Microelectromechanical mirror, method for operating a microelectromechanical mirror, projection device and method for producing a micromechanical mirror

Abstract

The invention relates to a microelectromechanical mirror (1) which comprises a mirror element (2) with a planar top side (21) and an underside (22) arranged opposite the planar top side (21), with the mirror element (2) comprising a support structure (4) arranged on the underside (22) of the mirror element (2). Further aspects relate to a method for operating a microelectromechanical mirror, a projection device and a method for producing a micromechanical mirror.

Description

[0001] Description

[0002] MICROELECTROMECHANICAL MIRROR, METHOD FOR OPERATING A MICROELECTROMECHANICAL MIRROR, PROJECTION DEVICE AND METHOD FOR PRODUCING A MICROELECTROMECHANICAL MIRROR

[0003] A microelectromechanical mirror, a method for operating a microelectromechanical mirror, a projection device and methods for producing a micromechanical mirror are specified.

[0004] Microelectromechanical mirrors are used, for example, in laser projectors for the targeted deflection of a laser beam in order to display static or moving images. For example, laser projectors are used in the automotive sector to project information onto a road surface, in HUD display systems (head-up display) for matrix illumination or for LIDAR applications (light detection and ranging). This requires a particularly high depth of field, which laser projectors can provide. Laser projectors are also used, for example, as hologram projectors, in VR glasses (virtual reality) or AR glasses (augmented reality). Here the deflected laser beam is coupled into a waveguide lens, for example.The direction and not the position of the laser beam determines the position of the image point for the viewer, so that no additional optics are required.

[0005] Laser projectors that are insensitive to vibrations and inexpensive to manufacture are particularly advantageous for mobile applications, for example in the automotive sector or for VR or AR headsets. A laser projector, for example, has a microelectromechanical mirror that can be rotated in two directions and deflects a time-modulated laser beam to generate an image in the far field. In particular, the projected image is always in focus for an observer, and one of the observer's eyes does not need to be accommodated.

[0006] To implement laser projectors, micromechanical mirrors with good optical properties are required. In particular, a small wavefront distortion of light reflected from a mirror surface is required. This means that static and dynamic deformations—that is, deformations of the stationary or moving mirror from a planar plane—must not be excessive.

[0007] US 2005 / 0162765 A1 describes a micromechanical mirror in which a reinforcement structure is manufactured using sacrificial layers.

[0008] At least one object of the present invention is to provide an improved micromechanical mirror which, for example, has good optical properties. At least one further object of certain embodiments is to provide a projection device having such a micromechanical mirror. At least one further object of certain embodiments is to provide a method for operating such a mirror. At least one further object of certain embodiments is to provide methods for producing such a mirror.

[0009] These problems are solved by the subject-matter of the independent claims.

[0010] The micromechanical mirror has a mirror element which has a planar upper side and a lower side arranged opposite to the planar upper side. The micromechanical mirror has a support structure which is arranged on the lower side of the mirror element.

[0011] The support structure can stiffen the mirror element. The support structure can provide local stiffening at certain positions of the mirror element. The support structure can preferably be designed to create local stiffening at positions that, without the support structure, would experience particularly severe deformation upon oscillation of the mirror element.

[0012] The support structure can have rib-shaped support elements. The rib shape of the support elements allows deformation to be reduced in a targeted manner at those positions on the mirror element where particularly severe deformations would occur without support elements. By using rib-shaped support elements, the mass of the mirror element is only slightly increased compared to flat support elements. Accordingly, the resonance frequencies and the moment of inertia of the mirror element are only slightly changed by the addition of the rib-shaped support elements. At the same time, the deformation, in particular the dynamic deformation, of the mirror element can be considerably reduced through a targeted arrangement of the rib-shaped support elements.

[0013] In this way, the optical properties of the micromechanical mirror can be improved.

[0014] The mirror element has, in particular, a main extension plane. For example, the mirror element has a circular, oval, square, rectangular, or polygonal shape when viewed from above onto the main extension plane. The upper side can be completely planar in the main extension plane of the mirror element. The upper side can be referred to as "planar" if it is even or flat and has no elevations or indentations. If the mirror element is used in a projection device, a laser beam is directed onto the upper side.

[0015] In particular, the upper surface can be planar even in the positions opposite a support structure on the underside. The planarity of the upper surface ensures good optical performance of the mirror element. Irregularities in the upper surface, on the other hand, would lead to distortions in the image reproduction of the mirror element.

[0016] The planar upper side can be reflective. The mirror element comprises, for example, a substrate with a reflective layer applied thereto, which ensures that the planar upper side is reflective. For example, the substrate comprises silicon or is made of silicon. Alternatively or additionally, the substrate can comprise diamond, cubic boron nitride (BN), silicon nitride (SiN) or boron, or can be made of at least one of these materials. For example, the reflective layer comprises a metal or is made of a metal. In particular, the reflective upper side is designed to reflect and / or deflect electromagnetic radiation in a spectral range between infrared and ultraviolet light. The reflective layer extends, in particular, in a plane which here corresponds to the main extension plane of the mirror element.Here and in the following, the main extension plane is defined with respect to a rest position of the mirror element.

[0017] The mirror may further comprise a drive element. The drive element may comprise a piezoelectric drive element. The drive element may be configured to excite the mirror element to oscillate, wherein the oscillation excitable by the drive element may be a torsional oscillation.

[0018] The drive element can be designed to excite a torsional oscillation with two oscillation modes. In the first oscillation mode, the mirror element oscillates about a first axis of rotation and in the second oscillation mode about a second axis of rotation. Both torsional oscillations can superimpose one another. The drive element can, in particular, be annular. The drive element can enclose the mirror element.

[0019] The support structure can be composed of rib-shaped support elements. A rib-shaped support element can have a narrow, elongated shape. A rib-shaped support element can be approximately two-dimensional. A rib-shaped support element can have a length and a height that are significantly greater than a width of the rib-shaped support element. For example, the length and the height can each be at least three times as great as the width. Ribs of the rib-shaped support element can be straight or curved structures with a small width compared to the length, where the width is, for example, less than a tenth of the length.

[0020] The rib shape is particularly advantageous for the support elements because the height of the support structure contributes to the stiffness of the mirror element to the third order, while the width has only a linear influence. Accordingly, even support structures with a small width can significantly increase the stiffness of the mirror element. Due to the small width, the mass of the mirror element is not increased excessively by the support structure, so the moments of inertia and thus the resonance frequencies of the mirror element are not changed too much.

[0021] The rib-shaped support elements can be manufactured from a multilayer substrate, in particular, using an etching process, whereby an etching process can be limited by an etch stop layer within the multilayer substrate. This process makes it possible to manufacture the support elements with very high precision. Furthermore, this process makes it possible to manufacture support elements whose width is small compared to their height.

