The elastic biaxial modulus of a polycrystalline material as a function of [111] fiber texture was determined by imposing an equibiaxial strain and calculating the resulting stress assuming a plane-stress condition. The situation of a such a texture in a film under plane-stress is commonly seen in deposited thin films of face centered cubic metals. The calculation was performed by determining the average biaxial modulus of a single crystal as a function of tilt angle off the [111] plcine normal and then using these values in a Gaussian distribution of crystal tilts off the [111] to simulate varying degrees of texture. Results are presented for several fee materials with different elastic anisotropy factors.

The Brillouin light scattering technique has been exploited in order to investigate the elastic properties of periodic superlattices consisting of alternating layers of Fe20Ni80 (permalloy) and either Cu or Nb. These multilayers, with total thicknesses ranging between 0.2 and 0.7 mm and with periods of typically 3-5 nm, present a polycrystalline structure with (110) texture for the Nb layers and (111) texture for both the FeNi and Cu layers. Measurement of the frequency position of the Brillouin peaks corresponding to the Rayleigh and Sezawa acoustic modes allowed the effective elastic constants of these structures to be determined. The values obtained are compared with those calculated from the elastic constants of the bulk materials, taking into account the polycrystalline nature of the superlattices and the crystallographic orientation of the layers.

Internal stress change of phosphorus-doped silicon thin films during crystallization is measured by detecting substrate curvature change using a scanning laser microscope. The films are deposited in an amorphous phase by chemical vapor deposition using Si2H6 gas. The deposited films have compressive stress of about 200 MPa. The internal stress changes significantly to a tensile stress of about 800 MPa at about 600 °C due to shrinkage of the films during crystallization. The high tensile stress can be relaxed by annealing above 800 °C. The phosphorus doping changes the crystallization process of the films and their final residual stress.

The relationship of intrinsic stress and microstructural evolution in nanometer thick Mo and Si films, and Mo/Si multilayers deposited by magnetron sputtering at low working pressure (2.5 mTorr) is studied. The stress depends strongly on the microstructure which evolves with the film thickness. Transition from tensile to compressive films is observed in the metal films, in which nucleation and columnar grain growth occur. Deposition of layered Mo films by time-delayed sequential sputtering of thin layers results in smaller grains that do not extend through the film thickness, and in more tensile stress state than thick films of trie same thickness. The Si films are highly compressive at all thicknesses studied. The multilayers in this study show compressive stresses, with higher compressive stress at longer periods, and decreasing stress at shorter periods. The interface stress in amorphous Mo/Si multilayers is determined to be 1.1 J/m2. Comparison with values in other systems is made.

A series of sputtered as-prepared and annealed Ge/C multilayer structures with periods ranging from 2 to 8 nm has been studied with high resolution transmission electron microscopy (HRTEM), x-ray scattering, and stress measurement techniques. Ge/C multilayers have potential applications as normal incidence reflective mirrors near 4.4 nm wavelength. The reflectivity and stress in these structures depend on the microstructural evolution of the component layers. The as-prepared structure of both Ge and C layers appear amorphous from TEM imaging and diffraction. Annealing at 500°C for 60 minutes leads to crystallization of the Ge layers. As the phase diagram indicates, no carbide compound has been found. X-ray scattering reveals that the multilayer period expands by as much as 10% after annealing. Both TEM images and x-ray profiles suggest that the layer structures remain well-defined upon annealing. In-situ stress-temperature measurements directly show the Ge/C multilayer microstructure evolution path. X-ray measurements show that the structures with periods near 2 nm undergo a significant improvement on optical performance with annealing. The physical mechanisms that may have caused the optical enhancement are discussed. Correlation of the stress evolution in the multilayers and in individual layers during annealing, and their relationships to the microstructures and optical properties are examined.

In magnetron sputter deposition the intrinsic stress in refractory-metal films changes from compressive to tensile on increasing the working-gas pressure. This pressure dependence is linked to the particle transport process from target to substrate during deposition. In this work we apply a Monte Carlo (MC) technique to simulate the transport of sputtered atoms and reflected neutrals in a background gas. Specific examples of Cr, Mo and W thin film growth in Ar and Ne gas ambients are presented. Trends in thermalization of the depositing atoms coincided with the observed trends in the compressive-to-tensile stress curves, for the different target and working-gas combinations studied. Furthermore, a quantitative correlation between the stress transition pressures and the incident kinetic energy of both sputtered atoms and reflected neutrals during film growth was found. In this case the contribution of the latter species was weighted with a relatively low factor.

