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EP1901317B1 - Integrated magnetic device with piezoelectric control - Google Patents

Integrated magnetic device with piezoelectric control Download PDF

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Publication number
EP1901317B1
EP1901317B1 EP07354048A EP07354048A EP1901317B1 EP 1901317 B1 EP1901317 B1 EP 1901317B1 EP 07354048 A EP07354048 A EP 07354048A EP 07354048 A EP07354048 A EP 07354048A EP 1901317 B1 EP1901317 B1 EP 1901317B1
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EP
European Patent Office
Prior art keywords
magnetic
magnetic element
piezoelectric material
electrically conducting
central branch
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German (de)
French (fr)
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EP1901317A1 (en
Inventor
Bastien Orlando
Bernard Viala
Sebastien Hentz
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F21/00—Variable inductances or transformers of the signal type
    • H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
    • H01F21/08—Variable inductances or transformers of the signal type continuously variable, e.g. variometers by varying the permeability of the core, e.g. by varying magnetic bias
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F17/00—Fixed inductances of the signal type
    • H01F17/0006—Printed inductances
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/02—Casings
    • H01F27/022—Encapsulation

Definitions

  • the invention relates to a variable-response magnetic device integrated on a substrate and comprising at least one element made of piezoelectric material, associated with actuating electrodes, and at least one magnetic element, able to deform under the stress of the element. made of piezoelectric material.
  • variable inductances transmission line elements, such as resonators, phase shifters or couplers, or spin oscillators.
  • variable inductances realized wholly or in part by integrated manufacturing techniques, derived from microelectronics and enabling continuous and reversible variations in inductance.
  • the various types of components made up to now have many disadvantages, including too little inductance variation, instability as a function of frequency, a mode of operation expensive energy terms, etc.
  • a conventional integrated passive component, with variation of inductance is generally composed of a winding in one or more parts, having in most cases a very high conductivity, and possibly one or more magnetic pieces, called “magnetic cores", having in most cases a high relative permeability (typically ⁇ R > 100).
  • magnetic cores having in most cases a high relative permeability (typically ⁇ R > 100).
  • the first principle consists in playing on the mutual inductances inside the winding by modifying its geometry, as described in particular in the patent US 6,184,755 and in the article "Self-Assembling MEMS Variable and Fixed RF Inductors” by Lubecke et al. (IEEE Trans., Mic Th and Tech 49, 11, 2001). ). It is also possible to play on the coupling with a secondary winding or with any other conductive part. This principle is the simplest to implement in integrated devices, but it allows only small variations in inductance.
  • the second principle consists in playing on the coupling between the winding and the magnetic element by modifying their relative distance, as described in particular in the article "Microassembled Tunable MEMS Inductor” by Sarkar et al. (IEEE MEMS 2005 ).
  • This principle allows large inductance variations, but raises the problem of actuation because it requires large amplitude movements in the plane of the substrate on which the component is made (typically of the order of 10 ⁇ m).
  • the third principle is to play on the permeability of the magnetic material itself.
  • Several known devices (essentially discrete components) use the application of a magnetic field, in order to vary the permeability, as described in particular in the article "Integrated Tunable Magnetic RF Inductor" by Vroubel et al. (IEEE Elect Dev Letter, 25 No. 12, 2004) ).
  • the application of a magnetic field requires the continuous use of currents, which induces a high energy consumption.
  • Piezoelectric materials are generally used, thanks to their integration capability and their low energy consumption.
  • Devices combining piezoelectric layers and magnetoelastic layers, in the form of stacks or heterostructures, have already been studied and considered for producing resonators or sensors or variable inductances, as described for example in the article «A New Hybrid Device using Magnetostrictive Amorphous Films and Piezoelectric Substrates “from Arai et al. (IEEE Trans., Volume 30, No. 2, 1994) ).
  • the article above describes a device 1 comprising a substrate 2 made of piezoelectric material, partially covered on the top and on the bottom by two electrodes 3, 4, respectively upper and lower, the upper electrode 3 being made of a material magnetic.
  • a voltage applied between the electrodes 3, 4 then causes the application of piezoelectric stresses ⁇ in the substrate 2, which are then transmitted to the magnetic material, thus causing a variation in its magnetic properties.
  • the device 1 may be composed of a heterostructure comprising a magnetostrictive material portion 5, with a parallel magnetic field M, and a portion 6 of piezoelectric material, with an electric field E perpendicular to the magnetic field M.
  • the devices described above are not integrated, but are made in solid piezoelectric substrates. Moreover, the mechanical stresses are not controlled because the piezoelectric material applies stresses in all directions of the plane. Therefore, the inductance variation is difficult to control and the electromagnetic properties at high frequencies are poor.
  • WO 2005/064590 discloses a magnetic device comprising on a substrate a stack of a piezoelectric layer entirely integral with the substrate and means for generating a surface acoustic wave, located on the piezoelectric layer on either side of a ferromagnetic element.
  • the piezoelectric layer is intended to participate in the generation of the surface wave and ensure its propagation to the ferromagnetic element.
  • the document WO 2005/064783 describes different possible structures for a spin oscillator.
  • the first structure comprises on a substrate a piezoelectric layer integral with said substrate and in contact with the free ferromagnetic layer of the oscillator.
  • the above structure comprises actuating means located on either side of the ferromagnetic layer.
  • the application of an electric field causes a deformation at the level of the piezoelectric layer, transmitted in the ferromagnetic layer. This results in a variation of the magnetoelastic properties of the ferromagnetic layer and thus a change in the frequency of the oscillator and its quality factor.
  • a second structure comprises a piezoelectric layer locally suspended relative to the substrate and in contact with the free layer of the oscillator. Unlike the first structure, the piezoelectric effect is not used, namely the deformation of the suspended membrane is provided by electrostatic (or capacitive) effect, through the dielectric character of the piezoelectric layer.
  • a third structure comprises a piezoelectric layer also suspended, but at a distance from the free layer of the oscillator.
  • the suspended structure comprises another magnetic element and serves only to modify the magnetostatic coupling between the two magnetic elements.
  • JP 2000 296 612 and JP 11,040,427 describe variable response magnetic devices according to the preamble of claim 1.
  • the object of the invention is to remedy all of the aforementioned drawbacks and is intended to provide an integrated magnetic device with a variable response, allowing large variations of response, and which allows a good control of these variations, even for high frequencies, by controlling the mechanical stresses imposed on the magnetic material, in particular to apply in the uniaxial magnetic material uniaxial stress, homogeneous and large amplitude.
  • the integrated variable response magnetic device according to the invention will be described in a nonlimiting manner as a variable inductance.
  • the device according to the invention also relates to other types of magnetic devices, namely elements of antennas, filters or phase shifters, spin oscillators, etc.
  • the integrated variable response magnetic device is a variable inductance 1 integrated on a substrate that can be applied to all areas requiring a continuous (or discrete) and reversible variation of inductance or impedance with low power. actuating.
  • variable inductance 1 has the form of a beam 7 of piezoelectric material, intended to generate mechanical stresses in a magnetic element 8, made of magnetic material, having a permeability varying according to the stresses applied thereto.
  • the beam 7 has substantially the shape of a tensile test piece and comprises, along a longitudinal axis of reference A1 ( figure 3 ), two transverse portions 9, of predetermined width W1, and a central branch 10, of predetermined width W2, advantageously smaller than the width W1 of the transverse portions 9, on which the magnetic element 8 is arranged.
  • the beam 7 is anchored in a substrate (not shown on the Figures 1 to 14 and 21 to 23 for the sake of clarity), on which the inductance is formed variable 1, preferably at the level of mechanical anchoring zones 16 ( figure 7 ), advantageously located at the ends of the transverse portions 9.
  • the beam 7 is thus free of movement vis-à-vis the substrate, out of its anchoring zones 16, to allow a maximum amplitude of deformation.
  • the profile of the beam 7 in piezoelectric material has been chosen and optimized to generate uniaxial and homogeneous stresses in the associated magnetic element 8.
  • variable inductor 1 comprises actuating electrodes 11a, 11b, placed on either side of the beam 7, cooperating with the beam 7 of piezoelectric material and generating the actuation voltage necessary for the application mechanical stresses in the magnetic element 8.
  • the voltage applied between the electrodes 11a and 11b namely positive or negative, compressive or tensile stresses are generated in the magnetic element 8.
  • the magnetic element 8 is preferably a uniaxial magnetic material composed of an alloy based on iron and / or cobalt and / or nickel, for example deposited in a magnetic field to promote the anisotropy of the material.
  • the direction of anisotropy is substantially parallel or perpendicular to the longitudinal reference axis A1 of the beam 7.
  • the inductor 1 comprises lower electrodes 11a and upper electrodes 11b extending preferably over most of the surface of the transverse portions 9, respectively below and above.
  • only one transverse portion 9 may comprise actuating electrodes, the transverse portion 9 having none thereof then serves essentially for anchoring the beam 7 in the substrate ( figure 21 ).
  • variable inductor 1 preferably comprises a winding 12 of the solenoid type, surrounding the central branch 10 and the associated magnetic element 8.
  • the coil 12 acts as an electrically conductive element, intended to create a magnetic field around the magnetic element 8, with a value of inductance varying as a function of the voltage applied by the electrodes 11 on the beam 7.
  • the coil 12 may be replaced by other electrically conductive elements.
  • the electrically conductive element is a meander-shaped wire 13, having a plurality of successive parallel branches disposed near the magnetic element 8.
  • the meanders 13 are preferably arranged under the central branch 10 of the beam 7.
  • the electrically conductive element is a line-shaped wire 14 disposed near the magnetic element 8, preferably under the central branch 10 of the beam 7 supporting the magnetic element 8.
  • the line-shaped wire 14 comprises, for example, two first parallel lines, perpendicular to the central branch 10 of the beam 7 and connected by a third line extending along the magnetic element 8, under the central branch 10.
  • the electrically conductive element is a spiral-shaped wire 15 extending in proximity to the magnetic element 8, preferably under the central branch 10 of the beam 7 supporting the magnetic element 8.
  • the transverse portions 9 of the beam 7 each comprise an anchoring zone 16, of length L1 and width W1, defining the end of the transverse zones 9 opposite to the central branch 10, providing an anchoring and a strong mechanical connection with the substrate (not shown in FIG. figure 7 for the sake of clarity), on which the variable inductance 1 is made.
  • the remaining area 17 of the transverse portions 9, of length L2 and of width W1, then provides the bulk of the generation of the stresses of the beam 7.
  • Each transverse portion 9 of the beam 7 is extended by an optional transition zone 18, of length L3 and of variable section, extending from the zones 17 of the transverse portions 9 to the central branch 10 of the beam 7 and having, preferably, an elliptical profile advantageously tangential to the zone 17 of the transverse portions 9 and to the central leg 10 of the beam 7.
  • the central branch 10, of length L4 and of width W2 defines a useful zone 19 of the beam 7, corresponding to the zone of the beam 7 in contact with the magnetic element 8.
  • the upper electrodes 11b and lower 11a do not extend, preferably, at the level of the transition zones 18 ( figure 7 ).
  • Each transition zone 18, with an elliptical profile makes it possible in particular to distribute the stresses in a homogeneous manner, while ensuring maximum compactness of the variable inductance 1. Moreover, such a beam 7 embedded only at its ends (zones of anchoring 16) also makes it possible to apply higher stresses, to better control these constraints and also to reduce stray capacitances.
  • the transition zones 18 of the beam 7 may have a simpler profile, for example rectangular ( figure 8 ) or trapezoidal ( figure 9 ).
  • the profile of the transition zones 18 may be elliptical and non-tangent to the central branch 10 and to the transverse portions 9.
