MEMS configuration and procedure for operating the MEMS configuration

Abstract

The invention relates to a MEMS arrangement comprising: a membrane and a first fixed counter electrode, wherein the first counter electrode is configured to generate a first electrostatic force on the membrane when a first electrical voltage is applied between the membrane and the first counter electrode, in order to reduce a restoring force of the membrane generated when the membrane is deflected towards the first counter electrode. The invention further relates to a method for operating the MEMS arrangement.

Description

[0001] The invention relates to a MEMS arrangement, in particular a MEMS microphone or a MEMS pressure sensor, in particular a MEMS relative pressure sensor, and a method for operating the MEMS arrangement. State of the art

[0002] The patent specification KR 10-1496817 B1 discloses a MEMS converter.

[0003] The published patent application CN 107872760 A discloses a MEMS converter.

[0004] The published patent application DE 10 2014 212 340 A1 discloses a microphone. Disclosure of the invention

[0005] The object underlying the invention is to provide a MEMS arrangement.

[0006] The object underlying the invention is to provide a method for operating the MEMS arrangement.

[0007] These objects are achieved by means of the respective subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the respective dependent subclaims.

[0008] According to a first aspect, a MEMS arrangement, in particular a MEMS microphone or a MEMS pressure sensor, in particular a MEMS relative pressure sensor, is provided, comprising: a membrane and a first fixed counter electrode, wherein the first counter electrode is configured to generate a first electrostatic force on the membrane upon application of a first electrical voltage between the membrane and the first counter electrode in order to reduce a restoring force of the membrane generated upon deflection of the membrane in the direction of the first counter electrode.

[0009] According to a second aspect, a method for operating the MEMS device according to the first aspect is provided, comprising the following steps: Applying a first electrical voltage between the membrane and the first counter electrode to generate a first electrostatic force on the membrane in order to reduce a restoring force of the membrane generated when the membrane is deflected in the direction of the first counter electrode

[0010] The invention is based on and incorporates the finding that the above-mentioned object is achieved by a stationary electrode arranged at a distance from the membrane, which generates an electrostatic force on the membrane. This force is designed to reduce the membrane's restoring force and thus achieve mechanical softening of the membrane.

[0011] This provides the technical advantage that a MEMS array, especially a MEMS microphone or MEMS pressure sensor, can be realized and operated with high sensitivity. In particular, this enables a sensitive MEMS array with a small backside volume. Furthermore, it also enables a sensitive MEMS array with a stiff but low-noise membrane.

[0012] An example of a MEMS device is a MEMS microphone. An example of a MEMS device is a MEMS pressure sensor, particularly a MEMS relative pressure sensor.

[0013] The MEMS microphone has, for example, a pressure equalization hole, in particular through a transducer structure of the MEMS microphone, through which a pressure equalization, in particular quasi-static, is enabled.

[0014] Statements regarding a MEMS microphone apply analogously to a MEMS array, in particular to a MEMS pressure sensor. Therefore, whenever "MEMS microphone" is written, it should always be read as "MEMS array" or "MEMS pressure sensor," and vice versa.

[0015] In one embodiment, the MEMS arrangement comprises a second fixed counter electrode, wherein the membrane is arranged between the first and the second counter electrode, wherein the second counter electrode is configured to generate a second electrostatic force that substantially cancels the first electrostatic force upon application of a second electrical voltage between the membrane and the second counter electrode.

[0016] This results in the technical advantage, for example, that the two electrostatic forces cancel each other out and the membrane does not deflect. This means that the resting point of the membrane is the same or approximately the same with and without voltage. This can be achieved, for example, by ensuring equal distances between the membrane and the electrodes, equal areas, and equal voltages between the membrane and the electrodes. For example, a change in one or two of these parameters can be compensated for by an appropriate combination of the third parameter, so that the membrane is in the same position at rest with and without applied voltage. A parameter, for example, is: distance between membrane and counter electrode, applied electrical voltage, or area.

[0017] In one embodiment, the MEMS arrangement comprises at least one mechanical stop for the membrane, against which the membrane strikes when a restoring force is generated upon deflection of the membrane in the direction of one of the counter electrodes, which restoring force is greater than the electrostatic force generated by the corresponding counter electrode when striking the mechanical stop.

[0018] This results in the technical advantage, for example, of high robustness against overload.

[0019] As a rule, beyond a certain deflection, the electrostatic force of attraction becomes greater than the restoring force. For example, this can occur from a deflection of 60% of the distance between the counter electrode and the diaphragm. If the diaphragm is deflected during operation, for example, by a very large acoustic overload, by more than 60% in this example, the diaphragm is attracted to the stationary counter electrode and will generally not release it without countermeasures.

