TiN Layer Thickness Research Articles

Characteristics of Cobalt Silicide by various Film Structures

The process is widely employed in a salicide as well as an ohmic layer process. In this experiment, we investigated the characteristics of films by combinations of I-type (TiN 100/Co 150), II-type(TiN 100/Co 150/Ti 50), III-type(Ti 100/Co 150/Ti 50), and IV-type(Ti 100/Co 150/Ti 100). Sheet resistances of show the lowest resistance with 2.9 /sq. in a TiN/Co condition and much higher resistances in conditions simultaneously applying Ti capping layers and Ti interlayers. Though we couldn't observe a roughness dependence on the film stacks from RMS values, Ti capping layers turned into 78∼94 thick TiN layers of (200) preferred orientation at ambient. In addition, Ti interlayers helped to form the epitaxial with (200) preferred orientation and ternary compounds of Co-Ti-Si. We propose that film structures of II-type and III-type may be appropriate in the salicide process and the ohmic layer process from the viewpoint of Co diffusion kinetics and the CoSiepitaxy.

イオン・プレーティング法により形成したＳｉＯ２／Ｃｕ／ＴｉＮ積層膜のＸ線的評価

Residual stress in a coating film is influenced by an undercoated layer in a multi-layered film system. The present study investigates residual stress as well as crystal texture in two- and three-layered films, i. e., Cu/TiN film, SiO2/Cu film and SiO2/Cu/TiN film deposited on glass substrates. TiN film was first deposited by arc ion plating on the substrate as an undercoated layer and then Cu and SiO2 films were deposited on it by plasma coating. The crystal structure and the residual stress in the deposited multi-layered film were investigated by atomic force microscope (AFM) and X-ray diffraction as a function of film thickness of TiN layer.It was found that the SiO2 film was amorphous and both the Cu film and the TiN film had a strong {111} orientation. The two-exposure method was used to evaluate residual stress in the Cu and the TiN films by measuring lattice strains in two directions determined by crystal orientation. The Cu layer in Cu/TiN film had tensile residual stresses of 180-240MPa, and the Cu layer in SiO2/Cu/TiN film had slightly larger tensile residual stresses of 210-260MPa. These stresses in both films increased with the film thickness of the undercoated TiN layer. The TiN layer of Cu/TiN and SiO2/Cu/TiN had also tensile residual stress of 300 and 330MPa, respectively.

Synthesis and structure of smooth, superhard TiN/SiN x multilayer coatings with an equiaxed microstructure

TiN coatings have been widely used in various tribological applications. However, TiN coatings predominantly grow with a columnar grain structure, and these columnar grain boundaries become the sites for crack initiation, resulting in premature failure of TiN coatings. In this paper, we report the use of amorphous SiN x to periodically interrupt the growth of TiN in order to suppress the columnar structure. The growth was performed in a dual-cathode unbalanced reactive magnetron sputtering system. The resulting TiN/SiN x multilayer coatings, when deposited under optimum conditions (TiN layer thickness=2.0 nm, SiN x layer thickness=0.5 nm and substrate bias=−80 to –90 V) are smooth and exhibit an equiaxed grain structure with no evidence of columnar growth. The highest hardness is in excess of 45 GPa.

Evolution of nanoscale texture in ultrathin TiN films

We investigate the evolution of texture and grain morphology in fine-grained TiN thin films using cross correlation of dark-field images obtained using annular objective apertures with radii that correspond to different low index TiN reflections. This technique enables parallel analyses of the orientations of thousands of grains, with a spatial resolution of order 10 nm. Preferred grain orientations were determined for 40 and 100 nm thick TiN layers grown on SiO2 by magnetically unbalanced reactive magnetron sputter deposition. We find that no single orientation is dominant in the 40 nm films but that a 〈100〉 texture has developed by the time these films reach 100 nm in thickness.