  • the beam 7 of the variable inductor 1 comprises a plurality of orifices 20, preferably circular or elliptical, made in the zone 17 of stress generation, adjacent to the anchoring zone 16, transverse portions 9 of the beam 7.
  • Such openings 20 allow in particular to facilitate the release process of the beam 7, during the manufacture of the variable inductor 1, as described below.
  • orifices may also be made in the transition zones 18 of the beam 7, in addition to the orifices 20 made in the stress generation zones 17 or in replacement thereof.
  • the transverse portions 9 may be in the form of strips of parallel material and spaced regularly, connected to the central branch 10 and the anchoring zones 16.
  • the central branch 10 may also be formed of parallel strips of material, connected to the transverse portions 9.
  • the magnetic element 8 has a section of rectangular or square shape.
  • the magnetic element 8 has a section of ellipsoidal shape.
  • the magnetic element 8 consists of a plurality of disjoint elementary elements, preferably of rectangular or ellipsoidal shape, preferably arranged side by side on the central branch 10 of the beam 7 and, preferably, regularly.
  • the axis of anisotropy of the material must be parallel or perpendicular to the longitudinal reference axis A1 of the beam 7 in piezoelectric material ( figure 11 ).
  • a magnetic element 8 of parallelepipedal shape and a solenoid type winding 12 the number of turns is, for example, between 3 and 20.
  • the width of the magnetic element 8 is of the order of 50 to 300 ⁇ m
  • the thickness of the magnetic element 8 is of the order of 100 nm to 2 ⁇ m
  • the length of the magnetic element 8 is of the order of 50 to 300 ⁇ m.
  • the electromagnetic properties of the coil 12 can be finely calculated via, for example, finite element simulation, such as Ansoft's "HFSS" software.
  • the lower electrodes 11a and 11b must be as fine as the production method used, for example of the order of 50 nm to 1 ⁇ m, allows.
  • the thickness of the beam 7 is, for example, of the order of 100 nm to 2 ⁇ m.
  • the thickness of the beam 7 made of piezoelectric material is a compromise between the operating voltage, which decreases with the thickness, and the transmission of the stress to the magnetic element 8, which degrades if the beam 7 is too thin.
  • the central branch 10 of the beam 7, constituting the useful zone 19 of the beam 7, is preferably slightly larger than the magnetic element 8, with a margin of embodiment of the order of 10 ⁇ m, to obtain a maximum deformation amplitude.
  • the dimensions of the magnetic element 8 thus fix the corresponding dimensions W2 and L4 of the central branch 10.
  • the length L1 of the anchoring zone 16 can then be as small as the mechanical strength of the anchorage (depending in particular on the manufacturing process used).
  • a finite element simulation software can be used, such as the software "ANSYS".
  • ANSYS the software "ANSYS"
  • an increase in the length L2 and the width W1 tends to increase the intensity of the stresses applied to the useful area 19 to the detriment of the bulk, while an increase in the length L3, which is typically the order of 50 .mu.m to 300 .mu.m, improves the uniaxial and homogeneous nature of the constraints.
  • the maximum applied voltage must generate stresses lower than the plasticity threshold of the materials used for the beam 7 made of piezoelectric material, the magnetic element 8 or the actuating electrodes 11. Similarly, in the case of the application of a stress in compression, the applied voltage must not cause the buckling of the beam 7 of piezoelectric material.
  • variable inductor 1 is distinguished from the previous embodiments by the number of central branches 10 of the beam 7 of piezoelectric material.
  • the inductor 1 always comprises two transverse portions 9, connected by two central branches 10, each cooperating with a magnetic element 8 and, for example, with a solenoid-type winding 12.
  • the lower electrodes 11a and 11b preferably cover the entire surface of the transverse portions 9 and the central branches 10 are connected to the transverse portions 9 by transition zones 18, preferably with elliptical profiles.
  • the coils 12 may be connected in series or in parallel.
  • inductor 1 including several coils 12 and several magnetic elements 8, governed by the same actuating device, namely the same beam 7 of piezoelectric material, allows in particular to reduce the overall size of the inductor variable 1 and increase the total inductance density.
  • the two central branches 10 of the beam 7 can be associated with other types of electrically conductive elements, as shown in FIGS. Figures 4 to 6 , and / or other forms of magnetic elements 8, as shown in the Figures 11 to 13 , and / or other transition zone profiles 18, as shown in the Figures 7 to 10 .
  • a method of manufacturing an integrated variable inductance 1 will be described in more detail with regard to Figures 15 to 20 .
  • the manufacturing method is intended for producing an inductance 1 with a profiled beam, as described above, comprising a solenoid-type winding 12 ( figure 3 ).
  • the beam 7 of piezoelectric material is then integral with the substrate on which the inductance is formed, by means of lateral ends 23 advantageously made with the same layers of material as the winding 12, as described below. and illustrated on the Figures 15 to 20 .
  • the manufacturing method first comprises the formation on a substrate 21, for example by electrolysis or physical deposition, of a lower part of the winding 12, made of a material of high conductivity, for example copper, aluminum or in gold, then the encapsulation of said lower part by a first sacrificial layer 22, leaving flush with the lateral ends 23.
  • the sacrificial layer 22 is, for example, made of silicon oxide deposited by chemical deposition (PECVD) or polymer resin.
  • PECVD chemical deposition
  • a mechanical or mechano-chemical planarization step of the sacrificial layer 22 can also be performed.
  • the lateral ends 23 may be deposited, for example, by electrolysis and may consist of a material different from that of the lower part of the coil 12.
  • the part of the sacrificial layer 22 surrounding the lateral ends 23 may be of different nature of the part surrounding the coil 12 adjacent the substrate 21.
  • the method comprises the deposition of a stack of a first metal and conducting layer 24 intended to form the lower electrodes 11a of the inductor 1, of a layer 25 of piezoelectric material, intended to form the beam 7 of inductance 1, and a second metallic and conductive layer 26 intended to form the upper electrodes 11b of inductor 1 ( figure 15 ).
  • the layer 25 of piezoelectric material is deposited by a physical vapor deposition process (PVD) and the lower electrodes can be platinum, for a piezoelectric lead titano-zirconate (PZT) beam, or in molybdenum, for a piezoelectric aluminum nitride (AIN) beam.
  • the upper electrodes may be different in nature from the lower electrodes, for example gold, copper or tungsten, etc. Additional protective layers (not shown), for example gold or tungsten, may be provided, in particular to facilitate the subsequent release of the inductor.
  • a step of etching the stack of the layers 24, 25, 26 is then realized, to delimit the characteristic shape of the beam 7 of the inductance 1.
  • the structuring of the layers 24, 25, 26 can be carried out by a chemical method, of wet etching type, or physicochemical type, dry etching type (RIE ), or by ion milling.
  • RIE dry etching type
  • a layer 27 of uniaxial magnetic material ( figure 16 ) is then deposited and etched in order to form the magnetic element 8 placed on the central branch 10 of the beam 7 previously formed ( figure 17 ).
  • the magnetic element 8 can be made by physical vapor deposition (PVD) of an alloy material based on iron and / or nickel and / or cobalt.
  • the layer 27 may also be formed by a stack of different dielectric and conductive layers.
  • the structuring of the layers 24, 25, 26 by etching thus makes it possible to obtain the characteristic shape of the beam 7 with two transverse portions 9, perpendicular to the reference axis A1 of the beam 7, and a central branch 10 on which the magnetic element 8 is formed. It then remains only to close the winding 12, to obtain the inductance 1 as shown in FIG. figure 20 .
  • the inductor 1 is then suspended and anchored on the substrate 21, via the lateral ends 23, as shown in FIG. figure 19 .
  • the formation of the upper part of the winding 12 can be achieved by etching and resuming contact through the sacrificial layer 28, by a chemical or physicochemical method or by ion milling.
  • the deposition of the upper part of the winding 12 can be achieved by electrolysis and can be made from a material different from that of the lower part of the coil 12.
  • the release of the structure can be achieved by chemical selective etching, of the type wet or physico-chemical attack (of the RIE type) of the sacrificial layers 22 and 28.
  • the method according to the invention makes it possible to obtain an inductance 1 embedded at its two ends, with a characteristic profile making it possible to place the magnetic element and the winding substantially in its central part. , in order to concentrate the constraints and make them as uniaxial and homogeneous as possible.
  • Such a manufacturing method thus uses manufacturing techniques derived from microelectronics and adapted for microsystems.
  • Such integrated inductance 1 integrated therefore allows to apply a homogeneous and uniaxial stress - in tension or compression - on the magnetic element and to maximize the value of these constraints, for a given actuation voltage, thanks in particular to the characteristic shape and profile of its beam.
  • variable inductor the use of a beam of piezoelectric material released and embedded at its two ends makes it possible to improve the mechanical and electromagnetic properties of the variable inductor according to the invention, so as to obtain large reversible variations in inductance. , continuous or discontinuous, with low operating voltages, while preserving good frequency properties, especially at high frequencies.
  • the invention is not limited to the various embodiments described above.
  • the values of widths and lengths of the different zones of the beam 7 are nonlimiting and depend in particular on the desired size of the variable inductance 1 and the desired inductance value.
  • the electrodes 11 can extend above the transition zones 18 of the beam 7 ( figure 7 ).
  • the inductor 1 may comprise more than two central branches 10, all associated with a corresponding magnetic element 8 and a corresponding electrically conductive element, preferably of the solenoid winding type.
  • the beam 7 of piezoelectric material comprises a first transverse portion 9 of piezoelectric material, as shown in FIG. figure 7 , cooperating with the lower electrodes 11a and 11b, and a second transverse portion 9, of much smaller length, comprising only the anchoring zone 16 of the beam 7 to the substrate.
  • the operating principle of the inductor 1 is the same, with a solenoid-type winding 12 and a magnetic element 8, placed on the central branch 10 of the beam 7.
  • the width W1 of the transverse portions 9 may be smaller than the width W3 of the corresponding anchoring zones 16. Furthermore, the width W2 of the central branch 10, on which the magnetic element 8 is placed, may be greater than the width W1 of the transverse portions 9. In general, the widths W1, W2 and W3 of the different zones of the beam 7 are not interconnected and the beam 7 can take a quite other complex shape.
  • the beam 7 made of piezoelectric material and the associated magnetic element 8 can be encapsulated in layers 22 and 28 of insulating material and sufficiently soft, for example a low dielectric constant polymer resin, to enable a sufficient deformation of the beam 7 relative to the substrate, without the need to remove the layers 22 and 28. The release of the beam 7 is then no longer necessary.
  • the invention applies to any magnetic device with a variable response in the form of a beam 7 comprising an element made of piezoelectric material.
  • the element made of piezoelectric material may consist of the complete beam 7 or only of parts of the beam, namely a part of a transverse part 9, a complete transverse part 9 or the two transverse parts 9, the central branch 10 and the transition zones 18 can then be made of another material.
  • the invention applies in particular to any type of reconfigurable electronic circuit, for which a limitation of the number of components is sought by using adjustable components.
  • the principle used to vary the dynamic permeability, as well as its practical application, are not limited in terms of inductance values or operating frequency.
  • the invention therefore applies to all areas where a continuous (or discontinuous) and reversible dynamic permeability variation is necessary, with very low power operation, in particular reconfigurable multiband circuits, fine impedance matching and tunable oscillators.
  • the invention is also applicable to other types of magnetic devices with variable response, depending on how the magnetic element 8 is associated with the electrically conductive element (the coil 12 for example).
  • the magnetic element must be mechanically secured to the beam of piezoelectric material, so that the deformations of said beam generate a variation of the magnetic properties of the magnetic element.
  • the electrically conductive element is placed at a distance from the magnetic element, only on one side of the magnetic element, for example in the case of the meandering element 13 ( figure 4 ), in the form of lines 14 ( figure 5 ) or in the form of a spiral 15 ( figure 6 ), or on either side of the magnetic element 8, for example in the case of the solenoid-shaped element 12 ( figure 3 ), the magnetic device is then a variable inductance.
  • the electrically conductive element is placed only on one side of the magnetic element, it is also possible to produce transmission line elements, such as resonators, phase shifters, couplers, antennas , filters, etc.

