Method for producing a microelectromechanical component structure, microelectromechanical component structure, microelectromechanical device and microelectromechanical loudspeaker

Abstract

The invention relates to a method (100) for producing a microelectromechanical component structure (200) having a first substrate (20), which has a substrate surface (21), and having at least one vertical functional region (F), which extends substantially perpendicularly to the substrate surface (21), wherein the at least one vertical functional region (F) is delimited with respect to an adjacent sacrificial region (O) by virtue of at least one vertical trench (70) being produced and passivated and is exposed by virtue of the sacrificial region (O) being removed, wherein a bonding surface (23) is produced on the substrate surface (21) of the first substrate (20) by virtue of at least one layer (22) being applied, and wherein a second substrate (30) is applied to the bonding surface (23), in which second substrate at least one vertical trench (70) is produced as far as the bonding surface (23) of the first substrate (20). The invention also relates to a microelectromechanical component structure (200), to a microelectromechanical device (300), and to a microelectromechanical loudspeaker (400).

Description

[0001] Description

[0002] title

[0003] Method for producing a microelectromechanical component structure, microelectromechanical component structure, microelectromechanical device and microelectromechanical loudspeaker

[0004] The invention relates to a method for producing a microelectromechanical component structure, a microelectromechanical component structure, a microelectromechanical device and a microelectromechanical loudspeaker.

[0005] State of the art

[0006] Microelectromechanical structures, also known as MEMS structures, as well as methods for their production are known from the state of the art.

[0007] DE 102015206 996 A1 discloses a method for producing microelectromechanical structures in a layer sequence and a corresponding electronic component with a microelectromechanical structure.The method comprises providing a carrier substrate having a first surface, applying an insulation layer to the first surface, epitaxially growing a first silicon layer on the insulation layer, structuring the first silicon layer to form trenches in the first silicon layer, passivating the first silicon layer, wherein the trenches are filled and a passivation layer is formed on a side facing away from the first surface, structuring the passivation layer, wherein sacrificial regions and functional regions are formed in the first silicon layer and the sacrificial regions on a side facing away from the carrier substrate are at least partially free of the passivation layer, and finally removing the sacrificial regions.

[0008] EP 3 912 953 A1 describes a method for producing a MEMS component, in which a first and a second structural layer are produced and provided with trenches and masking layers.

[0009] US 2015 / 0 274 ​​512 A1 discloses MEMS devices and manufacturing methods therefor, in which a first dielectric layer with integrated circuits is formed on a first substrate, a second dielectric layer with an acceleration sensor is produced thereon and a second substrate is applied to the second dielectric layer.

[0010] US 8 043 931 B1 relates to a method for producing a multilayer silicon structure by producing structured individual layers and aligning and joining the individual layers.

[0011] Disclosure of the invention

[0012] According to the features of independent claim 1, a method is proposed for producing a microelectromechanical component structure with a first substrate having a substrate surface and with at least one vertical functional region which extends substantially perpendicular to the substrate surface, wherein the at least one vertical functional region is delimited from an adjacent sacrificial region by creating and passivating at least one vertical trench and is exposed by removing the sacrificial region, wherein a bonding surface is created on the substrate surface of the first substrate by applying at least one layer, and wherein a second substrate is applied to the bonding surface, in which at least one vertical trench is created.

[0013] In other words, it is proposed to use microelectromechanical

[0014] To produce component structures with a layer structure comprising more than one substrate, whereby greater layer thicknesses can generally be achieved by using substrates than, for example, with epitaxial growth processes or deposition processes. Accordingly, the proposed method makes it possible to produce microelectromechanical component structures and functional areas with large vertical dimensions, for example greater than 100 μm, in a simplified process. In addition, the presented method can be used to produce laterally narrow structures, for example with a width of less than 20 μm, which can also be realized with a narrow tolerance range, for example less than 10 μm, less than 5 μm, or less than 2 μm. A narrow structure can, for example, increase the mobility of the functional area and reduce its rigidity.The manufacturing method with passivated vertical trenches and optional horizontal etch stop regions (explained later) can delimit sacrificial regions and functional regions from each other, allowing the functional regions to be exposed by removing the sacrificial regions or, alternatively, separating functional regions with different potentials from each other. A high degree of design freedom with virtually any vertical and horizontal structure is possible. The functional regions can, for example, form mechanical or electrical connections and extend across the entire vertical extent of the component structure or a carrier of the component structure, for example, a MEMS chip, or only across a portion of the same, and can be individually designed locally.This allows, for example, the creation of movable structures or the free definition and design of electrical connections and insulation. For example, vertical and / or horizontal electrical potential distribution or separation is possible. Furthermore, horizontal electrical potential distribution can be used for mechanical stability purposes or for a horizontal connection of vertically offset structures. Furthermore, the trenches in the second substrate or in other substrates explained later can be created easily and with high precision compared to trench production in material layer sequences with individually applied material layers with a comparable vertical extension.Furthermore, the microelectromechanical structure can be manufactured economically and efficiently using the presented method, since a large layer height can be achieved cost-effectively with a single substrate compared to material layers of comparable vertical extent produced by epitaxial growth or deposition processes. Furthermore, the presented method is suitable for CMOS and high-temperature applications. Attaching a second or additional substrate, for example, using a direct wafer bonding process, is also thermally and energetically more advantageous than, for example, epitaxial growth processes with a comparable structure height. For example, epitaxial growth processes can require a process temperature of over 1,000 °C, while wafer bonding processes can take place at temperatures below 100 °C. Furthermore, a smaller wafer bow can be expected with the presented method.By creating a stable, solid layer structure with substrates, no moving structures are present during the process, and the subsequent structures are fixed during the process flow via vertical and horizontal passivation and etch stop structures, thus ensuring high process reliability. The deep structuring of the component structure is achieved by contouring the functional and sacrificial areas, eliminating the need for large-volume etching during the trench process and allowing the structural elements to be defined more precisely, resulting in a reduced trench angle and lower tilt.