[0022] The mirror element undergoes deformation during torsional oscillation. Deformation is defined as a deviation from the planar shape of the mirror element. The amplitude of the deformation can vary across the planar upper side of the mirror element. According to one embodiment, the rib-shaped support elements are arranged at positions on the underside that are opposite positions on the planar upper side where the amplitude of the deformation would be greater than an average amplitude of the deformation across the entire upper side of the mirror element if no rib-shaped support elements were arranged there. Accordingly, the rib-shaped support elements can be arranged precisely at those positions where a mirror element without support elements would undergo particularly severe deformation.This targeted arrangement of the support elements allows for significant improvements in deformation and thus in the optical properties of the mirror element, while simultaneously preventing excessive increases in the mass of the mirror element. It is thus possible to create targeted stiffening only at the positions and in the orientations that require it.

[0023] The support structure can be arranged, at least in places, at a position where the amplitude of a deformation of the mirror element without the support structure is at a maximum. Reducing the deformation at the positions where a maximum would occur without the support structure leads to a targeted reduction of the particularly strong deformations and thus to an improvement in the optical properties of the mirror element.

[0024] The support elements can only be positioned at strategically important locations, so that the increase in mass of the mirror element caused by the addition of the support structure is minimized. Strategically important positions are those that would experience significant deformation if no support elements were installed there.

[0025] In one embodiment, the rib-shaped support elements have a width and a height, wherein the height is an extension of the rib-shaped support elements in the direction of the surface normal of the underside, which points away from the upper side, and wherein the width of the rib-shaped support elements indicates a minimum extension of the rib-shaped support elements in a direction that is perpendicular to the height, wherein the height is at least three times as large as the width of the rib-shaped support elements, preferably the height is at least six times or at least ten times as large as the width.

[0026] The width and / or height of the rib-shaped support elements can vary across the support structure. Accordingly, the support structure can result in varying degrees of stiffening of the mirror element at different positions, which in turn contributes to the targeted adjustment of the stiffeners and, in particular, to significantly stiffening positions that would experience particularly severe deformation without the support structure.

[0027] The support structure can be composed of several rib-shaped support elements.

[0028] The geometric arrangement of the support structures relative to the mirror element is always described below from a perspective in which the mirror element is viewed in a direction perpendicular to the main extension plane. The support structure may comprise a rib-shaped support element forming a ring that is concentric with the mirror element. Accordingly, the center of the ring and the center of the mirror element may coincide.

[0029] The ring can be arranged, in particular, near an edge region of the mirror element. For example, the ring can have a diameter of more than 80%, preferably more than 90%, of the diameter of the mirror element. If the ring is arranged close to the edge of the mirror element, it can, in particular, contribute to reducing deformations caused by a first vibration mode in which the mirror element performs a torsional vibration about a long axis of a torsional suspension.

[0030] A rib-shaped support element of the support structure can form rectangles, with the corners of the rectangles lying on the ring. The rectangles can also contribute to stiffening a central region of the mirror element. In particular, the rib-shaped support element can form several rectangles that are regularly arranged relative to one another and are each rotated by a fixed angle relative to the adjacent rectangles.

[0031] The ring described above can be an outer ring, the support structure further comprising a further rib-shaped support element which forms an inner ring. Both rings can be arranged concentrically with the mirror element, the inner ring having a smaller diameter than the outer ring. The support structure can further comprise rib-shaped support elements which connect the inner ring and the outer ring to one another and which point straight radially away from the center point of the inner ring. Support elements which are arranged in the central region of the mirror element in particular reduce deformations which arise in a second oscillation mode of the mirror element, in which the mirror element executes a torsional oscillation about a short axis of the torsional suspension.

[0032] The support structure may comprise a rib-shaped support element forming a straight beam extending along an axis about which the mirror element oscillates during torsional vibration. The axis may be the short axis or the long axis. This beam contributes in particular to reducing deformations generated by the second vibration mode. The beam may connect two suspension points at which a connecting element is suspended from the mirror element, the connecting element connecting the mirror element to a torsional suspension.

[0033] The support structure may comprise a rib-shaped support element forming an ellipse whose center coincides with the center of the mirror element.

[0034] The support structure may comprise a rib-shaped support element forming a lattice structure. The lattice structure may, for example, comprise triangular cells. The lattice structure may, for example, be formed by straight rib-shaped

[0035] Support elements are formed. The support structure can have rib-shaped support elements, each forming an elliptical section, wherein the elliptical sections intersect at the center of the mirror element.

[0036] The support structure may comprise rib-shaped support elements forming circles, the circles intersecting at the center of the mirror element.

[0037] The micromechanical mirror may have a torsion suspension which surrounds the mirror element and is connected to the mirror element via two first torsion spring elements, wherein the drive element has a drive ring which surrounds the torsion suspension and is connected to the torsion suspension via two second torsion spring elements.

[0038] In particular, the torsion suspension encloses the mirror element of the main extension plane of the mirror element when the mirror element is at rest. The torsion suspension comprises, for example, a substrate formed in a ring shape in the main extension plane, in the center of which the mirror element is arranged. For example, the substrate comprises silicon or is made of silicon. During operation of the micromechanical mirror, in which in particular the mirror element is moved, the main extension plane of the mirror element can be rotated relative to the torsion suspension.

[0039] Each of the torsion spring elements comprises, in particular, a torsion beam or consists of the torsion beam. For example, the torsion spring elements comprise a substrate which, for example, comprises silicon or is made of silicon. The torsion spring elements each have, for example, an elongated, beam-like shape with an axis of rotation which, in particular, corresponds to a longitudinal direction of the respective torsion spring element. During operation, the torsion spring elements are subjected, for example, to a torsional moment with respect to the axis of rotation, as a result of which the torsion spring elements twist about their respective axis of rotation. In this case, a restoring torsional moment builds up in the torsion spring elements.

[0040] The axes of rotation of the two first torsion spring elements are preferably aligned along a common first axis of rotation. In other words, the two first torsion spring elements have a common first axis of rotation about which they twist during operation. The mirror element is rotatable at least within a first angular range about the first axis of rotation relative to the torsion suspension.

[0041] The drive element is particularly designed to deflect the mirror element from its rest position during operation. In this case, the torsion suspension and / or the mirror element are preferably rotated relative to the drive element. For example, mechanical stresses are generated in the drive element, which, via the second torsion spring elements, result in a bending element and / or a torque on the torsion suspension.

[0042] The axes of rotation of the two second torsion spring elements are preferably aligned along a common second axis of rotation. In other words, the two second torsion spring elements have a common second axis of rotation, which twist during operation. In particular, the torsion suspension and thus the mirror element are rotatable about the second axis of rotation relative to the drive ring at least within a second angular range. The second axis of rotation is, for example, transverse or orthogonal to the first axis of rotation.

[0043] The torsion suspension has an elongated shape with a long axis and a short axis perpendicular thereto. The first torsion spring elements are arranged along the long axis and the second torsion spring elements can be arranged along the short axis according to one embodiment. The long and short axes are, for example, axes of symmetry of the torsion suspension. In particular, the torsion suspension has a greater spatial extent in the direction of the long axis than in the direction of the short axis. For example, the diameter of the torsion suspension in the direction of the long axis is at least 5% larger, preferably at least 20 or 40% larger, than the diameter in the direction of the short axis. The long axis and the short axis lie, for example, in the main extension plane of the mirror element.

