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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.

This paper presents the mechanical characterization of membranes micromachined in bulk-titanium wafers, which can be future parts of various Ti-based MEMS such as pressure sensors or microvalves for corrosive environment. One membrane was characterized by microbending using a mechanical microprobe. Two membranes were characterized by vibrometry using microscopic interferometry, and the residual mechanical stress could be derived from these measurements. These are key experiments for successful design of future Ti-based MEMS.

We report the fabrication and characterization of two kinds of titanium membranes made of bulk titanium. Both membrane designs are compared mechanically to define the most suited for the targeted application. These membranes are future parts of Ti-based MEMS pressure sensors for active biomedical implants. As pressure is known to be linked to patient’s health for numerous diseases (glaucoma, heart failure, hydrocephalus...), in vivo pressure monitoring appears as a promising way to help medical doctors to define their treatments. Yet, most of current methods used to monitor pressure are still routinely invasive, which increases the risk of infection. The use of Ti as a mechanical transducer appears as a promising approach to tackle the lack of biocompatibility of standard semiconductor materials such as silicon, which requires a complex, bulky and costly packaging.

In this work, we investigate Au/Zr/V/Zr multilayer getters in order to get a sustainable low pressure in a packaging cavity. These films were analyzed by using four probe resistivity measurements, SEM and TEM cross section observations and Energy Dispersive X-Ray Spectrometry (EDX) measurements. It is demonstrated that the activation temperature of a zirconium layer covered with a vanadium layer depends on the vanadium layer thickness. Other experiments demonstrate that Au/Zr/V/Zr multilayer getter films can be activated at low temperature and that suitable sorption properties to get a low pressure in a medium size vacuum package during 9 months can be achieved after activation at 300°C for 1 hour.

Some applications require MEMS devices to be packaged in a high vacuum environment, for example, high-quality factor mechanical micro-resonators or low heat loss microbolometers can only be obtained in a vacuum better than 10-3 mbar [1-2]. For this purpose, many Non-Evaporable Getter (NEG) multilayers or alloys films based on sputtered highly reactive transition metals have been investigated. For example, R.K. Sharma [3] found the Ti21Zr24V55 getter and O.B. Malyshev [4] found the Ti-Zr-Hf-V getter can be activated at 160 °C for 2 hours and 150 °C for 24 hours respectively. The getter function after its thermal activation is to absorb gases generated inside the packaging cavity by outgassing, permeation and by real and virtual leaks after packaging cap sealing by a highly hermetic bonding process. In this work we investigate Au/Zr/V/Zr getter multilayers in order to get a sustainable low pressure in a packaging cavity. All films were initially deposited by e-beam evaporation on 100 mm in diameter Si（100）wafers. The samples of Au/Zr/V/Zr were deposited in an ultra-high vacuum set-up with a background pressure of 2 10-10 mbar. To investigate their activation and oxidation by gas sorption at typical pressures found in packaging cavities, the films were annealed for 1 hour at various annealing temperatures in a rapid thermal annealing (RTA) chamber (Jipelec Jetfirst 100) at a vacuum level 10-2 mbar. Then, these films were analyzed by using four probe resistivity measurement, SEM and TEM cross section observations, EDX measurement and SIMS. All results are consistent and support that the activation temperature of zirconium under vanadium depends on vanadium layer thickness. For example, a 25nm zirconium oxide layer is found under the vanadium film after annealing at 300°C for 1h when the vanadium thickness is less than 200nm. However, for a 450nm thick vanadium layer, the 1-hour annealing temperature must reach 350°C to obtain the same thickness of zirconium oxide layer. Next, these annealed Au/Zr/V/Zr getters were exposed to air at room temperature for 7 months. After this exposure, the sheet resistance was found to increase by 6 % and 15 % for samples annealed at 250°C-1h and 300°C-1h respectively. TEM cross section observations of these samples showed that the thickness of the zirconium oxide layer under vanadium increases by about 3 nm. Finally, to evaluate its sorption ability in a real application case, the Au/Zr/V/Zr getter film was integrated in the 1.3 cmx1.3 cmx2.5 mm packaging cavity of a resonant gyroscope and activated at 300°C for 30 min before cavity sealing by Au/Sn bonding at 285°C for 30min. The time dependence of the pressure inside the packaging was evaluated from the variation of the quality factor Q of a selected mechanical resonance of the gyroscope. Quantitative values of the internal pressure were obtained owing to a previous calibration of the Q versus pressure curve that was in agreement with a squeeze film damping model. The evaluated pressure inside the cavity was 4.5 x10-3 mbar after annealing, 3x10-3 mbar after 2 weeks, and then this vacuum level still maintained after 6 months. In conclusion, this work demonstrates that Au/Zr/V/Zr getter films have a low activation temperature and suitable sorption properties to get a sustainable low pressure in a medium size vacuum package. [1] M. Elßner, Vacuum quality evaluation for uncooled micro bolometer thermal imager sensors, Microelectronics Reliability 54 (2014), 1758. [2] G.-D. Anna, Miniature and MEMS-type vacuum sensors and pumps, Vacuum 82 (2009), 1419. [3] R.K. Sharma, Jagannath, S. Bhattacharya, R.B. Tokas, K.G. Bhushan, S. Sen, S.C. Gadkari, S.K. Gupta, Journal of Alloys and Compounds 651 (2015) 375-381. [4] O.B. Malyshev, R. Valizadeh, R.M.A. Jones, A. Hannah, Vacuum 86 (2012) 2035-2039.

