Stress In TiN Research Articles

INFLUENCE OF BIAS POTENTIAL AND SUBSTRATE ORIENTATION ON CHARACTERISTICS OF DEPOSITED COATING: THE ROLE OF SPUTTERING

Influence of atomic sputtering on intrinsic stress and growth rate of the coating made by method of plasma - ion deposition with use of pulsed bias potential and at different incidence angles of ions is theoretically investigated. The formula for intrinsic stress calculation in deposited coating obtained in the model of the nonlocal thermoelastic peak of the ion, taking into account atomic sputtering processes, was used to calculate the stresses in TiN and CrN coatings deposited from Ti+ and Cr+ ion beams, respectively. The stress value for the coatings considered correlates with the modulus of elasticity of the coating material. The stress curve maximum decreases and shifts to the region of higher potentials with increasing angle of incidence. This behavior is due to the sputtering of quasi-stable interstitial defects that determine the level of stress in the deposited coating. A formula is proposed for the coating deposition rate, which takes into account the sputtering of the coating atoms at arbitrary bias potential and the angle of incidence of the ions. It is shown that sputtering sharply reduces the coatings deposition rate and makes it impossible to deposit TiN and CrN coatings in the DC mode at potentials on the substrate exceeding 1.7 kV and 0.7 kV, respectively, and with normal ion incidence. Sputtering has the greatest influence on the intrinsic stress and the growth rate of the coating at ion deposition at inclined angles of incidence α = 45°...70° . The results of the calculations are compared with the available experimental data.

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.

Quantification of dislocation nucleation stress in TiN through high-resolution in situ indentation experiments and first principles calculations.

Through in situ indentation of TiN in a high-resolution transmission electron microscope, the nucleation of full as well as partial dislocations has been observed from {001} and {111} surfaces, respectively. The critical elastic strains associated with the nucleation of the dislocations were analyzed from the recorded atomic displacements, and the nucleation stresses corresponding to the measured critical strains were computed using density functional theory. The resolved shear stress was estimated to be 13.8 GPa for the partial dislocation 1/6 <110> {111} and 6.7 GPa for the full dislocation ½ <110> {110}. Such an approach of quantifying nucleation stresses for defects via in situ high-resolution experiment coupled with density functional theory calculation may be applied to other unit processes.

Interfacial coherency stress distribution in TiN/AlN bilayer and multilayer films studied by FEM analysis

The development of interfacial coherency stresses in TiN/AlN bilayer and multilayer films was investigated by finite element method (ABAQUS) using the four-node bilinear quadrilateral axisymmetric element CAX4R. The TiN and AlN layers are always in compression and tension at the interface, respectively, as may be expected from the fact TiN has larger lattice parameter than AlN. Both, the bi-layer and the multilayer stacks bend due to the coherency stresses. For the TiN/AlN bilayer system, the curvature of the bending is largest for the TiN/AlN thickness ratios ∼0.5 and ∼2 (at which one of the two layers is fully in compression or tension), while it is smaller for the layers with the same thickness (at which both layers posses regions with compressive as well as tensile stresses). This stress distribution over the bi-layer thickness is shown to be strongly influenced by the presence and the properties of a substrate.Furthermore, the coherency stress profile and specimen curvature of a TiN/AlN multilayer system was studied as a function of the top-most layer thickness. The curvature is maximum for equal number of TiN and AlN layers, and decreases with increasing the number of TiN/AlN periods. Within the growth of an additional TiN/AlN bilayer, the curvature first decreases to zero for a vertically symmetrical geometry over the layers when the TiN layer growth is finished (e.g. for (n+1) layers of TiN and n layers of AlN). At this stage, the coherency stresses in TiN and AlN are same in each layer type (independent on the layer position). The growth of the second half of the TiN/AlN bi-layer (i.e. the AlN) to finish the period, again bends the specimen, and generates a non-uniform stress distribution. This suggests that the top layer as well as the overall specimen geometry plays a critical role on the actual coherency stress profile.

Residual stresses in TiN, DLC and MoS 2 coated surfaces with regard to their tribological fracture behaviour

Thin hard coatings on components and tools are used increasingly due to the rapid development in deposition techniques, tribological performance and application skills. The residual stresses in a coated surface are crucial for its tribological performance. Compressive residual stresses in PVD deposited TiN and DLC coatings were measured to be in the range of 0.03–4 GPa on steel substrate and 0.1–1.3 GPa on silicon. MoS 2 coatings had tensional stresses in the range of 0.8–1.3 on steel and 0.16 GPa compressive stresses on silicon. The fracture pattern of coatings deposited on steel substrate were analysed both in bend testing and scratch testing. A micro-scale finite element method (FEM) modelling and stress simulation of a 2 μm TiN-coated steel surface was carried out and showed a reduction of the generated tensile buckling stresses in front of the sliding tip when compressive residual stresses of 1 GPa were included in the model. However, this reduction is not similarly observed in the scratch groove behind the tip, possibly due to sliding contact-induced stress relaxation. Scratch and bending tests allowed calculation of the fracture toughness of the three coated surfaces, based on both empirical crack pattern observations and FEM stress calculation, which resulted in highest values for TiN coating followed by MoS 2 and DLC coatings, being K C = 4–11, about 2, and 1–2 MPa m 1/2, respectively. Higher compressive residual stresses in the coating and higher elastic modulus of the coating correlated to increased fracture toughness of the coated surface.

