Although wafer curvature measurement provides a rapid and accurate determination of stress in a uniform thin film, the technique is not applicable to patterned films. To study the stress in metal lines, and the effect of passivation on that stress, it is necessary to use X-ray diffraction. To obtain the sensitivity and precision required, a generalized focusing diffractometer (GFD), that had been developed especially for work on thin films, was used in this study.

The elastic strain tensors for aluminum and aluminum-silicon films and patterned lines were determined by X-ray diffraction. The corresponding stress tensors were calculated with the use of the known elastic constants of aluminum. The effect of various oxide and oxynitride passivations was investigated. Passivation over uniform metal films has very little effect, while passivation over patterned metal results in substantial triaxial tensile stress in the metal. Contrary to the conventional wisdom, high compressive stress in the passivation does not result in additional tensile stress in the metal. A possible explanation for the frequently observed deleterious effect (increased tendency for formation of cracks and voids) of highly compressive silicon nitride and silicon oxynitride passivations will be discussed.

Thermal stresses in passivated and unpassivated aluminum lines bonded to substrates have been calculated using the MARC finite element code. Stresses in the unpassivated lines increase with increasing line width, with increasing substrate rigidity, and with decreasing distance from the substrate. Edge effects become significant for small line widths. Stresses in passivated lines increase with decreasing aspect ratio, with increasing passivation thickness, and with increasing Young's modulus of the passivation. Allowing plastic deformation to occur in the lines homogenizes and reduces the stresses. The calculated stresses in passivated lines are compared to recent measurements of stresses in encapsulated aluminum lines. The measured values are about a factor of four smaller than the calculated stresses, indicating that some deformation process besides plasticity, such as voiding or cracking, must have occurred to relieve the stresses.

The curvatures of thin film/substrate systems are obtained for a nonlinear plate deflection model using a Galerkin minimization procedure proposed by Hyer. A fifth order polynomial involving the curvatures is given. The results show that the linear models of Stoney and Brenner and Senderoff apply only at low stress states and that stable and unstable configurations develop at higher stresses even for isotropic systems.

The direct measurement of stresses in spin-coated thin films is crucial for understanding their end use capabilities. A new technique for measuring the residual biaxial curing stresses in spin coated polymer films has been developed. This technique uses holographic interferometry to observe the modes of vibration of a membrane under biaxial tension. The stress in the film can then be determined by application of the vibrating membrane equation. A great advantage of this technique is that the material constants of the film do not enter into the analysis. The only material parameter needed is the density. In thispaper, we will examine membranes of polyimide and biaxially stretched rubber and latex. It is possible, using this technique to resolve the principal stresses and directions in films with complicated stress states.

This paper presents a new technique for the measument of stress in films based on the classical theory of membrane vibrations. The specimens for vibrational analysis are prepared by removing a circular or square piece of the substrate far from any edge of the film (this operation preserves the state of stress in the film). The specimen is mechanically excited by random noise and its natural frequencies are peaks in the measured response of the membrane. The natural frequencies increase as the square root of stress in the film. The only material parameter needed to determine stress from the natural frequency is the density of the film. The technique has been used to measure stress in two different systems: urethane cured epoxies and silver films under different environmental conditions (temperature and humidity).

Polymeric coatings have been used in many ways from automobile paints to package coatings for integrated circuits. It is important to understand the mechanical properties of coatings in order to ensure fulfilling their designed functions. To measure these properties, in situ measurement techniques are desirable since these techniques measure the mechanical properties of coatings in the presence of the correct residual stress. In addition, the coatings most commonly used are multi-layer structures, a fact which increases the difficulty of the mechanical analysis. At present, the in situ mechanical behavior of multi-layer coatings has not been well characterized, and very few researchers have reported a satisfactory way to analyze multi-layer problems.

This paper presents experimental results of a new application of cathodoluminescence microscopy in the analysis of stress variations in epitaxial layers. Cathodoluminescence microscopy and spectroscopy techniques, in conjunction with the known behavior of the optical transitions in the presence of stress, can be effectively used for both the qualitative and quantitative analyses of spatial variations of stress in epitaxial films.