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Description

Domaine technique de l'inventionTechnical field of the invention

L'invention concerne un dispositif magnétique à réponse variable intégré sur un substrat et comportant au moins un élément en matériau piézoélectrique, associé à des électrodes d'actionnement, et au moins un élément magnétique, apte à se déformer sous la sollicitation de l'élément en matériau piézoélectrique.The invention relates to a variable-response magnetic device integrated on a substrate and comprising at least one element made of piezoelectric material, associated with actuating electrodes, and at least one magnetic element, able to deform under the stress of the element. made of piezoelectric material.

L'invention s'applique notamment à des inductances variables, des éléments de ligne de transmission, tels que des résonateurs, des déphaseurs ou des coupleurs, ou encore des oscillateurs de spin.The invention applies in particular to variable inductances, transmission line elements, such as resonators, phase shifters or couplers, or spin oscillators.

État de la techniqueState of the art

II existe plusieurs types d'inductances variables intégrées, ou semi-intégrées, réalisées intégralement ou en partie par des techniques de fabrication intégrées, issues de la microélectronique et permettant des variations continues et réversibles d'inductance. Cependant, les différents types de composants réalisés jusque-là présentent de nombreux inconvénients, notamment une trop faible variation d'inductance, une instabilité en fonction de la fréquence, un mode d'actionnement onéreux en termes énergétiques, etc.There are several types of integrated, or semi-integrated, variable inductances realized wholly or in part by integrated manufacturing techniques, derived from microelectronics and enabling continuous and reversible variations in inductance. However, the various types of components made up to now have many disadvantages, including too little inductance variation, instability as a function of frequency, a mode of operation expensive energy terms, etc.

Un composant passif intégré classique, avec variation d'inductance, est généralement composé d'un bobinage en une ou plusieurs parties, possédant dans la plupart des cas une très forte conductivité, et éventuellement d'une ou plusieurs pièces magnétiques, appelées « noyaux magnétiques », possédant dans la plupart des cas une forte perméabilité relative (typiquement µR>100). Il existe trois grands principes connus, utilisables pour la variation d'inductance.A conventional integrated passive component, with variation of inductance, is generally composed of a winding in one or more parts, having in most cases a very high conductivity, and possibly one or more magnetic pieces, called "magnetic cores", having in most cases a high relative permeability (typically μ R > 100). There are three known principles that can be used for the variation of inductance.

Le premier principe consiste à jouer sur les inductances mutuelles à l'intérieur du bobinage en modifiant sa géométrie, comme décrit notamment dans le brevet US 6 184 755 et dans l'article « Self-Assembling MEMS Variable and Fixed RF Inductors » de Lubecke et al. (IEEE Trans. Mic. Th. and Tech. vol. 49 n°11, 2001 ). Il est possible également de jouer sur le couplage avec un bobinage secondaire ou avec une tout autre pièce conductrice. Ce principe est le plus simple à mettre en oeuvre dans les dispositifs intégrés, mais il ne permet que de faibles variations d'inductance.The first principle consists in playing on the mutual inductances inside the winding by modifying its geometry, as described in particular in the patent US 6,184,755 and in the article "Self-Assembling MEMS Variable and Fixed RF Inductors" by Lubecke et al. (IEEE Trans., Mic Th and Tech 49, 11, 2001). ). It is also possible to play on the coupling with a secondary winding or with any other conductive part. This principle is the simplest to implement in integrated devices, but it allows only small variations in inductance.

Le deuxième principe consiste à jouer sur le couplage entre le bobinage et l'élément magnétique en modifiant leur distance relative, comme décrit notamment dans l'article « Microassembled Tunable MEMS Inductor » de Sarkar et al. (IEEE MEMS 2005 ). Ce principe permet de fortes variations d'inductance, mais pose le problème de l'actionnement, car il nécessite des mouvements de grande amplitude dans le plan du substrat sur lequel est réalisé le composant (typiquement de l'ordre de 10µm).The second principle consists in playing on the coupling between the winding and the magnetic element by modifying their relative distance, as described in particular in the article "Microassembled Tunable MEMS Inductor" by Sarkar et al. (IEEE MEMS 2005 ). This principle allows large inductance variations, but raises the problem of actuation because it requires large amplitude movements in the plane of the substrate on which the component is made (typically of the order of 10 μm).

Le troisième principe consiste à jouer sur la perméabilité du matériau magnétique lui-même. Plusieurs dispositifs connus (essentiellement des composants discrets) utilisent l'application d'un champ magnétique, afin de faire varier la perméabilité, comme décrit notamment dans l'article « Integrated Tunable Magnetic RF Inductor » de Vroubel et al. (IEEE Elec. Dev. Letter vol. 25 n°12, 2004 ). Cependant, l'application d'un champ magnétique nécessite l'utilisation en continu de courants, ce qui induit une forte consommation énergétique.The third principle is to play on the permeability of the magnetic material itself. Several known devices (essentially discrete components) use the application of a magnetic field, in order to vary the permeability, as described in particular in the article "Integrated Tunable Magnetic RF Inductor" by Vroubel et al. (IEEE Elect Dev Letter, 25 No. 12, 2004) ). However, the application of a magnetic field requires the continuous use of currents, which induces a high energy consumption.

Il existe un autre moyen qui consiste à utiliser la variation de la perméabilité magnétique du matériau en fonction des contraintes mécaniques qui lui sont appliquées, comme décrit notamment dans l'article « Processing and application of magnetoelastic thin films in high-frequency devices » de Frommberger et al. (Microelectronics Engineering 67-68 2003 ) et dans l'article « High-Frequency Magnetoelastic Multilayer Thin Films and Applications » de Ludwig et al. (IEEE Trans. Mag. Vol.. 39 n°5, 2003 ). Cette propriété est due au couplage magnétomécanique présent dans tous les matériaux magnétiques à diverses échelles et connu sous le nom de magnétoélasticité.There is another way which consists in using the variation of the magnetic permeability of the material as a function of the mechanical stresses applied to it, as described in particular in the article "Processing and application of magnetoelastic thin films in high-frequency devices" by Frommberger et al. (Microelectronics Engineering 67-68 2003 ) and in the article "High-Frequency Magnetoelastic Multilayer Thin Films and Applications" by Ludwig et al. (IEEE Trans., Mag., Vol 39 No 5, 2003) ). This property is due to the magnetomechanical coupling present in all magnetic materials at various scales and known as magnetoelasticity.

De manière connue en magnétoélasticité, il est essentiel de maîtriser l'amplitude et la direction des contraintes appliquées dans une couche en matériau magnétique uniaxial. En effet, les contraintes ont une grande influence sur le comportement dynamique du matériau magnétique. Si les contraintes sont trop inhomogènes ou ne sont pas appliquées selon des directions dans le plan du substrat à 0° ou à 90° de l'axe d'anisotropie du matériau magnétique, il devient très difficile de prévoir les propriétés magnétiques en fonction des contraintes appliquées. La variation de perméabilité et le comportement dynamique de la couche magnétique ne sont alors plus maîtrisables.In known manner in magnetoelasticity, it is essential to control the amplitude and the direction of the stresses applied in a layer of uniaxial magnetic material. Indeed, the stresses have a great influence on the dynamic behavior of the magnetic material. If the stresses are too inhomogeneous or are not applied along directions in the plane of the substrate at 0 ° or at 90 ° to the axis of anisotropy of the magnetic material, it becomes very difficult to predict the magnetic properties according to the constraints applied. The variation in permeability and the dynamic behavior of the magnetic layer are then no longer controllable.

Par ailleurs, il est nécessaire de déterminer le mode d'actionnement de l'inductance. Les matériaux piézoélectriques sont généralement utilisés, grâce à leur possibilité d'intégration et leur faible consommation énergétique. Des dispositifs combinant des couches piézoélectriques et des couches magnétoélastiques, sous la forme d'empilements ou d'hétérostructures, ont déjà été étudiés et envisagés pour la réalisation de résonateurs ou de capteurs ou d'inductances variables, comme décrit par exemple dans l'article « A New Hybrid Device using Magnetostrictive Amorphous Films and Piezoelectric Substrates » de Arai et al. (IEEE Trans. Mag. Vol. 30 n°2, 1994 ).Moreover, it is necessary to determine the mode of actuation of the inductor. Piezoelectric materials are generally used, thanks to their integration capability and their low energy consumption. Devices combining piezoelectric layers and magnetoelastic layers, in the form of stacks or heterostructures, have already been studied and considered for producing resonators or sensors or variable inductances, as described for example in the article «A New Hybrid Device using Magnetostrictive Amorphous Films and Piezoelectric Substrates "from Arai et al. (IEEE Trans., Volume 30, No. 2, 1994) ).

Comme représenté schématiquement sur la figure 1, l'article ci-dessus décrit un dispositif 1 comportant un substrat 2 en matériau piézoélectrique, recouvert partiellement sur le dessus et sur le dessous par deux électrodes 3, 4, respectivement supérieure et inférieure, l'électrode supérieure 3 étant réalisée en un matériau magnétique. Une tension appliquée entre les électrodes 3, 4 entraîne alors l'application de contraintes piézoélectriques σ dans le substrat 2, qui sont alors transmises au matériau magnétique, entraînant ainsi une variation de ses propriétés magnétiques.As shown schematically on the figure 1 , the article above describes a device 1 comprising a substrate 2 made of piezoelectric material, partially covered on the top and on the bottom by two electrodes 3, 4, respectively upper and lower, the upper electrode 3 being made of a material magnetic. A voltage applied between the electrodes 3, 4 then causes the application of piezoelectric stresses σ in the substrate 2, which are then transmitted to the magnetic material, thus causing a variation in its magnetic properties.

L'article « Magnetoelectric Properties of a Heterostructure of Magnetostrictive and Piezoelectric Composites » de Wan et al. (IEEE Trans. Mag. Vol. 40 n°4, 2004 ) décrit également un autre exemple de dispositif combinant l'utilisation de matériaux piézoélectriques et de matériaux magnétoélastiques. Comme représenté schématiquement sur la figure 2, le dispositif 1 peut être composé par une hétérostructure comportant une portion 5 en matériau magnétostrictif, avec un champ magnétique M parallèle, et une portion 6 en matériau piézoélectrique, avec un champ électrique E, perpendiculaire au champ magnétique M.Article "Magnetoelectric Properties of a Heterostructure of Magnetostrictive and Piezoelectric Composites" by Wan et al. (IEEE Trans., Mag, Vol 40 No.4, 2004) ) also discloses another example of a device combining the use of piezoelectric materials and magnetoelastic materials. As shown schematically on the figure 2 , the device 1 may be composed of a heterostructure comprising a magnetostrictive material portion 5, with a parallel magnetic field M, and a portion 6 of piezoelectric material, with an electric field E perpendicular to the magnetic field M.