Analysis of thermal stress in magnetron sputtered TiN coating by finite element method

The thermal stress generated in the sputter deposited TiN coating on glass and silicon substrates was investigated by finite element analysis (ANSYS). The four-node structural and quadratic element PLANE 42 with axisymmetric option were used to model the thermal stress induced in the TiN coating. The influence of substrate temperature, Young’s modulus, substrate and coating properties on thermal stress were analyzed. It was found that the thermal stress in TiN coating, for the planar substrate, exhibits a linear relationship with substrate temperature, substrate thickness and Young’s modulus of the coating, but showed an inverse relationship with the coating thickness. The simulated thermal stress of TiN coating was in tandem with the analytical method. The thermal stress induced in the coatings for the rough substrate is higher as compared to that of the planar substrate. The radial stress and shear stress distribution of the coating–substrate combination were calculated. The low and high compressive shear stresses observed in the TiN coating on glass and Si substrate, respectively indicate a low adhesive strength of the coating on the former than that of the latter.

Evaluation of internal stresses in TiN thin films by synchrotron radiation

Evaluation of internal stresses in TiN thin films by synchrotron radiation

836 シンクロトロン放射光を用いた多層膜の内部応力評価

Residual stresses in TiN and TiAlN films on steel substrate were investigated by the usual in-lab X-ray equipment and ultra high X-rays of synchrotron radiation. The specimens prepared in this study were single TiN films with different thickness on the stainless steel substrate and single-, double- and multi-layer TiN and TiAlN films deposited on high speed steel substrate by arc-ion plating. The minimum thickness available for the residual stress measurement was 0.8μm by in-lab equipment whereas below 0.1μm by synchrotron radiation. Extremely large compressive residual stresses were found in the films and the level of residual stress was almost constant regardless of the film thickness. Residual stresses in TiAlN films were more than twice larger than those in TiN films, resulting to reduce the average residual stress in the whole film system by making double- or multi-layer film construction comparing to that in the single TiAlN film.

Properties of Ti1−xSixNy films deposited by concurrent cathodic arc evaporation and magnetron sputtering

A new technique is described in the synthesis of thin films of Ti1−xSixNy based on the concurrent reactive deposition of Ti produced by a cathodic arc source and Si produced by a d.c. magnetron sputter source. The technique permits the controllable doping of TiN with silicon over the range of 1–16 at.%. The films were found to have a microhardness of 70 GPa with a compressive stress of 5.5 GPa when deposited with a magnetron power of 220 W and a bias voltage of −150 V, and a maximum hardness of 58 GPa and stress values of approximately 3.3 GPa when deposited using 280 W magnetron power and −50 V bias. The hardness and stress of TiN was found to be 26 and 3.5 GPa, respectively, when deposited in the absence of the magnetron.

An analysis of stress waves in 12Cr steel, Stellite 6B and TiN by liquid impact loading

This research placed emphasis on the computer simulated stress distribution on the surface and in the bulk of the materials which are subjected to the water impact causing erosion damage. The erosion damage was predicted by evaluating the spatial and temporal stress wave distribution generated by water impact pressure on 12Cr steel and Stellite 6B as steam turbine materials and TiN as a hard coating material. There were two distinctive stress wave behaviors. Firstly, the large tensile stress at the surface was developed by the Rayleigh wave component which appeared between the water drop and the Rayleigh wave front. After the Rayleigh wave detached from the water drop, the materials were in the tensile stress state which could be related to fracture initiation. Secondly, the largest tensile stress in the bulk was near the surface due to the Rayleigh wave generated at the surface and decreased due to the enlargement of wave front as the radial distance increased. Rayleigh wave's shape was broadened due to the difference between the contact point velocity and the wave front velocity, while its value decayed exponentially in the depth direction. Also, there may be a tendency to produce a circumferential crack by σ rr near the surface and a lateral crack by σ zz in the sub-surface. The tensile stresses in TiN were much lower than those in 12Cr steel and Stellite 6B due to its higher wave velocity.

