DE102023209211A1 - Method for producing a microelectromechanical component structure, microelectromechanical component structure, microelectromechanical device and microelectromechanical loudspeaker - Google Patents

Abstract

The invention relates to a 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 creating and passivating at least one vertical trench (70) and is exposed by removing the sacrificial region (O), wherein a bonding surface (23) is created 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 created up to the bonding surface (23) of the first substrate (20). The invention also relates to a microelectromechanical component structure (200), a microelectromechanical device (300) and a microelectromechanical loudspeaker (400).

Description

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

State of the art

Microelectromechanical structures, also known as MEMS structures, and methods for their production are known from the state of the art.

The DE 10 2015 206 996 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 with a first surface, applying an insulating layer to the first surface, epitaxially growing a first silicon layer on the insulating 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.

The EP 3 912 953 A1 describes a method for manufacturing a MEMS component in which a first and a second structural layer are produced and provided with trenches and masking layers.

The US 2015 / 0 274 512 A1 MEMS devices and manufacturing methods for them can be found 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.

The 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.

Disclosure of the invention

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.

In other words, it is proposed to produce microelectromechanical component structures with a layer structure comprising more than one substrate, whereby the use of substrates generally allows for greater layer thicknesses to be achieved 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 process-technically simplified manner. 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) that can delimit sacrificial regions and functional regions from one another and enable the functional regions to be exposed by removing the sacrificial regions or, alternatively, separate functional regions with different potentials from one another, enables a high degree of design freedom with almost any vertical and horizontal structures. 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 also allows for the creation of movable structures or electrical connections. and insulations can be freely defined and designed; for example, vertical and/or horizontal electrical potential guidance or separation is possible. Furthermore, horizontal electrical potential guidance can be used, for example, for mechanical stability purposes or for a horizontal connection of vertically offset structures. Furthermore, the trenches in the second substrate or in further 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 one substrate compared to material layers of comparable vertical extension produced by epitaxial growth processes or deposition processes. Furthermore, the presented method is suitable for CMOS and high temperatures. Connecting a second or further substrate, for example, using a direct wafer bonding process, is also thermally and energetically more favorable than, for example, epitaxial growth processes with a comparable structure height. For example, epitaxial growth processes may require a process temperature of over 1,000°C, while wafer bonding processes can take place at temperatures below 100°C. Furthermore, the presented process can be expected to have a smaller wafer bow. By creating a stable, solid layer structure with substrates, no movable structures are present during the process, and the subsequent structures are fixed via vertical and horizontal passivation and etch stop structures during the process flow, thus ensuring high process reliability. The deep structuring of the component structure is achieved by contouring the functional and sacrificial regions, 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.

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 area portion of the first substrate and each have a length and width that are greater than the depth of the first substrate. The directions of extension 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 designed as a narrow structure, for example, have a width of less than 20 µm 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.

The creation of a vertical trench can be implemented, for example, using a trenching 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.

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 be, for example, a monocrystalline, polycrystalline or amorphous silicon layer or a dielectric layer with a silicon compound such as, for example, silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ). 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 ren or subsequently optionally removed again, 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 (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ). With an etch stop layer, for example, horizontal boundaries within the component structure can be defined and adjacent structure regions can be protected from etching attack. In particular, it is conceivable to provide etch stop regions in sections of the component structure at which a later introduced vertical trench is to end. The application of at least one layer can furthermore relate 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 in order to form layer regions spaced apart from one another.

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 application of the second or further substrate can take place, for example, using a wafer direct bonding process.

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 filled with a material in such a way that a continuous bonding surface is created.

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 adjoin 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 (SF ₆ ) or a gas-phase etching process using, for example, xenon difluoride (XeF ₂ ). The removal of the sacrificial regions can be carried out starting from the surface of a last-applied substrate and/or starting from the backside of the first substrate, which is opposite the substrate surface of the first substrate. Optionally, after removing the sacrificial area, passivation and etch stop material can be removed from the component structure in order to achieve complete exposure of the functional area.

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 at 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 means of 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. In addition, overlapping or interlocking structural elements or structural regions can be realized. The material layer can be, for example, a semiconductor material, in particular a silicon material.