Les dispositifs décrits ci-dessus ne sont pas intégrés, mais sont réalisés dans des substrats piézoélectriques massifs. Par ailleurs, les contraintes mécaniques ne sont pas maîtrisées, car le matériau piézoélectrique applique des contraintes dans toutes les directions du plan. Par conséquent, la variation d'inductance est difficilement maîtrisable et les propriétés électromagnétiques aux hautes fréquences sont médiocres.The devices described above are not integrated, but are made in solid piezoelectric substrates. Moreover, the mechanical stresses are not controlled because the piezoelectric material applies stresses in all directions of the plane. Therefore, the inductance variation is difficult to control and the electromagnetic properties at high frequencies are poor.

Par ailleurs, le document WO 2005/064590 décrit un dispositif magnétique comportant sur un substrat un empilement d'une couche piézoélectrique entièrement solidaire du substrat et de moyens de génération d'une onde acoustique de surface, situés sur la couche piézoélectrique de part et d'autre d'un élément ferromagnétique. La couche piézoélectrique est destinée à participer à la génération de l'onde de surface et assurer sa propagation jusqu'à l'élément ferromagnétique.In addition, the document WO 2005/064590 discloses a magnetic device comprising on a substrate a stack of a piezoelectric layer entirely integral with the substrate and means for generating a surface acoustic wave, located on the piezoelectric layer on either side of a ferromagnetic element. The piezoelectric layer is intended to participate in the generation of the surface wave and ensure its propagation to the ferromagnetic element.

Le document WO 2005/064783 décrit différentes structures possibles pour un oscillateur de spin. La première structure comporte sur un substrat une couche piézoélectrique solidaire dudit substrat et en contact avec la couche ferromagnétique libre de l'oscillateur. La structure ci-dessus comporte des moyens d'actionnement situés de part et d'autre de la couche ferromagnétique. L'application d'un champ électrique provoque une déformation au niveau de la couche piézoélectrique, transmis dans la couche ferromagnétique. Il en résulte une variation des propriétés magnétoélastiques de la couche ferromagnétique et donc une modification de la fréquence de l'oscillateur et de son facteur de qualité.The document WO 2005/064783 describes different possible structures for a spin oscillator. The first structure comprises on a substrate a piezoelectric layer integral with said substrate and in contact with the free ferromagnetic layer of the oscillator. The above structure comprises actuating means located on either side of the ferromagnetic layer. The application of an electric field causes a deformation at the level of the piezoelectric layer, transmitted in the ferromagnetic layer. This results in a variation of the magnetoelastic properties of the ferromagnetic layer and thus a change in the frequency of the oscillator and its quality factor.

Une deuxième structure comporte une couche piézoélectrique localement suspendue par rapport au substrat et en contact avec la couche libre de l'oscillateur. À la différence de la première structure, l'effet piézoélectrique n'est pas utilisé, à savoir la déformation de la membrane suspendue est assurée par effet électrostatique (ou capacitif), par l'intermédiaire du caractère diélectrique de la couche piézoélectrique.A second structure comprises a piezoelectric layer locally suspended relative to the substrate and in contact with the free layer of the oscillator. Unlike the first structure, the piezoelectric effect is not used, namely the deformation of the suspended membrane is provided by electrostatic (or capacitive) effect, through the dielectric character of the piezoelectric layer.

Une troisième structure comporte une couche piézoélectrique également suspendue, mais à distance de la couche libre de l'oscillateur. La structure suspendue comporte un autre élément magnétique et sert uniquement à modifier le couplage magnétostatique entre les deux éléments magnétiques.A third structure comprises a piezoelectric layer also suspended, but at a distance from the free layer of the oscillator. The suspended structure comprises another magnetic element and serves only to modify the magnetostatic coupling between the two magnetic elements.

Pour toutes les structures décrites ci-dessus, aucun contrôle de la direction des contraintes induites au niveau du matériau ferromagnétique n'est réalisé et les structures suspendues décrites ne servent pas du tout à contrôler ces contraintes.For all the structures described above, no control of the direction of the stresses induced at the level of the ferromagnetic material is realized and the suspended structures described do not serve at all to control these constraints.

JP 2000 296 612 et JP 11 040 427 décrivent des dispositifs magnétiques à réponse variable selon la préambule de la revendication 1. JP 2000 296 612 and JP 11,040,427 describe variable response magnetic devices according to the preamble of claim 1.

Objet de l'inventionObject of the invention

L'invention a pour but de remédier à l'ensemble des inconvénients précités et a pour objet la réalisation d'un dispositif magnétique intégré à réponse variable, autorisant de fortes variations de réponse, et qui permette un bon contrôle de ces variations, même pour des hautes fréquences, en maîtrisant les contraintes mécaniques imposées sur le matériau magnétique, afin notamment d'appliquer dans le matériau magnétique uniaxial une contrainte uniaxiale, homogène et de grande amplitude.The object of the invention is to remedy all of the aforementioned drawbacks and is intended to provide an integrated magnetic device with a variable response, allowing large variations of response, and which allows a good control of these variations, even for high frequencies, by controlling the mechanical stresses imposed on the magnetic material, in particular to apply in the uniaxial magnetic material uniaxial stress, homogeneous and large amplitude.

L'objet de l'invention est caractérisé en ce que le dispositif a la forme d'une poutre, mobile par rapport au substrat et comportant, selon un axe longitudinal de référence, deux parties transversales, de largeur prédéterminée, et en ce que :

  • l'élément en matériau piézoélectrique est constitué par au moins une partie d'une partie transversale,
  • chaque partie transversale comporte une zone d'ancrage mécanique sur le substrat,
  • et les parties transversales sont reliées par au moins une branche centrale, de largeur prédéterminée, sur laquelle est disposé l'élément magnétique.
The object of the invention is characterized in that the device has the shape of a beam, movable with respect to the substrate and comprising, along a longitudinal reference axis, two transverse portions, of predetermined width, and in that:
  • the element made of piezoelectric material is constituted by at least a part of a transverse part,
  • each transverse portion has a mechanical anchoring zone on the substrate,
  • and the transverse portions are connected by at least one central branch, of predetermined width, on which the magnetic element is arranged.

Description sommaire des dessinsBrief description of the drawings

D'autres avantages et caractéristiques ressortiront plus clairement de la description qui va suivre de modes particuliers de réalisation de l'invention donnés à titre d'exemples non limitatifs et représentés aux dessins annexés, dans lesquels :

  • La figure 1 représente schématiquement un mode particulier de réalisation d'un dispositif magnétique selon l'art antérieur, avec une structure multicouches.
  • La figure 2 représente schématiquement un autre mode particulier de réalisation d'un dispositif magnétique selon l'art antérieur, composé par une hétérostructure.
  • La figure 3 représente un mode particulier de réalisation d'un dispositif magnétique intégré à réponse variable selon l'invention.
  • Les figures 4 à 6 représentent schématiquement des variantes de réalisation d'un dispositif magnétique selon la figure 3.
  • La figure 7 est une vue de dessus de la poutre du dispositif magnétique selon la figure 3.
  • Les figures 8 à 10 sont des vues de dessus de la poutre de variantes de réalisation du dispositif magnétique selon la figure 7.
  • Les figures 11 à 13 sont des vues de dessus de variantes de réalisation d'un dispositif magnétique selon la figure 3, représentant uniquement la poutre et l'élément magnétique.
  • La figure 14 représente schématiquement une vue en perspective d'une autre variante de réalisation d'un dispositif magnétique selon l'invention.
  • Les figures 15 à 20 représentent des vues de face en coupe (figures 15, 16, 18, 19) et des vues de dessus (figures 17, 20) de différentes étapes d'un mode particulier de réalisation d'un procédé de fabrication d'un dispositif magnétique selon l'invention.
  • La figure 21 représente schématiquement une vue en perspective d'une autre variante de réalisation d'un dispositif magnétique selon l'invention.
  • La figure 22 représente très schématiquement une vue de dessus d'une poutre d'une autre variante de réalisation d'un dispositif magnétique selon l'invention.
  • La figure 23 représente très schématiquement une vue de face d'une poutre d'une autre variante de réalisation d'un dispositif magnétique selon l'invention.
Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention. given as non-limiting examples and shown in the accompanying drawings, in which:
  • The figure 1 schematically represents a particular embodiment of a magnetic device according to the prior art, with a multilayer structure.
  • The figure 2 schematically represents another particular embodiment of a magnetic device according to the prior art, composed by a heterostructure.
  • The figure 3 represents a particular embodiment of an integrated variable response magnetic device according to the invention.
  • The Figures 4 to 6 schematically represent variant embodiments of a magnetic device according to the figure 3 .
  • The figure 7 is a top view of the beam of the magnetic device according to the figure 3 .
  • The Figures 8 to 10 are top views of the beam of embodiments of the magnetic device according to the figure 7 .
  • The Figures 11 to 13 are top views of alternative embodiments of a magnetic device according to the figure 3 , representing only the beam and the magnetic element.
  • The figure 14 schematically represents a perspective view of another variant embodiment of a magnetic device according to the invention.
  • The Figures 15 to 20 represent front views in section ( Figures 15, 16 , 18, 19 ) and top views ( figures 17 , 20 ) of different steps of a particular embodiment of a method of manufacturing a magnetic device according to the invention.
  • The figure 21 schematically represents a perspective view of another variant embodiment of a magnetic device according to the invention.
  • The figure 22 schematically represents a view from above of a beam of another variant embodiment of a magnetic device according to the invention.
  • The figure 23 schematically represents a front view of a beam of another variant embodiment of a magnetic device according to the invention.

Description de modes particuliers de réalisationDescription of particular embodiments

En référence aux figures, le dispositif magnétique intégré à réponse variable selon l'invention va être décrit à titre non limitatif comme une inductance variable. Toutefois, le dispositif selon l'invention concerne également d'autres types de dispositifs magnétiques, à savoir des éléments d'antennes, de filtres ou de déphaseurs, des oscillateurs de spin, etc.With reference to the figures, the integrated variable response magnetic device according to the invention will be described in a nonlimiting manner as a variable inductance. However, the device according to the invention also relates to other types of magnetic devices, namely elements of antennas, filters or phase shifters, spin oscillators, etc.

En référence aux figures, le dispositif magnétique intégré à réponse variable est une inductance variable 1 intégrée sur un substrat pouvant s'appliquer à tous les domaines requérant une variation continue (ou discrète) et réversible d'inductance ou d'impédance avec une faible puissance d'actionnement.With reference to the figures, the integrated variable response magnetic device is a variable inductance 1 integrated on a substrate that can be applied to all areas requiring a continuous (or discrete) and reversible variation of inductance or impedance with low power. actuating.

Dans le mode particulier de réalisation représenté sur la figure 3, l'inductance variable 1 a la forme d'une poutre 7 en matériau piézoélectrique, destinée à générer des contraintes mécaniques dans un élément magnétique 8, en matériau magnétique, ayant une perméabilité variant en fonction des contraintes qui lui sont appliquées. La poutre 7 a sensiblement la forme d'une éprouvette de traction et comporte, selon un axe longitudinal de référence A1 (figure 3), deux parties transversales 9, de largeur W1 prédéterminée, et une branche centrale 10, de largeur W2 prédéterminée, avantageusement inférieure à la largeur W1 des parties transversales 9, sur laquelle est disposé l'élément magnétique 8.In the particular embodiment shown on the figure 3 variable inductance 1 has the form of a beam 7 of piezoelectric material, intended to generate mechanical stresses in a magnetic element 8, made of magnetic material, having a permeability varying according to the stresses applied thereto. The beam 7 has substantially the shape of a tensile test piece and comprises, along a longitudinal axis of reference A1 ( figure 3 ), two transverse portions 9, of predetermined width W1, and a central branch 10, of predetermined width W2, advantageously smaller than the width W1 of the transverse portions 9, on which the magnetic element 8 is arranged.