The adhesion of Ta2N thin films – often used as thin film resistors – to sapphire substrates has been studied by continuous microindentation and microscratch techniques. Ta2N films, 0.1-0.63μm in thickness, were sputter deposited onto single crystal substrates. Continuous microscratch experiments were performed by driving a conical diamond indenter simultaneously into and across the film surface until stresses high enough to delaminate the film were developed. Continuous microindentation experiments were performed to induce film spallation by normal indentation. From both of these experiments, interfacial fracture toughness was determined as a function of film thickness. The interfacial fracture toughness obtained from continuous microscratch experiments is 0.53±0.17 MPa√m, independent of film thickness. This observation indicates that there is almost no plastic deformation in the film prior to fracture so that a ‘true’ interfacial fracture toughness is measured. For the 0.63 µm thick film, continuous microindentation data yielded a fracture toughness of 0.61 ±0.08 MPa√m, which matches closely the value obtained from the microscratch test. Hence, the continuous microscratch and microindentation techniques are viable methods for determining the interfacial fracture toughness in such bi-material systems.

Continuous microscratch testing was used in this study to determine the effects of elevated temperature exposure on the adhesion and toughness of thin tantalum nitride films. These films were sputter-deposited at room temperature on sapphire substrates to a nominal thickness of 600 nm with some films heated to 600°C in vacuum while others were heated to 600°C in air. The films heated in vacuum exhibited no changes in composition or structure while the films heated in air completely transformed to tantalum pentoxide. Comparison of the results shows that the interfacial fracture toughness increases from 0.5 MPa-m1/2 for as-sputtered films to 0.8 MPa-m1/2 for films heated in air. However, the toughness increases to more than 3.0 MPa-m1/2 when the films are heated in vacuum. The increase in toughness values follows the reduction in deposition defect content where formation of an oxygen deficient tantalum oxide layer in air from the as-sputtered film increases interfacial toughness slightly while full densification of the tantalum nitride films in vacuum increases toughness to very high levels.

Raman spectroscopy is applied for the analysis of polysilicon films deposited on SiO2 sacrificial layers. Different deposition technologies and processing parameters have been studied. The features of the first order Si Raman signal (shape, width and position of maximum) are analyzed in order to evaluate the stress average value in the scattering volume. MicroRaman measurements performed at different points on the edge of the samples allows the estimation of the stress gradient through the polysilicon layers. These measurements are correlated with the structure obtained by using micromachined test structures.

Strains in polycrystalline Al films grown on oxidized Si wafers were measured using convergent beam electron diffraction (CBED). CBED patterns were acquired on a Zeiss EM 912 TEM equipped with an imaging energy filter and CCD camera. HOLZ line positions in the (000) CBED disk were matched using an automated refinement procedure. A sensitivity to variations in lattice parameter of approximately 0.00007 nm was obtained. Strong deviations from a simple equibiaxial strain, perfect [111] texture model were observed.

We studied on a nanometer scale the tribological properties of thin silicon carbide films on Si(100) wafers and stainless steel. The coatings were fabricated from a sintered SiC target by pulsed ArF laser deposition at substrate temperatures between 20 °C and 1000 °C. Amorphous films resulted at low deposition temperatures while nanocrystalline structures developed at high deposition temperatures. An atomic force/lateral force microscope was employed to characterize the film topography and the friction behavior. The microhardness was determined from measurements utilizing a depth-sensing nanoindentation instrument. The SiC films on Si(100) exhibit a smooth surface with an average roughness Ra of a few nanometer, the amorphous films being even an order of magnitude smoother. No appreciable differences were found in microhardness and friction coefficient between amorphous and nanocrystalline films. On stainless steel, amorphous SiC coatings were obtained for deposition temperatures up to 500 °C. Their surface relief portrayed the grain boundaries of the underlying steel substrate, reflecting the ballistic nature of the deposition process. No stoichiometric films were obtained above 500 °C as the silicon from the growing film quickly dissolved in the steel substrate.

