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In this work, we compare the results of different Cliff–Lorimer (Cliff & Lorimer 1975) based methods in the case of a quantitative energy dispersive spectrometry investigation of light elements in ternary C–O–Si thin films. To determine the Cliff–Lorimer (C–L) k-factors, we fabricated, by focused ion beam, a standard consisting of a wedge lamella with a truncated tip, composed of two parallel SiO2 and 4H-SiC stripes. In 4H-SiC, it was not possible to obtain reliable k-factors from standard extrapolation methods owing to the strong CK-photon absorption. To overcome this problem, an extrapolation method exploiting the shape of the truncated tip of the lamella is proposed herein. The k-factors thus determined, were then used in an application of the C–L quantification procedure to a defect found at the SiO2/4H-SiC interface in the channel region of a metal-oxide field-effect-transistor device. As in this procedure, the sample thickness is required, a method to determine this quantity from the averaged and normalized scanning transmission electron microscopy intensity is also detailed. Monte Carlo simulations were used to investigate the discrepancy between experimental and theoretical k-factors and to bridge the gap between the k-factor and the Watanabe and Williams ζ-factor methods (Watanabe & Williams, 2006).

A previously developed Monte Carlo code has been extended to the X-ray microanalysis in a (scanning) transmission electron microscope of plan sections, consisting of bilayers and triple layers. To test the validity of this method for quantification purposes, a commercially available NiOx (x ∼ 1) thin film, deposited on a carbon layer, has been chosen. The composition and thickness of the NiO film and the thickness of the C support layer are obtained by fitting to the three X-ray intensity ratios I(NiK)/I(OK), I(NiK)/I(CK), and I(OK)/I(CK). Moreover, it has been investigated to what extent the resulting film composition is affected by the presence of a contaminating carbon film at the sample surface. To this end, the sample has been analyzed both in the (recommended) “grid downward” geometry and in the upside/down (“grid upward”) situation. It is found that a carbon contaminating film of few tens of nanometers must be assumed in both cases, in addition to the C support film. Consequently, assuming the proper C/NiOx/C stack in the simulations, the Monte Carlo method yields the correct oxygen concentration and thickness of the NiOx film.

Test structures consisting of shallow trench isolation (STI) structures are fabricated using advanced silicon (Si) technology. Different process parameters and geometrical features are implemented to investigate the residual mechanical stress in the structures. A technology computer aided design homemade tool, IMPACT, is upgraded and optimized to yield strain fields in deep submicron complementary metal–oxide–semiconductor devices. Residual strain in the silicon substrate is measured with micro-Raman spectroscopy (m-RS) and/or convergent beam electron diffraction (CBED) for large (25 micron) and medium size (2 micron), while only CBED is used for deep submicron STI (0.22 micron). We propose a methodology combining CBED and technology computer aided design (TCAD) with m-RS to assess the accuracy of the CBED measurements and TCAD calculations on the widest structures. The method is extended to measure (by CBED) and calculate (by TCAD) the strain tensor in the smallest structures, out of the reach of the m-RS technique. The capability of determining, by both measurement and calculation, the strain field distribution in the active regions of deep submicron devices is demonstrated. In particular, it is found that for these structures an elastoplastic model for Si relaxation must be assumed.

The use of TiSi 2 layers as ohmic contacts in complementary MOS (CMOS) devices is expected to introduce large distortions in the underlying silicon which may degrade the device performances. In this work, the TEM technique known as convergent beam electron diffraction (CBED) has been employed to map the strain distributions across 〈1 1 0〉 cross-sectional specimens of sub-quarter-micron CMOS structures. Different experimental set-ups in terms of energy filtering, liquid nitrogen cooling and zone axis have been explored and compared to each other by using three differently equipped microscopes. The strain induced on silicon by TiSi 2 layers has then been investigated, quantified and compared with that due to the presence of an oxide isolation trench. Also, the effects of depositing a TiN capping layer on TiSi 2 have been analysed. Our results show that its presence results in a more tensile strain without altering the strain distribution trend.

The Large Angle Convergent Beam Electron Diffraction (LACBED) technique has been applied to determination of the tetragonal mismatch in coherent Si/Si1−xGex/Si heterostructures. Two-dimensional (2D) dynamical simulation of the LACBED patterns has been performed and compared with the corresponding experimental ones. A good agreement is found in the whole simulated area, particularly as regards the splitting of the Bragg contours, due to the strain field present in the TEM cross-sections.

