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Considering the application of titanium nitride (TiN) films as a release layer in producing Wolter-I X-ray telescope mirror shells by the electroformed nickel replication (ENR) technique, this research pays attention to the influence of nanometer-scale thickness variation in the microstructure and physical properties of TiN films deposited by the pulsed direct current (DC) magnetron sputtering method. This topic has received limited attention in the existing literature. TiN films (9.8 nm to 42.9 nm) were fabricated to comprehensively analyze the evolution in microstructure, depth distribution of elements, surface morphology, and intrinsic stress. With increasing thickness, TiN transitioned from amorphous to (200) and (111)–(200) mixed-oriented crystallization, explaining inflection points in the increasing roughness curve. Elements (C, N, O, Si, and Ti) and chemical bond proportions (Ti-N, Ti-N-O, and Ti-O) varied with film depth, and the fitting of film density can be optimized according to these variations. Crystallite size increased with thickness, which led to a reduction in intrinsic stress. It is evident that as film thickness increases, TiN forms a stable crystal structure, thereby reducing intrinsic stress, but resulting in increased roughness. Considering the impact of changes in thin film thickness on physical properties such as roughness, crystallinity, and intrinsic stress, a TiN film with a thickness of approximately 25 nm is deemed suitable for application as a release layer. [ABSTRACT FROM AUTHOR]

Understanding the origins of intrinsic stress in Si nanowires (NWs) is crucial for their successful utilization as transducer building blocks in next-generation, miniaturized sensors based on nanoelectromechanical systems (NEMS). With their small size leading to ultrahigh-resonance frequencies and extreme surface-to-volume ratios, silicon NWs raise new opportunities regarding sensitivity, precision, and speed in both physical and biochemical sensing. With silicon optoelectromechanical properties strongly dependent on the level of NW intrinsic stress, various studies have been devoted to the measurement of such stresses generated, for example, as a result of harsh fabrication processes. However, due to enormous NW surface area, even the native oxide that is conventionally considered as a benign surface condition can cause significant stresses. To address this issue, a combination of nanomechanical characterization and atomistic simulation approaches is developed. Relying only on low-temperature processes, the fabrication approach yields monolithic NWs with optimum boundary conditions, where NWs and support architecture are etched within the same silicon crystal. Resulting NWs are characterized by transmission electron microscopy and micro-Raman spectroscopy. The interpretation of results is carried out through molecular dynamics simulations with ReaxFF potential facilitating the incorporation of humidity and temperature, thereby providing a close replica of the actual oxidation environmentin contrast to previous dry oxidation or self-limiting thermal oxidation studies. As a result, consensus on significant intrinsic tensile stresses on the order of 100 MPa to 1 GPa was achieved as a function of NW critical dimension and aspect ratio. The understanding developed herein regarding the role of native oxide played in the generation of NW intrinsic stresses is important for the design and development of silicon-based NEMS. [ABSTRACT FROM AUTHOR]

Suppressing the open-circuit voltage deficit and residual stress caused by stubborn defects is crucial for achieving efficiency flexible Cu 2 ZnSn(S,Se) 4 solar cell coexisting with bending stability. The strategy of sputtering Sb 2 Se 3 layer in CZTS precursor followed by selenization is proposed to realize Sb doping in CZTSSe. Benefitting from the role of Sb doping in suppressing Sn Zn defects, improved mechanical flexibility with decreased porosity and released residual stress declining from −5.75 GPa to −3.45 GPa of CZTSSe absorber is achieved, which can effectively inhibit carrier recombination in CZTSSe/CdS heterojunctions during harsh bending environment. Consequently, an enhanced efficiency from 3.06 % to 4.63 % is achieved with the optimal Sb 2 Se 3 thickness of 80 nm, which can retain 90 % of its initial efficiency after harsh bending. The inspiring results provide a new route to stress regulation for flexible copper-based thin film solar cells. [ABSTRACT FROM AUTHOR]

