NANOMETRIC ELECTROMECHANICAL ACTUATOR AND ITS MANUFACTURING METHOD

Description

DOMAINE TECHNIQUE

[0001] The present invention relates to the field of nanometric electromechanical systems, otherwise known in English as NEMS for Nano Electro-Mechanical Systems. It finds a particularly advantageous application in the field of electromechanical actuators activated by an electrostatic force. ÉTAT DE LA TECHNIQUE

[0002] There are many nanoscale devices designed to replace traditional transistors in certain applications. Indeed, NEMS offer many advantages for certain technical applications such as telecommunications, for example.

[0003] There are almost as many processes as there are types and morphologies of NEMS. Indeed, it is truly high-precision work that is necessary to implement these devices.

[0004] Also, we know for example the document "Silicon on nothing MEMS electromechanical resonator, Durand et al., Microsyst Technol 2008, 14:1027-1033" which describes an electromechanical actuator comprising an epitaxial silicon membrane suspended at several of its ends above a silicon substrate. The distance between these two elements is then 100 nm and is obtained by the removal of an intercalary layer located between these two elements and having served for the growth of the epitaxial silicon layer.

[0005] The process used and the resulting device have many drawbacks. On the one hand, the process does not allow the entire interlayer located under the silicon layer to be efficiently removed, and on the other hand, the size of this device is large given that the membrane is held in suspension at several points. Finally, the membrane is made of epitaxial silicon, which is therefore not a monocrystalline layer, which then reduces its electromechanical performance.

[0006] Also known from the state of the art is document WO 02 / 10063 A2 relating to a method for manufacturing a microelectromechanical switch or a tunnel sensor with a cantilever beam and document EP 2 138 452 A1 relating to a flexible method for producing single-crystal silicon MEMS / NEMS whose small thicknesses can be controlled.

[0007] An object of the present invention is therefore to propose a method and a device responding at least in part to these problems and providing an improvement in the design of nanometric electromechanical actuators.

[0008] Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated. RÉSUMÉ

[0009] To achieve this objective, according to one embodiment, a method is provided for manufacturing an electromechanical actuator, preferably nanometric, comprising a fixed actuation electrode, a fixed contact electrode and a mobile electrode, the actuator further comprising a stack of layers, the mobile electrode comprising an anchoring part secured to the stack of layers and a mobile part configured to have a rest position and a contact position, the rest position corresponding to an absence of contact between the mobile part of the mobile electrode and the fixed contact electrode, the contact position corresponding to a contact between the mobile part of the mobile electrode and the fixed contact electrode when a non-zero bias is applied between the mobile electrode and the fixed actuation electrode, said method comprising the following steps: a) Providing a primary stack of layers comprising: i. A first substrate; ii. A monocrystalline layer disposed on an upper surface of the first substrate; iii. An interlayer disposed on an upper surface of the monocrystalline layer; iv. An etch layer disposed on an upper surface of the interlayer; b) Providing a secondary stack of layers comprising: i. A second substrate; ii. A transfer layer disposed on an upper surface of the second substrate; c) Forming by etching in the etch layer at least three pads, selectively to the interlayer; d) Encapsulating the three pads by a first encapsulation layer;e) Assembling the primary stack of layers with the secondary stack of layers by bonding at least a portion of the exposed surface of the first encapsulation layer with at least a portion of the exposed surface of the transfer layer so as to form a bonding interface; f) Removing the first substrate; g) Forming by etching the anchoring portion and the mobile portion of the mobile electrode in the monocrystalline layer; h) Removing a sacrificial portion of the interlayer configured to release the mobile portion of the mobile electrode and so as to preserve a portion of the interlayer between the anchoring portion of the mobile electrode and at least a portion of one of the three pads; ;

[0010] This makes it possible to produce an electromechanical actuator whose moving element is monocrystalline. This improves the electromechanical response of the actuator.

[0011] The monocrystallinity of the moving electrode allows better control of the polarization voltages necessary for its movement.

[0012] Bonding allows the use of various substrates and thus various types of monocrystalline materials if desired.

[0013] This also makes it possible to produce an electromechanical actuator with a reduced gap compared to the prior art.