[0044] The first axis of rotation, for example, coincides with the long axis, while the second axis of rotation, for example, coincides with the short axis. During operation, the mirror element is therefore at least partially rotatable relative to the drive element, particularly with respect to the short axis and the long axis.

[0045] The micromechanical mirror may further comprise a frame that surrounds the drive element and is connected to the drive element via two third torsion spring elements. The drive element may be configured to excite the mirror element to a torsional oscillation having a first oscillation mode along a first axis and a second oscillation mode along a second axis, wherein the second axis is perpendicular to the first axis.

[0046] The mirror element and the drive element can be formed as a one-piece component. In particular, the mirror element, the drive element, the torsion suspension, the frame and the torsion spring elements can all be formed as a single one-piece component. In other words, the elements can be monolithically integrated. The elements can be formed from a single common substrate. The substrate can be monocrystalline. Furthermore, a connecting element between the first torsion spring elements and the mirror element can also be formed integrally with the above-mentioned elements. For example, during production of the micromechanical mirror, the common substrate is structured such that the above-mentioned elements are formed in the common substrate.

[0047] The mirror element and the drive element can have a common substrate which has a constant thickness. Here and in the following, the thickness of the substrate describes a spatial extent in a direction perpendicular to the main extension plane. This particularly simplifies the production process of the micromechanical mirror. For example, the thickness of the substrate is between 20 pm and 500 pm. Furthermore, a method for operating a microelectromechanical mirror is specified. The method is particularly applicable to operating the microelectromechanical mirror described here. All features of the microelectromechanical mirror are also disclosed for the method for operating a microelectromechanical mirror, and vice versa.

[0048] According to at least one embodiment of the method for operating a microelectromechanical mirror, the mirror element is placed into a first oscillation mode by means of a first electrical alternating current signal having a first frequency, which acts on first control regions of the drive element, and a torsion suspension is placed into a second oscillation mode by means of a second electrical alternating current signal having a second frequency, which acts on second control regions of the drive element. In particular, in the second oscillation mode, the torsion suspension oscillates together with the mirror element.

[0049] According to at least one further embodiment of the method, the first oscillation mode and the second oscillation mode are resonantly excited. In particular, the first oscillation mode and the second oscillation mode are excited simultaneously and superimpose during operation of the microelectromechanical mirror.

[0050] According to at least one further embodiment of the method, the second oscillation mode is a torsional oscillation of the torsional suspension with the mirror element about the short axis, while the first oscillation mode is a combination of a torsional oscillation of the mirror element about the long axis and a bending movement of the torsional suspension. In particular, the first oscillation mode is a so-called "rocking" mode, in which, for example, one of the two second torsion spring elements is periodically moved in a direction perpendicular to the main extension plane of the mirror element, while the other of the two second torsion spring elements is moved, for example, in antiphase thereto. This in particular excites an oscillation of the mirror element about the long axis.

[0051] Furthermore, a projection device is specified. The projection device comprises, in particular, the microelectromechanical mirror described here. All features of the microelectromechanical mirror are also disclosed for the projection device, and vice versa.

[0052] According to at least one embodiment, the projection device comprises a laser light source and a microelectromechanical mirror described herein. During operation, the microelectromechanical mirror deflects laser light emitted, for example, by the laser light source. Due to the previously described oscillation modes of the mirror element, the deflected laser light can, in particular, scan an image area perceivable by an observer. In particular, the microelectromechanical mirror is configured for Lissajous scanning of the image area.

[0053] According to at least one embodiment, the microelectromechanical mirror is used for projecting information onto a surface, for head-up displays, for matrix illumination, for LIDAR applications, for hologram projectors, for VR glasses, or for AR glasses.

[0054] According to at least one embodiment, a method for producing the micromechanical mirror described above is provided. The method comprises the steps of: a. providing a multilayer silicon wafer having a first silicon layer and a second silicon layer, b. structuring the first silicon layer to form the mirror element, and c. structured etching of the second silicon layer to form the support structure.

[0055] The steps are carried out in the order given.

[0056] By structuring the multilayer wafer, the support structure can be manufactured with high precision. Furthermore, the process enables the production of support elements with a width that is small compared to the height, for example, less than one-third of the height. The thickness of the second silicon layer can define the height of the support structure.

[0057] The multilayer silicon wafer can be an SOI wafer (SOI = silicon-on-insulation), in which the two silicon layers are separated by an insulation layer. The insulation layer can be a BOX layer (BOX = buried oxide). The multilayer silicon wafer can also comprise other materials in which the etching step for creating the support structure is coordinated with an etch stop layer. For example, the first and second silicon layers can comprise differently doped silicon and be etched with potassium hydroxide (KOH). The silicon layers can comprise silicon oxide and be separated by an etch stop layer comprising silicon nitride. Controlled etching of silicon can be achieved by an electrochemical etch stop. Indium phosphide with indium gallium arsenide can be used as the etch stop, or vice versa.Gallium arsenide can be used with aluminum gallium arsenide as an etch stop, with an aluminum content of at least 80%, or vice versa. Silicon can be used with a metal layer or a polymer as an etch stop layer.

[0058] In some embodiments, the method further comprises step d., in which the structured multilayer silicon wafer is bonded or adhered to a second wafer. A recess may be structured in the second wafer, which recess is arranged beneath the mirror element after the second wafer has been bonded to the silicon wafer.

[0059] In some embodiments, the wafer provided in step a. has a third silicon layer arranged on a side of the second silicon layer facing away from the first silicon layer. The third silicon layer can be etched before step c., so that only a frame remains of the third silicon layer, which completely encloses the mirror element. In this case, structuring of the second wafer can be omitted.

[0060] Preferably, the wafer provided in step a. has an etch stop layer, which limits the respective etching process during the structuring in step b. and during the etching in step c. The use of an etch stop layer makes it possible to manufacture the support structure with high precision. Furthermore, the etch stop layer makes it possible to manufacture support elements with a width that is small compared to the height and, for example, less than one-third of the height.

[0061] Before step a, the positions at which the mirror element without a support structure would experience the greatest deformation during a torsional vibration can be determined in the manufacturing process. The support structure can then be formed in step c at the previously determined positions at which the mirror element experiences the greatest deformation during the torsional vibration. The positions can be determined by simulations and / or calculations.

[0062] In an alternative method for producing a micromechanical mirror, an etching stop layer can be dispensed with. The alternative method has the following steps: i. producing the support structure from a silicon wafer in an etching process, ii. bonding a planar wafer to the support structure, iii. applying a reflective layer to the planar wafer, iv. applying the drive element to the planar wafer, and v. structuring the planar wafer to form the mirror element. Further advantageous embodiments and developments of the microelectromechanical mirror, the methods for operating and producing a microelectromechanical mirror, and of the projection device emerge from the exemplary embodiments described below in conjunction with the figures.

[0063] Figures 1 and 2 show two embodiments of the mirror.

[0064] Figures 3 to 5, 7 and 9 to 41 show nine embodiments of the support structure and the reduction in dynamic deformation achieved in each case.

[0065] Figure 6 and Figure 8 show the dynamic deformation of a comparative example without support structure.

