Intrinsic stresses in polycrystalline CVD diamond films have been related to restructuring at grain boundaries. It is speculated that reducing the interfacial energy induces an elastic tensile strain. There appears to be a correlation between the evolution of macroscopic stresses in the entire sample and localized, non-homogeneous stresses in the microstructure based on Raman Spectroscopy and x-ray diffraction pole figures. A multistep processing sequence developed previously can help reduce these stresses substantially, by using an intermediate annealing step when the diamond grains are partially coalesced. Our results suggest that small changes in the film microstructure due to annealing can reduce both homogeneous and non-homogeneous stresses.

The influence of ion bombardment on the mechanical stress and microstructure of sputtered silicon nitride (SiNx) films has been systematically investigated. Applied substrate bias voltage was used to control the bombardment energy in a radio frequency (rf) reactive magnetron sputtering system. The resultant films were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), Rutherford backscattering spectrometry (RBS), stress and chemical etch rate measurements. As the bias voltage was increased, the internal stress in SiNx films became increasingly compressive and reached a value of about 18.3 × 109 dyne/cm2 at higher bias voltages. These correlated well with the transition of the film microstructure from a porous microcolumnar structure containing large void to the more densely packed one. The obtained results can be explained in terms of atomic peening by energetic particles, leading to densification of the microstructure. It was also found that the amount of argon incorporated in the film is increased with increasing bias voltage, whereas the oxygen content is decreased. The lowest etch rate in buffered HF solution, approximately 1.2 Å/sec, was observed with the application of a substrate bias of -50 V.

In this report, the effect of sputtering target microstructure on the deposited film stress was investigated. By controlling the metallurgical process, two types of W-10wt%Ti target constituents, namely single-phase and multiple-phase WTi, were prepared. The former one was composed of W-rich (βTi,W) phase only, the latter one was with W, W-rich (βTi,W) and Ti-rich (βTi,W) phases. The stress of the films deposited on 12.7 cm diameter silicon oxide wafers from the single-phase target tends to be more compressive than that from the multiple-phase target. By increasing wafer temperature, the compressive stress was linearly decreased. In addition, the level of film stress was also affected by the film thickness and other sputtering parameters. To understand the causes for the differences in film stress between the multiple-phase and singlephase derived films, an evaluation of the film structure using a field-emission scanning electron microscope (FE-SEM) and mechanical testing using a nano-indentation instrument were performed. Finer domains with denser laminar structure were observed on the films deposited from the single-phase target. However, no significant difference in mechanical properties was found between these two from the nano-indentation measurements. It is envisioned that the more uniform solid solution between the W and Ti in the films obtained by sputtering the single-phase targets generates a higher compressive stress when deposited on the silicon oxide wafers resulting in a higher compressive stress.

We have developed a numerical simulation based on the boundary element method that models thermal contraction-induced stresses within semiconductor microstructures, and the effects of these stresses on surface evolution. The test case we have studied is that of polysilicon gate etch during over-etching in a plasma environment. We assume a local etch rate proportional to the normal component of the surface strain energy density gradient caused by the differential thermal contraction of polysilicon substrate and underlying silicon dioxide film. This leads to the prediction of stress-enhanced etching in the area near the polysilicon / gate oxide interface, where large stresses develop during cooling from deposition temperature to room temperature. It is proposed that stress-enhanced etching of this nature may be partially responsible for a common type of deleterious feature observed experimentally during gate electrode patterning known as “notching”.

High quality YBa2Cu3O7–δ, (YBCO) epitaxial thin films grown on MgO substrate with a strainrelieved SrTiO3 (STO) buffer layer have been investigated by Rutherford backscattering spectrometry (RBS), ion channeling and high resolution cross sectional transmission electron microscopy (XTEM). The in-situ growth of STO buffer layer along with the YBCO films was carried out by pulsed laser ablation. In this work, minimum yield of channeling measurements have shown that a very thin STO buffer layer is sufficient to grow highly crystalline YBCO thin films on MgO substrates. TEM studies showed that the STO layers were strain-relieved by an array of periodic edge dislocations. The YBCO films on STO buffer, as in those grown directly on an STO substrate, evolved from a strained layer to a largely dislocation free area.

An innovative bending-beam method is used to study the stress of thin film a-Si:H deposited on thin quartz by hot-wire chemical vapor deposition (CVD) techniques. When the deposition temperature increases from 280 to 440 °C the hydrogen content decreases from 8 to <1 at.%, and the initial compressive stress also decreases from 420 to 74 MPa. We found that there is a 10−4 photo-induced increase of the initial compressive stress under 300 mW/cm2 light-soaking, which can be recovered to the initial value by thermal annealing at 160 °C for 1 h. The results imply that the Si-H bonds contribute to the compressive stress in the a-Si:H film. There is no simple correlation between the stress and the photodegradation of the electronic properties.