MMoO 4 /SiO 2 composites (M=Ni or Co) were prepared by a sol–gel procedure involving Si(OMe) 4 , M(NO 3 ) 2 and (NH 4 ) 6 Mo 7 O 24 as starting materials. The dried gels were treated at increasing temperatures until crystalline grains of MMoO 4 highly dispersed in the amorphous silica matrix were formed (675°C). They were evidenced by XRD and TEM measurements. Beside supporting the MMoO 4 mixed oxide, the silica xerogel appears to play the important role of stabilizing the β-phase of nickel molybdate, which otherwise would turn into the α-phase at room temperature. The catalytic activity of the β-NiMoO 4 /SiO 2 composite in the oxidative dehydrogenation of isobutane was compared with related systems containing the metastable β-molybdate.

A method for the fabrication of a wedge-shaped thin NiO lamella by focused ion beam is reported. The starting sample is an oxidized bulk single crystalline, ⟨100⟩ oriented, Ni commercial standard. The lamella is employed for the determination, by analytical electron microscopy at 200 kV of the experimental k(O-Ni) Cliff-Lorimer (G. Cliff & G.W. Lorimer, J Microsc103, 203–207, 1975) coefficient, according to the extrapolation method by Van Cappellen (E. Van Cappellen, Microsc Microstruct Microanal1, 1–22, 1990). The result thus obtained is compared to the theoretical k(O-Ni) values either implemented into the commercial software for X-ray microanalysis quantification of the scanning transmission electron microscopy/energy dispersive spectrometry equipment or calculated by the Monte Carlo method. Significant differences among the three values are found. This confirms that for a reliable quantification of binary alloys containing light elements, the choice of the Cliff-Lorimer coefficients is crucial and experimental values are recommended.

A method to perform nanobeam diffraction (NBD) in a transmission electron microscope with high spatial resolution and low convergence angle is proposed. It is based on the use of a properly fabricated condenser aperture of 1 mu m in diameter, which allows an electron beam about 10 nm in size to be focused on the sample, with a convergence angle in the 0.1 mrad range. Examples of NBD patterns taken in an untilted < 110 > cross section of a silicon device are shown. Their quality is adequate for spot position determination and hence to obtain, in principle, quantitative strain information. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3003581]

Summary A method to extract accurate information on the displacement field distribution from split high-order Laue zones lines in a convergent-beam electron diffraction pattern of nanostructures has been developed. Starting from two-dimensional many beam dynamical simulation of HOLZ patterns, we assembled a recursive procedure to reconstruct the displacement field in the investigated regions of the sample, based on the best fit of a parametrized model. This recursive procedure minimizes the differences between simulated and experimental patterns, taken in strained regions, by comparing the corresponding rocking curves of a number of high-order Laue zone reflections. Due to its sensitivity to small displacement variations along the electron beam direction, this method is able to discriminate between different models, and can be also used to map a strain field component in the specimen. We tested this method in a series of experimental convergent-beam electron diffraction patterns, taken in a shallow trench isolation structure. The method presented here is of general validity and, in principle, it can be applied to any sample where not negligible strain gradients along the beam direction are present.

The effects of 2 MeV Si+ implantation on silicon-on-insulator layers uniformly doped with B at concentrations 1.0 and 1.8 x 10(20) cm(-3), and the kinetics of damage recovery were investigated by carrier density, mobility measurements, and transmission electron microscopy (TEM) observations. High energy implantation reduces the hole density by about 98%; the mobility is also reduced at an extent which increases with B concentration. Isochronal and isothermal annealings show that recovery of the hole density takes place in three stages: the first stage (alpha) is accompanied by a mobility decrease and is followed by the second stage (beta) where mobility increases attaining values close to the ones of the reference undamaged samples. Mobility keeps nearly constant in the third recovery stage (gamma), which takes place above 800 degrees C. As a characterizing feature the mobility values for each B concentration only depend on the hole density, irrespective of the thermal history of the samples. Experiments and TEM observations allowed us to distinguish defect recovery from SiB3 precipitation, which can take place at temperatures higher than 700 degrees C. Recovery stages are discussed, and it is concluded that dissolution of B rich clusters in stage (alpha) modifies the concentration, or the charge state, of the defects responsible of the second (beta) stage. These defects are identified as boron interstitial clusters in consideration of their mobility behavior and of the activation energy E-beta for their recovery process, which results to be 3 +/- 0.2 eV.

