MEMS device

Abstract

MEMS device (10) comprising: a solid electrode (12) having a main area (12m); and a movable electrode (14) which is arranged in an insulated manner and spaced apart from the fixed electrode (12); wherein the movable electrode (14), which has a base surface substantially parallel to the main surface (12m) of the fixed electrode (12) and an end face (14f) laterally adjoining one or more spacers (18), is suspended in relation to the fixed electrode (12) by means of one or more spacers (18) comprising an insulating material, wherein the movable electrode (14) is attached to the one or more spacers (18) via the end face (14f) of the movable electrode (14), wherein the one or more spacers (18) are attached to the two electrodes (12, 14), and wherein the insulating material insulates the fixed electrode (12) and the movable electrode (14) from each other.

Description

AREA

[0001] Embodiments of the present disclosure relate to a MEMS device, a MEMS device used as an accelerometer, humidity sensor, bolometer or pressure sensor, and a method for manufacturing a MEMS device. BACKGROUND

[0002] A MEMS device, also known as a microelectromechanical system, is frequently used as a sensor, for example, as an accelerometer, pressure sensor, or sound wave sensor (microphone). All these MEMS devices have a moving element, such as a diaphragm or a cantilever arm, and the movement of this element, caused, for example, by a change in pressure or acceleration, can be detected capacitively. A common MEMS device consists of a movable electrode as the moving element and a fixed electrode opposite the moving electrode, so that a change in the distance between the two electrodes (due to the movement of the moving element) can lead to a change in capacitive measurement.

[0003] Typically, MEMS devices exhibit an imprinted capacitance, primarily determined by the two electrodes, and a parasitic capacitance of the MEMS device itself. The capacitance change, indicative of the movement of the moving element, is often relatively small compared to the total capacitance of the MEMS device. To compensate for manufacturing-related variations, especially those related to the parasitic capacitance, funds are allocated for offsetting. Consequently, there is a need for an improved method that allows for the reduction of parasitic capacitance. SUMMARY

[0004] One embodiment of the disclosure provides a MEMS device comprising a fixed electrode and a movable electrode. The movable electrode is arranged in an insulated manner and spaced apart from the fixed electrode. The movable electrode is suspended relative to the fixed electrode by means of one or more spacers comprising an insulating material, the movable electrode being laterally attached to the one or more spacers.

[0005] Another embodiment provides a MEMS device comprising a substrate and a movable electrode. The substrate includes a fixed electrode. The movable electrode is insulated and spaced apart from the fixed electrode, which has a rectangular shape. The movable electrode is suspended relative to the fixed electrode by one or more spacers having an insulating oxide at their corners, with the movable electrode being laterally attached to the spacer(s). The distance between the fixed electrode and the movable electrode is variable, and a change in the distance results in a change in capacitance.

[0006] According to a further embodiment, a MEMS device comprises a fixed electrode and a movable electrode, which is arranged insulated and spaced apart from the fixed electrode. The movable electrode is suspended relative to the fixed electrode by means of one or more spacers comprising an insulating material, the movable electrode being laterally attached to the one or more spacers. The base area of ​​one or more spacers is at least twenty times smaller than the base area of ​​the movable electrode.

[0007] Another embodiment provides a method for manufacturing a MEMS device. The method comprises providing a sacrificial layer on a fixed electrode, providing a movable electrode on the sacrificial layer such that a layer stack comprising the sacrificial layer and the movable electrode is formed. Furthermore, the method comprises providing one or more spacers adjacent to the layer stack, which include an insulating material, such that the movable electrode is laterally attached to one or more spacers, and removing the sacrificial layer at least in a section that is aligned with a section of the movable electrode, such that the movable electrode is spaced apart from the fixed electrode. This results in the movable electrode being suspended relative to the fixed electrode by means of the one or more spacers. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the following, embodiments of the present disclosure are discussed with reference to the accompanying drawings, wherein

[0009] Fig. Figure 1 shows a schematic cross-sectional view of a MEMS device with two electrodes which, according to a first embodiment, are suspended relative to each other by means of one or more spacers;

[0010] Fig. 2a and Fig. 2b show a cross-sectional view and a top view of another MEMS device according to an embodiment;

[0011] Fig. 3a to Fig. 3f successive steps of a process for manufacturing the MEMS device of Fig. 2a and Fig. 2b show;

