MICRO DEVICE WITH AT LEAST TWO MOVABLE ELEMENTS

Description

TECHNICAL FIELD AND PRIOR ART

[0001] The invention relates to the field of micro-devices, in particular that of micro-devices of the microelectromechanical systems (MEMS) and / or nanoelectromechanical systems (NEMS) and / or opto-electromechanical microsystems (MOEMS) and / or nanoopto-electromechanical systems (NOEMS) type, comprising mobile elements capable of moving under the effect of an external action (mechanical, electrical, magnetic) relative to a fixed part of the device. Subsequently, the term "micro-device" is used to designate in particular a device of the MEMS and / or NEMS and / or MOEMS and / or NOEMS type.

[0002] Micro-devices are generally made by implementing conventional techniques of collective etching of a wafer of semiconductor material (for example silicon). They are small and inexpensive to manufacture. The fields of application can be very varied, ranging from consumer products to very specific fields of application.

[0003] Some micro-devices each have several moving elements, such as some inertial sensors that require several moving masses to perform inertial measurements. One of the areas of application for these sensors is, for example, the inertial measurement of angular quantities such as angular position (gyroscopes) and rotational speed (gyrometers). The performance of such an inertial sensor depends directly on the balancing of the resonator, and more particularly on the balancing between the different moving masses of the sensor. This requires the presence of at least two moving masses mounted symmetrically with respect to each other in such a way that they can move in phase opposition with respect to each other, thus providing balancing of the sensor.

[0004] These moving masses can be produced side by side within the same layer of material, as described in documents US2014 / 0299947A1 and EP 2 887 013 A1. However, such an angular magnitude sensor comprising two moving masses arranged side by side and produced in the same layer of material has the disadvantage of generating a dynamic unbalance resulting from the displacement of the overall center of gravity of the moving masses at their vibration frequency. This causes reaction forces in the support and therefore a loss of vibration energy. In addition, the presence of the moving masses side by side implies, for the sensor, large dimensions and therefore a high production cost.

[0005] Alternatively, it is also known to produce concentric moving masses within the same layer of material. The main drawback of having at least two concentric moving masses within the same layer is that these two masses cannot have identical shapes. This configuration can cause problems with balancing these masses. In addition, the concentric production of these moving masses implies large dimensions for the sensor, and therefore a significant production cost. These large dimensions are also found even when a single moving mass is produced within a single layer of material.

[0006] Another configuration is to make the two moving masses of a sensor one above the other, each within a different layer of material. This configuration avoids the problems encountered with the configurations described above in which the moving masses are arranged side by side or concentrically. However, the realization of such sensors poses other problems.

[0007] Thus, document US 2011 / 0300658 A1 describes the production of such a sensor comprising two superimposed moving masses, from a double SOI substrate, i.e. comprising, above a support layer and a buried dielectric layer, two surface layers of silicon superimposed one above the other and spaced from each other by another dielectric layer. The disadvantage of such a production method is that the two moving masses must be produced during the same etching step of the two surface layers of silicon. The two mobile masses produced are therefore necessarily identical. In addition, the multilayer etching that must be carried out through the silicon / dielectric / silicon stack in a single technological step is not easy to implement. This method is therefore not suitable for producing a sensor comprising two superimposed moving masses of different geometry.

[0008] In documents US 2005 / 0091843 A1 and US 2009 / 0283917 A1, it is proposed to form a sensor comprising two moving masses made in two separate substrates. A sealing of the two substrates is then carried out to superimpose the two moving masses produced and obtain the sensor. With this method, the moving masses of the sensor may or may not be similar. However, a disadvantage of this method is that the sealing between the two substrates requires an alignment of the two substrates relative to each other. This alignment step is very sensitive and difficult to implement, and a misalignment between the two substrates can cause in particular a misalignment of the two centers of gravity of the superimposed moving masses, which can compromise the balancing of the sensor. Document FR 3 013 441 A1 discloses a micro-device comprising two moving elements.The first movable element comprises a first portion of a first layer of material and a second portion of a second layer of material. The second movable element comprises a first portion of the second layer of material and a second portion of the first layer of material.

[0009] In document US 2015 / 0375995 A1, the production of a first mobile element of a sensor in a substrate is described, then the sealing of a cover covering the first mobile element, then a thinning of the part of the substrate serving as a mechanical handle (at the rear face of the substrate), and finally the production of a second mobile element in this thinned part of the substrate from its rear face. This method allows the production of similar or different mobile elements. However, it is necessary to carry out a sealing with alignment of the substrate and the cover. In addition, the alignment of the second mobile element with respect to the first mobile element poses problems because the alignment marks arranged on the rear face of the substrate and used for the alignment of the cover disappear during the thinning of the part of the substrate serving as a mechanical handle.The alignment of the second moving element must therefore be carried out either by using infrared vision of the elements, or by carrying out the alignment in relation to the transferred cover. In both cases, this can lead to significant misalignments between the two moving elements. STATEMENT OF THE INVENTION

[0010] An aim of the present invention is to propose a micro-device, for example of the inertial sensor type, comprising at least one mobile element and not having at least some of the drawbacks of the micro-devices of the prior art, that is to say limiting or eliminating the dynamic unbalance effect, which eliminates the alignment constraints encountered during the production of the micro-devices of the prior art, and which can be produced in a compact manner with a reduced cost.

[0011] For this, the present invention proposes a micro-device comprising at least: a first layer of material, a second layer of material, a fixed part, a first movable element comprising at least a first portion of the first layer of material and at least a second portion of the second layer of material, a second movable element comprising at least a first portion of the second layer of material and at least a second portion of the first layer of material, first suspension means formed in the first layer of material and / or in the second layer of material, second suspension means formed in the first layer of material and / or in the second layer of material, and wherein: the first and second movable elements are capable of moving relative to each other and relative to the fixed part, the first and second layers of material are arranged one above the other,the first portion of the first layer of material is integral with the second portion of the second layer of material, the first movable element is suspended from the fixed part by the first suspension means, the second movable element is suspended from the fixed part by the second suspension means, the first portion of the second layer of material is integral with the second portion of the first layer of material.

[0012] This distribution of the portions of material forming the moving elements within the different layers of material avoids generating a significant dynamic imbalance resulting from the displacement of the overall center of gravity of the micro-device.

[0013] The characteristics of this micro-device are compatible with an embodiment not involving the implementation of an alignment of elements intended to be sealed to each other. This micro-device can therefore be produced without having to implement such an alignment.

[0014] The creation of a mobile element within two superimposed layers also makes it possible to reduce the size of this mobile element.

[0015] When the moving element comprises different portions from two separate layers electrically insulated from each other, several different electrical potentials can be applied to this moving element.

[0016] Generally speaking, the term "material layer" can refer to a monolithic material layer or a set of several superimposed layers.