[0066] Figure 42 shows a table comparing the embodiments and the comparative example.

[0067] Figures 43 to 57 show the mirror during various processes for its manufacture .

[0068] Figure 58 shows the micromechanical mirror in a perspective view.

[0069] The microelectromechanical mirror 1 according to a first design in Figure 1 has a mirror element 2, a connecting element 6, a torsion suspension 3, a drive element 5, a frame 7, and two first, second, and third torsion spring elements 41, 42, 43, which are formed integrally from a common substrate. In particular, Figure 1 shows a plan view of the main extension plane of the mirror element 2. The main extension plane is parallel to a planar upper side 21 of the mirror element 2.

[0070] The mirror element 2 is circular or elliptical and has, for example, a diameter of between 1 mm and 2 mm. Applied to an upper side 21 of the mirror element 2 is a reflective layer comprising a metal, a dielectric mirror, or a nanostructured surface, which is designed to reflect electromagnetic radiation in a spectral range between infrared and ultraviolet light.

[0071] The connecting element 6 mechanically connects the mirror element 2 to two first torsion spring elements 41, which are arranged on opposite sides of the mirror element 2. The connecting element 6 comprises two circular arc-shaped segments 62, each of which is mechanically connected to the mirror element 2 via two suspension points 61 at its ends. The two first torsion spring elements 41 are each mechanically connected to one of the segments 61 in the middle between the two suspension points 61.

[0072] The two first torsion spring elements 41 mechanically connect the connecting element 6 to the torsion suspension 3. The torsion suspension 3 completely encloses the mirror element 2 and the connecting element 6 in the main extension plane, so that the mirror element 2 is arranged in the center of the torsion suspension 3. The torsion suspension 3 has an elongated shape with a long axis 31 and a short axis 32, which are each axes of symmetry of the torsion suspension 3. The diameter of the torsion suspension 3 along the long axis 31 is 40% to 60% larger than the diameter of the torsion suspension 3 along the short axis 32, for example by 50%. A circumference of the torsion suspension 3 has the shape of an indented or constricted oval. The first two torsion spring elements 41 are arranged along the long axis 31.

[0073] The two second torsion spring elements 42 mechanically connect the torsion suspension 3 to the drive element 5. The two second torsion spring elements 42 are arranged on opposite sides of the torsion suspension 3 along the short axis 32.

[0074] The drive element 5 comprises a piezoelectric drive element. If a voltage is applied to the piezoelectric drive element, a substrate on which the drive element 5 is arranged is mechanically stressed by the piezoelectric effect. Since the mirror element 2 and other elements of the mirror 1 are also formed by the substrate, the stress is transferred to the mirror element and excites the mirror element 2 to move, in particular torsional vibration.

[0075] The piezoelectric drive element 5 has a drive ring. The piezoelectric drive element 5 is, for example, circular or elliptical. The piezoelectric drive element 5 is mechanically connected to the frame 7 via two third torsion spring elements 43. The torsion suspension 3 is arranged in the center of the drive element 5. The frame 7 completely encloses the drive element 5 in the main extension plane. A piezoelectric layer made of PZT is applied to a main surface of the drive element 5, which is arranged parallel to the main extension plane, and is arranged between a first electrode and a second electrode 52. The second electrode 52 has separate first control regions 521a, 521b and second control regions 522a, 522b.

[0076] By applying a temporally oscillating electrical voltage between the first electrode and the first control regions 521a, 521b of the second electrode 52, a first oscillation mode of the microelectromechanical mirror 1 can be excited. By applying a temporally oscillating electrical voltage between the first electrode and the second control regions 522a, 522b of the second electrode 52, a second oscillation mode of the microelectromechanical mirror 1 can be excited. The first oscillation mode 11 comprises, in particular, a torsional oscillation of the mirror element 2 about the long axis 31, while the second oscillation mode 12 comprises, in particular, a torsional oscillation of the mirror element 2 about the short axis 32. The electrical voltage is applied in the first control regions 521a and 521b, in particular with opposite phases.Likewise, the electrical voltage in the second control regions 522a and 522b is applied in particular with opposite phase.

[0077] Sensor elements 9 for determining a deflection and / or a frequency of the oscillation of the mirror element 2 during operation of the microelectromechanical mirror 1 can be arranged both on the drive element 5 and on the frame 7. The sensor elements 9 comprise a piezoelectric layer arranged between a first electrode 91 and a second electrode. The sensor elements 9 detect, in particular, mechanical stresses in the microelectromechanical mirror 2 that occur during an oscillation of the mirror element 2 during operation of the microelectromechanical mirror 1.

[0078] Figure 2 shows a second design of the mirror. The torsion suspension 3 has an elliptical ring shape. Furthermore, further sensor elements 9 can be arranged on a main surface of the torsion suspension 3, which is arranged parallel to the main extension plane. The sensor elements 9 comprise a piezoelectric layer which is arranged between a first electrode and a second electrode. The second electrode is segmented, so that the sensor element 9 on the torsion suspension 3 has a plurality of readout regions. The measuring accuracy of the sensor elements can be improved, for example, by means of the further sensor elements 9 on the torsion suspension 3.

[0079] Furthermore, the connecting element 6 in the second design is circular and has two suspension points 61 for the mirror element 2 along the short axis 32. The connecting element 6 completely encloses the mirror element 3. The suspension points 61 are arranged at opposite points on the mirror element 3, with the axis 32, around which the mirror element performs a torsional vibration in the second vibration mode, passing through the two suspension points 61.

[0080] The micromechanical mirror 1 shown in Figures 1 and 2 is manufactured from a silicon substrate. The mirror element 2, the connecting element 6, the torsion suspension 3, the drive element 5 and the frame 7 are manufactured in one piece from a single wafer substrate. The substrate has the orientations <100> , <010> , <001> which are each parallel to the axes that span the main extension plane or that are parallel to a surface normal of the main extension plane.

[0081] The mirror element 2 can have a thickness between 50 pm and 200 pm, for example, a thickness of 100 pm. A piezoelectric layer of the drive element 5 can have a thickness between 1 pm and 2 pm, for example, 1.7 pm.

[0082] In the following , a mirror element 2 with a thickness of 100 pm is considered , which can be excited to a first oscillation mode with a resonance frequency of 18,518 kHz and to a second oscillation mode with a resonance frequency of 35,322 kHz .

[0083] Figures 1 and 2 each show a micromechanical mirror 1, which has a mirror element 2, a torsion suspension 3, a support structure 4, a drive element 5, a connecting element 6, a frame 7 and sensor elements 9. The torsion suspension 3, the drive element 5, the connecting element 6, the frame 7 and the sensor elements 9 represent optional elements. In an alternative embodiment, the mirror only has a mirror element 2, on the underside 22 of which a support structure 4 is arranged. In this alternative embodiment, the mirror does not have the torsion suspension 3, the drive element 5, the connecting element 6, the frame 7 and the sensor elements 9. Figure 3 shows a perspective view of the underside of the mirror 1 according to a first embodiment. Figure 4 shows a plan view of the underside of the mirror 1 according to the first embodiment.In the first embodiment and in the following embodiments, the second design of mirror 1 is used. The support structures shown here can also be arranged on mirror 1 according to the first design.

