The vibrating-membrane configuration represents an important new approach to the dynamic mechanical analysis of thin-layer materials. The method offers a convenient capability for high-resolution stress measurements over a wide temperature range, and can be combined if desired with internal friction measurements for the detection of defect-related relaxation peaks. Illustrative results are given for the thermomechanical behavior of silicon, silicon carbide, and synthetic diamond membranes, and for the moisture swelling of polyimide films. A detailed study of hydrogen-boron point defects in silicon is in progress, using both internal stress and internal friction measurements, and work on membranes has been supplemented significantly by the use of vibrating-string and ultra-thin vibrating-reed samples.

In this paper we have formulated the electronic contribution to the elastic constants in ultrathin films of p-Si by considering the influences of heavy, light and split-off holes respectively. We have suggested an experimental method of determining the same in degenerate materials having arbitrary dispersion laws. The elastic constants increase with increasing hole concentration in an oscillatory way and decrease with increasing film thickness. The theoretical formulation is in agreement with the suggested experimental method of determining second and third order elastic constants.

The vibrational technique for stress measurement in films has been used to study silver foils, silver-based conductor pastes, and aluminum foil. During cooling, a tensile stress develops in the films due to thermal expansion mismatch with the substrate. Because the stress is limited by the yield stress, these experiments furnish data for the yield stress of the materials over a wide range of temperature at fixed state. Experiments with silver specimens pre-annealed to different grain sizes show that the yield stress follows the Hall-Petch relationship. The full vibrational analysis is used to extract the stiffness of the foils.

We have investigated the microstructure, electrical resistivity and mechanical behavior of DC magnetron sputtered A1-4wt%Cu films. The substrate temperatures were varied systematically from room temperature to 500 °C. Scanning and transmission electron microscopy of the sputtered films show that the top surface of the films sputtered at low temperatures (< 200 °C) exhibits a pure Al-like fine grain morphology. In contrast, sputter deposition at higher temperatures (> 300 °C) produces films that are characterized at the top surface by a distribution of θ’-A12Cu precipitates with a platelet morphology. The mechanical behavior of the sputtered films were investigated by performing indentation tests using a depth-sensing technique.

The synthesis of aluminum nitride thin films by pulsed-laser ablation is demonstrated. The films were formed on single-crystal sapphire and graphite substrates. A number of techniques were used to characterize the films: transmission and scanning electron microscopy, Rutherford backscattering spectrometry and x-ray diffraction.

The evolution of the stress in coatings derived from divinylsiloxane bisbenzocyclobutene, mixed stereo and positional isomers of 1,3-bis(2-bicyclo[4.2.0]octa-1,3,5-trien-3-ylethenyl)-1,1,3,3-tetramethyl disiloxane (CAS 117732-87-3), has been measured on silicon substrates with an optically levered beam during thermal cycles. The stress at room temperature in gelled coatings varies between ca. 15 MPa and 45 MPa depending on the cure schedule. The progression of the polymer's glass transition temperature is correlated with the evolution of the structural state observed with FTIR. A method is presented for predictably controlling substrate curvature during multilayer processing.

Hardness properties of CVD SiO2, films deposited on silicon substrates are investigated by microindentation techniques. It is found that the hardness of these films is sensitive to the thermal histories and doping and is less influenced by the residual stress levels.

A technique is presented for measurement of elastic properties of thin films from 0.001-0.025 mm in thickness. Lamb Waves were excited in free standing films with a pulsed Nd:YAG laser, and detected using heterodyne interferometry. Elastic properties were calculated from time-of-flight measurements. Variability in waveform structure with film thickness was observed, and interpreted with respect to extraction of elastic property information. An explanation is offered for changes in waveform structure, and common features are highlighted.