[0017] The second portions of the first and second layers of material may correspond to simple portions of these layers, for example rectangular in shape, or be of more complex geometry, for example forming a frame, a plurality of pads, a grid, etc.

[0018] This micro-device therefore comprises a fixed part from which at least two superimposed mobile elements are suspended. The distribution of the portions of material forming the mobile elements in the two layers of material may correspond to a head-to-tail arrangement of the mobile elements. These mobile elements may therefore be arranged in a nested manner relative to each other within the micro-device.

[0019] The moving elements can be made from layers of material stacked on top of each other. This reduces the size of the micro-device compared to those in which the moving elements are made from the same layer of material, either next to each other or concentrically, which results in a lower production cost. This advantage is also found when the micro-device has only one moving element.

[0020] Furthermore, such a micro-device does not have any constraints limiting the shape and dimensions of the moving elements which may or may not be similar for each of the moving elements. When the shape and dimensions of the moving elements are similar, this facilitates the balancing of the micro-device.

[0021] According to the invention, the first and second mobile elements are capable of moving substantially in phase opposition with respect to each other, when the micro-device is subjected to an external action (displacement, acceleration, rotation, shock, etc.). In this case, the distribution of the portions of material forming each of the mobile elements within the two layers is very advantageous because the dynamic imbalance which could be generated by such a movement is reduced.

[0022] The first and second movable members may be capable of moving substantially in phase with each other.

[0023] The centers of gravity of the first and second moving elements are aligned one above the other along an axis substantially perpendicular to major faces of the first and second layers of material. This configuration further reduces the effects of overall dynamic unbalance, or even eliminates them.

[0024] The first and second movable elements may be symmetrical about a center of symmetry located between the first portions of the first and second layers of material and on the axis substantially perpendicular to the main faces of the first and second layers of material.

[0025] The micro-device can be such that: at least a first end of the first portion of the first layer of material is connected to the second portion of the second layer of material and at least a second end of the first portion of the first layer of material forms a free end of the first movable element, and at least a first end of the first portion of the second layer of material is connected to the second portion of the first layer of material and at least a second end of the first portion of the second layer of material forms a free end of the second movable element.

[0026] In this case, the second end of the first portion of the first layer of material may be disposed between the first end of the first portion of the first layer of material and the second portion of the first layer of material, and the second end of the first portion of the second layer of material may be disposed between the first end of the first portion of the second layer of material and the second portion of the second layer of material.

[0027] The first and second movable elements may be arranged nested and / or concentric with respect to each other.

[0028] The first portion of the first layer of material may be connected to the second portion of the second layer of material via at least a first portion of an intermediate layer disposed between the first and second layers of material, and / or the first portion of the second layer of material may be connected to the second portion of the first layer of material via at least a second portion of the intermediate layer.

[0029] The micro-device may further comprise elements for detecting and / or measuring a movement of the first mobile element and / or the second mobile element relative to the fixed part and / or a movement of the first mobile element relative to the second mobile element, and / or elements capable of moving the first mobile element and / or the second mobile element relative to the fixed part and / or moving the first mobile element relative to the second mobile element.

[0030] In an advantageous configuration, the first movable element can form a first detection element, and the second movable element can form a second detection element, the first and second detection elements being able to carry out an inertial measurement of angular quantities experienced by the micro-device.

[0031] The first movable element and / or the second movable element may be capable of moving in translation and / or in rotation relative to the fixed part and / or relative to each other.

[0032] The fixed portion may comprise portions of the first and second layers of material disposed around the first and second movable members and / or surrounded by the first and second movable members.

[0033] The fixed portion may comprise a support layer such that the first layer of material is disposed between the support layer and the second layer of material.

[0034] According to a particular embodiment, the micro-device may further comprise at least one intermediate mobile element suspended from the fixed part and capable of moving relative to the fixed part, and the first and second mobile elements may be suspended from the intermediate mobile element and be capable of moving relative to the intermediate mobile element and to the fixed part.

[0035] In this particular embodiment, the intermediate mobile element ensures absorption of external vibrations to the micro-device. Thus, the mobile elements are not subjected to these external vibrations.

[0036] Furthermore, the micro-device according to this particular embodiment may be such that: the fixed part comprises a fixed frame at least partly surrounding the intermediate mobile element, and the intermediate mobile element forms a mobile frame suspended from the fixed frame, and / or the micro-device further comprises a first cavity of which at least part of the walls is formed by the fixed part and in which the intermediate mobile element is encapsulated, and a second cavity arranged within the first cavity, of which at least part of the walls is formed by the intermediate mobile element and in which the first and second mobile elements are encapsulated.

[0037] Advantageously, the second cavity can be isolated from the first cavity.

[0038] Thus, it is possible to encapsulate the first and second mobile elements within a particular atmosphere (in terms of gas nature and / or pressure) different from that in which the intermediate mobile element is located, for example different from the ambient air in which the micro-device is located. The second cavity can be hermetically or tightly closed with respect to the first cavity.

[0039] The invention also relates to a method for producing a micro-device, comprising at least: etching a first layer of material such that at least a first portion of the first layer of material forms a first part of at least one first mobile element and that at least a second portion of the first layer of material forms a first part of at least one second mobile element, producing a second layer of material on the first layer of material, etching the second layer of material such that at least a second portion of the second layer of material forms a second part of the first mobile element and is integral with the first portion of the first layer of material and that at least a first portion of the second layer of material forms a second part of the second mobile element and is integral with the second portion of the first layer of material,these steps being implemented such that: the first mobile element is suspended from a fixed part by first suspension means formed in the first layer of material and / or in the second layer of material, the second mobile element is suspended from the fixed part by second suspension means formed in the first layer of material and / or in the second layer of material, the first and second mobile elements are able to move relative to each other and relative to the fixed part, the first and second mobile elements are able to move substantially in phase opposition relative to each other when the micro-device is subjected to an external action, the centers of gravity of the first and second mobile elements are aligned one above the other along an axis substantially perpendicular to main faces of the first and second layers of material.

[0040] The production of the second layer of material on the first layer of material may comprise a transfer of the second layer of material onto the first layer of material such that an intermediate layer is arranged between the first and second layers of material, the method may further comprise, after the etching of the second layer of material, an etching of the intermediate layer such that at least a first portion of the intermediate layer connects the first portion of the first layer of material to the second portion of the second layer of material and, when the second mobile element is produced, that at least a second portion of the intermediate layer connects the first portion of the second layer of material to the second portion of the first layer of material.

[0041] According to a first embodiment, a sacrificial layer may be arranged between the first layer of material and a support layer, the method further comprising, after etching the second layer of material, providing access to the sacrificial layer through the support layer and then etching a portion of the sacrificial layer via the access formed through the support layer, releasing at least the first portion of the first layer of material (and also the second portion of the first layer of material when the second mobile element is produced) from the support layer. In this case, the release of the first mobile element (and of the second mobile element when the latter is produced) may be done from two opposite faces of the micro-device.