International audience; This paper reports on progress in the analysis of time-domain optical coherence tomography (OCT) applied to the dimensional metrology of through-silicon vias (TSVs), which are vertical interconnect accesses in silicon, enabling three-dimensional (3D) integration in microelectronics, and estimates the deviations from earlier, simpler models. The considered TSV structures are 1D trenches and circular holes etched into silicon with a large aspect ratio. As a prerequisite for a realistic modeling, we work with spectra obtained from reference interferograms measured at a planar substrate, which fully includes the dispersion of the OCT apparatus. Applying a rigorous modal approach, we estimate the differences to a pure ray tracing technique. Accelerating our computations, we focus on the relevant fundamental modes and apply a Fabry–Perot model as an efficient approximation. Exploiting our results, we construct and present an iterative procedure based on the minimization of a merit function, which concludes TSV heights reliably, accurately, and rapidly from measured interferograms.

Transition metals alloys are the most studied getter films for wafer-level vacuum packaging of MEMS. In this work we investigated yttrium and YxTiy alloys films that could possibly overcome the limitations of usual getter materials, i.e. reversible sorption of hydrogen and low sorption ability for hydrocarbon gases. As a preliminary step towards this objective, properties of (co-)evaporated yttrium and YxTiy films were analyzed by SEM, EDS, XPS and in-situ sheet resistance measurements before, after and/or during annealing in vacuum. As deposited and annealed films have a small grain size and a columnar structure. It is shown that yttrium and YxTiy films can be activated after 1 hour of annealing in vacuum at 250 °C if the Y-content is larger than ∼9 %. These results are promising for the use of Y-based films as low temperature getters for vacuum packaging.

International audience; Gettering properties of thin films of pure yttrium and yttrium-based alloys have been studied for application to MEMS vacuum packaging at the wafer level. Thin films of Y, Zr-Y, Ti-Y and V-Y were co-evaporated under ultra-high vacuum. It is demonstrated that the sheet resistance measured by 4-probes technique before and after activation at 250°C gives a good estimation of the oxygen sorption ability determined by NRA. Pure yttrium has been found to be highly reactive after deposition (sheet resistance increases by 40% after 1 month in air) but poorly efficient in oxygen trapping after activation. Conversely, the sorption ability of Y-V, Y-Zr and Y-Ti alloys is extremely high and increases with the yttrium content in the film. The bests results for sorption are obtained with Y-V (2.7 10 22 atom/cm 3 for Y44V56).

In this work, thermal diffusion of titanium, vanadium and zirconium through a thin capping gold layer has been investigated and compared in terms of oxygen gettering ability after activation at low temperature. The films were characterized by means of sheet resistance measurements, high resolution Scanning Electron Microscopy, Ion Beam Etching coupled with Secondary Ions Mass Spectrometry, X-ray diffraction, X-ray photoelectron spectrometry and mechanical stress measurements. Results show that, among investigated bilayers, gold/zirconium system is the best candidate to get low temperature getter film as its activation temperature is below 200 °C for 1 h annealing time.

International audience; We report on progress in Time-Domain OCT (optical coherence tomography) applied to TSV (vertical interconnect accesses in silicon, enabling stacking of devices). Transitioning from the common scalar approach to an electromagnetic one, and combining it with a damped least squares approach, we enhance the accuracy of TSV height measurements.

