Stress In TiN Films Research Articles

Understanding the stress effect of TiN top electrode on ferroelectricity in Hf0.5Zr0.5O2 thin films

We conducted a comprehensive investigation on the influence of TiN thickness and stress on the ferroelectric properties of Hf0.5Zr0.5O2 thin films. TiN top electrode layers with varying thicknesses of 2, 5, 10, 30, 50, 75, and 100 nm were deposited and analyzed. It was observed that the in-plane tensile stress in TiN films increased with the thickness of the TiN top electrode. This is expected to elevate the tensile stress in the Hf0.5Zr0.5O2 film, consequently leading to an enhancement in ferroelectric polarization. However, the effect of stress on the ferroelectric behavior of Hf0.5Zr0.5O2 films exhibited distinct stages: improvement, saturation, and degradation. Our study presents novel findings revealing a saturation and degradation phenomenon of in-plane tensile stress on the ferroelectric properties of polycrystalline Hf0.5Zr0.5O2 films, thereby partially resolving the discrepancies between experimental observations and theoretical predictions. The observed phase transformation induced by tensile stress in Hf0.5Zr0.5O2 films played a crucial role in these effects. Furthermore, we found that the impact of the TiN top electrode thickness on other factors influencing ferroelectricity, such as grain size and oxygen vacancies, was negligible. These comprehensive results offer valuable insights into the influence of stress and TiN top electrode thickness on the ferroelectric behavior of Hf0.5Zr0.5O2 films.

Crystal orientation and residual stress in TiN film by synchrotron radiation

Abstract The residual stress in a TiN film, the thickness of which is less than 1 µm, deposited by arc ion plating was measured using the SPring-8 synchrotron radiation facility installed at Japan Synchrotron Radiation Research Institute (JASRI). Films thicker than 300 nm have a {111} texture, whereas those with a thickness of 100 nm have a relatively random orientation. Instead of the conventional laboratory X-ray equipment, ultrabright synchrotron radiation can be used to precisely measure the residual stress in thin films with a thickness of 100 to 800 nm. The residual stress in thicker TiN films is about 7 GPa in compression and it is not affected by the film thickness. The slightly small compressive stress in a film of 100 nm in thickness may be due to the different crystal orientations in the film.

Tuning the stress in TiN films by regulating the doubly charged ion fraction in a reactive HiPIMS discharge

In the present study, we investigate the impact of pulse power (Ppulse) on the ion flux and the properties of TiN films using reactive high-power impulse magnetron sputtering. Ppulse was adjusted in the range of 5–25 kW, while keeping the total average power constant through regulating the pulsing frequency. It is found that the required N2 flow, to produce stoichiometric TiN, decreases as Ppulse is increased, which is due to a decrease in the deposition rate. The plasma conditions when stoichiometric TiN is formed were investigated in detail. In situ ion mass spectrometry measurements of the ion energy distribution functions reveal two distinct ion populations, ions originating from sputtered atoms (Ti+, Ti2+, and N+) and ions originating from the working gas (Ar+, Ar2+, and N2+). The average ion energies (Eave) of the sputtered ions show an increase with increasing Ppulse, while Eave for the gas ions remains almost unaffected. The relative flux intensity Ti2+/Ti+ showed an increasing trend, from 0.28 to 0.47, as Ppulse was increased from 5 to 25 kW. The ion flux changes affect the growth of the TiN film such that 111-textured films are grown for low Ppulse while higher Ppulse results in mixed orientations. In addition, the hardness of the deposited film increases with increasing Ppulse, while the compressive film stress increases significantly at a higher Ppulse. In this way, optimum deposition conditions were identified at Ppulse = 8.3 kW, where a relatively low compressive stress of 0.89 GPa and high hardness of 22.67 GPa were measured.

