fill voids around droplets, leading to film damage.

A previous study by KOBELCO investigated AlCrN coatings using both a conventional arc evaporation source and a novel “μ-ARC” source. The μ-ARC process was found to reduce surface roughness and micro-particles (MPs), improving durability in cutting tests. However, due to the chemical reactivity between AlCrN and nickel-based materials, Cr-containing coatings are generally unsuitable for Inconel machining, and TiAlN or TiAlN+X coatings are commonly used instead.

This study explores the deposition of TiAlN and TiAlN+X films using both conventional and μ-ARC evaporation sources. The effects of the evaporation source and metal X addition on the film’s microstructure, mechanical properties, and crystal structure are analyzed. Based on these evaluations, optimal deposition conditions for carbide end mills were determined, and machining performance of TiAlN and TiAlN+X coated tools in Inconel cutting was evaluated. The findings provide insights into the development of high-performance coatings with improved durability and cutting efficiency.