International audience; Immunoglobulins, such as immunoglobulin G (IgG), are of prime importance in the immune system. Polyclonal human IgG comprises four subclasses, of which IgG1 and IgG2 are the most abundant in healthy individuals. In an effort to develop an absolute MALDI-ToF-MS quantitative method for these subclasses and their Fc N-glycoforms, (glyco)peptides were synthesized using a solid-phase approach and used as internal standards. Tryptic digest glycopeptides from monoclonal IgG1 and IgG2 samples were first quantified using EEQYN(GlcNAc)STYR and EEQFN(GlcNAc)STFR standards, respectively. For IgG1, a similar glycopeptide where tyrosine (Y) was isotopically labelled was used to quantify monoclonal IgG1 that had been treated with the enzyme Endo-F2, i.e., yielding tryptic glycopeptide EEQYN(GlcNAc)STYR. The next step was to quantify single subclasses within polyclonal human IgG samples. Although ion abundances in the MALDI spectra often showed higher signals for IgG2 than IgG1, depending on the spotting solvent used, determination of amounts using the newly developed quantitative method allowed to obtain accurate concentrations where IgG1 species were predominant. It was observed that simultaneous analysis of IgG1 and IgG2 yielded non-quantitative results and that more success was obtained when subclasses were quantified one by one. More experiments served to assess the respective extraction and ionization efficiencies of EEQYNSTYR/EEQFNSTFR and EEQYN(GlcNAc)STYR/EEQFN(GlcNAc)STFR mixtures under different solvent and concentration conditions. Graphical Abstract ᅟ.

The Cu/Sn TLP bonding process is based on the transient liquefaction of the Sn layer. The control of the amount of molten Sn is critical during the bonding process, especially when involving thin bonds and small volume. Indeed, by using thin films deposited by PVD, defect-free bonds can be obtained at 250°C but no liquid Sn is involved in the bonding process and interdiffusion of Cu and Sn begins at temperature as low as 150°C. In this work, Differential scanning calorimetry (DSC) was used to detect melting during annealing of Cu/Sn thin stacks. The effect of an ultra-thin buffer layer (UBL) of Ti between Cu and Sn layers was also investigated. We showed that the amount of liquid phase can be controlled by the thickness of the Ti UBL. The DSC results were confirmed by Cu/Sn and Cu/Ti/Sn wafer bonding experiments at 250°C.

It is demonstrated that high quality stress-induced birefringence maps in silicon with a high lateral resolution can be obtained by microphotoelasticity in reflection mode at wavelength of 1.31 μm. This technique was applied to inspection of Si-Si wafer bonding defects with variable magnifications. It is shown that defects with an apparent size as small as 20μm in diameter can be observed with a 2μm lateral resolution.

Activation of evaporated getter films was indirectly evaluated by characterizing their oxidation. Alloys of Zr-V, Zr-Ti and Zr-Co with different content in Zr were studied. XRD measurements confirmed that the evaporated films have a microstructure suitable for gettering activity: the films are nanocrystalline with a columnar structure. The films were oxidized by a thermal treatment in an Ar atmosphere with traces of O2 and H2O. To evaluate the oxidation degree, sheet resistance were measured by 4-probes electrical measurement and oxygen content in the films was deduced from EDX and XPS analysis. The oxidation of the getter film reflects its oxygen sorption ability, and thus allows evaluating its activation temperature. Estimation of the activation temperature for a 1h15 annealing is 325°C for Zr-Ti getters. For Zr-Co and Zr-V getters, it varies from 320°C to 350°C and 220°C to 270°C respectively, depending on the Zr content in the alloy.

This paper presents the design of a piezoelectric MEMS Coriolis Vibrating Gyroscope (CVG) based on a single gallium arsenide vibrating structure allowing the measurement of rotation rate along 3 orthogonal sensitive axes. Based on a theoretical and FEM study, we demonstrate that the achieved sensitivities reached for each axis is about 1.6 × 10 −16 C/(°/s). We then demonstrate the feasibility of the realization of simple MEMS structures from C-doped Gallium Arsenide (GaAs) using standard micromachining processes. Finally, we show the fabrication and characterization of GaAs-based tuning fork microresonators as a first step towards a complete 3-axis GaAs MEMS CVG. These resonators show a resonance frequency of 42 350 Hz, a quality factor of 122 000 and a frequency temperature coefficient of 24 ppm/°K, validating the high potential of GaAs as a structural material for 3-axis MEMS CVGs.