[0084] On an underside 22 of the mirror element 2, a support structure 4 is arranged, which has support elements 10, 11, 12. The support elements 10, 11, 12 each have a narrow, elongated shape. The support elements 10, 11, 12 are perpendicular to the underside 22 of the mirror element 2. In a plane parallel to the underside 22 of the mirror element 2, the support elements 10, 11, 12 run almost two-dimensionally. The support elements 10, 11, 12 are rib-shaped, whereby the ribs formed by the support elements 10, 11, 12 can be straight or curved. The support structure 4 is composed of several support elements 10, 11, 12.

[0085] The support structure 4 reduces the deformations experienced by the mirror element 2 during oscillations in the first and second oscillation modes. These deformations are undesirable and lead to a distortion of the optical behavior of the mirror element 2. By adding the support structure 4, the amplitude of the deformations can be reduced.

[0086] The deformations deform the mirror element 2 from its planar shape. The deformations occur as dynamic deformations during the first and second oscillation modes. The deformations exhibit an amplitude, with positions at which the mirror element 2 is particularly strongly deformed or distorted being characterized by a high amplitude of the deformation.

[0087] The rib-shaped support elements 10, 11, 12 are applied at the positions of the mirror element 2 which experience particularly strong deformations during the vibrations of the mirror element 2.

[0088] The rib-shaped support elements 10, 11, 12 have a width B between 30 and 70 pm, in particular 50 pm, and a height H between 150 and 250 pm, in particular 200 pm. The height H is at least three times the width B. The width B refers to an extension of the support elements 10, 11, 12 in a direction parallel to the underside 22 of the mirror element 2, wherein at each position of the rib-shaped support elements 10, 11, 12 the respective minimum extension in a direction parallel to the underside 22 of the mirror element 2 is referred to as width B. The height H of the support element 10, 11, 12 is the extension of the support element 10, 11, 12 along the surface normal of the underside 22 of the mirror element 2. The height H indicates the distance from the underside 22 of the mirror element 2 to the end of the support element 10, 11, 12 pointing away from the underside 22.Figure 5 shows a section of the mirror element 2 shown in Figure 3, wherein the height H and the width B of a rib-shaped support element are shown.

[0089] The support elements 10 , 11 , 12 are designed so that they

[0090] Reduce deformations of the mirror element 2 as much as possible and at the same time increase the moment of inertia of the mirror element 2 as little as possible. The support elements 10, 11, 12 should have high rigidity and low weight. These apparently contradictory goals can be achieved by support elements 10, 11, 12 whose height H is at least three times the width B, since the height of the support elements 10, 11, 12 has a third-order influence on the rigidity of the mirror element and the width B only has a linear influence on the rigidity.

[0091] The support structure 4 of the first exemplary embodiment has the following rib-shaped support elements 10, 11, 12. A rib-shaped support element 10 is annular and forms a ring. The center point of the ring coincides with the center point of the mirror element 2 when the mirror 1 is viewed in a plan view onto the main extension plane of the mirror element 2. The ring is arranged close to the edge of the underside. For example, a diameter of the ring can be greater than 90% of the diameter of the mirror element 2 and less than or equal to 100% of the diameter of the mirror element 2.

[0092] Another rib-shaped support element 11 is straight and forms a beam that runs straight along the short axis 32 of the torsion suspension 3 through a center point of the mirror element 2. The beam can connect two opposite points of the ring. The beam runs along the connecting line of the suspension points 61, at which the connecting element 6 is connected to the mirror element 2. Another rib-shaped support element 12 can form an ellipse, the center point of which is in the center of the mirror element.

[0093] 2 . The size of the ellipse can be selected such that the ellipse touches the ring . In particular, the ellipse can touch the ring at the positions where the short axis 32 of the torsion suspension 3 intersects the ring . The ellipse touches the ring at the positions where the straight beam meets the ring .

[0094] The support structure 4 on the underside 22 of the mirror element 2 adds additional mass to the mirror element 2. This increases the moment of inertia of the mirror element 2, which leads to a change in the resonance frequencies for the oscillation modes of the mirror element 2. The support structure 4 is designed such that the changes in the resonance frequencies and the increase in the moment of inertia are kept as small as possible. The table shown in Figure 42 shows the change in the resonance frequencies of the two oscillation modes and the increase in the moments of inertia for the two oscillation modes in percent. This table also indicates how much the dynamic deformation of the mirror element can be reduced by adding the support structure.

[0095] For the first vibration mode, in the embodiment shown in Figure 3, an amplitude of the dynamic deformation by the support structure 4 can be a factor greater

[0096] 3 be reduced .

[0097] Figure 6 shows a dynamic deformation of a

[0098] Comparative example in which the one shown in Figure 3

[0099] Mirror element 2 is used without support structure 4 and the dynamic deformation of the mirror element 2 for the first vibration mode is determined at each position. Figure 7 shows the dynamic deformation of the mirror element 2 shown in Figure 3. The respective deformations were calculated using simulation data.

[0100] It can be seen that the dynamic deformation is reduced by the addition of the support structure 4 and, moreover, occurs primarily at the edge regions of the mirror element 2. Deformations at the edge regions are less critical for the optical behavior of the mirror element 2 than deformations in a central region of the mirror element 2.

[0101] The rib-shaped support element 10 which forms the ring makes a significant contribution to reducing the dynamic deformation of the first vibration mode.

[0102] Figures 8 and 9 show the dynamic deformation of the second oscillation mode, wherein Figure 8 uses the comparative example without support structure and Figure 9 uses the first exemplary embodiment shown in Figure 3. The dynamic deformation for the second oscillation mode is reduced by a factor greater than 2. In particular, dynamic deformations in the center of the mirror element can be almost completely eliminated. The reduction in the dynamic deformations of the second oscillation mode is attributable to the support elements 11, 12, which form the ellipse and the straight bar. The suspension of the connecting element 6 at two opposite points of the mirror element 2 also contributes to reducing the dynamic deformation of the second oscillation mode. Figures 10 and 11 show a micromechanical mirror

[0103] 1 according to a second embodiment. Figure 10 shows a perspective view of the mirror 1 from below. Figure 11 shows a plan view of the underside of the mirror.

[0104] The micromechanical mirror 1 according to the second embodiment differs from the mirror 1 according to the first embodiment in the design of the support structure 4. The support structure 4 according to the second embodiment has only the rib-shaped support element 10, which forms the ring.

[0105] Compared to the first embodiment, the moment of inertia is increased less by the support structure 4 according to the second embodiment. The reason for this is that the omission of the straight and elliptical support elements 11, 12 provides less additional mass.

[0106] Figure 12 shows the dynamic deformation of the mirror element

[0107] 2 according to the second embodiment for the first oscillation mode and Figure 13 shows the dynamic deformation of the mirror element 2 according to the second embodiment for the second oscillation mode.