[0015] The first substrate, also known as a wafer, can be, for example, a silicon substrate, particularly a monocrystalline one. The first substrate can form a planar support structure for the microelectromechanical component structure, having a base area and a substrate surface opposite the base area, on which the further component structure can be built up as a layer sequence. The base area and the substrate surface can comprise the largest surface area of ​​the first substrate and each have a length and width that are greater than the depth of the first substrate. The extension directions of the substrate surface can define a horizontal plane of the microelectromechanical component structure. The component structure can, for example, have a rectangular cross-sectional profile.The vertical functional region produced using the method presented can have a vertical extension perpendicular to the substrate surface that is greater than a horizontal extension of the functional region parallel to the substrate surface. The vertical functional region can, in particular, be embodied as a narrow structure, for example, have a width of less than 20 pm or have an extension in the vertical direction that is several times, for example, at least five times or at least ten times greater than in the horizontal width and / or depth direction. As a narrow structure, the vertical functional region can advantageously fulfill certain functions of the microelectromechanical component structure, for example, form a movable structure and thereby a sensing element or assume a mechanical function such as a support function between spaced-apart component elements.

[0016] The creation of a vertical trench can be implemented, for example, using a trench process to create a narrow trench with high precision. At least one trench created in the second substrate can advantageously extend to the bonding surface of the first substrate. The position of the trench or multiple trenches can be predetermined for trench creation, for example, by a structured etch stop layer acting as a masking layer. The passivation of the created vertical trench can be carried out as surface passivation of the trench surface and, for example, by filling a passivation material that acts as an etch barrier, so that an etching process stops at the passivated trench. For example, a horizontal etch stop layer can be applied to the second substrate having the vertical trench. This etch stop layer penetrates into the vertical trench due to capillary effects and passivates it.

[0017] The application of at least one layer can refer to the application of a material layer made of, in particular, a semiconductor-based material. Such a material layer can, for example, be a monocrystalline, polycrystalline, or amorphous silicon layer, or a dielectric layer comprising a silicon compound such as, for example, silicon dioxide (SiO2) or silicon nitride (SiSiO2). The application of at least one layer can further refer to the application of an auxiliary layer such as an etch stop layer or sacrificial layer, which can be optionally removed again during the process or subsequently, for example by means of an HF gas-phase etching process. Etch stop layers or sacrificial layers can, for example, comprise a silicon compound such as silicon dioxide (SiO2) or silicon nitride (SiSiO2).An etch stop layer can, for example, be used to define horizontal boundaries within the component structure and protect adjacent structural regions from etching. In particular, it is conceivable to provide etch stop regions in sections of the component structure where a later vertical trench is intended to end. The application of at least one layer can furthermore refer to the application of a layer sequence, which can, for example, comprise one or more material layers and / or one or more auxiliary layers. An applied layer can also optionally be structured, for example by etching, for example to form spaced-apart layer regions.

[0018] The second substrate and further substrates discussed later can be designed similarly or identically to the first substrate in terms of material and dimensions. For example, the second or further substrate can advantageously be a silicon substrate, in particular a monocrystalline one. According to one embodiment, the first substrate and the second or further substrate can have substantially the same substrate heights. Alternatively, it is conceivable for the second or further substrate to have a larger or smaller substrate height in order to be able to define individual layer heights of the microelectromechanical component structure. The substrate height can also be influenced, for example, by thinning the second or further substrate. The second or further substrate can be applied, for example, using a direct wafer bonding process.