Film thickness effect on texture and residual stress sign transition in sputtered TiN thin films

Abstract Residual stress in thin films and coatings strongly affects their properties and behavior in service. Comprehensive understanding and precise measurements of residual stress are prerequisites for preparing high quality films and coatings. Residual stresses in TiN films with different thickness were measured by X-ray diffraction (XRD) employing the cos 2 α sin 2 ψ method with certain optimization. Grazing incidence parallel beam optics was combined with side-inclination geometry using in-house designed sample stage to ensure results accuracy. To validate this method, TiN films with thickness ranging from 1 to 3 µm were deposited on (100) Si single crystal substrates at 300 °C by RF magnetron sputtering. High compressive −2 GPa residual stress was present in the 0.9 µm thick film and decreased with film thickness. Tensile stress of less than 0.3 GPa was present in 2 µm TiN film. Compressive-to-tensile residual stress transition was observed with the film thickness increase. Microstructure change with growth, annihilation of grain boudaries, atomic peening and recovery mechanisms are responsible for the reported stress sign transition.

High-Performance Metal Hard Mask Process Using Fiber-Textured TiN Film for Cu Interconnects

One of the most challenging issues in the metal hard mask process for copper interconnects is controlling the residual stress in TiN mask. The relationship between the residual stress and the feature size of the trench was investigated using a mechanical simulation. It was found that the trench deformation at a specific pattern due to the residual compressive stress in TiN film resulted in void formation in Cu. To overcome this problem, the correlation between the residual stress and the film properties of TiN was investigated and a potential TiN mask in the metal hard mask process was studied. The residual stress in TiN film and the etching performance were correlated with the composition and the crystal structure of TiN. The grain growth was suppressed by reducing the energy of sputtered atoms during the deposition of TiN, resulting in low residual stress in TiN film with keeping the etching performance for TiN. By applying low stress TiN mask which had a fiber-textured structure, the trench deformation at a specific pattern could be suppressed and thus Cu filling was perfectly achieved. The metal hard mask process using TiN film which had a fiber-textured structure was demonstrated to be high performance.

Numerical Simulation and Response Analysis of Residual Stress Induced by Micro-Scale Laser Shock Peening in TiN Film

The ABAQUS software was used to analyze the residual stress of TiN film treated by the single point micro-scale laser shock peening (μLSP). In view of the multi-factor effect of μLSP, the response surface methodology (RSM) of Design-Expert software was utilized to analyze the influence of laser process parameters on the residual stress in TiN film, based on the Box-Behnken experimental design methods, as a result, optimal combination of the laser process parameters was obtained. The results showed that μLSP can transform the tensile residual stress in the TiN film into the compressive residual stress, the compressive residual stress was gradually increasing with the increased laser power density, when the laser power density was 8 GW/cm2, the maximum compressive residual stress of the film surface was up to -350.48 MPa. In addition, as the laser power density increased, the maximum compressive residual stress was moving away from the spot center. The optimal combination of the laser process parameters of μLSP was obtained by the RSM, the laser power density was 7.6 GW/cm2, laser spot diameter was 283 μm, and the number of shocking was 2 times. Simulation results of the average residual stress was -248.76 MPa, while the predicting result of regression model was -245.31 MPa, the error was just 1.38 %. The results showed that μLSP was feasible for improving the residual stress distribution of TiN film, and the RSM can effectively optimize the process parameters of μLSP.

Numerical Simulation and Response Analysis of Residual Stress Induced by Micro-Scale Laser Shock Peening in TiN Film