We present a study of the giant piezoresistance effect in p-type silicon using full-band Monte Carlo simulation based on 30-band k.p calculation. This effect has been demonstrated experimentally in Si nanowires by He and Yang. By including the well-known strain effect on the band structure, and by introducing a law of variation of the surface potential according to the applied mechanical stress, we can reproduce this effect. This variation of surface potential modulates the depletion depth and then the conductivity of the structure. This modulation induces a strong variation of the total amount of carriers available for the conduction, which increases drastically this piezoresistive effect. This is probably the main origin of this effect, which may be used to achieve high performance MEMS sensors.

Interdiffusion in gold/titanium films with titanium evaporated on silicon at different oblique angles (0°, 30°, 50°, and 70°) and gold evaporated under normal incidence is investigated using a scanning electron microscope and in-situ sheet resistance measurements for the optimization of the films' effective gettering ability during and after a low-temperature thermal activation. Films have a tilted columnar structure and a porosity increasing with the deposition angle in agreement with calculated values. The oxygen effective gettering ability, characterized by energy-dispersive X-ray spectroscopy, increases with the deposition angle. It is shown that the gold/titanium film with titanium deposited with an oblique angle of 50° is an optimized condition to obtain the largest sorption capacity after 1 h thermal activation at temperatures lower or equal to 300 °C. This film has a low initial residual stress that becomes highly tensile if thermal activation is performed above 300 °C.

A low cost and low temperature thin film packaging process based on the transfer of an electroplated Nickel 3D cap is proposed. This process is based on adhesion control of a thick molded cap Ni film on the carrier wafer by using a plasma deposited fluorocarbon film, on mechanical debonding and on adhesive bonding of the microcaps on the host wafer with BCB sealing rings. Mechanical characterizations show that the transferred microcaps have a high stiffness, a low stress and a high adhesion. Because this process is simple and only involves a low temperature (250°C) heating of the host wafer, it is highly versatile and suitable for the encapsulation of micro and nano devices, circuits and systems elaborated on a large range of substrate materials.

Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920); International audience; Copper planar microcoils were processed by U.V. lithography on SiO2/Si and Kapton®. The coils were packaged on different supports in order to create varying thermal exchange conditions. The electric current was increased step by step until the electric connection breaks, the microcoils remaining free on a thermal point of view. The copper temperature was estimated from its resistivity. It allowed to show that the thermal exchange mode of the wire-bonded microcoils is conductive. The current density was calculated taking into account the deterioration of the coils by oxidation. Its maximum value is linearly decreasing with the thermal exchange ability of the support. The failure modes of the microcoils are related to track melting and oxidation, the current density remaining one order too weak to induce electromigration.

In this paper, we study the resonance frequency resolution of a MEMS resonator based on suspended piezoresistive silicon nanogauges transduction. Nanowire strain gages are attractive for MEMS resonators thanks to their high sensitivity to motion. They have excellent force sensitivity due to their small cross-section area (250×250nm2) and a negligible footprint. Hence, this transduction mean exhibits a very high signal to noise ratio (SNR) of 115dB above a few kHz, which does not limit the excellent resolution frequency required for high performance applications. Thus, resolution frequency down to 35 ppb is here reported, limited by thermo mechanical fluctuations, instrumentation noise and environment stability. Influence of various actuations and damping conditions are investigated and then compared to the Robins' law that estimates resolution for the frequency measurement. Thus, Robin's law is validated for the nanogauge transduction of a MEMS resonator. Eventually, these results can be used to anticipate the outstanding frequency resolution of an ongoing resonant pressure sensor, which has been estimated at only a few ppb.

Tubulobulbar complexes (TBCs) are elongate subcellular machines responsible for internalizing intercellular junctions during sperm release. Each complex consists of a double-membrane tubular core terminating in a clathrin-coated pit. The core is surrounded by a network of actin filaments, and a distinct swelling or bulb, which lacks an association with actin, develops in the distal third of the structure. The bulb eventually buds from the complex and enters endocytic compartments of the Sertoli cell. The relationship of the actin cuff to the formation and budding of the bulb is not known. To gain insight into this relationship, we perturbed the actin networks of TBCs with cytochalasin D. When isolated testes were perfused with a physiological buffer containing cytochalasin D, apical TBCs at stage VII of spermatogenesis were associated with lower levels of actin compared to controls. At the ultrastructural level, the actin networks in cytochalasin D-treated testes appeared patchy, and ectopic bulbs and swollen tubular regions occurred. When normal untreated samples at early stage VII were analyzed, large elongate bulbs and short tubular sections were observed. Together, these results suggest a new model for TBC vesiculation in which the actin network begins to disassemble and the tubular region begins to swell into a bulb. As actin disassembly continues, the coated pit and most of the tubular region are incorporated into the enlarging bulb. The remaining short neck of the bulb near the base of the complex undergoes scission, and the bulb is internalized.

