Magnetically actuated reflector device, and associated method

Abstract

Title: Magnetically Actuated Reflector Device and Associated Method. The invention relates to a reflector device (1) comprising: a substrate (S), a mirror (10) configured to be pivoted about at least one axis of rotation (A1), an actuator module (6) comprising at least one magnet (20) and at least one electrical line (30) configured to carry an electric current (i), the actuator module (6) being configured to rotate the mirror (10) by a driving force (FL), wherein the at least one magnet (20) comprises a stack (2) of at least one bilayer comprising a first sublayer (3) based on an antiferromagnetic material and a second sublayer (4) based on a ferromagnetic material. The invention also relates to the method of manufacturing the reflector device (1) in which the at least one magnet (20) is formed by depositing the stack (2) onto the substrate (S). Figure for the summary: Fig.1

Description

Title of the invention: Magnetically actuated reflector device, and associated method. Technical field

[0001] The present invention relates to the field of reflective devices for reflecting an incident light beam towards a target. It finds particularly advantageous application in the field of MEMS (microelectromechanical systems) micromirrors, notably for LIDAR (Light Detection and Ranging) and imaging applications, for example in pico-projectors. PRIOR TECHNOLOGY

[0002] Reflecting devices are used in many applications where the aim is to reflect an incident light beam towards a given target.

[0003] To achieve this, an incident light beam is emitted from a source towards the reflecting device having a mirror. The mirror has a front face arranged to receive the incident light beam. The mirror is oriented with the source so as to form a reflected beam in the direction of the target.

[0004] For example, MEMS micromirrors are commonly used for LIDAR or projection applications. These micromirrors may include an actuator module configured to rotate the micromirror around at least one axis of rotation. The actuation of the micromirrors may be electrostatic, magnetic, or piezoelectric.

[0005] Magnetic actuation of micromirrors is the most widespread. In particular, it has the advantage of being linear at low frequencies and offers a large travel at low voltage.

[0006] Reflecting devices comprising a magnetic actuation module are conventionally manufactured by the heterogeneous assembly of a permanent solid magnet with a micromirror mechanically coupled to a coil. In these solutions, the solid magnet is therefore attached to the substrate, for example by gluing. Integrating such a magnet into the reflecting device requires additional manufacturing steps that can be complex and costly. Moreover, its large size makes the device bulky and increases the energy consumption required to actuate the micromirror.

[0007] An object of the present invention is therefore to provide an improved solution for a magnetically actuated reflector device. An objective of the present invention may, in particular, be to provide a magnetically actuated reflector device, simplified manufacturing. One objective of the present invention may in particular be to provide a magnetically actuated reflector device with improved compactness.

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

[0009] To achieve this objective, according to one embodiment, a reflector device is provided for reflecting an incident light beam comprising: • a substrate comprising a first part, and a second part movable relative to the first part around at least one axis of rotation, • a mirror fixedly to the second part of the substrate, the mirror being configured so as to be pivoted around at least one axis of rotation and so as to receive the incident light beam to form a reflected beam, • an actuator module comprising at least one magnet and at least one electrical line configured to carry an electric current (i), the at least one electrical line being based on an electrically conductive material, the actuator module being configured to drive the second part of the substrate and the mirror in rotation by a driving force generated by an interaction between the at least one magnet and the electric current flowing through the at least one electrical line, one of at least one magnet and at least one electrical line being disposed on the first part of the substrate, the other of at least one magnet and at least one electrical line being disposed on the second part of the substrate, and the at least one magnet comprising a stack of at least one bilayer comprising a first sublayer based on an antiferromagnetic material and a second sublayer based on a ferromagnetic material, the stack being magnetized along at least one direction of magnetization.

[0010] The mirror's movement is thus driven by the Laplace force generated between the electric line, also called the coil, and the magnet. Since the magnet comprises a stack of sublayers based on alternating ferromagnetic and antiferromagnetic materials, it can be deposited using microelectronic deposition techniques, instead of requiring heterogeneous assembly. As detailed in the reference to the process, the homogeneous integration of these different components simplifies and reduces the manufacturing costs of the reflector device. Additional heterogeneous assembly steps, which are complex and expensive, can be avoided. Furthermore, the device's performance can be improved by this homogeneous integration, limiting the risk of magnet defects. or more generally of the device induced by heterogeneous integration. The mirror actuation is thus made more reliable. Furthermore, the magnet can therefore have reduced dimensions, and in particular thickness, compared to existing solutions. This thickness can typically be on the order of microns. The compactness of the device is thus improved.

[0011] A second aspect of the invention relates to a method for manufacturing a reflective device, the method comprising: • the supply of a substrate, • Formation of the actuator module on the upper surface of the substrate, the formation comprising: • a deposit on the upper surface of the substrate of a stack of at least one bilayer comprising a first sublayer based on an antiferromagnetic material and a second sublayer based on a ferromagnetic material, superimposed on the first sublayer, • a heat treatment of the deposited stack under the application of a magnetic field so as to magnetize the stack along at least one direction of magnetization, • a deposit of an electrically conductive material on the upper surface of the substrate, so as to form at least one electrical line, • the application of a mirror to the upper surface of the substrate, • at least one etching of the substrate so as to form a first part and a second movable part relative to the first part around at least one axis of rotation, the deposits and the etching being configured together so that the mirror is deposited on the second part of the substrate, one of at least one magnet and at least one electric line is disposed on the first part of the substrate, the other of at least one magnet and at least one electric line is disposed on the second part of the substrate.

[0012] The basic building blocks of a magnetically actuated reflector device are thus formed on the substrate using microelectronic deposition techniques, instead of being applied heterogeneously: the power line, the mirror, and the magnet formed by deposition on the substrate. This monolithic and collective integration of these different building blocks simplifies the manufacturing of the reflector device by avoiding additional heterogeneous assembly steps that can be complex and costly. Manufacturing costs are thus limited. Monolithic integration also significantly reduces the distance between the magnet and the power line. This significant reduction in the distance between the magnet and the line Electrical engineering would prove complex in manufacturing the actuator module by individually transferring magnets. Monolithic integration also allows for improved performance of the reflector device, notably by circumventing the mechanical constraints that can be imposed by a heterogeneous assembly. BRIEF DESCRIPTION OF THE FIGURES

[0013] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0014] [Fig.1] Fig.1 schematically illustrates a magnetically actuated reflector device in an orthonormal frame, comprising the X, Y, Z axes, according to an example of an embodiment.

[0015] [Fig.2A][Fig.2B] Figures 2A and 2B schematically illustrate according to YZ cross-sections a magnet comprising a stack of bilayers based on antiferromagnetic and ferromagnetic materials, manufactured by deposition according to the present invention, according to an embodiment.

[0016] [Fig.3][Fig.4][Fig.5A][Fig.6A][Fig.7A] Figures 3, 4, 5A, 6A and 7A illustrate schematically along an XY plane, top views of different examples of embodiments of the reflector device, according to several embodiments of the present invention.

[0017] [Fig.5B][Fig.6B][Fig.7B] Figures 5B, 6B and 7B schematically illustrate, according to XZ or YZ cross-sections, the different examples of realization of the reflector device illustrated in Figures 5A, 6A and 7A.

[0018] [Fig.8A] Fig.8A schematically illustrates, along an XY plane, a top view of the reflector device, according to another embodiment of the present invention.

[0019] [Fig.8B] Fig.8B schematically illustrates, according to a YZ cross-section, the reflector device illustrated in [Fig.8A].

[0020] [Fig.9A][Fig.1OA] Figures 9A and 10A schematically illustrate, along an XY plane, two examples of configurations of the actuator module of the reflector device according to the present invention.

[0021] [Fig.9B][Fig.1OB] Figures 9B and 10B represent graphs of the magnetic field produced by at least one magnet as a function of a distance g between at least one magnet and the electric line, obtained by calculations carried out for each of the two configurations illustrated in Figures 9A and 10A respectively.

[0022] [Fig.llA][Fig.l2A][Fig.l3A][Fig.l4A] Figures 11A, 12A, 13A and 14A schematically illustrate, in an XY plane, top views of the different stages of the manufacturing process of the reflector device, according to an embodiment of the present invention.

[0023] [Fig.llB][Fig.l2B][Fig.l3B][Fig.l4B] Figures 11B, 12B, 13B and 14B schematically illustrate, according to XZ or YZ cross-sections, the different stages of the manufacturing process of the reflector device, according to an embodiment of the present invention.