La poutre 7 est ancrée dans un substrat (non représenté sur les figures 1 à 14 et 21 à 23 pour des raisons de clarté), sur lequel est formée l'inductance variable 1, de préférence au niveau de zones d'ancrage mécanique 16 (figure 7), avantageusement situées aux extrémités des parties transversales 9. La poutre 7 est ainsi libre de mouvement vis-à-vis du substrat, hors de ses zones d'ancrage 16, pour permettre une amplitude maximale de déformation.The beam 7 is anchored in a substrate (not shown on the Figures 1 to 14 and 21 to 23 for the sake of clarity), on which the inductance is formed variable 1, preferably at the level of mechanical anchoring zones 16 ( figure 7 ), advantageously located at the ends of the transverse portions 9. The beam 7 is thus free of movement vis-à-vis the substrate, out of its anchoring zones 16, to allow a maximum amplitude of deformation.

Le profil de la poutre 7 en matériau piézoélectrique a été choisi et optimisé pour générer des contraintes uniaxiales et homogènes dans l'élément magnétique 8 associé.The profile of the beam 7 in piezoelectric material has been chosen and optimized to generate uniaxial and homogeneous stresses in the associated magnetic element 8.

Sur la figure 3, l'inductance variable 1 comporte des électrodes d'actionnement 11 a, 11 b, placées de part et d'autre de la poutre 7, coopérant avec la poutre 7 en matériau piézoélectrique et générant la tension d'actionnement nécessaire à l'application des contraintes mécaniques dans l'élément magnétique 8. Suivant la tension appliquée entre les électrodes 11 a et 11 b, à savoir positive ou négative, des contraintes de compression ou de traction sont générées dans l'élément magnétique 8.On the figure 3 , the variable inductor 1 comprises actuating electrodes 11a, 11b, placed on either side of the beam 7, cooperating with the beam 7 of piezoelectric material and generating the actuation voltage necessary for the application mechanical stresses in the magnetic element 8. Depending on the voltage applied between the electrodes 11a and 11b, namely positive or negative, compressive or tensile stresses are generated in the magnetic element 8.

L'élément magnétique 8 est, de préférence, en un matériau magnétique uniaxial composé d'un alliage à base de fer et/ou de cobalt et/ou de nickel, par exemple déposé sous champ magnétique pour favoriser l'anisotropie du matériau. Avantageusement, la direction d'anisotropie est sensiblement parallèle ou perpendiculaire à l'axe longitudinal de référence A1 de la poutre 7.The magnetic element 8 is preferably a uniaxial magnetic material composed of an alloy based on iron and / or cobalt and / or nickel, for example deposited in a magnetic field to promote the anisotropy of the material. Advantageously, the direction of anisotropy is substantially parallel or perpendicular to the longitudinal reference axis A1 of the beam 7.

Sur la figure 3, l'inductance 1 comporte des électrodes inférieures 11a et des électrodes supérieures 11 b s'étendant, de préférence, sur la majeure partie de la surface des parties transversales 9, respectivement au-dessous et au-dessus. Dans une variante de réalisation non représentée, une seule partie transversale 9 peut comporter des électrodes d'actionnement, la partie transversale 9 n'en comportant pas sert alors essentiellement pour l'ancrage de la poutre 7 dans le substrat (figure 21).On the figure 3 the inductor 1 comprises lower electrodes 11a and upper electrodes 11b extending preferably over most of the surface of the transverse portions 9, respectively below and above. In an alternative embodiment not shown, only one transverse portion 9 may comprise actuating electrodes, the transverse portion 9 having none thereof then serves essentially for anchoring the beam 7 in the substrate ( figure 21 ).

L'inductance variable 1 comporte, de préférence, un bobinage 12 de type solénoïde, entourant la branche centrale 10 et l'élément magnétique 8 associé. Le bobinage 12 joue le rôle d'un élément électriquement conducteur, destiné à créer un champ magnétique autour de l'élément magnétique 8, avec une valeur d'inductance variant en fonction de la tension appliquée par les électrodes 11 sur la poutre 7.The variable inductor 1 preferably comprises a winding 12 of the solenoid type, surrounding the central branch 10 and the associated magnetic element 8. The coil 12 acts as an electrically conductive element, intended to create a magnetic field around the magnetic element 8, with a value of inductance varying as a function of the voltage applied by the electrodes 11 on the beam 7.

Dans les variantes de réalisation de l'inductance variable 1, représentées sur les figures 4, 5 et 6, le bobinage 12 peut être remplacé par d'autres éléments électriquement conducteurs. Sur la figure 4, l'élément électriquement conducteur est un fil en forme de méandres 13, comportant une pluralité de branches parallèles successives, disposées à proximité de l'élément magnétique 8. Les méandres 13 sont disposés, de préférence, sous la branche centrale 10 de la poutre 7.In the variant embodiments of the variable inductor 1, represented on the Figures 4, 5 and 6 , the coil 12 may be replaced by other electrically conductive elements. On the figure 4 , the electrically conductive element is a meander-shaped wire 13, having a plurality of successive parallel branches disposed near the magnetic element 8. The meanders 13 are preferably arranged under the central branch 10 of the beam 7.

Sur la figure 5, l'élément électriquement conducteur est un fil en forme de lignes 14, disposé à proximité de l'élément magnétique 8, de préférence sous la branche centrale 10 de la poutre 7 supportant l'élément magnétique 8. Le fil en forme de lignes 14 comporte, par exemple, deux premières lignes parallèles, perpendiculaires à la branche centrale 10 de la poutre 7 et reliées par une troisième ligne s'étendant le long de l'élément magnétique 8, sous la branche centrale 10.On the figure 5 the electrically conductive element is a line-shaped wire 14 disposed near the magnetic element 8, preferably under the central branch 10 of the beam 7 supporting the magnetic element 8. The line-shaped wire 14 comprises, for example, two first parallel lines, perpendicular to the central branch 10 of the beam 7 and connected by a third line extending along the magnetic element 8, under the central branch 10.

Sur la figure 6, l'élément électriquement conducteur est un fil en forme de spirale 15, s'étendant à proximité de l'élément magnétique 8, de préférence sous la branche centrale 10 de la poutre 7 supportant l'élément magnétique 8.On the figure 6 the electrically conductive element is a spiral-shaped wire 15 extending in proximity to the magnetic element 8, preferably under the central branch 10 of the beam 7 supporting the magnetic element 8.

Sur la figure 7, uniquement la poutre 7 en matériau piézoélectrique est représentée. Les parties transversales 9 de la poutre 7 comportent chacune une zone d'ancrage 16, de longueur L1 et de largeur W1, définissant l'extrémité des zones transversales 9 opposée à la branche centrale 10, assurant un ancrage et une liaison mécanique forte avec le substrat (non représenté sur la figure 7 pour des raisons de clarté), sur lequel est réalisée l'inductance variable 1. La zone restante 17 des parties transversales 9, de longueur L2 et de largeur W1, assure alors l'essentiel de la génération des contraintes de la poutre 7.On the figure 7 only the beam 7 of piezoelectric material is shown. The transverse portions 9 of the beam 7 each comprise an anchoring zone 16, of length L1 and width W1, defining the end of the transverse zones 9 opposite to the central branch 10, providing an anchoring and a strong mechanical connection with the substrate (not shown in FIG. figure 7 for the sake of clarity), on which the variable inductance 1 is made. The remaining area 17 of the transverse portions 9, of length L2 and of width W1, then provides the bulk of the generation of the stresses of the beam 7.

Chaque partie transversale 9 de la poutre 7 est prolongée par une zone de transition 18 facultative, de longueur L3 et de section variable, s'étendant des zones 17 des parties transversales 9 jusqu'à la branche centrale 10 de la poutre 7 et présentant, de préférence, un profil elliptique avantageusement tangent à la zone 17 des parties transversales 9 et à la branche centrale 10 de la poutre 7. La branche centrale 10, de longueur L4 et de largeur W2, définit une zone utile 19 de la poutre 7, correspondant à la zone de la poutre 7 en contact avec l'élément magnétique 8. Dans le cas de la présence des zones de transition 18, les électrodes supérieures 11 b et inférieures 11 a ne s'étendent pas, de préférence, au niveau des zones de transition 18 (figure 7).Each transverse portion 9 of the beam 7 is extended by an optional transition zone 18, of length L3 and of variable section, extending from the zones 17 of the transverse portions 9 to the central branch 10 of the beam 7 and having, preferably, an elliptical profile advantageously tangential to the zone 17 of the transverse portions 9 and to the central leg 10 of the beam 7. The central branch 10, of length L4 and of width W2, defines a useful zone 19 of the beam 7, corresponding to the zone of the beam 7 in contact with the magnetic element 8. In the case of the presence of the transition zones 18, the upper electrodes 11b and lower 11a do not extend, preferably, at the level of the transition zones 18 ( figure 7 ).

Chaque zone de transition 18, avec un profil elliptique, permet notamment de répartir les contraintes de manière homogène, tout en assurant une compacité maximale de l'inductance variable 1. Par ailleurs, une telle poutre 7 encastrée uniquement à ses extrémités (zones d'ancrage 16) permet également d'appliquer de plus fortes contraintes, de mieux maîtriser ces contraintes et permet également de réduire les capacités parasites.Each transition zone 18, with an elliptical profile, makes it possible in particular to distribute the stresses in a homogeneous manner, while ensuring maximum compactness of the variable inductance 1. Moreover, such a beam 7 embedded only at its ends (zones of anchoring 16) also makes it possible to apply higher stresses, to better control these constraints and also to reduce stray capacitances.

Dans les variantes de réalisation représentées sur les figures 8 et 9, les zones de transition 18 de la poutre 7 peuvent avoir un profil plus simple, par exemple rectangulaire (figure 8) ou trapézoïdal (figure 9). Dans une autre variante de réalisation non représentée, le profil des zones de transition 18 peut être elliptique et non tangent à la branche centrale 10 et aux parties transversales 9.In the variant embodiments represented on the Figures 8 and 9 , the transition zones 18 of the beam 7 may have a simpler profile, for example rectangular ( figure 8 ) or trapezoidal ( figure 9 ). In another variant embodiment, not shown, the profile of the transition zones 18 may be elliptical and non-tangent to the central branch 10 and to the transverse portions 9.

Dans la variante de réalisation représentée sur la figure 10, la poutre 7 de l'inductance variable 1 comporte une pluralité d'orifices 20, de préférence circulaires ou elliptiques, réalisés dans la zone 17 de génération de contraintes, adjacente à la zone d'ancrage 16, des parties transversales 9 de la poutre 7. De tels orifices 20 permettent notamment de faciliter le processus de libération de la poutre 7, lors de la fabrication de l'inductance variable 1, comme décrit ci- dessous.In the variant embodiment represented on the figure 10 , the beam 7 of the variable inductor 1 comprises a plurality of orifices 20, preferably circular or elliptical, made in the zone 17 of stress generation, adjacent to the anchoring zone 16, transverse portions 9 of the beam 7. Such openings 20 allow in particular to facilitate the release process of the beam 7, during the manufacture of the variable inductor 1, as described below.

Dans une autre variante de réalisation non représentée, des orifices peuvent également être réalisés dans les zones de transition 18 de la poutre 7, en complément des orifices 20 réalisés dans les zones 17 de génération de contraintes ou en remplacement de ceux-ci.In another variant embodiment, not shown, orifices may also be made in the transition zones 18 of the beam 7, in addition to the orifices 20 made in the stress generation zones 17 or in replacement thereof.