Formation of Cu-Sn intermetallic compounds has been studied with thin Sn and Cu films deposited by physical vapor deposition. The influence of annealing time at 250°C and 320°C highlights a rapid interdiffusion of copper and tin, leading to the formation of Cu 6 Sn 5 and Cu 3 Sn phases. Application to 100 mm wafer bonding has been implemented at 250°C and 320°C, which shows that stress induced by the deposits must be controlled to achieve the bonding on the whole wafer surface.

Endocytic structures known as tubulobulbar complexes internalize intercellular attachments during sperm release. They are elongate structures capped with a clathrin-coated pit. Their membranous cor...

Vacuum encapsulation is required for various microsensors to improve their performances. In the case of wafer level vacuum encapsulation, dedicated techniques must be developed to measure the background pressure in the bonded cavities. In this paper we investigated ex situ measurement techniques based on the measurement by interference microscopy of the deformation and vibrations of the caps as function of an external pressure. Because these techniques detect the equality between external and internal pressure, they do not require any modelling nor prior calibration. Application to wafer level encapsulations fabricated by gold-silicon eutectic wafer bonding demonstrates that a detection limit in the 10−2–10−1 mbar range can be reached for millimetre size caps.

Special attention has been paid in this work to use all possible means to measure an intrinsic quality factor (Q) for silicon beam resonators realized on SOI wafers. Specifically, this work points to the energy dissipation into the support; a model is given and a high insulating system for clamped–clamped and clamped-free configurations has been studied, preserving the resonating element from support damping. Finite element analysis on these structures evidences values of Qsupport higher than 107. Out-of-plane and in-plane vibration Q values up to 1.0 × 105 have been measured under a high vacuum using, respectively, laser Doppler vibrometry and stroboscopic optical microscopy combined with image processing. The results have shown good agreement with thermoelastic theory. However, the observed agreement on the resonator dimension dependences is limited to quality factors lower than 3.0 × 104. Beyond these values, a physical limitation is evidenced in both cases (in-plane and out-of-plane) which does not match with the surface and clamping models listed. The role of the SOI wafer's oxide layer is discussed as a possible source of dissipation.

The future CMOS generations for microelectronics will require advanced doping techniques capable to realize ultra-shallow, highly-doped junctions with abrupt profiles. Recent experiments have shown the potential capabilities of laser processing of Ultra Shallow Junctions (USJ). According to the International Technology Roadmap for Semiconductors, two laser processes are able to reach ultimate predictions: laser thermal processing or annealing (LTP or LTA) and Gas Immersion Laser Doping (GILD). Both processes are based on rapid melting/solidification of the substrate. During solidification, the liquid silicon, which c ontains the dopants, is formed epitaxia lly from the underlying crystalline silicon. In the case of laser thermal annealing dopants are implanted before laser processing. GILD skips the ion-implantation step: in this case dopants are chemisorbed on the Si surface before the laser shot. The dopants are then incorporated and activated during the laser proce ss. Activation is limited to the liquid layer an d this chemisorption/laser shot cycle can be repeated until the desired concentration is reached. In this paper, we investigate the possibilities and limitations of the GILD technique for two different substrat es: silicon bulk and SOI. We also show so me laser doping applications for the fabrication of micro and nanoresonators , widely used in the MEMS Industry. Keywords: laser doping, ultra shallow junctions, impl antation, micro resonator, MEMS, LTP, GILD.

The principle of a multilayer monochromator with a narrow bandwidth and a low specular background is recalled. The elaboration of such a monochromator obtained from a Mo/Si multilau-yer mirror is briefly described. The performance of the device measured at 1500 and 98 eV is presented. Le principe d'un monochromateur multicouche a bande passante etroite et presentant un faible fond continu est rappele. Nous decrivons brievement la fabrication d'un tel monochromateur obtenu a partir d'un miroir multicouche Mo/Si. Les performances de ce dispositif mesurees a 1500 et 98 eV sont presentees.