Within the framework of the model of the nonlocal thermoelastic peak of low-energy ion, the formation of intrinsic stress in a carbon coating deposited from the vacuum arc plasma in the argon atmosphere is theoretically studied. It is shown that the flow of particles bombarding the deposited coating contains, along with C+ ions, also Ar+ ions involved in the formation of intrinsic stress in the coating. The flux density of Ar+ ions resulting from ionization losses of C+ ions passing through the argon atmosphere is proportional to both the flux density of C+ ions and the density (pressure) of argon. Expressions are obtained for the intrinsic stress in the deposited carbon coating depending on the bias potential on the substrate and the argon pressure for the cases of both constant and pulsed potentials. The analysis of the obtained expressions shows that the intrinsic stress in the carbon coating decrease with increasing argon pressure.

Boron as thin film material is of relevance for use in modern micro- and nano-fabrication technology. In this research boron thin films are realized by a number of physical and chemical deposition methods, including magnetron sputtering, electron-beam evaporation, plasma enhanced chemical vapor deposition (CVD), thermal/non-plasma CVD, remote plasma CVD and atmospheric pressure CVD. Various physical, mechanical and chemical characteristics of these boron thin films are investigated, i.e., deposition rate, uniformity, roughness, stress, composition, defectivity and chemical resistance. Boron films realized by plasma enhanced chemical vapor deposition (PECVD) are found to be inert for conventional wet chemical etchants and have the lowest amount of defects, which makes this the best candidate to be integrated into the micro-fabrication processes. By varying the deposition parameters in the PECVD process, the influences of plasma power, pressure and precursor inflow on the deposition rate and intrinsic stress are further explored. Utilization of PECVD boron films as hard mask for wet etching is demonstrated by means of patterning followed by selective structuring of the silicon substrate, which shows that PECVD boron thin films can be successfully applied for micro-fabrication. [ABSTRACT FROM AUTHOR]

At present, the power conversion efficiency of single-junction perovskite-based solar cells reaches over 26%. The further efficiency increase of perovskite-based optoelectronic devices is limited mainly by defects, causing the nonradiative recombination of charge carriers. To improve efficiency and ensure reproducible fabrication of high-quality layers, it is crucial to understand the perovskite nucleation and growth mechanism along with associated process control to reduce the defect density. In this study, we investigate the growth kinetics of a promising narrow bandgap perovskite, formamidinium methylammonium lead iodide (FAMAPbI 3 ), for high-performance single-junction solar cells. The temporal evolution of structural and optoelectronic properties during FAMAPbI 3 vacuum codeposition was inspected in real time by grazing-incidence wide-angle X-ray scattering and photoluminescence. Such a combination of analytical techniques unravels the evolution of intrinsic defect density and layer morphology correlated with lattice strain from the early stages of the perovskite deposition.

Micro-Electro-Mechanical Systems (MEMS) acoustic transducers are highly sophisticated devices with high sensing performance, small size, and low power consumption. To be applied in an implantable medical device, they require a customized packaging solution with a protecting shell, usually made from titanium (Ti), to fulfill biocompatibility and hermeticity requirements. To allow acoustic sound to be transferred between the surroundings and the hermetically sealed MEMS transducer, a compliant diaphragm element needs to be integrated into the protecting enclosure. In this paper, we present a novel fabrication technology for clamped micron-thick Ti diaphragms that can be applied on arbitrary 3D substrate geometry and hence directly integrated into the packaging structure. Stiffness measurements on various diaphragm samples illustrate that the technology enables a significant reduction of residual stress in the diaphragm developed during its deposition on a polymer sacrificial material.