[0024] [Fig.15A][Fig.15B][Fig.15C][Fig.15D] Figures 15A, 15B, 15C and 15D schematically illustrate, according to YZ cross-sections, the manufacturing steps of an actuator module according to a first example.

[0025] [Fig.l6A][Fig.l6B][Fig.l6C][Fig.l6D][Fig.l6E][Fig.l6F] Figures 16A to 16F schematically illustrate, according to YZ cross-sections, the manufacturing steps of an actuator module according to a second example.

[0026] [Fig. 17A] [Fig. 17B] [Fig. 17C] [Fig. 17D] [Fig. 17E] [Fig. 17F] [Fig. 17G] [Fig. 17H] [Fig. 171] Figures 17A to 171 schematically illustrate, according to YZ cross-sections, the manufacturing steps of an actuator module according to a third example.

[0027] On the cross-sectional figures, cutting planes are indicated (A-A', B-B',..., N-N') with cross references to the cutting planes of the corresponding figures.

[0028] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of the principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, in the schematic diagrams, the thicknesses and / or dimensions of the different layers, patterns and reliefs are not representative of reality. DETAILED DESCRIPTION

[0029] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in association or alternatively are stated below.

[0030] According to one example, the first and second sublayers are superimposed. More particularly, the second sublayer based on a ferromagnetic material can be superimposed on the first sublayer based on an antiferromagnetic material.

[0031] According to one example, at least one magnet is attached to the substrate without the use of an adhesive material or mechanical fastening or welding.

[0032] The magnet is integrated into the reflector device in a homogeneous and monolithic manner, that is, without the use of assembly processes such as welding, mechanical fastening, or the use of an adhesive material. This homogeneous and monolithic integration improves the compactness of the reflector device and facilitates its manufacture.

[0033] According to one example, the magnet is in direct contact with the substrate, and preferably without an interface of glue.

[0034] According to an example, at least one magnetization direction (M) is in the main extension plane of the stack, and for example of the bilayer.

[0035] According to one example, at least one magnet and at least one power line are separated by a distance g, the shortest distance between the at least one magnet and the at least one power line, the distance g being greater than or equal to 500 nm. According to one example, the distance g is less than or equal to 7 pm, preferably less than or equal to 5 pm.

[0036] The distance g separating the magnet and the power line is a parameter that has a significant impact on the intensity of the driving force FL. The closer the magnets and the power line are, the greater the Laplace force FL. Reducing the distance g makes it easier to magnetically actuation the mirror. This therefore reduces the energy consumption required to actuation the mirror.

[0037] According to one example, the second sublayer based on a ferromagnetic material has a thickness e4 between 2 nm and 50 nm, preferably between 10 nm and 50 nm.

[0038] According to one example, the first sublayer based on an antiferromagnetic material has a thickness e3 between 5nm and 50 nm, preferably between 5 nm and 30 nm.

[0039] The thicknesses e3 and e4 can be advantageously optimized for each pair of ferromagnetic and antiferromagnetic materials. Preferably, the thickness e3 of the sublayers based on an antiferromagnetic material is minimized, and the thickness e4 of the sublayers based on a ferromagnetic material is maximized, while maintaining significant exchange interaction between the two materials. For example, for a PtMn-based antiferromagnetic material, the thickness e3 is preferably chosen to be around 20 nm, preferably around 12 nm, and the thickness e4 of the ferromagnetic sublayers can be around 20 nm. According to another example, for an antiferromagnetic material based on IrMn, the thickness e3 is preferably chosen around 8 nm, preferably around 5 nm, and the thickness e4 of the ferromagnetic sublayers can be chosen around 20 nm.According to another example, for an antiferromagnetic material based on NiMn, the thickness e3 is preferably chosen around 50 nm, and the thickness e4 of the ferromagnetic sublayers can be chosen around 50 nm.

[0040] According to one example, the stack of at least one magnet has a thickness between 700 nm and 5 pm, preferably between 900 nm and 2 pm, and even more preferably equal to 1 pm.

[0041] The effective magnetic thickness of the magnet is the sum of the thicknesses of all the ferromagnetic sublayers. Indeed, the antiferromagnetic material exhibits substantially compensated magnetic moments, and consequently, does not produce a magnetic field, or produces an extremely weak magnetic field. It is primarily the magnetic moments present in the ferromagnetic material that contribute to the effective magnetization of the magnet. The effective magnetic thickness can be substantially between 350 nm and 2.5 pm, preferably between 450 nm and 1 pm, and even more preferably can be substantially equal to 0.5 pm, depending on the number of ferromagnetic sublayers.

[0042] According to one example, the stacking of at least one magnet comprises N superimposed bilayers, N being an integer between 10 and 50.

[0043] The number N of bilayers determines the total thickness as well as the effective magnetization of the magnet.

[0044] According to one example, the width of the magnet is on the order of 200 pm.

[0045] According to one example, the length of the magnet is on the order of 5 mm.

[0046] The reduced dimensions of the magnet make it possible to decrease the size of the device and to reduce the energy consumption of the reflector device.

[0047] According to one example, the actuator module is configured so that two driving forces are exerted on the second moving part of the substrate, said forces being in opposite directions to each other.

[0048] According to one example, the actuator module comprising at least two magnets, at least one electrical line being disposed on the second movable part of the substrate in a manner fixed to the mirror, the at least two magnets being respectively disposed on the first part on either side of at least one electrical line with respect to the axis of rotation of the mirror.

[0049] According to one example, the actuator module comprising at least two electrical lines, at least one magnet being disposed on the second movable part of the substrate in a manner fixed to the mirror, the at least two electrical lines being respectively disposed on the first part of the substrate on either side of at least one magnet with respect to the axis of rotation of the mirror.

[0050] These two configurations allow the generation of two Laplace forces which will act in two opposite directions on either side of the second moving part of the substrate, to facilitate the rotation of the mirror.

[0051] The configuration in which the power line is arranged on the second moving part of the substrate has the advantage of reducing the weight of the moving part and facilitating the rotation of this moving part.

[0052] According to one example, the actuator module comprises at least two magnets, at least one electrical line being disposed on the second movable part of the substrate in a manner fixed to the mirror, the at least two magnets being respectively disposed on the first part on either side of the at least one electrical line with respect to the axis of rotation of the mirror, in which the second movable part of the substrate presents a recess around which at least one electrical line forms a loop, the reflector device further comprising a third magnet attached to the first part of the substrate and disposed in the recess.

[0053] The recess in the second moving part reduces the weight of the moving part and facilitates its rotation. The addition of a magnet increases the intensity of the Laplace forces generated, further facilitating the rotation of the mirror.

[0054] According to one example, the mirror surmounts one of at least one magnet and at least one electric line.

[0055] Integrating the magnet or the electrical line below the mirror allows for optimization of the device's compactness.

[0056] According to one example, the mirror includes a metallic reflective layer, preferably based on gold (Au) or aluminum (Al).

[0057] According to one example, the mirror includes a Bragg stacking.

[0058] According to one example, the at least one magnet comprises a plurality of sub-magnets juxtaposed with each other, each sub-magnet being in the shape of a bar and comprising the stacking of at least one bilayer.

[0059] Dividing the magnet into sub-magnets in the form of parallel bars, so that each bar has a significant length-to-width ratio, allows for good alignment of the magnetic moments along the principal direction of the bar extension.

[0060] Due to the elongated shape of the bars, the magnetization can naturally align itself along their principal directions, that is, the direction in which their length is measured, during the manufacture of the magnet and, more specifically, during magnetic annealing. The orientation of the magnetization direction is thus made more reliable, which in turn makes the actuation of the mirror more reliable. This can be particularly advantageous for manufacturing sub-magnets with two distinct magnetization directions.

[0061] According to one example, the sub-magnets form a matrix in at least one dimension, by being juxtaposed along a direction perpendicular to their principal extension direction and parallel to the principal extension plane of the substrate.

[0062] According to one example, the sub-magnets have distinct magnetization directions (M) between them.

[0063] Thus, Laplace forces can be generated in different directions. This can, in particular, make it possible to rotate the mirror around two axes of rotation.

[0064] According to one example, the sub-magnets are separated by a non-magnetic material, preferably based on silicon oxide (SiO2).

