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International audience; Nanoindentation is widely used to investigate elastic modulus, hardness and work hardening behaviour of nano- and micro-scale laminates. In this work, 16 nm accumulative roll bonding (ARB) Cu/Nb nanolaminate is used as a test material due to its interfacial anisotropy owing to the presence of contrasting interfaces along rolling (RD) and transverse direction (TD). Nanoindentation was performed along TD as well as RD of ARB Cu/Nb nanolaminate, and then scanning probe microscopy (SPM) data were collected to measure the pileup along RD and TD. Nanolaminate along RD was found to show higher surface pileup than TD which is attributed to crystallographic and interfacial anisotropy resulting in (a) higher yield strength (low plasticity) along TD in comparison to RD and (b) high interfacial sliding in the case of TD resulting in less co-deformation of layers in comparison to RD. The characterization of surface pileup is of significant importance for facilitating the study of anisotropic micro/nanolaminates.

Stress changes in GeTe thin films on silicon have been studied in situ as a function of temperature by optical curvature measurements. Crystallization of the initially amorphous layers is evidenced by a steep tensile stress buildup. The crystallization temperature is shown to be thickness-dependent for the thinner films. Various annealing conditions, such as cooling/re-heating steps and isothermal stages, allow exploring the thermo-mechanical behavior of the films. A non-thermoelastic temperature-dependent behavior is observed in the amorphous phase before crystallization. Keywords: Phase-change materials, GeTe, Thin films, Stress measurements, Thermomechanical behaviour

Here is presented raw and analysed data collected during study of the evolution, with uniaxial stretching, of the electrical and microcrystalline characteristics of polystyrene sulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) organic electrochemical transistors (OECTs). X-ray diffraction data from GIWAXS measurements of the PEDOT:PSS material, performed at the SOLEIL light source are presented in raw and partially analysed forms. Current-voltage data, collected concurrently with the GIWAXS data, are also presented, and the evolution of the transconductance of the OECT devices with stretching is shown. GIWAXS data are only examined along the qz specular reflection ridge, and scans along this ridge are extracted and presented. However, the off-specular data may also be of interest to readers and is therefore made available here in its entirety.

International audience; Yttrium, Titanium and Yttrium-Titanium getter thin films were elaborated on silicon by co-evaporation in ultra-high vacuum. Y-Ti films exhibit nanometric crystallites size (18-35 nm) leading to a very high grain boundary density, which is a favorable microstructure for an activation at low temperature. The yttrium content in Y-Ti alloys influences grain size, resistance against room temperature oxidation and gettering performance for oxygen. Y-Ti films with an yttrium content higher than 30 % show strong oxygen sorption during annealing at low temperature (< 300 °C). After 1 h of annealing at 250 °C, it was estimated that the yttrium-based getter films can trap between 0.2 and 0.5 µmol of oxygen per cm 2 , while no oxygen sorption was detected for a single metal titanium film. This make Y-Ti getter alloys attractive candidates for the packaging of MEMS under vacuum with a low bonding temperature.

International audience; In this work, we reexamine Ge rejection in Ge-rich GeTe thin films with a slight deviation from stoichiometry using a unique combination of in situ measurements: curvature and x-ray diffraction as well as electrical resistance and x-ray diffraction and reflectivity during annealing. This unique combination of several experiments performed simultaneously on a synchrotron beamline allows to monitor in situ, during the crystalliza-tion and phase transformation, the microstructure, the strain and the stress changes, as well as electrical properties of GeTe films. Structural, electrical and thermomechanical evolutions of the GeTe thin films upon annealing are shown to follow three different steps. Stage I, before crystallization, is characterized by a tensile stress variation and a small decrease of the mass density. Stage II corresponds to the rhombohedral aGeTe phase crystallization leading to an abrupt tensile stress jump (+72 MPa), a mass density increase, and followed by a slight compressive stress evolution. During stage III, Ge crystallization is observed leading to a compressive stress jump (À54 MPa), an abrupt increase in aGeTe lattice spacing and diffracted intensity, whereas aGeTe diffraction peak widths decrease. During cooling a thermoelastic behavior is observed. A detailed analysis of stage III (Ge precipitation and crystallization) is performed and discussed regarding structural , stress, microstrain, electrical and thermomechanical properties. In particular, this study reveals that crystalline Ge precipitation results in important changes (volume of the unit cell, homogeneity of lattice spacing, average stress. . .) in the surrounding GeTe matrix. Different scenarios are proposed to understand these results.