[0042] According to a second embodiment, a sacrificial layer may be arranged between the first layer of material and a support layer, the method may further comprise, between the etching of the first layer of material and the production of the second layer of material, an etching of a first part of the sacrificial layer partially releasing at least the first portion of the first layer of material (and the second portion of the first layer of material when the second mobile element is produced) with respect to the support layer, and after the etching of the second layer of material, an etching of a second part of the sacrificial layer via openings formed through the first and second layers of material during the previous etchings of the first and second layers of material,completing the release of the first portion of the first layer of material (and of the second portion of the first layer of material when the second mobile element is produced) with respect to the support layer. In this case, the release of the first mobile element, and possibly of the second mobile element, can be carried out without having to form an access to the sacrificial layer from a rear face of the support layer, and only from a front face of the micro-device.,

[0043] The steps of etching the first and second material layers may form release holes passing through the first and second material layers and which are aligned above each other. Thus, the release of the first portion (and possibly the second portion) of the first material layer may be achieved by using etchants reaching the sacrificial layer via these release holes.

[0044] The etching step of the second layer of material can form additional release holes passing through the second layer of material. This configuration makes it possible in particular to obtain different mobilities of the mobile elements relative to each other, when several mobile elements are produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be better understood by reading the description of exemplary embodiments given for purely indicative and non-limiting purposes with reference to the appended drawings in which: there figure 1 schematically represents a micro-device, object of the present invention, according to a particular embodiment, the Figures 2A to 2M represent the steps of a method for producing a micro-device, the subject of the present invention, according to a first embodiment, the Figures 3A to 3Hrepresent the steps of a method for producing a micro-device, the subject of the present invention, according to a second embodiment, the figure 4 schematically represents a micro-device, object of the present invention, according to another particular embodiment, the Figure 5 represents a sectional view of a part of a micro-device, object of the present invention, before the implementation of the final release of the movable elements of the micro-device, in the presence of additional release holes formed through the second layer of material, the Figures 6A and 6B represents examples of embodiments of release holes in a micro-device, object of the present invention, the figure 7represents a sectional view of a portion of a micro-device, object of the present invention, after the implementation of the final release of the movable elements of the micro-device, in the absence of additional release holes formed through the second layer of material, the figure 8 schematically represents a micro-device, object of the present invention, comprising an intermediate mobile element, the Figures 9A to 9K represent the steps of a method for producing a micro-device, the subject of the present invention, comprising an intermediate mobile element, the figure 10 schematically represents a micro-device, which is not part of the invention. Figures 11A and 11B schematically represent a micro-device, object of the present invention, according to another embodiment, the figure 12 schematically represents a micro-device, object of the present invention, according to another embodiment.

[0046] Identical, similar or equivalent parts of the different figures described below bear the same numerical references so as to facilitate the transition from one figure to another.

[0047] The different parts represented in the figures are not necessarily on a uniform scale, to make the figures more readable.

[0048] The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with each other. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0049] We first refer to the figure 1 which schematically represents a micro-device 100 according to a particular embodiment.

[0050] The micro-device 100 is produced from a stack comprising a support layer 102, a first layer of material 104 and a second layer of material 106, the first layer 104 being arranged between the support layer 102 and the second layer 106. In the particular embodiment described here, the material of the first and second layers 104, 106 is a semiconductor, for example doped or undoped silicon, doped or undoped germanium, SiGe, etc.

[0051] A layer 108, called the sacrificial layer, is disposed between the support layer 102 and the first layer 104. In addition, a layer 110, called the intermediate layer, is disposed between the first layer 104 and the second layer 106. In the particular embodiment described here, the layers 108, 110 each comprise a dielectric material, for example SiO 2 . Generally, the materials of the layers 108, 110 are such that they can be selectively etched with respect to the materials of the first and second layers 104, 106.

[0052] The micro-device 100 shown in the figure 1 corresponds to an inertial sensor comprising a first mobile element 111 formed by a first portion 112 of the first layer 104 and a second portion 118 of the second layer 106, and a second mobile element 113 formed by a first portion 114 of the second layer 106 and a second portion 126 of the first layer 104.

[0053] The first portion 112 of the first layer 104 comprises a first end 116 connected, or secured, to the second portion 118 of the second layer 106 via a first portion 120 of the intermediate layer 110. The first portion 120 of the intermediate layer 110 is part of the first mobile element 111. The first portion 112 comprises a second end 122 forming a free end of the first mobile element 111, that is to say an end which is not in contact with a portion of the intermediate layer 110.

[0054] The first portion 114 of the second layer 106 comprises a first end 124 connected to the second portion 126 of the first layer 104 via a second portion 128 of the intermediate layer 110 forming part of the second mobile element 113. The first portion 114 of the second layer 106 comprises a second end 130 forming a free end of the second mobile element 112.

[0055] In this micro-device 100, the first and second mobile elements 111, 113 form mobile masses, or seismic masses, capable of moving relative to a fixed part 115 of the micro-device 100. The fixed part 115 comprises portions 117, 119 of the first and second layers 104, 106 from which the mobile elements 111, 113 are suspended by means of first and second suspension means 121, 123 respectively. In the particular embodiment shown in the figure 1 , these first and second suspension means 121, 123 correspond to portions of the first and second layers of material 104, 106 forming micro-beams suspending the portions 112, 114, 118 and 126 of the mobile elements 111, 113 to the portions 117, 119 of the first and second layers of material 104, 106. The fixed part 115 also includes the support layer 102.

[0056] Alternatively, it is possible for the suspension means 121, 123 to be formed only by portions of one of the two layers of material 104, 106. For example, one or each of the movable elements 111, 113 may be suspended from the fixed part 115 by micro-beams connected only to the first portion 112, 114, or to the second portion 118, 126.

[0057] Each of the movable elements 111, 113 is formed by a portion of one of the layers 104, 106 connected to a portion of the other of the layers 104, 106, the two movable elements 111, 113 being arranged in an interlocking manner relative to each other.

[0058] In the particular embodiment described in connection with the figure 1, these two detection elements corresponding to the two mobile elements 111, 113 are identical to each other and arranged head to tail to each other, that is to say are symmetrical with respect to a center of symmetry C located between the first portions 112, 114 of the first and second layers 104, 106. In the embodiment described in connection with the figure 1 , the second end 122 of the first portion 112 of the first layer 104 is disposed between the first end 116 of the first portion 112 of the first layer 104 and the second portion 126 of the first layer 104, and the second end 130 of the first portion 114 of the second layer 106 is disposed between the first end 124 of the first portion 114 of the second layer 106 and the second portion 118 of the second layer 106.

