Mechanical microsystem and related manufacturing method

Abstract

The invention first relates to a mechanical microsystem (1) comprising a pair of elastically deformable elements (11, 12), a mechanical hinge (13) connecting the deformable elements together, and at least two electroactive layers (14, 15). The microsystem is configured so that a deformation of one of said deformable elements out of the plane from a rest position in which the deformable elements fall into the plane induces a circulation of electric current in one of the two electroactive layers, and / or vice versa. Each deformable element has a front face (111, 121) and a back face (112, 122) opposite each other and substantially parallel to the plane. A first electroactive layer is arranged with the first deformable element on its back face (112), and a second electroactive layer, different from the first electroactive layer, has a second deformable element different from the first deformable element on its front face 121. The mechanical microsystem is capable of generating movements of the deformable elements out of the rest plane which are antagonistic to achieve a bimetallic effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mechanical microsystems. Such systems can be defined as objects of which at least one characteristic dimension is of the order of microns and which are capable of local deformation. Mechanical microsystems are configured to implement sensor functions, i.e. to convert a physical quantity (such as a force and / or a deformation) into an electrical signal; and / or, conversely, to implement actuator functions, i.e. to convert an electrical signal into a physical quantity (such as a force and / or a deformation). The type of mechanical microsystems in question specifically includes:

[0002] a at least one so-called electroactive portion, which converts a force and / or a deformation into an electrical signal and, conversely, an electrical signal into a force and / or a deformation; and

[0003] b at least one so-called passivation portion, on which a force and / or a deformation applied is converted into an electrical signal or controlled by the application of a voltage on the electroactive portion.

[0004] These conversions can be achieved by physical phenomena such as swelling, electrostriction, piezoelectric effect, state or phase change, thermoelectric effect, pyroelectric effect, etc.

[0005] The present application has a particularly advantageous application in its integration with electromechanical microsystems (or MEMS), nanoelectromechanical systems (or NEMS), transducers, sensors, actuators, microfilms, microbeams, microengines, etc. BACKGROUND

[0006] Currently, known embodiments of microbeams or microfilms comprise the deposition of an electroactive material on a flexible layer on the basis of a passivation material.

[0007] More particularly, known mechanical microsystems comprise:

[0008] a at least two flexible beams made of a so-called passivation material, such as silicon;

[0009] b a mechanical hinge which binds together said at least two beams; and

[0010] c at least two so-called electroactive layers, each of which is based on a so-called electroactive material, for example a piezoelectric material;

[0011] At least one electroactive layer is arranged on each of said at least two beams.

[0012] When such a mechanical microsystem is used as an actuator, the application of a voltage between the terminals of one of the electroactive layers causes the beam on which the electroactive layer is deposited to contract or expand in the direction of the electric polarization. A bimetallic effect is thus produced.

[0013] More specifically, in the absence of an applied voltage, such as a mechanical microsystem has a substantially planar symmetry, when a voltage is applied, it has a curved symmetry. Indeed, each beam undergoes a displacement at the level of the applied voltage, which drives the beam out of a so-called rest plane, in which the mechanical microsystem enters in the absence of an applied voltage.

[0014] Moreover, piezoelectric layers based on lead zirconate titanate (PZT) are known to be of interest in terms of mass and electromechanical conversion yield. However, ferroelectric electroactive layers only contract whatever the polarization direction of the electric field applied thereon. In this case, each beam to which a voltage is applied always moves towards one and the same half-space defined by the rest plane.

[0015] It is thus possible to generate a displacement out of the beam plane in two directions, with the possibility of depositing on one and the same substrate two PZT-based layers stacked one on top of the other and separated by a Pt / Ti electrode layer (see in particular J. Tsaur et al., "2D scanning mirror using double layer PZT film", 2D microscanner actuated by double layer PZT derived by sol-gel, MEMS 2002, AIST, Tsukuba City, Japan). In this way, by applying a voltage only on a first of the two PZT layers, it is possible to obtain a displacement of the beam opposite to that obtained by applying a voltage only on a second of the two PZT layers. Thus, in the absence of an applied voltage, the beam is specific to move in two half-spaces defined by a plane (in which the mechanical microsystem substantially falls) and in which, moreover, the method for forming such a mechanical microsystem can comprise locally etching the substrate over the entire thickness of the substrate, so that the neutral fiber of such a mechanical microsystem thus advantageously passes between the two PZT-based layers.

[0016] However, in the prior art, it is difficult to implement a double series of PZT deposition.

[0017] It is therefore an object of the present application to propose a mechanical microsystem having at least the same advantages and in particular having a deformable element capable of moving in at least two directions and which is easier to manufacture and / or reduced in cost.

