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The discovery of auxetic behavior (negative Poisson's ratio) within elements and alloys had focused attention on their elastic anisotropy in an effort to understand the range of crystal orientations that manifest this property. A comparison of elastic constant data to atomistic models based on pair-wise, central force models provides key insights into deformation behavior of cubic crystals over a wide range of anisotropy, including, for the first time, those with Zener anisotropy ratios less than 1. A simple criterion is derived which dictates all cases in which a crystal whose atomic ordering obeys cubic symmetry will display auxetic deformation, where the extrema in Poisson's ratio involves (110) orientations. In the field of stress determination through x-ray diffraction, these findings also shed light on strain anisotropy in polycrystalline materials, where the elastic incompatibility between adjacent grains alters their overall deformation. By applying these same atomistic models, we can predict the Voigt/Reuss weighting fractions associated with Kröner limit x-ray elastic constants for cubic materials, a necessary component in quantifying stress using diffraction data. We also establish that greater elastic anisotropy in a constituent crystal leads to a more rigid mechanical response in the corresponding polycrystalline aggregate, with implications for auxetic crystal ensembles. [ABSTRACT FROM AUTHOR]

Strain within nanoscale strained SiGe FinFET structures has been investigated using a combination of X-ray diffraction and transmission electron microscopy-based nanobeam diffraction (NBD) techniques to reveal the evolution of the stress state within the FinFETs. Reciprocal space maps collected using high-resolution X-ray diffraction exhibited distinct features corresponding to the SiGe fin width, pitch, and lattice deformation and were analyzed to quantify the state of stress within the fins. Although the majority of the SiGe fin volume exhibited a uniaxial stress state due to elastic relaxation of the transverse in-plane stress, NBD measurements confirmed a small interaction region near the SOI interface that is mechanically constrained by the underlying substrate. We have quantitatively characterized the evolution of the fin stress state from biaxial to uniaxial as a function of fin aspect ratio and Ge fraction and confirmed that the fins obey elastic deformation based on a model that depends on the relative difference between the equilibrium Si and SiGe lattice constants and relative fraction of in-plane stress transverse to the SiGe fins. Spatially resolved, nanobeam X-ray diffraction measurements conducted near the SiGe fin edge indicate the presence of additional elastic relaxation from a uniaxial stress state to a fully relaxed state at the fin edge. Mapping of the lattice deformation within 500 nm of this fin edge by NBD revealed large gradients, particularly at the top corner of the fin. The values of the volume averaged lattice deformation obtained by nanoXRD and NBD are qualitatively consistent. Furthermore, the modulation of strain at the fin edge obtained by quantitative analysis of the nanoXRD results agrees with the lattice deformation profile obtained by NBD. [ABSTRACT FROM AUTHOR]

Experimental data are presented showing that low energy (< 2 MeV) proton irradiation can upset exploratory 65 nm node, Silicon-On-Insulator circuits. Alpha particle SER data, modeling and simulation results provide a plausible mechanism. This work suggests that track structures need to be understood and effectively modeled, especially for small, modern devices. Index Terms--Alpha particles, direct ionization, protons, radiation effects, simulations, soft error rate.

Novel techniques have been developed to simulate particle transport in arbitrarily complex back-end-of-line topologies. They are shown to be critical for single event effect analyses of new device structures for 65 nm CMOS technologies and beyond. The salient features of the new modeling methods are illustrated by the simulation results taken from several case studies of particle-induced radiation problems in the back end. Index Terms--Alpha-particle radiation effects, energy deposition, ion radiation effects, radiation effects, simulations, single event effect, single event upset, soft fail rate.

Simple expressions for the edge-force stress distributions corresponding to a strained film feature edge on an anisotropic substrate were generated, based on the mechanics of an elastically anisotropic half space. The resulting stress distributions showed the greatest variation from those predicted for an elastically isotropic substrate near the substrate surface.

Author(s): David B. Mitzi (corresponding author); Laura L. Kosbar; Conal E. Murray; Matthew Copel; Ali Afzali The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis [...]