[0014] Another aspect relates to an actuator comprising at least one fixed actuation electrode, one fixed contact electrode and one mobile electrode, the actuator comprising at least one stack of layers, the mobile electrode comprising at least one anchoring portion secured to the stack of layers and a mobile portion configured to have a rest position and a contact position, the rest position corresponding to an absence of contact between the mobile portion of the mobile electrode and the fixed contact electrode, the contact position corresponding to a contact between the mobile portion of the mobile electrode and the fixed contact electrode when a non-zero bias is applied between the mobile electrode and the fixed actuation electrode, said actuator being characterized in that the mobile electrode is formed from a monocrystalline material and in that the anchoring portion is secured to the stack of layers through an interlayer. BRÈVE DESCRIPTION DES FIGURES

[0015] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which: There figure 1 represents a nanoscale electromechanical actuator according to an embodiment of the present invention. The figure 2 represents part of the steps of a method of manufacturing a nanoscale electromechanical actuator according to an embodiment of the present invention. The figure 3 represents a primary stack of layers according to an embodiment of the present invention. The figure 4 represents a secondary stack of layers according to an embodiment of the present invention. figure 5 represents the production of plots according to an embodiment of the present invention. The figure 6 represents three plots produced according to an embodiment of the present invention. The figure 7 represents a step of encapsulating the three pads according to an embodiment of the present invention. The figure 8 represents a planarization step of the encapsulation layer of the figure 7 according to one embodiment of the present invention. The figure 9 represents a step of bonding the primary stack of layers with the secondary stack of layers according to an embodiment of the present invention. The figure 10 represents the assembly of the primary stack of layers with the secondary stack of layers according to an embodiment of the present invention. The figure 11 represents the removal of the first substrate from the primary stack of layers according to an embodiment of the present invention. The figure 12 represents a top view of the figure 11 with the arrangement of a second etching mask on the monocrystalline layer according to an embodiment of the present invention. The figure 13 represents a sectional view of the figure 12 and the step of arranging the second etching mask on the monocrystalline layer according to an embodiment of the present invention. figure 14 represents a step of conforming the second etching mask so as to define the contours of the mobile electrode being formed according to an embodiment of the present invention. The figure 15 represents a step of etching a portion of the monocrystalline layer and the interlayer according to an embodiment of the present invention. The figure 16 represents a step of removing the second etching mask according to an embodiment of the present invention. The figure 17 represents a step of encapsulating the mobile electrode according to an embodiment of the present invention. The figure 18 represents a step of planarizing the encapsulation layer according to an embodiment of the present invention. The figure 19 represents a step of forming openings in a third etching mask directly above the three pads according to an embodiment of the present invention. The figure 20 represents a step of forming openings in the second encapsulation layer according to an embodiment of the present invention. The figure 21 represents a step of depositing a plurality of electrically conductive layers according to an embodiment of the present invention. The figure 22 represents the deposition of a fourth etching mask according to an embodiment of the present invention. The figure 23 represents the formation of three electrical contacts according to an embodiment of the present invention. The figure 24 represents a step of removing at least a portion of the second encapsulation layer according to an embodiment of the present invention. The figure 25 represents a step of removing the part of the interlayer located under the mobile part of the mobile electrode so as to form a gap between this mobile part and the two other electrodes according to an embodiment of the present invention. The figure 26 represents a top view of a nanoscale electromechanical actuator according to an embodiment of the present invention. The figure 27 depicts a top view of a dual nanoscale electromechanical actuator according to another embodiment of the present invention.

[0016] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. In particular, the dimensions are not representative of reality. DESCRIPTION DÉTAILLÉE

[0017] Before beginning a detailed review of embodiments of the invention, optional characteristics which may possibly be used in combination or alternatively are set out below: According to one example, the monocrystalline layer is based on and / or comprises at least one material taken from: a semiconductor, an electrical conductor.

[0018] In one example, the etching layer is a monocrystalline layer.

[0019] In another example, the etching layer is an epitaxial layer.

[0020] In another example, the etching layer is a polycrystalline layer.

[0021] In another example, the etching layer is an amorphous layer.

[0022] In one example, the crystal structure of the monocrystalline layer is different from the crystal structure of the etching layer.

[0023] In one example, the monocrystalline layer and the etching layer are made of the same material.

[0024] According to one example, the etching layer is obtained by epitaxial growth of a material identical to the material composing the monocrystalline layer and from the interlayer.

[0025] According to one example, the interlayer has a thickness dimension less than or equal to the thickness dimension of the monocrystalline layer, the thickness dimensions being taken along an axis orthogonal to the main extension dimension of the layers considered.

[0026] In one example, the monocrystalline layer is based on monocrystalline silicon, the interlayer is based on silicon and germanium, and the etching layer is based on silicon.

[0027] In one example, collage is molecular collage.