[0020] The provision of a stop thus provides the technical advantage of eliminating instability in the event of overload. The stop is dimensioned in such a way that the mechanical stop is triggered before the unstable point is reached—that is, the point at which the membrane is attracted to the stationary counter electrode and no longer releases it without countermeasures.

[0021] In one embodiment, the MEMS arrangement comprises an overload detection device which is configured to detect an overload case according to which the membrane is attracted to one of the counter electrodes, wherein the overload detection device is further configured to reduce or switch off the electrical voltage applied to the corresponding counter electrode upon detection of an overload case.

[0022] This provides, for example, the technical advantage of high robustness against overload. Briefly reducing or switching off the electrical voltage also provides the technical advantage of reducing or even eliminating the electrostatic attraction force, allowing the membrane to detach from the electrode again.

[0023] This ensures a high level of robustness against overload.

[0024] In one embodiment of the MEMS arrangement, it is provided that the membrane and one of the counter electrodes each have a comb structure comprising a plurality of comb-shaped fingers, wherein, from a certain deflection of the membrane in the direction of the corresponding counter electrode, the respective comb-shaped fingers of the two comb structures are interlocked.

[0025] This results in the technical advantage, for example, that the electrostatic force approaches a constant value during overload with increasing membrane deflection, thus increasing the restoring force again. The unstable point is only reached when the surfaces of the two electrodes come very close together. This point is essentially determined by the dimensions of the fingers and the distances between them. Therefore, appropriate dimensioning can also significantly improve the overload resistance of the MEMS arrangement.

[0026] The basic idea of ​​the comb-shaped finger arrangement is that, when the electrodes are far apart, the closely spaced fingers electrically approach a plate due to the stray fields, resulting in a force response proportional to the inverse of the square of the distance between the electrodes. If the membrane fingers dip into the fingers of the corresponding electrode, and especially if the fingers are higher than the lateral distance between the fingers, a constant force is generated between the first and second electrodes. In the transition region between these two regions, there is a region with a very linear force response between deflection and force.By appropriately selecting the distances between the electrodes, the height of the fingers, the density of the fingers, the geometry of the recesses in the corresponding electrode and the choice of the applied voltage, this range can be very well controlled and it can be ensured that the rest position of this structure also lies in this range.

[0027] In one embodiment of the MEMS arrangement, it is provided that a height of the fingers is at least a quarter of a gap width between the membrane and the corresponding counter electrode.

[0028] This provides the technical advantage of ensuring that the fingers are dimensioned particularly appropriately.

[0029] Instead of the term “gap”, the term “column” can be used.

[0030] In one embodiment of the MEMS arrangement, it is provided that a gap in the horizontal direction between two fingers is smaller than twice the gap width between the membrane and the corresponding counter electrode.

[0031] This results in the technical advantage, for example, of a particularly favorable dimensioning of this arrangement.

[0032] In one embodiment of the MEMS arrangement, it is provided that a height of the fingers is smaller than a gap width between the membrane and the corresponding counter electrode.

[0033] This results in the technical advantage, for example, of a particularly favorable dimensioning of this structure.

[0034] In one embodiment of the MEMS arrangement, it is provided that a width of the fingers is less than twice the gap width between the membrane and the corresponding counter electrode.

[0035] This results in the technical advantage of particularly favourable dimensioning of this structure.

[0036] In one embodiment of the MEMS arrangement, it is provided that the membrane has an oscillation surface section on which the fingers of the comb structure of the membrane are arranged electrically insulated from the oscillation surface section.

[0037] This provides the technical advantage, for example, of electrically isolating a detection zone from the finger zone. This allows for easy detection of capacitance changes in the detection zone. In this case, the voltage in the detection zone can be independent of the voltage applied to the comb structures, making the electrical analysis simpler.

[0038] In one embodiment, the MEMS arrangement comprises a further membrane which forms a double membrane with the one membrane, wherein one of the counter electrodes is arranged between the two membranes.

[0039] This results in the technical advantage of creating a particularly sensitive MEMS arrangement.

[0040] In one embodiment of the MEMS arrangement, it is provided that at least one of the membranes and one of the counter electrodes is divided into a first region and a second region, which are either completely separated from each other or are connected to each other but are electrically insulated from each other.