In-line high resolution X-ray diffraction has been used to analyze embedded silicon-germanium (eSiGe) epitaxially grown in the source/drain regions of complementary metal-oxide-semiconductor devices. Compared to blanket films, the diffraction from patterned devices exhibited distinct features corresponding to the eSiGe in the source/drain regions and Si under the gate and SiGe. The diffraction features modulated with structural changes, alloy composition, and subsequent thermal processing. Reciprocal space measurements taken around the (224) diffraction peak revealed both in-plane (h) and out-of-plane (l) lattice deformation, along with features corresponding to the regular spacing between the gates. [ABSTRACT FROM AUTHOR]

The microstructural evolution within plated Cu films has been investigated using high-resolution x-ray diffraction, revealing a change in strain state within the recrystallized grains and the surrounding matrix with time. By approximating the case of an isolated grain in a randomly textured material as an Eshelby inclusion in an elastically isotropic matrix, we can determine the elastic strain energy in addition to the interaction strains that develop within the grain due to the effects of elastic anisotropy. The elastic strain energy density generated by a grain possessing cubic symmetry with arbitrary orientation within an elastically isotropic matrix has been compared to that within a fiber-textured film, revealing that the former case possesses less strain energy. These results suggest that the recrystallization of Cu (111) grains from an electroplated film with a small, initial grain size is less energetically favorable for films exhibiting strong (111) texture than for a randomly textured film. Experimental results indicate a sequence that emerges during the recrystallization process: (111) grains grow first, suggesting that the decrease in surface energy provided by the (111) surfaces is larger than the increase in elastic strain energy created by (111) grains. For sufficiently thick films, (100) grains emerge, lowering the strain energy density in the film, after (111) grain growth has saturated because no further decrease in energy is supplied by (111) surface growth. By examining plated Cu films of different thicknesses, we correlate the appearance of recrystallized (100) grains with a threshold energy density based on the additional energy associated with (100) surfaces relative to (111) surfaces. [ABSTRACT FROM AUTHOR]

We investigated the temporal evolution of nickel-silicide phase-formation and the simultaneous redistribution of platinum during silicidation of a 10 nm thick Ni0.95Pt0.05 film on a Si(100) substrate. Grazing incidence x-ray diffraction (GIXRD) and atom-probe tomography (APT) measurements were performed on as-deposited films and after rapid thermal annealing (RTA) at 320 or 420 °C for different times. Observation of the Ni2Si phase in as-deposited films, both with and without platinum alloying, is attributed to surface preparation. RTA at 320 °C for 5 s results in the formation of the low-resistivity NiSi intermetallic phase and nickel-rich phases, Ni2Si and Ni3Si2, as demonstrated by GIXRD measurements. At 420 °C for 5 s, the NiSi phase grows outward from the silicide/Si(100) interface by consuming the nickel-rich silicide phases. On increasing the annealing time at 420 °C to 30 min, this reaction is driven towards completion. The nickel-silicide/silicon interface is reconstructed in three-dimensions employing APT and its chemical root-mean-square roughness, based on a silicon isoconcentration surface, decreases to 0.6 nm with the formation of the NiSi phase during silicidation. Pt redistribution is affected by the simultaneous reaction between Ni and Si during silicidation, and it influences the resulting microstructure and thermal stability of the NiSi phase. Short-circuit diffusion of Pt via grain boundaries in NiSi is observed, which affects the resultant grain size, morphology, and possibly the preferred orientation of the NiSi grains. Pt segregates at the NiSi/Si(100) heterophase interface and may be responsible for the morphological stabilization of NiSi against agglomeration to temperatures greater than 650 °C. The Gibbsian interfacial excess of Pt at the NiSi/Si(100) interface after RTA at 420 °C for 5 s is 1.2 ± 0.01 atoms nm-2 and then increases to 2.1 ± 0.02 atoms nm-2 after 30 min at 420 °C, corresponding to a decrease in the interfacial free energy of 7.1 mJ m-2. [ABSTRACT FROM AUTHOR]