Distribution of the residual stress in InGaAs/GaAs strained layer superlattices (SLSs) has been investigated by the micro-focus photoluminescence (PL) method and PL topography. Dark lines parallel or perpendicular to [011] direction were observed in the samples by PL topography. The density of dark lines was decreased as the thickness of In0.1Ga0.9As layers increased. Such dark lines were observed even in a sample whose thickness was thinner than critical value. These dark areas corresponded to the regions where the peak wavelength of PL spectrum was shifted to longer side because of tensile stress. These results were explained well by our proposed model. That is, tensile stress acts the top of mountainous regions of wrinkles which were formed by compressive stress caused by the difference of the lattice constant between InGaAs and GaAs.

TEM was used to investigate the annealing effects on the microstructure of two electrodeposited Cu/Ag multilayered nanocomposites with bi-layer thickness values of 110nm and 330nm, respectively, as well as electrodeposited pure copper. It was found that silver layers limited the lateral growth of columnar copper grains and possibly acted as sites for nucleation of new copper grains in the as-deposited composites. The refinement of copper grains in this condition is one reason for the much higher strength of these materials in comparison to pure copper. Annealing at 100 °C did not change the microstructure significantly. After annealing at 150 °C, recrystallization occurred in all samples. The degree of recrystallization was dependent on the extent of internal stresses. Recrystallization was complete in the 110nm bi-layer thick composite, which had the highest internal stresses owning to its large Cu/Ag interfacial area. The recrystallization and growth of copper grains can be one reason for the drastic drop of the composites yield strength after annealing at 150°C

TiN/TaN multilayers were grown by reactive magnetron sputtering on WC-Co sintered hard alloy and MgO(100) single crystal substrates. Multilayer structure and composition modulation amplitudes were studied using x-ray diffraction method. Hardness and elastic modulus were mea- sured by nanoindentation tester. For bilayer thickness (Λ) larger than 80 A˚, hardness are lower than rule-of-mixtures value of individual single layers, and increased rapidly with decreasing Λ, peaking at hardness values ≈33% higher than that at A=43 Å. As a result of analysis the inclination of applied load for indenter displacement on P-h curve (ΔP/Δh), this paper exhibits that the en- hancement of the resistance to dislocation motion and elastic anomaly due to coherency strains are responsible for the hardness change.

A comparative study is reported on the aluminum nitride (AIN) films on Si (111) substrate deposited by pulsed laser deposition and reactive magnetron sputtering. The structure, bonding characteristics, relative impurity levels, and wear resistance have been investigated to compare these films. We have used the techniques such as high resolution transmission electron microscopy, Raman spectroscopy, fourier transform infra-red spectroscopy, secondary ion mass spectrometry, and crater grinding method for wear test, to delineate differences between these AIN films.

Surface stress represents the reversible work per unit area to elastically stretch a solid surface, and can be associated with interfaces between two solid phases as well as free solid surfaces. The effects of surface stresses on the critical thickness for epitaxy in thin film superlattices is given.

The deformation of thin layers of glass on crystalline materials has been examined using newly developed experimental methods for nanomechanical testing. Continuous films of anorthite (CaAl2Si2O8), celsian (BaAl2Si2O8), and monticellite (CaMgSiO4) were deposited onto A12O3 surfaces by pulsed-laser deposition (PLD). Mechanical properties such as Young's modulus and hardness were probed with a high-resolution depth-sensing indentation instrument. Nanomechanical testing, combined with AFM in-situ imaging of the deformed regions, allowed force-displacement measurements and imaging of the same regions of the specimen before and immediately after indentation. Emphasis has been placed on examining how changes in the glass composition, residual stress introduced into the films, effect of film's heat-treatment, and the effect of substrate crystallographic orientation will affect the mechanical properties of silicate-glass films.

