Carbon nitride films have been deposited by the reactive pulsed laser deposition technique by ablating carbon in a nitrogen atmosphere at different substrate temperatures and different background pressures of nitrogen. Si(111) and 440C steel substrates were used in the present investigation. Deposited films are uniform and show good adhesion to the substrates. The deposition rates depend on laser fluence, background pressure, and target-substrate distance. The nitrogen concentration in the deposited films increases with increasing background nitrogen gas pressure and laser fluence. Fourier transform infrared spectroscopy has been employed to evaluated CN bonds. X-ray photoelectron spectroscopy has been used to study the composition of the deposited films. X-ray diffraction and atomic force microscopy techniques revealed that the deposited films have an oriented microcrystalline structure after annealing at 900°C with smooth surface. Electronic, mechanical and tribological properties of these films have also been discussed.

We present the uniaxial stress-strain response of a freestanding 100 nanometer thick 99.99% pure sputtered Aluminum film with grain size about 60 nanometers, tested in-situ inside a SEM chamber. The specimen is cofabricated with MEMS force and displacement sensors to minimize the experimental setup size, allowing both quantitative and in-situ tests to be performed in SEM and TEM chambers. The experimental results strongly suggest that at this size scale, a) Elastic modulus remains same as the bulk Aluminum, b) Yielding starts at about 625 MPa, and c) Strain hardening effect is absent, which indirectly suggests the deformation at this size scale is not dislocation mechanism based.

Heteroepitaxial films of aluminum bicrystals grown on silicon provide a model system in which to study plasticity in polycrystalline metal thin films. For the bicrystal films, dislocations are confined to move on two different slip plane orientations because of the orientation of the crystals on the substrate. In-situ transmission electron microscopy (TEM) observations during thermal cycling have shown two threshold temperatures for dislocation motion on cooling. A simple model uses the resolved shear stress on the possible slip planes to explain the TEM observations. Mechanisms responsible for the dislocation behavior are studied in-situ during thermal cycling between room temperature and 450°C with x-ray diffraction. The strains are determined using a sin2(Ψ) analysis at each temperature. Direct comparisons are made between the TEM observations, the model and x-ray diffraction results.

Fracture behavior of micro-sized cantilever beam type specimens prepared from an electroless deposited Ni-P amorphous alloy thin film has been investigated at ambient and elevated temperatures. Cantilever beam type specimens with dimensions of 10 x 12 x 50 μm3 were prepared from an electroless deposited Ni-P amorphous alloy thin film and notches were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches. The introduction of fatigue pre-crack and fracture toughness tests were carried out using a mechanical testing machine for micro-sized specimens. The temperature of the specimen was controlled from room temperature to 473 K using a newly developed heating system. Compared with room temperature, fracture toughness increased approximately 40 % at 373 K but decreased 19 % at 473 K. The increase of fracture toughness at 373 K is considered to be related with the formation of nano-sized crystals and the decrease of fracture toughness at 473 K is considered to be due to the growth of crystals. It is required to consider the fracture behavior obtained in this investigation when designing actual MEMS devices using electroless deposited amorphous films.

A new relationship between indentation load and depth in relation to flow stress and strain hardening exponents of film and substrate of bilayers is given. The comparison between the numerical results and those experimentally obtained from known materials, confirms the interest of the proposed model for film characterization of these materials.

The development of a novel transmission electron microscope holder has made real time observations of nanoindentation possible. Using a piezo-ceramic loading mechanism, a diamond indenter is pushed into the surface of a sample, while the electron beam images the deforming sample in cross section. In this paper, we present the method for calibrating the force-displacement-voltage relation and load-frame compliance associated with this instrument. This allows quantitative force-displacement measurements to be obtained, in the manner of traditional indentation experiments. As an example of the utility of this technique, we present observations of the indentation behavior of an Al thin film on silicon, which have been previously shown [1]. Indentation into a coarse grain shows a displacement excursion corresponding to the nucleation of dislocations, and is compared to force-displacement responses measured with instrumented indentation techniques.

As the critical feature size in microelectronic devices continues to decrease below 100 nm, new barrier materials of > 5 nm thickness are required. Recently we have shown that self-assembled monolayers (SAMs) are attractive candidates that inhibit Cu diffusion into SiO2. For SAMs to be used as barriers in real applications, however, they must also promote adhesion at the Cu/dielectric interfaces. Here, we report preliminary quantitative measurements of interfacial adhesion energy and chemical binding energy of Cu/SiO2 interfaces treated with nitrogen-terminated SAMs. Amine-containing SAMs show a ~10% higher adhesion energy with Cu, while interfaces with Cu-pyridine bonds actually show degraded adhesion, when compared with that of the reference Cu/SiN interface. However, X-ray photoelectron spectroscopy (XPS) measurements show that Cu-pyridine and Cu-amine interactions have a factor-of-four higher binding energy than that of Cu-N bonds at Cu/SiN interfaces. The lack of correlation between adhesion and chemical binding energies is most likely due to incomplete coverage of SAMs.