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, a continuously monocrystalline vertical structure can be created across the layer structure by the material layer. 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.

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 structural 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 µm, more than 200 µm, or more than 400 µm before or after an optional thinning process.

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 of a functional region of the component structure to be further increased efficiently and easily. The at least one further vertical trench can in particular be introduced up to the bonding surface of the second substrate. The creation of the further bonding surface can be carried out 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. The material layer can be 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 carried out 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 additional substrate after application to the bonding surface to a predefined structural height of the substrate surface of the additional substrate by grinding and/or polishing. The additional substrate can, for example, have a thickness of more than 100 µm, more than 200 µm, or more than 400 µm 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.

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.

• - Bereitstellen des ersten Substrats;
• - Aufbringen einer ersten Ätzstoppschicht auf das erste Substrat; und
• - Erzeugen von voneinander beabstandeten Ätzstoppbereichen durch Strukturieren der ersten Ätzstoppschicht.

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:

• - Providing the first substrate;
• - applying a first etch stop layer to the first substrate; and
• - Creating spaced-apart etch stop regions by structuring the first etch stop layer.

Accordingly, the process can be divided into different process stages, with an initial process phase being referred to as the start process and a final process phase being referred to as the completion process. The cycle process can include a sequence of process steps that can be repeated in a cycle-like manner with any desired frequency between the start process and the completion process. This can result in a very versatile and Nevertheless, a simple process can be provided which, for example, can be varied 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 a section of an overall layout of the component structure with individual geometric structures can be produced in each cycle. The initial start process enables entry into the cycle process. During the start process, a first substrate is provided as a carrier structure and a first etch stop layer is applied to it and structured. Further process steps can, for example, be carried out directly afterwards as part of the cycle process.

• - Auffüllen von Zwischenräumen zwischen den beabstandeten Ätzstoppbereichen mit einer Materialschicht zur Bildung einer Bondoberfläche;
• - Bonden eines zweiten oder weiteren Substrats an die gebildete Bondoberfläche;
• - Aufbringen einer zweiten Ätzstoppschicht auf das weitere Substrat;
• - Erzeugen von voneinander beabstandeten Ätzstoppbereichen durch Strukturieren der zweiten Ätzstoppschicht;
• - Erzeugen mindestens eines vertikalen Grabens zwischen den Ätzstoppbereichen der zweiten Ätzstoppschicht, insbesondere bis zu einem Ätzstoppbereich der ersten Ätzstoppschicht;
• - Aufbringen einer dritten Ätzstoppschicht und Passivierung des mindestens einen Grabens; und
• - Erzeugen von voneinander beabstandeten Ätzstoppbereichen durch Strukturieren der dritten Ätzstoppschicht.

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

• - Filling gaps between the spaced etch stop areas with a layer of material to form a bonding surface;
• - Bonding a second or further substrate to the formed bonding surface;
• - Applying a second etch stop layer to the further substrate;
• - Creating spaced-apart etch stop regions by structuring the second etch stop layer;
• - 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;
• - applying a third etch stop layer and passivating the at least one trench; and
• - Creating spaced-apart etch stop regions by structuring the third etch stop layer.

The aforementioned steps can be repeated cyclically in the described sequence, for example, until the component structure or a functional region of the component structure has reached a predefined vertical target height. Optionally, after filling the gaps between the spaced-apart 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 creating the at least one vertical trench, for example by etching and/or mechanical processing, to enable 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. With the last described step of creating spaced-apart etch stop regions by structuring the third etch stop layer, spaced-apart etch stop regions are provided, which 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. The cycle process of the method can thus be carried out and repeated with a closed circuit. It should be noted that during a second cycle pass, the vertical trench created is no longer introduced up to an etch stop region of the first etch stop layer, but rather ends in 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.

• - Freistellen des Funktionsbereiches durch Entfernung des Opferbereiches.

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

• - Clearing the functional area by removing the sacrificial area.