Here is reported the evolution of the transconductance and resistance, along with microstructure, of organic electrochemical transistors (OECTs) under progressively greater strain. A decrease in transconductance and increase in resistance over several orders of magnitude are reported for strains up to 75%. These changes in electrical characteristics are correlated with changes in the microstructure of the PEDOT:PSS characterised by a positive shift, and reduction in amplitude, of the characteristic (100) peak of the grazing incidence wide-angle X-ray scattering (GIWAXS) profile, recorded in tandem with the electrical characteristics during stretching. The (100) peak is associated with the lamella stacking of the PEDOT and PSS chains, and it is shown that this lamella spacing is reduced by up to around 3.5 A on application of strain up to 75%.

In 3-D integration, dice are vertically interconnected with through silicon via (TSV), which consist of holes etched in a thinned silicon substrate and filled with copper. This process induces thermal strain in surrounding silicon. New trends in 3-D integration imply the fabrication of Si photonic devices like waveguides in silicon-on-insulator (SOI) substrates containing TSVs. Thus, a quantitative analysis of strain in active areas around TSVs is mandatory. In this paper, the strain induced by the TSVs in both the bulk silicon and the SOI layer was investigated by using advanced scanning X-ray nano-diffraction. The crystallographic orientation offset between the separated silicon areas allows decorrelation of the strain in the Si layer of the SOI and Si substrate. Using synchrotron radiation, 2-D quicK continuous mapping of the strain in a region of 50 $ \mu \text{m}\,\, \times $ 50 $ \mu \text{m}$ with 500 nm spatial resolution was performed around a single TSV at room temperature and during in-situ annealing at 460 °C. The strain field induced by the TSV appears negligible in both silicon areas. The effect of in-situ annealing on the strain distribution is surprisingly weak. In the SOI active layer, the strain map mimics the surface pattern generated by the photonic devices processed at high temperature in this thin layer.

International audience; In this work, in-situ studies of organic thin films under stretching are developed. A high efficiency PffBT4T-2OD π-conjugated polymer (PCE11) was coated directly on a stretchable substrate in order to examine the impact of tensile strains on the structural properties. For that purpose, in-situ grazing incidence X-ray diffraction (GIXD) coupled with optical microscopic observations have been carried out to measure the structural parameters of PCE11 and to probe the mechanical behavior of polymer chains under uniaxial tensile load. It is observed that in the range between 0 and 15%-20% of stretching, the polymer chains become more oriented. Meanwhile an increase of negative values of deformation i.e. compression of the polymer chains along the film normal was measured. Beyond this range of stretching, the polymer order declined and the stress was relaxed. This relaxation is explained by the increased number of cracks spreading over the entire film as observed by optical microscopy.

International audience; Structure determination in high performance polymer semiconductors such as polythieno[3,4‐b]‐thiophene‐co‐benzodithiophene (PTB7) is essential to establish proper structure–property correlations. A combination of high‐temperature rubbing and isothermal crystallization leads to oriented and crystalline films of face‐on oriented PTB7 crystals. Electron diffraction indicates that crystallinity is marginal in the rubbed films but develops upon postrubbing annealing at T ≥ 250 °C. The best oriented and crystalline PTB7 films have a dichroic ratio of 12 for UV–vis absorption. The hole mobilities are improved by a factor of six along the rubbing direction over nonaligned films (µ// = 5.8 × 10$^{−3}$ cm$^2$ V$^{−1}$ s$^{−1}$ vs µ⊥ = 3.1 × 10$^{−4}$ cm$^2$ V$^{−1}$ s$^{−1}$). Structural analysis yields three possible models that share similar structural features, however; namely (i) PTB7 chains form a layered packing such as poly(2,5‐bis(3‐dodecyl‐2‐yl)thieno[3,2‐b]thiophene) with $\pi$‐stacked backbones alternating with layers of strongly interdigitated alkyl side chains, (ii) the PTB7 chains adopt a nonplanar zigzag conformation, and (iii) PTB7 chains show a mixed stacking of thieno[3,4‐b]thiophene and benzodithiophene blocks. Overall, these results highlight the key role played in polymer semiconductor crystals by the steric constraints due to the branched alkyl side chains interdigitation on the π‐stacking of conjugated backbones.

