Method for producing a layer structure for a MEMS device, and MEMS device comprising such a layer structure

Abstract

The invention relates to a method for producing a layer structure for a MEMS device, to a layer structure which is produced using the method, and to a MEMS device (200) which comprises such a layer structure. For the layer structure or the MEMS device (200), a starting substrate which forms the mechanically active functional layer (10) is used during the production process for example, wherein the mechanically active functional layer (10) comprises a ferroelectric and / or piezoelectric material.

Description

[0001] Method for producing a layered structure for a MEMS device and MEMS device having such a layered structure

[0002] Description

[0003] The present disclosure relates to a method for manufacturing a layer structure for a MEMS device, a layer structure for a MEMS device, and a MEMS device comprising such a layer structure.

[0004] background

[0005] A generic method for producing a layer structure for a MEMS device, in particular a piezoelectrically driven MEMS device, as well as a generic layer structure for a MEMS device and a generic MEMS device comprising such a layer structure are known, for example, from US 2009 / 0185253 A1.

[0006] In the piezoelectrically driven MEMS devices known in the prior art, e.g. according to US 2009 / 0185253 A1, the mechanically active functional layer (often referred to as device layer) of the layer structure of the MEMS (micro-electro-mechanical system) is usually formed by a supporting, non-piezoelectric layer (e.g. silicon), in which the movable or oscillating components, such as mirror-supporting support elements and the holding spring structure, are structured, e.g. by so-called high-rate etching or deep reactive ion etching (DRIE for short).

[0007] In the manufacturing process for the layered structure, piezoelectric material is typically applied or deposited onto the supporting functional layer. This results in a layered structure (also called a MEMS wafer), in which the piezoelectric material must be applied to the future mechanically movable structure (e.g., silicon) of the functional layer through additional processing steps during the manufacturing process. It must then be removed locally for structuring, e.g., using photolithographic masks and etching processes (e.g., with a subsequent etching of the areas unprotected by the photoresist of the photolithographic mask).

[0008] All process steps are associated with costs and time. Furthermore, the growth of the ferroelectric / piezoelectric layers depends on the respective deposition process and the respective growth substrate, resulting in manufacturing-related variations as well as integration-related limitations, which also affect the resulting piezoelectric coefficients of the driving piezoelectric layer.

[0009] In addition, the layer thicknesses of the ferro- / piezoelectric layers applied by deposition are limited (typically to approx. 0.5 to 5 pm), and thus the generation of forces or torques is limited as well as the applied electrical drive voltage (breakdown field strength typically approx. 1-2 MV / cm).

[0010] In view of the disadvantages described above, it is an object of the present disclosure, starting from the prior art described above, to provide an improved method for producing a layer structure for a MEMS device, in particular with cost and / or time savings and / or improved properties of the layer structure produced.

[0011] Summary

[0012] The present disclosure relates to a method for producing a layer structure for a MEMS device, a layer structure produced by the method, and a MEMS device comprising the layer structure, particularly preferably a vacuum-packed MEMS mirror device.

[0013] In particular, to achieve the above-mentioned object, a method for producing a layer structure for a MEMS device and a layer structure produced by the method are proposed according to the independent claims, as well as a MEMS device comprising the layer structure, particularly preferably a vacuum-packed MEMS mirror device. The dependent claims relate to some exemplary preferred embodiments. According to a first aspect, in some embodiments, a method for producing a layer structure for a MEMS device, in particular a MEMS mirror device or a vacuum-packed MEMS mirror device, is proposed.

[0014] The method for producing a layer structure for a MEMS device comprises, for example, providing a starting substrate which, for example, comprises at least one functional layer (ie, for example, one or more functional layers), and / or structuring the at least one functional layer of the starting substrate.

[0015] The structuring of the at least one functional layer can preferably be carried out to form one or more movable elements of the MEMS device in the at least one functional layer and / or to form a spring structure, which preferably holds the one or more movable elements of the MEMS device, in the at least one functional layer.

[0016] In preferred embodiments, the at least one functional layer of the starting substrate may comprise ferroelectric and / or piezoelectric material.

[0017] Among other things, some embodiments are based on the idea that, for example, instead of a silicon substrate, a substrate comprising ferroelectric and / or piezoelectric material can be used as the starting substrate, and in particular, it can comprise at least one functional layer comprising ferroelectric and / or piezoelectric material. In particular, in some embodiments, the starting substrate can preferably comprise one or more ferroelectric and / or piezoelectric layers or one or more functional layers made of ferroelectric and / or piezoelectric material.

[0018] In this way, numerous process steps can be saved, saving costs and time, especially since deposition processes, e.g. of a piezoelectric layer, can be avoided.

[0019] In addition, the ferro- and / or piezoelectric substrate can form at least one functional layer in which the movable elements of the MEMS and / or the spring structure holding them can later be formed.

[0020] The at least one functional layer can preferably form the mechanically active layer and, at the same time, act as an actuator and / or sensor to drive and / or detect the oscillating movements. In relation to a MEMS, “mechanically active” is to be understood in particular to mean that the mechanically active layer or the at least one mechanically active functional layer (device layer) of the MEMS layer structure preferably forms the layer which, according to its structuring, is designed or configured to execute a one-dimensional or two-dimensional oscillating movement, or in such a way that one or more structures or bodies formed in the mechanically active layer or mechanically active functional layer can execute a one-dimensional or two-dimensional oscillating movement (e.g. about an oscillation / torsion axis or about two preferably transverse orin particular oscillation / torsion axes that are perpendicular to one another, e.g. via springs of a spring structure, e.g. with bending springs, torsion springs and / or meander springs, in particular e.g. for Lissajous scanning movements or preferably resonant Lissajous scanning movements).

[0021] Preferably, the holding and / or spring structure for the movable structures or bodies of the mechanically active layer or mechanically active functional layer can also be formed in this mechanically active layer or mechanically active functional layer.

[0022] In some embodiments, the holding and / or spring structure may comprise springs, particularly preferably bending springs, meander springs and / or torsion springs, which may preferably be designed to hold one or more movable structures or bodies of the mechanically active layer or mechanically active functional layer, e.g. in such a way that the movable structures or bodies can execute a respective oscillating rotational movement about one or more respective oscillation and / or torsion axes about the corresponding axis (e.g. torsional oscillations).

[0023] Furthermore, the formation of the mechanically active layer or mechanically active functional layer can preferably determine the resonance frequency or resonance frequencies of the MEMS, the deflection amplitudes and / or any dynamic deformations (e.g. in a holding and / or spring structure formed in the mechanically active layer or mechanically active functional layer or the formed structures or bodies, such as a mirror support element with a mirror plate).

[0024] In addition, the starting substrate or the one or more functional layers in the starting substrate can be provided in some embodiments as a ferro- and / or piezoelectric single crystal or polycrystal and thus optimal ferro- / piezoelectric properties with optimal ferro- / piezoelectric coefficients can be provided, which is not possible in conventional deposition processes due to process fluctuations and growth conditions.

[0025] In some preferred embodiments, the starting substrate comprising the at least one functional layer may be made of ferroelectric and / or piezoelectric material.

[0026] In some preferred embodiments, one or more functional layers of the starting substrate may consist of ferroelectric and / or piezoelectric material.

[0027] Preferably, the starting substrate comprising the at least one functional layer may comprise one or more piezoelectric layers made of ferro- and / or piezoelectric material, in particular one or more functional layers made of ferro- and / or piezoelectric material.

[0028] In some preferred embodiments, the starting substrate comprising the at least one functional layer and / or the at least one functional layer of the starting substrate may comprise a single crystal of a ferro- and / or piezoelectric material and / or consist of a single crystal of a ferro- and / or piezoelectric material.

[0029] In further preferred embodiments, the starting substrate comprising the at least one functional layer and / or at least one functional layer of the starting substrate may comprise a polycrystal of a ferro- and / or piezoelectric material and / or consist of a polycrystal of a ferro- and / or piezoelectric material.

[0030] In addition, in embodiments with multiple functional layers in the starting substrate, one or more functional layers of the starting substrate may comprise a single crystal of a ferro- and / or piezoelectric material and / or consist of a single crystal of a ferro- and / or piezoelectric material, wherein one or more further functional layers of the starting substrate may comprise a polycrystal of a ferro- and / or piezoelectric material and / or consist of a polycrystal of a ferro- and / or piezoelectric material.

[0031] Particularly preferably, the starting substrate is not a silicon substrate, and preferably, the starting substrate does not comprise silicon or a functional layer comprising silicon. In some preferred embodiments, the ferroelectric and / or piezoelectric material may comprise aluminum nitride (AlN), aluminum scandium nitride (AlScN), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), lead zirconate titanate (PZT), niobium-doped PZT (PZT-Nb), and / or quartz.