Numerical Analysis of the Effect of Coating Microstructure on Three-Dimensional Crack Propagation in the Coating Under Rolling Contact Fatigue Conditions

Hard protective coatings produced by the physical vapor deposition (PVD) processes can potentially be used to prevent rolling contact fatigue (RCF) failures in gears and rolling bearings. Although TiN appears to be an attractive material for such applications, the RCF performance of PVD TiN coatings is limited by their columnar microstructure. One possible solution is to use interlayers interrupting the column growth in TiN to achieve a more equiaxed grain morphology. In this paper, the effect of the coating layer structure on the propagation of a three-dimensional crack through the coating thickness is studied theoretically. Numerical simulations of both planar and kinked three-dimensional cracks under cyclic contact loading are performed using a new numerical approach recently developed by the authors, which is based on a combination of the fast Fourier transform (FFT) technique, the eigenstrain theory, and the conjugate gradient method. The simulation results indicate that high-endurance TiN-based coatings can in principle be produced by alternating relatively thick TiN layers with much thinner interlayers made of another material.

ガス窒化によりチタン基材に形成させた窒化チタン層の割れおよびはく離強度評価

Gas nitriding was applied to pure titanium specimens and the tensile tests were carried out on the specimens in order to evaluate the fracture strength and delamination strength of titanium nitride (TiN and Ti2N) layers. With increasing load, both the TiN and Ti2N layers were divided by parallel cracks repeatedly and only the TiN layer was delaminated after a large plastic deformation of substrate. The fracture strength of TiN layer was estimated by an extrapolation method from the relationship between inverse of crack intervals and nominal tensile stress. Interfacial fracture toughness between TiN and Ti2N layers was almost independent of nitriding temperature and nitriding time, and it slightly increased with increasing thickness of TiN layer.

Ａｌ／ＴｉＮ多層薄膜の微小押し込み硬さ試験によるエネルギー的解析

In order to discuss mechanisms of hardness enhancement of Al/TiN multilayered thin films, elastic and plastic deformation behaviors of the multilayered films have been investigated by using dissipated and elastic energies evaluated from a load-displacement curve of nanoindentation. The Al/TiN multilayered films were deposited by dc magnetron sputtering. Thickness of Al layers was varied from 3 to 100 nm, and that of TiN layers was varied from 16 to 500 nm in correspondence with the variation in the number of layers from 60 to 2. A hardness enhancement by up to 10% compared to a monolithic TiN film was observed for a 20-layerd film with an Al layer thickness of 10 nm and a TiN layer thickness of 50 nm. A minimum dissipated energy was observed for a film with Al layer thickness of 5 or 10 nm. In contrary, elastic energy showed a maximum for the film. The reduction in the dissipated energy for a film with a thin Al layer implies that the pinning effect for propagation of dislocations at an interface between Al and TiN layers suppresses plastic deformation, resulting in the enhancement in microhardness.

ホローカソード方式イオンプレーティング法で作製したＴｉ／ＴｉＮ多層皮膜の耐食・耐摩耗性

Attempts have been made to reveal a desirable design for a Ti/TiN multilayer as a protector for corrosion and wear at-tacks. Multilayers of Ti/TiN were deposited on two types of chromium molybdenum steels and on a high speed tool steel by switching on and off a reactive gas feed valve. Layer thicknesses were determined by scanning electron microscopy and also estimated from Ti depth profiles obtained by grow discharge atomic emission spectrometry (GD-AES). Corrosion resisitance was evaluated by two types of tests : one is the method where the coated steels were exposed to the gas generated through hydrolyzing a resin mixture of ABS and PVC at 443 K under a pressure of 2.87 MPa, and the other is the critical passivation current density method where a deaerated solution of 0.5 kmol/m3H2SO4-0.05 kmol/m3KSCN was used as an electrolyte. Ttribology tests were carried out under unlubricated conditions with a reciprocating type testing apparatus. Substrate current is a fairly useful indicator for precise control of layer thickness. GD-AES offers an exact estmation of layer thickness in the matter of minutes, for example, only within 0.4 ks for a multilayer of 56 μm in total thickness. Corrosion tests show that TiN coatings with a thicker Ti underlayer are more protective and that the multilayer coatings possess a better protective function when the ratio of cumulative thickness of Ti layers to that of TiN layers, ∑XTi to ∑XTiN, is within 1 to 2. It is possible that an increase in thickness of the outer TiN layer brings about reduction of protection performance. With an increase in intrinsic compressive stress in the TiN layer, abrasive damage progresses more rapidly toward a substrate. The Ti layer contacting to the outer TiN layer suppressed the progression; for multilayers, therefore decreasing the thickness of the outer TiN layer resulted in a decrease in wear loss.