International audience; The influence of annealing temperature on the structural and electrical properties of conjugated poly(dodecyl-quaterthiophene) (PQT-12) polymer films is exploited. The temperature induced changes of structural parameters are monitored by in situ grazing incident X-ray diffraction (GIXD) and the conductivity. They are complemented by studies of the dielectric properties using variable angle spectroscopic ellipsometry (VASE). An increase of the scattered intensity, the size of the crystalline domains, and the current response is observed for a first thermal cycle with stepwise heating up to 90 degrees C, which revealed two polymorphs with different degrees of interdigitation in PQT-12. Irreversible changes are observed for the second cycle with a higher thermal budget up to 140 degrees C and are connected with a transition from the highly ordered to powder-like disordered phase for the main PQT-12 form whereas the second polymorph with stronger interdigitation completely vanished. In agreement with these observations high-temperature VASE studies demonstrated a blue shift of the transitions with a reduction in the conjugation length caused by an increase in the twist and torsion of the backbone. Combined GIRD, VASE, and electrical characterizations show that PQT-12 exhibits a complex interplay between two polymorphs with a strong influence on the charge carrier transport depending on the thermal budget employed.

International audience

In 3D integration, interconnections between stacked dies are ensured by conductive through silicon vias. Electrical conduction is achieved via coating the vias sidewalls with a metal, such as tungsten. In this work we have compared thermal-dependent stress of thin tungsten films deposited either in full plate oron vias sidewalls. The comparison of stress measurements at room temperature and during heating cycles reveals large differences between full plate and vias samples. At room temperature, in the vias samples, the stress is a factor 4 less than it is in the full plate sample, with both values indicating a tensile stress. While a thermo-elastic behavior is expected for the full plate sample, no stress evolution as a function of temperature is observed in the case of the vias samples.

Molecular Beam Epitaxy (MBE) grown, 50-800 nm thick SiGe layers on Si are studied by two X-ray complementary techniques: imaging (X-ray topography) and High Resolution X-Ray Diffraction. The measured relaxation rates are spreding from as low as 0.01% to over 70%. These results are examined through the main models for critical thickness tc calculation, the Matthews and Blakeslee approach concerning misfit dislocations (MD) development from existing dislocations and the People and Bean model for homogeneous MD nucleation. The beginning step of the relaxation is found to fit exactly with the People and Bean model, otherwise larger relaxation is reached after an intermediate weak relaxation stage. This leads to a refined approach of the critical thickness: a critical band [t, t] Comparison between observed t and calculated tc indicates that the lower limit of this band can be predicted by equilibrium models, the upper one being linked with multiplication stages (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

24th Workshop on Materials for Advanced Metallization held Jointly with the International Interconnect Technology (IITC) Conference, Grenoble, FRANCE, MAY 18-21, 2015; International audience; The strain distribution induced by TSVs is extensively studied in silicon by using submicron resolution synchrotron X-ray diffraction techniques. Simulations with finite elements are performed to interpret the experimental strain results. Stress and strain in silicon are found to be small at room temperature (

International audience; Single crystal Silicon (Si) layers have been deposited by molecular beam epitaxy on double-layer porous silicon (PSi). We show that a top thin layer with a low porosity is used as a seed layer for epitaxial growth. While, the underlying higher porosity layer is used as an easily detectable etch stop layer. The morphology and structure of epitaxial Si layer grown on the double-layer PSi are investigated by high resolution X-ray diffraction and transmission electron microscopy. The results show that, an epitaxial Si layer with a low defect density can be grown. Epitaxial growth of thin crystalline layers on double-layer PSi can provide opportunities for silicon-on-insulator applications and Si-based solar cells provided that the epitaxial layer has a sufficient crystallographic quality.

The influence of local strain fields on electrical properties such as the mobility of electrons and holes in silicon is of growing concern. In this work, we consider the displacement field generated in a semi-infinite Si substrate by a periodic array of lines located at the surface. We focus on a model system: an array of silicon nitride lines deposited on a monocrystalline silicon substrate. Measurements with X-ray diffraction (XRD) need mechanical modeling to validate the strain field. For that purpose we use finite element modeling (FEM) for simulating the displacement field, which is then used for calculating the diffracted intensity in the kinematical approximation. Agreement between measured and calculated intensity allows for a validation of the calculated strain field in the silicon.

