Lateral growth of poly-Ge at temperatures as low as 150°C is reported. External mechanical stress has been properly manipulated to drive the low temperature Cu-induced crystallization of poly-Ge wherever Cu is deposited to form the crystallization seed for lateral growth. Uniaxial compressive stress has been externally applied to the Ge layer by bending the flexible PET substrate inward. A 10-hour period thermo-mechanical post-treatment in the presence of 0.05% equivalent compressive strain leads to a growth rate of 2.5 μm/hour in the direction of the applied stress and 1.8 μm/hour in the perpendicular direction, as confirmed by SEM analysis. We believe that partial growth of the Cu-seeded poly-Ge region in the form of tetragonal structures is the key feature which leads to the lateral growth of the pure-Ge strip. Elimination of the compressive stress hinders the lateral growth completely, even at reasonably high temperatures.

We studied on the thermal annealing effect on the residual stress and the mechanical properties in thin compressive stressed diamond-like carbon film on Si substrate. Annealing experiments were carried out with Rapid Thermal Procedure system at 200–600 °C, and the stress change with annealing temperature was investigated by in-situ stress measurement system. The apparent stress reduction occurred with minimal structure changes. In order to measure the change of chemical structure of diamond-like carbon film by annealing, we used Raman spectrometer. The adhesion deterioration in interface has been detected as annealing temperature increased. In the compressive stressed DLC film, we observed the dramatic evolution of interface delamination at certain high temperature using in-situ heating stage built in Environment SEM. The quantitative change of adhesion affected by annealing process was also measured with scratch testing. For exploring the interface structure affected by the thermal annealing process at high temperature, the cross section of annealed film has been observed with HR TEM.

Forming of pre-coated metal sheet becomes of increasing importance in various fields of industrial application. For instance, the trend in automotive industry goes for ready coated steel sheet that can be formed and cut without loss of performance. This so called “finish first, fabricate later” concept increases the value of the steel sheet supplied by the steel industry and releases the automotive industry from the burden of the coating process. Consequently, studies on the effect of forming on the performance of corrosion protective coating systems adhering to metals sheet are carried out in order to determine the forming limiting curves for existing coatings [1]. New coating systems are sought in order to improve the formability of coating/metal sheet composites. As a very promising step into this direction, in the recent years ultra-thin plasma-polymer films have emerged as candidates for substituting phosphatation and the environmentally critical chromatation as pre-treatments for steel sheet. These Si-containing plasma polymers provide good corrosion protection properties to steel as well as to zinc-coated steel [2–3].

Bulge test was performed on gold and gold/nitride composite films with in plane sizes ranging from 20 to 200μm. The films were prepared using the microfabrication process of a drug delivery MEMS device, and the bulge test setup was constructed using some of the packaging components of the device. Incremental pressure at 5psi interval was applied to the films, whose deflection was measured using interferometry. The extracted gold film properties from bulge test on either pure gold films or composite films yielded comparable values. The lower modulus (126∼168 GPa) comparing with the bulk gold could be due to the less dense microstructure of the evaporated gold film.

The thermo-mechanical behavior of magnetron sputtered Fe polycrystalline films of thickness between 50 nm and 400 nm has been investigated. The state of stress has been determined by means of wafer curvature and X-ray diffraction (sin2ψ-method). Both methods are in good agreement for layers of thickness above 200 nm. For specimens of smaller layer thickness, however, the average stresses as measured by X-ray diffraction are systematically higher than those observed by wafer curvature experiments. The results can be interpreted in terms of differences in micro-strain (estimated using X-ray diffraction peak width analysis) and grain size as obtained by transmission and scanning electron microscopy. Thermal cycling experiments were performed between RT and 873 K. The effect of microstructure on thermo-mechanical properties was shown to be crucial.

Thermal expansion is an important actuation mechanism for microelectromechanical system (MEMS). We investigate multi-layered cantilever microactuators actuated by resistive heating with an electric current. The actuator consists of films and sandwiched microheaters. An electrothermal-elastic model for characterizing microactuators is developed. The general analytical expressions relating tip deflection with an applied electric field, temperature change, the film thickness and the applied load at the tip are obtained. The large deflection is considered in the model. The width effect of the cantilever is also investigated using 3D finite element analysis. Based on the analytical solutions and a mixed variable programming (MVP) algorithm, the optimal design of the actuators is presented. The algorithms optimize simultaneously with respect to the number of films and the material choice from a list of candidate materials. The minimum weight and maximum deflection are chosen as the design objectives.

We have developed a wedge-loaded double-cantilever beam adhesion measurement set-up for thin films deposited on glass by magnetron sputtering. Results on the Glass/ZnO/Ag/ZnO multilayer evidence that the upper Ag/ZnO interface is tougher than the lower ZnO/Ag interface. This asymmetry in the adhesion energy between identical materials is not expected from first principles. It results from different non-equilibrium interfacial structures.