Erosion and deposition during the sputter cleaning of substrates prior to the cathodic arc evaporation of transition metal nitride coatings

Reactive cathodic arc evaporation (CAE) is a physical vapour deposition technique employed to produce wear resistant coatings. The adhesion of the coating is improved if the substrate surface is sputter cleaned by running the arc in high vacuum with the substrate held at a rms bias of −1000 V prior to deposition of the coating. In this paper the erosion and deposition of material during the sputter cleaning process is examined using analytical electron microscopy on two different systems. Cr sputter cleaning of Ti results in the formation of a surface layer of thickness ∼20 nm at the surface. This layer is crystalline and has a graded composition with a high fraction of Cr at the vacuum surface and a high fraction of Ti at the substrate interface. There is also some penetration of Cr into the substrate. The material of the substrate is eroded at a rate ∼6 nm per Amp-h of cathode current. Ti sputter cleaning of an existing TiN coating, on the other hand, exhibits negligible erosion of the substrate but results in the deposition of a layer of α-Ti, the thickness of which is strongly dependent on the geometry of the system. The rapid variation of the thickness of the deposited Ti with the angle between the planes of the substrate and the cathode suggests that a plasma sheath does not form under these circumstances. A simple model of the ion trajectories is used to describe this variation of the Ti thickness. The presence of such a Ti layer has implications for the re-coating of tools with TiN. The variation of the thickness of the subsequent TiN layer on the substrate is much smaller.

Barrier properties of TiN/TiSi 2 bilayers formed by two-step rapid thermal conversion process for Cu diffusion barrier

TiN/TiSi 2 bilayers offering excellent stability as a barrier against Cu metallization have been made achievable through a two-step rapid thermal conversion process. TiN/TiSi 2 bilayers are formed on single-crystalline Si substrates by the thermal conversion of Ti films in an ammonia ambient, using a rapid thermal process with a sequential two-step temperature cycle. In the thermal conversion process, the first-step is conducted in a low-temperature range, to minimize Ti/Si interaction, while maintaining reasonable interaction of Ti/NH 3 and vigorous nitrogen diffusion through the Ti layer, to maximize the thickness of the TiN layer. Then, the second step is carried out at a relatively high temperature, to reduce Ti/Si interaction in the silicidation process. The TiN/TiSi 2 bilayers show excellent diffusion barriers between Cu and single-crystal Si up to the annealing condition, 800°C for 90 s; and the Cu film improve in quality by resulting from grain growth in a decrease of about 20% in sheet resistance. From the XRD results, only variation of peak intensities was observed due to grain growth of the Cu film for the 850°C annealed samples. Also, there was no evidence of Cu diffusion through TiN for the 850°C annealed samples on the Auger and RBS results. It seems that enhanced barrier property of the Cu/TiN/TiSi 2 stack is due to the thick TiN layer and the suppression of Ti-oxide formation by the low-temperature nitridation in the first step.

The processing and testing of new and advanced materials for wear resistant surface coatings

In the search of wear resistant coatings for applications such as cutting tools and turbine refurbishing, we have produced and tested a wide range of coatings including nanocrystalline metals (At, Ti, Cu), nanolaminated composites, containing alternating layers of metal-ceramic (Al 2O 3 and Ti/TiN) or metal-metal (Ti/Cu), and monolithic coatings (TiN). These coatings were produced using an r.f. magnetron sputtering system except for the monolithic TiN which was commercially produced using an ion plating system. All these coatings were tested for their tribological (friction and wear) and mechanical (hardness) properties using a pin-on-disc type wear rig and an ultra-microindentation system, respectively. The tribological properties that were used to compare the relative performance of these materials were the coefficients of friction (both peak and steady-state) and the wear rates (volume loss per unit sliding distance) in both the severe and mild wear regimes. The optimum combination of a low coefficient of friction and low wear rate in the steady-state regime was exhibited by Ti/TiN nanolaminated composite coating with a 150 nm Ti layer thickness and a 20 nm TiN layer thickness. This material also exhibited the highest hardness of the composite coatings. The micromechanisms responsible for the differences in hardness and wear resistance of these materials are discussed and recommendations are made on future directions for producing improved wear resistant coatings.