[0059] In this particular embodiment, the centers of gravity of the first and second mobile elements 111, 113 are aligned one above the other along an axis substantially perpendicular to the main faces of the first and second layers of material 104, 106 (faces parallel to the plane (X,Y)), that is to say here aligned along an axis parallel to the axis Z and passing through the center of symmetry C.

[0060] Thus, when the micro-device 100 is subjected to external forces, the phase-opposition movement of the first and second mobile elements 111, 113 does not generate any or little dynamic imbalance.

[0061] Alternatively, it is possible that these mobile elements 111, 113 are different from one another, that is to say that they do not have the same shape and / or the same dimensions.

[0062] Finally, the micro-device 100 here comprises electrically conductive vias 132, 134 electrically connecting the first and second layers 104, 106 together.

[0063] Portions of material of at least one of the layers 104, 106 may also connect the first movable element 111 to the second movable element 113. Such portions may thus ensure a certain mechanical support of the first portions 112, 114. However, these portions of material, which correspond for example to micro-beams, are such that the movable elements 111, 113 are movable relative to each other.

[0064] THE Figures 2A to 2M represent the steps of a method for producing a micro-device 100 according to a first embodiment.

[0065] The micro-device 100 is for example made from a first substrate of the semiconductor on insulator type, for example SOI (silicon on insulator), SiGeOl, GeOl, etc. This substrate, visible on the Figure 2A, comprises the support layer 102, a buried dielectric layer, or BOX (“Buried Oxide”), forming the sacrificial layer 108 and comprising for example semiconductor oxide such as SiO 2 , and a surface layer of semiconductor comprising for example silicon and forming the first layer of material 104. The thickness of each of the layers 104 and 108 is for example between approximately 100 nm and 400 µm, or even greater than 400 µm. For example, the thickness of the layer 104 is typically equal to approximately 60 µm, and that of the layer 108 equal to approximately 2 µm. Generally, the first layer 104 corresponds to a layer of material suitable for producing one of the mobile elements of the micro-device 100, and the material of the sacrificial layer 108 is capable of being selectively etched with respect to that of the first layer 104.

[0066] Alternatively, the micro-device 100 can be produced from a solid substrate, or bulk, comprising for example a semiconductor such as silicon and forming the support layer 102, on which are successively deposited the sacrificial layer 108, for example dielectric such as a layer of semiconductor oxide or glass, and the first layer of material 104 in which one of the mobile elements of the micro-device 100 is intended to be produced, corresponding for example to a layer of semiconductor such as doped or undoped silicon, doped or undoped germanium, etc. The sacrificial layer 108 and the first material layer 104 can be formed by implementing different techniques such as LPCVD (low pressure chemical vapor deposition), PECVD (plasma-enhanced chemical vapor deposition), ALD (atomic layer deposition), PVD (physical vapor deposition), or even epitaxy, etc.

[0067] When different regions of the first layer of material 104 are intended to be subjected to different electrical potentials, the first layer 104 may be structured so as to define one or more electrical insulation trenches 136 between these different areas of the first layer 104 ( Figure 2B ). For example, a DRIE (deep reactive ion etching) type etching can be implemented to form these trenches 136, such etching allowing a very selective and deep etching of the semiconductor (here silicon) of the first layer 104, the sacrificial layer 108 serving as a stop layer for this etching.

[0068] This or these trenches 136 can then be blocked or not by at least one dielectric material 138 ( Figure 2C). This dielectric material 138 may be, for example, a thermal oxide, a nitride, undoped polysilicon, or a combination of different dielectric materials. Filling these trenches 136 with the dielectric material 138 will make it possible to obtain better mechanical strength of the mobile structure having areas of different electrical potentials which will be produced in the first layer 104. The documents “Fabrication challenges and test structures for high-aspect-ratio SOI MEMS devices with refilled electrical isolation trenches” by J. Xie, Microsyst. Technol. (2015) 21:1719-1727, and “Fabrication of keyhole-free ultra-deep high-aspect-ratio isolation trench and its applications” by Y. Zhu et al., J. Micomech. Microeng. 15 (2005), 636-642, describe the production of such trenches filled with dielectric material.If the trenches 136 are not subsequently blocked by the dielectric material 138, they can be produced subsequently, for example at the same time as the structuring of the first layer 104 forming the portions 112 and 126 of the mobile elements 111, 113 of the micro-device 100 (see step described below in connection with the . 2D figure ).

[0069] Alternatively, it is possible not to make the trenches 136 if the micro-device 100 does not require having, in the first layer 104, different zones electrically insulated from each other.

[0070] The first layer of material 104 is then structured, here by etching (for example DRIE) so as to define the first portion 112 intended to be part of the first mobile element 111 and the second portion 126 intended to be part of the second mobile element 113 ( 2D figure). Part of the suspension means 121, 123 (those intended to maintain the portions 112 and 126 in a suspended state with respect to the portions 119) are also produced in the first layer 104, as well as the portions 119 of the fixed part 115 of the micro-device 100. Elements for detecting and / or measuring the movement of one or more mobile elements 111, 113, for example electrostatic combs, may also be produced in the first layer 104. Depending on the nature of the micro-device 100, it is also possible for this structuring of the first layer 104 to form elements capable of moving, i.e. actuating means, the or one of the mobile elements 111, 113. Finally, release holes 140 intended for the subsequent release of the portions 112, 126 with respect to the support layer 102 are also made through the first layer 104.These release holes 140 will be used during the etching of the sacrificial layer 108 which will be implemented to release the portions 112, 126 from the support layer 102.

[0071] The second layer of material 106 is then produced on the first layer of material 104. In the first embodiment described here, the second layer 106 corresponds to the surface layer of a second substrate of the semiconductor on insulator type, for example SOI, SiGeOl, GeOl, etc. This second substrate comprises a bulk layer 142 and a buried dielectric layer 144 disposed between the bulk layer 142 and the second layer of material 106.

[0072] This second substrate can be transferred onto the first layer of material 104 using different techniques: direct bonding between the first layer 104 and the second layer 106 (direct silicon / silicon bonding for example, or more generally semiconductor / semiconductor), or else direct bonding between one of the first and second layers 104, 106 and a dielectric layer previously formed on the other of the first and second layers 104, 106 (direct semiconductor / dielectric bonding, for example silicon / SiO 2 ), or else direct bonding between two dielectric layers previously formed on each of the first and second layers 104, 106 (direct dielectric / dielectric bonding, for example SiO 2 / SiO 2 ). Alternatively, this joining between the first and second layers 104, 106 can be achieved by metal sealing (for example of the Au / Si, Au / Au, Au / Sn, Al / Ge, etc. type).) by first forming such a metal layer or cord on at least one of the two layers 104, 106. The two layers 104, 106 can also be joined together using a non-metallic sealing cord, for example a polymer one.

[0073] On the example of the Figure 2E , a direct dielectric / dielectric or semiconductor / dielectric bonding is implemented to secure the two layers 104, 106. An intermediate layer 110, comprising a dielectric material such as SiO 2 , is present between the layers 104, 106.