[0032] In some embodiments, the starting substrate comprising the at least one functional layer and / or at least one functional layer of the starting substrate may comprise an at least partially amorphous ferroelectric and / or piezoelectric material and / or may consist of an at least partially amorphous ferroelectric and / or piezoelectric material.

[0033] In this case, the at least partially amorphous (e.g. (partially) amorphous) ferro- and / or piezoelectric material can, for example, comprise PVDF (polyvinylidene fluoride (CF2-CH2)n) or consist of PVDF.

[0034] In some embodiments with multiple functional layers in the starting substrate, the starting substrate can be provided such that the starting substrate comprises, for example, at least one functional layer comprising or consisting of a ferro- and / or piezoelectric single crystal, at least one functional layer comprising or consisting of a ferro- and / or piezoelectric polycrystal, and / or at least one functional layer comprising or consisting of an at least partially amorphous ferro- and / or piezoelectric material.

[0035] In some preferred embodiments, a layer thickness of the at least one functional layer of the starting substrate, which comprises ferro- and / or piezoelectric material, can be substantially greater than or equal to 50 pm, in particular substantially greater than or equal to 100 pm, and / or substantially less than or equal to 1 mm.

[0036] Particularly preferably, in embodiments with several functional layers comprising ferroelectric and / or piezoelectric material, the layer thickness of each functional layer is preferably substantially greater than or equal to 50 pm, particularly preferably substantially greater than or equal to 100 pm, and / or substantially less than or equal to 1 mm

[0037] In some preferred embodiments, the method may further comprise: applying and / or providing electrically conductive electrode layers on respective opposite sides (e.g. on the front and back) of the at least one functional layer (e.g. already in the starting substrate between adjacent functional layers of the starting substrate if the starting substrate comprises more than one ferro- and / or piezoelectric functional layer), and / or structuring the electrode layers to form structured electrode surfaces on respective opposite sides (e.g. on the front and back) of the at least one functional layer.

[0038] In some preferred embodiments, a mirror of the MEMS device can be formed during the structuring of one of the electrode layers, particularly preferably during the structuring of an outer electrode layer or during the structuring of the upper or front-side electrode layer.

[0039] In further embodiments, an additional mirror layer can also be applied to form a mirror of the MEMS device. The mirror layer can comprise or consist of metal, e.g., aluminum. Alternatively or additionally, depending on the application area or wavelength range, an electrode and / or mirror layer made of gold, platinum, or silver can be used. For example, a mirror layer made of a more expensive metal, such as gold, platinum, and / or silver, can be applied to an electrode layer made of a less expensive metal, e.g., aluminum.

[0040] In some preferred embodiments, during the structuring of the at least one functional layer of the starting substrate, a mirror carrier element can be formed in the at least one functional layer, wherein particularly preferably a mirror (e.g. the mirror mentioned above) can be arranged and / or formed on the mirror carrier element.

[0041] In some preferred embodiments, in particular when structuring the at least one functional layer, a spring structure that holds the mirror support element with mirror can be formed in the at least one functional layer, in particular in some embodiments preferably such that the mirror support element with mirror is held so as to be able to swing about one or two axes, in particular preferably oscillation and / or torsion axes, e.g. by means of bending springs, torsion springs and / or meander springs.

[0042] In some embodiments, the spring structure may comprise springs, particularly preferably meander springs, spiral springs, and / or torsion springs, which are preferably designed to hold the mirror support element in such a way that the mirror support element can perform an oscillating rotational movement about the respective oscillation and / or torsion axis (e.g., torsional oscillations). In embodiments with two axes, particularly two oscillation and / or torsion axes, the mirror support element with mirror and / or the spring structure is particularly preferably designed for a two-dimensional Lissajous scanning movement or preferably a resonant two-dimensional Lissajous scanning movement of the mirror support element with mirror.

[0043] In some preferred embodiments, the conductive electrode layers for electrical contacting may be formed on opposite sides of the at least one functional layer.

[0044] In other preferred embodiments, one of the electrode layers (e.g. a second electrode layer) can be guided by means of a through-plating in a region, particularly preferably in a central and / or lateral region, of the at least one functional layer to the side of the other (first) electrode layer, preferably in such a way that the conductive (first and second) electrode layers for electrical contacting can be formed on the same side of the at least one functional layer.

[0045] Particularly preferably, at least a second electrode layer of the conductive electrode layers can be guided by means of a through-plating in a region of the at least one functional layer from a second side of the at least one functional layer to a first side of the at least one functional layer, on which a first electrode layer of the conductive electrode layers is arranged.

[0046] Particularly preferably, at least the first electrode layer and the second electrode layer can be designed by means of the through-plating of the second electrode layer to provide electrical contact between the first and second electrode layers on the same first side of the functional layer.

[0047] For example, in some preferred embodiments, the (second) electrode layer located on a rear side of the at least one functional layer can be guided by means of a through-plating in a region, in particular in a central or lateral region, of the at least one functional layer to the front side, on which the other (first) electrode layer is applied, preferably in such a way that the conductive (first and second) electrode layers can be designed for electrical contact on the front side of the at least one functional layer, in that the contacting of the (second) electrode layer applied on the rear side of the at least one functional layer can preferably also take place on the front side.

[0048] In some preferred embodiments, the starting substrate may comprise one (e.g., exactly one) ferro- and / or piezoelectric functional layer.

[0049] In some preferred embodiments, the starting substrate may also comprise several ferro- and / or piezoelectric functional layers.

[0050] For example, the starting substrate can comprise two ferroelectric and / or piezoelectric functional layers, particularly preferably with an intermediate (second) electrode layer. Corresponding (first) electrode layers can be arranged at the top and bottom (outside).

[0051] Furthermore, the starting substrate can comprise, for example, three or more ferro- and / or piezoelectric functional layers, wherein a respective electrode layer can preferably be arranged between adjacent ferro- and / or piezoelectric functional layers, particularly preferably such that one, several or each ferro- and / or piezoelectric functional layer is arranged between two corresponding (first and second) electrode layers.

[0052] According to a second aspect, in some embodiments, a layer structure is further proposed, which can preferably be produced in particular by means of the method according to at least one of the above embodiments.

[0053] In some preferred embodiments, the layer structure may comprise: at least one structured functional layer, in which preferably one or more movable elements of the MEMS device and / or a spring structure that holds the one or more movable elements of the MEMS device may be formed.

[0054] The movable element(s) may, in particular in some embodiments, comprise a mirror carrier element on which, for example, a mirror plate and / or mirror layer may be applied, in particular for reflecting electromagnetic radiation, particularly preferably light in the visible and / or infrared range.

[0055] In some preferred embodiments, the at least one functional layer may comprise ferroelectric and / or piezoelectric material. According to a third aspect, some embodiments further propose a MEMS device, in particular a MEMS mirror device or a vacuum-packed MEMS mirror device, comprising a layer structure produced by the method according to at least one of the preceding embodiments.

[0056] In operation, such MEMS devices can be configured according to some embodiments for periodic movements or oscillations in the frequency range from approximately 1 Hz up to the kHz range, in embodiments preferably for frequencies substantially less than or equal to 200 kHz and particularly preferably for frequencies substantially less than or equal to 100 kHz.

[0057] This distinguishes such MEMS devices, among other things, in terms of application from so-called quartz crystal devices, which are designed for the frequency range in the MHz range.

[0058] Further aspects and embodiments as well as advantages and more specific implementation possibilities of the aspects and features described above can be found in the following descriptions and explanations of the attached figures, which are not to be construed as limiting in any way.

[0059] Short description of the characters

[0060] Fig. 1A shows an exemplary sectional view of a layer structure for a MEMS device according to a background example,

[0061] Fig. 1B shows an exemplary sectional view of a MEMS device comprising the layer structure according to Fig. 1A,

[0062] Fig. 2 shows exemplary sectional views of the layer structure during a manufacturing process according to an exemplary manufacturing sequence of an embodiment,

[0063] Fig. 3 shows an exemplary functional schematic sectional view of a layer structure produced according to Fig. 2,

[0064] Fig. 4 shows an exemplary functional schematic sectional view of a layer structure according to a further embodiment, Fig. 5 shows an exemplary schematic sectional view of a MEMS device comprising the layer structure according to Fig. 3,

[0065] Fig. 6 shows an exemplary schematic sectional view of a MEMS device comprising the layer structure according to Fig. 4,

[0066] Fig. 7 shows exemplary sectional views of the layer structure during a manufacturing process according to an exemplary manufacturing sequence of a further embodiment,

[0067] Fig. 8 shows an exemplary schematic sectional view of a MEMS device comprising the layer structure according to Fig. 7,

[0068] Fig. 9 shows exemplary sectional views of the layer structure during a manufacturing process according to an exemplary manufacturing sequence of a further embodiment, and

[0069] Fig. 10 shows an exemplary schematic sectional view of a MEMS device comprising the layer structure according to Fig. 9.