[0019] The bonding surface can be a surface of the layer structure facing away from the first substrate, comprising the first substrate and at least one layer, wherein the bonding surface can run parallel to the substrate surface of the first substrate. The bonding surface is provided for connecting the second substrate to the existing layer structure and forms an interface between at least one layer applied to the first substrate and the second substrate. In this case, it can be advantageous to create a continuous bonding surface so that the second substrate can lie flat on the bonding surface. In particular, a structured layer with layer sections spaced apart from one another by the structuring can be coated with a material in such a way that a continuous bonding surface is created.

[0020] After the introduction and passivation of the at least one vertical trench or in a final process of the method, the functional region can be exposed by removing an adjacent sacrificial region. Several sacrificial regions, for example two or more, can also be adjacent to the functional region and are removed to expose the functional region. The removal can be carried out by means of an etching process, which can, for example, stop vertically at the passivated trench and horizontally at an auxiliary layer such as an etch stop layer. The etching process can, for example, be suitable for removing silicon material. The etching process can, for example, be an isotropic plasma etching process using, for example, sulfur hexafluoride (SFe) or a gas-phase etching process using, for example, xenon difluoride (XeF2).The removal of the sacrificial regions can be performed starting from the surface of a recently applied substrate and / or starting from the backside of the first substrate, which is opposite the substrate surface of the first substrate. Optionally, following the removal of the sacrificial region, passivation and etch stop material can be removed from the component structure to completely expose the functional area.

[0021] According to one embodiment, the bonding surface of the first substrate can be created by applying and structuring a first etch stop layer to form spaced-apart etch stop regions and by filling gaps between the etch stop regions with a material layer. This allows a bonding surface to be specifically created that can provide etch stop regions as an etch barrier, for example, to limit the depth of vertical trenches. Furthermore, the etch stop regions can form a horizontal boundary, for example, between a sacrificial region and a functional region of the component structure, so that an etching process for removing a sacrificial region stops on the etch stop region and an adjacent region is protected from etching attack. The etch stop layer can be, for example, a silicon dioxide layer or a silicon nitride layer.The etch stop layer can be applied, for example, by thermal oxidation and / or chemical vapor deposition. Horizontally extending etch stop regions and vertically extending passivated trenches provide a high degree of design freedom in the geometric configuration of the functional and sacrificial regions. Overlapping or interlocking structural elements or structural regions can also be realized. The material layer can be a semiconductor material, in particular a silicon material, for example.

[0022] According to one embodiment, the gaps can be filled with a monocrystalline silicon material as a material layer. As a result, for example, in the case of a monocrystalline first substrate and a monocrystalline second substrate, the material layer can create a continuously monocrystalline vertical structure across the layer structure. A continuously monocrystalline vertical structure can have particularly favorable mechanical and electrical properties. For example, the structure can have increased fracture strength or increase the thermal conductivity of the structure. The material layer can be applied, for example, by epitaxial growth or by deposition, for example by chemical vapor deposition (CVD). According to other embodiments, it is also conceivable to use, for example, a polycrystalline or amorphous silicon material for the material layer.

[0023] According to one embodiment, the bonding surface of the first substrate can be prepared for the application of the second substrate by chemical and / or mechanical processing. This can ensure a reliable and flat connection of the second substrate to the bonding surface. For example, the bonding surface can be planarized. The processing can be carried out, for example, by polishing, for example by chemical-mechanical polishing (CMP process). Furthermore, it is conceivable, for example, to thin the second substrate after application to the bonding surface to a predefined structure height of the substrate surface of the second substrate by means of grinding and / or polishing. The second substrate can, for example, have a thickness of more than 100 pm, more than 200 pm, or more than 400 pm before or after an optional thinning process.

[0024] According to one embodiment, a further bonding surface can be created on the substrate surface of the second substrate facing away from the first substrate, and a further substrate can be applied to the bonding surface of the second substrate, in which at least one further vertical trench is created. This allows the vertical extension of the component structure and a functional region of the component structure to be further increased efficiently and simply. The at least one further vertical trench can, in particular, be introduced up to the bonding surface of the second substrate.The further bonding surface can be created analogously to the creation of the bonding surface on the first substrate, for example by applying and structuring an etch stop layer to form spaced-apart etch stop regions and by filling gaps between the etch stop regions with a material layer, wherein the material layer can be, for example, a silicon material, in particular a monocrystalline silicon material, and can be applied, for example, by epitaxial growth or by deposition. The application of a further substrate can be done analogously to the application of the second substrate, for example by means of a wafer direct bonding process. Furthermore, it is conceivable, for example, to thin the further substrate after application to the bonding surface to a predefined structure height of the substrate surface of the further substrate by means of grinding and / or polishing.The additional substrate can, for example, have a thickness of more than 100 pm, more than 200 pm, or more than 400 pm before or after an optional thinning process. The creation of additional vertical trenches can be carried out analogously to the creation of trenches in the second substrate, for example, using a trenching process.