[0018] Other objects, features and advantages of the present application will appear more clearly from the following description and the annexed drawings. It will be understood that other advantages can also be combined. SUMMARY

[0019] To achieve this object, according to a first aspect, the present application relates to a microsystem comprising:

[0020] a pair of elastically deformable elements;

[0021] b a mechanical hinge joining together the deformable elements; and

[0022] c at least two electroactive layers,

[0023] The mechanical microsystem is configured so that starting from a rest position in which the deformable elements substantially fall into one and the same so-called rest plane, the deformation of at least one of the deformable elements at least partially moves it from the rest position outside the rest plane to induce a circulation of electric current in at least one of the at least two electroactive layers, and / or vice versa,

[0024] Each deformable element has a front face and a back face opposite to each other, the two faces being substantially parallel to the rest plane,

[0025] The mechanical microsystem is substantially configured so that a first layer of the at least two electroactive layers is arranged with a first deformable element of the pair of deformable elements on the back face of the first deformable element, and a second electroactive layer of the at least two electroactive layers, different from the first layer, is arranged with a second deformable element of the pair of deformable elements, different from the first deformable element, on the front face of the second deformable element.

[0026] The front face / back face of the deformable elements has the same orientation as the orientation of the back face / front face of the deformable elements.

[0027] The invention according to a first aspect thus proposes a mechanical microsystem capable of causing the deformable elements to move outside the rest plane, the movements being antagonistic to produce a bimetallic effect.

[0028] Thanks to these antagonistic movements of the deformable elements, it is allowed to create an angle between the two deformable elements of the same pair, i.e. at the intermediate portion, called mechanical hinge or "ball" of the device, the amplitude of which is substantially equal to that offered by a mechanical microsystem with non-antagonistic movements and / or which is multiplied with respect to the displacement of the same pair of deformable elements, but with an electrical energy saving and / or an amplitude of the movement much greater than the equivalent actuation tension.

[0029] In addition, the neutral fiber of the mechanical microsystem according to the first aspect of the invention advantageously passes between each deformable element and the electroactive layer arranged with this deformable element, thus allowing the bimetallic effect to be maximized.

[0030] A second aspect of the invention relates to a method of manufacturing a mechanical microsystem, comprising:

[0031] a providing a substrate based on a first material, forming at least one first electro-active layer and a second electro-active layer on the front side of the substrate, spaced apart from each other, the substrate further comprising an embedded etch stop layer having an opening just underneath (or flush with) at least one portion of the first electro-active layer, and preferably no opening underneath (or flush with) the second electro-active layer,

[0032] b depositing at least at the portion of the first electro-active layer underneath (or flush with) a so-called passivation layer based on a second material, leaving at least a portion of the second electro-active layer uncovered by said passivation layer,

[0033] c etching at least one central portion of the substrate on the back side of the substrate until the entire thickness of the substrate at the portion underneath (or flush with) the etch stop layer is removed, and until the entire thickness of the substrate at the right of the opening the etch stop layer has is removed,

[0034] whereby the passivation layer forms a first elastically deformable element arranged together with the first electro-active layer,

[0035] whereby the etched substrate forms a second elastically deformable element arranged together with the second electro-active layer, and

[0036] whereby at least one of the etched substrate and the passivation layer forms a mechanical hinge connecting the first and second deformable elements together.

[0037] The method thus allows to manufacture a mechanical microsystem that provides the sought after simpler and / or less costly functionality, in particular due to the possibility to deposit the electro-active layers in a synchronized manner. BRIEF DESCRIPTION OF DRAWINGS

[0038] The objects, aims, as well as the features and advantages of the present application will become more apparent from the following detailed description of embodiments thereof, given as a non-restrictive example with reference to the annexed drawings, in which:

[0039] Figure 1 a cross-sectional view of a mechanical microsystem according to one embodiment of the first aspect of the present application is schematically shown;

[0040] Figures 2 to 7 different steps of a method for manufacturing a mechanical microsystem according to one embodiment of the first aspect of the present application are schematically shown, each of the schematic views showing a cross-sectional view of a different stage of manufacturing the mechanical microsystem; and Figure 1

[0041] Figure 8 a cross-sectional view of a mechanical microsystem according to one embodiment of the first aspect of the present application is schematically shown; ​

[0042] The drawings are given as examples and do not constitute a limitation on the application. The drawings constitute schematic representations of principles, intended to facilitate the understanding of the application, and are not necessarily to scale with actual applications. In particular, the thicknesses of the different layers such as shown do not represent real thicknesses. DETAILED DESCRIPTION

[0043] Before beginning a detailed description of embodiments of the application, the optional features set out below can be used in combination or alternatively.