The curvature method which allows to measure the stress in epitaxial layers has been adapted to transmission electron microscopy observations. The samples thinned by the substrate side present some particular mechanical characteristics. The ratio between the substrate thickness and the layer thickness should be taken into account. The experimental conditions allowing a reliable determination of the stress have been established. A finite element calculation has been used to show that the dimensions of the area where the measure is performed can not systematically be neglected. This method has been applied to the semiconducting systems Ga1-xInxAs/GaAs and Ga1-xInxAs/InP.

We have measured and calculated the propagation velocity of successive cracks in a single sample of amorphous SiNx as a function of energy release rate. We have obtained the conditions for controlled, repetitive crack formation by using a substrate of compliant plastic that survives the cracking of a thin film formed on it. We have recorded the crack velocity curves using high-speed micro-photography using dark field illumination. Under uniform, uniaxial tensile strain, the films crack in an array of essentially straight, parallel lines, if the increase of the strain density is slow. We find reasonable agreement in the comparison of theory and experiment and find a linear relationship between the initial velocity and energy release rate threshold. Consequently, in cases where the theoretical agreement with the data is reasonable, the successive cracks show velocity curves that scale with each other.

Effects of thickness and tip geometry on Ni thin films deposited on Cu substrate were studied using nanoindenter. The deformation mechanisms in correlation to hardness measurements were discussed at various loads and depths of penetration. The Berkovich, Cube corner and Conical tips have been used in this study. Initially, the hardness and modulus of elasticity were measured at a depth of 10% of film thickness. The depth of penetration was increased to 20% to observe the depth effects. Analysis of data showed that there is an Indentation Size Effect (ISE) irrespective of indenter tip geometries.

The mechanical stresses in Cu interconnect lines arise from thermal expansion (CTE) differences, and the magnitude of the stress can be calculated based on the measured strain. In the current work, the strain (and stress) state of narrow Cu lines fabricated in oxide and porous organic spin-on dielectrics (low K) has been determined with X-Ray diffraction (XRD) during annealing. The room temperature stress along the length (X) and width (Y) of the lines are not dramatically different while the Z component is somewhat smaller with the spin-on ILD. These small perturbations in the magnitude of the Cu stress do not reflect the dramatic differences in the CTE. More insight into the materials system is obtained by studying the strain-temperature behavior, which illustrates the effect of the ILD clearly. The X strain is similar in magnitude and variation with temperature for both ILDs, supporting strain being imposed by the substrate. However, the Z strain is compressive at RT and linearly increases with temperature for Cu in low K, reflecting the lack of constraint by the ILD and the higher CTE of the ILD.

Thin metal film deposited on compliant substrate undergoes equi-biaxial compression and buckles into a highly ordered herringbone pattern [1,2]. In this study, it is shown that compare with the bifurcation competing modes, the herringbone mode has the lowest strain energy and therefore it is the preferred buckling pattern in the thin film.

When deposited at room temperature, sputtered NiTi thin films are amorphous and need to be crystallized before they can be used as a functional material. We present the results of an annealing study on substrate-constrained NiTi shape memory thin films. Amorphous films of a NiTi shape memory alloy were deposited by UHV sputtering. Films of thickness 1.0 μm were grown on (100) Si wafers both with and without an LPCVD SiNx barrier. The as-deposited films were annealed in vacuum at temperatures ranging from 500°C to 800°C. The microstructure of the annealed films was characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and Rutherford back scattering (RBS).

Thermally induced residual strains in polycrystalline Cu and Al films on single crystal Si and glass substrates, respectively, have been examined on a grain-by-grain basis by x-ray microbeam diffraction. The crystallographic orientation and the deviatoric strain tensor, εij*, are determined for each grain by white beam Laue diffraction. From grain orientation mapping and strain tensor measurements, information is obtained about the distributions of strains for similarly oriented grains, about strain variations within single grains, and about grain-to-grain correlations of strains. This type of information may be useful in developing and testing theories for intergrain effects in strain evolution in polycrystals.

Fracture tests have been carried out on micro-sized specimens prepared from a fully lamellar γ-TiAl based alloy thin foil. Micro cantilever beam type specimens with dimensions = 50 × 10 × 20 μm were prepared from one lamellar colony of the thin foil by focused ion beam machining. Notches with a width of 0.5 μm and a depth of 10 μm were also introduced into the micro-sized specimens by focused ion beam machining. Notch directions were introduced into samples in order to select the trans- and inter-lamellar directions, respectively. Fracture tests were carried out using a mechanical testing machine for micro-sized specimens. Fracture tests for the micro-sized specimens were performed successfully, showing the fracture behaviour to be dependent upon the notch orientation. The fracture toughness of specimens with a notch direction perpendicular to the lamellar direction was 4.7 – 6.9 MPam1/2, while that with a notch direction in the inter-lamellar direction was 1.4 – 2.7 MPm1/2. This indicates that the orientation of the lamellar microstructure greatly affects the fracture properties of micro-sized components prepared from fully lamellar γ-TiAl based alloy thin foils. It is required to consider the results obtained in this investigation when designing actual micro scale structures using TiAl thin foils.