[0070] Detailed description of the figures and preferred embodiments

[0071] Examples and embodiments of the present disclosure are described in detail below with reference to the accompanying figures. Identical or similar elements in the figures may be designated by the same reference numerals, although sometimes different reference numerals may be used.

[0072] It should be emphasized, however, that the subject matter of the present disclosure is in no way limited or restricted to the exemplary embodiments and their embodiment features described below, but further comprises modifications of the exemplary embodiments, in particular those which are encompassed by modifications of the features of the described examples or by combination of one or more of the features of the described examples within the scope of protection of the independent claims.

[0073] First, a background example is described below with reference to Figs. 1A and 1B, which is intended to facilitate understanding of the embodiments and advantages described below. However, the layer structure underlying Figs. 1A and 1B does not actually constitute publicly known prior art.

[0074] A generic layer structure from the state of the art as well as a corresponding manufacturing process can be found, for example, in US 2009 / 0185253 A1.

[0075] Even if the following description with reference to Figs. 1A and 1B refers to a background example, any described technical details and / or features of the method, the manufacturing sequence, the layer structure and in particular of individual steps and / or layers of the layer structure may also relate to corresponding details and / or features of the embodiments described below, unless a difference is explicitly pointed out.

[0076] Fig. 1A shows an exemplary cross-sectional view of a layer structure for a MEMS device according to a background example. Fig. 1B shows an exemplary cross-sectional view of a MEMS device comprising the layer structure according to the background example of Fig. 1A.

[0077] The layer structure comprises, for example, a substrate layer 1, a functional layer 3 which is applied to the substrate layer 1 (for example with an intermediate passivation layer 2), a piezoelectric layer 4 (e.g. with bottom electrode or counter electrode of the top electrode), which is applied to the functional layer 3 (for example with an intermediate passivation layer 2b), and an electrode layer 5 which is applied to the piezoelectric layer 4 or to regions of the functional layer 3.

[0078] The electrode layer 5 forms, on the one hand, the top electrode of the piezoelectric layer 4 and, on the other hand, forms, in one region (e.g., in the central region), a mirror 5a which is arranged on the functional layer 3.

[0079] In the following, explanations of the possible manufacturing process for a layer structure according to Fig. 1A are given as an example.

[0080] In the exemplary manufacturing process, respective passivation layers 2 and / or 2b (example intermediate layers) can be applied to the top and bottom sides (or front and back sides) of the substrate layer 1. Furthermore, the functional layer 3 (often referred to as the device layer) can be applied to the top side of the substrate layer 1, with, for example, a passivation layer 2 (intermediate layer) in between.

[0081] The substrate layer 1 can, for example, be formed from silicon or comprise silicon. In expedient embodiments, the substrate layer 1 can be provided, for example, as an SCS wafer (SCS, English: "single-crystal silicon," e.g., as a crystalline bulk silicon substrate).

[0082] Furthermore, the substrate layer can also be provided by means of an SOI wafer (SOI, English: "silicon-on-insulator"), which can already comprise the substrate layer 1 and, for example, also the functional layer 3 and / or the intermediate layer(s) 2.

[0083] Exemplary SOI wafers may comprise a handling wafer, which may, for example, consist of a crystalline bulk silicon substrate, followed, for example, by an intermediate layer (typically a silicon oxide, e.g., 100 - 2000 nm).

[0084] In other examples, the intermediate layers (e.g., intermediate layers 2 and / or 2b) may also consist of other (e.g., dielectric) layers, such as silicon nitride, silicon oxynitride, or aluminum oxide. In particular, different intermediate layers may consist of different materials.

[0085] Functional layer 3 (for example, with layer thicknesses of 5-300 μm) forms the layer that will later be mechanically effective. Functional layer 3 can be made of silicon, for example, or comprise silicon, and can also consist of a pure crystalline substrate (e.g., SCS, English: "single-crystal silicon") or be applied using epitaxial deposition processes, e.g., in polycrystalline form.

[0086] Furthermore, a piezoelectric layer 4 can be applied to the functional layer 3, for example with a further intermediate passivation layer 2b. In this case, an electrically conductive layer can preferably be provided on the underside of the piezoelectric layer 4, which can be used as the bottom electrode of the piezoelectric layer 4.

[0087] The piezoelectric layer 4 can preferably comprise or be formed from piezoelectric material that preferably has high piezoelectric and / or ferroelectric constants. For example, the piezoelectric layer 4 can comprise aluminum nitride (AlN), aluminum scandium nitride (AlScN), lead zirconate titanate (PZT), or niobium-doped PZT (PZT-Nb). The piezoelectric layer 4 can also comprise semi-crystalline polymer materials such as PVDF (polyvinylidene fluoride (CF2-CH2)n).

[0088] Furthermore, for example, the piezoelectric layer 4, which is applied on or above the functional layer 3, can be structured in the next step or in later process steps, particularly preferably by means of a wet and / or dry etching process.

[0089] The remaining regions of the piezoelectric layer 4 preferably define, in the later MEMS structure, the piezoelectric elements and / or drive and / or detection elements (e.g. actuator and / or sensor surfaces) for generating, driving, controlling and / or detecting the movements or vibrations of the movably held components or elements of the MEMS.

[0090] In a further step, for example, an electrode layer 5 can be applied to the piezoelectric layer 4 (which can optionally be structured beforehand).

[0091] In a further exemplary step, the electrode layer 5, which is applied on or above the piezoelectric layer 4, can be structured. In the exemplary step of structuring the electrode layer 5, for example, the desired structure of the upper electrode (top electrode) for the upper electrical contact of the piezoelectric layer 4 can be formed.

[0092] Furthermore, in the step of structuring the electrode layer 5, a mirror 5a (e.g. a mirror layer with a reflective surface) can be formed in a region, e.g. in the middle of the layer structure, for example by means of the material of the electrode layer 5.

[0093] In such examples, for example, the electrode layer can comprise metal, in particular aluminum, so that the surface of the electrode layer 5 already has a reflective surface and is suitable for forming the mirror 5a. For example, a top electrode layer deposited over the entire area, e.g. made of metal, in particular, for example, aluminum, can be structured using wet and / or dry chemical photolithographic steps, e.g. using spray coat lithography, using a lift-off process in which the lithography takes place before the metal deposition, or, for example, using positive photoresist lithography. In a further exemplary step, the functional layer 3 can be structured in regions 3a. In this case, in particular the mechanically active structures of the MEMS device can be formed in the functional layer. This includes, for example, the formation or exposure of the, for example,from central regions of the functional layer 3 formed mirror support element (here, for example, the region of the functional layer 3 below the mirror layer 5a) as well as any holding webs which can be formed from the functional layer 3 and which can act, for example, as a holding spring structure and which can hold the mirror support element oscillatable, for example, about one, two or more oscillation or torsion axes (e.g. about an oscillation / torsion axis or about two oscillation / torsion axes which are preferably transverse or, in particular, perpendicular to one another, e.g. via springs of the spring structure, e.g. with bending springs, torsion springs and / or meander springs, in particular, for example, for Lissajous scanning movements or preferably resonant Lissajous scanning movements).

[0094] In some embodiments, the spring structure may comprise springs, particularly preferably spiral springs, meander springs and / or torsion springs, which are preferably designed to hold the mirror support element in such a way that the mirror support element can perform an oscillating rotational movement about the respective oscillation and / or torsion axis about the corresponding axis (e.g. torsional oscillations).

[0095] In the prior art, so-called high-rate etching or deep reactive ion etching (DRIE) is typically used to pattern functional layer 3 to form the deep trenches in functional layer 3 (e.g., regions 3a). For example, deep reactive ion etching can be performed using a photolithography mask to pattern functional layer 3.

[0096] In a further exemplary step, the layer structure can be opened on the back to expose the functional layer 3 on the side (back) opposite the piezoelectric layer 4.

[0097] In a further exemplary step, the fabricated layer structure can be provided in a vacuum-packed MEMS device 100 according to Fig. 1B.

[0098] For example, the layer structure can be hermetically sealed from above with a translucent cover element 6 (e.g., a translucent dome element or a glass dome) and / or from below with a base element or base body element 7 under a vacuum atmosphere (e.g., vacuum encapsulation). In further embodiments, differently shaped cover elements or 3D-shaped cover elements are also possible (e.g., square or planar, e.g., an angled window or a planar window). The material of the cover elements is preferably translucent, e.g., made of glass or other optically transparent materials (e.g., approx. 400-2500 nm), such as borosilicate glass (e.g., Borofloat® BF33 from SCHOTT).

[0099] Thus, a vacuum-packed (or vacuum-encapsulated) MEMS mirror device 100 (e.g., a MEMS mirror scanner) comprising the fabricated layer structure can be provided with a piezoelectrically driven, deflectable, or controllable mirror 5a according to Fig. 1B.