[0044] Optionally, the mechanical microsystem according to the first aspect of the application also has at least one of the following features:

[0045] The mechanical hinge can bind each pair of deformable elements together by one of the distal ends of each pair of deformable elements;

[0046] Each pair of deformable elements can be placed opposite each other with respect to the mechanical hinge;

[0047] Preferably, a single electroactive layer is arranged with each deformable element;

[0048] The mechanical microsystem can also comprise a rigid frame, the deformable elements being firmly bound to the rigid frame by the proximal end, the mechanical hinge binding a pair of deformable elements together by its distal end, and the mechanical hinge can be flexible, allowing the pair of deformable elements to move outside the rest plane;

[0049] The at least one electroactive layer, preferably each electroactive layer, is based on an electroactive material chosen from the following: piezoelectric materials, ferromagnetic materials and PTZ-based materials. A non-exhaustive list of ferromagnetic materials considered includes, for example, the perovskite ABO3family, for example PbZrTiO3(PZT), PbMgNbTiO3(PMNT), PbMgNbO3-PbTiO3(PMN-PT), KNaNbO3(KNN), BaSrTiO3(BST), BaCaZrTiO3(BCTZ), BaTiO3(BT), NaBiTiO3(NBT), NaBiTiO3-BaTiO3(NBT-BT), BiFeO3and ferromagnetic polymers such as polyvinylidene (or PVDF). Non-ferromagnetic piezoelectric materials are also considered, such as AIN, Sc-doped AIN, ZnO. The mechanical microsystem with a PZT-based electroactive layer is of particular interest, since this type of electroactive layer has good quality and conversion efficiency, but, like all ferroelectric materials, it can only contract under the action of an electric field, thus not allowing the deformable elements to deform in multiple directions;

[0050] The deformable elements and the mechanical hinge can be based on the same material, for example a silicon-based material;

[0051] The mechanical microsystem can further comprise at least one intermediate layer located between the first electrically active layer and the first deformable element and / or on either side of said first electrically active layer and first deformable element, and / or between the second electrically active layer and the second deformable element and / or on either side of said second electrically active layer and second deformable element. Said at least one intermediate layer can be configured to implement an electrical contact point, in particular for applying and / or measuring a current circulation in at least one of the first and second electrically active layers arranged with said at least one intermediate layer. As a complement or alternative to the preceding feature, said at least one intermediate layer can be arranged such that a neutral fiber of the mechanical microsystem is located between each electrically active layer and the deformable element arranged with this electrically active layer;

[0052] The mechanical microsystem can further comprise at least one pair of second deformable elements. Said at least one pair of second deformable elements can be joined together by a mechanical hinge different from the mechanical hinge joining the first pair of deformable elements together. Alternatively or in combination with the preceding feature, the pair of deformable elements can be arranged according to a rotational symmetry around the mechanical hinge. Strictly speaking, the mechanical microsystem according to the first aspect of the application can further comprise one or more deformable elements that do not form part of a pair of deformable elements.

[0053] At least one of the deformable elements can be chosen from the group consisting of: a beam and a membrane;

[0054] Each pair of deformable elements can have substantially identical geometry;

[0055] The mechanical hinge can comprise at least one structure, in particular constituted by the removal of material, located in a region of the mechanical microsystem between each pair of deformable elements. Said at least one structure preferably gives the mechanical hinge a greater flexibility than that characterizing the deformable elements, in particular when the mechanical microsystem comprises a rigid frame to which the deformable elements are firmly connected.

[0056] Optionally, the manufacturing method according to the second aspect of the application can further comprise at least one of the following features:

[0057] The formation of the first and second electrically active layers can comprise the following steps:

[0058] a. a single deposition of a film made of electrically active material on the front face of the substrate, then

[0059] b. etching of the deposited film, if necessary implementing an etching mask, to obtain and separate therebetween the first and second electrically active layers.

[0060] It should be noted that if the first and second electroactive layers are manufactured simultaneously by such a film made by a single deposition of electroactive material, the deposition of said film itself can comprise a certain number of steps and is therefore relatively time-consuming. This illustrates the importance of the present application with respect to the prior art mentioned in the background of the application, according to which two depositions of a film made of electroactive material would be carried out, which is more cumbersome with respect to the single deposition according to the method according to the above-mentioned features.

[0061] Only the central portion of the substrate can be etched, so that the remaining periphery of the substrate forms a rigid frame, the deformable elements are firmly bound to the rigid frame by their proximal end, the mechanical hinges bind the deformable elements together by their distal end, and the mechanical hinges can be flexible so as to allow each deformable element to move out of the rest plane. The manufacturing method can also comprise a step of structuring the mechanical hinges, in particular by removing one of the material of the substrate and / or of the passivation layer located between the deformable elements. Said at least one structure is preferably structured so that the flexibility of the mechanical hinges is greater than the flexibility characterizing the deformable elements in at least one given direction.

[0062] The manufacturing method can also comprise a deposition of at least one intermediate layer between the first electroactive layer and the first deformable element and / or on either side of said first electroactive layer and first deformable element, and / or between the second electroactive layer and the second deformable element and / or on either side of said second electroactive layer and second deformable element. The deposition of said at least one intermediate layer is structured so as to implement an electrical contact point, in particular for applying and / or measuring a current cycle in the electroactive layer arranged with said at least one intermediate layer, if necessary;

[0063] The deposition of the passivation layer is structured so that the thickness of the passivation layer is substantially equal to the depth of embedding of the etching stop layer from its front face in the substrate. This method thus allows to provide substantially identical geometries for each pair of deformable elements. In this way, after the application of the same current to each electroactive layer arranged with said deformable elements, a same amplitude of deformation of each of a pair of deformable elements can be expected, or a measurement of the same current cycle in each electroactive layer can be expected after a same deformation amplitude of said deformable elements.