[0012] Fig. 4a shows a top view of a MEMS device which, according to one embodiment, is used as an accelerometer;

[0013] Fig. 4b shows a top view of a MEMS device used as a pressure sensor according to one embodiment; and

[0014] Fig. 5a and Fig. 5b shows a cross-sectional view and a top view of a further MEMS device comprising two electrodes which, according to a further embodiment, are suspended relative to each other by means of one or more spacers embedded in one of the electrodes. DETAILED DESCRIPTION

[0015] In the following, various embodiments of the teachings disclosed herein are described with reference to Fig. 1 to Fig. 5 discussed, wherein in the drawing objects with completely identical or similar functions have been given the same reference numerals, so that objects which in different embodiments are designated with completely identical reference numerals are interchangeable and the description thereof is applicable to all.

[0016] Fig. Figure 1 shows a cross-sectional view of a MEMS device 10 with a fixed electrode 12 and a movable electrode 14 Here are the fixed electrodes 12 and the movable electrode 14 arranged so that both are spaced apart 16 in between, opposite each other. In one embodiment, the two electrodes are 12 and 14 essentially parallel to each other. The two electrodes 12 and 14 are by means of one or more spacers 18 spaced apart from each other. One or more spacers are placed between two electrodes. 12 and 14 arranged and attached to the same. In detail: The spacers 18 can be achieved using a main surface 12m , the movable electrode 14 is facing the fixed electrode 12It should be attached. Furthermore, the spacers are 18 by means of an end face 14f the movable electrode 14 at the movable electrode 14 attached; i.e., that one or more spacers 18 Adjacent to the side of the movable electrode 14 (and consequently adjacent to each other laterally). The reason for the lateral arrangement of the movable electrode 14 and the spacers 18 This will be discussed below, following a discussion of the overall structure and functionality of the MEMS device. 10 .

[0017] The solid electrode 12 If the electrode is stationary, it can, for example, be attached to a substrate (not shown). Conversely, the movable electrode is 14 at least along a first direction (through the arrow) 16(illustrated) movable. To achieve the movement, the movable electrode forms or possesses 14 a deformation zone. Alternatively, the deformation zone can be located at the connection or boundary line between the movable electrode. 14 and the spacer 18 or from the spacer 18 be self-formed. In general, this means with regard to one or more spacers. 18 that the purpose of one or more spacers 18 This consists of a suspension for the movable electrode. 14 with regard to the fixed electrode 12 to accomplish.

[0018] The two electrodes 12 and 14 form a capacitance, therefore the two electrodes 12 and 14 insulated from each other. That's why the spacers 18 an insulating material, such as an oxide or a nitride. Alternatively, the spacer can be18 have a different insulating material, for example monosilicon, wherein a doping is selected such that the monosilicon is non-conductive.

[0019] The range of motion is designed such that the distance 16 is variable. A change in distance 16 This causes a change in capacitance. Consequently, a change in distance or movement of the movable electrode is necessary. 14 Detectable due to the change in capacitance. Thanks to the lateral connection between the movable electrode. 14 and the spacers 18 by means of the end faces 14f It can be avoided that large sections of the electrodes 12 and 14with an oxide layer in between, facing each other, it should be noted that these regions typically give rise to parasitic capacitances. This is because parasitic capacitance is primarily caused in regions of the oxide, or more generally, the dielectric, due to the difference in capacitance compared to the dielectric constant ε. Hohlraum of the cavity (here 1.0, cf. the area marked 16) increased dielectric constant ε Abstandsstück (e.g., for an oxide 3,9). Consequently, the structure of the MEMS device enables 10 , to reduce the areas that are primarily responsible for the parasitic capacitance. In other words, this embodiment has the advantage that the capacitance is mainly determined by the overlap area of ​​the two electrodes. 12 and 14 and the distance 16 between the two electrodes 12 and 14 is determined. Consequently, the MEMS device10 a reduced parasitic capacitance compared to state-of-the-art MEMS devices, thanks to the type of suspension of the movable electrode. 14 This leads to improved electrical characteristics. A key effect is that the circuit for evaluating the movement of the movable electrode is no longer required. 14 no means for offsetting the signal from the device 10 needed.