Tungsten is attractive for VLSI device metallization because of its high conductivity and resistance to interdiffusion and electromigration. It is also one of the best absorber metals for x-ray lithographic masks. To minimize distortions in an x-ray mask, intrinsic stresses in the absorber films have to be low and reproducible. The physical properties of thin films are very dependent on their microstructure. We present the results of a study of the microstructural evolution and the resulting internal stress of rf sputter-deposited W films as a function of rf power, deposition temperature, and argon pressure. By controlling the nucleating phase and mobility of the adatoms, we have produced W films with low stresses (<±50 MPa). The lattice parameter and the argon content in W films increased with decreasing argon deposition pressure. It was found that a low base pressure (<10−7 torr) is necessary to produce stable α-phase W and to eliminate the metastable β-phase. Stresses in the W films were not affected bysubsequent anneals in vacuum at 200 °C for 50 hrs. In-situ stress measurements indicated stress relaxation by plastic deformation above 300 °C.

Polycrystalline diamond thin films have been selectively deposited on Si, SiO2, Si3 N4, Ta, Mo, alumina, and sapphire substrates using selective damaging by ultrasonic agitation. Novel processes were developed to selectively damage the polished substrates by ultrasonic agitation. Optical and scanning electron microscopy is used to study selectivity and morphology of as-grown diamond thin films.

Superconducting TI-Ba-Ca-Cu-O(TBCCO) films with zero resistance temperatures above 100K have been prepared on (001)MgO single-crystal substrates by the combination techniques of spray pyrolysis and Tl-diffusion. The as-sprayed Ba-Ca-Cu-O films and the sintered TBCCO superconducting bulks were wrapped in Au foil and heated in oxygen at temperatures ranging from 890 to 920°C and cooled to room temperature by furnace cooling. Highly c-axis oriented superconducting films were obtained and their average thicknesses were about 5-10 μm. The characteristics of TBCCO films by X-ray diffraction, scanning electron microscopy and electrical property are discussed.

The time and temperature dependent mechanisms underlying the relaxation of thermally induced stresses in Al-films on quartz substrates have been investigated for film thicknesses in the range between 0.4 and 4.2 μm. Film stresses were determined by a high resolution capacitive technique from the bending displacement of the specimens. By employing a lamp furnace heating rates of 10°C/sec could be achieved. This test equipment allowed the investigation of thermally induced film stresses between room temperature and 450°C and in the time range between 10 sec and several hours. Similar temperature programms were run in situ in a scanning electron microscope in order to observe the concommitant changes of the surface morphologies.

The experiments show that a major fraction of 50 to 70% of the thermal stress recovers instantaneously by plastic flow. This defines a yield stress for the Al-films which is found to be inversely proportional to the film thickness and to vary linearly with temperature. The magnitude of the yield strength under tension is larger by a factor 1.7 compared to that under compression.

We have measured the stress and the electrical resistivity of Ta-Si-N films deposited in an rf magnetron system by reactive sputtering of Ta5 Si3 target in an Ar-N2 mixture. The stress was determined by measuring the curvature of thin Si substrates with a stylus instrument. The atomic composition was established from backscattering spectra. The resistivity was derived from four-point probe measurements. The stress, the resistivity, and the atomic composition were studied as a function of various processing parameters (total pressure, gas composition). The stress is always compressive and can be changed from 0.38 - 1.48 GPa by such means. The resistivity is principally a function of the nitrogen composition and rises as the nitrogen amount increases. The results are compared with those reported for other amorphous metallic alloys.

The overwhelming majority of studies in microelectronics and fiber-optics are experimental. Not too many apply numerical, mainly finite-element, methods to analyze microelectronic and fiberoptic structures. There is a very small number of papers using analytical modeling. At the same time application of powerful and well-developed analytical methods of Engineering Mechanics often enables one to obtain valuable prior information of the mechanical behavior of materials and structures, interpret empirical data, and to extrapolate the accumulated experience on new designs [1,2]. As a rule, application of analytical modeling results in better understanding of the behavior and performance of a material or structure, and in substantial savings of time and expense. This review, based primarily on the author's research, addresses several basic and practically important problems related to the mechanical behavior of materials and-rational structural design of microelectronic and fiber-optic systems and lending themselves to sufficiently simple analytical solutions.