[0025] According to one configuration of the above-described embodiment, applying at least one layer to a substrate surface of a substrate, creating a bonding surface, applying a further substrate, and creating and passivating at least one vertical trench in the further substrate can be repeated cyclically until a predefined target height of the vertical functional region is reached. This allows the vertical extension of the component structure and of a functional region of the component structure to be further increased efficiently and easily. After reaching the predefined target height, which can optionally be precisely adjusted by thinning the last applied substrate, the functional region can be exposed by removing the sacrificial region.

[0026] According to one embodiment, the method may comprise a start process, a cycle process and a termination process, wherein the start process comprises the following steps:

[0027] - Providing the first substrate;

[0028] - applying a first etch stop layer to the first substrate; and

[0029] - Creating spaced-apart etch stop regions by structuring the first etch stop layer.

[0030] Accordingly, the process can be divided into different process stages, with an initial process phase referred to as the start process and a final process phase as the finish process. The cycle process can comprise a sequence of process steps that can be repeated in cycles between the start process and the finish process at any frequency. This provides a highly versatile yet simple process that can be varied, for example in terms of its number of cycles, and individually adapted to the specified requirements of the component structure to be created. The individual layer levels can be structured and designed individually and independently of one another, so that in each cycle a section of an overall layout of the component structure with individual geometric structures can be produced. The initial start process provides an entry point into the cycle process.During the initial process, a first substrate is provided as a carrier structure, and a first etch stop layer is applied and patterned onto it. Further process steps can be performed directly afterward, for example, as part of the cycle process.

[0031] According to one embodiment, the cycle process may comprise the following steps:

[0032] - Filling gaps between the spaced etch stop areas with a layer of material to form a bonding surface;

[0033] - Bonding a second or further substrate to the formed bonding surface;

[0034] - Applying a second etch stop layer to the further substrate;

[0035] - Creating spaced-apart etch stop regions by structuring the second etch stop layer;

[0036] Creating at least one vertical trench between the etch stop regions of the second etch stop layer, in particular up to an etch stop region of the first etch stop layer;

[0037] - applying a third etch stop layer and passivating the at least one trench; and

[0038] - Creating spaced-apart etch stop regions by structuring the third etch stop layer.

[0039] The aforementioned steps can be repeated cyclically in the described sequence, for example, until the component structure or a functional area of ​​the component structure has reached a predefined vertical target height. Optionally, after filling the gaps between the spaced etch stop regions with a material layer to form a bonding surface, the bonding surface can be planarized to provide an optimized flat surface for connecting the second or further substrate. The etch stop regions of the second etch stop layer can form a mask, wherein the regions between the etch stop regions can define the positions of the trenches to be created.Optionally, the etch stop regions of the second etch stop layer can be removed again after the creation of the at least one vertical trench, for example by etching and / or mechanical processing, in order to enable a uniform application of a third etch stop layer. The third etch stop layer can be created, for example, by deposition or growth on the substrate surface of the second substrate facing away from the first substrate, wherein the application of the third etch stop layer also forms a passivation layer on the surface of the at least one vertical trench and closes a trench structure opening of the trench on the substrate surface. The second and third etch stop layers can be, for example, a silicon dioxide layer or a silicon nitride layer.The last described step of creating spaced-apart etch stop regions by structuring the third etch stop layer provides spaced-apart etch stop regions that can be filled with a material layer upon a new cycle entry according to the first step of the cycle process in order to form another bonding surface and enable the bonding of another substrate to the bonding surface. Thus, the cycle process of the method can be carried out and repeated with a closed circuit. It should be noted that during a second cycle pass, the created vertical trench is no longer introduced, in particular, up to an etch stop region of the first etch stop layer, but rather ends, in particular, on an etch stop region of the third etch stop layer in the sense of the etch stop layer last applied in the previous cycle pass.If no further cycle entry is planned, the spaced-apart etch stop regions of the third etch stop layer can form horizontal boundaries of functional regions in order to protect them from an etch attack during a subsequent exposure of the functional regions.

[0040] According to one embodiment, the completion process may comprise the following step:

[0041] - Clearing the functional area by removing the sacrificial area.