[0074] Alternatively, the second layer of material 106 may not be the surface layer of a semiconductor-on-insulator type substrate, but be a simple layer of material, for example of semiconductor, deposited on the first layer 104, with possibly the presence of the intermediate layer 110 between the layers 104, 106. Figure 2Frepresents such a variant, in which the second layer 106 and the intermediate layer 110 are deposited for example by LPCVD, PECVD, ALD, PVD, epitaxy, etc.

[0075] As shown in the Figure 2G , the layers 142 and 144 are removed. The second layer 106 is optionally thinned to the desired thickness. When the second layer 106 is produced directly by deposition, this thinning is generally implemented due to the thickness of the deposited material which generally does not correspond to the desired thickness of the second mobile element 114. The thickness of the second layer 106 may be between approximately 100 nm and 400 µm, or even greater than approximately 400 µm, and for example equal to approximately 60 µm. The thickness of the second layer 106 is equal or not to that of the first layer 104.

[0076] As previously described for the first layer 104, when different regions of the second layer of material 106 are intended to be subjected to different electrical potentials, the second layer 106 can be structured so as to define one or more electrical insulation trenches 146 between these different areas of the second layer 106 ( Figure 2H ). For example, DRIE type etching can be implemented to form these trenches 146, the intermediate layer 110 serving here as a stop layer.

[0077] This or these trenches 146 can then be blocked or not by at least one dielectric material 148 ( Figure 2I). This dielectric material 148 may be, for example, one of the materials previously mentioned for the dielectric material 138. If the trenches 146 are not blocked by the dielectric material 148, they may be produced subsequently, for example at the same time as the structuring of the second layer 106 forming the other portions 114, 118 of the mobile elements 111, 113 of the micro-device 100 (see step described below in connection with the Figure 2K ).

[0078] The two layers 104 and 106 can be electrically connected by making one or more interconnection vias 132, 134 between these two layers ( Figure 2J). This or these vias 132, 134 are produced by successively etching the layers 106 and 110 with a stop on the first layer 104. This or these vias are then filled with an electrically conductive material (for example a metallic material such as Al, W, Cu, Au, or a doped semiconductor such as Si or Ge).

[0079] The second layer 106 is then structured, for example by etching, so as to define the portions 114, 118 of the mobile elements 111, 113, as well as the portions 117 of the fixed part 115 and the suspension means 121, 123 of the portions 114, 118 with respect to the portions 117 ( Figure 2K). Elements for detecting and / or measuring the movement of one or more mobile elements 111, 113, for example electrostatic combs, may also be formed in the second layer 106. Depending on the nature of the micro-device 100, it is also possible for this structuring of the second layer 106 to form elements capable of moving the or one of the mobile elements 111, 113, i.e. actuation means. Finally, release holes 152 intended for the subsequent release of the portions 114, 118 from the intermediate layer 110 are also made through the second layer 106. These release holes 152 will be used during the etching of the intermediate layer 110 which will be implemented to release these portions 114, 118.

[0080] As shown in the Figure 2L, an etching of a portion of the support layer 102, from its rear face, is then implemented, forming an access 154 to the sacrificial layer 108. This access 154 is located opposite the portions 112, 126.

[0081] The movable elements 111, 113 are then released via a selective removal of the materials of the layers 108, 110 (dielectrics) relative to the other materials of the layers 102, 104, 106 (semiconductors), as shown in the figure 2M Portions 120, 128 of the intermediate layer 110 are retained, these portions providing the link between the first portions 112, 114 and the second portions 118, 126.

[0082] All etchings of the first and second layers 104, 106 implemented (previously described in connection with the Figures 2B , 2D , 2H, 2D and 2K) during this method are advantageously implemented using alignment marks, or alignment reference frames, present on the rear face of the support layer 102 (the one located on the side opposite to that where the sacrificial layer 108 is located), preferably on a part of this rear face which will not be etched to form the access 154. Because these alignment marks are retained until the release of the mobile elements 111, 113, they can be used to produce these mobile elements 111, 113 in a manner aligned with each other. Alignment with such marks can be done, for example, with optical or interference systems commonly used on photolithography equipment.

[0083] Alternatively, it is possible that the access 154 is not formed by etching the entire portion of the support layer 102 located opposite the portions 112 and 126, but by forming release holes through this portion of the support layer 102.

[0084] The micro-device 100 previously described comprises two detection elements, each comprising at least one mobile element formed from two portions of the layers 104, 106, produced in a nested manner one above the other. Alternatively, the micro-device 100 may comprise a greater number of detection elements, or mobile elements, produced in a nested manner one above the other. For this, the steps previously described in connection with the Figures 2E to 2K are in this case repeated one or more times before releasing the mobile elements from these superimposed elements.

[0085] THE Figures 3A to 3Hrepresent the steps of a method for producing a micro-device 100 according to a second embodiment.

[0086] As in the first embodiment, the method is implemented from a stack of layers comprising the support layer 102, the sacrificial layer 108 and the first layer of material 104 ( Figure 3A ).

[0087] During the same etching step, the electrical insulation trenches 136, the release holes 140 as well as the portions 112 and 126 of the mobile elements 111, 113 and the parts of the suspension means 121, 123 connected to the portions 112, 126 are then produced in the first layer 104 ( Figure 3B). In this second embodiment, the trenches 136 are not subsequently blocked by the dielectric material 138 (but they could be, as in the first embodiment), which makes it possible to avoid the risks of thermal expansion which may appear due to the difference in thermal expansion coefficients between the dielectric material 138 and the material of the first layer 104. Other elements for detecting and / or actuating the mobile elements 111, 113 may also be formed in the first layer 104.

[0088] Partial etching of the sacrificial layer 108 is then carried out in order to partially release the portions 112 and 126. Portions 160 of the sacrificial layer 108 are kept under the portions 112, 126 (and more generally the different elements produced in the first layer 104) in order to maintain a certain mechanical strength of these elements during the rest of the process.

[0089] The second layer of material 106 is then produced on the first layer of material 104. As in the first embodiment, the second layer 106 here corresponds to the surface layer of a second substrate of the semiconductor-on-insulator type comprising the bulk layer 142 and the buried dielectric layer 144. In addition, the intermediate layer 110 is also present between the layers 104, 106 ( 3D figure ). The different sealing techniques previously described for the first embodiment can be applied to this second embodiment. Alternatively, the second layer of material 106 may not be the surface layer of a semiconductor type substrate, but be a simple layer of material, for example semiconductor, deposited on the first layer 104, with possibly the presence of the intermediate layer 110 between the layers 104, 106.

[0090] As shown in the Figure 3E, layers 142 and 144 are removed. The second layer 106 is here also thinned to the desired thickness.