[0064] By film based on a material A, it is meant a film comprising this material A and optionally other materials.

[0065] It should be noted that, within the scope of the present application, the term "electroactive" and its derivatives refer to the property of an element designed to act as an element capable of converting an electrical signal into a plurality of physical quantities and / or vice versa. This conversion can be achieved by piezoelectricity, by thermal expansion difference, by electrostriction, etc.

[0066] It is specified that within the scope of the present invention, the term "passivated" and its derivatives mean the property of an element such that, within the scope of the present invention, the material is not designed to be used as an electroactive element.

[0067] "Neutral fiber" means a line or surface located inside a deformed (e.g. folded or bent) portion on which neither traction nor compression stress is exerted. More specifically, during the bending of a beam or membrane under the action of a force, the stiffness of the material causes mechanical stresses to appear on the surface, so that the thickness decreases to change the marking on the opposite surface. Thus, there is a fictitious surface in the material on which the stresses are zero. This surface is defined as the neutral fiber, being on one side of which the material is compressed and on the other side of which the material is stretched.

[0068] "Beam" means a deformable element of elongated shape, optionally curved (even folded), the deformation (preferably elastic) of which is used as an actuator or a sensor.

[0069] "Membrane" means a deformable element comprising a flexible wall, the deformation (preferably elastic) of which is used as an actuator or a sensor.

[0070] "Mechanical hinge" means a mechanical junction area between at least two deformable elements of the same pair.

[0071] Reference will be made subsequently Figures 2 to 7 A preferred embodiment of the second aspect of the invention will first be described in detail.

[0072] The second aspect of the invention relates to a method for manufacturing a mechanical microsystem 1 according to the first aspect of the invention.

[0073] The manufacturing method first comprises a step of providing a substrate 101. The substrate 101 is based on a first material. The first material is a so-called passivated material. This can be for example silicon (and preferably monocrystalline silicon). More specifically, the substrate 101 comprises or consists of a silicon wafer.

[0074] On the front face 1011 of the provided substrate 101, at least one first electroactive layer 14 and a second electroactive layer 15 are formed, spaced apart from each other. The first and second electroactive layers 14, 15 are formed in a pair. More generally, the two layers form a first pair of electroactive layers, so that the provided substrate 101 can comprise a plurality of pairs of electroactive layers.

[0075] In addition, the substrate 101 comprises an embedded etch stop layer 102. As will be seen below, the depth of embedding of the etch stop layer 102 in the substrate 101 affects the performance of the manufactured mechanical microsystem 1.

[0076] The etch stop layer 102 comprises an opening 3 in its surface area. More specifically the opening 3 is located directly below or in line with at least a portion of the first electro-active layer 14. Preferably the opening 3 of the etch stop layer 102 does not extend below the second electro-active layer 14. More specifically the etch stop layer preferably does not have an opening directly below (or in line with) the second electro-active layer 15.

[0077] Accordingly, this first step of the method according to the preferred embodiment of the second aspect of the present application comprises providing a stack of layers of micrometer thickness as shown in any one of Figure 4 and 5 .

[0078] More specifically, the first step of the method according to the preferred embodiment of the second aspect of the present application comprises the following sub-steps as shown in Figures 2 to 6

[0079] a. providing a silicon wafer 100;

[0080] b. generating a silicon oxide layer on the front side of the wafer as the etch stop layer 102, for example by direct oxidation of the silicon in a furnace under controlled environment and pressure;

[0081] c. making an opening in the generated silicon oxide layer 102 as the opening 3 as described above, for example by a chemical etching method, by a photolithographic or by a reactive ion etching made mask. The thus obtained stack is shown in Figure 2

[0082] d. depositing a silicon layer on the silicon oxide layer 102 and the opening 3, preferably over the entire area of the silicon wafer 100, for example by chemical vapor deposition. The silicon layer is preferably deposited to have a substantially flat front side. Preferably the silicon layer is deposited on the opening 3 before the exposed silicon of the silicon wafer 100 is oxidized;

[0083] e. generating a silicon oxide layer on the surface of the previously deposited silicon layer, for example by plasma enhanced chemical vapor deposition (PEVCD). The thus obtained stack is shown in Figure 3

[0084] ​​​f. At least one film is deposited on the silicon layer previously deposited and oxidized on the surface, this film being based on an electroactive material intended to constitute each of the electroactive layers 14, 15 described above. Preferably, a single film with electroactive material is deposited in this step. Thus, the tedious work of depositing a bilayer based on at least one electroactive material is avoided. This deposition step can also include the deposition of an upper conductive layer and a lower conductive layer, for example a platinum-based layer, on either of the layers based on electroactive material, for example by physical vapor deposition. Each of these conductive layers is intended to constitute as many electrodes as there are electroactive layers of the mechanical microsystem;

[0085] g. At least the layers based on electroactive material are etched, and if necessary, the conductive layers are also etched, so as to form at least two electroactive layers 14, 15 on the front face 1011 of the substrate 101, if necessary sandwiched between electrodes formed by etching the conductive layers. The stack thus obtained is as shown in Figure 4 ;

[0086] h. Certain other layers are deposited and optionally etched, intended to allow the insulation of certain layers or parts of certain layers, or on the contrary, to allow electrical connections between them, in particular through their edges, and at least to constitute contact points 171. The stack thus obtained is as shown in Figure 5 .