In this work, Pb 1−3 x /2 La x ZrO 3 (x = 0–0.12) (PLZ- x) antiferroelectric thin films were fabricated on Pt(111)/TiO 2 /SiO 2 /Si substrates using chemical solution method. Smaller cations (La3+) and vacancies were introduced into A-sites of perovskite structure to construct chemical pressure. According to phenomenological theory, chemical pressure can increase the energy barrier between antiferroelectric (AFE) and ferroelectric (FE) phase, and enhance antiferroelectricity of the system. As a result, a large energy storage density (W re) of 23.1 J cm−3 and high efficiency (η) of 73% were obtained in PLZ-0.10 films, while PLZ-0 films displayed lower W re (15.1 J cm−3) and η (56%). More importantly, PLZ-0.10 films exhibited an excellent cycling stability with a variation of ˜2% after 1 × 108 cycles. The results demonstrate that heavily La-doped PbZrO 3 films with high energy storage density, high efficiency and excellent cycling stability can be considered as potential candidates for energy storage applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A formula for intrinsic stress in coating deposited from mixed ion beam is proposed. • Formula accounts for deposition temperature, it is valid in DC and pulse potential mode. • Stress calculation in Ti 1−x Al x N coating in DC and pulse potential mode is carried out. • Increase content of Al reduces stress in Ti 1−x Al x N coating deposited in pulse mode. Abstract The model of the nonlocal thermoelastic peak of low-energy ion is used in deriving an expression for intrinsic stress in multi-component material deposited from mixed beam of differently charged ions in modes of the direct current (DC) and pulsed bias potential. Calculation of intrinsic stress depending on bias potential in coating Ti 1−x Al x N deposited from mixed ion beam Ti + Al with different component ratio is executed in modes of DC and pulsed bias potential at different substrate temperatures. It is shown that the increase of the content x of Al ions in the mixed beam and in deposited Ti 1−x Al x N coating reduces the maximum of the stress curve σ(U). [ABSTRACT FROM AUTHOR]

We present technological issues in the deposition of diamond films on gallium nitride (GaN) membranes. Many wrinkles and thicker diamond layers were observed at the membrane center and poor quality diamond outside the membrane area. The deflection of the membranes was analyzed by a bulging method using white light interferometry. The membrane bending is discussed in the terms of temperature gradient and mismatch of thermal expansion coefficients of materials.

Zinc (Zn) is an essential micronutrient in organisms and an abundant element in the Earth's crust. Trace amounts of Zn released from natural sources can enter aquatic ecosystems through weathering and erosion. Zn accumulates in organisms, and when its intracellular concentration exceeds a certain level, it can induce oxidative stress and trigger oxidative stress-mediated heat shock protein (HSP) modulation. HSP70 is the most evolutionarily conserved among the HSP families. Despite extensive research on HSP70 genes in bivalves, the HSP70 gene family of Tegillarca granosa is still poorly characterized. We identified 65 HSP70 genes belonging to 6 families in the T. granosa genome, with 50 HSPa12 and 11 HSPa B2 genes highly expanded. On chromosome 11, 39 HSP70 (60%) genes were identified, and the HSPa12A genes were highly duplicated. A total of 527 and 538 differentially expressed genes were identified in the gills and mantle based on Zn exposure, respectively. The Gene Ontology of cellular anatomical entities was significantly enriched with upregulated differentially expressed genes in the gills and mantle. Eight of the 11 HSPa B2 genes were upregulated in both tissues. Most of the genes identified in both tissues were involved in "protein homeostasis" and "inhibition of apoptosis," which are associated with the HSP70 family's resistance to extrinsic and intrinsic stress. Hence, this study identified that the HSP70 gene family plays a vital role in the adaptation of aquatic organisms to heavy metal (e.g., Zn) stress in contaminated environments by compiling the different physiological responses to preserve homeostasis., Competing Interests: Declarations of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250°C and 550°C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed.