The ABAQUS software was used to analyze the residual stress of TiN film treated by the single point micro-scale laser shock peening (μLSP). In view of the multi-factor effect of μLSP, the response surface methodology (RSM) of Design-Expert software was utilized to analyze the influence of laser process parameters on the residual stress in TiN film, based on the Box-Behnken experimental design methods, as a result, optimal combination of the laser process parameters was obtained. The results showed that μLSP can transform the tensile residual stress in the TiN film into the compressive residual stress, the compressive residual stress was gradually increasing with the increased laser power density, when the laser power density was 8 GW/cm2, the maximum compressive residual stress of the film surface was up to -350.48 MPa. In addition, as the laser power density increased, the maximum compressive residual stress was moving away from the spot center. The optimal combination of the laser process parameters of μLSP was obtained by the RSM, the laser power density was 7.6 GW/cm2, laser spot diameter was 283 μm, and the number of shocking was 2 times. Simulation results of the average residual stress was -248.76 MPa, while the predicting result of regression model was -245.31 MPa, the error was just 1.38 %. The results showed that μLSP was feasible for improving the residual stress distribution of TiN film, and the RSM can effectively optimize the process parameters of μLSP.

Changes of internal stress and microstructure in spontaneous tin whisker growth

Tin thin films with various thicknesses were electrodeposited on Cu substrate with and without Ni undercoat. The changes of the internal stresses in tin films were measured by the X-ray diffractions. For the case of 2.2 μm thick film without Ni undercoat, the initial internal stress was tension and then gradually changed into compression. After 20 h, the internal compressive stress became around −30 MPa and was remained constant afterward. Filament-type whiskers were formed on the surface after the stress changed into compression. For the case of 2.2 μm thick film with Ni undercoat, the stress maintained in tension and no whisker was observed. For the cases of thicker films with and without Ni undercoat, the stress was compression around −30 MPa just after deposition, and remained constant. Nodule-type and Mount-type whiskers were formed on the surface, but no Filament-type whiskers were observed. The compressive stress applied by bending on 2.2 μm thick film with Ni undercoat resulted in the formation of Mount-type whiskers. The postbake process induced the tensile stresses in 2.2 and 16.5 μm thick films. Whisker formation was prevented in thin film and only Mount-type whiskers were formed in thicker films.

Effect of heating on the residual stresses in TiN films investigated using synchrotron radiation

The structure and residual stresses of TiN films deposited by arc ion plating (AIP) on a steel substrate were investigated using a synchrotron radiation system that emits ultra-intense X-rays. In a previous study, the crystal structures of TiN films deposited by AIP were found to be strongly influenced by the bias voltage. When high bias voltages were used, TiN films that were approximately 200 nm thickness had a preferred orientation of {110}, whereas TiN films that were approximately 600 nm thickness has a multilayer film orientation of {111}/{110}. In this present study, the two-tilt method was used to evaluate the residual stresses in TiN films by measuring lattice strains in two directions determined by the crystal orientation. Residual stresses in 600-nm-thick as-deposited TiN films were found to be −10.0 GPa and −8.0 GPa for {111}- and {110}-textured layers, respectively, while they were −8.0 GPa for {110}-textured layers in 200-nm-thick as-deposited TiN films. Residual stresses of both films relaxed to thermal stress levels upon annealing.

Stress reduction during phase change in Ge2Sb2Te5 by capping TiN film

It has been one of the most important issues to minimize the stress reduction during phase change in GST (Ge2Sb2Te5) alloy for PRAM (Phase-change Random Access Memory) applications, because the alloy has been reported to face the significant stress during the phase change. We fabricated GST/oxide/substrate as a basic structure, and then added two more structures by capping an adhesion layer (Ti) or a barrier metal (TiN) on GST layer, respectively. We report that TiN-capped structure shows about 40% stress reduction during the phase change compared with that of the basic structure. The stress reduction is considered to be due to the intrinsic compressive stress in TiN film itself.

Thermal relaxation of residual stresses in TiN films deposited by arc ion plating

Abstract The present study investigates crystal orientations and residual stresses in TiN films deposited by arc ion plating. TiN films approximately 2.0 μm thick were deposited on a steel substrate. With a bias voltage of 0 V, the TiN film exhibited strong {110} texture, whereas the dominant orientation of the film deposited at −100V was {111}. TiN films had very high compressive residual stresses: −8.6 GPa in the {110} textured film and −10.0 GPa in the {111} textured film. These residual stresses decreased with increasing annealing temperature and the reduction rate was greater for the {111} than for the {100} film. The behavior of residual stresses in the {111} and {110} textured layers of {111}/{110} textured double-layer film was identical to that for single-layer films.

