Physical Vapor Deposition TiN Research Articles

Duplex surface engineering of cold spray Ti coatings and physical vapor-deposited TiN and AlTiN thin films

The feasibility of a duplex coating based on cold spray technology and magnetron sputtering was evaluated for repair applications requiring a ‘thin-on-thick’ layered structure. Commercially pure angular-shaped Ti grade 4 particles are fed to a cold spray gun and accelerated toward a Ti alloy substrate to deposit thick coatings (∼4.5 mm). TiN and AlTiN thin films are deposited on polished cold spray coatings using a four-source closed-field unbalanced magnetron sputtering (CFUBMS) system. Microstructure was characterized using focused ion beam (FIB) lift-out, scanning electron microscopy (SEM), and electron channeling contrast imaging (ECCI). The nanoindentation technique was used to evaluate the mechanical properties of coatings. The H/E ratios and H3/E2 ratios for TiN films were found to be 0.098 and 0.26 GPa, respectively, while those for AlTiN films were measured at 0.066 and 0.052 GPa, respectively, suggesting higher capacity of TiN films to withstand both elastic and plastic deformation. Using scratch testing, the adhesion of TiN and AlTiN thin films to cold spray Ti was investigated, with TiN-Ti duplex coatings exhibiting better performance compared to AlTiN-Ti coatings. Tribological testing was performed on duplex coatings using a reciprocating tribometer equipped with an alumina ball counterface. The wear rate for AlTiN-Ti coatings after 2000 sliding cycles was found to be (1.0 × 10−3 ± 0.1 × 10−3 mm3/Nm), three orders of magnitudes higher than that for TiN-Ti (8 × 10−6 ± 2 × 10−6 mm3/Nm. SEM was used to reveal worn surface morphologies and cross-sectional analysis of the wear track. Subsurface microstructural changes due to wear were examined using focused ion beam cross-sectioning, revealing bending cracks and tribofilm formation.

Characterizing the composition, structure, and mechanical properties of magnetron sputtering physical vapor deposition TiN and TiSiN coatings

Ti(Si)N coatings were deposited on Si wafers via magnetron sputtering physical vapor deposition technique. Scanning electron microscopy and atomic force microscopy were used to study the morphologies, grain size, and thicknesses of the different films. X-ray diffraction confirmed the formation of the titanium nitride cubic phase. X-ray photoelectron spectroscopy (XPS) was used to study the silicon and oxygen levels in the films, and high resolution XPS was used to determine the surface oxide to nitride ratios as well as the silicon–nitrogen environment. The hardness of these films was then determined with nanoindentation. It was shown that grain size and film density could be controlled by the Si level and the ion bombardment to eliminate the oxygen level in the nitride coatings, which led to the harder films. It was suggested that due to the miscibility of Si, a ternary TiSiN solid solution was formed. Stronger (200) orientation of the TiN B1-NaCl crystals was associated with increased hardness of the coatings. This crystalline structure was preserved after incorporating Si.

High-Throughput Screening of Optimal Process Parameters for PVD TiN Coatings With Best Properties Through a Combination of 3-D Quantitative Phase-Field Simulation and Hierarchical Multi-Objective Optimization Strategy

Physical vapor deposition (PVD) is one of the most important techniques for coating fabrication. With the traditional trial-and-error approach, it is labor-intensive and challenging to determine the optimal process parameters for PVD coatings with best properties. A combination of three-dimensional (3-D) quantitative phase–field simulation and a hierarchical multi-objective optimization strategy was, therefore, developed to perform high-throughput screening of the optimal process parameters for PVD coatings and successfully applied to technically important TiN coatings. Large amounts of 3-D phase-field simulations of TiN coating growth during the PVD process were first carried out to acquire the parametric relation among the model parameters, microstructures, and various coating properties. Experimental data were then used to validate the numerical simulation results and reveal the correlation between model parameters and process parameters. After that, a hierarchical multi-objective method was proposed for the design of multiple coating properties based on the quantitative phase–field simulations and key experimental data. Marginal utility was subsequently examined based on the identification of the Pareto fronts in terms of various combinations of objectives. The windows for the best TiN coating properties were, therefore, filtered with respect to the model/process parameters in a hierarchical manner. Finally, the consistent optimal design result was found against the experimental results.