[0087] Through the contact points 171, the electrical current can thus advantageously be injected into or collected from the electroactive layers 14, 15 through their respective electrodes.

[0088] The electrodes (and if necessary, the contact points 171) are here equivalently considered as intermediate layers 17, the deposition of which is provided by the preferred embodiment of the method according to the second aspect of the application. As can be seen from the above, at least one of these intermediate layers 17 can be located between one or the other of the first and second electroactive layers 14, 15 and the underlying substrate 101, or at least on at least one of the first and second electroactive layers, or on either side of the first and second electroactive layers.

[0089] Once the stack of layers of micrometric thickness has been obtained as shown in Figure 4 and Figure 5 , the manufacturing method according to the preferred embodiment of the second aspect of the application comprises the deposition of a so-called passivation layer 103 formed on the basis of a second material. The layer 103 is called passivation, as it is formed more particularly on the basis of a so-called passivation material.

[0090] The second material on the basis of which the passivation layer 103 is formed can have the same properties as the first material on the basis of which the substrate 101 is formed. Thus, according to the preferred embodiment of the application, the passivation layer thus deposited is silicon-based, preferably polycrystalline.

[0091] More particularly, the step of depositing the passivation layer 103 is performed at least under (or in line with) at least a portion of the first electro-active layer 14, so that at least a portion of the second electro-active layer 15 is uncovered.

[0092] As shown in Fig. 1 1, the method according to the preferred embodiment of the second aspect of the application more particularly comprises the following sub-steps: Figure 6 Figure 7 As shown in Fig. 1 1, the method according to the preferred embodiment of the second aspect of the application more particularly comprises the following sub-steps:

[0093] a. depositing a preferably conformal layer of silicon (preferably polycrystalline) 1030 on the stack of layers provided in the first step of the method; and

[0094] b. etching the layer 1030 at least directly under (or flush with) at least a portion of the second electro-active layer 15. Preferably, this etching sub-step further comprises etching the conformal layer directly under (or flush with) the contact point 171. Preferably, this etching sub-step further comprises etching the conformal layer at a portion of the substrate 101 lying between the first and second electro-active layers 14, 15, flush with the underlying substrate 101. Etching the substrate can thus comprise etching through the previously generated silicon oxide layer on the surface of the silicon layer lying on the etching stop layer 102. This etching sub-step aims at forming the first elastically deformable element 1 1 at least at a portion of the first electro-active layer 14, but preferably also aims at structuring the central region of the substrate, central to the first and second electro-active layers 14, 15, so as to form the mechanical hinge 13 by structuring the substrate 101. This structuring can in particular be achieved by at least one removal of material 131. This removal of material 131 is formed in a manner shown in Fig. 1 1, and can comprise for example a hole or a trench (preferably a blind hole) extending from the front face of the mechanical microsystem 1 to the embedded etching stop layer 102. Figure 7

[0095] The mechanical hinge 13 thus formed has a controlled elasticity. In particular, it can be structured to have an elasticity greater than that of the first deformable element 1 1.

[0096] It is noted that the deposition of the passivation layer 103 is preferably configured so that the thickness of this layer is substantially equal to the thickness of the silicon layer previously deposited on the silicon oxide layer 102 and the opening 3. In other words, the deposition of the passivation layer 103 is preferably structured so that this layer has a thickness substantially equal to the depth of embedding of the etching stop layer 102 into the substrate 101 from its front face 101 1.

[0097] ​​Then, the manufacturing method comprises a step of etching at least partially the substrate 101 from its back face 1012. More specifically, during this step, at least one central portion 13 of the substrate 100 is etched. This etching step is configured to remove the central portion 1013 of the substrate 100 over the entire thickness located just below (or flush with) the etching stop layer 102. It is further configured to continue the removal of the central portion 1013 of the substrate 101 over the entire thickness to the right of the opening 3 of the etching stop layer 102. More specifically, the continuation of the etching to the right of the opening 3 is advantageously stopped by a silicon oxide layer created on the surface of the passivation layer 103.

[0098] Thus, a mechanical microsystem is obtained Figure 1 More specifically, as illustrated in Figure 1 The step of etching the substrate 100 through its back face 1012 allows forming a second elastically deformable element 12 arranged with the second electroactive layer 15, as illustrated in

[0099] It has to be noted that, alternatively or complementarily to the configuration of the mechanical hinge 13 as previously described, the etching of the back face 1012 of the substrate 101 can be configured to facilitate the configuration of the mechanical hinge 13.