[0091] As in the first embodiment, the two layers 104 and 106 can be electrically connected by making one or more interconnecting vias 132, 134 between these two layers ( Figure 3F ). The second layer 106 is then structured, for example by etching, so as to define the portions 114, 118, the release holes 152, the holding elements 121, 123, detection and / or actuation elements previously described for the first embodiment ( Figure 3G ). This etching also serves here to form the insulation trenches 146 which are then filled or not with the dielectric material 148 (not folded in this second embodiment).

[0092] The movable elements 111, 113 are then released via selective removal of the materials of the layers 108, 110 relative to the other materials of the layers 102, 104, 106, as shown in the Figure 3H . Due to the partial release of the elements of the first layer 104 (portions 112 and 126) previously carried out, it is not necessary to carry out, prior to this release step, an etching of the support layer 102 to form an access to the sacrificial layer 108. The etching agents used therefore carry out the etching of the portions 160 through the release holes 152 and 140.

[0093] As in the first embodiment, portions 120, 128 of the intermediate layer 110 are retained, these portions providing the mechanical link between the first portions 112, 114 and the second portions 118, 126.

[0094] Furthermore, as in the first embodiment, all the etchings of the first and second layers 104, 106 implemented during this method are advantageously implemented using alignment marks, or alignment reference, present on the rear face of the support layer 102. Because no access to the sacrificial layer 108 is made through the support layer 102, the entire surface of the rear face of the support layer 102 is available for these alignment marks.

[0095] The micro-device 100 previously described comprises two detection elements, each comprising at least one mobile element each formed from portions of the two layers 104, 106, produced in a nested manner one above the other. Alternatively, the micro-device 100 may comprise a greater number of detection elements produced in a nested manner one above the other. For this, the steps previously described in connection with the 3D to 3G figures are in this case repeated one or more times before releasing the mobile elements from these superimposed elements.

[0096] An exemplary embodiment of such a micro-device 100 comprising a greater number of detection elements produced in a nested manner one above the other is shown in the figure 4. In this figure, two additional layers of material 204, 206 are arranged above the second layer 106, in which detection elements similar to those made in the layers 104, 106 are also made, in particular mobile elements 211, 213 each suspended from the fixed part 115 which is common to the mobile elements 111, 113, 211 and 213. The layers 204, 206 are each arranged on one of the intermediate layers 210 and 211. Furthermore, in this exemplary embodiment, the vias 134 form electrical contacts for each of the layers 104, 106, 204, 206. Finally, release holes 240, 252 formed in the layers 204, 206 are aligned with those formed in the layers 104, 106.

[0097] It is possible for each moving element to comprise portions of two, or more, consecutive layers of material.

[0098] In the second embodiment previously described, the release of the two detection elements produced in the layers 104, 106 is obtained by introducing etching agents from the upper face of the second layer 106. The distance between this upper face and the portions 160 of the sacrificial layer 108 to be etched during the release of the detection structures is different from that between this upper face and the intermediate layer 110. In addition, due to the partial release of the structure formed in the first layer 104 implemented prior to the production of the second layer 106, the portions of material to be etched in the layers 108 and 110 are not the same.To carry out the etching of the portions 160 of the sacrificial layer 108 retained at the end of the partial release step, the release holes 140 formed through the first layer 104 are aligned with at least a portion of the release holes 152 formed through the second layer 106. In addition, as shown in the . Figure 5 , it is possible to make additional release holes 162 through the second layer 106 because during the final release step, the intermediate layer 110 has not yet been etched, unlike the sacrificial layer 108. A top view of the first layer 104 having the release holes 140 is visible on the Figure 6A , and a top view of the second layer 106 having the release holes 152 aligned with the holes 140, as well as the additional release holes 162, is visible in the Figure 6B .

[0099] Alternatively, it is also possible not to make the additional release holes 162. In this case, at the end of the release step, portions 164 of the intermediate layer 110 may still be present under certain parts of the second layer 106 (see figure 7 ). This configuration can be advantageous when a different mechanical strength is sought for the elements formed in the second layer 106 compared to those formed in the first layer 104.

[0100] For certain applications, it may be advantageous to isolate the mobile elements of the resonant micro-device 100 from vibrations external to this micro-device 100. For this, the micro-device 100 can be produced by producing the mobile structures not such that the mobile elements 111, 113 are suspended directly from the fixed part 115 of the micro-device 100 which comprises for example the support layer 102, but secured to an intermediate mobile element, for example in the form of a mobile frame, forming an intermediate suspension stage between the mobile elements 111, 113 and this fixed part 115 of the micro-device 100. The mobile elements 111, 113 are in this case suspended in and from this mobile frame, itself connected to the fixed part by suspension means. In such a configuration, the movable frame may, for example, be hermetically sealed to ensure a vacuum, or more generally an atmosphere (nature of gas, pressure, etc.) adapted to the operation of mobile structures.

[0101] As shown schematically in the figure 8 , the micro-device 100 comprises a fixed part 302 of which the support layer 102 is for example a part. It also comprises an intermediate mobile element 304 corresponding, in this exemplary embodiment, to a mobile frame. The intermediate mobile element 304 is arranged for example inside a space surrounded by a frame formed by the fixed part 302. In addition, the intermediate mobile element 304 is suspended from the fixed part 302 by first holding means 306 corresponding for example to first suspension holding arms which may correspond to micro-beams.

[0102] These first holding means 306 are such that the intermediate mobile element 304 can move according to one or more degrees of freedom relative to the fixed part 302 of the micro-device 100, for example in translation parallel to one of the axes X, Y or Z, and / or a rotation according to at least one of the axes X, Y or Z.

[0103] Each of the mobile elements 111, 113 is connected to the intermediate mobile element 304 by second holding means 308, 310 corresponding for example to second suspension holding arms which may correspond to micro-beams.

[0104] In such a micro-device 100, the intermediate mobile element 304 forms an intermediate suspension stage making it possible to isolate the mobile elements 111, 113 from external movements or vibrations experienced by the micro-device 100, and therefore by the fixed part 302.

[0105] An example of a method for producing such a micro-device 100 is described in connection with the Figures 9A to 9K .

[0106] As in the previous embodiments, the method is implemented from a stack of layers comprising the support layer 102, the sacrificial layer 108 and the first layer of material 104 ( Figure 9A ).

[0107] During the same etching step, the electrical insulation trenches 136, the release holes 140 as well as the portions 112, 126 of the mobile elements 111, 113 are then produced in the first layer 104 ( Figure 9B ). This etching step also delimits, within the first layer 104, parts 312 of the intermediate mobile element 304 with respect to the fixed part 302 intended to remain integral with the support layer 102. A part of the holding elements 306, 308 and 310 can also be produced.

[0108] The second layer of material 106 is then produced on the first layer 104, here via a transfer of a semiconductor-on-insulator type substrate and via the intermediate layer 110 ( Figure 9C ).