Duplex treatment of arc plasma nitriding and PVD TiN coating applied to dental implant screws

In modern dentistry, surface modification technology is critical for the long-term service of dental implants. The purpose of this study was to evaluate the effects of the duplex treatment of arc plasma nitriding and TiN coating on the mechanical behavior of implant systems. The Ti6Al4V screws of dental implants were treated by physical vapor deposition (PVD), arc plasma nitriding (APN), and arc plasma nitriding-physical vapor deposition (APN-PVD). The surface characteristics, loosening properties, and fatigue performance of different treated screws were analyzed. The results showed that APN-PVD duplex treatment produced a gradient surface structure, reduced the surface roughness, and improved the TiN coating adhesion. Compared with the PVD-treated screws alone, APN-PVD-treated screws improved anti-loosening performance, reduced surface wear, and prolonged fatigue life. Duplex treatment by arc plasma nitriding and TiN coating may be a method suitable for dental applications.

Influence of plasma nitriding pre‐treatment on the corrosion and tribocorrosion behaviours of PVD CrN, TiN and AlTiN coated AISI 4140 steel in seawater

AbstractCrN, TiN and AlTiN coatings were applied by the Physical Vapour Deposition (PVD) method on AISI 4140 and plasma nitrided (PN) AISI 4140 steel. The study aimed to investigate the effect of plasma nitriding before PVD on the corrosion and tribocorrosion behaviour of AISI 4140 steel in seawater. The electrochemical corrosion behaviour of the samples was evaluated in natural seawater by the potentiodynamic polarisation method. Tribocorrosion tests were performed against alumina in natural seawater under 5 N load and open circuit potential (OCP) using a ball‐on‐disk tribometer coupled with an electrochemical cell. As a result of the study, plasma nitriding applied before the coating significantly improved corrosion and tribocorrosion resistance of PVD CrN, TiN and AlTiN coatings. Besides, it was concluded that duplex treated low alloy AISI 4140 steel could be a candidate instead of stainless steel in tribocorrosion conditions for the marine environment.

Superlubricity achieved with TiN coatings via the in situ formation of a carbon-based film at the sliding interfaces

This work aimed to develop an efficient lubricant for physical vapor-deposited TiN coatings on steel by adding cyclopropane-carboxylic acid (CPCa) to PAO4 base oil to enhance boundary lubrication. Results showed that an ultralow coefficient of friction (0.008) and wear rate (7.0 × 10-8 mm3/N∙m) were obtained for the steel/TiN sliding contact using PAO4+2.5 wt % CPCa oil due to the in situ formation of a carbon-based lubricating tribofilm during the sliding process.

Room temperature PVD TiN to improve the ferroelectric properties of HZO films in the BEoL

Zirconium-doped hafnium oxide (HZO) crystallizes at low temperatures and is thus ideal to implement ferroelectric (FE) functionalities into the back end of line (BEoL). Therefore, metal-ferroelectric-metal (MFM) capacitors are of great interest. Placed in the BEoL, they can be connected either to the drain- or the gate-contact of a standard logic device to realize different emerging FE-embedded non-volatile memory (eNVM) concepts. However, the low crystallization temperature increases also the risk for a premature crystallization of the HZO films during the growth of the top electrode (TE), in particular, if high-temperature processes like atomic layer deposition (ALD) or chemical vapor deposition (CVD) are used. Herein, the TE is deposited at room temperature via physical vapor deposition (PVD). The impact of different process gas flows on the FE properties of the HZO films is studied by X-ray diffraction and polarization versus electric field measurements.Graphic abstract

Mechanical and High-Temperature Tribological Properties of Cr3C2-NiCr/TiN Duplex Coating

Preparation of duplex coating is an innovative way to improve components surface in terms of mechanical and tribological properties by the combination of high velocity oxy-fuel (HVOF) and physical vapor deposition (PVD) technologies. The present work focused on the construction, mechanical properties and high temperature tribological behaviors of the duplex coating consisting of a thick HVOF Cr3C2-NiCr interlayer and a thin PVD TiN top layer, as well as compared it with the Cr3C2-NiCr coating and the single TiN film. The results showed that the Cr3C2-NiCr/TiN duplex coating exhibited higher hardness, elastic modulus, H/E and H3/E2 ratios and superior load-bearing capacity than the single TiN film. The introduction of Cr3C2-NiCr intermediate layer did not affect the microstructure of TiN film but significantly improved the adhesion strength between TiN film and substrate, as well as the wear resistance sliding against WC ball at different temperatures. In addition, the friction and wear mechanism of the Cr3C2-NiCr coating, TiN film and Cr3C2-NiCr/TiN duplex coating was revealed by investigating the friction-induced morphological and structural evolutions of the sliding surface at elevated temperature.