[0100] As illustrated in Figure 1 The mechanical hinge 13 formed in the manner as previously described allows coupling the deformable elements 11, 12 together, as illustrated in

[0101] Preferably, only the central portion of the substrate 101 is etched from its back face 1012. Thus, as illustrated in Figure 1 The inner periphery of the substrate 101 is not etched and is conserved to constitute a rigid frame 16 to which the deformable elements 11, 12 are firmly connected. More specifically, the deformable elements 11, 12 are connected to the frame 16 through their proximal ends 113, 123, while the mechanical hinge 13 connects the deformable elements 11, 12 together through their distal ends 114, 124. In this preferred embodiment, it will thus be understood that advantageously the mechanical hinge 13 is flexible so as to allow each deformable element 11, 12 to move out of the rest plane, wherein each deformable element 11, 12 falls under the implementation of the manufacturing method according to the second aspect of the application as described below. Indeed, the proximal ends 113, 123 of the deformable elements 11, 12 coupled to the rigid frame 16 are not subjected to significant deformations (relative to the deformations undergone by each distal end 114, 124 of the deformable elements 11, 12) as long as they are connected to the mechanical hinge 13 which is relatively more flexible than the rigid frame 16, even more flexible than the deformable elements 11, 12 themselves.

[0102] Reference is made to Figure 8Thanks to the arrangement described above with respect to the deformable elements 11, 12 of the electrically active layers 14, 15, each deformable element 11 and 12 has a counter movement, which, outside its resting plane, is caused by the construction to rotate the mechanical hinge 13 around a rotation center substantially falling in the resting plane. The mechanical hinge 13 thus constitutes an area that can be subjected to rotations around axes falling in the resting plane, which rotations can vary around a balance position substantially maintained in the resting plane. Even so, the arrangement allows to obtain a half-rotation of the pulling force, with respect to the prior art, with respect to the action of the rotation ability of the mechanical hinge 13 that swings with respect to the balance position lying in the resting plane.

[0103] The different steps and sub-steps of deposition and etching described above are advantageously implemented by standard microelectronic techniques, such as physical or chemical vapor deposition, reactive ion etching or chemical etching. These techniques can optionally require the implementation of etching masks and / or include passivation deposition steps.

[0104] From the results of the manufacturing method according to its preferred embodiment described above, the deformable elements 11, 12 constitute beams made of the same passivation material, i.e. silicon, preferably polysilicon, having substantially the same thickness, even the same geometry.

[0105] In this way, after the application of the same electric current to each electrically active layer 14, 15 arranged with the deformable elements 11, 12, it is expected that each of the pair of deformable elements 11, 12 has the same amplitude of deformation, or, after the same amplitude of deformation of the deformable elements 11, 12, it is expected or measured that the same electric current circulates in each electrically active layer 14, 15.

[0106] Moreover, the mechanical hinge 13 is at least partially composed of the same material as the deformable elements 11, 12, the mechanical hinge 13 being in fact obtained by construction of the silicon-based substrate 101.

[0107] Reference Figure 1 The mechanical microsystem 1 according to the first aspect of the present application thus mainly comprises:

[0108] a. a pair of elastically deformable elements 11, 12;

[0109] b. a mechanical hinge 13 connecting the deformable elements 11, 12 together; and

[0110] c. at least two electrically active layers 14, 15,

[0111] The mechanical microsystem 1 is configured so that the deformation of the deformable elements 11, 12 moves it at least partially out of the rest plane from the rest position in which the deformable elements 11, 12 substantially fall within the rest plane as described above, inducing a circulation of electric current in the electrically active layers 14, 15, and / or vice versa.

[0112] It will be noted that by configuration, each deformable element 11, 12 has a front face 111, 121 and a back face 112, 122 opposite each other and substantially parallel to the rest plane.

[0113] The mechanical microsystem 1 differs from the mechanical microsystems known from the prior art at least in that the first electrically active layer 14 is arranged with the first deformable element 11 on the back face 112 of this first deformable element 11 and the second electrically active layer 15 is arranged with the second deformable element 12 on the front face 121 of this second deformable element 12.

[0114] Thus, according to a first aspect of the application, the application proposes a mechanical microsystem 1 capable of generating movements of each pair of deformable elements 11, 12 out of the rest plane which are antagonistic to achieve a bimetallic effect, as Figure 8 illustrated. Indeed, each deformable element in the same pair is capable of:

[0115] a. displacing in the opposite direction to the other of the pair of deformable elements to induce a circulation of electric current in the electrically active layer it supports, the mechanical microsystem acting as a sensor,

[0116] b. or powered by the electric current to displace in the opposite direction to the displacement of the other deformable element of the pair of deformable elements out of the rest plane, inducing its displacement out of the rest plane, the mechanical microsystem thus acting as an actuator.

[0117] Due to these antagonistic movements of each pair of deformable elements 11, 12, with respect to a mechanical microsystem not having antagonistic movements, for the same electric current circulating in the electrically active layers, it allows to generate a double angle between the same pair of deformable elements along an axis in the rest plane. As to this advantage, due to the antagonistic movements of the deformable elements, it allows to obtain a displacement of the same pair of deformable elements 11, 12 substantially equal to the amplitude provided by a mechanical microsystem having non-antagonistic movements, however with the electric current halved, which has the advantage of saving the energy delivered.