[0042] This allows the microelectromechanical component structure to be provided with exposed functional regions. Optionally, the final process can comprise a further step following the exposure, in which the etch stop and passivation material is at least partially removed from the component structure. The described steps can, for example, immediately follow a completed cycle of the method. The sacrificial region can be removed, for example, using an etching process suitable for removing silicon material. The etching process can, for example, be an isotropic plasma etching process using, for example, sulfur hexafluoride (SFe) or a gas-phase etching process using, for example, xenon difluoride (XeF2).The distance of the sacrificial region is limited horizontally by the surface passivation of the trench structures, while the etching process is limited vertically by the etch stop regions of the respective substrate surfaces. Material connections between two substrate planes, realized via the material layer, which in particular comprises a silicon material, can form a vertical etch channel for the sacrificial regions across the substrate planes.

[0043] The invention also relates to a microelectromechanical component structure with a first substrate having a substrate surface and with at least one vertical functional region which extends substantially perpendicular to the substrate surface, wherein the vertical functional region extends over a material layer arranged on the substrate surface and over a second substrate arranged on the material layer. The component structure is characterized by particularly simple and efficient production. The construction of the component structure, which is based on a layered structure with at least two substrates arranged in the layered structure, makes it possible to provide functional regions with a high vertical extent, high stability and optionally with very narrow structures, e.g. with a width of less than 20 pm, and tight tolerances, for example less than 10 pm, less than 5 pm or less than 2 pm.For example, the functional region can have a vertical extension that can be greater than 100 pm. The component structure can be manufactured, in particular, using the method described above. The component structure can, for example, have a rectangular cross-sectional profile. According to one embodiment, the material layer can comprise a monocrystalline silicon material. As a result, for example, in the case of a monocrystalline first substrate and a monocrystalline second substrate, the monocrystalline material layer can provide a consistently monocrystalline vertical structure across the layer structure.

[0044] According to one embodiment, the vertical functional region can extend over at least one further material layer and over at least one further substrate arranged on the further material layer. This makes it possible to provide a component structure with a very high vertical extension of the component structure or of a functional region of the component structure.

[0045] The invention also relates to a microelectromechanical device with a microelectromechanical component structure according to one of the features described above, wherein the microelectromechanical component structure forms, at least in sections, a displacement structure for generating a fluid pressure. The displacement structure can be formed, for example, by at least one functional region of the component structure. In this case, for example, at least one functional region of the component structure can form a movable element of the displacement structure, wherein excitation of the functional region can cause a volume change in the component structure, by which a fluid pressure can be generated. With the component structure presented, it is possible to provide functional regions with a high vertical extent and a narrow design that have low rigidity and are thus easily excitable.Such functional areas enable highly efficient fluid pressure generation with low energy consumption. According to one embodiment, the device can be designed, for example, as a pump or a valve for microfluidic applications. According to another embodiment, the device can be designed as an acoustic sound generator.

[0046] The invention also relates to a microelectromechanical loudspeaker comprising a microelectromechanical device as described above, wherein the displacement structure is configured to generate sound pressure as fluid pressure, and wherein the loudspeaker further comprises a signal processing unit for applying and processing signals from the microelectromechanical device. The displacement structure can be formed, for example, by at least one functional region of the component structure. With the presented component structure, it is possible to provide functional regions with a high vertical extent and a narrow design. Due to the narrow, elongated design, the functional regions have low rigidity and are easy to drive. The functional regions can advantageously form vertically arranged lamellae of the loudspeaker, with which sound pressure generation with high sound quality and low energy consumption is possible.The microelectromechanical loudspeaker can, for example, be implemented as a system-on-chip (SoC).

[0047] In general, in the context of this application, the words “a / an”, unless expressly defined otherwise, are not to be understood as a number, but as an indefinite article with the literal meaning of “at least one”.

[0048] The invention permits various embodiments and is explained in more detail below using exemplary embodiments and the accompanying drawings. They show schematically:

[0049] Fig. 1 - a method for manufacturing a microelectromechanical

[0050] Component structure according to an embodiment;

[0051] Fig. 2a-2k - a method for manufacturing a microelectromechanical

[0052] Component structure according to another embodiment;

[0053] Fig. 3a-3b - a microelectromechanical component structure manufactured according to the method of Fig. 2a-2k before and after a final process of the method;

[0054] Fig. 4 - a schematic diagram of a microelectromechanical

[0055] Loudspeaker with a microelectromechanical device.

[0056] Fig. 1 schematically shows a method 100 for producing a microelectromechanical component structure 200, shown for example in Figs. 3a and 3b, according to an exemplary embodiment. The method 100 comprises a start process 110, a cycle process 120 and a final process 130. The component structure 200 comprises a first substrate 20 with a substrate surface 21. As shown in Fig. 3a, vertical functional regions F extend substantially perpendicular to the substrate surface 21. The vertical functional regions F are delimited from adjacent sacrificial regions O by generated and passivated trenches 70 and are exposed in Fig. 3b by removing the sacrificial regions O. As will be explained in more detail below with reference to Fig. 1, a bonding surface 23 is produced on the substrate surface 21 of the first substrate 20 by applying at least one layer 22.A second substrate 30 is applied to the bonding surface 23, in which vertical trenches 70 are created. Using the proposed method, microelectromechanical component structures 200 and functional areas F with large vertical dimensions and a narrow design can be manufactured in a simplified process. Furthermore, the presented method allows a high degree of design freedom in the creation of functional areas F in component structures 200.