Strategies for Reducing Particle Defects in Ti and TiN Thin-Film Deposition Processes

Generation of particle defects in semiconductor manufacturing is inevitable, but it has to be minimized to enhance IC yield. There are various causes for the generation of particle defects in different semiconductor manufacturing processes, such as diffusion, thin-film deposition, lithography, etch, and clean. In this paper, primary defect generation mechanisms in thin-film deposition processes, such as atomic layer deposition TiN, radio frequency physical vapor deposition Ti, and physical vapor deposition TiN, are discussed. Various strategies, such as periodic clean optimization, on-load clean, idle pasting, periodic pasting optimization, kit life optimization, target burning optimization, and kit hardware selection that reduce the generation of defects in the thin-film deposition processes are presented. This paper also discusses hardware-induced surface defect and solutions to reduce them.

The Influence of Ultrasonic Vibration Frequency on the Properties of TiN Coated Biomedical Ti–13Zr–13Nb

Bare biomedical grade titanium alloys are prone to degradation when in a body fluid environment. Surface coatings such as Physical Vapor Deposition (PVD) can serve as one of the options to minimize this issue. Past reports showed that the PVD coated layer consists of pores, pinholes, and columnar growths which act as channels through which the aggressive medium attacks the substrate. Duplex and multilayer coatings seem able to address this issue to varying extents but at the expense of manufacturing time and cost. In this paper, the effect of an ultrasonic vibration frequency on PVD TiN coated Ti–13Zr–13Nb biomedical alloy was studied. Disk type samples were prepared and coated with TiN at fixed conditions: bias voltage (−125 V), substrate temperature (300 °C), and nitrogen gas flow rate (300 standard cubic centimeters per minute (SCCM)). An ultrasonic vibration was then subsequently applied to the TiN coated samples at frequencies of 8 kHz and 16 kHz for 5 min. All TiN coated samples treated with ultrasonic vibrations exhibited a higher corrosion resistance than the untreated ones. Microstructure analysis under Field Emission Scanning Electron Microscopy (FESEM) confirmed that the coated sample at frequencies of 16 kHz produced the most compact coating. It is believed that the hammering effect of the ultrasonic vibration reduced the micro channels’ size in the coating and thus decelerated the corrosion’s attack.

Control of TiN oxidation upon atomic layer deposition of oxides.

The interfaces of a physical-vapor deposited (PVD)-TiN electrode with atomic-layer deposited (ALD) HfO2 layers were studied using photoelectron spectroscopy with high kinetic energies of photoelectrons enabling nondestructive in-depth chemical profiling and phase analysis. Our results reveal the presence of only TiNxOy at the TiN/ALD-HfO2 interface with no measurable traces of the TiO2 phase. By contrast, the interface formed by ALD of HfO2 on top of PVD TiN contains both TiO2 and TiNxOy compounds and may be compared to an HfO2/TiN interface with intentional ALD TiO2 interlayer (IL) formation prior to HfO2 growth. Pre-growth of ALD Al2O3 IL drastically reduces the TiO2 and TiNxOy amounts present at the HfO2/TiN interface, which can be ascribed to oxygen scavenging from the initially oxidized TiN surface by energetically more favorable Al-O bonds. The present study demonstrates that the amount of TiO2 phase can be effectively controlled, i.e., increased or decreased, during the ALD process enabling engineering of vacancy-mediated processes.

Dry machining of aluminum for proper selection of cutting tool: tool performance and tool wear

Machining of aluminum and its alloy is very difficult due to the adhesion and diffusion of aluminum, thus the formation of built-up edge (BUE) on the surface. The BUE, which affects the surface integrity and tool life significantly, affects the service and performance of the workpiece. The minimization of BUE was carried out by selection of proper cutting speed, feed, depth of cut, and cutting tool material. This paper presents machining of rolled aluminum at cutting speeds of 336, 426, and 540 m/min, the feeds of 0.045, 0.06, and 0.09 mm/rev, and a constant depth of cut of 0.2 mm in dry condition. Five cutting tools WC SPUN grade, WC SPGN grade, WC + PVD (physical vapor deposition) TiN coating, WC + Ti (C, N) + Al2O3 PVD multilayer coatings, and PCD (polycrystalline diamond) were utilized for the experiments. The surface roughness produced, total flank wear, and cut chip thicknesses were measured. The characterization of the tool was carried out by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) pattern. The chip underface was analyzed for the study of chip deformation produced after machining. The results indicated that the PCD tool provides better results in terms of roughness, tool wear, and smoother chip underface. It provides promising results in all aspects.