Interfacial structure and reaction mechanism of AlN/Ti joints

Bonding of AlN to Ti was performed at high temperatures in vacuum. The bonding temperature ranged from 1323 to 1473 K, while the bonding time varied from 7.2 up to 72 ks. The reaction products were examined using elemental analysis and X-ray diffraction. TiN, Ti3AlN (τ1), and Ti3Al were observed at the AlN/Ti interface, having various thickness at different bonding conditions. The thickness of TiN and Ti3AlN layers grew slowly with bonding time. On the other hand, growth of the Ti3Al layer followed Fick’s law. The activation energy of its growth was found to be 146 kJ mol-1. When thinner Ti foil (20 μm) was joined to AlN at 1473 K for a long time (39.6 ks), the Ti central layer has completely consumed and another ternary compound Ti2AlN(τ2) started to form. A maximum bond strength was achieved for an AlN/Ti (20 μm) joint made at 1473 K for 28.8 ks, after which the bond strength of the joint deteriorated severely.

Multiwavelength ellipsometry for real-time process control of the plasma etching of patterned samples

We present a quantitative model to understand the ellipsometry traces recorded while etching patterned wafers in a high-density plasma reactor. This model allows one to determine the real-time thickness of a film as it etches, and data are presented showing the real-time thickness of TiN and polysilicon layers while etching. The model is generic to the film type and can be applied to any arbitrary stack of materials. Knowing the thickness in real time allows greater process control, as it enables one to stop or change the process at a specified remaining film thickness. The model is essentially geometric and does not include the effect of diffraction. It has been applied successfully to many samples, each with different integrated circuit layouts. The results are in good agreement with scanning electron microscopy measurements.

Dielectric Degradation of Cu/ SiO2/Si Structure during Thermal Annealing

The impact of Cu on the dielectric layer was studied using a Cu//Si metal oxide semiconductor capacitor and rapid thermal annealing (RTA) treatment. With the RTA treatment, no chemical reaction was observed up to 900°C; however, dielectric degradation occurred following RTA at 300°C for 60 s and became worse with the increase of annealing temperature. The interface‐trap density at the /Si interface also increased from 5 × 1010 to after 800°C RTA treatment. The RTA anneal introduced a large number of positive Cu ions into the dielectric layer. Under bias‐temperature stress, Cu ions drift quickly in the layer and may drift across the /Si interface and enter the Si substrate. With the use of 1200 Å thick TiN and TiW barrier layers, respectively, the dielectric strength of the Cu/(barrier)//Si structures was able to remain stable up to 500 and 600°C.

Characterization of TiN/TiSi2 bilayer formed by sputter deposition from a TiN0.4 alloy target and subsequent lamp annealing and its application to a contact system

AbstractTo develop a thermally stable barrier metal for interconnections in LSI, films deposited by sputtering a Ti‐rich TiN0.4 target were investigated (in what follows, the film deposited in this manner will be referred to as TiN0.4). Both film quality and the electrical property of the Al‐alloy/Si contact with thin barrier metal were evaluated. It was found that the TiN layer formed by this method was twice as thick as the TiN layer formed by the conventional method, the TiN/TiSi2 layer formed was smooth and the silicide layer was five times thinner than when the conventional method was used. The TiN layer formed by nitridation of TiN0.4 (50 nm)/Si had a grain structure with a grain size of approximately 10 nm and was strongly oriented to TiN (200). In the silicide layer, the grain size was approximately 50 nm and a semistable phase was formed. It was also found that contact resistance to N+Si was similar to that formed by using the conventional Ti nitridation method while the contact resistance to P+Si was slightly lower than when the conventional method was used. In addition, it was found that the contact resistance became lowest when the rapid thermal nitridation (RTN) temperature was approximately 700°C and the formed film was stable when it was thermally treated. When a Ti layer was used, the N+/P junction showed a leakage problem after it was annealed at temperatures higher than 450°C. However, when TiN0.4 was used, no leakage problem was observed even when the junction was annealed at 525 °C. These superior junction characteristics were due to the thermally stable and thick TiN layer.

Plasma surface treatment and PACVD on Ti alloys for surgical implants

To improve the poor surface hardness and wear resistance of titanium alloys used for surgical implants undergoing wear TiA16V4 and TiA15Fe2.5 have been plasma nitrided. TiN and other sublayers are formed by plasma nitriding. To increase the thickness of the outermost TiN layer the samples have been coated with TiN by PACVD following plasma nitriding. The produced layers have been characterized in terms of microstructure, layer composition, hardness depth profiles. The evaluation of corrosion resistance and biocompatibility revealed that the good properties of the untreated alloys have been well preserved.