[0100] Various exemplary embodiments are described below. Any details or exemplary features from the above examples, in particular regarding individual process steps and materials, may also apply analogously to the exemplary embodiments below, unless differences are explicitly pointed out. Furthermore, descriptions of details or exemplary features from the following exemplary embodiments, in particular regarding individual process steps and materials, may also apply analogously to other exemplary embodiments, unless differences are explicitly pointed out.

[0101] Fig. 2 shows exemplary sectional views of the layer structure during a manufacturing process according to an exemplary manufacturing sequence of an embodiment. In other possible embodiments, the sequence of the steps may also be different, steps may be omitted, and / or additional steps may be added.

[0102] A basic idea of ​​some embodiments is that the at least one functional layer, which later forms the mechanically active layer of the MEMS device, is formed from piezoelectric and / or ferroelectric material, in contrast to the above background example.

[0103] Thus, for example, the mechanically acting functional layer (i.e., in particular, the layer or layers that form the moving or oscillating elements of the MEMS) is already ferroelectrically and / or piezoelectrically formed, whereby this ferroelectrically and / or piezoelectrically formed functional layer also drives the amplitude and / or frequency of the movements or oscillations in the MEMS, functioning as an actuator, and / or detects them, functioning as a sensor. Thus, no further piezoelectric layer needs to be deposited on the functional layer.

[0104] This thus advantageously enables, by way of example, in contrast to the above background example and in particular also in contrast to the prior art, the elimination of many manufacturing steps, including various deposition steps, such as the deposition of the functional layer 3 and the deposition of the piezoelectric layer 4, as well as the rear opening or exposure of the functional layer 3 (e.g., by opening the rear of the substrate layer 1 in the above background example). Consequently, significant cost and time savings in the manufacturing process can be achieved.

[0105] Furthermore, in some embodiments, the starting substrate comprising the functional layer 3 can be provided as a single- or multi-layer piezoelectric single crystal or polycrystal. This enables improved or optimized piezoelectric properties with optimized piezoelectric coefficients, particularly compared to previously known methods in which the piezoelectric layer is deposited onto the starting substrate during the process.

[0106] In this case, a substrate layer 10 of a ferro- / piezoelectric material can be provided directly (e.g., instead of a layer structure with substrate layer 1 and functional layer 3), hereinafter referred to as piezoelectric functional layer 10; see, for example, Fig. 2 (i).

[0107] In some preferred embodiments, the piezoelectric functional layer 10 can be provided as a substrate of a ferro- / piezoelectric single crystal or polycrystal. However, the piezoelectric functional layer 10 can also be at least partially amorphous.

[0108] In some preferred embodiments, the layer thickness of the piezoelectric functional layer 10 can be substantially greater than or equal to 50 μm, preferably substantially greater than or equal to 100 μm, for example even substantially greater than or equal to 200 μm. In some embodiments, the piezoelectric functional layer 10 can be provided with a layer thickness of substantially greater than or equal to 100 μm and / or substantially less than or equal to 1 mm.

[0109] In some preferred embodiments, the piezoelectric functional layer 10 may comprise ferroelectric and / or piezoelectric material or be formed from ferroelectric and / or piezoelectric material, which preferably has high piezoelectric and / or ferroelectric constants. For example, the piezoelectric functional layer 10 may comprise aluminum nitride (AlN), aluminum scandium nitride (AlScN), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), lead zirconate titanate (PZT), niobium-doped PZT (PZT-Nb), and / or quartz, or may consist of one of the aforementioned materials.

[0110] In a further step, an electrically conductive layer, hereinafter referred to as the first electrode layer 11, can be applied or deposited on one side of the provided piezoelectric functional layer 10; see, for example, Fig. 2 (ii).

[0111] In a further step, the first electrode layer 11 can be structured; see, for example, Fig. 2 (iii). In exemplary embodiments, the upper (front) electrode surfaces for the deflection of the piezoelectric crystal or the piezoelectric functional layer 10 can be formed. In the exemplary step of structuring the first electrode layer 11, the desired structure of the upper electrode (top electrode) for the upper (front) electrical contacting of the piezoelectric functional layer 10 can be formed.

[0112] In some embodiments, e.g., in the production of a layered structure for a MEMS mirror device, one or more mirrors or mirror plates, such as mirror 111 in Fig. 2(iii), can also be machined in this step. Thus, in the step of structuring the first electrode layer 11, a mirror 111 (e.g., a mirror layer with a surface that reflects electromagnetic radiation) can be formed, for example, using the material of the electrode layer 11 in regions, e.g., in the center, of the layered structure.

[0113] In some embodiments, the first electrode layer 11 may comprise, for example, metal, in particular aluminum, so that the surface of the first electrode layer 11 may preferably already have a reflective surface and / or is suitable for forming the mirror 111.

[0114] For example, a top electrode layer deposited over the entire surface, e.g. made of metal, in particular, for example, aluminum, can be structured wet and / or dry chemically via photolithographic steps, e.g. by means of spray-coat lithography or alternatively via a lift-off process in which the lithography takes place before the metal deposition. In some embodiments, the electrode layer can also be applied by means of a shadow mask deposition. In further examples, it is possible to provide a non-reflective electrode layer (or, for example, a less well-reflective electrode layer, e.g., reflection substantially less than or equal to 60% in the relevant wavelength range) and / or a non-metallic electrode layer (e.g., doped polycrystalline silicon), wherein a further, for example, metallic, mirror layer (e.g., as a thin metal film) can then be applied in a further process step, e.g.,in the middle, to form a mirror.

[0115] In some preferred embodiments, the material of the (front-side) metallic electrode layer 11 or mirror layer 111 can be selected depending on the desired application for the respective wavelength range, in particular with very good reflection behavior in the wavelength range of the desired application (e.g. substantially greater than or equal to 85% in the relevant wavelength range), for example aluminum or silver for visible light (e.g. substantially at wavelengths of 400-700nm) or gold for infrared light or infrared radiation (e.g. substantially at wavelengths of 850-2000nm).

[0116] In a further step, a further electrically conductive layer, hereinafter referred to as the second electrode layer 12 (or counter electrode), can be applied or deposited on a side of the piezoelectric functional layer 10 that is opposite the first electrode layer 11 (i.e., for example, the rear side); see, for example, Fig. 2 (iv).

[0117] In some embodiments, the second electrode layer 12 may comprise metal, in particular aluminum, for example.

[0118] For example, a fully deposited bottom electrode layer, e.g., made of metal, in particular aluminum, can be structured using wet and / or dry chemical photolithographic steps, e.g., using spray-coat lithography or, alternatively, using a lift-off process in which the lithography is performed before the metal deposition. In some embodiments, the electrode layer can also be applied using shadow mask deposition.

[0119] In further examples, it is possible to provide a non-reflective or non-metallic electrode layer (e.g. doped polycrystalline silicon).

[0120] In a further step, the second electrode layer 12 can be structured; see, for example, Fig. 2 (v). In exemplary embodiments, the lower electrode surfaces for the deflection of the piezoelectric crystal or the piezoelectric functional layer 10 can be formed. In the exemplary step of structuring the second electrode layer 12, the desired structure of the underlying electrode (e.g., rear bottom electrode) for the lower electrical contacting of the piezoelectric functional layer 10 can be formed. The structured electrode layer 12 can thus be used as a counter electrode or counter electrode surface(s) to the electrodes of the first electrode layer 11, e.g., for the negative potential.

[0121] In a further step, the piezoelectric functional layer 3 can be structured; see, for example, Fig. 2 (vi). In this case, in particular the mechanically active structures of the MEMS device can be formed in the functional layer. This includes, for example, the formation or exposure of the mirror support element formed from (e.g., central) regions of the functional layer 10 (here, for example, the region of the functional layer 10 below the mirror layer 111) as well as the holding webs, which can be formed from the functional layer 10 and can act, for example, as a holding spring structure, and which can hold the mirror support element oscillatable, for example, about one, two or more oscillation or torsion axes (e.g., about one oscillation / torsion axis or about two oscillation / torsion axes that are preferably transverse or, in particular, perpendicular to one another (e.g., via springs of the spring structure, e.g.,with bending springs, torsion springs and / or meander springs), especially e.g. for Lissajous scanning movements or preferably resonant Lissajous scanning movements).

[0122] In some embodiments, the spring structure may comprise springs, particularly preferably spiral springs, meander springs and / or torsion springs, which are preferably designed to hold the mirror support element in such a way that the mirror support element can perform an oscillating rotational movement about the respective oscillation and / or torsion axis about the corresponding axis (e.g. torsional oscillations).

[0123] The structuring of the functional layer 10 can be performed using wet- and / or dry-chemical photolithographic steps. In this case, the structuring of the functional layer 10 can be performed together with the structuring of the second electrode layer 12 or at least with the same mask. In further embodiments, the structuring of the functional layer 10 can also be performed independently of the structuring of the second electrode layer 12 and / or with an additional photolithographic mask (e.g., with a subsequent etching of the areas unprotected by the photoresist of the photolithographic mask).