Micro Raman spectroscopy (RS) is used to study the crystalline quality and the stresses in the thin superficial silicon layer of Silicon-On-Insulator (SO) materials. Results are presented for SIMOX (Separation by IMplanted OXygen) and ZMR (Zone Melt Recrystallized) substrates. Both as implanted and annealed SIMOX structures are investigated. The results from the as implanted structures are correlated with spectroscopic ellipsometry (SE) and cross-section transmission electron microscopy (TEM) analyses on the same material. Residual stress in ZMR substrates is studied in low- and high temperature gradient regions.

In the microelectronics industry titanium disilicide (TiSi2) is used as a material for metallization and interconnection on silicon based integrated circuits. In the C54 structure (face centred orthorhombic) TiSi2 has important properties for application in electronic devices: low resistivity (16 μΩ cm), stability up to 900°C and compatibility with silicon processing. In thin films this phase is formed above approx. 700°C. However before this phase is formed, a metastable TiSi2 phase with the C49 (or ZrSi2) structure [1] is already formed at lower temperature. This C49 phase is unfavourable as metallization in IC applications because of the high resistivity (60–300 μΩ cm). From a technological point of view however it is important to realize that during the C49 formation the thin film is subject to a large change of the intrinsic stress. The occurrence of this stress can cause problems during semiconductor device fabrication. Gate oxides in MOSFETs (and other IC microstructures) may be deteriorated by stress. Also focussing problems in lithographic steps can arise because of wafer warpage. In this paper we present in situ stress measurements of the formation of TiSi2 C49 from Ti-Si multilayers. From these measurements the kinetics of the formation process is analyzed.

Self aligned cobalt disilicide technology is emerging as an excellent choice for gate and interconnection and contact metallization in VLSI. The presence of an as deposited, intrinsic stress in the cobalt film and the generation of stresses during its subsequent reaction with the underlying silicon and during post silicide processing can affect the mechanical stability and the performance of the overall device structure. This study involved the in situ observation of the stresses generated in thin films of cobalt (or silicide formed on reaction) on silicon as they react during a continuously ramped and cooled temperature cycle. The results will be presented, and in the light of a well characterized reaction sequence, possible governing mechanisms will be presented and discussed.

Stress in dielectric films, including silicon dioxide, borosilicate glass, and silicon nitride, deposited using Plasma Enhanced Chemical Vapor Deposition have been studied. In each case the total stress was found to be strongly dependent on processing conditions. Deposition rates and film characteristics, such as refractive index, -OH content, (in the case of SiO2), total H content, Si-H and N-HI concentration (in the case of nitride), boron concentration (for BSG), have also been determined as fuctions of processing parameters. In addition, the emission spectra from the plasma itself has been studied. Correlations have been established whereever relevant.

The inter-relationship between plasma processing, composition, and mechanical properties of PECVD-SiNx, thin films was investigated. Results showed that by varying the gas feeding ratio of NH3/SiH4N2, one can obtain PECVD-SiNx, films of different composition and streu levels. For high stress films, the deposition rate is low, values of index of refraction and Si/N ratio are small. On the other hand, film density of such films is high; values of Young's modulus and N-H/Si-H relative bond density are large. A model which correlates film stress to that contributed by (1) lattice distortion induced by Si-H and NH bondings, (2) ion bombardment, (3) thermal mismatch between PECVD-SiNx films and silicon substrate, and (4) intrinsic stress introduced during the formation of covalent Si-N bonding is proposed and examined in this work.

Plasma enhanced chemical vapor deposited ( PECVD ) silicon oxynitride films with refractive indices varying from 1.65 to 1.85 have been deposited in a hot-wall reactor using a SiH4/NH3/N2O gas mixture. A systematic investigation of the variation of the intrinsic stress of the deposited films with the parameters of deposition and the properties of the films, has been carried out. Our results show that silicon oxynitride films deposited in optimal conditions can support annealing temperatures of 900°C without cracking. The mechanical stresses in the films were determined by the Newton's fringes technique and a surface profiler. The film thickness was measured by ellipsometry at a wavelength of 632.8 nm. Fourier transform infrared spectroscopy ( FTIR ) was used to measure the hydrogen content of the films. The composition of the silicon oxynitride films was determined by Auger electron spectroscopy ( AES ) and Rutherford backscattering spectrometry ( RBS ).