Abstract The growth rate and pressure dependence on the intrinsic stress in sputter deposited Cu thin films has been investigated and compared to a kinetic growth model, which contains both growth and energetic contributions to stress in its description. Since microstructure also has a strong effect on intrinsic growth stress, we have been able to systematically control a fixed grain size over multiple growth conditions spanning 0.012 nm/s to 2.4 nm/s deposition rates and 0.267 Pa to 2.667 Pa pressures using a seed layer prior to film deposition. At high deposition pressures, the stress became more tensile as the growth rate increased. In the low deposition pressure regime, the stress became more tensile with increases in deposition rate until a critical cross-over point where upon further increases in deposition rate resulted in the stress becoming more compressive. This cross-over has been explained in terms of the energetic contributions to the stress and the intrinsic high mobility of Cu to reveal this behavior. The fitting parameters and corresponding stress contributions from the kinetic model were extracted and compared to other films and deposition techniques. Though caution should be used in comparing absolute values, the kinetic model revealed the correct trends in predicting energetic trapping of defects between low and high mobility films as well as similar growth stress values, which are independent of energetic contributions, between sputtering and electrodeposition. These results suggest that the kinetic model shows promise in fitting different materials and deposition techniques intrinsic stress behavior. Highlights • A Cu seed layer limited grain size variation over varied deposition parameters. • Intrinsic growth stress exhibited growth rate dependent behavior. • The kinetic model of stress evolution fits well with high mobility sputtered Cu. [ABSTRACT FROM AUTHOR]

Abstract The effect of Ge alloying on the growth morphology and intrinsic stress evolution during deposition of Cu thin films is investigated using in situ and real time diagnostics, complemented by ex situ microstructural characterizations. Cu 1-x Ge x alloys with x up to 0.15 were sputter-deposited at room temperature on Si substrates, while measuring simultaneously the substrate curvature evolution and surface differential reflectance spectroscopy during the early stages of growth. All films exhibit a typical compressive-tensile-compressive stress behavior, which underpins the distinct stages of a Volmer-Weber growth mode; however, it is revealed that the Ge content plays a decisive role on the nucleation and coalescence stages. This results in a grain size refinement and development of higher compressive stresses for Ge solute additions up to x = 0.07. At higher Ge contents, the strong chemical affinity between Cu and Ge atoms leads to a germanide compound (Cu 5 Ge) formation and even higher compressive stress. The stress evolutions are discussed considering the surfactant character of Ge atoms affecting Cu adatom mobility and growth morphology. This study highlights the possibility to tailor the early stages of growth and film microstructure (grain size, texture, surface roughness) by introducing solute concentrations of Ge in Cu films. We also determined for the elemental Cu film the percolation and film continuity thicknesses and discussed theses values with respect to those reported for other metallic films. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A method of numerically estimating intrinsic stress has been developed for thin-film coatings of TiSiCN prepared by plasma enhanced magnetron sputtering at 280 °C. A portable optical setup was designed to be used with a commercial lab microscope, for taking measurements of the radii of curvature of the coated samples. The sensitivity of the optical instrument was optimized for taking measurements over a specific range of radii. A finite element model was developed in Abaqus to computationally determine the intrinsic and residual stresses in the thin films, with the help of the optical measurements. The computationally generated stresses and curvatures were found to agree well with previous analytical work. An average intrinsic stress of −2.49 GPa was observed for the thin-film samples. The stress relief in all the samples was calculated to be in the range of (20−30) %. Variations in the intrinsic and residual stress in the coatings indicate the possibility of a non-uniform deposition incidence based on their substrate positions. [ABSTRACT FROM AUTHOR]

Aerosol deposition is a kinetic energy, particle impacting process to produce dense ceramic films or coatings at room temperature, and thus results in high residual compressive stress. The purpose of this work was to determine the stress and its thickness dependence in titanium dioxide, TiO 2 , films. Aerosol deposition was used to produce films, 1 to 22 μm thick, on glass substrates. A scanning interferometric optical profiler was used to generate surface maps and measure curvature values of the substrates before and after deposition. The Stoney equation was used to calculate average film stress from the measured thickness and radius of curvature. The effect of substrate shape was also investigated by using square and beam substrates in the deposition experiments. Surface maps of the square and beam substrates after deposition showed an increasing trend towards spherical curvature as the film thickness increased. Average (compressive) stress measured for square samples was 0.37 GPa, while the average for beams was 0.52 GPa. The beam-shaped sample data showed good linearity between curvature and film thickness, and fitting to the simple Stoney formula resulted in an intrinsic stress value of 0.50 GPa. [ABSTRACT FROM AUTHOR]