[0124] Other structuring methods are also possible in further embodiments, e.g. by means of laser ablation or also by means of the so-called LIDE method (Laser Induced Deep Etching), in which, for example, the crystal is chemically and physically modified in areas in which the crystal has been exposed or irradiated, in such a way that significantly higher etching rates occur there (e.g. in wet chemistry) than in those areas that have not been exposed or irradiated.

[0125] In the above embodiments, it can be provided, for example, that the electrode layers 11 and 12 are applied or deposited on respective sides (e.g. front and back) of the ferro- and / or piezoelectric functional layer 10.

[0126] In further embodiments, it is expediently possible to already provide a starting substrate which comprises the ferro- and / or piezoelectric functional layer 10 and in which, for example, one or both of the electrode layers 11 and 12 are already applied, e.g. glued to the functional layer 10, or as a laminated layer composite which already comprises the functional layer 10 and the first electrode layer 11 and / or the second electrode layer 12.

[0127] Fig. 3 shows an exemplary schematic functional sectional view of a layer structure, which is manufactured, for example, according to Fig. 2, in an exemplary electrical circuit for the drive.

[0128] On the right-hand side of Fig. 3, it is shown schematically by way of example that preferably at least one alternating voltage can be applied between at least one electrode of the first electrode layer 11 and at least one electrode of the second electrode layer 12, for example to control (and / or detect) the voltage generation or the voltage drop across the piezosubstrate or the piezoelectric functional layer 10. In further exemplary embodiments, multiple alternating voltage sources can also be used for different actuator surfaces (e.g. with different frequencies for oscillations in transverse or perpendicular torsion or oscillation axes (e.g. via springs of a spring structure, e.g. with bending springs, torsion springs and / or meander springs), e.g. for 2D Lissajous scanning movements or preferably resonant 2D Lissajous scanning movements of the mirror 111). The thin dashed arrows in Fig.3 schematically illustrates, by way of example, the controllable or excitable and / or detectable deflection of the piezoelectric functional layer 10, whereby an oscillation or oscillating movement of the mirror support element of the piezoelectric functional layer 10, which is arranged below the mirror 111, can be driven and / or detected. The thick dashed arrow in Fig. 3 schematically illustrates, by way of example, the reflection of a light beam on the (oscillating or moving) mirror 111.

[0129] Fig. 4 shows an exemplary schematic functional sectional view of a layer structure according to a further embodiment in a further exemplary electrical circuit for the drive.

[0130] In contrast to the example from Fig. 3, in further exemplary embodiments, as shown by way of example in Fig. 4, for example, a through-plating of the second (rear-side) electrode layer 12 can be carried out, in which at least in an exemplary lateral (or central) region of the functional layer 10, the second electrode layer 12 (for example on the left side in Fig. 4) or at least a section of the second electrode layer 12 (or an electrode section electrically connected to the second electrode layer 12) is guided to the side (front side) of the functional layer 10 on which the first electrode layer 11 is arranged. Such a through-plating can, for example, be carried out through or along one or more structured regions of the functional layer 10 (e.g. on one or more side walls of one or more structured regions or structured trenches of the functional layer 10).

[0131] This advantageously makes it possible to provide electrical contact between the electrodes of the first and second electrode layers 11 and 12 on the same side (front side) of the functional layer 10. This simplifies the complexity of the MEMS structure, and in particular the contacting and connection technology. For example, simple wire bonds can be placed on the front side and / or simple solder balls can be provided on the back side.

[0132] On the top side (front side), it is schematically shown by way of example that at least one alternating voltage can preferably be applied between at least one electrode of the first electrode layer 11 and at least one electrode of the second electrode layer 12 with exemplary contact on the top side (front side), for example to control (and / or detect) the voltage generation or the voltage drop across the piezosubstrate or the piezoelectric functional layer 10. In exemplary embodiments, several alternating voltage sources can also preferably be used here for different actuator surfaces (e.g. with different frequencies for oscillations in transverse or perpendicular torsion or oscillation axes (e.g. via springs of a spring structure, e.g. with bending springs, torsion springs and / or meander springs), e.g. for 2D Lissajous scanning movements or preferably resonant 2D Lissajous scanning movements of the mirror 111).

[0133] Fig. 5 shows an exemplary schematic sectional view of a MEMS device 200, which comprises, for example, the layer structure according to Fig. 3. Here, for example, the layer structure can be hermetically sealed from above with a translucent cover element 6 (e.g., a translucent dome element or a glass dome) and / or from below with a base element or base body element 7 under a vacuum atmosphere (e.g., vacuum encapsulation).

[0134] Fig. 6 shows an exemplary schematic sectional view of a MEMS device 300, which comprises, for example, the layer structure according to Fig. 4. Here, for example, the layer structure can be hermetically sealed from above with a translucent cover element 6 (e.g., a translucent dome element or a glass dome) and / or from below with a base element or base body element 7 under a vacuum atmosphere (e.g., vacuum encapsulation).

[0135] In further embodiments, differently shaped cover elements or 3D-shaped cover elements are also possible (e.g., square or planar, e.g., a slanted window or a planar window). The material of the cover elements is preferably translucent, e.g., glass or other optically transparent materials (e.g., approximately 400-2500 nm), such as borosilicate glass (e.g., Borofloat® BF33 from SCHOTT).

[0136] Consequently, by way of example, a vacuum-packed (or vacuum-encapsulated) MEMS mirror device 200 or 300 (e.g. a MEMS mirror scanner), which comprises the respectively manufactured layer structure, can be provided with piezoelectrically deflectable or controllable mirror 111, which can be configured, by way of example, for ID and / or 2D scanning movements of the mirror 111 (e.g. 2D scanning movements for Lissajous scans or preferably resonant 2D scanning movements for Lissajous scans, e.g. a bi-resonant mirror 111 with two resonant axes for Lissajous scans, e.g. via springs of a spring structure, e.g. with bending springs, torsion springs and / or meander springs). In Figs. 5 and 6 show an exemplary fixed clamping of the layer structure (in particular to hold the spring structures in the outer area which hold the mirror support element or the mirror 111), which is shown in Figs.3 and 4 is only shown schematically by way of example, provided by way of example by the attachment to the exemplary floor element or base body element 7.

[0137] Fig. 7 shows exemplary sectional views of the layer structure during a manufacturing process according to an exemplary manufacturing sequence of another embodiment. In other possible sequences, the order of the steps may also be different, steps may be omitted, and / or additional steps may be added.

[0138] While in the exemplary embodiments described above, the respective starting substrate is provided, for example, with a ferroelectric or piezoelectric functional layer 10, in contrast to the preceding exemplary embodiments, a starting substrate according to Fig. 7 (i) is now provided, which comprises, for example, two ferroelectric or piezoelectric functional layers 10a and 10b. These two ferroelectric or piezoelectric functional layers 10a and 10b (or the ferroelectric or piezoelectric layers 10a and 10b that form the functional layer) can comprise the same ferroelectric or piezoelectric material and / or different ferroelectric or piezoelectric materials.

[0139] By way of example, the starting substrate according to Fig. 7 (i) can also already be provided in such a way that a (second) electrode layer 12, e.g., a metallic electrode layer, is arranged between the two ferroelectric or piezoelectric functional layers 10a and 10b. By way of example, the starting substrate according to Fig. 7 (i) can be provided in some embodiments in such a way that the two ferroelectric or piezoelectric functional layers 10a and 10b and the (second) electrode layer 12 arranged therebetween, for example, are bonded or laminated.

[0140] On opposite outer sides (e.g., front and back) of the starting substrate according to Fig. 7 (i), respective (first) electrode layers 11a and 11b are arranged, for example. These (first) electrode layers 11a and 11b can, for example, either be applied to the starting substrate (e.g., by deposition processes) or, for example, can already be provided in the starting substrate (e.g., glued or laminated to the respective functional layer 10a / 10b). In the exemplary manufacturing method according to Fig. 7, the (first) electrode layer 11a located on top (on the front side) can also be structured (e.g., analogously to electrode layer 11 in Fig. 2 (iii)); see, for example, Fig. 7 (ii).

[0141] Thus, in the step of structuring the (first) electrode layer 11a, e.g. in the middle of the layer structure, a mirror 111 (e.g. mirror layer with a reflective surface) can be formed by means of the material of the electrode layer 11a.

[0142] In some embodiments, the (first) electrode layer 11a may, for example, comprise metal, in particular aluminum, so that the surface of the (first) electrode layer 11a, for example, already comprises a reflective surface and / or is suitable for forming the mirror 111.

[0143] In some preferred embodiments, the material of the metallic (first) electrode layer 11a or mirror layer 111 can be selected depending on the desired application for the respective wavelength range, in particular with very good reflection behavior in the wavelength range of the desired application, for example aluminum or silver for visible light (e.g. essentially at wavelengths of 400-700nm) or gold for infrared light or infrared radiation (e.g. essentially at wavelengths of 850-2000nm).