Thickness measurement of titanium nitride layers on steel using PIXE and proton backscattering

RBS, PES (proton enhanced scattering) and PIXE were used to measure the thickness of TiN layers deposited on steel by plasma vapour deposition. Backscattering data were treated using RUMP with modified cross sections; PIXE data were treated by an extension of GUPIX which handles multilayer specimens. Agreement at the level of a few percent was obtained for thicknesses in the range of 1–5 μm.

Analysis of the tribological behaviour and wear mechanisms of titanium nitride coating

Experiments were conducted on a test machine that used a thrust-washer adapter, where a rotating upper specimen was pressed against a stationary lower specimen. This setup was used to simulate the surface contacts between the steel (of the ring) and the titanium nitride coating (on the washer). Further, the existence of an electroless nickel interlayer on the washer was also investigated. The effect of the coating layers on tribological behaviour was evaluated for different thickness combinations of the titanium nitride layer (top layer) and the electroless nickel layer (interlayer). The interlayer was found to increase the wear volume, but was advantageous for strengthening resistance against chemical corrosion. The wear volume was controlled by the thickness of the two coating layers. A thicker TiN layer in conjunction with a thinner interlayer constituted the appropriate combination for two coating layers from the viewpoint of lowering wear volume. The friction coefficients arising from the TiN coating generally varied in the narrow range between 0.5 and 0.55, regardless of the interlayer thickness. Both the friction coefficient and wear volume were affected very much by the applied load and sliding speed. In the testing operating conditions, the primary wear mechanisms of the coating layers, such as microabrasion, semicircular or curved cracking, plucking and grooving, formed the surface failures. The surface failures due to friction and wear that occurred within the top layer appeared to be nearly independent of the adhesive strength of the interface.

Heterointerfaces of CdTe/α-Sn /InSb structure grown by molecular beam epitaxy

A CdTe/α-Sn heterostructure has been grown on an InSb(100) substrate by molecular beam epitaxy at temperatures of 150 and 220°C. The α-Sn layers were grown up to thicknesses of 64 and 38 Å, respectively, assisted by the stabilizing effect, which prevents the α-Sn to β-Sn transition which normally occurs at 13.2°C. Here we report a transmission electron microscopy study which indicates the blocking of planar defects at the interface of α-Sn and InSb, suppressing their propagation to the CdTe overlayer. However, by Raman spectroscopy, the peaks of In, Te-related compounds can be seen for every thickness of grey tin layers. This indicates that the interdiffussion of In and Te could not be prevented by the grey tin layer. However, we cannot deny the possibility of suppression of interdiffusion, because it depends upon the quality of the grey tin layer.

Interfacial reactions in single-crystal-TiN (100)/Al/polycrystalline-TiN multilayer thin films

The thermal stability of Al/polycrystalline-TiN and Al/single-crystal-TiN couples was investigated using Auger electron spectroscopy (AES) and cross-sectional transmission electron microscopy (XTEM) with energy-dispersive X-ray spectroscopy (EDX). The trilayer samples consisted of a 100 nm thick epitaxial TiN layer grown on MgO(100) substrates, a 100 nm thick aluminium layer, and a 100 nm thick polycrystalline TiN layer. The multilayer films were grown in a dual-magnetron sputter-deposition system and then annealed in a reducing atmosphere at temperatures between 500 and 600 °C for up to 90 min. AES and EDX showed extensive penetration of titanium into the aluminum layer, but only limited interdiffusion of aluminum into both single-crystal and polycrystalline TiN. However, aluminum segregation occurred at both Al/TiN interfaces. XTEM examination revealed the formation of the ordered aluminum-rich AlTi intermetallic compoundssuch as Al 3Ti in the aluminum layer, while cubic-structure AIN formed at the AlTiN interfaces. Only small differences were observed in the reaction paths and product formation rates of Al/polycrystalline-TiN and Al/single-crystal-TiN couples. AlTi intermetallic compounds formed more rapidly in the former while AIN formation proceeded more rapidly at the Al/single-crystal-TiN interface.