Using a combination of the CBED and the LACBED techniques in the transmission electron microscopy (TEM), we have investigated the strain field in the silicon active region of a shallow trench isolation structure, underlying a TiSi 2 layer. Starting from the analysis of the deformation in a sample, thinned for TEM analysis, we have reconstructed the displacement field, simulating the split HOLZ lines visible in the experimental CBED patterns. From the comparison between the experimental LACBED patterns, taken in a suitable sample orientation to evidence the stressors distribution in the polycrystalline silicide layer, and the corresponding dynamically simulated ones, we have reproduced the strain field in the unthinned, bulk sample.

Silicon-germanium thin films have been analyzed by EDS microanalysis in a field emission gun scanning transmission electron microscope (FEG-STEM) equipped with a high angular dark-field detector (STEM/HAADF). Several spectra have been acquired in the same homogeneous area of the cross-sectioned sample by drift-corrected linescan acquisitions. The Ge concentrations and the local film thickness have been obtained by using a previously described Monte Carlo based “two tilt angles” method. Although the concentrations are in excellent agreement with the known values, the resulting confidence intervals are not as good as expected from the precision in beam positioning and tilt angle position and readout offered by our state-of-the-art microscope. The Gaussian shape of the SiKα and GeKα X-ray intensities allows one to use the parametric bootstrap method of statistics, whereby it becomes possible to perform the same quantitative analysis in sample regions of different compositions and thicknesses, but by doing only one measurement at the two angles.

High order Laue zone lines present in the central disk of convergent beam electron diffraction patterns have been used to determine the bulk mismatch in thinned, cross‐sectioned heterostructures, where a relaxation occurs along the thinning direction. The position of these lines is sensitive to lattice parameters along different crystallographic directions, so that information on the residual strain along the growth and the thinning directions can be extracted from a single diffraction pattern. This information has been properly combined using the isotropic elasticity theory to give the bulk mismatch. The results are in good agreement with independently obtained bulk measurements.

The principles of the convergent beam electron diffraction technique, which is a point-to-point method for local strain analysis of thin crystals in the transmission electron microscope, are briefly outlined. The availability in modern instruments of scanning attachments coupled with high-angle annular dark-field detectors (STEM/HAADF) has recently enabled the automatic acquisition of diffraction patterns ill a large number of points, selected by digitally rastering the probe in a two dimensional region of the sample. As the components of the strain tensor can be calculated at each point, 2D strain mapping has thus become possible. An example of application of the technique to deep sub-micron shallow-trench isolation structures in silicon is reported.

A method of obtaining quantitative two-dimensional (2D) maps of strain by the convergent beam electron diffraction technique in a transmission electron microscope is described. It is based on the automatic acquisition of a series of diffraction patterns generated from digital rastering the electron spot in a matrix of points within a selected area of the sample. These patterns are stored in a database and the corresponding strain tensor at each point is calculated, thus yielding a 2D strain map. An example of application of this method to cross-sectioned cells fabricated for the 0.15 μm technology of flash memories is reported.

In this paper, three techniques are discussed that provide information on process-induced local mechanical stress in silicon: the convergent beam electron diffraction technique of transmission electron microscopy, X-ray micro-diffraction and micro-Raman spectroscopy. We discuss the principles of these techniques, their spatial resolution, the ease-of-use, the information that can be obtained, the required sample preparation, the measurement time, and the complementarities of these techniques. We demonstrate this for stress induced by shallow trench isolation and correlate the results to finite element analysis results.

The convergent beam electron diffraction (CBED) technique of transmission electron microscopy (TEM) has been applied to 〈1 1 0〉 cross-sections of shallow trench isolation structures in silicon, in order to evaluate the strain field distribution in 0.22 μm wide active areas. Different spot sizes (1 and 10 nm) and sample temperatures (room temperature with energy filtering, liquid nitrogen cooling without filtering) have been employed. It has been found that the regions of the active area closer than about 100 nm to the padoxide/substrate interface can be analysed only by using a 1 nm spot size. Moreover, the use of an energy filter to reduce the inelastic scattering improves the contrast of the diffraction lines in the CBED pattern, thus allowing the analysis to be performed at room temperature.