Dans d'autres variantes de réalisation non représentées, les parties transversales 9 peuvent être sous la forme de bandes de matériau parallèles et espacées de façon régulière, reliées à la branche centrale 10 et aux zones d'ancrage 16. De même, la branche centrale 10 peut également être formée de bandes de matériau parallèles, reliées aux parties transversales 9.In other embodiments not shown, the transverse portions 9 may be in the form of strips of parallel material and spaced regularly, connected to the central branch 10 and the anchoring zones 16. Similarly, the central branch 10 may also be formed of parallel strips of material, connected to the transverse portions 9.

Dans les modes particuliers de réalisation représentés sur les figures 11 à 13, uniquement la poutre 7 en matériau piézoélectrique et l'élément magnétique 8 associé, disposé sur la banche centrale 10 de la poutre 7, sont représentés. Sur la figure 11, l'élément magnétique 8 a une section de forme rectangulaire ou carrée. Sur la figure 12, l'élément magnétique 8 a une section de forme ellipsoïdale. Sur la figure 13, l'élément magnétique 8 se compose d'une pluralité d'éléments élémentaires disjoints, de préférence de forme rectangulaire ou ellipsoïdale, disposés de préférence côte à côte sur la branche centrale 10 de la poutre 7 et, de préférence, régulièrement.In the particular embodiments represented on the Figures 11 to 13 , only the beam 7 of piezoelectric material and the associated magnetic element 8, arranged on the central wall 10 of the beam 7, are shown. On the figure 11 the magnetic element 8 has a section of rectangular or square shape. On the figure 12 , the magnetic element 8 has a section of ellipsoidal shape. On the figure 13 , the magnetic element 8 consists of a plurality of disjoint elementary elements, preferably of rectangular or ellipsoidal shape, preferably arranged side by side on the central branch 10 of the beam 7 and, preferably, regularly.

D'une façon générale, dans le cas de l'utilisation d'un matériau magnétique uniaxial pour l'élément magnétique 8, l'axe d'anisotropie du matériau doit être parallèle ou perpendiculaire à l'axe longitudinal de référence A1 de la poutre 7 en matériau piézoélectrique (figure 11).Generally speaking, in the case of using a uniaxial magnetic material for the magnetic element 8, the axis of anisotropy of the material must be parallel or perpendicular to the longitudinal reference axis A1 of the beam 7 in piezoelectric material ( figure 11 ).

À titre d'exemple, pour une inductance variable 1 avec une poutre 7 comme décrit précédemment, un élément magnétique 8 de forme parallélépipédique et un bobinage 12 de type solénoïde, le nombre de spires est, par exemple, compris entre 3 et 20. La largeur de l'élément magnétique 8 est de l'ordre de 50 à 300µm, l'épaisseur de l'élément magnétique 8 est de l'ordre de 100nm à 2µm et la longueur de l'élément magnétique 8 est de l'ordre de 50 à 300µm.By way of example, for a variable inductance 1 with a beam 7 as previously described, a magnetic element 8 of parallelepipedal shape and a solenoid type winding 12, the number of turns is, for example, between 3 and 20. The width of the magnetic element 8 is of the order of 50 to 300 μm, the thickness of the magnetic element 8 is of the order of 100 nm to 2 μm and the length of the magnetic element 8 is of the order of 50 to 300μm.

En considérant les exemples de valeurs ci-dessus, les propriétés électromagnétiques de la bobine 12 (inductance, résistance, capacités, facteur de qualité, etc.) peuvent être calculées de manière fine par l'intermédiaire, par exemple, d'un logiciel de simulation par éléments finis, tel que le logiciel « HFSS » d'Ansoft. Par ailleurs, les électrodes inférieures 11 a et supérieures 11 b doivent être aussi fines que le permet le procédé de réalisation utilisé, par exemple de l'ordre de 50nm à 1µm.Considering the examples of values above, the electromagnetic properties of the coil 12 (inductance, resistance, capacitances, quality factor, etc.) can be finely calculated via, for example, finite element simulation, such as Ansoft's "HFSS" software. Moreover, the lower electrodes 11a and 11b must be as fine as the production method used, for example of the order of 50 nm to 1 μm, allows.

L'épaisseur de la poutre 7 est, par exemple, de l'ordre de 100nm à 2µm. De façon générale, l'épaisseur de la poutre 7 en matériau piézoélectrique est un compromis entre la tension d'actionnement, qui baisse avec l'épaisseur, et la transmission de la contrainte à l'élément magnétique 8, qui se dégrade si la poutre 7 est trop fine.The thickness of the beam 7 is, for example, of the order of 100 nm to 2 μm. In general, the thickness of the beam 7 made of piezoelectric material is a compromise between the operating voltage, which decreases with the thickness, and the transmission of the stress to the magnetic element 8, which degrades if the beam 7 is too thin.

À titre d'exemple, sur la figure 7, la branche centrale 10 de la poutre 7, constituant la zone utile 19 de la poutre 7, est, de préférence, à peine plus grande que l'élément magnétique 8, avec une marge de réalisation de l'ordre de 10µm, pour obtenir une amplitude de déformation maximale. Les dimensions de l'élément magnétique 8 fixent donc les dimensions correspondantes W2 et L4 de la branche centrale 10. La longueur L1 de la zone d'ancrage 16 peut alors être aussi petite que le permet la tenue mécanique de l'ancrage (dépendant notamment du procédé de fabrication utilisé).For example, on the figure 7 , the central branch 10 of the beam 7, constituting the useful zone 19 of the beam 7, is preferably slightly larger than the magnetic element 8, with a margin of embodiment of the order of 10 μm, to obtain a maximum deformation amplitude. The dimensions of the magnetic element 8 thus fix the corresponding dimensions W2 and L4 of the central branch 10. The length L1 of the anchoring zone 16 can then be as small as the mechanical strength of the anchorage (depending in particular on the manufacturing process used).

Pour dimensionner les longueurs L2 et L3, respectivement de la zone 17 et de la zone de transition 18 des parties transversales 9, ainsi que la largeur W1 des parties transversales 9, un logiciel de simulation par éléments finis peut être utilisé, tel que le logiciel « ANSYS ». De façon générale, une augmentation de la longueur L2 et de la largeur W1 tend à augmenter l'intensité des contraintes appliquées sur la zone utile 19 au détriment de l'encombrement, tandis qu'une augmentation de la longueur L3, qui est typiquement de l'ordre de 50µm à 300µm, améliore le caractère uniaxial et homogène des contraintes.To size the lengths L2 and L3, respectively of the zone 17 and the transition zone 18 of the transverse portions 9, as well as the width W1 of the transverse portions 9, a finite element simulation software can be used, such as the software "ANSYS". In general, an increase in the length L2 and the width W1 tends to increase the intensity of the stresses applied to the useful area 19 to the detriment of the bulk, while an increase in the length L3, which is typically the order of 50 .mu.m to 300 .mu.m, improves the uniaxial and homogeneous nature of the constraints.

D'une manière générale, la tension maximale appliquée doit générer des contraintes inférieures au seuil de plasticité des matériaux utilisés pour la poutre 7 en matériau piézoélectrique, l'élément magnétique 8 ou les électrodes d'actionnement 11. De même, dans le cas de l'application d'une contrainte en compression, la tension appliquée ne doit pas entraîner le flambement de la poutre 7 en matériau piézoélectrique.In general, the maximum applied voltage must generate stresses lower than the plasticity threshold of the materials used for the beam 7 made of piezoelectric material, the magnetic element 8 or the actuating electrodes 11. Similarly, in the case of the application of a stress in compression, the applied voltage must not cause the buckling of the beam 7 of piezoelectric material.

Sur la figure 14, la variante de réalisation de l'inductance variable 1 se distingue des modes de réalisation précédents par le nombre de branches centrales 10 de la poutre 7 en matériau piézoélectrique. L'inductance 1 comporte toujours deux parties transversales 9, reliées par deux branches centrales 10, coopérant chacune avec un élément magnétique 8 et, par exemple, avec un bobinage 12 de type solénoïde. Les électrodes inférieures 11 a et supérieures 11 b recouvrent, de préférence, la totalité de la surface des parties transversales 9 et les branches centrales 10 sont reliées aux parties transversales 9 par des zones de transition 18, de préférence, avec des profils elliptiques. Les bobinages 12 peuvent être connectés en série ou en parallèle.On the figure 14 , the variant embodiment of the variable inductor 1 is distinguished from the previous embodiments by the number of central branches 10 of the beam 7 of piezoelectric material. The inductor 1 always comprises two transverse portions 9, connected by two central branches 10, each cooperating with a magnetic element 8 and, for example, with a solenoid-type winding 12. The lower electrodes 11a and 11b preferably cover the entire surface of the transverse portions 9 and the central branches 10 are connected to the transverse portions 9 by transition zones 18, preferably with elliptical profiles. The coils 12 may be connected in series or in parallel.

L'utilisation d'une telle inductance 1 incluant plusieurs bobines 12 et plusieurs éléments magnétiques 8, gouvernés par le même dispositif d'actionnement, à savoir la même poutre 7 en matériau piézoélectrique, permet notamment de réduire l'encombrement total de l'inductance variable 1 et d'accroître la densité d'inductance totale.The use of such an inductor 1 including several coils 12 and several magnetic elements 8, governed by the same actuating device, namely the same beam 7 of piezoelectric material, allows in particular to reduce the overall size of the inductor variable 1 and increase the total inductance density.

Dans d'autres variantes de réalisation non représentées, les deux branches centrales 10 de la poutre 7 peuvent être associées à d'autres types d'éléments électriquement conducteurs, comme représentés sur les figures 4 à 6, et/ou à d'autres formes d'éléments magnétiques 8, comme représentés sur les figures 11 à 13, et/ou à d'autres profils de zones de transition 18, comme représentés sur les figures 7 à 10.In other non-illustrated embodiments, the two central branches 10 of the beam 7 can be associated with other types of electrically conductive elements, as shown in FIGS. Figures 4 to 6 , and / or other forms of magnetic elements 8, as shown in the Figures 11 to 13 , and / or other transition zone profiles 18, as shown in the Figures 7 to 10 .

Un procédé de fabrication d'une inductance variable intégrée 1 va être décrit plus en détail au regard des figures 15 à 20. Dans la description qui va suivre, le procédé de fabrication est destiné à la réalisation d'une inductance 1 avec une poutre profilée, comme décrit ci-dessus, comportant un bobinage 12 de type solénoïde (figure 3). Dans ce cas, la poutre 7 en matériau piézoélectrique est alors solidaire du substrat sur lequel est réalisée l'inductance, par l'intermédiaire d'extrémités latérales 23 réalisées avantageusement avec les mêmes couches de matériau que le bobinage 12, comme décrit ci-dessous et illustrées sur les figures 15 à 20.A method of manufacturing an integrated variable inductance 1 will be described in more detail with regard to Figures 15 to 20 . In the following description, the manufacturing method is intended for producing an inductance 1 with a profiled beam, as described above, comprising a solenoid-type winding 12 ( figure 3 ). In this case, the beam 7 of piezoelectric material is then integral with the substrate on which the inductance is formed, by means of lateral ends 23 advantageously made with the same layers of material as the winding 12, as described below. and illustrated on the Figures 15 to 20 .