[0144] In the exemplary manufacturing method according to Fig. 7, the first ferroelectric or piezoelectric functional layer 10a can further be structured analogously to Fig. 2 (vi); see, for example, Fig. 7 (iii).

[0145] The (front-side) structuring of the ferroelectric or piezoelectric functional layer 10a can be performed using wet- and / or dry-chemical photolithographic steps. In some embodiments, the structuring of the ferroelectric or piezoelectric functional layer 10a can be performed together with the structuring of the electrode layer 12 or at least using the same mask.

[0146] In further embodiments, the structuring of the ferroelectric or piezoelectric functional layer 10a can be carried out independently of the structuring of the electrode layers 11a and / or 12 and / or with a further photolithographic mask (e.g., with a subsequent etching of the areas unprotected by the photoresist of the photolithographic mask). Other structuring methods are also possible in further embodiments, e.g., structuring by laser ablation or by the so-called LIDE method (Laser Induced Deep Etching). In the exemplary manufacturing method according to Fig. 7, the (first) electrode layer 11b located below (on the rear side) can also be structured; see, for example, Fig. 7 (iv). In some embodiments, the (first) electrode layer 11b can, for example, comprise metal, in particular aluminum.

[0147] In the exemplary manufacturing method according to Fig. 7, the second ferroelectric or piezoelectric functional layer 10b (analogous to the functional layer 10a) can also be structured; see, for example, Fig. 7 (v).

[0148] The (rear-side) structuring of the ferroelectric or piezoelectric functional layer 10b can be performed using wet- and / or dry-chemical photolithographic steps. In this case, the structuring of the ferroelectric or piezoelectric functional layer 10b can be performed simultaneously with the structuring of the electrode layer 12 or at least using the same mask.

[0149] In further embodiments, the structuring of the ferroelectric or piezoelectric functional layer 10b can be performed independently of the structuring of the electrode layers 11b and / or 12 and / or with an additional photolithographic mask (e.g., with a subsequent etching of the areas unprotected by the photoresist of the photolithographic mask). Other structuring methods are also possible in further embodiments, e.g., by laser ablation or by the so-called LIDE (Laser Induced Deep Etching) method.

[0150] In the exemplary manufacturing method according to Fig. 7, the (second) electrode layer 12 (counter electrode) can also be structured; see, for example, Fig. 7 (vi). In some embodiments, the (second) electrode layer 12 can comprise metal, in particular aluminum, for example.

[0151] In this case, by structuring the ferroelectric or piezoelectric functional layer(s), in particular by structuring the ferroelectric or piezoelectric functional layers 10a and 10b (and structuring the electrode layer 12), the mechanically effective structures of the MEMS device can be formed in the ferroelectric or piezoelectric functional layers 10a and 10b.

[0152] This includes, for example, the formation or exposure of the mirror support element formed from (e.g., central) regions of the ferroelectric or piezoelectric functional layers 10a and 10b (here, for example, the region under the mirror layer 111) as well as the holding webs, which can be formed from the functional layers 10a and 10b and can act, for example, as a holding spring structure, and which can, for example, hold the mirror support element oscillatable about one, two or more oscillation or torsion axes (e.g., about an oscillation / torsion axis or about two oscillation / torsion axes that are preferably transverse or, in particular, perpendicular to one another, e.g., via springs of the spring structure, e.g., with bending springs, torsion springs and / or meander springs, in particular, e.g., for Lissajous scanning movements or preferably resonant Lissajous scanning movements).

[0153] In some embodiments, the spring structure may comprise springs, particularly preferably spiral springs, meander springs and / or torsion springs, which are preferably designed to hold the mirror support element in such a way that the mirror support element can perform an oscillating rotational movement about the respective oscillation and / or torsion axis around the corresponding axis (e.g., torsional oscillations).

[0154] In some embodiments with two or more ferroelectric or piezoelectric functional layers, even greater deflections and / or even greater acting forces or torques can be advantageously enabled if required or desired depending on the application, compared to previous embodiments with one ferroelectric or piezoelectric functional layer. In further embodiments with two or more ferroelectric or piezoelectric functional layers, the drive voltage can advantageously be reduced if required or desired depending on the application, compared to previous embodiments with one ferroelectric or piezoelectric functional layer.

[0155] Preferably, one or more alternating voltages can be applied between the (first) electrode layer 11a and the (second) electrode layer 12 (counter electrode) and / or between the (first) electrode layer 11b and the (second) electrode layer 12 (counter electrode), wherein the alternating voltages applied to the (first) electrode layers 11a and 11b can be in phase or out of phase relative to one another, can be at the same or different frequency and / or can be at the same or different amplitude. In some embodiments, several alternating voltage sources can also be used for different actuator surfaces (e.g. with different frequencies for oscillations in transverse or perpendicular torsion or oscillation axes, e.g. via springs of a spring structure, e.g. with bending springs, torsion springs and / or meander springs, e.g.for 2D Lissajous scanning movements or, preferably, resonant 2D Lissajous scanning movements of the mirror 111). Fig. 8 shows an exemplary schematic sectional view of a MEMS device 400, which, by way of example, comprises the layer structure according to Fig. 7 (vi). Here, too, the layer structure can, by way of example, be hermetically sealed from above with a translucent cover element 6 (e.g., a translucent dome element or a glass dome) and / or from below with a base element or base body element 7 under a vacuum atmosphere (e.g., vacuum encapsulation).

[0156] In further embodiments, differently shaped cover elements or 3D-shaped cover elements are also possible (e.g., square or planar, e.g., a slanted window or a planar window). The material of the cover elements is preferably translucent, e.g., glass or other optically transparent materials (e.g., approximately 400-2500 nm), such as borosilicate glass (e.g., Borofloat® BF33 from SCHOTT).

[0157] Consequently, a vacuum-packed (or vacuum-encapsulated) MEMS mirror device 400 (e.g., a MEMS mirror scanner) comprising the manufactured layer structure can be provided, for example, with piezoelectrically deflectable or controllable mirror 111, which can be configured, for example, for ID and / or 2D scanning movements of the mirror 111 (e.g., 2D scanning movements or preferably resonant 2D scanning movements for Lissajous scans, e.g., a bi-resonant mirror 111 with two resonant axes for Lissajous scans, e.g., via springs of a spring structure, e.g., with bending springs, torsion springs, and / or meander springs).

[0158] Fig. 9 shows exemplary sectional views of the layer structure during a manufacturing process according to an exemplary manufacturing sequence of another embodiment. Only the exemplary starting substrate (see Fig. 9 (i)) and the exemplary finished layer structure (see Fig. 9 (ii)) are shown here. Any intermediate structuring steps of the functional and electrode layers can be carried out in various possible ways and sequences, analogous to the above embodiments.

[0159] By way of example, in contrast to the preceding embodiments, a starting substrate according to Fig. 9 (i) is now provided, which comprises, for example, three ferroelectric or piezoelectric functional layers 10a, 10b, and 10c. These three ferroelectric or piezoelectric functional layers 10a, 10b, and 10c (or the ferroelectric or piezoelectric layers 10a, 10b, and 10c that form the functional layer) can comprise the same ferroelectric or piezoelectric material and / or different ferroelectric or piezoelectric materials.

[0160] By way of example, the starting substrate according to Fig. 9 (i) can also already be provided in such a way that a respective electrode layer 11b (first electrode layer) or electrode layer 12a (second electrode layer), e.g., as metallic electrode layer(s), is arranged between respective adjacent ferroelectric or piezoelectric functional layers. By way of example, the starting substrate according to Fig. 9 (i) can be provided in some embodiments in such a way that the ferroelectric or piezoelectric functional layers 10a, 10b, and 10c and the (example of first and / or second) electrode layers 11b and 12a located therebetween are already bonded or laminated.

[0161] On opposite outer sides (e.g., front and back) of the starting substrate according to Fig. 9 (i), respective electrode layers 11a (first electrode layer) and 12b (second electrode layer) are arranged, for example. The electrode layers 11a and 12b can, for example, either be applied to the starting substrate (e.g., by deposition processes) or, for example, already be provided in the starting substrate (e.g., glued or laminated to the respective functional layer 10a / 10c).

[0162] The (second) electrode layers 12a and 12b each form, for example, the corresponding counterelectrodes to the respective (first) electrode layers 10a, 10b, and 10c, so that, for example, each ferroelectric or piezoelectric functional layer is arranged between a respective first electrode layer and a respective second electrode layer (corresponding counterelectrode). The electrode layers 12a and / or 12b can, for example, be structured analogously to the electrode layers 11a and / or 11b. In general, the electrode layers 11a and / or 12a and / or the electrode layers 11b and / or 12b do not need to be symmetrical.