[0108] Compared to the deformation shown in Figure 6 for the first oscillation mode without a support structure, in the second embodiment the deformation for the first oscillation mode can be reduced by a factor greater than 2. Furthermore, the remaining deformation occurs mainly in the edge regions of the mirror element 2, where it has a less pronounced effect on the optical behavior of the mirror element 2 than a deformation in the central region.

[0109] Compared with the dynamic deformation of the mirror element 2 shown in Figure 8 without a support structure 4 for the second vibration mode, the second exemplary embodiment only achieves a reduction in the dynamic deformation of approximately 35%. A strong deformation occurs in the center of the mirror element 2. The reason for this is that in the second exemplary embodiment no support elements are provided in the center of the mirror element 2. Therefore, although the support structure 4 according to the second exemplary embodiment is well suited to damping dynamic deformations resulting from the first vibration mode, the reduction of dynamic deformations resulting from the second vibration mode is inadequate.

[0110] An advantage of the second embodiment is that the moments of inertia for the two vibration modes are changed less than in the first embodiment. The reason for this is that the support structure 4 has a lower mass in the second embodiment.

[0111] Figures 14 and 15 show a micromechanical mirror 1 according to a third embodiment. Figure 15 shows a section of the underside of the mirror.

[0112] According to the third embodiment, the support structure 4 has a rib-shaped support element 10 that forms a ring and is designed like the annular support element 10 of the first and second embodiments. In addition, the support structure has rib-shaped support elements 13 that form straight beams. These straight beams form a regular lattice structure with triangular cells. The lattice structure is arranged throughout the interior of the annular support element.

[0113] Figure 16 shows the dynamic deformation of this exemplary embodiment for the first oscillation mode and Figure 14 shows the dynamic deformation of this exemplary embodiment for the second oscillation mode. Compared to a mirror element 2 without a support structure 4, the dynamic deformation for the first oscillation mode can be reduced by a factor of greater than 3, with deformations occurring mainly in the edge regions of the mirror element 2. This effect is due in particular to the annular support element 10. Compared to a mirror element without a support structure, the deformation of the second oscillation mode can be reduced by a factor of approximately 2. In this case, deformations in the center of the mirror element 2 in particular can be almost completely eliminated. This reduction in deformation is due in particular to the grating structure formed in the center of the mirror element.

[0114] Figures 18 and 19 show a mirror 1 according to a fourth embodiment. Figure 19 shows a section of the underside of the mirror.

[0115] The support structure 4 of the fourth embodiment also has the rib-shaped support element 10, which forms a ring arranged in the edge region of the mirror element. In addition, the support structure 4 of the fourth embodiment has rib-shaped support elements 14 that form a plurality of rectangles. The rectangles are dimensioned such that their corner points lie on the ring. The rectangles are rotated relative to one another. In the embodiment shown in Figures 18 and 19, a total of three rectangles rotated relative to one another are formed inside the ring.

[0116] Figure 20 shows the dynamic deformation in the first oscillation mode for the fourth exemplary embodiment, and Figure 21 shows the dynamic deformation of the fourth exemplary embodiment for the second oscillation mode. In the first oscillation mode, the dynamic deformation is reduced by a factor of greater than 3 compared to a mirror 1 without a support structure 4. The remaining deformation occurs mainly at the edge regions of the mirror element 2. This effect is essentially due to the ring. The dynamic deformation of the second oscillation mode is reduced by a factor of approximately 2. The deformation in the center of the mirror element 2 is also almost completely eliminated. This reduction in the dynamic deformation is particularly due to the rectangular support elements 14.

[0117] Figures 22 and 23 show a micromechanical mirror 1 according to a fifth exemplary embodiment, with Figure 23 showing only a section. The support structure 4 according to the fifth exemplary embodiment also has a rib-shaped support element 10 which forms a ring near the edge region of the mirror element 2. In addition, the support structure 4 has four rib-shaped support elements 15 which each form an elliptical ring section and intersect at the center of the mirror element 2. The four elliptical ring sections are shaped identically to one another and are each rotated by 90° to one another.

[0118] Figure 24 shows the dynamic deformation of the first oscillation mode for the fifth embodiment, and Figure 25 shows the dynamic deformation of the fifth embodiment for the second oscillation mode. The deformation for the first oscillation mode is reduced by a factor of almost 3 compared to a mirror without a support structure, and the remaining deformation occurs mainly at the edge regions of the mirror element 2. Here, the annular support element 10 in particular plays a significant role in reducing the deformation. The dynamic deformation of the second oscillation mode is reduced by almost 40%. The deformation in the central region of the mirror element cannot be completely eliminated. This is because the support structure 4 of the fifth embodiment does not place sufficient mass in the center of the mirror element 2.

[0119] Figures 26 and 27 show a sixth embodiment of the mirror 1. The support structure 4 of the sixth embodiment has the annular support element 10 and four straight rib-shaped support elements 16. The straight rib-shaped support elements 16 all extend through the center of the mirror element 2 and are rotated by 45° relative to one another.

[0120] Figure 28 shows the dynamic deformation of the sixth exemplary embodiment for the first oscillation mode and Figure 29 for the second oscillation mode. The dynamic deformation of the first oscillation mode is reduced by a factor of almost 3. The remaining deformation occurs particularly in the edge regions of the mirror element 2. The reduction in the deformation in the first oscillation mode is particularly attributable to the annular support element 10. The deformation of the second oscillation mode is reduced by a factor of approximately 2. In particular, the deformation in the center of the mirror element 2 can be almost completely eliminated. This reduction in the deformation of the second oscillation mode is particularly attributable to the four straight support elements 16 which intersect at the center of the mirror element 2.

[0121] Figures 30 and 31 show a seventh exemplary embodiment of the mirror 1, with Figure 31 showing a detail. The support structure 4 of the seventh exemplary embodiment has the rib-shaped support element 10, which forms a ring, as well as four further rib-shaped support elements 17, which form four intersecting circles. Each of the circles touches the ring. In addition, the four circles intersect at the center of the mirror element 2.

[0122] Figures 32 and 33 show the dynamic deformation of the first and second vibration modes, respectively, for the seventh exemplary embodiment. The deformation of the first vibration mode is reduced by a factor of almost 3, with the remaining deformation occurring particularly in the edge regions of the mirror element 2. The support element 10, which forms the ring, is responsible for this. The deformation of the second vibration mode is reduced by more than 40%. The strong deformation in the central region of the mirror element 2 cannot be completely reduced.

[0123] Figures 34 and 35 show a mirror 1 according to an eighth embodiment, with Figure 35 showing a detail. The support structure 4 according to the eighth embodiment has the rib-shaped support element 10, which forms the ring near the edge of the mirror element. This ring is referred to as the outer ring.

[0124] Furthermore, the support structure has a further rib-shaped support element 18 which forms an inner ring. The inner ring and the outer ring are concentric, with their centers coinciding with the center of the mirror element. The radius of the inner ring is smaller than the radius of the outer ring. For example, the radius of the inner ring is between 20 and 90% of the radius of the outer ring. In addition, the support structure has six straight support elements 19 which radiate outwards from the center of the rings and are formed only between the inner and outer rings.