Sur la figure 15, le procédé de fabrication comporte d'abord la formation sur un substrat 21, par exemple par électrolyse ou dépôt physique, d'une partie inférieure du bobinage 12, constituée d'un matériau à forte conductivité, par exemple en cuivre, en aluminium ou en or, puis l'encapsulation de ladite partie inférieure par une première couche sacrificielle 22, laissant affleurant les extrémités latérales 23. La couche sacrificielle 22 est, par exemple, en oxyde de silicium déposé par dépôt chimique (PECVD) ou en résine polymère. Une étape de planarisation mécanique ou mécano-chimique de la couche sacrificielle 22 peut également être réalisée.On the figure 15 the manufacturing method first comprises the formation on a substrate 21, for example by electrolysis or physical deposition, of a lower part of the winding 12, made of a material of high conductivity, for example copper, aluminum or in gold, then the encapsulation of said lower part by a first sacrificial layer 22, leaving flush with the lateral ends 23. The sacrificial layer 22 is, for example, made of silicon oxide deposited by chemical deposition (PECVD) or polymer resin. A mechanical or mechano-chemical planarization step of the sacrificial layer 22 can also be performed.

En variante, les extrémités latérales 23 peuvent être déposées, par exemple, par électrolyse et peuvent être constituées d'un matériau différent de celui de la partie inférieure du bobinage 12. La partie de la couche sacrificielle 22 entourant les extrémités latérales 23 peut être de nature différente de la partie entourant le bobinage 12 adjacent au substrat 21.Alternatively, the lateral ends 23 may be deposited, for example, by electrolysis and may consist of a material different from that of the lower part of the coil 12. The part of the sacrificial layer 22 surrounding the lateral ends 23 may be of different nature of the part surrounding the coil 12 adjacent the substrate 21.

Puis, le procédé comporte le dépôt d'un empilement d'une première couche 24 métallique et conductrice, destinée à former les électrodes inférieures 11a de l'inductance 1, d'une couche 25 en matériau piézoélectrique, destinée à former la poutre 7 de l'inductance 1, et d'une seconde couche 26 métallique et conductrice, destinée à former les électrodes supérieures 11 b de l'inductance 1 (figure 15).Then, the method comprises the deposition of a stack of a first metal and conducting layer 24 intended to form the lower electrodes 11a of the inductor 1, of a layer 25 of piezoelectric material, intended to form the beam 7 of inductance 1, and a second metallic and conductive layer 26 intended to form the upper electrodes 11b of inductor 1 ( figure 15 ).

À titre d'exemple, la couche 25 en matériau piézoélectrique est déposé par un procédé physique de déposition en phase vapeur (PVD) et les électrodes inférieures peuvent être en platine, pour une poutre en titano-zirconiate de plomb (PZT) piézoélectrique, ou en molybdène, pour une poutre en nitrure d'aluminium (AIN) piézoélectrique. Les électrodes supérieures peuvent être de nature différente des électrodes inférieures, par exemple en or, en cuivre ou en tungstène, etc. Des couches complémentaires de protection (non représentées), par exemple en or ou en tungstène, peuvent être prévues, notamment pour faciliter la libération ultérieure de l'inductance.For example, the layer 25 of piezoelectric material is deposited by a physical vapor deposition process (PVD) and the lower electrodes can be platinum, for a piezoelectric lead titano-zirconate (PZT) beam, or in molybdenum, for a piezoelectric aluminum nitride (AIN) beam. The upper electrodes may be different in nature from the lower electrodes, for example gold, copper or tungsten, etc. Additional protective layers (not shown), for example gold or tungsten, may be provided, in particular to facilitate the subsequent release of the inductor.

Sur les figures 16 et 17, avant l'élimination de la couche sacrificielle 22, une étape de gravure de l'empilement des couches 24, 25, 26 est ensuite réalisée, pour délimiter la forme caractéristique de la poutre 7 de l'inductance 1. La structuration des couches 24, 25, 26 peut être réalisée par une méthode chimique, de type attaque humide, ou physico-chimique, de type gravure sèche (RIE), ou bien par usinage ionique. Comme représenté sur la figure 16, le bord de l'empilement des trois couches 24, 25, 26 formant la poutre 7 est alors associé aux extrémités latérales 23.On the Figures 16 and 17 before the elimination of the sacrificial layer 22, a step of etching the stack of the layers 24, 25, 26 is then realized, to delimit the characteristic shape of the beam 7 of the inductance 1. The structuring of the layers 24, 25, 26 can be carried out by a chemical method, of wet etching type, or physicochemical type, dry etching type (RIE ), or by ion milling. As shown on the figure 16 the edge of the stack of the three layers 24, 25, 26 forming the beam 7 is then associated with the lateral ends 23.

Puis, une couche 27 en matériau magnétique uniaxial (figure 16) est ensuite déposée et gravée, afin de former l'élément magnétique 8 placé sur la branche centrale 10 de la poutre 7 formée au préalable (figure 17). À titre d'exemple, l'élément magnétique 8 peut être réalisé par dépôt physique en phase vapeur (PVD) d'un matériau en alliage à base de fer et/ou nickel et/ou cobalt. La couche 27 peut également être formée par un empilement de différentes couches diélectriques et conductrices.Then, a layer 27 of uniaxial magnetic material ( figure 16 ) is then deposited and etched in order to form the magnetic element 8 placed on the central branch 10 of the beam 7 previously formed ( figure 17 ). For example, the magnetic element 8 can be made by physical vapor deposition (PVD) of an alloy material based on iron and / or nickel and / or cobalt. The layer 27 may also be formed by a stack of different dielectric and conductive layers.

Sur la figure 17, la structuration des couches 24, 25, 26 par gravure permet ainsi d'obtenir la forme caractéristique de la poutre 7 avec deux parties transversales 9, perpendiculaires à l'axe de référence A1 de la poutre 7, et une branche centrale 10 sur laquelle est réalisé l'élément magnétique 8. Il ne reste alors plus qu'à fermer le bobinage 12, pour obtenir l'inductance 1 comme représentée sur la figure 20.On the figure 17 , the structuring of the layers 24, 25, 26 by etching thus makes it possible to obtain the characteristic shape of the beam 7 with two transverse portions 9, perpendicular to the reference axis A1 of the beam 7, and a central branch 10 on which the magnetic element 8 is formed. It then remains only to close the winding 12, to obtain the inductance 1 as shown in FIG. figure 20 .

Sur les figures 18 à 20, une seconde couche sacrificielle 28, identique ou de nature différente par rapport à la première couche sacrificielle 22, est ensuite déposée sur la poutre 7 formée au préalable, afin de pouvoir former la partie supérieure du bobinage 12 (figure 18). Enfin, l'élimination des couches sacrificielles 22 et 28 permet de libérer la structure ainsi formée. L'inductance 1 est alors suspendue et ancrée sur le substrat 21, par l'intermédiaire des extrémités latérales 23, comme représenté sur la figure 19.On the Figures 18 to 20 a second sacrificial layer 28, identical or different in nature from the first sacrificial layer 22, is then deposited on the previously formed beam 7 in order to form the upper part of the winding 12 ( figure 18 ). Finally, the elimination of the sacrificial layers 22 and 28 makes it possible to release the structure thus formed. The inductor 1 is then suspended and anchored on the substrate 21, via the lateral ends 23, as shown in FIG. figure 19 .

La formation de la partie supérieure du bobinage 12 peut être réalisé par gravure et reprise de contact à travers la couche sacrificielle 28, par une méthode chimique ou physico-chimique ou bien par usinage ionique. Le dépôt de la partie supérieure du bobinage 12 peut être réalisé par électrolyse et peut être réalisé à partir d'un matériau différent de celui de la partie inférieure du bobinage 12. La libération de la structure peut être réalisée par gravure sélective chimique, du type attaque humide, ou physico-chimique (du type RIE) des couches sacrificielles 22 et 28.The formation of the upper part of the winding 12 can be achieved by etching and resuming contact through the sacrificial layer 28, by a chemical or physicochemical method or by ion milling. The deposition of the upper part of the winding 12 can be achieved by electrolysis and can be made from a material different from that of the lower part of the coil 12. The release of the structure can be achieved by chemical selective etching, of the type wet or physico-chemical attack (of the RIE type) of the sacrificial layers 22 and 28.

Sur la figure 20, illustrant en vue de dessus l'inductance 1 terminée, le procédé selon l'invention permet d'obtenir une inductance 1 encastrée à ses deux extrémités, avec un profil caractéristique permettant de placer l'élément magnétique et le bobinage sensiblement dans sa partie centrale, afin de concentrer les contraintes et les rendre le plus uniaxial et homogène possibles. Un tel procédé de fabrication utilise ainsi des techniques de fabrication issues de la microélectronique et adaptées pour les microsystèmes.On the figure 20 illustrating, in plan view, inductance 1 completed, the method according to the invention makes it possible to obtain an inductance 1 embedded at its two ends, with a characteristic profile making it possible to place the magnetic element and the winding substantially in its central part. , in order to concentrate the constraints and make them as uniaxial and homogeneous as possible. Such a manufacturing method thus uses manufacturing techniques derived from microelectronics and adapted for microsystems.

Une telle inductance variable 1 intégrée, selon les différents modes de réalisation décrits ci-dessus, permet donc d'appliquer une contrainte homogène et uniaxiale - en tension ou en compression - sur l'élément magnétique et de maximiser la valeur de ces contraintes, pour une tension d'actionnement donnée, grâce notamment à la forme et au profil caractéristiques de sa poutre.Such integrated inductance 1 integrated, according to the different embodiments described above, therefore allows to apply a homogeneous and uniaxial stress - in tension or compression - on the magnetic element and to maximize the value of these constraints, for a given actuation voltage, thanks in particular to the characteristic shape and profile of its beam.

Par ailleurs, l'utilisation d'une poutre en matériau piézoélectrique libérée et encastrée à ses deux extrémités permet d'améliorer les propriétés mécaniques et électromagnétiques de l'inductance variable selon l'invention, de manière à obtenir de fortes variations réversibles d'inductance, continues ou discontinues, avec de faibles tensions d'actionnement, tout en préservant de bonnes propriétés fréquentielles, notamment en hautes fréquences.Furthermore, the use of a beam of piezoelectric material released and embedded at its two ends makes it possible to improve the mechanical and electromagnetic properties of the variable inductor according to the invention, so as to obtain large reversible variations in inductance. , continuous or discontinuous, with low operating voltages, while preserving good frequency properties, especially at high frequencies.

L'invention n'est pas limitée aux différents modes de réalisation décrits ci-dessus. Les valeurs de largeurs et de longueurs des différentes zones de la poutre 7 sont non limitatives et dépendent notamment de la taille souhaitée de l'inductance variable 1 et de la valeur d'inductance recherchée. Les électrodes 11 peuvent s'étendre au-dessus des zones de transition 18 de la poutre 7 (figure 7). Dans la variante de réalisation représentée sur la figure 14, l'inductance 1 peut comporter plus de deux branches centrales 10, toutes associées à un élément magnétique 8 correspondant et à un élément électriquement conducteur correspondant, de préférence de type bobinage solénoïde.The invention is not limited to the various embodiments described above. The values of widths and lengths of the different zones of the beam 7 are nonlimiting and depend in particular on the desired size of the variable inductance 1 and the desired inductance value. The electrodes 11 can extend above the transition zones 18 of the beam 7 ( figure 7 ). In the variant embodiment represented on the figure 14 the inductor 1 may comprise more than two central branches 10, all associated with a corresponding magnetic element 8 and a corresponding electrically conductive element, preferably of the solenoid winding type.