[0065] According to one example, the at least one magnet comprises a plurality of superimposed sub-magnet arrays, arranged in a direction normal to the principal extension direction of the stack or, equivalently, of the substrate. The superposition of the bar magnet arrays along the same direction increases the effective magnetization of the magnet.

[0066] According to one example, the electrically conductive material is based on a metal, such as aluminium or copper, preferably copper-based.

[0067] According to one example, the power line is connected to a power supply source.

[0068] This source allows the line or the electric coil to be supplied with a current which interacts with the magnetic field emanating from the magnet to generate a Laplace force FL called driving force whose direction depends on the direction of the electric current and the direction of the magnetization of the magnet.

[0069] According to one example, the ferromagnetic material is based on CoFe, and the antiferromagnetic material is based on PtMn or IrMn.

[0070] The choice of these ferromagnetic and antiferromagnetic material pairs allows, on the one hand, for improved saturation magnetization Ms in the principal extension plane of the bilayer, which improves the generation of the driving force FL. On the other hand, it simplifies the integration of the magnet, for example by physical vapor deposition (PVD).

[0071] According to one example, the CoFe composition of the ferromagnetic material is richer in cobalt (Co) than in iron (Fe).

[0072] This improves the exchange interaction between the two ferromagnetic and antiferromagnetic materials, and consequently, improves the magnet's resistance to magnetic shocks. On the other hand, this tends to decrease the saturation magnetization Ms.

[0073] According to one example, the CoFe composition of the ferromagnetic material is richer in iron (Fe) than in cobalt (Co).

[0074] This allows the saturation magnetization Ms to be increased. On the other hand, this tends to decrease the exchange interaction between the two ferromagnetic and antiferromagnetic materials.

[0075] According to one example, the heat treatment of the stack is carried out at a temperature greater than or equal to 265°C for an antiferromagnetic material based on IrMn.

[0076] According to one example, the heat treatment of the stack is carried out at a temperature greater than or equal to 290°C for an antiferromagnetic material based on PtMn.

[0077] According to one example, the heat treatment of the stack is carried out for a period greater than or equal to 1 hour.

[0078] The heat treatment is often carried out at a temperature above the blocking temperature of the bilayer, above which the exchange interaction between the antiferromagnetic and ferromagnetic sublayers disappears. This allows the magnetic moments in the ferromagnetic material to be reoriented along the direction of the applied external magnetic field. After the heat treatment and cooling of the magnet to a temperature below the blocking temperature, the exchange interaction is re-established, and the magnetic moments in the ferromagnetic material are fixed in the desired direction, which preferably lies in the principal extension plane of the bilayer.

[0079] According to one example, the heat treatment is carried out under the application of a magnetic field having a direction which makes an angle of 45° with the main extension direction of the sub-magnets.

[0080] This makes it possible to obtain at the end of the heat treatment two perpendicular magnetization directions, which makes it possible to actuate a rotation of the mirror along two axes of rotation.

[0081] According to one example, the intensity of the magnetic field applied during at least part of the heat treatment, and according to another example during the entire heat treatment, is greater than or equal to 1 T.

[0082] According to one example, the formation of the actuator module further comprises: • an engraving of the deposited stack so as to form two first distinct magnets, separated by a space exposing the inner flanks of the first two magnets and the upper face of the substrate,

[0083] According to one example, the formation of the actuator module further comprises: • a deposit of a layer of resin on the first two magnets so as to cover the surface and the inner sides of the first two magnets and to define a pattern intended for the formation of at least one electric line between the first two magnets, • the deposition of the electrically conductive material in the pattern defined in the previous step, to form at least one electrical line, • a shrinkage of the resin layer after the deposition of the electrically conductive material.

[0084] According to one example, the formation of the actuator module further comprises: • the deposition of a layer of electrically conductive material on the first two magnets so as to cover at least the surface of the first two magnets, and to fill at least partially, and preferably completely, the space between the first two magnets, • an engraving of the layer of electrically conductive material between the first two magnets so as to form two trenches in the layer of electrically conductive material delimiting an electrical line separate from the two magnets, preferably without exposing the inner sides of the first two magnets.

[0085] According to one example, the formation of the actuator module further comprises: • a deposit of a first layer of oxide on the first two magnets so as to cover the surface and sides of the first two magnets, and to fill at least partially, and preferably completely, the space between the first two magnets, • a partial engraving of the first oxide layer directly above the space between the first two magnets, substantially up to the plane comprising the upper face of the first two magnets, in order to form a pattern intended for the formation of at least one electric line, • the deposition of a layer of electrically conductive material on the first oxide layer in order to fill at least partially, and preferably completely, the pattern defined in the previous step, to form at least one electrical line, • a planarization of the layer of electrically conductive material until substantially reaching the first oxide layer, • the formation of two distinct secondary magnets above the first oxide layer and directly above the first two magnets, • a deposit of a second layer of oxide so as to cover the surface and sides of the two second magnets, and to fill at least in part, and preferably entirely, the space between the two second magnets.

[0086] According to one example, the second oxide layer is planarized so as to expose the upper face of the two second magnets.

[0087] According to one example, the deposition of the first oxide layer is followed by the following steps: • an etching of the first oxide layer between the first two magnets so as to expose the underlying substrate, and preferably expose the inner flanks of the first two magnets, • a layer of resin is deposited on the first magnets to define a pattern between the first two magnets, separated from the inner flanks of the two first magnets, intended for the formation of at least one power line, for example the resin layer deposited on the first magnets is configured to cover at least the inner sides of the first two magnets, and • the deposition of the electrically conductive material in the pattern defined in the previous step, to form at least one electrical line, • a shrinkage of the resin layer, • a deposit of a second layer of oxide so as to fill at least in part, and preferably entirely, the space between the at least one electrical line formed and the two second magnets.

[0088] According to one example, the deposition of the first oxide layer is followed by the following steps: • a partial etching of the first oxide layer between the first two magnets so as to expose at least part of the upper face of the substrate, without exposing the inner sides of the first two magnets, and to define a pattern intended for the formation of at least one electric line, • the deposition of the electrically conductive material in the pattern defined in the previous step, to form at least one electrical line, • a planarization of the layer of electrically conductive material, preferably without exposing the upper face of the first two magnets, • a deposit of a second layer of oxide so as to cover the first two magnets and at least one electrical line.

[0089] It is specified that, within the framework of the present invention, the terms "on", "overcomes", "covers", "underlying", "opposite" and their equivalents do not necessarily mean "in contact with". Thus, for example, the arrangement of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means 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.

[0090] A substrate is understood to be a layer based on a species A, a substrate, a layer comprising only that species A or that species A and possibly other species.

[0091] A parameter "approximately equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, to within ±10% of that value. A parameter "approximately between" two given values ​​means that this parameter is at least equal to the smaller of the two values. given value, plus or minus 10%, close to that value, and at most equal to the largest given value, plus or minus 10%, close to that value.

[0092] A frame of reference, preferably orthonormal, comprising the X, Y, Z axes is represented in the attached figures.

[0093] It is specified that, within the framework of the present invention, the thickness of a layer or substrate is measured along a direction perpendicular to the surface along which this layer or substrate has its maximum extent. The thickness is thus taken along a direction perpendicular to the principal faces of the layer or substrate on which the different layers rest. More particularly, the thickness can be taken along the Z direction.

[0094] In this patent application, the term "fixed" used to describe the connection between two parts means that the two parts are linked / fixed to each other with respect to all degrees of freedom, unless explicitly specified otherwise. For example, if it is stated that two parts are fixed in translation along a direction X, this means that the parts can be movable relative to each other, possibly with respect to several degrees of freedom, excluding freedom in translation along the direction X. In other words, if one part is moved along the direction X, the other part moves in the same direction.

[0095] In the detailed description that follows, terms such as "horizontal", "vertical", "longitudinal", "transverse", "superior", "inferior", "high", "low", "front", "rear", "interior", and "exterior" may be used. These terms must be interpreted in a relative manner with respect to the normal position of the reflecting device and the propagation of light beams, and in particular the incident light beam, relative to the reflecting device.

[0096] The steps of the process are understood in the broad sense as the execution of a part of the process and may optionally be carried out in several sub-steps. Several embodiments of the invention implementing successive steps of the manufacturing process are described below. Unless explicitly stated, the adjective "successive" does not necessarily imply, although this is generally preferred, that the steps follow one another immediately; intermediate steps may separate them.