The influence of the ratio between the energy and the deposition flux, or the energy per arriving atom, on the growth of Y 2 O 3 sputter deposited thin films has been studied. The energy per arriving atom has been varied by the adjustment of the discharge power, and/or the target-to-substrate distance. The relationship between the energy per arriving atom and the phase evolution, grain size, microstructure, packing density and residual stress was investigated in detail. At low energy per arriving atom, the films consist of the monoclinic B phase with a preferential (1 1 1) orientation. A minority cubic C phase appears at higher energy per arriving atom. A study of the thin film cross sections showed for all films straight columns throughout the thickness, typically for a zone II microstructure. The intrinsic stress is compressive, and increases with increasing energy per atom. The same trend is observed for the film density. Simulations show that the momentum transfer per arriving atom also scales with the energy per arriving atom. Hence, the interpretation of the observed trends as a function of the energy per arriving atom must be treated with care. [ABSTRACT FROM AUTHOR]

The aim of this work was a comparative study of the structure, mechanical, and tribological properties of VCN and VCN-Ag coatings. The VCN coatings were deposited by magnetron sputtering of V and C targets either in a gaseous mixture of Ar + 15%N 2 or in pure nitrogen. Silver was added into such coatings by simultaneous sputtering of metallic Ag target using an additional ion source. Microstructure and elemental composition of the coatings were studied by means of X-ray diffraction, transmission and scanning electron microscopy, atomic force microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. The coatings were evaluated in terms of their mechanical properties, adhesion strength, intrinsic stress, fracture toughness, room-temperature friction coefficient, as well as wear resistance and fatigue strength. Incorporation of as much as 10–11 at.% Ag was found to cause significant changes in the coating structure and properties: (i) the columnar morphology changes to equiaxial one; (ii) the coating hardness and Young's modulus decrease from 22 to 26 to 15–17 GPa and from 260 to 270 to 220 GPa, respectively; (iii) the friction coefficient and wear rate increased slightly from 0.4–0.47 to 0.51–0.53 and from 1.5–1.6 × 10 − 7 to 8.2–13.3 × 10 − 7 mm 3 /Nm, respectively; (iv) the compressive stress decreased from 1.6 to 0.3–0.5 GPa. The Ag-doped VCN coatings withstood high elastic and plastic deformation during scratching with increasing load up to 50 N without adhesive failure and applied load as high as 1000 N for 10 5 cycles during dynamic impact tests without brittle fracture. [ABSTRACT FROM AUTHOR]

The aim of this work is to study and model the effect of argon addition to the N 2 working gas on the intrinsic stress of TiN coatings deposited via rectilinear filtered vacuum arc plasma using substrate pulse bias potential. It was found that produced TiN coatings have a NaCl type cubic structure with the [110] axial texture regardless of the concentration of argon in the gas mixture. With increasing the content of argon in the gas mixture, the level of residual stress increased from 7 GPa up to 10 GPa and the coatings hardness remained at a high level of 27–32 GPa. By mathematical modeling based on the modified Davis model, it was shown that increasing the stress level in the TiN coatings with increasing of argon content was due to the intensification of the bombardment process of the coating surface by the inert gas ions. [ABSTRACT FROM AUTHOR]