1031 PVD 法により成膜した TiN 硬質被膜の残留応力の測定

1031 PVD 法により成膜した TiN 硬質被膜の残留応力の測定

Crack formation in TiN films deposited on Pa- n due to large thermal mismatch

Advanced metallization requires stringent demands on the properties of dielectric materials and the respective conducting metals used. These include low dielectric constant, negligible water take up, chemical inertness, low temperature deposition, as well as compatibility with current integrated circuits manufacturing, low resistivity, and high electromigration resistance. To meet future integration requirements, Pa- n as the low κ-dielectric material and silver or copper as the low resistive metals are being studied. The issues of metal diffusion and adhesion are important for successful operation and long-term reliability. The diffusion barrier, titanium nitride has been well studied and is an accepted material in current industrial manufacturing. In this study, TiN was deposited using DC magnetron sputtering to minimize the thermal budget constrains associated with Pa- n. In situ four-point probe analysis was used to measure the resistivity of TiN and to elucidate the discontinuity in the films during thermal annealing. In situ X-ray analysis was performed to determine the coefficient of linear thermal expansion, which was then used to determine thermal stresses in TiN and Pa- n films. During the annealing, the hard and brittle TiN film did not comply with ductile Pa- n due to the thermal mismatch. This large tensile stress opposes the pre-existing compressive stress present upon deposition, and eventually exceeds the TiN fracture strength at approximately 150°C resulting in crack formation.

High-temperature mechanical properties of hot-pressed TiN with fine grain size

Mechanical properties of fine-grained TiN were studied by compression tests at temperatures ranging from 1073–1823 K and strain rates from 2×10-5 to 5×10-3 s-1. The temperature dependence of maximum (fracture or peak) stress of TiN reveals three regions with different activation energy and strain-rate sensitivity. At lower temperatures, brittle fracture takes place without plastic deformation. Fracture stress is independent of temperature, and greater than 1 Gpa. In the intermediate temperature region, specimens fracture in a quasi-brittle manner after a few per cent plastic deformation. Fracture stress decreases above 1300 K (in the intermediate temperature region), due to the deformation-assisted fracture. TiN becomes fully ductile at further higher temperatures, at which five independent slip systems are available. This ductile to brittle transition characteristic of TiN is similar to MgO (ionic) but different from TiC (covalent), though all three materials take the same NaCl type of lattice structure. In the high-temperature region, the activation energy for plastic deformation is close to that for diffusion of nitrogen in TiN. Strain-rate sensitivity in this region is typical of superplasticity, suggesting the possibility of superplastic forming. © 1998 Chapman and Hall

Effects of Ti interlayer on the microstructure of ion-plated TiN coatings on AISI 304 stainless steel

The microstructure and chemistry of TiN coatings on AISI 304 stainless steel was analyzed by an energy filtering transmission electron microscope (TEM) equipped with an electron energy loss spectroscopy (EELS) detector. Two types of TiN-coated specimens, with and without a Ti interlayer, were prepared by a hollow cathode discharge ion plating coater. For the TiN directly coated on steel, it is found that the grain size, texture, and chemistry of the coating is thickness dependent. The large residual stresses in TiN caused the formation of dislocation networks and cell walls in the steel, and often resulted in early failure of the coating upon subsequent handling. Compared to the TiN–steel system, the introduction of a Ti interlayer between TiN and steel gives rise to the different results. The microstructure of TiN coatings with a Ti interlayer is mainly composed of columnar grains whose size is found to be relatively independent of coating thickness. Near the TiN–Ti interface, it is observed that many of the TiN grains grew out of the underlying Ti crystallites. Consequently, a very good epitaxial relation is established between TiN and Ti. The texture of the TiN coatings with a Ti interlayer, therefore, showed enhanced preferred orientation when approaching the TiN–Ti interface. From the calculation of the unrelaxed thermal stress based on a bilayer model, it is demonstrated that the presence of a Ti interlayer between TiN and steel can dramatically reduced the thermal stress in the TiN coating.

Formation Kinetics and Thin Film Stress of Tin Containing Intermetallic Compounds

AbstractThin film reactions and its influence on mechanical stress have been investigated in Cr/Cu/Sn and Cr/Ni/Sn multilayer structures. Thin film stresses of different intermetallic compounds in each material system were evaluated using substrate bending technique. Stress state in the thin film structures was round directly related to formation kinetics and thermal properties of intermetallics. In Cu-Sn system, a large internal stress increase in tension was generally observed after being heat treated at high temperatures. In Ni-Sn systems, formation of intermetallics is a relatively slow reaction at elevated temperatures as compared to that of Cu-Sn samples. Contrary to that of Cu-Sn system, formation of Ni-Sn intermetallics causes a decrease in stress in the thin film structure. The correlation of thin film stress state and the structure evolution at the interface is studied and discussed in details.