[0109] As shown in the Figure 9D , layers 142 and 144 are removed. The second layer 106 is here also thinned to the desired thickness.

[0110] As in the previous embodiments, the two layers 104 and 106 can be electrically connected by making one or more interconnecting vias 132, 134 between these two layers ( Figure 9E ).

[0111] A dielectric layer 314 is then formed on the second layer 106. Openings 316 are formed through this dielectric layer 314 opposite the vias 132, 134 ( Figure 9F ).

[0112] An electrically conductive layer, for example metallic, is then deposited on the dielectric layer 314 and in the openings 316, then etched in order to preserve portions 318 arranged in the openings 316 forming electrical contacts connected to the vias 132, 134, as well as portions 320 intended for the subsequent production of metallic sealing beads intended to ensure hermetic closure of a first cavity in which the mobile elements 112, 114 will be arranged and of a second cavity in which the intermediate mobile element 304 will be arranged ( Figure 9G ).

[0113] Layers 314 and 106 are then etched to define portions 114 and 118 (and also other holding, sensing, etc. elements) as well as any isolation trenches 146, release holes 152 and also define other portions 322 of intermediate movable element 304 ( figure 9H ).

[0114] The support layer 102 is then etched in order to form an access 154 to the parts of the sacrificial layer 108 located at the part of the micro-device 100 comprising the portions 112, 126 as well as that at which the intermediate mobile element 304 is located ( Figure 9I ).

[0115] The various mobile elements of the micro-device 100 are then released by etching the parts of the layers 108 and 110 to which these mobile elements 111, 113 and 304 are linked ( Figure 9J ). The parts of layer 314 not covered by the metal portions 320 are also etched.

[0116] The structure thus obtained in Figure 9J may also be encapsulated to form the micro-device 100 as shown in the figure 9K, on which the detection elements comprising the mobile elements 111, 113 are encapsulated in a cavity 324 delimited in particular by the intermediate mobile element 304. The intermediate mobile element 304 is itself encapsulated in a cavity 326 which includes the cavity 324. The cavities 324, 326 are for example hermetically isolated from each other thanks to the sealing bead 328 separating them. The intermediate mobile element 304 here forms a mobile frame suspended from the fixed frame formed by the fixed part 302.

[0117] In the embodiments previously described, the micro-device 100 comprises several mobile elements. According to an example outside the scope of the invention shown in the figure 10, the micro-device 100 comprises a single mobile element 111 formed by the first portion 112 of the first layer 104 and the second portion 118 of the second layer 106. The portions 112 and 118 are connected, or secured, to each other by means of the portion 120 of the intermediate layer 110.

[0118] This mobile element 111 forms a mobile mass capable of moving relative to the fixed part 115 of the micro-device 100. This fixed part 115 comprises the portions 117 and 119 of the first and second layers 104, 106 from which the mobile element 111 is suspended by means of the first suspension means 121 formed on each side of the mobile element 111.

[0119] The different embodiment variants described for the previous embodiments can be applied to the micro-device 100 shown in the figure 10 .

[0120] As a variant of the micro-device 100 shown in the figure 10, it is possible that the first mobile element 111 is a geometry close or similar to that of the first mobile element 111 of the micro-device 100 previously described in connection with the figure 1 .

[0121] For the production of the micro-device 100 shown in the figure 10 , a method similar to one of those previously described may be implemented, in which the steps implemented realize a single moving element.

[0122] The micro-device 100 according to another embodiment different from those previously described is represented schematically according to two different views on the Figures 11A and 11B .

[0123] In this other embodiment shown in the Figures 11A and 11B, the micro-device 100 comprises the two mobile elements 111, 113. The first mobile element 111 is formed by the first portion 112 of the first layer 104 and the second portions 118 of the second layer 106. The second mobile element 113 is formed by the first portion 114 of the first layer 104 and the second portions 126 of the first layer 104.

[0124] In this micro-device 100, the first and second movable elements 111, 113 form movable masses capable of moving relative to the fixed part 115 of the micro-device 100 and also relative to each other. As previously, the fixed part 115 comprises the portions 117, 119 of the first and second layers 104, 106 from which the movable elements 111, 113 are suspended by means of first and second suspension means 121, 123 respectively.

[0125] In this embodiment, the two movable elements 111, 113 are arranged in a nested manner relative to each other.

[0126] Furthermore, in the configuration shown in the Figures 11A and 11B , the centers of gravity of the first and second mobile elements 111, 113 are aligned one above the other along an axis substantially perpendicular to main faces of the first and second layers of material 104, 106.

[0127] A micro-device 100 according to another embodiment different from those previously described is shown in the figure 12 .

[0128] In this other embodiment, the first and second movable elements 111, 113 are made concentrically with respect to each other. Thus, on the figure 12, the first movable element 111 comprises portions 112, 118 of the layers 104, 106 which at least partially surround portions 117a, 119a of the layers 104, 106 which form a fixed part 115a from which the first movable element 111 is suspended by means of the first suspension means 121. The second movable element 113 is formed by portions 114, 126 of the layers 104, 106 arranged around the portions 112, 118 of the first movable element 111 such that the first movable element 111 is at least partially surrounded by the second movable element 113. The second movable element 113 is suspended from another fixed part 115b, formed by portions 117b, 119b arranged around the second movable element 113, by second suspension means 123.

[0129] Viewed from above, each of the movable elements 111, 113 may have a ring or crown shape. Furthermore, in the main plane of the layers 104, 106 (plane (X,Y)), the section of the rings or crowns formed by the movable elements 111, 113 may be circular or polygonal (square, hexagonal, etc.).

[0130] According to yet another alternative embodiment, the micro-device 100 may comprise the first mobile element 111 or the second mobile element 113 as described in one of the previous embodiments, and another mobile element which comprises one or more portions of materials from only one of the layers of material 104, 106 (unlike the previous embodiments described in which each mobile element comprises at least two portions of material from at least two distinct layers of material).

Claims

1. Microdevice (100) comprising at least: - a first layer of material (104), - a second layer of material (106), - a fixed portion (115, 302), - a first mobile element (111) comprising at least a first portion (112) of the first layer of material (104) and at least a second portion (118) of the second layer of material (106), - a second mobile element (113) comprising at least a first portion (114) of the second layer of material (106) and at least a second portion (126) of the first layer of material (104), - first suspension means (121) formed in the first layer of material (104) and / or in the second layer of material (106), - second suspension means (123) formed in the first layer of material (104) and / or in the second layer of material (106), and wherein: - the first and second mobile elements (111, 113) are capable of moving with respect to one another and with respect to the fixed portion (115, 302), - the first and second layers of material (104, 106) are arranged one above the other, - the first portion (112) of the first layer of material (104) is rigidly connected to the second portion (118) of the second layer of material (106), - the first mobile element (111) is suspended from the fixed portion (115, 302) by the first suspension means (121), - the second mobile element (113) is suspended from the fixed portion (115, 302) by the second suspension means (123), - the first portion (114) of the second layer of material (106) is rigidly connected to the second portion (126) of the first layer of material (104), characterized in that: the first and second mobile elements (111, 113) are capable of moving substantially in phase opposition with respect to one another when the device is subjected to an external force, - the centres of gravity of the first and second mobile elements (111, 113) are aligned one above the other according to an axis substantially perpendicular to main faces of the first and second layers of material (104, 106).