We report the results of tensile tests of thin films of Al-0.5 % Cu deposited on bare silicon. This material was subjected to the complete CMOS fabrication process, including a high-temperature heat treatment. Contact metal makes the electrical connection between the metal wiring and the silicon transistors in a chip. Room-temperature values of yield strength, ultimate tensile strength, and elongation were all lower than the corresponding values found previously for pure electron-beam-evaporated aluminum films. The strengths and elongation decreased slightly as the specimen temperature was raised from 25 to 150°C. The slopes of the stress-strain curves from unloading-reloading runs were lower than the accepted Young's modulus of bulk polycrystalline aluminum. The results are interpreted with the help of scanning and transmission electron microscopy.

The mechanical and resonant properties of thin film resonators are influenced by the surrounding environment. Adsorption- and surface oxidation-induced stiffening effect was observed on silicon nitride and silicon carbide cantilever beams. The resonance frequency increased logarithmically in time upon exposure to ambient air. The variations of surface stress and spring constant of the SiNx cantilever beam were calculated. Further oxynitride formation on the surface increased the stability of the resonators. The shock response of the structures was studied in various environments. The resonance frequency abruptly dropped due to cracking of the absorbed surface layer, than recovered logarithmically. The initial drop and the recovery rate is environment dependant. Humidity increased, while argon and nitrogen rich environments mitigated the degrading effects. The SiCx is more inert to the environmental effects and proved to be a promising candidate as structural material in resonant MEMS devices.

The failure of Si3N4 metal-insulator-metal (MIM) capacitors fabricated by plasma enhanced chemical vapor deposition (PECVD) was investigated using cross-sectional transmission electron microscopy (XTEM) and residual stress analysis. As a result we noted that the failure of the Si3N4 MIM capacitors originated from the microvoids formed over the Si3N4 dielectric and the TiN interlayer. The microvoid of the MIM capacitor, particularly in case of having a very thin Si3N4 of less than 50 nm-thick, caused it to leak out much of the current to the extent of a few microamperes even at bias of 3 volts. The formation of microvoids was explained by the residual stress of the constituent layers at a mechanistic point of view. The stress analysis showed that the absolute stress normalized by the thickness of the Si3N4 layer should be less than 31 MPa/nm to avoid microvoiding. In this research it was noted in conclusion that the stress state of not only the dielectric but also the interlayer should be taken into account for the successful design of high capacitive Si3N4 MIM capacitors.

Nanoindentation has been successfully used as a mechanical properties microprobe to characterise the elastic properties of materials. However, in an isotropic material it is not possible to measure the two independent elastic constants by nanoindentation. Normally, a value of Young's modulus is determined using an assumed value for Poisson's ratio. It is also possible to use the acoustic microscope in its z-contrast mode to measure the elastic constants of a surface. This too produces a composite measurement of the elastic properties, which can be represented in terms of Young's modulus and Poisson's ratio. By using both techniques on the same sample area, it is possible to make two independent measurements of the elastic properties and thus determine both Young's modulus and Poisson's ratio. This method has been used on well-characterised bulk materials, e.g. silica glass, to demonstrate that it produces consistent results. It has also been uused to characterise thin films of TiN/NbN multilayers. These results show that, although for thin films there is a need to improve the analysis of the mechanics, the combination of nanoindentation and acoustic microscopy shows promise.

Free-standing gold thin-film tension specimens of thicknesses in the range 500-700 nm were fabricated by e-beam deposition methods. The films have grains which have thicknesses essentially equal to the film thickness, and an in-plane grain-size distribution which is bi-modal, with a collection of small grains with an average size of 130 nm, and another collection of larger grains with an average size of 380 nm. The films possess a strong texture with the {111} crystallographic planes aligned with the plane of the film. The thin-film specimens have been tested in simple tension using a novel testing machine which enables measurement of the elastic-plastic stress-strain response of the films with high resolution. The experiments show that the gold thin-films have an initial yield strength of around 100 MPa, which is followed by rapid strain hardening to a stress level of 360 MPa at a strain of only ~1.2%, at which point the specimens fail abruptly. Transmission electron microscopy (TEM) investigations of the deformed films shows that the rapid strain hardening is attributable to extensive dislocation activity in the larger grains. The reason behind the low ductility in our gold specimens is still unclear, but it may be attributable to the observed lack of dislocation activity in the smaller grains, whose boundaries then serve as easier sites for alternative inelastic mechanisms such as grain boundary sliding and decohesion leading to low macroscopic strains to failure.