[0097] Furthermore, the term "step" does not necessarily mean that the actions carried out during a step are simultaneous or immediately successive. Certain actions of a first step may, in particular, be followed by actions related to a different step, and other actions from the first step may be repeated later. Thus, the term "step" does not necessarily imply unitary actions that are inseparable in time and in the sequence of phases of the process.

[0098] In the context of the present invention, a resin is classically defined as an organic or organo-mineral material that can be shaped by exposure to a beam of electrons, photons or X-rays or mechanically.

[0099] Examples of resins commonly used in microelectronics include polystyrene (PS), methacrylate (e.g., Polymethyl methacrylate PMMA), hydrosilsesquioxane (HSQ), polyhydroxystyrene (PHS), etc. The advantage of using a resin is that it is easy to deposit a significant thickness, from several hundred nanometers to several micrometers.

[0100] A reflector device 1 is now described with reference to Figures 1, 2A and 2B, according to an example embodiment.

[0101] Figure 1 illustrates a magnetically actuated reflector device 1 for reflecting an incident light beam to form a reflected beam propagating in a predetermined direction, typically towards a target. The reflector device 1 comprises a substrate S extending, for example, in an XY plane defined by a direction X and a direction Y perpendicular to the direction X. The substrate S comprises a first portion S1 and a second portion S2 movable relative to the first portion S1

[0102] A mirror 10, which receives the incident beam and forms the reflected beam, is fixedly attached to the second part S2 of the substrate S. The mirror 10 is configured to be pivoted about at least one axis of rotation AL. The axis of rotation Al is defined, for example, by the length of the second movable part S2, which extends along the X direction on either side of the mirror 10 to join the first part SL.

[0103] The reflector device 1, for example illustrated in [Fig.1], may include at least one actuator module 6. Each actuator module 6 includes at least one magnet 20 having a magnetization direction M, and at least one electric line 30. The electric line 30 is based on an electrically conductive material 35 and is supplied by an electric current i.

[0104] The current i flowing through the electrical line 30 interacts with the magnetic field emanating from the magnet 20 to generate a Laplace force FL, called the "driving force." This driving force FL causes the second part S2, and therefore the mirror 10, to pivot around the axis of rotation AL. The direction of the driving force FL is typically substantially perpendicular to the direction of the magnetization M and to the direction of current i. Furthermore, the direction of the driving force FL depends on the orientation of the direction of the magnetization M as well as the direction of the current i. Since the direction of the magnetization M is preferably fixed, the direction of the driving force FL is determined by the direction of the current i passing through the electric line 30. It is therefore understood that the mirror 10 can be driven in rotation in one direction or in the opposite direction.

[0105] The mirror 10 thus moves from a rest position, i.e., an equilibrium position without magnetic actuation, to a pivoted position, by pivoting around the axis of rotation Al. Once the mirror 10 has been set in rotation, it can be returned to a rest position. This return to the rest position can be achieved by returning to the equilibrium position, by stopping the magnetic drive.

[0106] Typically, the second part S2 of the substrate is rotationally hinged to the first part SI by means of a hinge 5, and more particularly a torsionally deformable hinge 5 about the axis of rotation Al. Conventionally, this hinge 5 may include a portion of the substrate forming a torsionally deformable bar, connecting the first part SI and the second part S2 of the substrate. During magnetic actuation, this hinge 5 can be torsionally deformed about the axis of rotation Al to allow the rotation of the second part S2 of the substrate and thus of the mirror 10. When the driving force is no longer generated, the torsional force of the hinge 5 can cause the return to the equilibrium position.

[0107] Note that in the configuration of the reflector device 1 illustrated in [Fig. 1], two actuator modules 6 are shown. According to the illustrated example, the reflector device comprises two actuator modules 6 arranged on either side of the mirror 10 along a direction parallel to the axis of rotation Al of the mirror 10, so as to increase the resultant of the driving forces generated. The rotation of the mirror 10 is thus facilitated. The pivoting of the mirror 10 can nevertheless be driven by a single actuator module 6. For the sake of simplification and without limitation, only one actuator module 6 will be shown in the figures and embodiments described below.

[0108] As illustrated, for example, in Figures 2A and 2B, the magnet 20 comprises a stacking 2 of at least one bilayer along a direction Z perpendicular to the X and Y directions. Each bilayer comprises a first sublayer 3 based on, and preferably made of, an antiferromagnetic material, and a second sublayer 4 based on, and preferably made of, a ferromagnetic material. The superposition of a ferromagnetic material with an antiferromagnetic material gives rise to an exchange interaction between the magnetic moments at the interface between the first sublayers 3 and the second sublayers 4, which fixes the magnetic moments, particularly in the second ferromagnetic sublayers 4.

[0109] The second sublayer 4 can be superimposed on the first sublayer 3. Superimposing an antiferromagnetic material on a ferromagnetic material improves the resistance of the magnet 20 to magnetic shocks. The stacking 2 can understand N bilayers, N being an integer between 10 and 50. Figures 2A and 2B show an example with N=2.

[0110] The stack 2 is manufactured using microelectronic deposition techniques. This allows the magnet 20 to be integrated into the reflector device 1 by depositing the stack 2 onto the substrate S, homogeneously with the deposition of the mirror 10 and the electrical line 30 during the manufacturing process.

[0111] Following the deposition of the stack 2, the direction of the magnetization M can be defined during the process as will be described in detail later. This direction of the magnetization M is preferably taken in the XY plane, which makes it possible to generate a driving force FL along the Z direction.

[0112] The actuator module 6 described above, comprising at least one magnet 20 and at least one electrical line 30, can be configured in several ways. According to one example, the actuator module 6 is configured so that two driving forces are exerted on the second movable part S2 of the substrate, in opposite directions between the two opposite edges 7a, 7b, of the movable part S2 with respect to the axis of rotation AL. Thus, the rotation of the mirror 10 is facilitated.

[0113] To this end, according to a first embodiment, an electrical line 30 forming a loop or a coil is arranged on the second movable part S2, and two magnets 20 are arranged on the first part SI on either side of the movable part S2, in a direction perpendicular to the axis of rotation AL. Several variants of this first embodiment, which will be described initially, notably allow for improvement in the generation of the driving force FL and the compactness of the reflector device 1. According to a second embodiment, two electrical lines 30 are arranged on the first part SI, on either side of a magnet arranged on the movable part S2, in a direction perpendicular to the axis of rotation AL. This second embodiment will be described later in the following description.

[0114] Figure 3 illustrates a top view along the XY plane of a reflector device 1, according to the first embodiment of the present invention. The electrical line 30 can form a loop or a coil, such that the current i propagates in the electrical line 30 over a first part of the loop, located opposite an edge of the movable part S2. The current i thus propagates in a first direction relative to the reflector device. The current i can also propagate in the electrical line 30 over a second part of the loop, located opposite an edge, relative to the axis of rotation Al, of the movable part S2. The current i thus propagates in a second direction relative to the reflector device, opposite to the first. According to this first embodiment, the electrical line 30 can be arranged on the second movable part S2 of the substrate S, fixed to the mirror 10. Two magnets 20 having preferably the same magnetization direction M, can be arranged respectively on the first part SI on either side of the electric line 30 in a direction perpendicular to the rotation axis Al of the mirror 10. The current i interacts with the first magnet 20 of the first part of the loop to generate a driving force FL in the direction Z in a first direction, then interacts with the second magnet 20 of the second part of the loop to generate a driving force Fl in a second direction opposite to the first direction. These two opposing forces facilitate the rotation of the second mobile part S2. Reversing the direction of current i in the loop, with respect to the reflecting device, induces a reversal of the direction of the two driving forces, which allows the mirror 10 to pivot around the rotation axis Al in a positive or negative direction with respect to an axis perpendicular to the rotation axis AL La [Fig.3] illustrates an example of pivoting the mirror 10 around the axis of rotation Al defined along the X direction, in a negative direction of the Y direction.

[0115] The arrangement of the electrical line 30 on the second mobile part S2 further allows the weight of this second mobile part S2 to be reduced, which facilitates the rotation of the mirror 10. According to one example, the second mobile part S2 may advantageously have a recess 8 around which the electrical line 30 forms the loop, which further reduces the weight of the second mobile part S2.