This allows the microelectromechanical component structure to be provided with exposed functional areas. Optionally, the final process can include 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 area can can be removed, for example, by means of an etching process suitable for removing silicon material. The etching process can be, for example, an isotropic plasma etching process using, for example, sulfur hexafluoride (SF ₆ ) or a gas phase etching process using, for example, xenon difluoride (XeF ₂ ). The removal 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, which are realized via the material layer comprising, in particular, a silicon material, can form a vertical etching channel for the sacrificial regions across the substrate planes.

The invention also relates to a microelectromechanical component structure comprising a first substrate having a substrate surface and at least one vertical functional region extending 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 µm, and tight tolerances, for example, less than 10 µm, less than 5 µm, or less than 2 µm. For example, the functional region can have a vertical extent that can be greater than 100 µm. The component structure can be produced, 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 may comprise a monocrystalline silicon material. This allows, for example, a monocrystalline first substrate and a monocrystalline second substrate to be combined, the monocrystalline material layer can provide a continuous monocrystalline vertical structure across the layered structure.

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.

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, which have low rigidity and are thus easily excited. With such functional regions, very efficient fluid pressure generation with low energy consumption is possible. 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.

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 component structure presented, 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, which enable sound pressure generation with high sound quality and low energy consumption. The microelectromechanical loudspeaker can be implemented, for example, as a system-on-chip (SoC).

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”.

• 1 - ein Verfahren zur Herstellung einer mikroelektromechanischen Bauteilstruktur gemäß einem Ausführungsbeispiel;
• 2a-2k - ein Verfahren zur Herstellung einer mikroelektromechanischen Bauteilstruktur gemäß einem weiteren Ausführungsbeispiel;
• 3a-3b - eine gemäß dem Verfahren nach 2a-2k hergestellte mikroelektromechanische Bauteilstruktur vor und nach einem Abschlussprozess des Verfahrens;
• 4 - eine Prinzipskizze eines mikroelektromechanischen Lautsprechers mit einer mikroelektromechanischen Vorrichtung.

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

• 1 - a method for producing a microelectromechanical component structure according to an embodiment;
• 2a-2k - a method for producing a microelectromechanical component structure according to a further embodiment;
• 3a-3b - a procedure according to 2a-2k manufactured microelectromechanical component structure before and after a final process of the process;
• 4 - a schematic diagram of a microelectromechanical loudspeaker with a microelectromechanical device.

1 shows schematically a method 100 for producing a, for example, in the 3a and 3b shown microelectromechanical component structure 200 according to an 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 in 3a As shown, 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 in 3b by removing the sacrificial areas O. As shown below, 1 As explained in more detail below, 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, in which vertical trenches 70 are created, is applied to the bonding surface 23. With the proposed method, microelectromechanical component structures 200 and functional areas F with large vertical dimensions and a narrow design can be manufactured in a process-technically simplified manner. In addition, the presented method allows a high degree of design freedom in the creation of functional areas F in component structures 200.

In the following, the method 100 is described using the 1 illustrated steps 1 to 12 are explained in more detail. The start process 110 starts 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 produce spaced-apart etch stop regions 24c. Subsequently, the cycle process 120 can optionally be run through again with the inclusion of further substrates, for example, with a third substrate 40, a fourth substrate 50, and a fifth substrate 60, as will be described below with reference to 2a to 2k will be explained in more detail below. Alternatively, after each cycle run, it is conceivable to enter the final process 130, in which the functional areas F are exposed by removing the sacrificial areas O. The final process 130 can be started, for example, when the functional areas F of the component structure 200 have reached a predefined target height.

Based on the 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 running through several cycle processes 120.

In 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 as layer 22 and structured on the substrate surface 21. By structuring, spaced-apart etch stop regions 24a are generated, between which there are gaps 25a.

The 2b It can be seen 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 in order to create a topography balance and a smooth bonding surface 23. Subsequently, a second substrate 30, in particular 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 chemically mechanical polishing of the second substrate surface 31 were carried out in order to bring the second substrate 30 to a target layer thickness. In addition, the second substrate 30 was structured by creating trenches 70 in the second substrate 30, which trenches expose the side surfaces of the functional regions F and which end on the etch stop regions 24a of the first etch stop layer 22a.

In 2c It can be seen 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.