Amorphous Gd-Fe alloy thin films were made by D.C. planar magnetron sputtering under various deposition conditions (e.g., film thickness, composition, working pressure of Ar, negative bias voltage and deposition rate). The stress, the film composition and the content of entrapped Ar in the films were measured respectively. The experimental results showed that in this case the working pressure of Ar and the negative bias voltage did not change the composition of the films, and the stresses were all compressive except for the films deposited in a very high working pressure of Ar. The origin of the compressive stress can be attributed to the atomic peening effect produced by fast neutral working gas atoms rebounded from the sputtering target. The magnitude of the compressive stress depends not only on the amount of Ar atoms incorporated in the films but also on the film microstructure such as the packing density.

The evolution of internal stresses in Tungsten films deposited on Silicon substrates submitted to external stresses is discussed here. The stresses are estimated and measured by theoretical and experimental methods. The discussion of the internal stress evolution is shown to be dependent of the film/substrate interfaces, and of the loss of adhesion inducing stress relaxation.

In VLSI processing and other applications such as printed circuit boards thin films of copper, usually used as conductors, undergo thermal cycling. This thermal cycling can cause loss of adhesion and mechanical failures thus decreasing reliability of the devices[l–7]. Understanding thermally induced stress due to mismatch of thermal expansion may assist in generating designs, processes and material replacement for increased reliability. This paper reports studies of the temperature dependence of stresses for plated and sputtered copper and plated copper-silver and copper-tin alloys. Studies of thermally annealed plated copper and copper-tin alloys are also reported.

Ion implantation of ceramics such as Al2O3 and SiC may produce a highly damaged but crystalline surface layer or an amorphous surface. The specific structure depends upon the implantation parameters. Studies using microindentation techniques show that a crystalline implanted surface has a higher hardness (by 10 to 50%) than the corresponding unimplanted crystal but the elastic modulus is essentially unchanged. The hardness and elastic modulus of amorphous implanted surfaces are less than those of the crystalline material. Estimates of the residual stress have been obtained from microindentation tests.

Polycrystalline niobium specimens were implanted with either 200 keV carbon ions or a combination of 50, 100, and 200 keV carbon ions to peak concentrations of 0.6 to 50 at. %. Microindentation techniques were used to measure the hardness and elastic modulus of the implanted layer. Both the hardness (H) and modulus (E) showed dramatic increases due to the carbon implantation. The measured peak hardness and modulus following uniform implantation with 16 at. % C were 15× and 3× that of niobium, respectively, which is comparable to the literature values for NbC. The peak hardness and modulus for the implanted specimens were observed at an indent depth of ˜40 nm, which is about one-eighth of the depth of the implanted carbon layer. The decrease in the indentation mechanical properties at deeper indent depths is due to the interaction of long-ranging strain fields underneath the indenter with the niobium substrate.

Silica Coatings of various thicknesses. hardnesses. and interface integrities were deposited on sapphire substrates using sol-gel techniques. The mechanical properties of the coatings were examined using a mechanical properties microprobe. The observed changes in hardness with indentation depth are explained on the basis of a model of the indentation sequence. in which three separate stages of the indentation process are described. In the first stage. the properties of the coating alone are probed: in the second stage. as the plastic field associated with the indenter extends beyond the coating into the substrate, the properties of the substrate begin to appear: and in the third stage. where the indenter penetrates into the substrate, the composite hardness is dominated by that of the substrate, although the properties of the coating are still apparent.

Silica coatings with as-deposited densities ranging from approximately 50-100% were deposited on sapphire substrates by electron beam evaporation and sol-gel techniques. The shrinkage, hardness, and etch rates of the coatings were measured after various heat treatments. Differences in shrinkage indicated that hardness was not controlled by bulk porosity alone. Most films exhibited a surface “crust” that was significantly harder, and etched more slowly than the interior of the sample. We propose that the differences in mechanical and chemical behavior are caused by Si-O network reorganization starting at the film/air interface.