Friction and wear behaviors of TiCN coating based on electrical discharge coating

Titanium carbonitride (TiCN) coating was prepared on 45# carbon steel by electrical discharge coating (EDC), and the compositions, morphology and microstructure of the coating were studied. In addition, its friction and wear behaviors relative to the physical vapor deposition (PVD) TiN coating were investigated. The results show that the TiCN coating features a thickness of 15 μm with a primary phase of TiC0.3N0.7. The wear rates of the two coatings have no clear distinction at low applied loads. However, severe abrasive wear appears in the PVD TiN coating when the applied load exceeds 30 N, while the TiCN coating features better wear resistance. The abrasive wear with coating peelings is found to be the predominant wear mechanism at high applied loads.

Nanostructuring and property modification of arc PVD TiN coatings by nickel

We have studied structure and phase formation processes in the Ti-N-Ni system during the growth of coatings by cathodic arc physical vapor deposition (PVD). The incorporation of nickel has been shown to reduce the crystallite size of TiN from 100–120 to 15–18 nm. This is accompanied by a transition from a columnar microstructure, typical of PVD TiN coatings, to an equiaxed one. In the concentration range 0 to 12–13 at %, the nickel in the coatings is X-ray amorphous. Further increasing the nickel content leads to the formation of the intermetallic phase TiNi, which is in turn accompanied by the generation of pores in the structure of the coating. We have determined optimal nickel concentrations in the composite coatings (8–12 at %) that ensure hardness, Young’s modulus, H3/E2, and H/E of 52 GPa, 516 GPa, 0.57 GPa, and 0.104, respectively. We have demonstrated that the nanostructured TiN-Ni (2.8 to 12 at % Ni) coatings undergo failure by a cohesion mechanism. Complete wear of the coatings only occurred starting at a load of 90 N, attesting to high adhesion/cohesion strength of the system.

ALD TiN Barrier Metal for pMOS Devices With a Chemical Oxide Interfacial Layer for 20-nm Technology Node

We propose the use of atomic layer deposition (ALD) TiN barrier to replace physical vapor deposition TiN barrier for high- k last/gate last pMOS devices with a chemical oxide interfacial layer in 20-nm technology node. It was found that the pMOS devices with ALD TiN exhibit lower gate leakage current density (Jg) and equivalent oxide thickness. Furthermore, it was found that we could achieve larger flat-band voltage (Vfb) and larger equivalent work function from the pMOS devices with ALD TiN barrier. It was also found that we could further improve the performances of the fabricated pMOS devices by increasing the ALD TiN thickness from 2 to 3 nm.

PVD TiN for Bottom Electrode of Phase Change Memory

Phase change memory (PCM) has been regarded as a promising candidate of the next generation nonvolatile memory. However, the application of PCM has been limited by the high power required to reset the device (changing from crystalline to amorphous state by melting the phase change material). TiN is proposed to be bottom electrode of PCM due to its lower thermal and more suitable electrical conductivity than that of tungsten, which can drastically reduce reset power by less thermal loss and higher heating efficiency. This article shall report several TiN films with different Ti/N ratio prepared by physical vapor deposition (PVD). The Ti/N ratio, resistivity, thermal stability, anti-erosion capability in HF and film density of PVD TiN films are characterized and optimized. We demonstrate the step coverage and contact resistance of the 10nm PVD TiN as the sidewall bottom electrode.

Selective etching of TiN over TaN and vice versa in chlorine-containing plasmas

Selectivity of etching between physical vapor-deposited TiN and TaN was studied in chlorine-containing plasmas, under isotropic etching conditions. Etching rates for blanket films were measured in-situ using optical emission of the N2 (C3Πu →B3Πg) bandhead at 337 nm to determine the etching time, and transmission electron microscopy to determine the starting film thickness. The etching selectivity in Cl2/He or HCl/He plasmas was poor (<2:1). There was a window of very high selectivity of etching TiN over TaN by adding small amounts (<1%) of O2 in the Cl2/He plasma. Reverse selectivity (10:1 of TaN etching over TiN) was observed when adding small amounts of O2 to the HCl/He plasma. Results are explained on the basis of the volatility of plausible reaction products.