[0028] According to one example, the method comprises, before the assembly step, a step of planarizing the exposed surface of the first encapsulation layer so as to partially expose at least one surface of at least one of the three pads, and the bonding interface is formed in part at least of a portion of the surface of one of the three pads, of at least a portion of the exposed surface of the first encapsulation layer and of at least a portion of the exposed surface of the transfer layer.

[0029] According to one example, the step of removing a portion of the interlayer comprises at least one wet or anhydrous etching configured to remove a sacrificial portion of the interlayer supporting the movable portion of the movable electrode.

[0030] According to one example, the method comprises a step of forming at least one electrical contact for each pad.

[0031] According to one example, the mobile part of the mobile electrode is suspended by the anchoring part of the mobile electrode above at least a part of the fixed actuation electrode in the rest position, the distance separating the mobile part and the part of the fixed actuation electrode is less than 20 nm, preferably 15 nm and advantageously equal to 12 nm in the rest position.

[0032] According to one example, the actuator comprises at least one bonding interface resulting from bonding a primary stack of layers with a secondary stack of layers.

[0033] It is specified that in the context of the present invention, the term "on", "overcomes", "covers" or "underlying" or their equivalents do not mean "in contact with". Thus, for example, the deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but it does mean that the first layer at least partially covers the second layer by being either directly in contact with it or by being separated from it by at least one other layer or at least one other element.

[0034] In the present patent application, the thickness is taken in a direction perpendicular to the main faces of the substrate on which the different layers rest. In the figures, the thickness is taken vertically.

[0035] The present invention relates to a nanometric electromechanical actuator and its manufacturing method. This device advantageously has a gap of less than 50nm, which allows it to be more responsive. Similarly, this device has a monocrystalline mobile electrode, which again allows for increased responsiveness, reliability and durability of the device. These advantages are made possible in part by the configuration of the device and its manufacturing method.

[0036] There figure 1 represents, according to an embodiment of the present invention, a nanometric electromechanical actuator 10. This actuator 10 comprises three electrical contacts 510, 520 and 530, each connected to a pad 131, 132 and 133. Each electrical contact / pad assembly forms an electrode 410, 420 and 430. This device 10 then comprises a fixed contact electrode 430, a fixed actuation electrode 420 and a mobile electrode 410.

[0037] This mobile electrode 410 comprises an anchoring part 412 secured to a pad 131 and an electrical contact 510 through an interlayer 411. This mobile electrode 410 comprises a mobile part 413, preferably in the form of a beam suspended above the two other pads 132 and 133. This mobile electrode 410 is configured to advantageously have two positions, a so-called rest position and a so-called contact position. The rest position corresponds to an absence of contact between the mobile part 413 of the mobile electrode 410 and the fixed contact electrode 430. The contact position corresponds to a contact between the mobile part 413 of the mobile electrode 410 and the fixed contact electrode 430 when a non-zero bias is applied between the mobile electrode 410 and the fixed actuation electrode 420.The electrostatic force then exerted on the movable part 413 of the movable electrode 410 tilts the latter to the point that it comes into electrical contact with the fixed contact electrode 430.

[0038] It will be noted in particular that, according to an embodiment illustrated in figure 1 , the fixed actuation electrode 420 is arranged between the fixed contact electrode 430 and the anchoring part of the mobile electrode 410. In this configuration, and advantageously, it is the free end of the beam of the mobile part 413 of the mobile electrode 410 which is configured to come at least partly into electrical contact with the fixed contact electrode 430 in the contact position.

[0039] These three electrodes 410, 420 and 430 are supported by a stack of layers called secondary 200 comprising a substrate, called second substrate 211 hereinafter, and a transfer layer 212.

[0040] According to a preferred embodiment, this transfer layer 212 comprises a bonding interface 142 located between the three pads 131, 132 and 133 and the second substrate 212 as will be described below.

[0041] In this figure as well as the figure 25 , the gap 415 will be noted, that is to say the distance located between the mobile part 413 of the mobile electrode 410 and the pad 133 of the contact electrode 430 when the mobile electrode 410 is in the rest position. Preferably, the upper surface of the pads 132 and 133 are coplanar, thus defining a constant gap 415 between the mobile part 413 of the mobile electrode 410 and both the upper surface of the pad 132 and the upper surface of the pad 133 of the other two electrodes 420 and 430. This gap 415 is preferably equal to the thickness dimension of the interlayer 411. This interlayer 411 is preferably based on silicon-germanium (SiGe). This gap 415 is advantageously less than 20nm, preferably 15nm and preferably equal to 12nm.

[0042] There figure 2 illustrates a schematic representation of an embodiment of the method 1000 according to the present invention.