[0125] Figures 36 and 37 show the dynamic deformation of the mirror element 2 according to the eighth exemplary embodiment for the first and second oscillation modes, respectively. The deformation of the first oscillation mode is reduced by a factor of almost 3. The remaining deformation occurs mainly in the edge regions of the mirror element 2. The outer ring, in particular, is responsible for this reduction in deformation. The dynamic deformation of the first oscillation mode is reduced by more than 40%. However, the strong deformation in the central region of the mirror element 2 is not completely eliminated.

[0126] Figures 38 and 39 show a mirror according to a ninth exemplary embodiment, with Figure 39 showing a detail. The support structure 4 of the mirror according to the ninth exemplary embodiment has the rib-shaped support element 10, which forms a ring, and two straight rib-shaped support elements 16, which are formed inside the ring and intersect at the center of the circle.

[0127] Figures 40 and 41 show the dynamic deformation of the mirror element according to the ninth embodiment. The deformation of the first oscillation mode is reduced by a factor of almost 3, with the remaining deformation occurring mainly in the edge regions, and the outer ring being primarily responsible for this reduction. The deformation of the first oscillation mode is reduced by approximately 50%, although the strong deformation in the central region is not sufficiently reduced.

[0128] Figures 43 to 46 show the mirror in different stages of a first manufacturing process for the mirror.

[0129] Figure 43 shows the mirror 1 after the following steps have been completed. First, a multilayer silicon substrate is provided. The silicon substrate has a first silicon layer 20 and a second silicon layer 23, which are separated from each other by an etch stop layer 24.

[0130] Then, the first silicon layer 20 is structured, for example, by an etching process. In the process, the mirror element 2, the drive element 5, the frame 7, the torsion suspension 3, the connecting element 6, and the torsion springs 41, 42, 43 are structured. For the sake of simplicity, only the mirror element 2 and the frame 7 are shown in Figure 43. The etch stop layer 24 limits the etching process used for structuring.

[0131] Subsequently, a reflective layer 25 is applied to the top side of the first silicon layer 20 in the region of the mirror element 2 and a bond pad 26 is attached to the frame 7.

[0132] Figure 44 shows the mirror after further process steps, which will now be described. In the next process step, the second silicon layer 23 is structured from below, for example, using an etching process. In this process, the second silicon layer 23 beneath the mirror element 2 is almost completely removed, with only rib-shaped elements 10-19 remaining of the second silicon layer 23 beneath the mirror element 2, which form the support structure 4 in the finished mirror. The etch stop layer 24 limits this etching step.

[0133] In a further process step, a second wafer 27, in which a cavity 28 is formed, is arranged beneath the structured multilayer silicon substrate. The second wafer 27 is arranged such that the cavity 28 is arranged beneath the mirror element 2.

[0134] Figure 45 shows the mirror 1 after a further process step in which the multilayer silicon substrate and the second wafer 27 are connected to one another.

[0135] Figure 46 shows the finished mirror 1. In a final process step, the mirror 1 is hermetically encapsulated. For this purpose, a glass cap 29 can be attached to the edge by bonding or gluing, for example. The glass cap 29 can be hemispherical.

[0136] Figure 47 shows an alternative to the mirror shown in Figure 46, in which a glass cap 29 with an oblique window was attached to the edge.

[0137] Alternatively, the mirror can be glued in another package, as shown in Figure 48.

[0138] Figures 49 to 53 show an alternative manufacturing process. This involves using a so-called double SOI wafer, which has three superimposed silicon layers 20, 23, 30, each separated from each other by an etch stop layer 24. In the first process step, as shown in Figure 49, the first silicon layer 20 is structured. In this process, the mirror element 2, the drive element 5, the frame 7, the torsion suspension 3, the connecting element 6, and the torsion springs 41, 42, 43 are structured.

[0139] Figure 50 shows the wafer after further process steps. In the further process diagram, the third silicon layer 30 is structured and a cavity is formed under the mirror element 2.

[0140] Figure 51 shows the mirror 1 after a further process step in which the second silicon layer 23 is etched. This creates the support structure 4 and a cavity beneath the mirror element 2.

[0141] Figure 52 shows the mirror after a further process step in which the mirror is bonded to a second wafer 27. In contrast to the process shown in Figures 43 to

[0142] 46, no cavity needs to be formed in the second wafer 27.

[0143] Figure 53 shows the finished mirror, with a dome-shaped glass cap 29 being applied in a final process step. Alternatively, the mirrors shown in Figures 47 and 48 could also be formed. In an alternative process, the mirror could be glued to a wafer instead of being bonded to it.

[0144] Figures 54 to 57 show a third manufacturing method in which a silicon wafer without an etch stop layer 24 is used. The method steps correspond to those shown in connection with the method steps shown in Figures 43 to 46. However, etch stop layers are omitted in the third manufacturing method. As a result, the mirror cannot be manufactured with the same precision as is possible in the first and second methods.

[0145] Figure 58 shows the finished mirror 1 in a perspective view, which is hermetically encapsulated under a glass cap 29.

[0146] Reference symbol list

[0147] 1 microelectromechanical mirror

[0148] 2 mirror elements

[0149] 3 Torsion suspension

[0150] 4 Support structure

[0151] 5 Drive element

[0152] 6 Connecting element

[0153] 7 frames

[0154] 9 Sensor element

[0155] 10 Support element (ring-shaped, outer ring)

[0156] 11 Support element (straight, beam through center)

[0157] 12 Support element (ellipse)

[0158] 13 Support element (lattice structure)

[0159] 14 Support element (rectangle)

[0160] 15 Support element (elliptical sections)

[0161] 16 Support element (straight)

[0162] 17 Support element (circles)

[0163] 18 Support element (ring-shaped, inner ring)

[0164] 19 Support element (radial)

[0165] 20 first silicon layer

[0166] 21 Top of the mirror element

[0167] 22 Underside of the mirror element

[0168] 23 second silicon layer

[0169] 24 Etch stop layer

[0170] 25 reflective layer

[0171] 26 Bondpad

[0172] 27 second wafer

[0173] 28 cavity

[0174] 29 Glass cap

[0175] 30 third silicon layer

[0176] 31 long axis of the torsion suspension

[0177] 32 short axis of the torsion suspension 41 first torsion spring elements

[0178] 42 second torsion spring elements

[0179] 43 third torsion spring elements 52 second electrode

[0180] 521a first control area

[0181] 521b first control area

[0182] 522a second control area

[0183] 522b second control area 61 suspension points of the connecting element

[0184] 62 segments of the connecting element

[0185] B Width

[0186] H Height

Claims

Patent claims 1. Microelectromechanical mirror (1) comprising - a mirror element (2) having a planar upper side (21) and a lower side (22) arranged opposite to the planar upper side (21), and - a support structure (4) arranged on the underside (22) of the mirror element (2).

2. Microelectromechanical mirror (1) according to the preceding claim, wherein the support structure has rib-shaped support elements (10-19).