Advanced PVD TiN for Metal Gate Application

High-κ metal gate is widely used for 32nm and beyond to enable scaling down of MOSFET geometry while improving device speed and gate leakage. This structure requires a good work function metal to tune Vt as well as a stable metal barrier to control inter-diffusion and interaction between the multiple metal gate layers. To meet the integration requirements of metal gate, it is very important to choose the proper metal thin film process. Its stability and excellent integration performance make TiN a good option for metal gate application, but the traditional PVD (physical vapor deposition) TiN process still faces issues, such as plasma damage and poor gap-fill capability. RFPVD (radio frequency physical vapor deposition) TiN has been developed for metal gate application. This paper presents studies of the film texture, density, and inter-diffusion base on different metal gate layers. MOSCAP (metal oxide silicon capacitor) tests showed that RF PVD TiN exhibits low Dit and device leakage. To meet the strict gap-fill requirement of the gate-last scheme, physical gap-fill performance of the high-pressure RF TiN process was checked. It achieved more than 60% bottom coverage and minimal sidewall coverage, allowing the electrode gap-fill window to be effectively enlarged.

Comparative analysis of wear on PVD TiN and (Ti1−x Alx)N coatings in machining process

Ti3Al3N ternary coatings processed by Physical Vapor Deposition (PVD) are frequently used in machining inserts particularly for the automotive and aerospace industries. They possess many good qualities generally required in a cutting tool and high metal removal rates can be achieved with them. (Ti1−x Alx)N ternary coatings may form different crystalline structures (single cubic phase, mixed cubic and hexagonal phases, and single hexagonal phase) during processing, depending on the Al (at%) content. It is therefore important to study the relationship between the structures and properties of the coatings and their performance during machining under industrial cutting conditions. In the present work, the performance of carbide tools (ISO grade K10) with different (Ti1−x Alx)N coatings is investigated during continuous turning of nodular cast iron. Ternary coatings were processed by PVD in two ranges of stoichiometric ratios of Ti/Al, namely: (0.20≤x≤0.30) and (0.60≤x≤0.70). Machining trials using TiN coating were also performed for comparative analysis. Tool wear analysis was conducted within a Scanning Electron Microscope (SEM) and also using Energy Dispersive Spectroscopy (EDS). Statistical analysis of the results of a design of experiment test series indicated that the tools with low Al content coatings – (Ti0.71 Al0.29)N – exhibited superior performance in terms of wear rate and indentation test. However, tools coated with both low and high Al contents of (Ti1−x Alx)N presented higher wear rates than the TiN coated tools.

Triode plasma diffusion treatment of titanium alloys

In this paper the structure, properties and tribological behaviour of the binary β titanium alloy Ti–15Mo have been investigated. Low-pressure triode plasma diffusion processes were used to improve the wear resistance of this material and the results were compared with equivalent work carried out on the more popular and better known α+β alloy, Ti–6Al–4V. In order to study these materials, X-ray diffraction, micro- and nano-indentation hardness, surface profilometry, optical microscopy, electron backscatter diffraction and ball-on-plate reciprocating wear testing were employed. These techniques show stark differences between the two titanium alloys, not only in their structure and properties, but also in their response to the surface engineering treatments investigated. It was found that the relatively coarse-grained Ti–15Mo experiences a larger increase in surface roughness when plasma diffusion-treated, particularly where nitrogen is used to provide the active ionised gas species. However, physical vapour deposition (PVD) of a thin pure α-Ti layer can effectively reduce this roughening effect to acceptable levels without compromising the diffusion treatment efficacy in terms of the case hardness and depth achieved. Once a thin PVD layer of α-Ti has been deposited onto the untreated Ti–15Mo, significant improvements in the wear resistance of this alloy can be achieved by either nitrogen plasma-diffusion treatment or by a duplex process routine which includes the final deposition of a hard PVD TiN ceramic coating. Furthermore, the results presented here show that triode plasma oxidation is also a simple (yet very effective) method that can be used to drastically improve the tribological performance of this alloy, where the careful control of (oxide) compound layer formation can produce a hard and wear-resistant surface without the need for duplex PVD coating.