Germanium tin (GeSn) is under equilibrium a two phase (Ge + Sn) system. Single phase GeSn alloys are important for silicon based heterostructure devices as stressors for Ge channels and as candidates for direct/indirect band cross-over. Such alloys would allow superior Ge channel metal oxide semiconductor devices and optoelectronic infrared circuits on a Si substrate. Preparation of GeSn layers is possible at low growth temperatures. We discuss the challenges caused by the non-equilibrium growth and the limitations of low temperature epitaxy. Main challenges and limitations are the surface segregation, precipitations and defect accumulation in low temperature epitaxy. The problem of high lattice mismatch between Si and GeSn (> 4%) can be solved using virtual substrates with strain relaxed Ge buffer layers. The lattice mismatch can be reduced to 1% and below. Growth of pseudomorphic GeSn layers on Ge buffers/Si substrate was investigated. The samples were characterized by X-ray methods and Raman spectroscopy. High device process stability was achieved up to 600 °C annealing and documented by Raman spectroscopy. Fabrication of a detector test device demonstrated feasibility for optoelectronic applications with extended infrared range.

The periodic strain induced in mono-crystalline Si lines isolated by the Shallow Trench Isolation process is investigated by High-Resolution X-ray diffraction which is very sensitive to local strain and is non-destructive. The array periodicity gives rise to satellites in the reciprocal space around the Si Bragg peak, their envelope being directly linked to the local strain field. In the particular case of sub-micrometric arrays, the reciprocal space maps present a secondary diffraction peak caused by a homogeneous strain area in the middle of the Si lines. The secondary intensity relative position can be translated in transverse and perpendicular strain values, which allows a quantitative comparison of samples. We first compare two process flows to show the effect of top-layer deposition on Si strain. Then, the influence of geometrical variations is studied for the softer process. When considering a fixed period, the strain is getting higher for a lower Si line/SiO2 trench width ratio. The trenches depths variation shows a few effects on the strain values; the decrease in strain with decrease in depth is only noticeable for the transverse value. Finally, the homogeneous strain values increase with decrease in period from 580 nm down to 200 nm. All these results confirm that most of the stress is applied to the Si-active areas by the trenches filled with SiO2.

In the framework of the development of strained channel materials, the mechanical stress induced in silicon by a silicon nitride stressor layer is studied. The investigated samples are sub-micrometric periodic arrays of polysilicon lines deposited on thermally oxidised single crystal (0 0 1) Si substrate and capped with silicon nitride. We compare the stress induced in the silicon substrate by three layouts: without Si3N4, with a tensile Si3N4 or with a compressive Si3N4 layer on top of the poly lines. The periodic strain field in silicon is investigated by high resolution X-ray diffraction which is very sensitive to local strain (

The processing of Si-based devices induces very high local strains in silicon. This strain field is worth investigating in particular in Shallow Trench Isolation, which is a key step in the production of non-volatile-memories and transistors. In this study we investigate by high high-resolution X-ray diffraction the periodic strain field induced in silicon by the STI process. High-resolution X-ray diffraction is shown to be very sensitive ( − 4 ) to local strains and has the distinct advantage of being non-destructive. Investigated samples are periodic arrays of SiO 2 -filled trenches in single crystal (001) Si. The trenches are etched either along [100] or along [110]. The experiments have been performed on a 4 circles goniometer with a laboratory source. We have recorded Si 004 and asymmetric Si 224 or Si 404 reciprocal space maps in order to extract axial strains in the 3 directions. The trenches array induces a periodic strain field in silicon, which gives rise to distinct satellites in reciprocal space. The intensity of these satellites is related to the strain field. We also performed elastic calculations with a finite element modelling code. Finally structure factor calculations are performed using the displacement field determined from mechanical modelling. We focus here on the effect of silicon elastic anisotropy on the strain field in 580 nm and 200 nm period samples. The influence of line crystallographic orientation ([100] or [110]) on the strain field is evaluated by finite element modelling and compared with experimental ones. The silicon anisotropy has a weak effect on strain and is compensated by process variations due to the line orientation.