[0043] According to one embodiment, the manufacturing method 1000 comprises at least the following steps: a) Providing 1010 a primary stack of layers 100 comprising: i. A first substrate 110; ii. A monocrystalline layer 120 disposed on an upper surface of the first substrate 110; iii. An interlayer 411 disposed on an upper surface of the monocrystalline layer 120; iv. An etch layer 130 disposed on an upper surface of the interlayer 411; b) Providing 1020 a secondary stack of layers 200 comprising: i. A second substrate 211; ii. A transfer layer 212 disposed on an upper surface of the second substrate 211; c) Forming 1030, preferably by etching, at least three pads 131, 132 and 133 in the first etch layer 130, selectively to the interlayer 411; d) Encapsulation 1040 of the three pads 131, 132 and 133 by a first encapsulation layer 140; e) Preferably, planarization 1050 of the exposed surface of the first encapsulation layer 140;f) Assembling 1060 the primary stack of layers 100 with the secondary stack of layers 200 by bonding at least a portion of the exposed surface 141 of the first encapsulation layer 140 with the exposed surface 213 of the transfer layer 212 so as to form a bonding interface 142; g) Removing 1070 the first substrate 100 so as to expose at least a portion of the monocrystalline layer 120; h) Forming 1080 by etching the anchoring portion 412 and the mobile portion 413 of the mobile electrode 410 in the monocrystalline layer 120; i) Preferably, removal 1090 of a portion of the interlayer 411 so as to retain the interlayer 411 at least under the mobile electrode 410, said interlayer 411 thus forming a support layer for the mobile electrode 410 and in particular for the anchoring part 412 and the mobile part 413 of the mobile electrode 410;j) Removal 1100 of a sacrificial portion 414 of the interlayer 411 configured to release the mobile portion 413 of the mobile electrode 410 and so as to preserve one of the interlayer 411 between the anchoring portion 412 and at least a portion of one of the three pads 131; k) Preferably, before or after the formation 1080 of the anchoring portion 412 and the mobile portion 413 of the mobile electrode 410, formation 1110 of electrical contacts 510, 520 and 530 above at least a portion of each of the three pads 131, 132 and 133. ;

[0044] This method 1000 cleverly makes it possible to obtain the device 10 previously presented comprising a monocrystalline mobile electrode 410 spaced in height from the fixed contact electrodes 430 and actuation electrodes 420 by a very small distance relative to the prior art, a distance commonly called gap 415. As described below, it is at least partly by the bonding step 1060 and the use of wet or anhydrous etching 1100 that this device 10 can thus be manufactured.

[0045] There figure 3 represents the primary stack of layers 100. The first substrate 110 preferably comprises at least one support layer 111 and one interface layer 112.

[0046] The support layer 111 is preferably made of semiconductor material and in particular silicon-based.

[0047] The interface layer 112 is advantageously based on a dielectric material, for example a nitride or a semiconductor oxide, and preferably silicon oxide.

[0048] The monocrystalline layer 120 is preferably based on monocrystalline silicon. The monocrystalline layer 120 may have a thickness dimension of less than 20nm, preferably 15nm and advantageously equal to 12nm.

[0049] Preferably, the term "monocrystalline" means a material or layer having a homogeneous and continuous crystalline structure, preferably without grain boundaries. It will be noted in particular that an epitaxial layer is not considered to be a monocrystalline layer in the present description.

[0050] The interlayer 411 is preferably based on SiGe. The interlayer 411 may have a thickness dimension of less than 20nm, preferably 15nm and advantageously equal to 12nm.

[0051] According to a preferred embodiment, the etching layer 130 is preferably based on an epitaxial material. This makes it possible to reduce the introduction of mechanical stresses in the primary layer stack 100. According to this embodiment, the etching layer 130 is an epitaxial layer, and not a monocrystalline one.

[0052] According to another embodiment, the etching layer 130 is monocrystalline.

[0053] Preferably, the etching layer 130 is based on silicon, advantageously epitaxially grown or monocrystalline. It will be noted that the embodiment in which the etching layer 130 is monocrystalline makes it possible to avoid the presence of mechanical stresses in the stack of primary layers 100.

[0054] The etching layer 130 may have a thickness dimension greater than 20nm, preferably 50nm and advantageously equal to 100nm.

[0055] According to one embodiment, the etching layer 130 is doped so as to make it electrically conductive or more conductive. This makes it possible to reduce the electrical resistivity of the etching layer 130, for example in the case where it is based on a semiconductor or even insulating material. This thus makes it possible to reduce the propagation delay of an electrical signal passing through the etching layer 130.