[0020] With reference to Fig. 2a and Fig. 2b describes another embodiment of a MEMS device 10' discussed. The MEMS device 10' is here in Fig. 2a shown in a cross-sectional view (AA), wherein Fig. 2b a top view of the device 10' shows. The device 10' includes a substrate 20 , on which the solid electrode 12 is formed, or more generally, that the solid electrode 12 includes the second electrode. 14is with the distance 16 above the surface 12m arranged. According to this embodiment, the movable electrode 14 using several spacers 18a , 18b , 18c and 18d suspended. In this case, the electrode forms a membrane. 14 and has a deformation zone located next to or at the boundary between the membrane 14 and the spacers 18a , 18b , 18c and 18d lies. The several spacers 18a , 18b , 18c and 18d are at the corners of the movable electrode 14 with openings in between. It should be noted that the openings are indicated by the reference symbols. 19a , 19b , 19c and 19d are marked. As can be seen from the embodiment of Fig. As can be seen in 2b, the openings are 19a , 19b , 19c and 19don the long sides of the rectangular membrane 14 arranged.

[0021] As seen especially from above 2b What can be seen is the added base area of ​​the several spacers. 18a , 18b , 18c and 18d compared to the base area of ​​the movable electrode 14 significantly smaller. For example, the ratio between the two base areas can be 1:10, 1:20, or even 1:100. This is based on an example size of the movable electrode. 14 The base area of ​​each spacer is 35 μm × 35 μm (up to 200 μm × 200 μm). 18a , 18b , 18c or 18d smaller than 70 μm or smaller than 20 μm 2 (less than 5% or 1% of the base area of ​​the movable electrode 14 The base area is equal to the sum of all spacers. 18a , 18b , 18c and 18din relation. Consequently, the respective base area of ​​a single spacer can 18a , 18b , 18c or 18d less than 2.5% or even less than 0.25% of the base area of ​​the movable electrode 14 be (depending on the number of spacers) 18a , 18b , 18c and 18d This leads to the advantage of the improved electrical characteristic discussed above.

[0022] According to another embodiment, one of the spacers can be attached to 18a , 18b , 18c or 18d a leader 26 be arranged to accommodate the movable electrode 14 to connect electrically. This conductor 26 is arranged as a layer that runs along the surface of the spacer 18a is formed in such a way that it separates from the substrate 20 to the movable electrode 14 extends. To extend the conductor from the electrode. 12To isolate, according to another embodiment, the substrate can be 20 an insulator 28 include the one between the leader 26 and the electrode 12 is arranged. According to this further embodiment, the conductor 26 a section 26a include, which is defined by the insulator 28 through into the substrate 20 extends.

[0023] With reference to Fig. 3a to Fig. 3f will describe an exemplary procedure for manufacturing the MEMS device. 10' discussed.

[0024] Fig. Figure 3a shows a first step in providing the substrate. 20 and the fixed electrode 12 on the substrate 20 Then, on the surface 12m the solid electrode 12 a victim class 32 aggravated, as if by Fig. 3b illustrates. In one embodiment, the sacrificial layer can 32over the entire surface 12m the electrode 12 are applied, with the thickness of the sacrificial layer 32 based on the distance 16 is chosen (cf. Fig. 2a).

[0025] The material of the sacrificial layer 32 It can be SiGe or another material that can be etched by isotropic etching. Using SiGe as a sacrificial layer 32 has the advantage that the movable electrode 14 , which, for example, monocrystalline silicon exhibits, can be formed by epitaxy. The etching rate of the sacrificial layer 32 is compared to the etching rate of the membrane 14 or another functional layer (e.g. the electrode) 12 , 14 and 32 or the spacer 18 ) different (e.g. higher) to allow selective (wet or dry) etching of the sacrificial layer 32 to enable.

[0026] Fig. Figure 3c shows the procedure after the movable electrode has been provided. 14 on the victim layer 32 The movable electrode 14 may include polysilicon, monosilicon, or a metal, such as an alloy, with the selected material typically depending on the material of the sacrificial layer. 32 and in particular depends on the technology used to remove the sacrificial layer 32 is used. In detail: Typically, the material used for the movable electrode is... 14 Polysilicon, monosilicon and nitride are used when the MEMS device is manufactured in the initial stage of production (FEOL, Front End of Line), typically using a movable metal electrode. 14 is used when the MEMS device 10'It is manufactured in the final stage of production (BEOL, Back End of Line). It should be noted that monosilicon enables the production of a robust and reliable electrode. 14 This enables a low voltage gradient. Furthermore, the material of the movable electrode is... 14 depending on the material of the spacers 18 (which will be provided during one of the next processes) selected.