The convergent beam electron diffraction technique (CBED) of the transmission electron microscopy (TEM) has been employed to determine the strain distribution along a cutline parallel to the padoxide/Si interface in a 0.80 micron wide recessed-LOCOS structure. The values of the components of the strain tensor so obtained have been compared with those computed by two simulator codes. It has been found that both the LOCOS morphology and the strain distribution deduced from TEM images and TEM/CBED patterns, respectively, were in agreement with the simulation results, if some oxidation-related parameters were modified.

A novel approach to the quantitative analysis of thinned samples, which exploits the finite and variable width of the incident beam of an analytical electron microscope (AEM), is reported. For a binary alloy AB, the method requires two measurements of the I(AKα)/I(BKα) X-ray intensity ratios, obtained with two different beam diameters. The digital image of the beam is also recorded by a slow-scan CCD camera; its pixel intensities are converted into probability densities by our Monte Carlo code, which has been modified to simulate the electron trajectories crossing the vertical boundaries of the sample. The result of the simulation consists of two thickness t vs concentration C matrices for the two different spot sizes; the unique t-C combination, corresponding to the analyzed region, is obtained through the convergence routine described in our previous papers.

Large-angle convergent beam electron diffraction (LACBED) dynamical simulations have been applied to the investigation of the strain distribution in the silicon region underlying a local oxidation of silicon (LOCOS) structure. This distribution is revealed through the modification of the profile of the (0 0 8) Bragg contour in the [1 2 0] projection of a [1 1 0] TEM cross-sectioned structure. If one assumes a strain field independent on the direction normal to the cross section, a contrast in the LACBED pattern is obtained only if a rotation of the lattice planes in the silicon region under stress is taken into account. The experimental patterns, taken on a submicron recessed-LOCOS, are in fair agreement with those calculated assuming, for the strain field, an analytical model based on the planar stress approximation [J. Vanhellemont, Ph.D. Thesis, University of Antwerp, 1990; I. De Wolf, J. Vanhellemont, A. Romano-Rodriguez, H. Norstrom, H.E. Maes, J. Appl. Phys. 71 (1992) 898].

The LACBED technique has been applied to the determination of the tetragonal distortion in Si 1-x Ge x /Si heterostructures, which are of great interest in the device technology. The strain determination has been performed on plan sections in an analytical electron microscope. The agreement between this strain value and the tetragonal distortion is influenced mainly by the local sample flatness and the acceleration voltage.

Two benzoylthiourea-functionalized silica xerogels, 4.5SiO2·SiO3/2(CH2)3NHC(S)NHC(O)Ph (XGbztu) and SiO3/2(CH2)3NHC(S)NH-C(O)Ph (XGbztu*), prepared by the sol–gel process, are able to bind palladium by reaction with Pd(OAc)2, giving the hybrid materials Pd/XGbztu and Pd/XGbztu*. The ligand CH3(CH2)2NHC(S)NHC(O)Ph (Hbztu), a model of the surface-binding function, on reaction with Pd(OAc)2, afforded the mononuclear complex [Pd(bztu)2] and a sulfur-containing metal colloid. Diffuse reflectance FTIR (DRIFT) experiments have shown that Pd/XGbztu* is able to fix CO at room temperature, giving a three v(CO) frequency pattern, which changes with increasing temperature. Pd/XGbztu and Pd/XGbztu* are effective catalysts in the hydrogenation of phenylacetylene to give styrene or ethylbenzene, depending on the reaction time. Nanoscale palladium aggregates have been evidenced by transmission electron microscopy (TEM) investigations on the materials after the hydrogenation processes; energy-dispersive Xray (EDX) analysis has revealed a significant presence of sulfur in the vicinity of the particles. X-Ray photoelectron spectroscopy (XPS) data have shown that Pd2+ and Pd0 are simultaneously present in Pd/XGbztu recovered after the catalytic cycle.

It is now widely accepted that one of the major issues for the future deep sub-micron integrated circuit (IC) technologies regarding yield, device performance and stability and device and product reliability, is the mechanical stress built up in the layers and substrate. It is therefore important to give a quantitative account of these stresses and this can only be achieved by disposing of reliable, performant (as to spatial resolution) and quantitative techniques for the local stress determination in the substrate, of adequate and dedicated process simulation tools and of sensitive methods to analyse the stress effects on device performance.The only experimental technique presently available which allows the strain field distribution in sub-micron CMOS devices is the convergent beam electron diffraction technique of the transmission electron microscopy. Its sensitivity is of the order of 10-4 and its spatial resolution is of 1 nm if a TEM/FEG is employed.

