We present in situ measurements of the intrinsic (growth) stress during nucleation and growth of thin tungsten films by chemical vapor deposition. It is shown that interfering stress sources, as recrystallization or plasic flow, do not contribute to the intrinsic stress in these films. This makes W-CVD a model system for the experimental study of the relation between the evolution of microstructure and the development ofgrowth stress.

A method has been developed to measure the stress in films which have been sputtered using a planar magnetron in a small-scale UHV chamber. The stress has been measured for diffent materials as a function of the sputtering gas pressure P and the substrate-target distance d. It is found that the stress in films of the same material deposited at different values of d is dependent only on the pressure-distance product (Pd), except at short (less than about 30mm) distances. The value of Pd required to produce a stress-free film is found to increase with the more extreme ratios between the atomic masses of the film material and the sputtering gas for the case of metals. However, the required Pd product is higher for the case of amorphous semiconductors. The stress in alloy films is also investigated.

The tensile deformation behavior of nickel/ polyimide-thin-film / copper-thin-film structures is observed using an in situ x-ray stress analysis technique. The x-ray stress is measured in the nickel and the copper simultaneously. From the analysis, the stress/strain transfer from the nickel through the polyimide to the copper can be measured.

The effect of polyimide thickness (in the range from no polyimide to 33μm of polyimide) on the stress/strain transfer behavior is reported here.

Three-dimensional elastic finite element analysis was used to investigate the stress state in patterned GaAs/Si squares with different width to thickness ratios. Quantitative results for stress relief close to free edges were obtained. Features not revealed by previous two-dimensional calculations show the necessity of the three-dimensional treatment. For large areas the calculations give an approximately uniform biaxial stress everywhere, with reduced magnitude close to free edges. This allows for straightforward interpretation of high spatial resolution luminescence spectra and precise stress measurement. Experimental results from low temperature photoluminescence show good agreement with the calculated stresses. Finally, the effects of adjacent layers of different materials on the stress in epitaxial semiconductor thin films is investigated (particularly the case of InP/GaAs/Si) and discussed in conjunction with previous results.

Polymeric materials are used as interlayer dielectrics for multichip modules. One of the central challenges for these structures is management of the large stresses induced by the differences in the thermal properties of the inorganic component structures and the organic film during processing.

Finite clement analysis has been used to model the stresses in the dielectric material in practical structures used in multilayer microelectronic architecture, such as interlayer vias and the associated internal metal patterns. Calculations have been performed on the stress field at the corner of square vias in benzocyclobutcne based interlayer dielectrics and related polymeric materials. The effects of the thermal and mechanical properties of the polymeric coating on the stress fields in metal patterns have been calculated and provide insight for design and process optimization.

This paper presents results from measurements of residual stress-induced bending moment of heavily-boron-doped (p+) silicon films. Microfabricated free-standing cantilever beams of p+ silicon were fabricated by using anisotropie etching of (100) silicon wafers in ethylene-diamine and pyrocatechol. The p+ etch stops forming the cantilevers were created by diffusion from a solid source at 1125°C for one and two hour time durations. The nonuniform residual stress distribution through the thickness of the p+ silicon cantilevers resulted in a deflection of the beams. The as-diffused p+ silicon films had a residual stress distribution through the film thickness which resulted in negative bending moments. Thermal oxidation subsequent to the diffusion step modified the residual stresses near the top surface or, perhaps, plastically deformed the near surface region of the p+ thin film. As a result, thermally oxidized p+ silicon films exhibited a positive bending moment. Measurements of the deflection curves of the beams in conjunction with beam theory were used to calculate the residual stress-induced bending moments.

The properties of polycrystalline silicon layers deposited by RTCVD have been studied by texture, stress and electrical analyse. The intrinsic layers intended for applications in integrated IC processing are very much textured with the preferred orientation depending on deposition temperature and atmosphere. Very low residual film stress in the order of 10 dyn/cm2 was detected, and a transition from compressive to tensile stress with increasing deposition temperature around 800°C was observed. This was associated with the development of the columnar structure by the (110) orientation becoming dominant at the expense of the (100) texture. Also the effect of post-deposition anneal ambience on the grain structure has been studied. Grain size and grain-boundary trapping in after doped layers have been evaluated in P-implanted RTA activated layers.