The 2d It can be seen that analogous to the 2b described procedure, a further bonding surface 23 was created by applying a further material layer 22b and a third substrate 40 was connected. In the third substrate 40, trenches 70 were created, which 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, in 2d However, it is also apparent that an etch stop region 24c' was formed as a 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. From this it is apparent that with etch stop layers and passivated vertical trenches almost any geometries of the functional regions F can be designed. In addition, in 2d It can be seen that with vertical trenches and horizontal etch stop regions 24c', even adjacent functional regions F can 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.

In 2e It can be seen that a fourth etch stop layer 28 has been 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 has been patterned to form further etch stop regions and also to create a further horizontal etch stop region 24c'.

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

In 2g 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 can be seen. Furthermore, analogous to the previous steps, a fifth substrate 60 was connected to a bonding area 23 formed on the fourth substrate 50.

In 2 hours The further structuring of the fifth substrate 60 can be seen by vertical trenches 70 passivated with passivation material 71 and further horizontal etch stop regions 24c' of a sixth etch stop layer 29-2. In addition, a seventh etch stop layer 29-3 was applied to the rear side 21-2 of the first substrate 20, which lies opposite the substrate surface 21, and structured, 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 carried out 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. 2 hours the desired target level of the functional areas F is reached and the method 100 can enter a final process 130.

In 2i the sacrificial areas O of the second substrate 30, the third substrate 40, accessible from the surface of the fifth substrate 60, of the fourth substrate 50 and the fifth substrate 60 are removed contiguously by means of isotropic sacrificial layer etching.

In 2 years 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 means of isotropic sacrificial layer etching. Removing the sacrificial regions O exposed the functional regions F.

In 2k the accessible passivation and etch stop layers of the device structure 200 were removed by HF gas phase etching to complete the exposure of the functional areas F.

In the 3a and 3b is a procedure according to 2a-2k manufactured microelectromechanical component structure 200 before and after a final process 130 of the method 100. In 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.

In 3b Examples of structural elements of the component structure 200 are shown, which are compatible with the 3a shown functional areas F can be manufactured. 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 three-dimensional structural element clamped in the viewing direction, segmented, and independently movable in the segments. A fourth structural element 94 can, for example, be an immobile 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. It thus becomes clear with what great design freedom the component structure 200 can be manufactured using the presented method 100.

4 schematically shows a microelectromechanical loudspeaker 400 with a device 300, which has a component structure 200 forming a displacement structure at least in sections according to the features described above, and with a signal processing unit 410, which is connected to the device 300 by a signal connection 420 and is designed 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.

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10 2015 206 996 A1 [0003]
• EP 3 912 953 A1 [0004]
• US 2015 / 0 274 512 A1 [0005]
• US 8 043 931 B1 [0006]

Claims (14)

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 creating and passivating at least one vertical trench (70) and is exposed by removing the sacrificial region (O), wherein a bonding surface (23) is created 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 created. Procedure (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). Procedure (100) according to Claim 2 , wherein the gaps (25a) are filled with a monocrystalline silicon material as a material layer (22b). 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). 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. Procedure (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 in a cycle until a predefined target height of the vertical functional region (F) is reached. 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 - creating spaced-apart etch stop regions (24a) by structuring the first etch stop layer (22a) (3). Procedure (100) according to Claim 7 , wherein the cycle process (120) comprises the following steps: - filling gaps (25a) between the spaced-apart 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). Procedure (100) according to Claim 7 and 8 , wherein the completion process (130) comprises the following step: - exposing the functional area (F) by removing the sacrificial area (O). 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). Microelectromechanical component structure (200) according to Claim 10 , wherein the material layer (22b) comprises a monocrystalline silicon material. Microelectromechanical component structure (200) according to Claim 10 or 11 , wherein the vertical functional region (F) extends over at least one further material layer (22b) and over at least one further substrate (40, 50, 60) arranged on the further material layer (22b). Microelectromechanical device (300) with a microelectromechanical component structure (200) according to one of the Claims 10 until 12 , wherein the microelectromechanical component structure (200) forms at least in sections a displacement structure for generating a fluid pressure. Microelectromechanical loudspeaker (400), comprising a microelectromechanical device (300) according to Claim 13 , wherein the displacer 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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