SixOyNz ,S i 3N4 and SiO2 films deposited on silicon in a low frequency PECVD reactor (187.5 kHz) from a SiH4 ,N 2O and/or NH3 gas mixture are always in compressive mechanical stress state after deposition because of ion bombardment of the growing film during deposition. The stress value is, as expected, a decreasing function of oxygen content. It is demonstrated that by reducing drastically the deposition temperature down to 200 8C, stoechiometric silicon nitride films and silicon oxynitride films (0 � O=Si � 1:8) with a low tensile stress can be obtained after high temperature annealing (800 8C). Rutherford backscattering experiments (RBS), elastic recoil detection analyses (ERDA) and infrared spectrometry measurements show that this stress variation is related to the initial composition, to hydrogen desorption from Si‐H, N‐H and O‐H bonds and to cross-linking. By controlling the initial hydrogen concentration with the deposition temperature, the stress value after annealing can be tuned precisely. This simple process was applied to the fabrication of flat dielectric membranes with a thickness in the range of 90‐400 nm by KOH bulk micromachining. # 2002 Elsevier Science B.V. All rights reserved.

We report results concerning the control of shape memory properties of NiTi thin films deposited on silicon. Films with 1.2 μm thickness were deposited by rf sputtering using a Ti-rich target. All as-deposited films were amorphous after deposition and displayed a titanium deficiency (under 50 at.%). Without removing the substrate, thin films were annealed at 700 °C during 30 min in order to crystallise them and to produce diffusion of nickel into the substrate and silicon into the film. Ternary alloys of Ni x Ti y Si z were then obtained. Shape memory properties of these films were examined by X-ray diffraction measurements at various temperature to evidence the hysteresis of transformation. Typical measured transition temperatures are Ms=58 °C, Mf=35 °C, Af=72 °C and As=60 °C. This result shows that transformation temperatures above room temperature can be obtained from a Ni-rich NiTi film by using interdiffusion of nickel and silicon.

We present a study of the interface between a NiTi film deposited by magnetron d.c. sputtering and a SiO2 film obtained by thermal oxidation. Electron-induced X-ray emission spectroscopy (EXES) is used to characterize the physicochemical environment around the Si atoms at the NiTi/SiO2 interface, and to obtain information about the interfacial reactivity. From analysis of the Si 3p valence states, the composition and the thickness of the interfacial zone before and after annealing are deduced. The composition of the passivation layer, located at the surface of the metallic film, is determined by EXES and X-ray Photoelectron Spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.

A new soft-x-ray multilayer monochromator with an improved resolution and a low specular background is presented. The principles of the device, based on the use of a lamellar multilayer amplitude grating (LMAG), are summarized. The techniques of fabrication of the monochromator (multilayer deposition, UV lithography and reactive ion etching) are given. The performance of this new monochromator at photon energies around 1500 eV is demonstrated. Copyright © 2001 John Wiley & Sons, Ltd.

In this paper, realization process and electroplated copper and permalloy properties are presented in order to fabricate micro-coils. RF electrical and magnetic characterizations of the first devices with 40 turns obtained for low frequencies application are exposed showing an inductive behavior under 220 MHz ( L =320 nH) and a capacitive behavior above. Experimental results are compared with calculations. A comparative magnetic field measurement is performed using micro-coils and AMR.

In this paper, electrodeposition of copper films and copper lines with direct and pulse currents is compared. In the first step, electrical and physicochemical characterizations of the copper films are realized, and the optimized electrodeposition parameters are so determined. The use of pulse reverse current is also investigated. In the second step, these parameters are applied to micromolding. Copper lines are electro-deposited and compared in order to determine the more suitable current mode for micromolding.

In conjunction with a remote-controlled smart-sensors project (Villegas M, Bildstein P and Nicole P 1997 Translateur de frequence micro-ondes pour capteur intelligent autonome Proc. 10eme Journees Nationales Microondes (St Malo, 21-23 May 1997) pp 270-1), this study concerns the validation of a radio-frequency microelectromechanical system combining micromechanical capacitive functions and microwave data communication functions. In this project, we have focused on the back-modulation function used for data re-emission. We decided to develop this function with a microelectromechanical mixer made as a passive microwave frequency shifter using an integrated silicon micromechanical capacitive structure. The principles, together with electromechanical considerations, the technology of the silicon implantation, and some first experimental results are described in this paper. The main interest lies in the characterization of the device: both electrical and mechanical properties are tested in parallel to assist us in improving the system and defining a new micromechanical frequency-translator prototype.