[0027] In detail: Fig. Figure 3c illustrates the process of structuring the movable electrode. 14 . Here, the layer stack, which contains the two layers 14 and 32 includes, etched in such a way that the shape, e.g. the rectangular shape, of the movable electrode 14 is determined. In other words, this means that the structure of the layer stack is determined. 14 , 32is determined by applying lithography technologies and / or anisotropic etching technologies. The result of this by Fig. The process illustrated in 3c is a layer stack. 14 , 32 with the desired final shape of the movable electrode 14 .

[0028] The next process, illustrated by Fig. 3D is the provision of the spacers. 18 The process is carried out in such a way that the spacers 18 around the layer stack 14 , 32 are arranged.

[0029] Consequently, the spacers 18 typically to the side of the movable electrode 14 or next to the stack of layers 14 , 32 provided, e.g., by deposition of the spacer oxide. The deposition of the spacer 18 This is done in such a way that the thickness of the spacer 18essentially corresponds to the thickness of the layer stack to create the connection between the movable electrode 14 and the spacers 18 to enable, and in such a way that a good (adherent) connection between the movable electrode 14 and the spacers 18 is achieved.

[0030] The spacers 18 They can be provided in a structured manner, e.g., using a mask, such that the footprint is as small as possible to reduce parasitic capacity, as explained above. Providing the spacers 18 In a structured way, it simultaneously allows one to provide them in such a way that the openings (cf. Fig. 19a, Fig. 19b, Fig. 19c and Fig. 19d) are arranged in between. These openings are intended to allow the removal of the sacrificial layer in one of the subsequent processes. Alternatively, the shape of the spacers can be 18 and consequently the base area as well as the openings of the spacers 18 can be subsequently limited by a different (e.g., anisotropic) etching process.

[0031] As through Fig. As illustrated in section 3e, the next process is intended to reduce the victim layer. 32 They can be removed. This can be done by isotropic (wet or dry) etching. Thanks to the openings between the spacers. 18 Good accessibility is achieved after removing the sacrificial layer. 32 is the movable electrode 14 through the spacers attached to the sides 18 suspended. It should be noted that in one embodiment the sacrificial layer 32completely removed, but alternatively mainly or at least partially, i.e. to more than 75%, 90% or even 99%, with respect to the entire victim layer area 32 , may be far away.

[0032] Fig. Figure 3f shows a final, optional step of the manufacturing process, where the movable electrode 14 electrically contacted. In this process, the electrical conductor 26 on the surface of one of the spacers 18 provided, in such a way that the leader 26 from the substrate 20 to the second electrode 14 extends.

[0033] It should be noted that the described manufacturing process may optionally include further processes, such as polishing or planarizing.

[0034] Fig. 4a shows another MEMS device 10'' , which the MEMS device 10' from Fig. 2a is essentially the same or similar, wherein the movable electrode 14'' It is designed as a cantilever arm. The hammer-shaped cantilever arm 14'' is achieved by means of two spacers, namely the spacers 18a and 18b , suspended. As for the other elements, namely the first electrode 12 , the substrate 20 , the leader 26 and the insulator 28 As far as the MEMS device is concerned, 10'' the MEMS device 10' the same or similar. The MEMS device shown 10'' It can be used as an accelerometer. According to another embodiment, the accelerometer can 10'' include a lid that attaches to the substrate 20 is arranged such that the MEMS structure with the two electrodes 12 and 14'' ( 14 ) is shielded from the environment.

[0035] Fig. 4b shows another MEMS device 10'''The further MEMS device 10''' is the MEMS device 10' from Fig. 2a essentially the same or similar, wherein the openings 19a , 19b , 19c and 19d by additional spacers 36a , 36b , 36c and 36d are sealed. Due to the additional spacers 36a , 36b , 36c and 36d forms the movable electrode 14 a closed membrane, so that the cavity between the two electrodes 12 and 14 It is hermetically sealed. This allows the use of the MEMS device. 10''' for various applications. For example, the closed membrane enables 14 The formation of a pressure sensor due to the fact that a pressure difference between the pressure inside the closed cavity and the external pressure leads to a deformation of the membrane. 14leads to capacitive measurement, as explained above.