[0056] According to one embodiment, the etching layer 130 is based on the same material as the monocrystalline layer 120, and the crystallographic structure of the etching layer 130 is different from the crystallographic structure of the monocrystalline layer 120. By different crystallographic structure is meant, for example, the fact that the crystallographic orientation and / or the lattice parameters and / or the impurity level are different between two layers of the same material.

[0057] There figure 4 represents the secondary stack of layers 200.

[0058] The second substrate 211 is preferably silicon-based, advantageously monocrystalline.

[0059] The transfer layer 212 is preferably based on a dielectric material. The transfer layer 212 is advantageously based on silicon oxide.

[0060] The transfer layer 212 has a thickness dimension greater than 50nm, preferably 150nm and advantageously equal to 400nm.

[0061] THE figures 5 And 6represent the step 1030 of forming the three pads 131, 132 and 133 in the etching layer 130. It will be noted that this step comprises the arrangement of a first etching mask 310 on at least a portion of the exposed surface of the etching layer 130 so as to define the three pads 131, 132 and 133 to be formed. Preferably, the term etching mask means any layer of resin or any hard mask used to protect one or more portions of a layer or layers during etching.

[0062] This step 1030 comprises an etching of the etching layer 130. Preferably, the etching continues until at least part of the interlayer 411 located between each pad 131, 132 and 133 thus formed is exposed.

[0063] According to one embodiment, this etching may comprise plasma etching based on Cl 2 / HBr chemistry.

[0064] According to another embodiment, this etching may comprise an etching based on CF 4 / N 2 and O 2 .

[0065] It will be noted that the three pads 131, 132 and 133 have a substantially equal thickness dimension. It will also be noted that the first pad 131 has a width extension dimension greater than that of the second pad 132, and that the second pad 132 has a width extension dimension greater than that of the third pad 133.

[0066] Advantageously, the first pad 131 is configured to support the anchoring portion 412 of the mobile electrode 410. The second pad 132 is preferably configured to form at least in part the fixed actuation electrode 420. Preferably, the third pad 133 is configured to form at least in part the fixed contact electrode 430.

[0067] There figure 7 represents the encapsulation step 1040 by the first encapsulation layer of the three pads 131, 132 and 133 thus formed. The first encapsulation layer 140 is preferably based on a dielectric material, advantageously based on silicon oxide. It will be noted that the thickness dimension of the first encapsulation layer 140 is greater than the thickness dimension of each pad 131, 132 and 133.

[0068] There figure 8 represents a planarization step 1050 of the exposed surface 141 of the first encapsulation layer. The planarization 1050 can be carried out until at least a portion of the three pads 131, 132 and 133 is exposed according to one embodiment. This planarization step 1050 can use a chemical-mechanical planarization method.

[0069] THE figures 9 And 10illustrate the bonding 1060 of at least a portion of the planarized surface 141 of the first encapsulation layer 140 with the exposed surface 213 of the transfer layer 212 of the secondary stack of layers 200. This bonding is advantageously a molecular bonding. It will be noted that this bonding gives rise to a bonding interface 214. This bonding interface 214 can be either located between the previously exposed surface of a pad 131, 132 or 133 and the exposed surface 213 of the support layer 212 and / or between a portion of the planarized surface 141 of the first encapsulation layer 140 and the exposed surface 213 of the support layer 212.

[0070] There figure 11 illustrates the step 1070 of removing the first substrate 110. This step of removing 1070 may comprise a step of selectively etching the monocrystalline layer 120. This step makes it possible to expose the monocrystalline layer 120.

[0071] Now, the monocrystalline layer 120 is arranged above the interlayer 411, itself arranged at least in part above the three pads 131, 132 and 133, the whole being supported by the secondary stack of layers 200.

[0072] THE figures 12 à 15 illustrate the conformation of the monocrystalline layer 120 into the anchoring part 412 and into the mobile part 413 of the mobile electrode 410.

[0073] There figure 12 represents a top view of the arrangement on the monocrystalline layer 120 and the conformation of a second etching mask 320 so as to define the desired geometric shape for the mobile electrode 410.

[0074] There figure 13 illustrates a sectional view of this arrangement and conformation.

[0075] There figure 14 represents an optional step of refining the geometry of the second etching mask 320. This makes it possible to optimize the desired geometric shape for the mobile electrode 410.