[0163] In this case, by structuring the ferroelectric or piezoelectric functional layer(s), in particular by structuring the ferroelectric or piezoelectric functional layers 10a, 10b, and 10c (and, for example, also structuring the electrode layers 12a and 11b), the mechanically effective structures of the MEMS device can be formed in the ferroelectric or piezoelectric functional layers 10a, 10b, and 10c; see, for example, Fig. 9 (ii). This includes, for example, the formation or exposure of the mirror support element formed from (e.g. middle) regions of the ferro- or piezoelectric functional layers 10a, 10b and 10c (here, for example, the region under the mirror layer 111) as well as the holding webs, which can be formed from the functional layers 10a, 10b and 10c and can act, for example, as a holding spring structure, and which can, for example, keep the mirror support element oscillatable about one, two or more oscillation or torsion axes (e.g.about an oscillation / torsion axis or about two oscillation / torsion axes that are preferably transverse or, in particular, perpendicular to one another, e.g., via springs of the spring structure, e.g., with bending springs, torsion springs, and / or meander springs, in particular, e.g., for Lissajous scanning movements or, preferably, resonant Lissajous scanning movements). In general, the ferroelectric or piezoelectric functional layers 10a, 10b, and / or 10c do not have to be structured symmetrically.

[0164] In some embodiments, the spring structure may comprise springs, particularly preferably spiral springs, meander springs and / or torsion springs, which are preferably designed to hold the mirror support element in such a way that the mirror support element can perform an oscillating rotational movement about the respective oscillation and / or torsion axis about the corresponding axis (e.g. torsional oscillations).

[0165] The respective electrode layers 11a, 12a, 11b and / or 12b can, for example, consist of metal, preferably aluminum, or comprise metal, preferably aluminum, e.g. either of the same metal or of different metals.

[0166] In some preferred embodiments, the material of the metallic electrode layer 11a or mirror layer 111 can be selected depending on the desired application for the respective wavelength range, in particular with very good reflection behavior in the wavelength range of the desired application, for example aluminum or silver for visible light (e.g. essentially at wavelengths of 400-700nm) or gold for infrared light or infrared radiation (e.g. essentially at wavelengths of 850-2000nm).

[0167] Fig. 10 shows an exemplary schematic sectional view of a MEMS device 500, which, for example, comprises the layer structure according to Fig. 9 (ii). Here, too, the layer structure can be hermetically sealed from above with a translucent cover element 6 (e.g., a translucent dome element or a glass dome) and / or from below with a base element or base body element 7 under a vacuum atmosphere (e.g., vacuum encapsulation).

[0168] In further embodiments, differently shaped cover elements or 3D-shaped cover elements are also possible (e.g., square or planar, e.g., a slanted window or a planar window). The material of the cover elements is preferably translucent, e.g., glass or other optically transparent materials (e.g., approximately 400-2500 nm), such as borosilicate glass (e.g., Borofloat® BF33 from SCHOTT).

[0169] Consequently, a vacuum-packed (or vacuum-encapsulated) MEMS mirror device 500 (e.g., a MEMS mirror scanner) comprising the manufactured layer structure can be provided, for example, with piezoelectrically deflectable or controllable mirror 111, which can be configured, for example, for (preferably resonant) ID and / or 2D scanning movements of the mirror 111 (e.g., 2D scanning movements for Lissajous scans, e.g., a bi-resonant mirror 111 with two resonant axes for Lissajous scans, e.g., via springs of a spring structure, e.g., with bending springs, torsion springs, and / or meander springs).

[0170] In operation, such layer structures described above by way of example, with one, two, three, or more ferroelectric and / or piezoelectric functional layers, can be configured for a MEMS device or such MEMS devices according to some embodiments for periodic movements or oscillations in the frequency range from approximately 1 Hz up to the kHz range, in embodiments preferably for frequencies substantially less than or equal to 200 kHz and particularly preferably for frequencies substantially less than or equal to 100 kHz. This distinguishes such MEMS devices, among other things, in terms of application from so-called quartz crystal devices, which are configured for the frequency range in the MHz range.

[0171] The above embodiments are based in particular on the idea that, for example, instead of a silicon substrate, a substrate comprising ferroelectric and / or piezoelectric material can be used as the starting substrate, and in particular, comprises at least one functional layer comprising ferroelectric and / or piezoelectric material. In particular, in some embodiments, the starting substrate can preferably comprise one or more ferroelectric and / or piezoelectric layers or one or more functional layers made of ferroelectric and / or piezoelectric material.

[0172] This allows numerous process steps to be eliminated, saving time and money, especially since deposition processes, e.g., for a piezoelectric layer, can be avoided. Furthermore, the ferroelectric and / or piezoelectric substrate can form the at least one functional layer in which the movable elements of the MEMS and / or the spring structure holding them can later be formed. The at least one functional layer can preferably form both the mechanically active layer and, at the same time, act as an actuator and / or sensor to drive and / or detect the oscillating movements.

[0173] In relation to a MEMS, "mechanically effective" is to be understood here in particular to mean that the mechanically effective layer or the at least one mechanically effective functional layer (device layer) of the MEMS layer structure preferably forms the layer which, according to its structuring, is designed or configured to execute a one-dimensional or two-dimensional oscillatory movement, or in such a way that one or more structures or bodies formed in the mechanically effective layer or mechanically effective functional layer can execute a one-dimensional or two-dimensional oscillatory movement (e.g., about an oscillation / torsion axis or about two oscillation / torsion axes which are preferably transverse or, in particular, perpendicular to one another, e.g., via springs of a spring structure, e.g., with bending springs, torsion springs and / or meander springs, in particular, e.g., for Lissajous scanning movements or preferably resonant Lissajous scanning movements).

[0174] Preferably, the holding and / or spring structure for the movable structures or bodies of the mechanically active layer or mechanically active functional layer can also be formed in this mechanically active layer or mechanically active functional layer.

[0175] Furthermore, the formation of the mechanically active layer or mechanically active functional layer can preferably determine the resonance frequency or resonance frequencies of the MEMS, the deflection amplitudes and / or any dynamic deformations (e.g. in a holding and / or spring structure formed in the mechanically active layer or mechanically active functional layer or the formed structures or bodies, such as the mirror support element with the mirror plate 111).

[0176] Furthermore, the starting substrate or the one or more functional layers in the starting substrate in the embodiments described above can be provided as a ferro- and / or piezoelectric single crystal or polycrystal, thus providing optimal ferro- / piezoelectric properties with optimal ferro- / piezoelectric coefficients, which is not possible in conventional deposition processes due to process fluctuations and growth conditions. Furthermore, compared to the prior art, in which ferro- / piezoelectric layers are deposited on a silicon substrate, in some embodiments comparatively thicker ferro- / piezoelectric layers can be provided in the starting substrate, advantageously enabling higher force development.

[0177] In the embodiments described above, the starting substrate comprising the at least one functional layer can be made of ferroelectric and / or piezoelectric material. In the embodiments described above, one or more functional layers of the starting substrate can be made of ferroelectric and / or piezoelectric material. Preferably, the starting substrate comprising the at least one functional layer can comprise one or more piezoelectric layers made of ferroelectric and / or piezoelectric material, in particular one or more functional layers made of ferroelectric and / or piezoelectric material.

[0178] In the embodiments described above, the starting substrate comprising the at least one functional layer and / or the at least one functional layer of the starting substrate may comprise a single crystal of a ferroelectric and / or piezoelectric material and / or consist of a single crystal of a ferroelectric and / or piezoelectric material.

[0179] In the embodiments described above, the starting substrate comprising the at least one functional layer and / or at least one functional layer of the starting substrate may comprise a polycrystal of a ferro- and / or piezoelectric material and / or consist of a polycrystal of a ferro- and / or piezoelectric material.

[0180] Particularly preferably, the starting substrate is not a silicon substrate and preferably the starting substrate does not comprise any silicon or any functional layer comprising silicon.

[0181] In the embodiments described above, the ferro- and / or piezoelectric material may comprise aluminum nitride (AIN), aluminum scandium nitride (AlScN), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), lead zirconate titanate (PZT), niobium-doped PZT (PZT-Nb) and / or quartz.

[0182] In the exemplary embodiments described above, the starting substrate comprising the at least one functional layer and / or at least one functional layer of the starting substrate can comprise an at least partially amorphous ferroelectric and / or piezoelectric material and / or can consist of an at least partially amorphous ferroelectric and / or piezoelectric material. The (partially) at least partially amorphous (e.g., (partially) amorphous) ferroelectric and / or piezoelectric material can, for example, comprise PVDF (polyvinylidene fluoride (CF2-CH2)n) or consist of PVDF.

[0183] In the above-described embodiments with a plurality of functional layers in the starting substrate, the starting substrate can be provided such that the starting substrate comprises, for example, at least one functional layer which comprises or consists of a ferro- and / or piezoelectric single crystal, at least one functional layer which comprises or consists of a ferro- and / or piezoelectric polycrystal, and / or at least one functional layer which comprises or consists of an at least partially amorphous (e.g. (partially) amorphous) ferro- and / or piezoelectric material.