[0041] This results in the technical advantage, for example, that the membrane and / or the counter electrode are each divided into two areas that are either completely separate from one another or connected to one another but electrically insulated from one another. This advantageously allows a constant voltage to be applied to a first area and the second area can be used to detect the deflection of the membrane. Especially with particularly sensitive evaluation circuits, it is generally not possible to apply a constant voltage to them simultaneously. Evaluation concepts that keep the charge on the electrodes constant are usually used for this purpose, which is why electrical separation of the counter electrode or the membrane is advantageous in order to separate the two functions.Depending on the desired sensitivity and available voltage, the basic distance between the membrane and the counter electrode can be selected differently depending on the function.

[0042] For example, the area in which a counterforce is generated via an applied electrical voltage can be arranged at the edge of the membrane in a somewhat stiffer area of ​​the membrane, and the detection area can be arranged in the center of the membrane, i.e., in an area where the membrane moves more strongly when sound is applied, thus generating a larger signal. This advantageously allows a large capacitive signal to be generated. At the same time, a correspondingly higher counterforce can be generated at the edge relatively easily by increasing the voltage, since the capacitive force scales proportionally to the square of the applied voltage.

[0043] The electrical separation between detection areas and constant voltage areas described here can only be carried out in the membrane and can only be carried out in the fixed electrode and can be carried out in both the membrane and the fixed electrode.

[0044] The phrase “at least one of the membrane and one of the counter electrodes” means “membrane and / or one of the counter electrodes”.

[0045] “One of the counter electrodes” therefore means, for example, the first counter electrode or the second counter electrode.

[0046] Statements made in connection with one of the counter electrodes also apply analogously to the other of the counter electrodes and vice versa.

[0047] In embodiments that describe only one counter electrode, it can be provided that a second counter electrode is provided, which is formed analogously to the first counter electrode or is formed differently from it.

[0048] The phrase “at least one” means “one or more”.

[0049] The embodiments or embodiments described here can be combined with each other in any way, even if this is not explicitly described.

[0050] “Voltage” means “electrical voltage”.

[0051] “Electrode” means “counter electrode”.

[0052] Statements made in connection with the method apply analogously to the MEMS arrangement and vice versa. This means that the technical functionalities of the method result analogously from the corresponding technical functionalities of the MEMS arrangement and vice versa.

[0053] The invention is explained in more detail below using preferred embodiments. These show: Fig. 1 a cross-sectional view of a MEMS microphone, Fig. 2 a graph, Fig. 3 a cross-sectional view of another MEMS microphone, Fig. 4 a graph, Fig. 5 to 7 each show a cross-sectional view of a MEMS microphone, Fig. 8 a graph, Fig. 9 to 22 show different steps of a manufacturing process for a MEMS microphone, Fig. 23 a MEMS microphone and Fig. 24 another MEMS microphone.

[0054] In the following, the same reference symbols may be used for identical features. Furthermore, for the sake of clarity, not all features in each figure are provided with their own reference symbol.

[0055] The following explains the concept described here using one or more MEMS microphones as an example. The corresponding explanations apply generally to MEMS arrays. This means that "MEMS array" can also be used instead of "MEMS microphone."

[0056] Fig. 1 shows a MEMS microphone 101.

[0057] The MEMS microphone 101 comprises a membrane 103 and a first fixed counter electrode 105 and a second fixed counter electrode 107. The membrane 103 is arranged between the two counter electrodes 105, 107.

[0058] Furthermore, the MEMS microphone 101 comprises a carrier 109, which is, for example, a substrate, wherein the two counter electrodes 105, 107 and the membrane 103 are connected to or arranged on the carrier 109.

[0059] A first layer 111 is located between the second counter electrode 107 and the membrane 103. A second layer 113 is located between the membrane 103 and the first counter electrode 105. A third layer 115 is located between the first counter electrode 105 and the carrier 109. An electrical contact 117 is provided on the second counter electrode 107, via which the second counter electrode 107 can be electrically contacted.

[0060] Layers 111, 113, and 115 are oxide layers. They serve as electrical insulation and, at the same time, sacrificial layers in the exposed area. This means that the first layer 111 provides electrical insulation between the second counterelectrode 107 and the membrane 103. This means that the second layer 113 provides electrical insulation between the membrane 103 and the first counterelectrode 105. This means that the third layer 115 provides electrical insulation between the first counterelectrode 105 and the carrier 109.

[0061] It should be noted here that a sacrificial layer, as defined in the description, can be, for example, a dielectric layer, i.e., an electrically insulating layer. The dielectric layer can be, for example, an oxide layer, i.e., SiO2. The dielectric layer can, for example, simultaneously be used as a sacrificial layer for HF etching, i.e., etching with hydrofluoric acid (HF: hydrogen fluoride).

[0062] An etching in the sense of the description is, for example, an HF etching.