The measurement of stress using x-ray diffraction requires knowledge of the constitutive equation linking strain and stress for the sample under investigation. With the exception of single-crystal materials, a unique constitutive relation does not exist requiring an average over the diffracting ensemble. Such averaging techniques provide bounds to the range of x-ray elastic constants, whose values depend on the elastic anisotropy of the material, the mechanical response of the crystallites and often the x-ray reflection chosen. In fact, for materials possessing cubic symmetry, the general x-ray stress equation can be reduced to a form that relates the measured strain to the hydrostatic stress and the bulk modulus, quantities that are invariant with respect to crystal orientation. These orientations do not correspond to stress-free values but rather to lattice parameters that are independent of the x-ray reflection used. Examples include the application of this technique to a test case of an isotropic, biaxially stressed film, and determining the triaxial stress states in capped features. The validity of these orientations, which are developed for specific stress states, relies on the assumption that the polycrystalline aggregate behaves as a quasi-isotropic ensemble. [ABSTRACT FROM AUTHOR]

Rotation and strain fields were mapped across silicon-on-insulator (SOI) regions induced by overlying stressed Si3N4 features using x-ray nanobeam diffraction. The distribution in SOI tilt exhibited an antisymmetric distribution with a maximum magnitude of 7.9 milliradians, representing one of the first direct measurements of the lattice tilt conducted in situ within buried layers using a spot size of less than 100 nm. The measured rotation distribution corresponds to simulated values generated by boundary element method modeling, indicating that the strain transfer into the underlying SOI primarily induces elastic deformation. [ABSTRACT FROM AUTHOR]

Lattice spacing measurements of the (211)/(202), (020)/(013), and (111)/(102) reflections were used to calculate the residual stresses in a Ni monosilicide film after cooling from its formation temperature. The ability to measure stresses in crystalline materials using x-ray diffraction requires the use of appropriate x-ray elastic constants, which link the measured strain to the stress tensor of the grains that satisfy the diffraction condition. X-ray elastic constants were calculated in the Neerfeld–Hill (NH) limit for a polycrystalline aggregate composed of orthorhombic crystals. The anisotropy in grains that possess orthorhombic elasticity introduces significant variation in the stresses determined among the three sets of reflections. However, the in-plane stress calculated due to thermal expansion mismatch between NiSi and the underlying Si substrate shows a close correspondence to the average of x-ray measurements. [ABSTRACT FROM AUTHOR]

The effects of stressed thin films on substrates that possess anisotropic elasticity have been measured and modeled. Substrate curvature induced by a uniform, stressed film will be axisymmetric for substrates possessing greater than twofold in-plane symmetry, and anisotropic for twofold symmetric substrates. For a (011) Si substrate, the difference between the curvature along the <110> and <100> principal axes varies by approximately 47%. A simple, analytical formulation of the force and moment balance equations for elastically anisotropic films and substrates has been employed to calculate the dependence of curvature and strain on substrate orientation for several cases. [ABSTRACT FROM AUTHOR]

We have used scanning microdiffraction topography to determine the mismatch strains and local strain distributions in silicon-on-insulator substrates with overlying thin film stressor features. Analysis of the data using the edge-force model and the Ewald–von Laue dynamical diffraction theory shows the presence of an exponential strain gradient in the vicinity of the buried SiO2/Si-substrate interface. We show that, for simple geometries, it is possible to deduce the sign of the mismatch strain simply by inspecting the microdiffraction topograph. [ABSTRACT FROM AUTHOR]

Strain distributions within a silicon-on-insulator (SOI) layer induced by overlying compressively stressed Si3N4 features were measured using x-ray microbeam diffraction. A comparison of analytical and numerical mechanical models of the depth-averaged strain distributions to the measured strain profiles in the SOI layer indicated a blanket film stress of -2.5 GPa in the Si3N4 features. A two-dimensional boundary element model, implemented to analyze thin film/substrate systems, reproduced the observed strain distributions better than an edge-force formulation due to the incorporation of loading along the Si3N4/Si interface. [ABSTRACT FROM AUTHOR]