Preliminary results on NiTiCu shape memory alloy thin-film deposition on silicon are reported. Characteristics of these films (composition, density and electrical resistivity) were correlated with working gas pressure and rf power during sputtering. The films were then annealed in order to crystallize them. The properties of these films were examined as functions of annealing and measurement temperatures in order to evidence shape memory behaviour.

We have studied the solid/solid interface between Mo and SiO 2 films deposited, respectively, by magnetron d.c. sputtering and plasma-enhanced chemical vapour deposition (PECVD). The sample depth profile was characterized by SIMS. We used electron-induced x-ray emission spectroscopy to characterize the interface from the valence Si 3p and O 2p spectral densities, which are very sensitive to the physicochemical environment, and the Si 2p → Is transition, which is sensitive to the oxidation degree of the silicon atoms. By gradually decreasing the emissive thickness, which is a function of the primary electron energy, we have shown the presence of an interfacial compound 2-4 nm thick that is not seen by SIMS. We suggest that this compound is an Mo-Si-O mixed oxide in which the silicon atoms have an oxidation degree equal or close to that of silica.

Electrodeposited Ni 80 Fe 20 magnetic films are used in storage devices and are usually used for MEMS. In this paper, we present some fundamental results concerning the influence of electrodeposition conditions on the films characteristics. In the first step, permalloy electrodeposition has been studied on copper evaporated films without resist patterns. The growth rate varies linearly as function of the current density (typically 120 nm min −1 for 10 mA cm −2 ). The variation of the alloy composition with deposition parameters is consistent with the so-called anomalous deposition effect, i.e., a preferential deposition of iron. The composition is the same for films with thickness in the range 0.6–20 μm and the Fe concentration decreases with current density. An alloy Ni 80 Fe 20 with a density close to the bulk value is obtained for a current density of 14.5 mA cm −2 . Characterization of magnetic properties with a vibrating magnetometer shows that good properties can be obtained (coercivity=0.35 Oe for a thickness of 600 nm). These results are applied to the patterning of permalloy by electrodeposition through photoresist molds.

Free standing single-crystal silicon cantilever beams were fabricated by a SCREAM-like process which uses dry etching. Typical dimensions are length 200 μm, width 2–3 μm, thickness 2–3 μm. Cantilever beams were initially upward deflected by depositing a tungsten layer with a tensile stress. The electrostatic vertical actuation of the composite beam is investigated by biasing it with respect to the grounded substrate and lateral driving electrodes. A voltage of 10 V is sufficient to induce a large displacement of the beam free end up to 8 μm. A precise positioning is obtained with a good repeatability.

A new calorimeter especially built for the measurement of the heat release rate and effective heat of combustion of composite materials is pre sented. Two procedures can be used to obtain these data: the first one is based on the direct measurement of the convective and radiant heat liberated by the flame, the second involves oxygen consumption measurement. Preliminary ex periments were carried out with a gas burner to calibrate and check the inertia of the thermal method. In a second step, measurements were performed on PMMA and PVC samples. The results obtained with both methods are very similar and in agreement with literature values.

Silicon-on-insulator (SOI) wafers made by direct wafer bonding are widely used as starting substrates for microelectromechanical systems (MEMS) fabrication. Adding another layer next to the SiO2 SOI, or replacing it with another material, will be a way to tailor the SOI wafers further. Atomic layer deposition (ALD) can be used to deposit pinhole-free nanometer-thin conformal and smooth inorganic films at low temperatures, making it of interest for many applications in MEMS. In this work, the direct wafer bonding of ALD TiO2, and Al2O3 for reference, is investigated, eventually in order to fabricate SOI wafers with buried ALD oxides. Finding suitable process conditions for TiO2 bonding was challenging: bonding could not be made for TiO2 deposited directly on SiO2 or Si, and annealing at 1100°C gave non-continuous Ti-containing layers. Using a 2-nm Al2O3 under-layer and annealing at 700°C gave void-free bonding with continuous TiO2 and a bond strength of approximately 1600 mJ/m2, enabling the fabrication of SOI wafers with buried TiO2.

Electrostatically actuated MEMS devices integrating surface micromachined silicon piezoresistive nanowires were batch processed to investigate a silicon nanowire detection scheme allowing an arbitrary choice of MEMS motion detection range and an increase of nanowire gauge factor measurement stress resolution. It is demonstrated that an in-plane MEMS displacements up to 180 nm with a resolution down to a few Angstroms can be achieved as well as a MEMS resonance detection. Results are compared with ex-situ MEMS optical microscopy and in-situ capacitive measurements of MEMS displacement.