Die-level warpage is a challenging issue affecting silicon interposer assembly yield. Stress management strategies are required to compensate residual and thermo-mechanical stress occurring during silicon interposer integration and die stacking processes. In this work, die-level curvature is measured using shadow moire interferometry during a thermal cycle at several process steps. Finite element modeling aims at understanding the curvature behavior observed experimentally and then at proposing warpage compensation strategy. It is found that back-side dielectrics deposited at low-temperature have a critical impact on die curvature magnitude, compared to other layers typically found in Si interposer. On the contrary, organic passivation plays a minor role despite a high coefficient of thermal expansion. Experiments are carried out on Si-bulk and SOI substrates: in the case of SOI substrates, optimized compressive stress regime in the BS layers counteracts the residual stress in front-side layers, especially the compressive stress of the BOX alone. This configuration puts under appropriate conditions a large silicon interposer for subsequent packaging steps.

TSV-induced stress is extensively studied in silicon interposer by using two different submicron resolution x-ray diffraction techniques. Simulations are performed to interpret the experimental strain results. Stress and strain in silicon are found to be small at room temperature, while measurements and simulations at annealing temperature (400 °C) support a plastic behavior of copper in some regions of the TSV.

Strain in silicon induced by Through-Silicon Via (TSV) integration is of particular interest in the frame of the integration of active devices in silicon interposer. Nano-focused X-ray beam diffraction experiments were conducted using synchrotron radiation to investigate the thermally induced strain field in silicon around copper filled TSVs. Measurements were performed on thinned samples at room temperature and during in situ annealing at 400 °C. In order to correlate the 2D strain maps with finite elements analysis, an analytical model was developed, which takes into account beam absorption in the sample for a given diffraction geometry. The strain field along the [335] direction is found to be in the 10−5 range at room temperature and around 10−4 at 400 °C. Simulations support the expected plastification in some regions of the TSV during the annealing step.

Display Omitted 2D strain maps in Si around TSV performed using high resolution fast scanning XRD.Strains in 335] crystallographic direction are small - in the order of 10-4.Low impact of TSV process on carrier mobility variations close to the TSV at RT.3D finite element analysis of a TSV structure compare well with experimental data.Gradient of strains in 335] direction close to the sample surface. Fast-scanning X-ray microscopy is used to directly visualize the local strain and lattice tilt in the silicon neighboring Through Silicon Vias (TSVs). Strain variations of the order of 10-4 were detected and results show that the silicon is slightly strained at room temperature ( | e 335 | < 0.06 % ) with maximum close to the oxide/copper interface, after the completion of copper filled TSVs process. Finite element analysis was carried out and compared with experimental data obtained with synchrotron X-rays. Using the elements birth and death technique with commercial software ANSYS, 3D strains are simulated in a complete TSV structure. Numerical results are in good agreement with extracted strains from diffraction data.

Thermo-mechanical stress is a major concern in the frame of 2.5D integration. Passive stress sensors were integrated in a silicon interposer test vehicle to quantify stress at critical locations. The sensors were integrated in a rosette-shape consisting of eight oriented copper serpentines acting like strain gauges. This innovative design allows the calculation of a partial stress tensor, including three planar and one out-of-plane components. Electrical measurements at wafer level, combined with FIB/SEM cross-sections, revealed a strong impact of elaboration processes on the structures electrical characteristics. Numerical simulations using finite element analysis were built to evaluate the sensitivity of copper serpentines to mechanical stress. Finally a dedicated four-point bending tool coupled with a four-terminal resistance measurement setup was fabricated to experimentally extract the values of sensors sensitivity factors. Preliminary results depicted in this paper highlight a sensitivity to stress of distinctly oriented resistors. Several identified sources of data dispersion are inherent to the present measurement configuration. Added-value and limitations of such sensors were underlined, and recommendations regarding the testing strategy were drawn to allow a reliable estimation of the stress fields.