2. Microdevice (100) according to claim 1, wherein the first and second mobile elements (111, 113) are arranged in an interlocking and / or concentric manner with respect to one another.

3. Microdevice (100) according to one of the previous claims, wherein the first portion (112) of the first layer of material (104) is connected to the second portion (118) of the second layer of material (106) by means of at least a first portion (120) of an intermediate layer (110) arranged between the first and second layers of material (104, 106), and / or wherein the first portion (114) of the second layer of material (106) is connected to the second portion (126) of the first layer of material (104) by means of at least a second portion (128) of the intermediate layer (110).

4. Microdevice (100) according to one of the previous claims, further comprising elements for detection and / or measurement of a movement of the first mobile element (111) and / or of the second mobile element (113) with respect to the fixed portion (115, 302) and / or of a movement of the first mobile element (111) with respect to the second mobile element (113), and / or elements capable of moving the first mobile element (111) and / or the second mobile element (113) with respect to the fixed portion (115, 302) and / or moving the first mobile element (111) with respect to the second mobile element (113).

5. Microdevice (100) according to one of the previous claims, wherein the first mobile element (111) and / or the second mobile element (113) are capable of moving in translation and / or in rotation with respect to the fixed portion (115, 302) and / or with respect to one another.

6. Microdevice (100) according to one of the previous claims, wherein the fixed portion (115, 302) comprises portions (117, 119) of the first and second layers of material (104, 106) arranged around the first and second mobile elements (111, 113) and / or surrounded by the first and second mobile elements (111, 113).

7. Microdevice (100) according to one of the previous claims, wherein the fixed portion (115, 302) comprises a support layer (102) such that the first layer of material (104) is arranged between the support layer (102) and the second layer of material (106).

8. Microdevice (100) according to one of the previous claims, further comprising at least one intermediate mobile element (304) suspended from the fixed portion (302) and capable of moving with respect to the fixed portion (302), and wherein the first and second mobile elements (111, 113) are suspended from the intermediate mobile element (304) and capable of moving with respect to the intermediate mobile element (304) and the fixed portion (302).

9. Microdevice (100) according to claim 8, wherein: - the fixed portion (302) comprises a fixed frame at least partially surrounding the intermediate mobile element (304), and the intermediate mobile element (304) forms a mobile frame suspended from the fixed frame, and / or - the microdevice (100) further comprises a first cavity (326), at least a portion of the walls of which is formed by the fixed portion (302) and in which the intermediate mobile element (304) is encapsulated, and a second cavity (324) arranged in the first cavity (326), at least a portion of the walls of which is formed by the intermediate mobile element (304) and in which the first and second mobile elements (111, 113) are encapsulated.

10. Method for fabricating a microdevice (100), comprising at least: - etching of a first layer of material (104) such that at least a first portion (112) of the first layer of material (104) forms a first portion of at least a first mobile element (111) and at least a second portion (126) of the first layer of material (104) forms a first portion of at least a second mobile element (113), - fabrication of a second layer of material (106) on the first layer of material (104), - etching of the second layer of material (106) such that at least a second portion (118) of the second layer of material (106) forms a second portion of the first mobile element (111) and is rigidly connected to the first portion (112) of the first layer of material (104) and at least a first portion (114) of the second layer of material (106) forms a second portion of the second mobile element (113) and is rigidly connected to the second portion (126) of the first layer of material (104), these steps being implemented such that: - the first mobile element (111) is suspended from a fixed portion (115, 302) by first suspension means (121) formed in the first layer of material (104) and / or in the second layer of material (106), - the second mobile element (113) is suspended from the fixed portion (115, 302) by second suspension means (123) formed in the first layer of material (103) and / or in the second layer of material (106), - the first and second mobile elements (111, 113) are capable of moving with respect to one another and with respect to the fixed portion (115, 302), characterized in that: the first and second mobile elements (111, 113) are capable of moving substantially in phase opposition with respect to one another when the device is subjected to an external force, - the centres of gravity of the first and second mobile elements (111, 113) are aligned one above the other according to an axis substantially perpendicular to main faces of the first and second layers of material (104, 106).

11. Method according to claim 10, wherein the fabrication of the second layer of material (106) on the first layer of material (104) comprises a transfer of the second layer of material (106) onto the first layer of material (104) such that an intermediate layer (110) is arranged between the first and second layers of material (104, 106), the method further comprising, after the etching of the second layer of material (106), an etching of the intermediate layer (110) such that at least a first portion (120) of the intermediate layer (110) connects the first portion (112) of the first layer of material (104) to the second portion (118) of the second layer of material (106) and, when the second mobile element (113) is made, at least a second portion (128) of the intermediate layer (110) connects the first portion (114) of the second layer of material (106) to the second portion (118) of the first layer of material (104).

12. Method according to one of claims 10 and 11, wherein a sacrificial layer (108) is arranged between the first layer of material (104) and a support layer (102), the method further comprising, after the etching of the second layer of material (106), the fabrication of an access (154) to the sacrificial layer (108) through the support layer (102) then an etching of a portion of the sacrificial layer (108) via the access (154) formed through the support layer (102), releasing at least the first portion (112) of the first layer of material (104) with respect to the support layer (102).

13. Method according to one of claims 10 and 11, wherein a sacrificial layer (108) is arranged between the first layer of material (104) and a support layer (102), the method further comprising, between the etching of the first layer of material (104) and the fabrication of the second layer of material (106), an etching of a first portion of the sacrificial layer (108) partially releasing at least the first portion (112) of the first layer of material (104) with respect to the support layer (102), and after the etching of the second layer of material (106), an etching of a second portion of the sacrificial layer (108) via openings (140, 152) formed through the first and second layers of material (104, 106) during the previous etchings of the first and second layers of material (104, 106), completing the releasing of the first portion (112) of the first layer of material (104) with respect to the support layer (102).

14. Method according to claim 13, wherein the steps of etching of the first and second layers of material (104, 106) form releasing holes (140, 152) passing through the first and second layers of material (104, 106) and which are aligned above each other.

15. Method according to claim 14, wherein the step of etching of the second layer of material (106) forms additional releasing holes (162) passing through the second layer of material (106).

16. Method according to one of claims 10 to 15, wherein the steps of etching of the first and second layers of material (104, 106) are implemented while using the same system of alignment marks arranged at a rear surface of a support (102) of the first and second layers of material (104, 106).