This paper deals with the design and fabrication of a 3-axis Coriolis Vibrating micro Gyro (µCVG), based on a single planar monolithic structure. The presented µCVG design ensures a high mechanical coupling between one single driving mode and each one of the 3 sensing modes when the structure is subjected to Coriolis acceleration, with limited mechanical cross-coupling between vibration modes. The structure is made of a semi-conducting material with a cubic lattice, such as Silicon (Si) or Gallium Arsenide (GaAs). GaAs was particularly investigated for its piezoelectric properties, allowing both the actuation and the detection of the mechanical vibrations.

In MEMS industry, silicon-on-insulator (SOI) wafers are gaining ground from blank silicon wafers as the main starting substrate. Tailored SOI wafers available in the market contain for example buried cavities or a buried gettering layer. Adding another layer in addition to the thermal SiO 2 insulator, or replacing it with another material altogether, could be a way to tailor the properties of SOI wafers further. In this work, the direct wafer bonding of ALD TiO 2 , and Al 2 O 3 for reference, is investigated, eventually in order to fabricate SOI wafers with other buried ALD oxides.

The mechanisms of nitridation of W films by reactive nitrogen neutrals generated form a N 2 multipolar discharge are studied by in situ AES and ex situ NRA in the temperature range 35–500°C. The growth is mainly due to atomic nitrogen and occurs in two steps at room temperature. At higher temperature the nitridation is less effective due to a decrease of the initial sticking coefficient of N on W.

This paper presents simulations and microfabrication of different parts of high fidelity electrodynamic MEMS loudspeakers with high electroacoustic conversion efficiency. The originality of the structure lies on the use of rigid silicon membranes suspended by a whole set of silicon beams instead of flexible polymer membranes usually found in MEMS loudspeakers. The microspeaker structure includes a planar copper microcoil electroplated on the silicon membrane and permanent magnets bonded on the substrate. Microstructure of the silicon membrane was optimized using FEM simulations for providing both rigidity and lightness of the mobile part. The results presented on a deep RIE etched 15 mm diameter silicon membrane structured with 40 stiffening ribs and on a 30 µm thick microcoil with 35 turns experimentally show the feasibility of key stages required for manufacturing of MEMS microspeakers with outstanding properties.

This article presents a study of the giant piezoresistance effect in p-type silicon using full-band Monte Carlo simulation. This effect has been demonstrated experimentally in Si nanowires by He and Yang [1]. By introducing a law of variation of the surface potential according to the applied mechanical stress, we can reproduce this effect. The modulation of the width of the depletion region associated with the variation of surface potential induces a strong modulation of the total amount of carriers available for the conduction, which increases drastically this piezoresistive effect. This is probably the main origin of this effect, which may be used to achieve high performance MEMS sensors.

We show that the recombination energy of the direct band gap photoluminescence of germanium can be controlled by an external mechanical stress. The deformation is provided by an apparatus used for blister test. This strain leads to a significant change of the room temperature direct band gap recombination of germanium. An energy red-shift up to 60 meV is demonstrated for the room temperature photoluminescence of a thin germanium membrane (125 nm wavelength shift from 1535 to 1660 nm). This photoluminescence shift is correlated to the inplane tensile strain present in the film. A biaxial tensile strain larger than 0.6 % is achieved by this method. The wavelength shift is correlated to the predicted band gap shift as obtained from a 30 band k. p formalism. An excellent agreement is obtained between the experimental band gap shift and the theoretical one. This mechanical deformation allows to approach the direct band gap condition for germanium. We will discuss the possibility to achieve lasing with n-doped layers and the application of an external mechanical stress.

WN x thin films (0.5⩽ x ⩽1) were deposited at room temperature on clean silicon substrates by reactive ion-beam sputter deposition in an UHV set-up. Properties such as morphology, microstructure, density, composition, mechanical stress and resistivity have been investigated as functions of ion-beam energy. Thermal stability of very thin films during sequential annealings and Schottky diodes were respectively characterized by in situ Auger electron spectrometry and C(V) measurements. It is demonstrated that a subnitridation of the silicon substrate occurs during the initial growth of the WN x layers. This may explain the absence of silicon out-diffusion up to more than 700°C and some anomalies observed during the electrical measurements of the Schottky diodes.