[0076] There figure 15 illustrates the formation 1080 of the anchoring portion 412 and the mobile portion 413 of the mobile electrode 410. This formation step 1080 comprises the etching of at least a portion of the monocrystalline layer 120 and preferably of at least a portion of the interlayer 411, preferably selectively with the second etching mask 320. This etching preferably continues until at least a portion of the pads 131, 132 and 133 is exposed and advantageously of the first encapsulation layer 140 located between the pads 131, 132 and 133.

[0077] This etching step can be carried out by plasma etching in the presence of Cl 2 / HBr chemistry for example and can be continued until at least part of the first encapsulation layer 140 is exposed.

[0078] There figure 16 illustrates the removal of the second etching mask 320. It is then noted that the monocrystalline layer 120 is shaped according to the desired geometry for the first electrode 410. The monocrystalline layer 120 is supported by a portion of the interlayer 411. The monocrystalline layer 120 comprises the anchoring portion 412 securing it to the first pad 131 through a support portion of the interlayer 411 and a movable portion 413, preferably longitudinal, intended to be suspended above a portion of the second pad 132 and the third pad 133.

[0079] On the figure 16 , the part 413 intended to be suspended is for the moment supported by a sacrificial part 414 of the intermediate layer 411.

[0080] There figure 17 illustrates a step of encapsulating the monocrystalline layer 120 by a second encapsulation layer 160. This second encapsulation layer 160 is preferably based on a dielectric material and preferably silicon oxide.

[0081] There figure 18 illustrates an optional step of planarization of the exposed surface 161 of the second encapsulation layer 160. This planarization is advantageously carried out by a mechanical-chemical planarization technique.

[0082] There figure 19 represents the arrangement of a third etching mask 330 and the formation in this third etching mask 330 of openings 331, preferably arranged directly above the pads 131, 132 and 133.

[0083] There figure 20 then represents the etching of the second encapsulation layer 160 at each of the openings 331 formed directly above the pads 131, 132 and 133. This etching step makes it possible to define openings 162 in the second encapsulation layer 160 directly above each pad 131, 132 and 133 and so as to expose at least a portion of each pad 131, 132 and 133.

[0084] THE figures 21 à 23 illustrate the steps 1110 of forming electrical contacts 510, 520 and 530. Each pad 131, 132 and 133 thus comprises an electrical contact 510, 50 and 530 configured to allow polarization, by means of the actuation electrode 420, of the mobile electrode 410 and its placing in electrical contact with the fixed contact electrode 430.

[0085] There figure 21 represents the deposition of a metallization layer 500 on at least part of the surface of the device 10 during manufacture, the objective here being to fill the openings 161 previously made in the second encapsulation layer 160 with at least part of this metallization layer 500.

[0086] Preferably, this metallization layer 500 comprises a plurality of sub-layers 501, 502, 503 and 504. The first sub-layer 501 is for example based on titanium, the second sub-layer 502 is for example based on titanium nitride, the third sub-layer 503 is for example based on tungsten and the fourth sub-layer 504 is based on a mixture of aluminum and silicon.

[0087] There figure 22 represents the positioning of a fourth etching mask 340 on the metallization layer 500 directly above the pads 131, 132 and 133.

[0088] Then the figure 23 represents the step of etching the metallization layer 500 selectively to the second encapsulation layer 160 so as to define at least one electrical contact 510, 520 and 530 for each pad 131, 132 and 133.

[0089] There figure 24 then illustrates a step of removing at least part of the thickness of the second encapsulation layer 160. This etching step may comprise vapor phase etching, in HF chemistry for example. This etching is advantageously selective with respect to the pads 131, 132 and 133, to the mobile electrode 410 and to the interlayer 411.

[0090] This etching step makes it possible to expose a surface of the interlayer 411, a surface opposite the surface of the residual portion of the second encapsulation layer 160.

[0091] There figure 25 then illustrates the removal 1100 of the sacrificial part 414 of the interlayer 411, that is to say the etching of the part of the interlayer 411 securing the mobile part 413 of the mobile electrode 410 with the second pad 132 and with the third pad 133.

[0092] This etching is advantageously a wet or anhydrous etching. The objective of such etching is to be able to remove the sacrificial part 414 of the interlayer 411 without leaving any trace of said interlayer 411 under the mobile part 413 of the mobile electrode 410, while retaining a part of this interlayer 411 under the anchoring part 412 of the mobile electrode 410.

[0093] Indeed, the beam defining the mobile part 413 of the mobile electrode 410 is then arranged in suspension by removing the sacrificial part 414 of the interlayer 411. This then creates the gap 415 previously discussed.

[0094] According to one embodiment, this etching is a plasma etching based on CF4.