Films of Mnl.56Co0.96Ni0.48O4, 6–10 ¼m thick, were RF-magnetron sputtered onto the high temperature lift-off polyimide PiRL®; (made by Brewer Science, Inc.), and patterned into long, narrow beams using photolithography. The beams would self-delaminate, curling towards the substrate upon cooling from 300°C to room temperature after sputtering, as a result of the stress gradient in the film, caused by the deposition process. The typical radius of curvature is 8000 ¼m. Upon annealing at temperatures as low as 250°C for 10 minutes, the delaminated films continue to curl. The films curl to equilibrium radii that are functions of the annealing atmosphere and temperature. Films annealed in H2/N2 or vacuum curl more slowly than in air. TEM reveals that the first 100 nm of film is relatively porous, nanocrystalline spinel which densify instantaneously when exposed to high electron beam currents. Analysis of TEM photographs before and after annealing at 250°C indicate that the level of porosity decreases in the films by 1% which can account for the change in the curl radius. The first layers of film at the PiRL-film interface are prevented from fully densifying while on the substrate. When the film delaminates and the constraint is removed, the initial layer can densify, sintering at low temperature because the large specific surface area of the nano-crystalline microstructure provides high driving forces. The nature of the substrate-induced constraint is not fully understood. Water vapor and other light elements may be released from the polyimide if it were to continue to imidize during the deposition, and a SIMS study has been undertaken to investigate this possibility. Alternatively, the constraint may be purely mechanical, where the sintering rate is reduced as in constrained sintering of films from slurry. This effect may be important to understand when ceramic films are patterned with lift-off techniques. Empirical expressions describing the curl are developed.

Micro-Raman spectroscopy is used to study mechanical stress distribution in polycrystalline silicon bridges on cavities micromachined in crystalline Si wafers. The influence of the processing parameters such as the thickness of polycrystalline membrane, the annealing conditions (before or after removal of the sacrificial porous-Si layer ), are studied. The results indicate that the annealing reduces the residual stress by an order of magnitude and that the membrane thickness of 2.5 μm has the least residual stress.

The effects of temperatures on the stress evaluation of boron doped silicon in solid and film forms are investigated. Several techniques, such as fluid cooling to eliminate the temperature raise and/or simultaneous observation of Stokes and anti Stokes peaks to compensate the temperature effects, are applied. The advantages and disadvantages of each method and the abilities and limits of these techniques are discussed.

Micro-Raman measurements axe performed with a focused laser beam. Because of its finite diameter (∼ 1 μm) and penetration depth, the laser beam samples a “large volume” of the sample. In a nonuniformly strained sample, spectra originating from different points are different. Therefore the observed spectrum depends on both the strain distribution in the sample and the absorption coefficient of the laser light. We describe a method to calculate the Raman spectra taking these factors into account. The calculated spectra show excellent agreement with the experimental results.

The laser optical microprobe is a powerful tool for studying the spatial variation of residual stress exploiting the sensitivity of Raman and luminescence spectra to the local stress. Here, using two different examples, we consider some issues determining the depth and lateral resolution of these techniques and their use in stress mapping in thin films. The first example involves Raman microprobe studies of a strained GeSi alloy quantum wire structure. The second example involves stress mapping using chromium ion luminescence in alumina films grown by high temperature thermal oxidation of NiAl single crystals.

This work reports a comparative study on three curvature based techniques for stress measurement in thin films, including double crystal diffraction topography (DCDT), profilometry, and laser scanning technique (LST). These techniques measure different physical quantities. In the former case, the curvature of crystal lattice planes is assessed while in the latter two cases, the curvature of physical surface of a sample is measured. The current experiments use these three techniques to determine the quantities of interest for a variety of films deposited on Si (100) wafers. In general, profilometry and LST produce similar results on surface curvature. For specimens where the residual stresses produces large curvatures of both types (lattice curvature and surface curvature), the results by DCDT and LST agree fairly well. When small to moderate curvatures are present, the two methods deviate to varying degrees on absolute curvatures. Nevertheless, DCDT and LST generally yield similar results on differential curvatures, i.e., the stress induced curvature differentials. When proper consideration is taken for the inherent limits of each technique, both DCDT and LST can be used as valid procedures for stress measurement in thin film-substrate systems.

X-ray strain analysis via Generalized Focusing Diffractometry (GFD) [1], and the concurrent need for accurate values of the unstrained lattice parameter, are discussed. A new method for determining the unstrained lattice parameter without knowledge of the elastic constants of the sample material is described. Stress measurements at varying temperatures, and extraction of the coefficient of thermal expansion from these measurements, are demonstrated for aluminum and gold films.

This paper concerns the bending of rectangular foils with different width-to-length ratios, coated with a layer with high internal stress. Framework for the interpretation of experimental results is a description of the bending based on geometrically nonlinear elasticity. Calculations indicate that the (mean) biaxial modulus of coatings on foils may be determined by this method. Fully isotropic and isotropic-orthotropic bilayers are considered. Preliminary experimental results, of unbalanced magnetron sputtered PVD TiN coatings on stainless steel foil, are shown to be in qualitative agreement with the geometrically non-linear description of the bending of coated foils, provided anisotropy of the substrate and clamping conditions are taken into account.