[0118] Moreover, the neutral fiber of the mechanical microsystem 1 according to the first aspect of the invention advantageously passes between each deformable element 11, 12 and the electroactive layer 14, 15 arranged with this deformable element. This location of the neutral fiber is a direct result of the manufacturing method 1, in particular when this method does not comprise any deposition of intermediate layers 17. When this method comprises a deposition of such intermediate layers 17, the configuration of these intermediate layers does not significantly influence the location of the neutral fiber, so that the neutral fiber continues to pass between each deformable element 11, 12 and the electroactive layer 14, 15 allowing its deformation, and thus achieves the desired bimetallic effect.

[0119] These characteristics and advantages of the mechanical microsystem 1 according to the first aspect of the invention are particularly useful when it is desired to produce MOEMS (Micro-Opto-Electro-Mechanical System) mirrors, in particular for routing optical telecommunication or scanners of LIDAR devices.

[0120] In addition to its application to MOEMS mirrors, the invention also applies to inkjet printing, for capturing and measuring pressure, etc.

[0121] Figure 1 It is also shown that the deformable elements 11, 12 are located opposite each other with respect to the mechanical hinge 13. The mechanical hinge 13 can in addition be used to join together another pair of deformable elements (not shown). This other pair of deformable elements can for example be identical to this pair of deformable elements 11, 12, however rotated by 90° with respect to this pair of deformable elements 11, 12 around the mechanical hinge 13. In other words, by considering the basic element located at the center of the mechanical hinge 13 and perpendicular to the plane of the mechanical hinge 13, the other pair of deformable elements is identical to this pair of deformable elements 11, 12, however rotated by 90° around this basic element. Figure 1 The cross-sectional plane of the cross-sectional plane shown, it is possible to obtain the same mechanical microsystem 1 as in Figure 1

[0122] It should also be noted that if the beams 11, 12 appear as streamlined elements in Figure 1 These elements can take any essentially elongated geometry. It can for example be curved (even folded) on a resting plane. More particularly, each beam can be of any essentially elongated shape, and in particular the shape of the beam shown and described by J. Tsaur et al. mentioned in the background art herein is taken as a reference.

[0123] ​The mechanical microsystem 1 according to the preferred embodiment of the first aspect of the present application comprises more specifically PTZ-based electroactive layers. With these electroactive layers 14, 15, the mechanical microsystem 1 is particularly advantageous since electroactive layers of this type contract only under the effect of an electric field and thus cannot allow the deformable elements 11, 12, which they support in multiple directions, to deform. Thus, here only the specific arrangement of each pair of electroactive layers with each pair of deformable elements allows the mechanical microsystem 1 to perform counter-movements on its deformable elements. Furthermore, PTZ advantageously has a high piezoelectric conversion rate.

[0124] The present application is not limited to the embodiments described above and can extend to all embodiments covered by the claims.

[0125] For example, each deformable element, each pair of deformable elements, or even a group of deformable elements can comprise or consist of a flexible membrane or be arranged with a flexible membrane.

Claims

1. A mechanical microsystem (1) comprising: a pair of elastically deformable elements (11, 12), b a mechanical hinge (13) connecting the deformable elements (11, 12) together, and c at least two electroactive layers (14, 15), said mechanical microsystem (1) being configured such that a deformation of at least one of the deformable elements (11, 12) moves it at least partially out of a rest plane from a rest position, thereby inducing a first electric current in at least one of the at least two electroactive layers (14, 15), and / or a second electric current in at least one of the at least two electroactive layers (14, 15) induces a deformation of at least another one of the deformable elements (11, 12) such that it moves at least partially out of the rest plane from the rest position, wherein in the rest position the deformable elements (11, 12) lie in one and the same rest plane, each deformable element (11, 12) has a front face (111, 121) and a back face (112, 122) opposite to each other and parallel to the rest plane, said mechanical microsystem (1) being characterized in that a first electroactive layer (14) of the at least two electroactive layers (14, 15) is arranged together with a first deformable element (11) of the pair of deformable elements on the back face (112) of the first deformable element (11), and a second electroactive layer (15) of the at least two electroactive layers (14, 15) different from the first electroactive layer (14) is arranged together with a second deformable element (12) different from the first deformable element (11) on the front face (121) of the second deformable element (12).

2. The mechanical microsystem (1) according to claim 1, further comprising a rigid frame (16), the deformable elements (11, 12) being fixedly joined to the rigid frame (16) through their proximal ends (113, 123) with respect to the rigid frame (16), the mechanical hinge (13) connecting the pair of deformable elements (11, 12) together through their distal ends (114, 124) with respect to the rigid frame (16), and wherein the mechanical hinge (13) is flexible, allowing the pair of deformable elements (11, 12) to move out of the rest plane.