3. Microelectromechanical mirror (1) according to claim 2, wherein the rib-shaped support elements (10-19) have a width (B) and a height (H), wherein the height (H) of the rib-shaped support elements (10-19) is an extension of the rib-shaped support elements (10-19) in the direction of the surface normal of the underside (22) which points away from the top side (21), wherein the width (B) of the rib-shaped support elements (10-19) indicates a minimum extension of the rib-shaped support elements (10-19) in a direction which is perpendicular to the height (H), wherein the height (H) is at least three times as large as the width (B) of the rib-shaped support elements (10-19).

4. Microelectromechanical mirror (1) according to one of claims 2 or 3, wherein a width (B) and / or a height (H) of the rib-shaped support elements vary over the support structure (4).

5. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) comprises a rib-shaped support element (10) forming a ring that is concentric with the mirror element (2).

6. Microelectromechanical mirror (1) according to the preceding claim, wherein the support structure (4) has rib-shaped support elements (14) forming rectangles, the corner points of the rectangles lying on the ring.

7. Microelectromechanical mirror (1) according to one of claims 5 or 6, wherein the ring is an outer ring, wherein the support structure (4) has a rib-shaped support element (18) forming an inner ring which is concentric with the mirror element (2), wherein the inner ring has a smaller diameter than the outer ring, wherein the support structure (4) has rib-shaped support elements (19) which connect the inner and the outer ring and which point straight radially away from the center of the inner ring.

8. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) comprises a rib-shaped support element (11) which has a straight beam which runs along an axis around which the mirror element (2) oscillates during the torsional oscillation.

9. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) has a plurality of rib-shaped support elements (16), each forming a straight bar passing through a center point of the mirror element (2).

10. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) has a rib-shaped support element (12) which forms an ellipse whose center coincides with the center of the mirror element (2).

11. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) has rib-shaped support elements (13) which form a lattice structure.

12. Microelectromechanical mirror (1) according to claim 11, wherein the grid structure has triangular cells.

13. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) has rib-shaped support elements (15) which each form an elliptical section, the elliptical sections intersecting at the center of the mirror element (2).

14. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the support structure (4) comprises rib-shaped support elements (17) forming circles, the circles being located in the center of the mirror element (2) cut.

15. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the micromechanical mirror (1) has a drive element (5).

16. Microelectromechanical mirror (1) according to the preceding claim, wherein the drive element (5) comprises a piezoelectric drive element.

17. Microelectromechanical mirror (1) according to one of the Claims 15 to 16, wherein the mirror element (2) and the drive element (5) are formed as a one-piece component.

18. Microelectromechanical mirror (1) according to one of claims 15 to 17, wherein the mirror element (2) and the drive element (5) have a common substrate (8) which has a constant thickness.

19. Microelectromechanical mirror (1) according to one of claims 15 to 18, wherein the drive element (5) is designed to excite the mirror element (2) to oscillate.

20. Microelectromechanical mirror (1) according to the preceding claim, wherein the oscillation excitable by the drive element is a torsional oscillation.

21. Microelectromechanical mirror (1) according to one of the Claims 19 or 20, wherein the mirror element (2) undergoes a deformation during the oscillation, wherein an amplitude of the deformation over the planar Top side (21) of the mirror element (2) varies, wherein the support structure (4) is arranged at positions of the bottom side (22), the positions of the planar top side (21) where the amplitude of the deformation would be greater than an average amplitude of the deformation over the entire top side (21) of the mirror element (2) if no support structure (4) were arranged there.

22. Microelectromechanical mirror (1) according to one of claims 19 to 21, wherein the mirror element (2) undergoes a deformation during the oscillation, wherein an amplitude of the deformation varies over the planar upper side (21) of the mirror element (2), wherein the support structure (4) is arranged at least in places at a position at which an amplitude of a deformation of the mirror element (2) without the support structure (4) has a maximum.

23. Microelectromechanical mirror (1) according to one of the Claims 15 to 22, wherein the microelectromechanical mirror has a torsion suspension (3) which surrounds the mirror element (2) and is connected to the mirror element (2) via two first torsion spring elements (41), wherein the drive element (5) has a piezoelectric drive ring which surrounds the torsion suspension (3) and is connected to the torsion suspension (3) via two second torsion spring elements (42).

24. Microelectromechanical mirror (1) according to the preceding claim, wherein the torsion suspension (3) has an elongated shape with a long axis (31) and a short axis (32) perpendicular thereto, wherein the first torsion spring elements (41) are arranged along the long axis (31), and the second torsion spring elements (42) are arranged along the short axis (32).

25. Microelectromechanical mirror (1) according to one of claims 15 to 24, wherein the micromechanical mirror (1) has a frame (7) which surrounds the drive element (5) and which is connected to the drive element (5) via two third torsion spring elements (43).

26. Microelectromechanical mirror (1) according to one of claims 15 to 25, wherein the drive element (5) is designed to excite the mirror element (2) to a torsional oscillation which has a first oscillation mode along a first axis (31) and a second oscillation mode along a second axis (32), the second axis being perpendicular to the first axis.

27. Microelectromechanical mirror (1) according to one of the preceding claims, wherein the planar upper side (21) is reflective.

28. A method for operating a microelectromechanical mirror (1) according to one of claims 1 to 27, wherein two electrical alternating current signals are applied to the mirror, which excite the mirror element to oscillate in two oscillation modes.

29. Projection device (1000) comprising a laser light source (200) and a microelectromechanical mirror (1) according to one of claims 1 to 27.

30. Use of a microelectromechanical mirror (1) according to one of claims 1 to 27 for the projection of information onto a surface, for head-up displays, for matrix illumination, for LIDAR applications, for hologram projectors, for VR glasses, or for AR glasses.

31. A method for producing a micromechanical mirror according to one of claims 1 to 27, comprising the steps of: a. Providing a multilayer silicon wafer having a first silicon layer (20) and a second silicon layer (23), b. Structuring the first silicon layer (20) to form the mirror element (2), and c. Structured etching of the second silicon layer (23) to form the support structure (4).

32. The method of claim 31, further comprising the step of: d. bonding or gluing the multilayer silicon wafer to a second wafer (27).

33. The method according to claim 31 or 32, wherein the wafer provided in step a. has a third silicon layer (30) arranged on a side of the second silicon layer (23) facing away from the first silicon layer (20), wherein before step c. the third silicon layer (30) is etched so that only a frame remains of the third silicon layer (30), which frame completely encloses the mirror element (2).

34. The method according to any one of claims 31 to 33, wherein the wafer provided in step a. has an etch stop layer (24) which, during the structuring in step b. and during the etching in step c., effects a limitation of the respective etching process.

35. A method according to any one of claims 31 to 34, wherein the method further comprises the step of: - Determining the positions at which the mirror element (2) has the greatest deformation at a experiences torsional vibration, whereby the supporting structure (4) in step c. to the previously determined Positions are formed at which the mirror element (2) experiences the greatest deformation during torsional oscillation.

36. Method for producing a micromechanical Mirror according to one of claims 1 to 27, comprising the steps: i. producing the support structure (4) from a silicon wafer in an etching process, ii. bonding a planar wafer to the support structure (4), iii. applying a reflective layer to the planar wafer, iv. applying the drive element (5) to the planar wafer, and v. structuring the planar wafer to form the mirror element (2).

Images