Experimental and numerical evaluations of adhesion strength and stress in TiN films deposited on ti-implanted aluminum

Titanium ions were implanted into aluminum substrates at 40kV prior to magnetron sputtering deposition of the Ti interlayer and TiN film using our custom-designed multifunctional ion implanter without breaking vacuum. An 82-nm-thick modified layer was formed between the TiN film and the substrate. The characteristics of the implanted samples were compared to those of TiN∕Al and TiN∕Ti∕Al samples that were not preimplanted. Based on our scratch tests, the critical loading Lc of the TiN∕Ti∕Ti-implanted Al sample was significantly improved compared to the unimplanted TiN∕Al and TiN∕Ti∕Al samples. Finite element analysis was conducted to simulate the scratch process to help reveal the stress distributions in the vicinity of the interlayer. The results show that the stress around the interface is largely reduced in the TiN∕Ti∕Ti-implanted Al sample. Consequently, the mechanical properties such as resistance to loadings are enhanced.

Evaluation of internal stresses in TiN thin films by synchrotron radiation

Residual stresses in TiN films on a steel substrate were investigated with ordinary in-lab X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. Specimens prepared in this study were TiN films with different thicknesses deposited on a stainless-steel substrate by arc-ion plating. The minimum thickness that allows the residual stress measurement was 0.8 μm by in-lab equipment, but it was below 0.1 μm by synchrotron radiation. We found extremely large compressive residual stresses even in a 0.1-μm-thick film; the level of residual stress was almost constant for the films with thickness of 0.1 to 0.8 μm.

Deposition pressure dependence of internal stress in TiN films deposited by filtered cathodic vacuum arc

TiN films were deposited by an off-plane double bend filtered cathodic vacuum arc technique. The composition, structure, and surface morphology of the films were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, and atomic force microscopy, respectively. Internal stress was determined by a substrate bending method. The influence of the deposition pressure on the composition, structure, and internal stress of the films was studied systematically. At a deposition pressure of 1×10−5 Torr, the films are composed of single α-TiN0.30 phase with fairly low internal stress, and the atomic ratio of N to Ti is 0.32. As the deposition pressure increases to 5×10−5 Torr, the N/Ti ratio increases to 0.56, and the films are composed of a mixture of hexagonal α-TiN0.30 and cubic TiN0.90. The formation of TiN0.90 phase and the mismatch of these two kinds of phases contribute to a dramatic increase of internal stress in the films. The increase of deposition pressure to 2×10−4 Torr results in the formation of stoichiometric TiN films with single TiN phase, which corresponds to slightly lower internal stress. However, a further increase of deposition pressure results in a continuous increase in the N/Ti ratio and the formation of overstoichiometric films. The incorporation of excess N atoms in the films accounts for the further increase of internal stress.

Crystal orientation and residual stress in TiN film by synchrotron radiation

Abstract The residual stress in a TiN film, the thickness of which is less than 1 mm, deposited by arc ion plating was measured using the SPring-8 synchrotron radiation facility installed at Japan Synchrotron Radiation Research Institute (JASRI). Films thicker than 300 nm have a {111} texture, whereas those with a thickness of 100 nm have a relatively random orientation. Instead of the conventional laboratory X-ray equipment, ultrabright synchrotron radiation can be used to precisely measure the residual stress in thin films with a thickness of 100 to 800 nm. The residual stress in thicker TiN films is about 7 GPa in compression and it is not affected by the film thickness. The slightly small compressive stress in a film of 100 nm in thickness may be due to the different crystal orientations in the film.