It was demonstrated in [1] that, in the absence of surface tension aflat boundary of non-hydrostatically stressed elastic solids is always unstable with respect to “mass rearrangement”. The physical mechanisms of the rearrangement can be different, for instance, a)melting-freezing or vaporization-sublimation processes at liquid-solid or vapor-solid phase boundaries, b»surface diffusion of particles along free or interfacial boundaries, b)adsorption-desorbtion of the atoms in epitaxial crystal growth, etc… We discuss the role of this instability in the problems of epitaxy and, in particular, the opportunities delivered by this instability for explanation of the recently discovered phenomena of the dislocation-free Stranski-Krastanow pattern of growth [2]. These phenomena cannot be interpreted in the framework of traditional viewpoints since, according to the classical theory, the Stranski-Krastanow pattern is a result of proliferation of the misfit dislocation appearing on the interface “crystalline film-substratum” [3].

Polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethersulfone (PES) were implanted with 200 keV boron ions at three different doses. PS was also implanted with 100 keV boron. A nanoindentation technique and reciprocating sliding wear tests were used to characterize mechanical properties of the implanted polymers. The results showed that hardness increased with increasing dose as well as increasing energy. The percentage increase in hardness was reduced with increasing complexity of the side groups although absolute hardness values were higher. With increasing complexity of the main backbone, polymer chain, the percentage increase in hardness as well as numerical hardness values were lower. These effects were attributed to the relative contributions of cross-linking and chain scission which were viewed as competing processes. Wear tests showed that in general, a lower or intermediate implant dose yielded the best improvement in wear resistance. No specific trends were observed for relating friction coefficient values and improved wear resistance. The results indicate that wear is a complex phenomenon which has a sensitive dependence on hardness and elastic properties of the mating surfaces.

The deformation of body centered iron whiskers has been simulated. The iron whisker has a very sharp yield stress. Dislocations are created in a small coppe crystal. A higher stress was needed to create the first partial dislocation but less stress to create the second partial dislocation.

Raman spectroscopy has been utilized to measure room-temperature residual strain in the active device layer of laser-recrystallized silicon-on-insulator (SOI) composite structures. The SOI composite structures were fabricated on synthetic fused-silica substrates, and the composites contained a phosphosilicate glass (PSG) layer to provide high-temperature stress relief. Conventional masking and etching techniques were used to selectively pattern the polycrys-talline silicon layer into isolated square islands prior to recrystallization. The biaxial in-plane stress in recrystallized films was calculated from the measured strain-induced first-order Stokes Raman wavenumber shifts, and the results indicate that 200- μm-square recrystallized silicon islands have significantly lower in-plane stress values than continuous recrystallized silicon films. These measurements provide a preliminary confirmation of the dependence of the time constant for viscoelastic stress relief on the in-plane pattern dimension.

Changes in mechanical stress occurring in unpatterned thin films on substrates at elevated temperatures can yield information about the kinetics of the controlling processes. In this study, a specialized furnace allowed stress at elevated temperatures to be measured by the optical-lever method. The furnace was designed for good temperature control, short thermal transient periods, accurate stress measurement with low scatter, and control of the gas ambient. Stress changes in phosphosilicate glass films measured during exposure to steam at 110–150°C allowed water diffusion coefficients to be calculated. Diffusivity decreased with increasing phosphorus content and with pre-annealing treatments. The effective activation energy for water sorption was about 0.43 eV. Analysis of stress changes associated with crystallization of amorphous silicon at temperatures near 600°C yielded an effective activation energy of 3.1 eV and a density change of about 1% for the transformation.

ABSTRACT: Internal friction has been employed to characterize various properties of thin Al and Al-alloy films. The grain boundary relaxation peak was used

a) to determine the activation energies for grain boundary diffusion in the alloy films,

b) to investigate the influence of impurities on the grain boundary diffusion in Al at concentration levels as low as 300 ppm, and

c) to get information about the adhesion strength between the film and the substrate.