[0095] According to another embodiment, this etching is a vapor phase etching based on HCl.

[0096] It will be noted that only the sacrificial part 414 of the intermediate layer 411, that is to say the part located in contact with, and preferably under, the mobile part 413 of the mobile electrode 410 is removed, preferably in its entirety. A part of the intermediate layer 411 remains under the anchoring part 412 of the mobile electrode 410 connecting it mechanically and electrically to the first pad 131 and therefore to the electrical contact 510 of the first pad 131.

[0097] There figure 26 represents a top view of the actuator 10 of the figure 1 produced by the method 1000 previously described. Note the shape of the movable part 413 of the movable electrode 410 which extends longitudinally so as to be suspended above the two other electrodes 420 and 430.

[0098] This method 1000 thus makes it possible to obtain a nanometric electromechanical actuator 10 having an increased electromechanical response and an extremely reduced gap 415 relative to the prior art.

[0099] According to an embodiment illustrated in figure 27 , it is also possible, via this same method, to produce a plurality of actuators 10. On the figure 27 , it is a double actuator 20 comprising two mobile parts 413 secured to each other by the same anchoring part 412. In this figure, there are then two fixed contact electrodes 430 and two fixed actuation electrodes 420.

[0100] According to one embodiment, and in particular depending on the thickness of the mobile electrode 410 and the mechanical properties of the interlayer 411, the first mobile part 413 and the second mobile part 413 can be either independent of each other in their position, or be anti-correlated with each other, so that when one is in the contact position, the other is necessarily in the rest position for example.

[0101] The present invention thus allows a significant gain in reliability, reproducibility and longevity by producing a monocrystalline mobile electrode suspended at a very short distance above the fixed contact and actuation electrodes compared to the prior art.

[0102] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the claims. LISTE DES REFERENCES

[0103] 10Nanometric electromechanical actuator 20Dual nanometric electromechanical actuator 100Primary layer stack 110First substrate 111Support layer 112Surface layer 120Single crystal layer 130Etching layer 131First pad 132Second pad 133Third pad 140First encapsulation layer 141Planarized surface of the first encapsulation layer 160Second encapsulation layer 161Planarized surface of the second encapsulation layer 162Openings in the second encapsulation layer 200Secondary layer stack 211Second substrate 212Transfer layer 213Exposed surface of the transfer layer 214Bonding interface 310First etch mask 320Second etch mask 321Second refined etching mask 330Third etching mask 331Openings in the third etching mask 340Fourth etching mask 410Movable electrode 411Interlayer 412Anchoring part 413Movable part 414Sacrificial part of the layer415Gap interlayer 420Fixed actuation electrode 430Fixed contact electrode 500Metallization layer 501First metallization sublayer 502Second metallization sublayer 503Third metallization sublayer 504Fourth metallization sublayer 510First electrical contact 520Second electrical contact 530Third electrical contact 1000Manufacturing process 1010Providing a primary stack of layers 1020Providing a secondary stack of layers 1030Forming three pads in the first etch layer 1040Encapsulating the three pads with a first encapsulation layer 1050Planarizing the exposed surface of the first encapsulation layer 1060Assembling the primary stack of layers with the secondary stack of layers 1070Removal of the first substrate 1080Formation by etching of the mobile electrode in the monocrystalline layer 1090Removal of a portion of the interlayer 1100Removal of a partsacrificial interlayer 1110Formation of electrical contacts above at least part of each of the three pads

Claims

1. A method (1000) for manufacturing an electromechanical actuator (10, 20), preferably nanometric, comprising a fixed actuation electrode (420), a fixed contact electrode (430) and a movable electrode (410), the actuator further comprising a stack of layers (200), the movable electrode (410) comprising an anchor part (412) integral with the stack of layers (200) and a movable part (413) configured to have a rest position and a contact position, the rest position corresponding to a lack of contact between the movable part (413) of the movable electrode (410) and the fixed contact electrode (430), the contact position corresponding to a contact between the movable part (413) of the movable electrode (410) and the fixed contact electrode (430) when a non-zero polarisation is applied between the movable electrode (410) and the fixed actuation electrode (420), said method (1000) comprising the following steps: • Providing (1010) a primary stack of layers (100) comprising: i. A first substrate (110); ii. A single crystal layer (120) disposed on a top surface of the first substrate (110); iii. An interlayer (411) disposed on a top surface of the single crystal layer (120); iv. An etching layer (130) disposed on a top surface of the interlayer (411); • Providing (1020) a secondary stack of layers (200) comprising: i. A second substrate (211); ii. A transfer layer (212) disposed on a top surface of the second substrate (211); • Forming (1030) at least three pads (131, 132, 133), by etching in the etching layer (130), selectively to the interlayer (411); • Encapsulating (1040) the three pads (131, 132, 133) by a first encapsulation layer (140); • Assembling (1060) the primary stack of layers (100) with the secondary stack of layers (200) by bonding at least part of the exposed surface (141) of the first encapsulation layer (140) with at least part of the exposed surface (213) of the transfer layer (212) so as to form a bonding interface (214); • Removing (1070) the first substrate (110); • Forming (1080) the anchor part (412) and the movable part (413) of the movable electrode (410) by etching into the single crystal layer (120); • Removing (1100) a sacrificial part (414) of the interlayer configured to release the movable part (413) of the movable electrode (410) and so as to keep part of the interlayer (411) between the anchor part (412) of the movable electrode (410) and at least part of one of the three pads (131, 132, 133);2. The method (1000) according to the preceding claim, wherein the single crystal layer (120) is based on and / or comprises at least one material chosen from: a semiconductor, an electrical conductor.