Production and structural characterization of BN/TiN multilayers

A pulsed excimer laser was used to evaporate targets of boron nitride and titanium nitride in an attempt to produce hard thin films on crystalline silicon substrates. The films were either pure TiN or BN layers, as well as alternating multilayers and mixed layers. Deposition could be assisted by ion bombardment. The films were characterized by Auger electron spectroscopy, Fourier transform infrared spectroscopy (FTIR), and x-ray diffraction. A selection of films was also studied by profilometry in order to determine deposition rate and the type of stress present. The level of stress in TiN films was also a function of the deposition temperature and could be varied with the use of ion bombardment. Amorphous, cubic, and hexagonal BN films were produced and the effect of the stress of the substrate on these layers was investigated. Multilayers were stressed, having alternating layers of nanocrystalline TiN and amorphous BN. Mixtures consisted of nanometer-sized regions of crystalline TiN and sp2 coordinated boron nitride. FTIR spectra and high-resolution transmission electron microscope pictures suggested that in the mixtures, boron nitride planes tended to parallel the surface of the TiN grains. No sign of stress-driven formation of cubic BN was observed in the multilayers nor in the nanosized mixtures, regardless of the stress level present in them; neither was there any sign of titanium borides or other structures that might increase the hardness of the films.

ＴｉＮ膜の膜内残留応力に及ぼす基材溶対処理の影響

A fundamental study on the effect that pre-coating a substrate with metal spraying has on the properties of sputtered Titanium-nitride film (TiN film) was carried out. The residual stresses in TiN films sputtered on the substrates coated with various spray coatings were measured by X-ray stress measurement. It was observed that the residual stresses in TiN films sputtered on substrates coated by metal spraying were lower than those on the substrates not so coated. The influence of the surface configuration of spray coating on the residual stress in sputtered TiN film was also investigated. It was found that the surface configuration of spray coating affected the residual stress in TiN film, and that the residual stress increased with the surface roughness of the spray coating increasing.

401 <110> 繊維配向した TiN 薄膜の力学特性の X 線的研究

The residual stress in TiN film was measured by the X-ray method. TiN film was deposited on steel substrate by ion beam mixing method and the thickness was 1μm. The residual stress in TiN film was equi-biaxial and the value was about -5.5GPa compression. When uniaxial tensile loading was applied to the substrate, the stress in the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. The result agreed well with the prediction. When the measured stress in the film becomes tension, the stress stop increasing even though the applied strain keep increasing. This leveling of the stress was caused by cracking of the film.

Residual stress in TiN film deposited by arc ion plating

TiN films were deposited on aluminum and stainless steel substrates by arc ion plating (AIP). Bias voltages, nitrogen gas pressures and arc currents were changed to examine their role on the hardness and residual stress of a TiN film. Vickers microhardness tests revealed high hardness value (HV = 2250–2500) which depends on both nitrogen gas pressures and arc currents. From the X-ray diffraction pattern, it was found that the crystal orientation of the TiN film markedly varied with the bias voltage. Residual stresses in the TiN film were measured by the two-exposure X-ray stress analysis as a function of the nitrogen gas pressure, arc current. Very high compressive residual stresses, −5 GPa in the films on aluminum substrates and −7 GPa in the film on a stainless steel substrate, were observed.

Plasma deposition of tribological and optical thin film materials with a filtered cathodic arc source

Abstract The recent development of the filtered arc deposition method (FAD) has shown that hard, wear-resistant materials can be deposited free of cathode microdroplets and with exceptional smoothness and reproducible properties. The microhardness and stress of TiN films are determined by the bias applied to the substrate during growth. Microhardness values have been measured over the range of 2000–3000 Hv. The absence of particulates in the deposited films renders the technique suitable for the preparation of high-quality optical dielectric oxide and metallic films on to ambient temperature substrates. Films of amorphous TiO 2 with refractive indices of 2.45 at a wavelength of 600 nm can be easily prepared with a very low absorption. Optical-quality films of Nb 2 O 5 and Al 2 O 3 have also been prepared similarly by reactive deposition from pure Nb and Al cathodes. Smooth Au films with a high reflectivity are also deposited by the FAD process.