[0184] In the exemplary embodiments described above, a layer thickness of the at least one functional layer of the starting substrate comprising ferroelectric and / or piezoelectric material can be substantially greater than or equal to 50 μm, in particular substantially greater than or equal to 100 μm, and / or substantially less than or equal to 1 mm. Particularly preferably, in exemplary embodiments with multiple functional layers comprising ferroelectric and / or piezoelectric material, the layer thickness of each functional layer is preferably substantially greater than or equal to 50 μm, in particular preferably substantially greater than or equal to 100 μm, and / or substantially less than or equal to 1 mm.

[0185] In the exemplary embodiments described above, in particular when structuring the at least one functional layer, a spring structure which holds the mirror support element with mirror can be formed in the at least one functional layer, in particular in some exemplary embodiments preferably such that the mirror support element with mirror is held so as to be able to swing about one or two axes, in particular e.g. oscillation and / or torsion axes, e.g. via springs of a spring structure, e.g. with torsion springs and / or meander springs.

[0186] In some embodiments, the spring structure may comprise, for example, springs, particularly preferably spiral springs, meander springs and / or torsion springs, which are preferably designed to hold the mirror support element in such a way that the mirror support element can perform an oscillating rotational movement about the respective oscillation and / or torsion axis around the corresponding axis (e.g., torsional oscillations).

[0187] In embodiments with two axes, in particular oscillation and / or torsion axes, the mirror support element with mirror and / or the spring structure is particularly preferably designed for a (preferably resonant) two-dimensional Lissajous scanning movement of the mirror support element with mirror.

[0188] Embodiments of multilayer stack structures have been described above. It should be noted that such embodiments should not be construed as limiting the possibility of further intermediate layers being present in further embodiments. On the contrary, further layers and / or intermediate layers may be provided and / or described layers may be omitted in further embodiments.

[0189] It should be noted that only examples or exemplary embodiments of the present disclosure, as well as technical advantages, have been described above in detail with reference to the accompanying figures. However, the present disclosure is in no way limited or restricted to the exemplary embodiments described above and their design features or the described combinations thereof, but further encompasses modifications of the exemplary embodiments, in particular those encompassed by modifications of the features of the described examples or by combinations or partial combinations of individual or several of the features of the described examples within the scope of the independent claims.

[0190] List of reference symbols

[0191] 1 substrate layer

[0192] 2 passivation layer(s)

[0193] 2b Passivation layer

[0194] 3 Functional layer (device layer)

[0195] 3a Trenches or structured areas of the functional layer

[0196] 4 piezoelectric layer

[0197] 5 Electrode layer

[0198] 5a Mirror

[0199] 6 Cover element

[0200] 7 Floor element

[0201] 10 piezoelectric functional layer (device layer)

[0202] 10a first piezoelectric functional layer

[0203] 10b second piezoelectric functional layer

[0204] 10c third piezoelectric functional layer

[0205] 11 first electrode layer (top electrode)

[0206] 11a first electrode layer

[0207] 11b first electrode layer

[0208] 111 mirrors

[0209] 12 second electrode layer (bottom electrode; counter electrode)

[0210] 12a second electrode layer (counter electrode)

[0211] 12b second electrode layer (counter electrode)

[0212] 100 MEMS device

[0213] 200 MEMS device

[0214] 300 MEMS device

[0215] 400 MEMS device

[0216] 500 MEMS device

Claims

Patent claims 1. A method for producing a layer structure for a MEMS device, in particular a vacuum-packed MEMS mirror device, comprising: - Providing a starting substrate comprising at least one functional layer (10; 10a, 10b; 10a, 10b, 10c), wherein the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the starting substrate comprises ferroelectric and / or piezoelectric material, and - Structuring the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the starting substrate to form one or more movable elements of the MEMS device (200; 300; 400; 500) in the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) and / or to form a spring structure that holds the one or more movable elements of the MEMS device (200; 300; 400; 500) in the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c).

2. Method according to claim 1, characterized in that the starting substrate comprising the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) consists of ferroelectric and / or piezoelectric material.

3. Method according to claim 1 or 2, characterized in that the starting substrate comprising the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) comprises one or more piezoelectric layers made of ferro- and / or piezoelectric material, in particular one or more functional layers (10; 10a, 10b; 10a, 10b, 10c) made of ferro- and / or piezoelectric material.

4. Method according to one of the preceding claims, characterized in that the starting substrate which has the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c), and / or at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the starting substrate comprises a single crystal of a ferro- and / or piezoelectric material and / or consists of a single crystal of a ferro- and / or piezoelectric material.

5. Method according to one of the preceding claims, characterized in that the starting substrate which has the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) and / or at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the Starting substrate comprises a polycrystal of a ferro- and / or piezoelectric material and / or consists of a polycrystal of a ferro- and / or piezoelectric material.

6. Method according to one of the preceding claims, characterized in that the ferro- and / or piezoelectric material is aluminum nitride (AIN), aluminum Scandium nitride (AlScN), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), lead zirconate titanate (PZT), niobium-doped PZT (PZT-Nb) and / or quartz.

7. Method according to one of the preceding claims, characterized in that the starting substrate which has the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c), and / or at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the starting substrate comprises an at least partially amorphous ferro- and / or piezoelectric material and / or consists of an at least partially amorphous ferro- and / or piezoelectric material.

8. Method according to one of the preceding claims, characterized in that a layer thickness of the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the starting substrate, which comprises ferro- and / or piezoelectric material, is substantially greater than or equal to 50 pm, in particular substantially greater than or equal to 100 pm, and / or substantially less than or equal to 1 mm.

9. Method according to one of the preceding claims, characterized by - applying and / or providing electrically conductive electrode layers (11, 12; 11a, 12, 11b; 11a, 12a, 11b, 12b) on respective opposite sides of the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c), and - Structuring the electrode layers (11, 12; 11a, 12, 11b; 11a, 12a, 11b, 12b) to form structured electrode surfaces on respective opposite sides of the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c).

10. The method according to claim 9, characterized in that in the structuring of one of the electrode layers (11; 11a), in particular an outer electrode layer (11; 11a), a mirror (111) of the MEMS device is formed.

11. Method according to one of the preceding claims, characterized in that during the structuring of the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) of the starting substrate, a mirror carrier element is formed in the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c), wherein a mirror (111) is arranged and / or formed on the mirror carrier element.

12. The method according to claim 11, characterized in that during the structuring of the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c), a spring structure which holds the mirror carrier element with mirror (111) is formed in the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c).

13. The method according to claim 12, characterized in that the spring structure is designed such that the mirror support element with mirror (111) is held so as to be oscillatable about one or two axes, in particular oscillation and / or torsion axes, particularly preferably for a two-dimensional Lissajous scanning movement of the mirror support element with mirror (111).

14. Method according to at least one of claims 9 to 13, characterized in that the conductive electrode layers (11, 12) are formed for electrical contact on opposite sides of the functional layer (10).

15. Method according to at least one of claims 9 to 13, characterized in that at least one second electrode layer (12) of the conductive electrode layers is guided by means of a through-plating in a region of the at least one functional layer (10) from a second side of the at least one functional layer (10) to a first side of the at least one functional layer (10), on which a first electrode layer (11) of the conductive electrode layers is arranged.

16. The method according to claim 15, characterized in that at least the first electrode layer (11) and the second electrode layer (12) are formed by means of the through-plating of the second electrode layer (12), to provide electrical contact between the first and second electrode layers (11, 12) on the same first side of the functional layer (10).

17. Method according to one of the preceding claims, characterized in that the starting substrate comprises a ferro- and / or piezoelectric functional layer (10).

18. Method according to one of the preceding claims, characterized in that the starting substrate has two ferro- and / or piezoelectric functional layers (10a, 10b) with an intermediate electrode layer (12).

19. Method according to one of the preceding claims, characterized in that the starting substrate comprises three or more ferro- and / or piezoelectric Functional layers (10a, 10b, 10c), wherein a respective electrode layer (12a, 11b) is arranged between adjacent ferro- and / or piezoelectric functional layers (10a, 10b, 10c).

20. A layer structure, which is produced in particular by means of the method according to at least one of the preceding claims, comprising: - at least one structured functional layer (10; 10a, 10b; 10a, 10b, 10c) in which one or more movable elements of the MEMS device (200; 300; 400; 500) and / or a spring structure that holds the one or more movable elements of the MEMS device (200; 300; 400; 500) are formed, wherein the at least one functional layer (10; 10a, 10b; 10a, 10b, 10c) comprises ferroelectric and / or piezoelectric material.

21. MEMS device, in particular MEMS mirror device (200; 300; 400; 500), comprising a layer structure according to claim 20.

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