[0057] The method 100 is explained in more detail below with reference to steps 1 to 12 shown in Fig. 1. The starting process 110 begins in a first step 1 with the provision of the first substrate 20 with a substrate surface 21. In a second step 2, a first etch stop layer 22a is applied as layer 22 to the substrate surface 21 of the first substrate 20. In a third step 3, spaced-apart etch stop regions 24a are created by structuring the first etch stop layer 22a. The method 100 then enters the cycle process 120. In a fourth step 4, gaps 25a between the spaced-apart etch stop regions 24a are filled with a material layer 22b to form a bonding surface 23. In an optional fifth step 5, a CMP process is used to planarize the bonding surface 23.In a sixth step 6, a second substrate 30 is bonded to the formed bonding surface 23. The second substrate 30 has a substrate surface 31 facing away from the first substrate 20. In a seventh step 7, the second substrate 30 is optionally thinned by grinding and polishing. In an eighth step 8, a second etch stop layer 26 is applied to the substrate surface 31 of the second substrate 30. In a ninth step 9, the second etch stop layer 26 is structured such that spaced-apart etch stop regions 24b are formed. In a tenth step 10, vertical trenches 70 are introduced between the etch stop regions 24b of the second etch stop layer 26. According to the exemplary embodiment shown, the vertical trenches 70 end on the etch stop regions 24a of the first etch stop layer 22a.In an eleventh step 11, a third etch stop layer 27 is applied, which simultaneously passivates the trenches 70 with passivation material 71. In a twelfth step 12, the third etch stop layer 27 is structured to create spaced-apart etch stop regions 24c. The cycle process 120 can then optionally be run through again, incorporating further substrates, for example, with a third substrate 40, a fourth substrate 50, and a fifth substrate 60, as will be explained in more detail below with reference to Figs. 2a to 2k. Alternatively, it is conceivable to enter the final process 130 after each cycle run, in which the functional regions F are exposed by removing the sacrificial regions O. The final process 130 can be started, for example, when the functional regions F of the component structure 200 have reached a predefined target height.

[0058] With reference to Figs. 2a to 2k, it is explained how a component structure 200 with individually designed functional areas F can be produced using the presented method 100 by passing through several cycle processes 120.

[0059] In Fig. 2a, it can be seen that a first substrate 20 with a substrate surface 21 was provided, and that a first etch stop layer 22a was applied and patterned on the substrate surface 21 as layer 22. The patterning created spaced-apart etch stop regions 24a, between which gaps 25a are present.

[0060] Fig. 2b shows that the gaps 25a have been filled with a material layer 22b, and a bonding surface 23 has been formed. The material layer 22b can be applied, for example, by deposition or growth of a particularly monocrystalline silicon layer. The growth process can create a polycrystalline layer 80 on the etch stop regions 24a of the first etch stop layer 22a. Optionally, following the application of the material layer 22b, the produced bonding surface 23 was chemically mechanically polished to create a topography balance and a smooth bonding surface 23. Subsequently, a second substrate 30, particularly a silicon substrate, with a substrate surface 31 was bonded to the bonding surface 23 using the wafer bonding process.Subsequently, an optional back-grinding of the second substrate 30 and a chemical-mechanical polishing of the second substrate surface 31 were performed to bring the second substrate 30 to a target layer thickness. Furthermore, the second substrate 30 was structured by creating trenches 70 in the second substrate 30, which expose the side surfaces of the functional regions F and end at the etch stop regions 24a of the first etch stop layer 22a.

[0061] Fig. 2c shows that a third etch stop layer 27 has been applied to the substrate surface 31 of the second substrate 30, thereby passivating the surfaces of the trenches 70 with a passivation material 71. Furthermore, the third etch stop layer 27 closes the trenches 70 on the substrate surface 31 of the second substrate 30. Furthermore, the third etch stop layer 27 has been structured to form spaced-apart etch stop regions 24c.