Mechanisms and phenomena of strain relaxation at bi-material interfaces have been studied for over half a century. The details, however, and limiting kinetics, thermodynamics and mechanics are still being sorted out - particularly for large misfit systems. Three techniques are required to accurately portray strain distributions during and after epitaxial growth: RHEED, TEM and SACP. Reflection high energy electron diffraction (RHEED) is used to measure the lattice parameter during growth. Both transmission electron microscopy (TEM) and selected area electron channeling pattern (SACP) analysis are necessary to identify the defects and the strain distribution. These techniques have been applied to NiAl and FeAl grown by MBE on GaAs with a thin AlAs buffer layer. It is shown that both island and layer by layer growth can occur with the corresponding defects being remarkably similar in character. From a combined Moiré, HREM and computer simulation, the dislocation character is assessed. Both <100> dislocations from half-loops or island edges may occur providing only partial relaxation of the film-substrate systems. The impact of the remaining elastic strain distribution on kinetic measurements of dislocation velocities is discussed.

The practice of forming electrical conduction paths in an insulating material by filling cylindrical holes with molten metal can result in high residual stresses when the metal cools. Residual stress is greatest near the metal-insulator interface, and stress relaxation by means of de-adhesion is possible. Another failure mode that poses greater practical difficulties is the growth of cracks along paths which spiral away from the interface into the brittle material. Such cracks may occur singly or in pairs, and their lengths can be sufficiently great to provide links with adjacent conduction paths. Such cracks are considered from the fracture mechanics point of view. The residual stress field is relaxed by the growth of spiral cracks which are modeled as continuous distributions of dislocations. It is assumed that these cracks grow so that the stress state on the prospective fracture plane just ahead of the crack tip is purely tensile. The paths are determined by means of an incremental numerical procedure.

Fracture strength of amorphous A1203 insulating thin film coated on a Fe-42%Ni base metal was Investigated under static and cyclic loadings by using four point bending apparatus. It was found that the both static and cyclic fracture strength of thin film decreased with increasing coating thickness and also fracture under cyclic loading occurred at a strain below the static fracture strength. Observations In detail by the optical and scanning electron microscopes revealed that the splash particles deposited in coating process caused crack initiation origins. Evaluation method of fracture strength of thin films was discussed based on the fracture mechanics approach.

Significant changes in polymer materials and their subsequent mechanical performance can occur within an expected engineering service time. These changes can be further exacerbated with environmental effects such as with solvents and mechanical stresses. Examples are given of premature field failures which illustrate the inadequacy of existing understanding and design criteria. A new approach is outlined which is based on the coupling of two fundamental concepts; a geometrical representation of material morphology on various scales and thermodynamics of morphological transformation. These concepts allow one to bridge an existing understanding of aging on molecular and morphological levels with a phenomenological continuum mechanics approach.

Microstructure of composite materials can have a profound effect upon the performance of microelectronics composed of those composite materials. Conventional analysis based on quasi-homogeneous models neglecting the structural details of the composites is inadequate. Micromechanical analysis is more complex but can provide a more realistic treatment. We have investigated the propagation of a signal in a periodic composite to examine the essential of a micromechanical analysis. By analyzing the state of the composite material just before and after the wave front as well as on both sides right next to the interfaces, we have determined the strength of the propagating signal. The results show that the property differential between material components is critical in determining the energy dissipation. In composite materials made of dissipative components such as polymers,structural details of the composite materials contribute further to the energy dissipation.

Control of thermal expansion is often necessary in the design and selection of electronic packages. In some instances, it is desirable to have a coefficient of thermal expansion intermediate between values readily attainable with single or two phase materials. The addition of a third phase in the form of fillers, whiskers, or fibers can be used to attain intermediate expansions. To help design the thermal expansion of multiphase materials for specific applications, a closed form model has been developed that accurately predicts the effective elastic properties of isotropic filled materials and transversely isotropic lamina. Properties of filled matrix materials are used as inputs to the lamina model to obtain the composite elastic properties as a function of the volume fraction of each phase. Hybrid composites with two or more fiber types are easily handled with this model. Results for glass, quartz, and Kevlar fibers with beta-eucryptite filled polymer matrices show good agreement with experimental results for X, Y, and Z thermal expansion coefficients.