[0116] According to a variant illustrated in [Fig. 4], each magnet 20 can comprise a plurality of sub-magnets 25 placed side by side. In this example, each sub-magnet 25 is bar-shaped and comprises the stack 2 of bilayers described previously. The sub-magnets 25 are more specifically placed side by side along the X direction, along a direction substantially perpendicular to their principal extension direction Y. This configuration ensures good alignment of the magnetic moments of the magnet 20 along the principal extension direction of the bar during manufacturing. Due to the elongated shape of the sub-magnets 25, the magnetization M can naturally align itself along their principal directions, i.e., the direction in which their length Ua is measured, during the manufacturing of the magnet 20, and more particularly during heat treatment.The orientation of the magnetization direction M is made reliable, which makes the actuation of the mirror 10 reliable. The sub-magnets 25 are preferably substantially parallel to each other, and each sub-magnet 25 advantageously has a significant aspect ratio with a length Ua along the Y direction, on a width Va along the Y direction, preferably Ua / Va>10. .

[0117] According to one embodiment, the sub-magnets 25 may have distinct magnetization directions M. Thus, Laplace forces FL may be generated in different directions. This can notably allow the rotation of mirror 10 along two different axes of rotation.

[0118] According to an example not shown, the sub-magnets 25 are separated by a non-magnetic material, preferably based on silicon dioxide (SiO2). This makes it possible to form an array of sub-magnets 25 which can be superimposed with a plurality of sub-magnet arrays 25. The superposition of the arrays of magnetized bars along the same magnetization direction M increases the effective magnetization of the magnet.

[0119] As illustrated in Figures 5A and 5B, by way of example, the reflector device 1 may further comprise a third magnet 20 attached to the first part SI of the substrate S and disposed in the recess 8. The addition of a third magnet 20 at the center of the electrical loop increases the intensity of the opposing Laplace forces FL generated, which further facilitates the rotation of the mirror 10. Calculation results performed as a function of different configurations of the actuator module 6 show the effect of adding a third magnet 20 on the intensity of the driving force Fl. These results will be presented later in this description.

[0120] Figures 6A and 6B illustrate an example of an embodiment that further improves the compactness of the reflector device 1. In this example, the dimensions of the second movable part S2 are reduced. Indeed, the recess 8 in this part extends to the vertical axis of the power line 30, as shown by cross-sections BB' and CC' along the YZ and XZ planes, respectively. This further reduces the weight of the second movable part S2, which facilitates the rotation of the mirror 10. It is understood that the dimensions of the components of the reflector device 1 can be adjusted according to the envisaged architectures.

[0121] As illustrated in Figures 7A and 7B, according to another example, the mirror 10 can be arranged in superposition with the power line 30 as shown in the cross-section DD' along the YZ plane. This improves the compactness of the reflector device 1.

[0122] Figures 8A and 8B illustrate an alternative embodiment of the present invention. According to this alternative, the magnet 20 is disposed on the second movable part S2 of the substrate S. The mirror 10 can more particularly be superimposed on the magnet 20, as shown in the cross-section FF' along the YZ plane. Two electrical lines 30 are disposed on either side of the magnet 20 with respect to the axis of rotation Al, on the first part SL. A current i flows in each of the electrical lines 30 on either side of the magnet 20, in opposite directions, so that the Laplace forces FL generated are in opposite directions.

[0123] We will now describe the parameters that influence the intensity of the Laplace force FL generated by the interaction between the current i and the magnetic field emanating from at least one magnet 20. As is known, the intensity of FL follows the following equation:

[0124] FL = Bxixl

[0125] Where B represents the intensity of the magnetic field produced by the magnet 20 at a distance g between the power line 30 and the magnet 20 taken along the Y direction, i represents the intensity of the current i flowing through the power line 30, and l represents the length of the interaction between the current i and the magnetic field, which preferably corresponds to the length of the magnet 20. The Laplace force FL depends on this distance g. In order to evaluate the influence of the distance g on the intensity of the force FL, calculations were performed for two different configurations, illustrated in Figures 9A and 10A.

[0126] Figure 9A illustrates a first configuration in which a single magnet 20 interacts with the loop-shaped power line 30. Calculations based on the parameters presented in the table below, with reference to Figure 9A, were performed. In the examples presented, in order to simulate a stack 2 comprising ferromagnetic sublayers with a saturation magnetization Ms of approximately 2.4 T and a thickness approximately equal to that of the antiferromagnetic sublayers, a permanent magnet with a saturation magnetization Ms of approximately 1.2 T replaces the stack 2 in the calculations.As an example, this permanent magnet can simulate a 2-layer stack of 25 bilayers, comprising PtMn-based antiferromagnetic sublayers each with a thickness of around 20 nm, and CoFe-based ferromagnetic sublayers with a composition of 65% Fe and 35% Co, for example, each with a thickness of around 20 nm. [Tables 1] Parameters Values ​​Number of magnets 1 Thickness of one magnet 1 µm Maximum intensity of the magnetic field generated by the magnet 1.2 T Width b of the magnet along the y direction 200 µm Length 1 of the magnet along the x direction 5 mm Number of power lines 1 Thickness r of the power line along the z direction 1 µm Dimension d of the power line along the y direction: 100 pm. Electric current intensity: 100 mA.

[0127] The calculation results show that most of these parameters have an impact proportional to their value on the intensity of the Laplace force FL. The thickness r of the power line 30 and the length 1 of the magnet 20 have a negligible impact on this intensity. On the other hand, these parameters r and 1 have an impact on the maximum current i supported by the power line 30, which defines the limit of electromigration in the power line. The distance ga, however, has a strong impact on the intensity of the driving force. The variation of the magnetic field B as a function of the distance g is shown in the graph in [Fig. 9B]. By increasing the distance g between the magnet 20 and the power line 30, the intensity of the magnetic field produced by the magnet 20 decreases exponentially. This drastic variation of the magnetic field intensity as a function of the distance g has a significant impact on the intensity of the Laplace force FL.The closer the magnet 20 and the power line 30 are, the greater the Laplace force FL, which facilitates the actuating of the mirror 10's pivoting action. Furthermore, this reduces energy consumption, because for a fixed current i, simply reducing the distance g increases the magnitude of the driving force FL. According to the graph in [Fig. 9B], to obtain a significant driving force FL, the distance g is preferably less than or equal to 7 pm, and preferably less than or equal to 5 pm. These reduced values ​​of the distance g are advantageously achievable through the monolithic integration of the magnet 20 and the power line 30. For a distance g of 5 pm, the calculated magnitude of the Laplace force FL is approximately 20.5 pN. In the case where two magnets 20 are placed on either side of the moving part S2, the sum of the forces in absolute value is therefore 41 pN.

[0128] Figure 1OA illustrates an example in which two magnets 20 interact with the current i flowing through the looped power line 30. The first magnet 20 is positioned outside the loop at a distance g from the power line 30. The second magnet 20 is positioned at the center of the loop at the same distance g from the power line 30, for example, in a recess 8 in the moving part S2 as described previously. Calculations based on the parameters presented in the table below, with reference to Figure 1OA, have been performed. [Tables 2] Parameters Values ​​Number of magnets 2 Thickness of one magnet 1 µm Total maximum intensity of magnetic fields generated by the magnets: 1.2 T. External magnet dimension (be) along the y-direction: 200 µm. External magnet dimension (b) along the y-direction: 100 µm. Magnet length (l) along the x-direction: 5 mm. Number of electrical lines: 1. Electrical line thickness (r) along the z-direction: 1 µm. Electrical line dimension (d) along the y-direction: 100 µm. Electrical current intensity: 100 mA.

[0129] The variation of the magnetic field B as a function of the distance g is shown in the graph in [Fig. 1OB]. This graph shows that for this configuration, in order to obtain a significant driving force FL, the distance g has a significant impact. Preferably, the distance g is less than or equal to 7 pm, preferably less than or equal to 5 pm. For a distance g equal to 5 pm, the magnitude of the force FL calculated for the same current intensity i as for the previous configuration is around 82 pN. This shows that by adding a magnet 20 inside the loop, the magnitude of the force FL is significantly increased. In the case where two magnets 20 are arranged on either side of the moving part S2, the resultant force is therefore 164 pN.

[0130] For each of the two embodiments described above, a set of dimensions for the second movable part S2 is shown in the tables below. Optimizing these dimensions allows for optimizing the rotational resonance frequency of mirror 10 and the maximum static displacement of mirror 10 relative to its equilibrium position.