The CVD diamond films at different growth stages were prepared on the same substrate by DC arc plasma jet CVD. The surface morphologies and residual stress of diamond films were characterized by scanning electron microscope and Raman spectroscopy. The intrinsic stress of diamond films were obtained by subtracting thermal stress from residual stress. The results showed that the intrinsic compress stress was 0.42 GPa for the precoalescence stage due to the sp 2 carbon inclusions in diamond islands. With the diamond islands growing up and even snapping together to form grain boundary at the coalescence stage the intrinsic compress stress was 0.06 GPa. Eventually, the diamond islands coalesced into a continuous polycrystalline film, the intrinsic compress stress vanished and converted to tensile stress, the intrinsic tensile stress reached 1.41 GPa due to the number of grain boundaries increasing. The evolution of intrinsic stress during diamond film initial growth was mainly attributed to the surface free energy of diamond islands changed to the free energy of grain boundaries which was consistent with the Nix-Clemens model. [ABSTRACT FROM AUTHOR]

Residual stresses strongly influence the behavior of components produced by forming technologies. The residual stress state is decisive for component failure both during the manufacturing process as well as during subsequent use. For this reason, residual stresses have so far been interpreted as a property which has to be avoided. Models and experiments on fatigue strength show promising approaches to the potential use of residual stresses. In the DFG Priority Programme SPP2013 which initiated this special issue, the aim is therefore to control and use residual stresses consciously with the aid of manufacturing processes so that they have a positive influence on the properties of components. [ABSTRACT FROM AUTHOR]

The effect of intrinsic stress on the structure and physical properties of silicon-tin-oxide (STO) films have been investigated. Since a state of tensile stress is available in as-deposited films, the value of stress can be exponentially enhanced when the annealing temperature is increased. The tensile stress is able to not only suppress the crystallization and widen the optical band gap of STO films, but also reduce defects of STO films. In this report, the good electrical performance of STO thin-film transistors (TFTs) can be obtained when annealing temperature is 450 °C. This includes a value of saturation mobility that can be reached at 6.7 cm2/Vs, a ratio of Ion/Ioff as 7.34 × 107, a steep sub-threshold swing at 0.625 V/decade, and a low trap density of 7.96 × 1011 eV-1.cm-2, respectively. [ABSTRACT FROM AUTHOR]

In the synthesis of epitaxial heterostructures with appreciable lattice misfit, dislocations represent a crucial linear defect. Since device quality is typically deteriorated by their presence, minimizing the dislocation density by optimized growth strategies is a key challenge for R&D. This especially holds also for the system diamond-on-iridium with its difference in lattice constants of more than 7%. As a consequence of this misfit, the initial dislocation density is very high. In this review we discuss different aspects of dislocations in heteroepitaxial diamond growth. They vary from mutual interaction mechanisms for an efficient reduction in density, over interaction with surface structures, their crucial role in the formation of intrinsic stress, their presumable role in formation of highly anisotropic stress and also their role as sink for the segregation of boron dopants. Finally, it is pointed out that the dislocation mediated stress formation may be used intentionally to strengthen devices by formation of compressively stressed surface layers. The present article is focused on recent studies from the authors' research group. [ABSTRACT FROM AUTHOR]

• A compact intrinsic stress measurement system for tansparent objects were proposed. • Full-field distributions of the intrinsic principal stresses were obtained individally after stress separation. • Principal stresses of wrinkling film with defects were determined. A compact stress measurement system for transparent objects was proposed based on the combination of photoelascity and DGS methods. The interferometry fringe and speckle image of the deformed specimen were captured from perpendicular and slant directions, respectively. The fundamentals of the stress calculation and imaging model of oblique camera viewing were analyzed mathematically. After phase-shifting computation, image correlation, and geometric transformation, full-field distributions of the major and minor intrinsic principal stresses were obtained simultaneously. A validation experiment was conducted on a circular disk under diametral compression by the proposed method. Comparison between the experimental resulsts and theoretical data calculated according to the theory of elasticity verified the feasibility and accuracy. Moreover, the combined method was also successfully applied for the intrinsic principal stresses determination on transparent wrinkling thin film with defects subjected to shearing forces. [ABSTRACT FROM AUTHOR]