We have measured elastic strain distributions with depth as a function of temperature in Al thin films of various thicknesses on oxidized silicon using synchrotron grazing incidence X-ray scattering (GIXS). Disregarding minor surface relaxation effects that depend on the film thickness, it is shown that there are no gross strain gradients in these films in the range of temperatures (between room temperature and 400°C) considered. We also observe X-ray line broadening effects, suggesting an accumulation of dislocations on cooling the films, and their annealing out as the films are reheated.

Strain gradients in Al-0.5%Cu lines on a 1000Å Ti barrier layer have been measured during thermal cycling from room temperature to 400°C using X-rays from a Synchrotron Source in the Crazing Incidence Geometry. The stress gradient calculated from the strain gradient is shown at four temperatures during thermal cycling. The surface of the line is relaxed relative to the bulk during heating and more stressed during cooling. It was also found that the width direction of the line supports essentially no stress throughout the thermal cycle and that the much of the stress along the length of the line is relaxed during the first few minutes at elevated temperatures.

A new design for a thin film microtensile tester is presented. The strain is measured directly on the free-standing thin film from the displacement of laser spots diffracted from a thin grating applied to its surface by photolithography. The diffraction grating is two-dimensional, allowing strain measurement both along and transverse to the tensile direction. In principle, both Young's modulus and Poisson's ratio of a thin film can be determined. Ag thin films with strong <111> texture were tested. The measured Young moduli agreed with those measured on bulk crystals, but the measured Poisson ratios were low, most likely due to slight transverse folding of the film that developed during the test.

A closed-form solution for a macroscopically homogeneous, fully anisotropie layer subject to non-uniform through-thickness eigenstrain is presented, and employed in determining the three-dimensional deformation and stress states of a thermally loaded ceramic film with microstructure-induced macroscopic anisotropy. The resultant stress field is compared with those that could be deduced by experimental determination of the curvature and the classical structural theories.

A recently reported nonlinear model of the bending of a thin-film/substrate bilayer provides a means for determining stress in thin films even for large deflection and ellipsoidal bending. This model replaces the usual Stoney's equation, which is valid only for small deflections. However, the model omits consideration of the commonly observed initial curvature of the substrate before deposition. In the small deflection regime the principle of superposition justifies simply subtracting the initial curvature from the final curvature after deposition, but for large deflections this is inappropriate, because the principle of superposition is no longer valid. The present paper presents a modified form of the nonlinear model incorporating initial substrate bending. The resulting equations show that initial substrate curvature causes magnified nonlinear effects and provide a means for determining film and substrate elastic properties in addition to thin-film stress.

Since its first application to thin films in the 1950's, the bulge test has had a prominent place in the field of thin film mechanical properties. The major appeal of the technique is that it is analogous to the familiar uniaxial tension test, which is commonly applied to bulk materials. At the same time, it avoids the sample tearing and alignment problems associated with micro-tensile tests. Unfortunately, bulge test results have been sometimes controversial and difficult to reproduce. In this paper we address possible causes for mese inconsistencies and describe a method by which the bulge test technique can be made to produce accurate and reliable results.

In order to advance the development of extremely hard coatings, new homogeneous and metastable films were prepared by magnetron sputter ion plating (MSIP) and arc ion plating (AIP) in the DC. or RF. mode.

In the present study coatings in the systems Ti-B-C-N, Si-C-N and amorphous carbon coatings (ADLC) were investigated and compared with other hard coatings. Multicomponent layers of different compositions and structures were deposited by varying the reactive gases methane (CH4) and nitrogen (N2) and the dominant process parameters (e. g. C/V-characteristic of the cathode, substrate bias).

X-ray diffraction studies of the Ti-B-C-N coatings revealed either an amorphous structure or crystallization in a hexagonal lattice. The ADLC and Si-C-N coatings were always amorphous. Electron microprobe analysis and auger electron spectroscopy were used to determine the coating compositions.

The tribological properties were determined by a ball on disc tribometer (e.g. friction coefficent), a pin on disc tribometer and a special abrasive wear test.