Cu films with thickness of 500nm and 5nm have been sputter deposited on amorphous SiO2 and Si3N4 substrates without and after sputter cleaning. The crystallographic texture has been characterized by x-ray diffraction techniques. Sputter cleaning of the substrates, by which the oxygen contaminants are removed from the Si3N4 substrates, leads to an increase in the {111} texture strength and sharpness of the Cu films on Si3N4. The texture is sharper in the 500nm thick Cu films than in the 5nm thick films. Roughness differences of the substrate surfaces have no obvious effect on the texture state.

We describe progress on the issue of pathological elastic wave reflection in atomistic and multiscale simulation. First we briefly r eview Coarse-Grained Molecular Dynamics (CGMD). Originally CGMD was formulated as a Hamiltonian system in which energy is conserved. This formulation is useful for many applications, but recently CGMD has been extended to include generalized Langevin forces. Here we describe how Langevin dynamics arise naturally in CGMD, and we examine the implication for elastic wave scattering.

The topology of telephone cord buckles that form beneath compressed diamond-like carbon films (DLC) on glass substrates has been characterized with Atomic Force Microscopy (AFM) and with the Focused Ion Beam (FIB). Using AFM with 2nm resolution, the wavelength and amplitude of the buckles and their profiles have been measured. It has been found that, within each wavelength, the profile has symmetric and asymmetric segments. These changes have been related to differences in local mode mixity around the periphery of each repeat unit along the buckle, resulting in a fundamental rationale for the factors governing the wavelength. Sections made through various segments of the buckle by using the FIB imaging system result in local changes in the shape and size of the buckles that provide further insight into the buckle propagation criterion.

Copper films of different thicknesses between 0.2 and 2 microns were electroplated on adhesion-promoting TiW and Ta barrier layers on <100> single crystal 6-inch silicon wafers. The residual stress was measured after each processing step using a wafer curvature technique employing Stoney's equation. Large gradients in the stress distributions were found across each wafer. Controlled Cu grain growth was achieved by annealing films at 350 C for 3 minutes in high vacuum. Annealing increased the average tensile residual stress by about 200 MPa for all the films, which is in agreement with stress-temperature cycling measurements.

After aging for 1 year wafer stress mapping showed that the stress gradients in the copper films were alleviated. No stress discrepancies between the copper on Ta and TiW barrier layers could be found. However, X-ray pole figure analysis showed broad and shifted (111) texture in films on a TiW underlayer, whereas the (111) texture in Cu films on Ta is sharp and centered.

The constitutive behavior of passivated copper films is studied. Stresses in copper films of thickness ranging from 1000 nm to 40 nm, passivated with silicon oxide on a quartz or silicon substrate, were measured using the curvature method. The thermal cycling spans a temperature range from - 196 to 600°C. It is seen that the strong relaxation at high temperatures normally found in unpassivated films is nonexistent for passivated films. The copper film did not show any rate-dependent effect over a range of heating/cooling rate from 5 to 25°C/min. Further analyses showed that significant strain hardening exists during the course of thermal loading. In particular, the measured stress- temperature response can only be fitted with a kinematic hardening model, if a simple constitutive law within the continuum plasticity framework is to be used. The analytic procedures for extracting the film properties are presented. Implications to stress modeling of copper interconnects in actual devices are discussed.

Microscopic studies of the plastic deformation of a simple polymer-metal laminate (PET-steel) are outlined. Representative examples of deformation and failure modes are illustrated with qualitative results from birefringence microscopy. The relation between bulk PET mechanical behaviour and laminate properties is discussed.

Reservoir length dependencies of electromigration lifetime in multilevel interconnect were compared for two passivation dielectrics, that is, FOX (Flowable Oxide) and HDP FSG (High Density Plasma Fluorinated Silicate Glass). The higher electromigration resistance of interconnects passivated by FOX can be best explained by their lower stress and vacancy concentration levels than the case for FSG. It was also proposed that lower levels of stress and vacancy concentration in the longer reservoir could partially contribute to the better electromigration reliability of interconnect with the longer reservoir.

In order to shed light on the role that grain boundaries and dislocations play in anelastic relaxation of thin films and small-scale structures, we measured the effective elastic moduli of 99.99% pure Al and Cu 10 m m diameter micro-wires in the as-received (drawn and slight tempered) and annealed states. Moduli were determined using microtensile tests at various strain rates (6.7x10-6s-1, 1.3x10-5s-1, 2.6x10-5s-1, 4.5x10-5s-1, 2.5x10-4s-1, 4.5x10-4s-1). Focused-ion beam scanning electron microscopy was used for imaging grain sizes. Results from the as-received wires are compared with the annealed wires to illustrate the effects of grain size and dislocation density on effective moduli, which closely relates to grain boundary sliding and dislocation motion, respectively. We conclude that microstructure is more significant than scale in inducing anelasticity in small-scale wires and, by extension, thin films.