[0131] According to the first embodiment and with reference to the example of the reflector device illustrated in Figures 6A and 6B, the second movable part S2 may comprise: - A support for the mirror 10 of a dimension Dm along the Y direction, - A support for power line 30 with a recess 8, a dimension La along the X direction, a section Wi along the X direction and a thickness Ts along the Z direction, - A hinge 5 connecting the support for the power line 30 to the first part SI of the substrate S, having a length Lh along the X direction and a width Wh along the Y direction, - Two bars separated from each other by a distance Wa along the Y direction, connecting the support of the electric line 30 to the support of the mirror 10, having a length Lb along the X direction.

[0132] The following table presents examples of values ​​for the dimensions mentioned above: [Tables3] Parameter Range of values ​​Optimal value wh 5 pm <Wh<20 pm 10 pm Wi 10 pm<Wh<100 pm 50 pm Lh 50 pm<Lh<1000 pm 500 pm La 500 pm<La<2000 pm 1000 pm Lb 10 pm<Lb<100 pm 50 pm Ts 5 pm<Ts<20 pm 11 pm Wa 500 pm<Wa<2000 pm 1500 pm

[0133] The optimal value of the dimension Dm depends on the optical specifications of the reflector device 1. For example, Dm can be equal to 2000 pm. As described previously, the intensity of the Laplace force FL depends on the parameters of the actuator module 6. For example, the intensity of FL can be equal to 50 pN. For the optimal values ​​of the parameters presented in the table above and for the example values ​​of Dm and FL given, the torsional resonance frequency is around 500 Hz, and the static displacement of the mirror from its equilibrium position is ±10°.

[0134] With reference to the example of the reflector device illustrated in Figures 8A and 8B, the second movable part S2 may comprise: - A support for mirror 10, of dimension Dm along the Y direction, with mirror 10 superimposed on magnet 20, - A hinge 5 connecting the support of the mirror 10 to the first part SI of the substrate S, having a length Lh along the X direction, a width Wh along the Y direction and a thickness ts along the Z direction.

[0135] The following table presents examples of values ​​for the dimensions mentioned above: [Tables 4] Parameter Range of values ​​Optimal value wh 5 pm <Wh<20 pm 10 pm Lh 50 pm<Lh<1000 pm 500 pm tS 5 pm< ts<20 pm 11 pm

[0136] For the optimal values ​​of the parameters presented in the table above and for Dm equal to 2000 pm and FL equal to 50 pN, the torsional resonance frequency is around 580 Hz, and the static displacement of the mirror relative to its equilibrium position is ±13°.

[0137] Note that the same parameters can be considered for the configuration illustrated in Figures 7A and 7B. In this configuration, the mass of the second mobile part S2 is lighter, the electrical line 30 being lighter than the magnet 20, which reduces the torsional resonance frequency.

[0138] The manufacturing process for a reflector device 1 is described below, according to several specific embodiments. For the sake of simplicity, only the manufacturing steps for a reflector device 1, according to the first configuration of the first embodiment, are schematically illustrated in Figures 11A, 11B to 14A, 14B. Those skilled in the art will readily adapt these figures to visualize the various steps of the manufacturing process for the reflector device 1 according to the other variants.

[0139] As illustrated in [Fig. 11 A] and 1 IB, one step of the process is to provide a substrate S extending along a plane parallel to the XY plane, and having a top face Sa and a bottom face Sb. The substrate S can be a SOI (Silicon-on-Insulator) type substrate. These known substrates comprise, according to the terminology commonly used by those skilled in the art, a bulk silicon carrier substrate, "Si bulk" (or massive silicon), and a silicon oxide layer called "BOX" (Buried Oxide).

[0140] An actuator module 6 is then formed on the upper face Sa of the substrate S. The formation of the actuator module 6 includes the deposition of a magnet 20, by depositing a stack 2 of N bilayers comprising a first sublayer 3 and a second sublayer 4 based on antiferromagnetic and ferromagnetic materials respectively, as illustrated in [Fig.2A].

[0141] Following its deposition, the stack 2 is subjected to heat treatment under the application of a magnetic field, as illustrated in [Fig. 2B]. The heat treatment is often carried out at a temperature above a so-called "blocking" temperature. Above the blocking temperature, the exchange interaction between the first antiferromagnetic sublayer 3 and the second ferromagnetic sublayer 4 disappears. This allows the magnetic moments in the ferromagnetic material to be reoriented according to the orientation of the applied external magnetic field. After the heat treatment and cooling of the stack 2 to a temperature below the blocking temperature, the exchange interaction is re-established, and the magnetic moments in the ferromagnetic material are fixed in the desired direction, which preferably lies in the principal extension plane of the bilayer.Thermal annealing is preferably carried out while maintaining an intensity. an external magnetic field of 1 T or greater in the desired direction for the entire duration of the annealing process, including cooling. Thermal annealing can be performed immediately after magnet deposition or later. Preferably, thermal annealing can be performed at the end of the process.

[0142] The blocking temperature can therefore correspond to the ordering temperature of the antiferromagnetic material when the antiferromagnetic material is magnetically unordered. An unordered antiferromagnetic material does not exhibit exchange coupling after deposition on a ferromagnetic material. This blocking temperature is more specifically the temperature above which there is no longer any exchange coupling between an antiferromagnetic material and a contacting ferromagnetic material when the antiferromagnetic material is magnetically ordered. This can be the Néel temperature, i.e., the temperature above which the antiferromagnetic material becomes paramagnetic. This blocking temperature is typically above 250°C for an unordered antiferromagnetic material. For an ordered AF antiferromagnetic material, the blocking temperature is typically between 150°C and 250°C.

[0143] The formation of the actuator module 6 further includes the formation of an electrical line 30 on the upper face Sa of the substrate S by deposition of an electrically conductive material 35. The electrically conductive material 35 may be based on a metal, such as aluminium or copper, preferably based on copper.

[0144] As illustrated in Figures 12A and 12B, a first partial etch is then made from the upper face Sa of the substrate S. This first etch allows the removal of a portion of the substrate S so as to separate the magnet 20 and the electrical line 30, and to define a first part SI and a second part S2 in the substrate S. The hinge 5 can be at least partially defined during this etch.

[0145] As illustrated in Figures 13A and 13B, a second engraving can be made from the lower face Sb of the substrate S. This second engraving allows for partial separation of the second part S2 from the substrate in order to give it a degree of freedom allowing it to rotate around a rotation axis Al that extends along the length of part S2. This partial separation can be made possible, in particular, by the hinge 5. The cross-sections KK' and LL' illustrated in [Fig. 13B] along the YZ and XZ planes, respectively, show the separation of the second part S2 from the first part SI, the movable second part S2 being surmounted by the electrical line 30 according to the first embodiment. Note that, in reality, the substrate S preferably exhibits a continuous layer between parts S1 and S2, by means of the torsionally deformable hinge 5.The first and second etchings can be dry etchings, preferably reactive ion etchings (RIE).

[0146] As illustrated in Figures 14A and 14B, a mirror 10 is formed on the second movable part S2 of the substrate S by depositing a reflective layer. This reflective layer may be based on a metallic material, preferably gold (Au) or aluminum (Al). It may also include a Bragg stack. The dimensions of the mirror 10 depend on the optical specifications of the reflecting device 1. The mirror 10 may, for example, have lateral dimensions in the XY plane of 2 mm x 2 mm and a thickness along the Z direction of 10 pm.

[0147] The formation of the stack 2 can be achieved by physical vapor deposition (PVD). This type of deposition simplifies the integration of the magnet 20 into the reflector device 1.

[0148] The number N of bilayers in the stack 2 determines the total thickness of the magnet 20. The stack 2 may have a thickness between 700 nm and 5 pm, preferably between 900 nm and 2 pm, and even more preferably equal to 1 pm. The length of the magnet in the XY plane may be on the order of 5 mm. Its width in the XY plane may be greater than or equal to 200 pm, preferably strictly greater than 200 pm, as exemplified by bar-shaped sub-magnets 25.

[0149] The effective magnetic thickness of the magnet 20 is the sum of the thicknesses of all the second ferromagnetic sublayers 4. Indeed, the antiferromagnetic material has substantially compensated magnetic moments, and consequently, does not produce a magnetic field, or produces an extremely weak magnetic field. It is primarily the magnetic moments present in the ferromagnetic material that contribute to the effective magnetization of the magnet 20. The second sublayer 4 has a thickness e4 of between 2 nm and 40 nm, preferably between 20 nm and 40 nm.