[0036] From a manufacturing perspective, it should be noted that the spacers 36a , 36b , 36c and 36d on the substrate 20 or on the fixed electrode 12 be formed after the victim layer (cf. Fig. 3e) has been removed.

[0037] Even though, in the embodiments discussed above, the spacers were discussed in the context of a spacer arrangement in which the spacers are positioned around the movable electrode 14 When arranging the spacers, it should be noted that one or more spacers may also be located within the electrode area. 14 They may be arranged. Such an arrangement is discussed below.

[0038] Fig. 5a and Fig. 5b shows another MEMS device 10'''', wherein the MEMS device 10'''' in Fig. 5a by a cross-sectional view (AA) and in Fig. Figure 5b is illustrated by a top view. The MEMS device 10'''' The substrate includes 20 with the fixed electrode 12'''' and the movable electrode 14'''' , which in relation to the surface 12m the solid electrode 12 through the distance 16 is arranged at a distance. As illustrated, the movable electrode 14'''' using a spacer 18'''' suspended within an area of ​​the movable electrode 14 is located. This means that the spacer is 18'''' from the surface 12m through the movable electrode 14'''' extends so that the spacer 18'''' into the movable electrode 14'''' is embedded.

[0039] Alternatively, the MEMS device shown can be used 10''''also several in the movable electrode 14'''' embedded spacers 18'''' include. According to a further embodiment, the conductor can be used to electrically connect the movable electrode. 14'''' inside the spacers 18'''' be arranged (not shown).

[0040] The manufacture of the MEMS device 10'''' This process is essentially similar to the manufacturing of the previously discussed MEMS devices. Here, during the process of defining the shape of the movable electrode... 14'''' a hole for the spacer 18'''' (through which the spacer 18'''' (should extend) in the movable electrode 14'''' and the victim class 32 created (cf. Fig. 3c). Integrating the one or more holes for the one or more spacers 18'''' into the movable electrode 14''''may be based on lithography technologies and / or anisotropic etching.

[0041] With regard to Fig. 2a, Fig. 2b and on Fig. 4a It should be noted that the MEMS shown 10' and 10'' They can be used as humidity sensors. In this process, a film of liquid that adheres to the membrane changes the temperature. 14 attached, for example proportionally the capacity of the MEMS device 10' or 10'' , so that a detectable capacitance can be inferred from the corresponding moisture level. This change in capacitance, caused by the liquid film, is quite small, making the principle described above, which allows one to avoid or reduce parasitic capacitance, advantageous.

[0042] According to further embodiments, the MEMS device forms 10' a bolometer. It is advantageous here that the material of the spacers 18a ,18b , 18c and / or 18d depending on a desired thermal conductivity, e.g. a reduced one.

[0043] Even if the membrane 14 In the context of a rectangular membrane, it should be noted that the shape of the membrane 14 It can be different, for example round.

[0044] Referring to Fig. 5a and Fig. 5b It should be noted that a MEMS device according to a further embodiment uses spacers 18'''' may include those in the movable electrode 14'''' are embedded, as are spacers 18a , 18b , 18c and 18d , which the electrode 14'''' surrounded, as if by Fig. 2a and Fig. 2b shown.

[0045] In general, the embodiments described above merely illustrate the basic idea of ​​the present disclosure. It is understood that modifications and variations of the arrangements and details described herein will be obvious to other persons skilled in the art. Therefore, it is intended that the scope of protection be limited only by the appended claims and not by the specific details presented here for description and explanation.