[0062] Fig. 2d shows that, analogously to the procedure described for Fig. 2b, a further bonding surface 23 was created by applying a further material layer 22b, and a third substrate 40 was connected. Trenches 70 were created in the third substrate 40, which trenches end on the etch stop regions 24c of the third etch stop layer 27. The trenches 70 in the second substrate 30 and the trenches 70 in the third substrate 40 are predominantly arranged such that they merge into one another as vertically continuous trenches 70. In addition, however, Fig. 2d also shows that an etch stop region 24c' was formed as the horizontal boundary of a functional region F, so that at this etch stop region 24c' a vertical trench 70 of the second substrate 30 is arranged offset from a vertical trench 70 of the third substrate 40.This shows that with etch stop layers and passivated vertical trenches, virtually any desired geometry of the functional regions F can be designed. Furthermore, Fig. 2d shows that with vertical trenches and horizontal etch stop regions 24c', adjacent functional regions F can also be structurally separated from one another. This allows, for example, electrically isolated functional regions F to be produced for separate potential conduction in the component structure 200.

[0063] In Fig. 2e, it can be seen that a fourth etch stop layer 28 was applied to the third substrate 40, thereby passivating the surfaces of the trenches 70 with a passivation material 71. The fourth etch stop layer 28 was patterned to form further etch stop regions and also to create a further horizontal etch stop region 24c'.

[0064] In Fig. 2f it can be seen that in an analogous manner to the steps described above, a fourth substrate 50 was connected and structured by vertical trenches 70.

[0065] Fig. 2g shows the passivation of the trenches 70 in the fourth substrate 50 by a fifth etch stop layer 29 and the formation of horizontal etch stop regions 24c' by structuring the fifth etch stop layer 29. Furthermore, analogously to the previous steps, a fifth substrate 60 was bonded to a bonding area 23 formed on the fourth substrate 50.

[0066] Fig. 2h shows the further structuring of the fifth substrate 60 by vertical trenches 70 passivated with passivation material 71 and further horizontal etch stop regions 24c' of a sixth etch stop layer 29-2. Furthermore, a seventh etch stop layer 29-3 was applied and structured on the rear side 21-2 of the first substrate 20, which lies opposite the substrate surface 21, and vertical trenches 70 were created and passivated in the first substrate 20, wherein the trenches 70 in the first substrate 20 establish connections to vertical trenches 70 of the second substrate 30. As a result, the structuring of the component structure 200 into sacrificial regions O and functional regions F can also be performed in the region of the first substrate 20, and the contouring of the sacrificial regions O and functional regions F can be created over the entire component structure 200. In Fig.2h the desired target height of the functional areas F is reached and the method 100 can enter a final process 130.

[0067] In Fig. 2i, the sacrificial regions O of the second substrate 30, the third substrate 40, the fourth substrate 50 and the fifth substrate 60 accessible from the surface of the fifth substrate 60 were removed contiguously by means of isotropic sacrificial layer etching.

[0068] In Fig. 2j, the sacrificial regions O of the second substrate 30, the third substrate 40, the fourth substrate 50, and the fifth substrate 60, accessible from the rear side 21-2 of the first substrate 20, were removed contiguously by isotropic sacrificial layer etching. Removing the sacrificial regions O exposed the functional regions F.

[0069] In Fig. 2k, the accessible passivation and etch stop layers of the device structure 200 were removed by RF vapor phase etching to complete the exposure of the functional regions F.

[0070] 3a and 3b show a microelectromechanical component structure 200 manufactured according to the method of FIGS. 2a-2k before and after a final process 130 of the method 100. In FIG. 3a, the layout of the component structure 200 is evident from the arrangement of vertical trenches 70 and horizontal etch stop regions 24c', which divide the component structure 200 into sacrificial regions O and functional regions F. The vertical trenches 70 and horizontal etch stop regions 24c' can be individually created in each layer level of the component structure 200 and connected to trenches 70 and etch stop regions 24c' of other layer levels. This enables a high degree of design freedom for three-dimensional structures of the component structure 200.

[0071] Fig. 3b shows examples of structural elements of the component structure 200 that can be manufactured with the functional regions F shown in Fig. 3a. A first structural element 91 can, for example, be a movable three-dimensional structural element clamped in the viewing direction. A second structural element 92 can, for example, be a segmented, movable three-dimensional structural element clamped on both sides. A third structural element 93 can, for example, be a segmented, three-dimensional structural element clamped in the viewing direction and whose segments are independently movable. A fourth structural element 94 can, for example, be an immovable three-dimensional support structure clamped on both sides. A fifth structural element 95 can, for example, be a movable three-dimensional structural element suspended on one side.A sixth structural element 96 can, for example, be a horizontal connection of vertically offset structures of the same potential. A seventh structural element 97 can, for example, form horizontal electrical insulation. An eighth structural element 98 can, for example, form vertical electrical insulation. This demonstrates the high degree of design freedom with which the component structure 200 can be manufactured using the presented method 100.