[0150] The effective magnetic thickness can be substantially between 350 nm and 2.5 pm, preferably between 450 nm and 1 pm, and even more preferably can be substantially equal to 0.5 pm, depending on the number of second ferromagnetic sublayers 4.

[0151] The ferromagnetic material may be based on a soft magnetic material having a strong saturation magnetization Ms, typically greater than 1000 emu / cm³. The ferromagnetic material may, for example, be based on an alloy of iron (Fe), cobalt (Co), and nickel (Ni). Preferably, the ferromagnetic material is based on CoFe.

[0152] The antiferromagnetic material may be based on an alloy comprising manganese (Mn), for example of the type NiMn, PdPtMn, FeMn or based on NiO or Fe2O3. The antiferromagnetic material is preferably based on PtMn or IrMn.

[0153] The CoFe composition of the ferromagnetic material allows control of the saturation magnetization Ms of the magnet 20. The ferromagnetic material can be richer in cobalt (Co) than in iron (Fe). This improves the exchange interaction between the first antiferromagnetic sublayers 3 and the second ferromagnetic sublayers 4, and consequently, improves the resistance of the magnet 20 to magnetic shocks. On the other hand, this tends to decrease the saturation magnetization Ms. For a composition of 20% Fe and 80% Co, Ms can be around 1.8 T.

[0154] The ferromagnetic material can be richer in iron (Fe) than in cobalt (Co). This increases the saturation magnetization Ms. However, it tends to decrease the exchange interaction between the first antiferromagnetic subshells 3 and the second ferromagnetic subshells 4. For a composition of 65% Fe and 35% Co, Ms can be around 2.4 T.

[0155] The composition of the antiferromagnetic material is chosen so as to improve the exchange interaction between the antiferromagnetic and ferromagnetic sublayers. This composition may be, for example, 50% ± 5% platinum (Pt) and 50% ± 5% manganese (Mn), or 20% ± 5% iridium (Ir) and 80% ± 5% manganese (Mn).

[0156] For a PtMn-based stack-2, the heat treatment can be carried out at a temperature between 290°C and 400°C, preferably around 320°C. For an IrMn-based stack-2, the heat treatment can be carried out at a temperature between 265°C and 350°C, preferably around 280°C. The thermal annealing can be carried out for a duration greater than or equal to 1 hour.

[0157] The stack 2 can be formed such that each second ferromagnetic sublayer 4 is located between two first antiferromagnetic sublayers 3, thereby improving the exchange interaction. This can be achieved by adding an additional antiferromagnetic sublayer to the N bilayers of the stack 2.

[0158] Each of the first 3 antiferromagnetic sublayers can have a thickness between 2 nm and 50 nm, preferably around 20 nm for a PtMn-based antiferromagnetic material, and preferably around 8 nm for an IrMn-based antiferromagnetic material.

[0159] Stack 2 may include a preliminary layer, on which the magnetic bilayers are deposited. The preliminary sublayer may be tantalum (Ta) based. This preliminary sublayer may have a thickness of around 5 nm.

[0160] The orientation of the magnetic field applied during heat treatment is chosen according to the desired magnetization M of the magnet 20. According to an example, and In particular, when the stack is configured to form juxtaposed, bar-shaped sub-magnets, the applied magnetic field is oriented at a 45° angle to the X and Y directions. This results in two perpendicular magnetization directions at the end of the heat treatment. The applied magnetic field preferably has an intensity greater than or equal to 1 T. In the example where the magnetic field direction is oriented at a 45° angle to the X and Y directions, a magnetic field intensity greater than or equal to 1 T is preferably applied during the heating phase of the thermal annealing process and during a plateau phase at a constant temperature. The magnetic field intensity is then reduced to a value between 20 Oe (1591.54 A / m) and 300 Oe (23873.24 A / m) during the cooling phase of the annealing process.This allows the shape anisotropy to fix the magnetizations in the desired directions.

[0161] Stack 2 may further include an encapsulation layer that protects the magnetic bilayers. This encapsulation layer may include a tantalum (Ta)-based sublayer, for example, with a thickness of 5 nm, and a ruthenium (Ru)-based sublayer, for example, with a thickness of 8 nm.

[0162] The following paragraphs of this description describe examples of manufacturing the actuator module 6 according to the first embodiment, with reference to Figures 15A-15D, 16A-16F and 17A-17I. Those skilled in the art will readily adapt these figures to visualize the various manufacturing steps of the actuator module 6 according to the second embodiment.

[0163] A first manufacturing step of the actuator module 6, common to all the examples described below, illustrated in Figures 15A and 15B, may include the following sub-steps: • The deposition of stack 2 on substrate S, as illustrated in [Fig. 15A]; • The deposition of a hard oxide-based mask onto the magnet (stack 2), not illustrated; • Formation by lithography of an aperture through the hard mask, preferably by reactive ion etching (RIE); • An etching of the stack 2 through the opening in the mask so as to form two first distinct magnets 20 as illustrated in [Fig.15B], this etching is preferably carried out by ion beam (IBE or “Ion Beam Etching” in English); The two magnets 20 formed are separated by a space exposing the inner flanks of the first two magnets 20 and the upper face Sa of the substrate S. The hard oxide-based mask can be kept on the magnets to protect them.

[0164] As illustrated in [Fig. 15C], following the formation of the separate magnets 20, according to a first embodiment of the actuator module 6, a layer of resin 50 is deposited on the first two magnets 20 so as to cover the surface and the inner flanks of the first two magnets 20 and to define a pattern intended for the formation of at least one electrical line 30 between the first two magnets 20. The electrically conductive material 35 is then deposited in the pattern defined in the previous step, to form the at least one electrical line 30. The resin layer 50 is removed after the deposition of the electrically conductive material 35.

[0165] As illustrated in Figures 16A-16F, according to a second embodiment of the actuator module 6, a first layer of oxide 61 is deposited on the first two magnets 20 so as to cover the surface and sides of the first two magnets 20, and to fill at least part, and preferably all, of the space between the first two magnets 20. A partial etching of the first layer of oxide 61 is then made perpendicular to the space between the first two magnets 20, substantially up to the plane comprising the upper face of the first two magnets 20, in order to form a pattern intended for the formation of at least one electrical line 30. A layer of electrically conductive material 35 is then deposited on the first layer of oxide 61, in order to fill at least part, and preferably all, of the pattern defined in the previous step, to form at least one electrical line 30.The layer of electrically conductive material 35 is then planarized until it substantially reaches the first oxide layer 61. Two separate second magnets 20 can be formed above the first oxide layer 61, and directly above the first two magnets 20. A second oxide layer 62 can be deposited so as to cover the surface and flanks of the two second magnets 20, and to fill at least part, and preferably all, of the space between the two second magnets 20. The second oxide layer 62 can be planarized so as to expose the upper face of the two second magnets 20. The stacking of the magnets 20 increases the saturation magnetization Ms, which facilitates the actuation of the rotation of the mirror 10.

[0166] As illustrated in Figures 17A-17E, according to a third embodiment of the actuator module 6, a first layer of oxide 61 is deposited on the upper face Sa of the substrate S, so as to cover the surface and flanks of the first two magnets 20, and to fill at least partially, and preferably completely, the space between the first two magnets 20. An etching of the first layer of oxide 61 is then made between the first two magnets 20 so as to expose the upper face Sa of the underlying substrate S, and preferably expose the inner flanks of the first two magnets 20. A layer of resin 50 is then deposited on the first magnets 20, so as to define a pattern between the first two Magnets 20 are separated from the inner flanks of the first two magnets 20, intended for the formation of the electric line 30. The deposition of the resin layer 50 on the first magnets 20 can, for example, be configured so as to cover at least the inner flanks of the first two magnets 20. The electrically conductive material 35 is then deposited in the pattern defined in the previous step, to form the electric line 30. The resin layer 50 is then removed, and a second oxide layer 62 is deposited so as to fill at least part, and preferably all, of the space between the formed electric line 30 and the first two magnets 20. The second oxide layer 62 can be planarized without exposing the surfaces of the magnets 20.A first actuator module 6 formed at the end of this example can be reproduced by following the same steps described with reference to Figures 17A-17E, in order to form a second actuator module 6 superimposed on the first, as illustrated in [Fig. 171].

[0167] More generally, it is understood that the actuator modules 6 can therefore be superimposed in the reflector device 1. The superposition of the actuator modules 6, in particular the magnets 20, makes it possible to increase the effective saturation magnetization Ms, which makes it easier to actuation the rotation of the mirror 10.