Made available in DSpace on 2018-12-11T16:50:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-10-28 The compositional dependence of the piezoelectric properties of self-polarized PbZr1-xTixO3 (PZT) thin films deposited on Pt/TiO2/SiO2/Si substrates (x = 0.47, 0.49 and 0.50) was investigated by in situ synchrotron X-ray diffraction and electrical measurements. The latter evidenced an imprint effect in the studied PZT films, which is pronounced for films with the composition of x = 0.50 and tends to disappear for x = 0.47. These findings were confirmed by in situ X-ray diffraction along the crystalline [100] and [110] directions of the films with different compositions revealing asymmetric butterfly loops of the piezoelectric strain as a function of the electric field; the asymmetry is more pronounced for the PZT film with a composition of x = 0.50, thus indicating a higher built-in electric field. The enhancement of the dielectric permittivity and the effective piezoelectric coefficient at compositions around the morphotropic phase boundary were interpreted in terms of the polarization rotation mechanism and the monoclinic phase in the studied PZT thin films. Aix Marseille Univ Univ Toulon CNRS IM2NP Synchrotron SOLEIL L'Orme des Merisiers, Saint-Aubin-BP 48 Universidade Federal Do Tocantins São Paulo State University (UNESP) School of Natural Sciences and Engineering Department of Physics and Chemistry Department of Physics CICECO-Aveiro Institute of Materials University of Aveiro ITMO University IM2NP UMR 7334 CNRS Aix-Marseille Universite Faculte des Sciences Campus de St Jerome, Case 262 Avenue Escadrille Normandie Niemen São Paulo State University (UNESP) School of Natural Sciences and Engineering Department of Physics and Chemistry

Passive stress sensors have been integrated in a silicon interposer test vehicle to investigate thermo-mechanical stress in a typical 2.5D system. The present sensors are integrated in a rosette-shape consisting of eight oriented copper serpentines acting like strain gauges. An innovative design allows theoretically the calculation of a partial stress tensor, including three planar and one out-of-plane components. Electrical measurements at wafer level, combined to FIB/SEM cross-sections, revealed a strong impact of elaboration processes on the structures electrical characteristics. Numerical siumations using finite element analysis were built to evaluated the theoretical sensitivity of copper serpentine to mechanical strains. Finally a dedicated four-point bending tool coupled with a four-terminal resistance measurement setup was fabricated to extract experimentally the values of sensors sensitivity factors. Preliminary results depicted in this paper highlight a sensitivity to stress of distinctly oriented resistors. Several identified sources of data dispersion are inherent to the present measurement configuration and prevent a reliable calculation of strain gauges so-called “gauge factors”.

We investigate the retrieval of spatially resolved atomic displacements via the phases of the direct(real)-space image reconstructed from the strained crystal's coherent x-ray diffraction pattern. We demonstrate that limiting the spatial variation of the first and second order spatial displacement derivatives improves convergence of the iterative phase retrieval algorithm for displacements reconstructions to the true solution. Our approach is exploited to retrieve the displacement in a periodic array of silicon lines isolated by silicon dioxide filled trenches., Comment: 30 pages, 7 figures

International audience; The growth of heteroepitaxial planar fully strained SiGe layers with high Ge concentration and large thickness enables tailoring electronic properties for enhanced transport properties and photoemission. We give here the first experimental and theoretical proof that high temperature flashed porous silicon layers (HT-PSi) perfectly accommodate the stress of SiGe layers and provide compliant substrates with unprecedented capabilities for the fabrication of planar SiGe nanomembranes. We show that the stress driven morphological evolution leading to self-organized quantum dots commonly observed on nominal Si (001) is fully inhibited when growing SiGe on such a HT-PSi substrate. The elastic behavior of HT-PSi results from two specific features: It is ten times softer than Si and tensily strained. Theoretical analysis proves that the compliant behavior of HT-PSi is due to the strain effect, while on the contrary its elastic softness favors the development of 3D growth. The inhibition due to the tensile strain produces atomically flat layers free of misfit dislocation.

International audience; Thick porous silicon (PS) buffer layers are used as sacrificial layers to epitaxially grow planar and fully relaxed Ge membranes. The single crystal Ge layers have been deposited by molecular beam epitaxy (MBE) on PS substrate. During deposition, the pore network of PS layers has been filled with Ge. We investigate the structure and morphology of PS as fabricated and after annealing at various temperatures. We show that the PS crystalline lattice is distorted and expanded in the direction perpendicular to the substrate plane due to the presence of chemisorbed –OH. An annealing at high temperature (> 500 °C), greatly changes the PS morphology and structure. This change is marked by an increase of the pore diameter while the lattice parameter becomes tensily strained in the plane (compressed in the direction perpendicular). The morphology and structure of Ge layers are investigated by transmission electron microscopy, high resolution X-ray diffraction and atomic force microscopy as a function of the deposition temperature and deposited thickness. The results show that the surface roughness, level of relaxation and Si-Ge intermixing (Ge content) depend on the growth temperature and deposited thickness. Two sub-layers are distinguished: the layer incorporated inside the PS pores (high level of intermixing) and the layer on top of the PS surface (low level of intermixing). When deposited at temperature > 500 °C, the Ge layers are fully relaxed with a top Si1 − xGex layer x = 0.74 and a very flat surface. Such layer can serve as fully relaxed ultra-thin SiGe pseudo-substrate with high Ge content. The epitaxy of Ge on sacrificial soft PS pseudo-substrate in the experimental conditions described here provides an easy way to fabricate fully relaxed SiGe pseudo-substrates. Moreover, Ge thin films epitaxially deposited by MBE on PS could be used as relaxed pseudo-substrate in conventional microelectronic technology.