[0063] Both counter electrodes 105, 107 have through holes 119, for example, pressure equalization holes, so that sound can reach the membrane 103 and, due to the sound pressure, can deflect it. The first counter electrode 105 is configured, for example, to generate a first electrostatic force on the membrane 103 upon application of a first electrical voltage between the membrane 103 and the first counter electrode 105 in order to reduce a restoring force of the membrane 103 generated upon deflection of the membrane 103 in the direction of the first counter electrode 105.

[0064] The second counter electrode 107 is configured, for example, to generate a second electrostatic force that substantially cancels out the first electrostatic force when a second electrical voltage is applied between the membrane 103 and the second counter electrode 107.

[0065] In Fig. 1, the MEMS microphone 101 comprises two fixed counter electrodes 105, 107. For example, it may be provided that the MEMS microphone 101 has only one counter electrode, for example, only the second fixed counter electrode 107, i.e., an electrode arranged above the membrane 103. In such an embodiment, the second fixed counter electrode 107 is then referred to as a first counter electrode.

[0066] Such, in Fig. 1 Although not shown, but which for example in Fig. 5 or also in Fig. 24, is therefore directed to a configuration according to which the fixed counter electrode is arranged in a parallel plate arrangement to the membrane 103. During operation, a constant electrical voltage is applied between the membrane 103 and the fixed electrode. The mechanical restoring force is, to a good approximation, proportional to the deflection of the membrane. Likewise, the restoring force of the membrane caused by the limited backside volume is, to a good approximation, proportional to the deflection of the membrane.

[0067] The electrostatic force between the movable membrane and the stationary electrode is proportional to the inverse of the square of the distance between the membrane and the stationary counter electrode. This means that the electrostatic force counteracts the two restoring forces and increases the further the membrane deflects.

[0068] This is shown by the graph according to Fig. 2 shown.

[0069] Fig. Figure 2 shows a graph 201 comprising an abscissa 203 and an ordinate 205. The abscissa 203 represents a deflection of the membrane relative to a rest position defined by zero. The unit of the ordinate 205 is Newton, thus the force is plotted on the ordinate 205.

[0070] Reference numeral 207 indicates a curve for the membrane's restoring force. Reference numeral 209 indicates a curve for the electrostatic force. Reference numeral 211 indicates a curve for the sum of the restoring force and the electrostatic force.

[0071] The applied voltage thus exerts a force, an electrostatic force, on the membrane, which leads to a pre-deflection, the point marked by reference numeral 213, here, for example, 15%. As can be seen in graph 201, the applied voltage causes the total force, i.e., the sum of the restoring force and the electrostatic force, to change less upon deflection around this new rest point. The slope of curve 215 is lower around its zero point than the slope of curve 207 at its zero point. The total force therefore changes less upon deflection around the new rest point than is the case around the zero point without an applied voltage.

[0072] The advantage of an arrangement comprising a single, fixed counter electrode is that the effect can be achieved simply by applying a constant voltage. No control mechanism is required. This allows the MEMS microphone to be operated efficiently and simply. Noise caused by a control mechanism can also be advantageously avoided.

[0073] According to the presentation in Fig. 1, two fixed counter electrodes are provided, with an electrical voltage being applied to both electrodes 105, 107 relative to the membrane 103. This advantageously cancels out the two electrostatic forces and prevents the membrane 103 from deflecting, so that the resting point of the membrane 103 is the same or approximately the same with and without voltage.

[0074] This is exemplified by the Fig. 4, which shows a graph 401. The abscissa 403 represents the deflection of the membrane relative to its rest position. The force is again plotted on the ordinate 405. Reference numeral 407 denotes a curve for the restoring force of the membrane 103. Reference numeral 409 denotes a curve for the electrostatic force generated by the first counter electrode 105. Reference numeral 411 denotes a curve for the electrostatic force generated by the second counter electrode 107. Reference numeral 413 denotes a curve for the sum of the restoring force, the first electrostatic force, and the second electrostatic force.

[0075] As in Fig. 4 by the graph 401, the rest point of the membrane 103 is the same or approximately the same with and without voltage.

[0076] In the simplest case, this can be achieved by maintaining equal distances between membrane 103 and the two electrodes 105, 107, and by maintaining equal areas and equal voltage between membrane 103 and the fixed counter electrodes 105, 107. Alternatively, a change in one or two of these parameters—distance, area, and voltage—can be compensated for by appropriately compensating the third parameter, so that membrane 103 is in the same position in the resting state, both with and without an applied voltage.