Claims

[1] MEMS device, comprising: a fixed electrode; and a movable electrode that is arranged in an insulated manner and spaced apart from the fixed electrode by a distance; wherein the movable electrode is suspended in relation to the fixed electrode by means of one or more spacers comprising an insulating material, wherein the movable electrode is attached laterally to the one or more spacers. [2] MEMS device according to claim 1, wherein the solid electrode is formed by a substrate or attached to a substrate. [3] MEMS device according to claim 1 or 2, wherein the movable electrode has a square shape and wherein the movable electrode is suspended at one or more corners of the movable electrode by means of one or more spacers. [4] MEMS device according to one of claims 1 to 3, wherein the one or more spacers are embedded in the movable electrode. [5] MEMS device according to any one of claims 1 to 4, wherein one or more spacers comprise an oxide or nitride. [6] MEMS device according to any one of claims 1 to 5, wherein the one or more spacers comprise a different material or lattice structure compared to the material or lattice structure of the movable electrode. [7] MEMS device according to any one of claims 1 to 6, wherein a base area of ​​one or more spacers is at least 10 times smaller compared to a base area of ​​the movable electrode. [8] MEMS device according to any one of claims 1 to 7, wherein the distance between the fixed electrode and the movable electrode is variable and wherein a change in distance leads to a change in capacitance. [9] MEMS device according to any one of claims 1 to 8, wherein the movable electrode is electrically contacted by means of a conductor arranged on one of the one or more spacers. [10] MEMS device according to any one of claims 1 to 9, wherein the one or more spacers are separated from each other by an opening extending along the movable electrode. [11] MEMS device according to one of claims 1 to 10, wherein the movable electrode is designed as a cantilever arm. [12] MEMS device according to claim 11, wherein the MEMS device forms an accelerometer or a humidity sensor. [13] MEMS device according to any one of claims 2 to 12, wherein the one or more spacers have a material which has a reduced thermal conductivity compared to a material of the movable electrode or the substrate. [14] MEMS device according to claim 13, wherein the MEMS device forms a bolometer. [15] MEMS device according to one of claims 10 to 14, wherein a further spacer is arranged in the area of ​​the opening to hermetically seal a cavity under a membrane formed by the movable electrode. [16] MEMS device according to claim 15, wherein the MEMS device forms a pressure sensor. [17] MEMS device comprising: a substrate with a solid electrode; and a movable electrode which is arranged in an insulated manner and spaced apart from the fixed electrode by a distance, wherein the movable electrode has a square shape; wherein the movable electrode is suspended from the fixed electrode by means of one or more spacers having an insulating oxide at their corners, wherein the movable electrode is attached laterally to the one or more spacers; wherein the distance between the fixed electrode and the movable electrode is variable and wherein a change in distance leads to a change in capacitance. [18] MEMS device comprising: a fixed electrode; and a movable electrode that is arranged in an insulated manner and spaced apart from the fixed electrode by a distance; wherein the movable electrode is suspended from the fixed electrode by means of one or more spacers comprising an insulating material, wherein the movable electrode is attached laterally to the one or more spacers, wherein the base area of ​​one or more spacers is at least 20 times smaller than the base area of ​​the movable electrode. [19] Method for manufacturing a MEMS device, comprising: Providing a sacrificial layer above a fixed electrode; Providing a movable electrode above the sacrificial layer in such a way that a layer stack comprising the sacrificial layer and the movable electrode is formed; Providing one or more spacers comprising an insulating material adjacent to the layer stack, such that the movable electrode is attached laterally to the one or more spacers; and Removing the sacrificial layer at least in a section that is aligned with a section of the movable electrode, such that the movable electrode is spaced from the fixed electrode by a distance which is related to the thickness of the sacrificial layer; wherein the movable electrode is suspended by means of one or more spacers a of the fixed electrode. [20] Method according to claim 19, wherein the provision of one or more spacers is carried out in such a way that an opening is formed between them. [21] Method according to claim 19 or 20, wherein providing the one or more spacers comprises anisotropic etching and / or applying lithography to define a base area of ​​the one or more spacers. [22] Method according to claim 21, wherein the anisotropic etching and / or application of lithography is carried out such that the base area of ​​one or more spacers is at least 10 times smaller than the base area of ​​the movable electrode. [23] Method according to any one of claims 20 to 22, wherein the removal of the sacrificial layer comprises etching or isotropic etching through the opening. [24] Method according to any one of claims 20 to 23, further comprising closing the opening by means of a further spacer after the sacrificial layer has been removed. [25] Method according to any one of claims 19 to 24, further comprising determining the area of ​​the layer stack by applying lithography and / or anisotropic etching prior to providing one or more spacers. [26] Method according to claim 25, wherein determining the area of ​​the layer stack comprises forming at least one hole in the layer stack for the one or more spacers, and wherein the one or more spacers are embedded in the movable electrode. [27] Method according to any one of claims 19 to 26, wherein the removal of the sacrificial layer takes place in a section in which the fixed electrode is aligned with the entire movable electrode. [28] Method according to any one of claims 19 to 27, wherein the etching rate of the sacrificial layer differs from the etching rate of the membrane and / or the spacer.

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