3. The mechanical microsystem (1) according to claim 1, wherein at least one of the at least two electroactive layers (14, 15) is based on an electroactive material selected from the group consisting of piezoelectric materials, ferromagnetic materials and PTZ-based electroactive materials.

4. The mechanical microsystem (1) according to claim 1, wherein the deformable elements (11, 12) and the mechanical hinge (13) are based on the same material.

5. The mechanical microsystem (1) according to claim 4, wherein the same material is a silicon-based material.

6. The mechanical microsystem (1) according to claim 1, further comprising at least one intermediate layer (17) located between the first electroactive layer (14) and the first deformable element (11) and / or on either side of the first electroactive layer (14) and the first deformable element (11) and / or between the second electroactive layer (15) and the second deformable element (12) and / or on either side of the second electroactive layer (15) and the second deformable element (12).

7. The mechanical microsystem (1) according to claim 6, wherein the at least one intermediate layer (17) is configured to realize an electrical contact point to apply and / or measure an electrical current in at least one of the first electroactive layer (14) and the second electroactive layer (15) arranged together with the at least one intermediate layer (17).

8. The mechanical microsystem (1) according to claim 6, wherein the at least one intermediate layer (17) is arranged such that a neutral fiber (2) of the mechanical microsystem (1) is located between each electroactive layer (14, 15) and the deformable element (11, 12) arranged together with this electroactive layer (14, 15).

9. The mechanical microsystem (1) according to claim 7, wherein the at least one intermediate layer (17) is arranged such that a neutral fiber (2) of the mechanical microsystem (1) is located between each electroactive layer (14, 15) and the deformable element (11, 12) arranged together with this electroactive layer (14, 15).

10. The mechanical microsystem (1) according to any one of claims 1-9, further comprising at least one pair of a second pair of deformable elements which are connected together by the mechanical hinge connecting the first pair of deformable elements (11, 12) together or by a mechanical hinge which is different from the mechanical hinge connecting the first pair of deformable elements (11, 12) together.

11. A method for manufacturing a mechanical microsystem (1), comprising: a providing a substrate (101) based on a first material, on a front side (1011) of which a first electroactive layer (14) and a second electroactive layer (15) are formed in a spaced-apart manner from each other, the substrate (101) further comprising an embedded etch stop layer (102) having an opening (3) at least directly below or flush with a portion of the first electroactive layer (14), b depositing a passivation layer (103) based on a second material at least directly below or flush with a portion of the first electroactive layer (14) such that at least a portion of the second electroactive layer (15) is not covered by the passivation layer (103), c etching at least one central portion (1013) of the substrate (101) through the back side (1012) of the substrate (101) until the at least one central portion (1013) of the substrate (101) is removed over the entire thickness of the substrate (101) at a location directly below or flush with the etch stop layer (102) and until the at least one central portion (1013) of the substrate (101) is removed over the entire thickness to the right of the opening (3) of the etch stop layer (102); such that the passivation layer (103) forms a resilient first deformable element (11) arranged together with the first electroactive layer (14), such that the etched substrate (101) forms a resilient second deformable element (12) arranged together with the second electroactive layer (15), and such that at least one of the etched substrate (101) and the passivation layer (103) forms a mechanical hinge (13) connecting the first deformable element (11) and the second deformable element (12) together.

12. The method according to claim 11, wherein the forming of the first electroactive layer (14) and the second electroactive layer (15) comprises the steps of: a depositing a film made of an electroactive material in a single pass on the front side (1011) of the substrate (101), followed by b etching the deposited film, if necessary with an etch mask, to obtain the first electroactive layer (14) and the second electroactive layer (15) and to separate them from each other.

13. The method according to claim 11, wherein only the central portion (1013) of the substrate (101) is etched such that the remaining periphery of the substrate forms a rigid frame (16) to which the deformable elements (11, 12) are fixedly joined through their proximal ends (113, 123) relative to the rigid frame (16), the mechanical hinge (13) connecting the deformable elements (11, 12) together through their distal ends (114, 124) relative to the rigid frame (16), wherein the mechanical hinge (13) is flexible to allow each deformable element (11, 12) to move out of a rest plane.

14. The method according to claim 13, further comprising the step of structuring the mechanical hinge (13) by removing material (131) between the deformable elements (11, 12), regions of the substrate (101) and / or the passivation layer (103) to structure the mechanical hinge (13).

15. The method according to claim 11, further comprising depositing at least one intermediate layer (17), said at least one intermediate layer (17) being located between and / or on either side of said first electroactive layer (14) and said first deformable element (11) and / or between and / or on either side of said second electroactive layer (15) and said second deformable element (12).

16. The method of claim 15, wherein, The deposition of said at least one intermediate layer (17) is configured to enable an electrical contact point to apply and / or measure an electrical current in an electroactive layer (14, 15) arranged with said at least one intermediate layer (17).

17. The method according to any one of claims 11-16, wherein the deposition of said passivation layer (103) is configured such that the thickness of said passivation layer (103) is equal to the depth of embedding of said etch stop layer (102) into said substrate (101) from the front side (1011) of said substrate (101).

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