All microelectronic chip interconnects are composed of polycrystalline films with properties that vary discretely with grain orientation. Techniques for dealing with this variation are developing as diminishing dimensions accentuate the effects of grain orientation. Variations in metallization microstructure affect mass transport and median failure time for metallization wearout mechanisms. Stability of adhesion layers, barrier layers and redundant conduction layers is influenced by the microstructure of the films in contact with each other. Intermetallic reactions, which are of no concern with single-level metallization, can become significant for multi level metallizations. Ti/AI systems provide typical examples of these trends.

The factors that determine the thermal strains, stresses and plastic yielding during the annealing of deposited Al thin films on Si substrates are reviewed. The effect of film texture orientation on dislocation glide is described and is shown to lead to variations in film strain energy with texture orientation. The strain energy difference between adjacent grains of different texture is proposed to account for several morphological changes during film annealing. If grain boundaries are mobile (i.e., with small initial diameter) film stresses and strain energies may induce the (secondary) growth of weakly oriented (110), (112), etc., grains at the expense of the normally favored (111) strongly oriented grains. If grain boundaries are stagnant, the strain energy differences between grains may induce the hillock growth of weakly oriented (110) grains in order to reduce film compressive stresses, and may also induce the depletion “sinking” of strongly oriented (111) grains in order to relieve film tensile stresses. This model generally accounts for these experimental findings of others.

Aluminum films 1 μm thick were deposited on oxidized silicon by sputtering and partially ionized beam evaporation to vary the crystallographic texture. These films were patterned into lines and subsequently annealed at 400 °C for 1 h. A strong correlation between the electromigration behavior and the blanket film texture (X-ray diffraction (XRD) / pole figures) has been reported previously for these films. In this work, an Electron Backscatter Diffraction (EBSD) a.k.a. Backscatter Kikuchi Diffraction (BKD) technique was employed using a scanning electron microscope (SEM) to interrogate individual grain orientations. BKD pole figures were acquired for lines ≥0.3 μm wide and for blanket (pad) regions. Identical, inverse pole figures were found for blanket films measured using both XRD and BKD (pads). Furthermore, the BKD (111) fiber texture shows a line width dependency, with narrow lines having a slightly improved texture over blanket (pad) regions. Local grain orientations were investigated near and within electromigration testing sites with characteristic void and hillock morphologies. The relationship of neighboring grain orientations to electromigration damage is shown.

Single crystal Al (111) films and bicrystal Al (110) films have been deposited on bare Si (111) and (100) wafers using ion-cluster beam deposition. The stress in the films was determined using X-rays diffraction as the films were thermally cycled from room temperature to 400C. The (111) film exhibited nearly ideal elastic behavior as the stress was essentially linear with temperature. The (110) Al film yielded in compression at a lower temperature and stress than the (111) film and exhibited broad hillocks not found in the Al (111) film. During the second thermal cycle, both films behaved in a nearly ideal elastic fashion. Measurement of the strain relaxation in the films during the second thermal cycle showed that the (110) film relaxed significantly while the (111) did not relax.

It is well known from studies of individual interfaces that grain boundaries exhibit a spectrum of properties because their structure is misorientation dependent. Usually this variability is neglected and properties are modeled using a mean field approach. The limitations inherent in this approach can be overcome, in principle, using a combination of experimental techniques, theory and modeling. The bamboo structure of an interconnect is a particularly simple polycrystalline structure that can now be readily characterized experimentally and modeled in the computer. The grain misorientations in a [111] textured aluminum line have been measured using the new automated technique of orientational imaging microscopy. By relating boundary angle to diffusivity the expected stress voiding failure processes can be predicted through the link between misorientation angle, grain boundary excess free energy and diffusivity. Consequently it can be shown that the high energy boundaries are the favored failure sites thermodynamically and kinetically.