Thin film metallic glasses (TFMG) can possess a variety of advantages against crystalline thin metal films. High strength and toughness as well as specific corrosion resistivity are features, which can be widely used in MEMS (micro-electromechanical systems), lab-on-a-chip or surface acoustic wave (SAW) device applications. Amongst others, the Cu–Ti binary alloy system is known for having a moderate glass forming ability (GFA) in mid-composition range. In the present study a systematic characterization of sputter deposited Cu–Ti thin films in dependence on the chemical composition is carried out. Intrinsic stress, Young's modulus, surface roughness and electrical resistivity are discussed with respect to the present phases and microstructure. Especially the films within the amorphous range from 25 to 75 at.% Cu exhibit favorable mechanical properties. [ABSTRACT FROM AUTHOR]

The effects of silicon etching and subsequent metallization during the fabrication of tungsten-lined open TSVs are examined using a combination of measurements and simulations. The total stress through a tungsten film deposited on a flat wafer is measured and finite element simulations are performed in order to identify the intrinsic and thermal stress components in the film. The data is then used to observe and model the stress through a TSV structure, which is etched using the DRIE process, resulting in scalloped inner sidewalls through the TSV opening. The scalloped structure is then compared to the ideal flat alternative with regard to the stress through the metal film and the TSV's electrical parameters, including resistance, capacitance, and inductance. It is found that the stress around the scallop varies significantly while the average stress through the tungsten in the flat TSV is only slightly higher than the stress observed through the scalloped structure. The resistance, capacitance, and inductance are all found to increase in the presence of scallops. [ABSTRACT FROM AUTHOR]

The mechanical behavior of Microelectromechanical systems (MEMS) devices is significantly influenced by fabrication processes conditions, deposition steps and geometry, e.g., processing temperature, thickness of thin film layers, deposition rate, etc. These processes under different deposition temperature will generate residual stress/strain in thin film layers, which will affect device sensing stability, accuracy and robustness, therefore, predicting and minimizing the residual stress become a critical issue on thin film devices design. This research develops a simulation methodology using finite element analysis (FEA) with process modeling technology to analyze the thermal stress/strain of thin films varying on different process procedures in a selected MEMS microphone device. In general, the residual stress/strain of multi-layers thin film is combined of intrinsic and thermal stresses, the thermal induced mechanical stress can be obtained using FEA but intrinsic stress which contains many uncertainties is very difficult to be defined. The residual stress in thin film layer on each processing procedure can be obtained from Stoney's equation. A comparison of the experiment and simulation results showed that the combined thermal induced stress and dislocation induced intrinsic stress in aluminum thin film will be rearranged after first annealing. The intrinsic stress, however, will affect the final residual stress when thickness of aluminum film is under 1 μm. The residual stress and the warpage of MEMS microphone are predicted by using processing modeling technology. The polysilicon will warp downward if the diaphragm is subjected to compressive stress. However, the polysilicon film will have much less warpage when intrinsic stress is positive. [ABSTRACT FROM AUTHOR]

The propagation properties of optical fibers can be significantly influenced by intrinsic stress. These effects are often undesired but in some cases essential for certain applications, e.g. in polarization maintaining (PM) fibers. In this paper, we present systematic studies on the influence of the fiber drawing process on the generated stress and demonstrate an approach to significantly increase the stress induced birefringence of PM-fibers. It is shown that the thermal stress caused by the material composition is superimposed with the mechanical stress caused by the fiber fabrication process. This intrinsic stress has a strong effect on the optical and mechanical properties of the glass and thus influences the fiber stability and modal behavior. By applying a thermal annealing step, the mechanical stress due to the fiber drawing process can be canceled. It is shown that this annealing step compensates the stress reducing influence of the drawing process on the birefringence of PM-fibers with panda structure. The comparison of the intrinsic stress states after fabrication with the state after the additional high temperature annealing step clearly shows that it is possible to improve the overall birefringence of panda fibers using appropriate preparation steps. [ABSTRACT FROM AUTHOR]

The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250 °C and 550 °C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed. [ABSTRACT FROM AUTHOR]