Boron activation and carrier mobility were measured after low temperature furnace heat treatments, in silicon layers implanted with BF2+ ions at 60 keV and at fluence in the 1 − 5 × 1015 ions cm−2 range. These quantities were correlated with boron and fluorine chemical depth profiles obtained with secondary ion mass spectrometry (SIMS), and with the lattice defects revealed by transmission electron microscopy (TEM). High dopant activation, well above the extrapolated boron solid solubility, was found for all the fluences investigated after a thermal treatment of 20 min at 600‡ C. In the high fluence implanted samples, the solid phase epitaxial regrowth of the amorphous layer induces a severe fluorine redistribution which causes the formation of a defective band at the sample surface containing microtwins and small precipitates; a decrease in both the activated dopant concentration and carrier mobility was found in this region. The comparison with dopant activation data obtained in samples diffused at higher temperature (from 900 to 1000‡ C) shows that twins are electrically active only when they are decorated by isolated impurities and/or in presence of very small precipitates.

The contrast in HREM images of small spherical coherent precipitates in silicon, having a hypothetical sphalerite structure and an SiX composition, is computed by the multislice method; X represents a dopant (or impurity) atom, ranging from boron up to platinum. The particles are assumed to have a diameter of 2 nm and to exert different amounts of in situ strain ϵ on the silicon matrix. The ideal case of no misfit (ϵ = 0) is also considered. For in situ strains 0 < ϵ < 2%, the maximum contrast, corresponding to the optimum defocus, depends mainly on the atomic number of the element X. For larger strains, which can occur in some cases if the SiX bond length in the SiX particle is determined by the covalent radius of the impurity atom X, the strain contrast dominates over the structure factor contrast. Der Kontrast in hochauflosenden, elektronenmikroskopischen Abbildungen kleiner, kugelformiger, koharenter Ausscheidungen in Silizium, die eine hypothetische Sphaleritstruktur und die Zusammensetzung SiX haben, wird mittels der Vielschichtmethode berechnet; X stellt hier ein Dotierungs- bzw. Verunreinigungsatom von Bor bis Platin dar. Es wird angenommen, das die Ausscheidungen einen Durchmesser von 2 nm haben und verschiedene in-situ-Dehnungen ϵ auf die Siliziummatrix ausuben. Der Idealfall, wo keine Fehlanpassung (ϵ = 0) vorhanden ist, wird auch betrachtet. Fur 0 < ϵ < 2% ist der maximale Kontrast, der der optimalen Defokussierung entspricht, hauptsachlich von der Atomzahl des X-Elementes abhangig. Fur grosere Dehnungen, die in einigen Fallen vorkommen konnen, wenn die SiX-Bindungslange im SiX-Teilchen vom kovalenten Radius des X-Verunreinigungsatoms bestimmt wird, uberwiegt der Dehnungskontrast den Strukturfaktorkontrast.

The apparent width of the SiO2Si interface was evaluated with Auger electron spectrometry, secondary ions mass spectrometry and transmission electron microscopy for thin silicon dioxide films grown at temperature ranging from 900 to 1100°C, both on single- and poly-crystalline silicon (polysilicon), with the aim of finding the meaning of this kind of measurement for this particular system. The width of the transition between SiO2 and polysilicon was found to depend on both the oxidation temperature and polysilicon doping method, being lower for ion implanted than for gas phase (POCl3) doped samples and for oxides grown at higher temperature. The possible causes for the differences in the interface width are discussed and attributed, in the present case, to the oxide thickness non-uniformity. This is due, in turn, to the lower oxide growth rate, particularly for the lower oxidation temperature, on the silicon grains protruding out of the surface.

The Convergent Beam Electron Diffraction technique (CBED) has been applied to determine the lattice strain in Si 1-x Ge x /Si heterostructures and below patterned films on silicon substrates. The well known problem of the stress relaxation which occurs in thinned TEM samples has been overcome, in the case of the heterostructures, by applying the isotropic elasticity theory to the lattice constants measured along different crystallographic directions through the shift of the High Order Laue Zone (HOLZ) lines in the central disk of the CBED patterns. In this way bulk strain values have been obtained, in good agreement with values deduced from independent techniques. In patterned structures, the high spatial resolution of the CBED technique has been applied to determine the distribution of the components of the strain tensor induced into oxidized silicon substrates by Si 3 N 4 stripes. A good agreement with the results obtained using numerical computations has been found.