A study of Si nucleation and deposition on SiO2 was performed using disilane and hydrogen in an ultra high vacuum rapid thermal chemical vapor deposition reactor in pressure and temperature ranges of 0.1 – 1.5 Torr and 625 – 750°C. The film analysis was carried out using scanning electron microscopy, transmission electron microscopy and atomic force microscopy. At lower pressures, an incubation time exists which leads to a retardation in film nucleation. At 750°C, the incubation time is 10s at 0.1 Torr and decreases to less than Is at 1.5 Torr. The nuclei grow and form three dimensional islands on S1O2, and as they coalesce, result in a rough surface morphology. At higher pressures, the inherent selectivity is lost resulting in a higher nucleation density and smoother surface morphology. For ˜ 2000 Å thick films, the root-mean-square surface roughness at 750ÅC ranges from 110Å at 0.1 Torr to 40Å at 1.5 Torr. Temperature also strongly influences the film structure through surface mobility and grain growth. At 1 Torr, the roughness ranges from 3Å at 625°C to 60Å at 750°C. The grain structure at 625°C/1Torr appears to be amorphous, whereas at 750°C the structure is columnar. The growth rate at 625°C/1.5 Torr is 1200 Å/min provides a surface roughness on the order of atomic dimensions which is comparable to or better than amorphous silicon deposited in LPCVD furnaces.

Polycrystalline-Si1−xGex films have been formed by various methods on oxide-coated Si substrates at temperatures ≤600°C. Compared to thermal growth, plasma deposition of poly-Si1−xGex promotes smoother films with smaller grains having a {200}-dominated texture. Poly-Si1−xGex Alms formed by plasma deposition of amorphous-Si1-xGex followed by a crystallization anneal have an even smoother surface with grain sizes enhanced by an order of magnitude and a weak {111} grain texture. Hydrogen incorporated in amorphous-Si1−xGex evolves completely during crystallization without disrupting the smooth surface morphology. The largest grain sizes (∶1.3μm) are achieved in poly-Si1−xGex films formed by Si+ ion implantation for amorphization with a subsequent recrystallization anneal.

The activation of dopants and the evolution of the microstructure of poly-SiGe films during the activation. anneal are of interest for applications such as removable diffusion sources for shallow junctions in CMOS circuit processing, low resistance contact layers and elements for thin film transistors in active matrix flat panel displays. To study these effects, 2300Å poly-SiGe films with Ge content between 20 and 48% were deposited on 600Å poly-Si seed layers by APCVD on thermally oxidized Si substrates. Growth temperatures were between 600 and 700°C. These films were then implanted with B and As at energies of 40 and 80 keV, respectively, at two different doses of 5 × 1013/cm2 and 5 × 1016/cm2. To activate the dopants, the samples were furnace annealed at temperatures from 600 to 1000°C in an N2 ambient. Additional samples were rapidly annealed at temperatures between 800 and 1050°C for times up to 120 seconds. The sheet resistance, measured using a four-point probe, of 5 × 1016 /cm2 arsenic implanted films increased by a factor of two as the Ge content in the film increased from 20 to 48%. The boron doped film, on the other hand, showed no increase in sheet resistance with Ge content. TEM showed that in all cases the grain size increased after anneal. However, the grain sizes of the annealed, arsenic doped samples were on average 5 times larger than those of the boron-doped samples with the same anneal. The sub-grain structure of these films also changed after implantation and annealing. In particular, the twin planes increased in size in boron doped samples and sub-grain twinning virtually disappeared in the arsenic doped samples. In 5 × 1016 /cm2 As implanted samples, precipitates were formed which may indicate that the As solubility limit in the films has been exceeded. These precipitates are believed to be As or Asrich and could be responsible for the sheet resistance increase with Ge fraction, since the maximum solubility for As in Ge is lower than in Si by about a factor of ten.

Shallow and lateral homogeneous delineated n+p-junctions were formed utilizing solid source diffusion from a deposited amorphous silicon layer with an in situ imbedded ultrathin phosphorus-rich zone. SIMS, AES, and TEM investigations were carried out to analyze the dopant behavior in correlation to morphological and structural changes during subsequent heat treatments. After heat treatments up to 950°C the layer remained flat, surface roughness was found to be less than 3 nm. Dopant pile up at the Si-layer/Si-substrate interface was observed and interpreted on the basis of segregation phenomena. From the time dependence the P segregation-pile-up was found to be diffusion limited except for a small starting period. The dopant concentration in the Si-substrate drops down over more than 2 orders of magnitude in a thickness range less than 20 nm.