Dans la variante de réalisation représentée sur la figure 21, la poutre 7 en matériau piézoélectrique comporte une première partie transversale 9 en matériau piézoélectrique, comme représentée sur la figure 7, coopérant avec les électrodes inférieures 11 a et supérieures 11 b, et une deuxième partie transversale 9, de longueur très inférieure, comportant uniquement la zone d'ancrage 16 de la poutre 7 au substrat. Le principe de fonctionnement de l'inductance 1 est le même, avec un bobinage 12 de type solénoïde et un élément magnétique 8, placé sur la branche centrale 10 de la poutre 7.In the variant embodiment represented on the figure 21 , the beam 7 of piezoelectric material comprises a first transverse portion 9 of piezoelectric material, as shown in FIG. figure 7 , cooperating with the lower electrodes 11a and 11b, and a second transverse portion 9, of much smaller length, comprising only the anchoring zone 16 of the beam 7 to the substrate. The operating principle of the inductor 1 is the same, with a solenoid-type winding 12 and a magnetic element 8, placed on the central branch 10 of the beam 7.

Dans une autre variante de réalisation représentée sur la figure 22, la largeur W1 des parties transversales 9 peut être inférieure à la largeur W3 des zones d'ancrage 16 correspondantes. Par ailleurs, la largeur W2 de la branche centrale 10, sur laquelle est placé l'élément magnétique 8, peut être supérieure à la largeur W1 des parties transversales 9. D'une manière générale, les largeurs W1, W2 et W3 des différentes zones de la poutre 7 ne sont pas liées entre elles et la poutre 7 peut prendre une tout autre forme complexe.In another variant embodiment shown on the figure 22 the width W1 of the transverse portions 9 may be smaller than the width W3 of the corresponding anchoring zones 16. Furthermore, the width W2 of the central branch 10, on which the magnetic element 8 is placed, may be greater than the width W1 of the transverse portions 9. In general, the widths W1, W2 and W3 of the different zones of the beam 7 are not interconnected and the beam 7 can take a quite other complex shape.

Dans une autre variante de réalisation non représentée, la poutre 7 en matériau piézoélectrique et l'élément magnétique 8 associé peuvent être encapsulés dans des couches 22 et 28 en matériau isolant et suffisamment mou, par exemple une résine polymère à faible constante diélectrique, pour permettre une déformation suffisante de la poutre 7 par rapport au substrat, sans avoir besoin de retirer les couches 22 et 28. La libération de la poutre 7 n'est alors plus nécessaire.In another variant embodiment not shown, the beam 7 made of piezoelectric material and the associated magnetic element 8 can be encapsulated in layers 22 and 28 of insulating material and sufficiently soft, for example a low dielectric constant polymer resin, to enable a sufficient deformation of the beam 7 relative to the substrate, without the need to remove the layers 22 and 28. The release of the beam 7 is then no longer necessary.

D'une manière générale, l'invention s'applique à tout dispositif magnétique à réponse variable en forme de poutre 7 comportant un élément en matériau piézoélectrique. L'élément en matériau piézoélectrique peut être constitué par la poutre 7 complète ou uniquement par des parties de la poutre, à savoir une partie d'une partie transversale 9, une partie transversale 9 complète ou les deux parties transversales 9, la branche centrale 10 et les zones de transition 18 pouvant être alors réalisées en un autre matériau.In general, the invention applies to any magnetic device with a variable response in the form of a beam 7 comprising an element made of piezoelectric material. The element made of piezoelectric material may consist of the complete beam 7 or only of parts of the beam, namely a part of a transverse part 9, a complete transverse part 9 or the two transverse parts 9, the central branch 10 and the transition zones 18 can then be made of another material.

L'invention s'applique notamment à tout type de circuit électronique reconfigurable, pour lequel une limitation du nombre de composants est recherchée en utilisant des composants ajustables. Le principe utilisé pour faire varier la perméabilité dynamique, ainsi que son application pratique, ne sont pas limités en termes de valeurs d'inductance ou de fréquence de fonctionnement. L'invention s'applique donc à tous les domaines où une variation de perméabilité dynamique continue (ou discontinue) et réversible est nécessaire, avec un actionnement de très faible puissance, notamment les circuits multibandes reconfigurables, l'adaptation fine d'impédance et les oscillateurs accordables.The invention applies in particular to any type of reconfigurable electronic circuit, for which a limitation of the number of components is sought by using adjustable components. The principle used to vary the dynamic permeability, as well as its practical application, are not limited in terms of inductance values or operating frequency. The invention therefore applies to all areas where a continuous (or discontinuous) and reversible dynamic permeability variation is necessary, with very low power operation, in particular reconfigurable multiband circuits, fine impedance matching and tunable oscillators.

L'invention s'applique également à d'autres types de dispositifs magnétiques à réponse variable, en fonction de la manière dont l'élément magnétique 8 est associé à l'élément électriquement conducteur (le bobinage 12 par exemple). De manière générale, l'élément magnétique doit être mécaniquement solidaire de la poutre en matériau piézoélectrique, afin que les déformations de ladite poutre engendrent une variation des propriétés magnétiques de l'élément magnétique.The invention is also applicable to other types of magnetic devices with variable response, depending on how the magnetic element 8 is associated with the electrically conductive element (the coil 12 for example). In general, the magnetic element must be mechanically secured to the beam of piezoelectric material, so that the deformations of said beam generate a variation of the magnetic properties of the magnetic element.

Ainsi, dans le cas où l'élément électriquement conducteur est placé à distance de l'élément magnétique, uniquement d'un côté de l'élément magnétique, par exemple dans le cas de l'élément en forme de méandres 13 (figure 4), en forme de lignes 14 (figure 5) ou en forme de spirale 15 (figure 6), ou de part et d'autre de l'élément magnétique 8, par exemple dans le cas de l'élément en forme de solénoïde 12 (figure 3), le dispositif magnétique est alors une inductance variable.Thus, in the case where the electrically conductive element is placed at a distance from the magnetic element, only on one side of the magnetic element, for example in the case of the meandering element 13 ( figure 4 ), in the form of lines 14 ( figure 5 ) or in the form of a spiral 15 ( figure 6 ), or on either side of the magnetic element 8, for example in the case of the solenoid-shaped element 12 ( figure 3 ), the magnetic device is then a variable inductance.

Dans le cas où l'élément électriquement conducteur n'est placé que d'un côté de l'élément magnétique, il est également possible de réaliser des éléments de ligne de transmission, tels que des résonateurs, des déphaseurs, des coupleurs, des antennes, des filtres, etc.In the case where the electrically conductive element is placed only on one side of the magnetic element, it is also possible to produce transmission line elements, such as resonators, phase shifters, couplers, antennas , filters, etc.

Sur la figure 23, dans le cas où un élément électriquement conducteur 29 est placé à la fois entre la branche centrale 10 de la poutre 7 et l'élément magnétique 8 et au-dessus de l'élément magnétique 8, de préférence au contact de part et d'autre de l'élément magnétique 8, il est alors possible de réaliser un oscillateur de spin 1.On the figure 23 , in the case where an electrically conductive element 29 is placed both between the central leg 10 of the beam 7 and the magnetic element 8 and above the magnetic element 8, preferably in contact with each other and with other of the magnetic element 8, it is then possible to make a spin oscillator 1.

Claims (26)

  1. A variable-response magnetic device (1) integrated on a substrate (21) and comprising at least one element made of piezoelectric material associated with actuating electrodes (11), and at least one magnetic element (8) able to deform under the stress of the element made of piezoelectric material,
    a device characterized in that it is in the form of a beam (7), movable with respect to the substrate (21) and comprising two transverse parts (9) of predetermined width (W1), along a reference longitudinal axis (A1), and in that:
    - the piezoelectric material element is consituted by at least one part of a transverse part (9),
    - each transverse part (9) comprises a zone for mechanical anchoring (16) on the substrate (21),
    - and the transverse parts (9) are connected by at least one central branch (10), of predetermined width (W2), on which the magnetic element (8) is arranged.
  2. The device according to claim 1, characterized in that the width (W2) of the central branch (10) is smaller than the width (W1) of the transverse parts (9).
  3. The device according to one of claims 1 and 2, characterized in that the two transverse parts (9) are made of piezoelectric material.
  4. The device according to any one of claims 1 to 3, characterized in that the central branch (10) is made of piezoelectric material.
  5. The device according to any one of claims 1 to 4, characterized in that the actuating electrodes (11a, 11b) extend partially on the surface of the transverse parts (9) of the beam (7).
  6. The device according to claim 5, characterized in that the actuating electrodes (11a, 11b) are situated on each side of the piezoelectric material element.
  7. The device according to any one of claims 1 to 6, characterized in that each transverse part (9) is extended by a transition zone (18) extending up to the corresponding central branch (10).
  8. The device according to claim 7, characterized in that the transition zone (18) is of variable cross-section.
  9. The device according to claim 7, characterized in that the transition zone (18) has an elliptical shape tangent to the associated transverse part (9) and central branch (10).
  10. The device according to any one of claims 7 to 9, characterized in that the transition zone (18) comprises a plurality of holes.
  11. The device according to any one of claims 1 to 10, characterized in that each transverse part (9) comprises a plurality of holes (20).
  12. The device according to any one of claims 1 to 11, characterized in that the magnetic element (8) comprises a uniaxial magnetic material having an axis of anisotropy parallel to the reference axis (A1) of the beam (7).
  13. The device according to any one of claims 1 to 12, characterized in that the magnetic element (8) comprises a uniaxial magnetic material having an axis of anisotropy perpendicular to the reference axis (A1) of the beam (7).
  14. The device according to any one of claims 1 to 13, characterized in that the magnetic element (8) has a cross-section of substantially rectangular shape.
  15. The device according to any one of claims 1 to 13, characterized in that the magnetic element (8) has a cross-section of substantially ellipsoid shape.
  16. The device according to any one of claims 1 to 15, characterized in that the magnetic element (8) is composed of a plurality of non-joined elemental magnetic elements arranged side by side on the central branch (10) of the beam (7).
  17. The device according to any one of claims 1 to 16, characterized in that it comprises at least one electrically conducting element associated with the magnetic element (8).
  18. The device according to claim 17, characterized in that the electrically conducting element is a solenoid coil (12).
  19. The device according to claim 18, characterized in that the coil (12) surrounds the magnetic element (8).
  20. The device according to claim 17, characterized in that the electrically conducting element is a wire in the form of a serpentine (13).
  21. The device according to claim 17, characterized in that the electrically conducting element is a wire in the form of lines (14).
  22. The device according to claim 17, characterized in that the electrically conducting element is a wire in the form of a spiral (15).
  23. The device according to any one of claims 20 to 22, characterized in that the electrically conducting element is located at a distance from the magnetic element (8).
  24. The device according to claim 23, characterized in that the electrically conducting element is arranged on one side of the magnetic element (8) only.
  25. The device according to claim 17, characterized in that the electrically conducting element (29) is arranged on both sides of and in contact with the magnetic element (8).
  26. The device according to any one of claims 1 to 25, characterized in that the beam (7) is encapsulated in a soft insulating material.
EP07354048A 2006-09-12 2007-09-06 Integrated magnetic device with piezoelectric control Active EP1901317B1 (en)

Applications Claiming Priority (1)

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FR0607966A FR2905793B1 (en) 2006-09-12 2006-09-12 INTEGRATED MAGNETIC DEVICE CONTROLLED PIEZOELECTRICALLY

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EP1901317A1 (en) 2008-03-19
JP2008072120A (en) 2008-03-27
JP5058732B2 (en) 2012-10-24
US20080068759A1 (en) 2008-03-20
FR2905793A1 (en) 2008-03-14
US7608975B2 (en) 2009-10-27
FR2905793B1 (en) 2008-10-17

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