Due to the corresponding intermetallic compounds, Ni/Al multi-layered thin film systems are important to protect against the mechanical and chemical impacts on the bulk component. The mechanical properties of these intermetallic compounds, NiAl, can be further improved by combining with other stiff phases. The mechanical properties would be optimized if the lateral surface composite can be made in such a way that the different phases are arranged periodically with a preferred orientation, micro-scaled period and reticulated phase interfaces. Such optimized surface composites have been achieved by laser interference irradiation in a nano-grained structure.

In this study, the thin film systems are produced by physical vapor deposition and subsequently irradiated by the interference pattern of two or more coherent laser beams. The corresponding periodical heat treatment has been analyzed by thermal simulation, and thermal simulation results are compared with the experimental results. Further, the phase transitions during laser interference irradiation are calculated. The structural investigations of irradiated films - grain sizes and deformation by TEM, stress and texture by XRD - are compared with the mechanical properties - hardness and Young's modulus by NI-AFM.

In thin film systems, failure often occurs via fracture mechanisms, with either through thickness cracking or interfacial delamination leading to failure of the device or layer. Measuring the stress at which fracture occurs in these thin film systems requires testing methods amicable to both the small scale of the films as well as the complex relationship between the mechanical properties of the film and the substrate. This paper will cover two oxide film systems, a piezoelectric ceramic (PZT) on platinum and passive oxide films (primarily Cr2O3) on stainless steels. Both will be tested with a bulk method (bulge testing in the case of PZT and circumferentially notched tensile bars for the stainless steel) and then with a nanoindentation method developed for testing fracture for hard coatings on soft substrates. The differences in stresses required for failure between the bulk and the nanoscale tests will be discussed in terms of differences in flaw population.

The tensile strengths of Nextel™ 720 fibers as well as tows and minicomposites made of these fibers were measured to study the effects of monazite coating at room temperature (RT) and 1200°C (HT). Tests were conducted on as-received materials (called unsoaked) as well as materials that had been thermally soaked at HT for 100 hours. Weibull analysis of fiber strength data shows close agreement between the Weibull modulus obtained from the statistical fracture distribution and the modulus obtained from a study of the gage length dependence of strength. The monazite coating does not change the RT strength of unsoaked single fibers, but has a beneficial effect in terms of strength retention under HT testing. This beneficial effect of the coating disappears for soaked samples. The results for tows and minicomposites also indicate that for the unsoaked condition, tensile failure appears to be driven by fiber surface flaws and the presence of the monazite coatings clearly improves both RT and HT strength of fibers, tows and minicomposites. However, the beneficial effects of the coating disappear after long term exposure to HT.

The fabrication of ultrathin (25nm) 2-dimensional free-standing arrays of tetrahedral amorphous Carbon (ta-C) microbridges is reported for the first time. The ta-C films were deposited by a Filtered Cathodic Vacuum Arc (FCVA) deposition system where the sp3 content in the film was measured to be in excess of 90% by high resolution XPS. Continuous arrays of free standing taC bridges whose length/width ratios ranged from 1:1 to 12:1 were successfully fabricated while maintaining the same thickness. Due to the naturally high compressive stress of ta-C films, the buckling of films was perpendicular to the length of the beam. The displacement of curvature obtained was in good agreement with FEM simulation results. Moreover, the curvature or arch of these ultrathin films, coupled with a high Young's modulus (750GPa) and Hardness (60GPa), meant they could withstand a vertical force in excess of 8000μN without breaking.

In ULSI circuit, interlayer thin film with low dielectric constant shall be used in order to reduce the interconnection RC delay. One promising material is methylsilesquioxane (MSQ) deposited by spin coating with controlled porosity. High porosity combined with matrix weakness result in low mechanical properties that could be detrimental to circuit reliability.

The aim of this study is to investigate the deformation behavior of mesoporous MSQ thin films by nanoindentation and by AFM analysis of residual indents. At first, proper measurement conditions were explored by modulating the film thickness from 100 nm up to 600nm for a fixed film density: the very low elastic modulus of the material on stiff substrate requires great care in the raw data analysis. Next, the density of these mesoporous films has been adjusted and the response to indentation is compared with dense bulk fused silica. AFM investigations lead to the sequence of fracture processes and to the sensitivity to hydrostatic pressure on the deformation of these materials.