3. The method (1000) according to any of the preceding claims, wherein the etching layer (130) is a single crystal layer.

4. The method (1000) according to the preceding claim, wherein the crystal structure of the single crystal layer (120) is different from the crystal structure of the etching layer (130).

5. The method (1000) according to any of the preceding claims, wherein the single crystal layer (120) and the etching layer (130) are based on the same material.

6. The method (1000) according to any of the preceding claims, wherein the etching layer (130) is obtained by epitaxially growing a material identical to the material making up the single crystal layer (120) and from the interlayer (411).

7. The method (1000) according to any of the preceding claims, wherein the interlayer (411) has a thickness dimension less than or equal to the thickness dimension of the single crystal layer (120), the thickness dimensions being taken along an axis orthogonal to the main dimension of extension of the layers considered.

8. The method (1000) according to any of the preceding claims, wherein the single crystal layer (120) is based on single crystal silicon, the interlayer (411) is based on silicon and germanium and the etching layer (130) is based on silicon.

9. The method (1000) according to any of the preceding claims, wherein bonding is molecular bonding.

10. The method (1000) according to any of the preceding claims, comprising, before the assembly step (1060), a step of planarising (1050) the exposed surface (141) of the first encapsulation layer (140) so as to at least partly expose a surface of at least one of the three pads (131, 132, 133) and wherein the bonding interface (214) is at least partly formed of the surface of one of the three pads (131, 132, 133), of at least part of the exposed surface (141) of the first encapsulation layer (140) and at least part of the exposed surface (213) of the transfer layer (212).

11. The method (1000) according to any of the preceding claims, wherein the step of removing (1100) part of the interlayer (411) comprises at least one wet or anhydrous etching configured to remove a sacrificial part (414) from the interlayer (411) supporting the movable part (413) of the movable electrode (410).

12. The method (1000) according to any of the preceding claims, comprising a step of forming (1110) at least one electrical contact (510, 520, 530) for each pad (131, 132, 133).

13. An actuator (10, 20) comprising at least a fixed actuation electrode (420), a fixed contact electrode (430) and a movable electrode (410), the actuator (10, 20) comprising at least a stack of layers (200), the movable electrode (410) comprising at least an anchor part (412) integral with the stack of layers (200) and a movable part (413) configured to have a rest position and a contact position, the rest position corresponding to a lack of contact between the movable part (413) of the movable electrode (410) and the fixed contact electrode (430), the contact position corresponding to a contact between the movable part (413) of the movable electrode (410) and the fixed contact electrode (430) when a non-zero polarisation is applied between the movable electrode (410) and the fixed actuation electrode (420), said actuator (10, 20) being such that the movable electrode (410) is formed of a single crystal material and in that the anchor part (412) is integral with the stack of layers (200) through an interlayer (411), the movable part (413) of the movable electrode (410) is suspended by the anchor part (412) of the movable electrode (410) above at least one part of the fixed actuation electrode (420) in the rest position, and the actuator being characterised in that the distance separating the movable part (413) and the part of the fixed actuation electrode (420) is less than 20nm in the rest position.

14. The actuator (10, 20) according to the preceding claim, comprising at least one bonding interface (214) derived from bonding a primary stack of layers (100) with a secondary stack of layers (200).

15. The actuator (10, 20) according to one of the two preceding claims, wherein the distance separating the movable part (413) and the part of the fixed actuation electrode (420) is less than 15nm, and advantageously equal to 12nm, in the rest position.