[0072] Fig. 4 schematically shows a microelectromechanical loudspeaker 400 with a device 300 having a component structure 200 forming a displacement structure at least in part according to the above-described features, and with a signal processing unit 410 connected to the device 300 by a signal connection 420 and configured to apply and process signals from the microelectromechanical device 300. The displacement structure of the component structure 200 of the device 300 is configured to generate sound pressure as fluid pressure and to be operated acoustically efficiently with low power consumption. The microelectromechanical loudspeaker 400 can be implemented as a system-on-chip.

Claims

Claims 1. Method (100) for producing a microelectromechanical component structure (200) with a first substrate (20) having a substrate surface (21) and with at least one vertical functional region (F) which extends substantially perpendicular to the substrate surface (21), wherein the at least one vertical functional region (F) is delimited from an adjacent sacrificial region (O) by producing and passivating at least one vertical trench (70) and is exposed by removing the sacrificial region (O), wherein a bonding surface (23) is produced on the substrate surface (21) of the first substrate (20) by applying at least one layer (22), and wherein a second substrate (30) is applied to the bonding surface (23), in which at least one vertical trench (70) is produced.

2. The method (100) according to claim 1, wherein the bonding surface (23) of the first substrate (20) is produced by applying and structuring a first etch stop layer (22a) to form spaced-apart etch stop regions (24a) and by filling gaps (25a) between the etch stop regions (24a) with a material layer (22b).

3. The method (100) according to claim 2, wherein the gaps (25a) are filled with a monocrystalline silicon material as a material layer (22b).

4. Method (100) according to one of the preceding claims, wherein the bonding surface (23) of the first substrate (20) is prepared by chemical and / or mechanical processing for the application of the second substrate (30).

5. Method (100) according to one of the preceding claims, wherein a further bonding surface (23) is produced on the substrate surface (31) of the second substrate (30) facing away from the first substrate (20), and a further substrate (40) is applied to the bonding surface (23) of the second substrate (30), in which at least one further vertical trench (70) is produced.

6. The method (100) according to claim 5, wherein applying at least one layer (22) to a substrate surface (21, 31) of a substrate (20, 30, 40, 50, 60), creating a bonding surface (23), applying a further substrate (30, 40, 50, 60) and creating and passivating at least one vertical trench (70) in the further substrate (30, 40, 50, 60) are repeated cyclically until a predefined target height of the vertical functional region (F) is reached.

7. The method (100) according to any one of the preceding claims, wherein the method (100) comprises a start process (110), a cycle process (120) and a termination process (130), and wherein the start process (110) comprises the following steps: - providing the first substrate (20) (1); - applying a first etch stop layer (22a) to the first substrate (20) (2); and - producing spaced-apart etch stop regions (24a) by structuring the first etch stop layer (22a) (3).

8. The method (100) of claim 7, wherein the cycle process (120) comprises the following steps: - filling gaps (25a) between the spaced etch stop regions (24a) with a material layer (22b) to form a bonding surface (23) (4); - bonding a second or further substrate (30, 40, 50, 60) to the formed bonding surface (23) (6); - applying a second etch stop layer (26) to the second or further substrate (30, 40, 50, 60) (8); - producing spaced-apart etch stop regions (24b) by structuring the second etch stop layer (26) (9); producing at least one vertical trench (70) between the etch stop regions (24b) of the second etch stop layer (26), in particular up to an etch stop region (24a) of the first etch stop layer (22a) (10); - applying a third etch stop layer (27) and passivating the at least one trench (70) (11); and - producing spaced-apart etch stop regions (24c) by structuring the third etch stop layer (27) (12).

9. The method (100) according to claim 7 and 8, wherein the final process (130) comprises the following step: - Isolating the functional area (F) by removing the sacrificial area (O).

10. Microelectromechanical component structure (200) with a first substrate (20) having a substrate surface (21) and with at least one vertical functional region (F) which extends substantially perpendicular to the substrate surface (21), wherein the vertical functional region (F) extends over a material layer (22b) arranged on the substrate surface (21) and over a second substrate (30) arranged on the material layer (22b).

11. The microelectromechanical component structure (200) of claim 10, wherein the material layer (22b) comprises a monocrystalline silicon material.

12. Microelectromechanical component structure (200) according to claim 10 or 11 , wherein the vertical functional area (F) extends over at least one further material layer (22b) and over at least one on the further further substrate (40, 50, 60) arranged on the material layer (22b).

13. Microelectromechanical device (300) with a microelectromechanical component structure (200) according to one of the Claims 10 to 12, wherein the microelectromechanical component structure (200) forms, at least in sections, a displacement structure for generating a fluid pressure.

14. A microelectromechanical loudspeaker (400), comprising a microelectromechanical device (300) according to claim 13, wherein the displacement structure is configured to generate sound pressure as fluid pressure, and a signal processing unit (410) for applying and processing signals from the microelectromechanical device (300).

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