[0168] According to another example, as illustrated in Figures 17F-171, the first oxide layer 61 can be partially etched between the first two magnets 20 so as to expose at least part of the upper face Sa of the substrate S, without exposing the inner flanks of the first two magnets 20, and to define a pattern for the formation of the electric line 30. The electrically conductive material 35 is then deposited in the pattern defined in the previous step, to form the electric line 30. The layer of electrically conductive material 35 can be planarized, preferably without exposing the upper face of the first two magnets 20, and a second oxide layer 62 can be deposited, so as to cover the first two magnets 20 and the electric line 30.A first actuator module 6 formed at the end of this example can be reproduced by following the same steps described with reference to Figures 17F-17H, in order to form a second actuator module 6 superimposed on the first, as illustrated in [Fig. 171].

[0169] In view of the preceding description, it is clear that the proposed method offers a particularly efficient solution for integrating at least one magnet 20 into a reflector device 1 by depositing a stack 2. This solution is also advantageously compatible with standard microelectronic processes.

[0170] The invention is not limited to the embodiments described above and extends to all embodiments covered by the invention. Various specific examples of manufacturing processes as well as device configurations Several reflectors have been described. Many other embodiments are possible, for example by combining previously described features, without departing from the scope of the invention. Furthermore, the features described with respect to one aspect of the invention can be combined with another aspect of the invention.

Claims

1.

2. Demands A reflector device (1) intended to reflect an incident beam of light comprising: • a substrate (S) comprising a first part (SI), and a second part (S2) movable relative to the first part (SI) around at least one axis of rotation (Al), • a mirror (10) fixedly arranged on the second part (S2) of the substrate (S), the mirror (10) being configured so as to be pivoted about at least one axis of rotation (Al) and so as to receive the incident light beam to form a reflected beam, • an actuator module (6) comprising at least one magnet (20) and at least one electrical line (30) configured to carry an electric current (i), the at least one electrical line (30) being based on an electrically conductive material (35), the actuator module (6) being configured to drive in rotation the second part (S2) of the substrate (S) and the mirror (10) by a driving force (FL) generated by an interaction between the at least one magnet (20) and the electric current (i) passing through the at least one electrical line (30), Characterized in that one of the at least one magnet (20) and the at least one electric line (30) is disposed on the first part (S1) of the substrate (S), the other of the at least one magnet (20) and the at least one electric line (30) is disposed on the second part (S2) of the substrate (S) in a manner fixed to the mirror (10), and the at least one magnet (20) comprises a stack (2) of at least one bilayer comprising a first sublayer (3) based on an antiferromagnetic material and a second sublayer (4) based on a ferromagnetic material, the stack (2) being magnetized along at least one magnetization direction (M). A reflector device (1) according to the preceding claim, wherein at least one magnet (20) and at least one power line (30) are separated by a distance g, the shortest distance between at least one magnet (20) and at least one power line (30), the distance g being greater than or equal to 500 nm and less than or equal to 7 pm, preferably less than or equal to 5 pm.

3. Reflecting device (1) according to any one of the preceding claims, wherein the second sub-layer (4) based on a ferromagnetic material has a thickness e4 of between 2 nm and 50 nm, preferably between 10 nm and 50 nm.

4. Reflector device (1) according to any one of the preceding claims, wherein the stack (2) of at least one magnet (20) has a thickness between 700 nm and 5 pm, preferably between 900 nm and 2 pm, and more preferably equal to 1 pm.

5. Reflector device (1) according to any one of the preceding claims, wherein the stacking (2) of at least one magnet (20) comprises N superimposed bilayers, N being an integer between 10 and 50.

6. A reflector device (1) according to any one of the preceding claims, wherein the actuator module (6) is configured such that two driving forces are exerted on the second movable part (S2) of the substrate (S), said forces being in opposite directions to each other: • the actuator module (6) comprising at least two magnets (20), at least one electrical line (30) being disposed on the second movable part (S2) of the substrate (S) in a manner fixed to the mirror (10), the at least two magnets (20) being respectively disposed on the first part (S1) on either side of the at least one electrical line (30) with respect to the axis of rotation of the mirror (10), or • the actuator module (6) comprising at least two electrical lines (30), at least one magnet (20) being disposed on the second movable part (S2) of the substrate (S) in a manner fixed to the mirror (10),the at least two electrical lines (30) being respectively arranged on the first part (SI) of the substrate (S) on either side of the at least one magnet (20) with respect to the axis of rotation (Al) of the mirror (10).

7. A reflector device (1) according to any one of claims 1 to 5, wherein the actuator module (6) is configured so that two driving forces are exerted on the second mobile part (S2) of the substrate (S), said forces being in opposite directions to each other, the module comprising at least two magnets (20), at least one electric line (30) being disposed on the second mobile part (S2) of the substrate (S) in a manner fixed to the mirror (10), the at least two magnets (20) being respectively disposed on the first part (SI) on either side of the at least one electric line (30) with respect to the axis of rotation (Al) of the mirror (10), in which the second mobile part (S2) of the substrate (S) has a recess (8) around which the at least one electric line (30) forms a loop, the reflecting device (1) further comprising a third magnet (20) fixed to the first part (SI) of the substrate (S) and disposed in the recess (8).

8. Reflecting device (1) according to any one of the preceding claims, wherein the mirror (10) surmounts one of at least one magnet (20) and at least one electrical line (30).

9. Reflecting device (1) according to any one of the preceding claims, wherein the at least one magnet (20) comprises a plurality of sub-magnets (25) juxtaposed with each other, each sub-magnet (25) being in the form of a bar and comprising the stacking (2) of at least one bilayer.

10. Reflector device (1) according to the preceding claim, wherein the sub-magnets (25) have distinct magnetization directions (M) from each other.

11. A method for manufacturing the reflector device (1) according to any one of the preceding claims, the method comprising: • supplying a substrate (S), • forming the actuator module (6) on the upper face (Sa) of the substrate (S), the formation comprising: • deposition on the upper face (Sa) of the substrate (S) of a stack (2) of at least one bilayer comprising a first sublayer (3) based on an antiferromagnetic material and a second sublayer (4) based on a ferromagnetic material, superimposed on the first sublayer (3), • a heat treatment of the stack (2) deposited under the application of a magnetic field (B) so as to magnetize the stack (2) along at least one magnetization direction (M), • a deposit of an electrically conductive material (35) on the upper face (Sa) of the substrate (S), so as to form at least one electrical line (30), • a deposit of a mirror (10) on the upper face (Sa) of the substrate (S), • at least one etching of the substrate (S) so as to form a first part (SI) and a second part (S2) movable relative to the first part (SI) around at least one axis of rotation (Al), the deposits and the etching being configured together so that the mirror (10) is deposited on the second part (S2) of the substrate (S), one of the at least one magnet (20) and the at least one electrical line (30) is disposed on the first part (SI) of the substrate (S),the other, among at least one magnet (20) and at least one electrical line (30), is disposed on the second part (S2) of the substrate (S).

12. Method of manufacturing the reflector device (1) according to the preceding claim, wherein the ferromagnetic material is based on CoFe, and the antiferromagnetic material is based on PtMn or IrMn.

13. A method for manufacturing the reflector device (1) according to any one of the two preceding claims, wherein the heat treatment of the stack (2) is carried out at a temperature greater than or equal to 265°C, preferably for a period greater than or equal to 1 hour.

14. A method for manufacturing the reflector device (1) according to any one of the three preceding claims, wherein the intensity of the magnetic field (B) applied during at least a part of the heat treatment is greater than or equal to 1 T.

15. A method for manufacturing the reflector device (1) according to any one of the four preceding claims, wherein the formation of the actuator module (6) further comprises: • an engraving of the stack (2) deposited so as to form two distinct first magnets (20), separated by a space exposing the inner flanks of the first two magnets (20) and the upper face (Sa) of the substrate (S),

16. A method for manufacturing the reflector device (1) according to the preceding claim, wherein the formation of the actuator module (6) further comprises: • a deposition of a layer of resin (50) on the first two magnets (20) so as to cover the surface and the inner flanks of the first two magnets (20) and to define a pattern intended for the formation of at least one electrical line (30) between the first two magnets (20), • the deposition of the electrically conductive material (35) in the pattern defined in the preceding step, to form the at least one electrical line (30), • a removal of the layer of resin (50) after the deposition of the electrically conductive material (35).

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