Thermo-mechanical stresses have proven to be a critical issue in a typical interposer integration and assembly flow. However the nature of passive interposer makes the integration of MOS-based stress sensors impossible. New methods are required. Using a coupling strategy between 3D Finite Element Models (FEM) and physical characterization, a method based on electrical measurement of passive stress sensors is presented here to assess stress at die- and wafer-level. Innovative combination of passive stress sensors based on rosettes of serpentine resistors have been developed and embedded to quantify local strain states in a typical interposer die. Their principle and implementation at a copper interconnect level of interposer are presented in this paper. Preliminary results are depicted, including first electrical measurements of these sensors. Electrical characterization has been performed after the back-side interconnection fabrication of the interposer. A local sensibility of each copper serpentine is highlighted. Discrepancies in the resistance values of orthogonal resistors could indicate local deformations to the environment of sensors, such as TSV's and bump pads. However, the order of magnitude of relative variation of resistance values is unexpectedly high and requires further investigations.

International audience; Porous silicon (PSi) layers are used as templates to grow epitaxial planar and fully relaxed Ge pseudo-substrates. An annealing at 600 °C, dramatically changes the PSi morphology and produces compliant template layers which serve in a second step, as substrate for the epitaxy of fully relaxed SiGe layers with a Ge content between 50% and 94%. The SiGe pseudo-substrates produced by such process exhibit a remarkable planar surface resulting from the penetration of Ge inside the pores. They could be integrated into conventional microelectronic technology for the subsequent deposition of active layers such as tensily strained Si or relaxed Ge.

Measuring stress and strain, induced by nanostructures, at the nanometer scale is still a challenge. In this work, we investigate the strain induced by sub-micrometric periodic line arrays deposited on single crystal (001) Si substrate. We study the influence of the lines width and the spacing between the lines for two sets of samples: a silicon nitride lines array and a poly-silicon line array capped with a Si3N4 stressor layer. The periodic strain field in mono-crystalline silicon is investigated by High Resolution X-ray Diffraction which is very sensitive to local strain (< 10(-4)), has the required resolution, and is non-destructive. X-ray reciprocal space maps (RSM) are measured on a 4 circles goniometer with a laboratory source. The line arrays induce a periodic strain field in silicon, which gives rise to distinct satellites in reciprocal space. The intensity envelope of these satellites is related to the strain field in one cell. In order to assess this strain field in silicon, mechanical modeling is necessary. Elastic calculations are performed with a Finite Element Modeling (FEM) code in order to extract the displacement field that is used for structure factor calculations within kinematical approximation. The calculated reciprocal space map is compared to the experimental results in order to validate the strain field. We show that for capped poly arrays, the diffracted intensity envelope is influenced by the spacing between the lines. This area is filled with silicon nitride which induces a noticeable change in displacement and strain field. While for bare stressor arrays the nitride line width is responsible of change in displacement field and thus on the RSM intensity envelope.

Metastable and strain relaxed SiGe layers with about 20% Ge content have been grown by molecular beam epitaxy on Si substrates at 550 °C. The thickness regime of metastability and the onset of strain relaxation were investigated on dust particle free surfaces obtained by careful chemical cleaning and epitaxy loading under clean room conditions. Compared to earlier results true metastable regime without misfit dislocations was obtained up to 140 nm thickness. The onset of strain relaxation started with heterogeneous nucleation sites of misfit dislocations. X-ray topography proved to be a unique monitoring tool to observe a low density of single dislocations. From these results we suggested to define a critical thickness band with lower bound tcl from dislocation nucleation to an upper bound tco (600 nm in our case) defined by the onset of considerable strain relaxation. The strain relief was measured by X-ray diffraction (reciprocal space mapping) and found to be very abrupt (76% strain relaxation at 800 n...