[0077] It is possible that with a fixed counter electrode in a parallel plate arrangement, the electrostatic force of attraction becomes greater than the restoring force above a certain deflection of the diaphragm. For example, this can be achieved with a deflection of 60% of the distance between the counter electrode and diaphragm. If the diaphragm is deflected during operation by more than the 60% shown here as an example, for example due to a very large acoustic overload, the diaphragm is attracted to the fixed counter electrode and will not let go without countermeasures. It is therefore advantageous, as is provided according to one embodiment, to provide detection of such an overload, for example by providing an overload detection device, so that in the event of an overload, for example, the voltage between the diaphragm and the fixed counter electrode is switched off or reduced, at least for a predetermined period of time.

[0078] In order to ensure particularly high robustness against overload, it is provided, for example, that a fixed counter electrode is provided on both sides of the membrane, which in Fig. 1 is shown.

[0079] The same applies to a fixed electrode arranged between two mechanically coupled membranes, i.e., a double membrane. In such an arrangement, the point at which the system becomes unstable and the membrane is attracted to a counter electrode is almost the same, but the ground-state deflection is absent or significantly reduced. Thus, a greater deflection and thus a higher overload is required to reach this point. Furthermore, the double-electrode arrangement allows for greater force compensation, so that, with the same force compensation, the point at which the system becomes unstable occurs later.

[0080] To achieve a system that does not exhibit instability under overload conditions, it is intended to provide overload stops, which are dimensioned, for example, to cause a mechanical stop before the unstable point is reached. This is exemplified in Fig. 3 is shown by another MEMS microphone 301. Reference numeral 307 denotes such mechanical stops. Here, the mechanical stops 307 are provided on the diaphragm 103.

[0081] Further in Fig. 3 shows by way of example that the second counter electrode 107, which also applies analogously to the first counter electrode 105, is divided into a first region 303 and a second region 305, which are, for example, completely separate from one another or connected to one another but electrically insulated from one another. The two regions 303, 305 are thus electrically insulated from one another. As a result, a constant electrical voltage can be applied to the first region 303 and the second region 305 can be used to detect the deflection of the membrane 103. In particular, with particularly sensitive evaluation circuits, it is generally not possible to apply a constant voltage to these circuits simultaneously. Evaluation concepts that keep the charge on the electrodes constant are usually used for this purpose, which is why electrical separation of the counter electrode is advantageous for separating the two functions.Depending on the desired sensitivity and available voltage, it may also be advantageous to choose the basic distance between membrane 103 and counter electrode 107 or 105 differently depending on the function.

[0082] For example, it may also be provided to arrange the region in which a counterforce is generated via an electrically applied voltage at the edge of the membrane 103 in a somewhat stiffer area of ​​the membrane 103, and to arrange the detection region in the center of the membrane 103, i.e., in the region in which the membrane moves more strongly when sound is applied and thus generates a larger signal. This generates a large capacitive signal. At the same time, a correspondingly higher counterforce can be generated at the edge relatively easily by increasing the voltage, since the capacitive force scales proportionally to the square of the applied voltage.

[0083] An advantageous electrical separation between detection areas and areas with constant voltage can alternatively also be achieved in a membrane or in a membrane and in the fixed electrode together.

[0084] In the Fig. 5 to 7 each show a further MEMS microphone 501 comprising a diaphragm 103 and a first fixed counter electrode 503. The diaphragm 103 has a first comb structure 509 having a plurality of comb-shaped fingers 511 arranged on a vibration surface portion 512 of the diaphragm 103. The first fixed counter electrode 503 has a second comb structure 505 having a plurality of comb-shaped fingers 507.

[0085] It is provided that, starting from a certain deflection of the membrane 103 in the direction of the first fixed counter electrode 503, the respective comb-shaped fingers 507, 511 of the two comb structures 505, 509 are interlocked.

[0086] Fingers of a comb structure in the sense of the description can also be referred to as columns or stripes.

[0087] By way of example, an arrangement is thus proposed according to which the height of the fingers is dimensioned such that the respective fingers of the comb structures do not touch each other in the rest position of the membrane, but can dip into corresponding recesses upon deflection.

[0088] The basic idea of ​​such an arrangement is in particular that with a large distance between the counter electrode and the membrane, the closely spaced columns or strips, i.e. the fingers, electrically come very close to a plate due to the stray fields and thus have a force behavior that is proportional to the inverse of the square of the distance between the membrane and the corresponding counter electrode.

[0089] This is exemplified by graph 801 according to Fig. 8. The abscissa 803 represents a deflection of the membrane from its rest position. The ordinate 805 represents a force. Reference numeral 807 denotes a profile of the membrane's restoring force. Reference numeral 809 denotes a profile of the electrostatic force generated by the counter electrode. Reference numeral 811 denotes a profile of the sum of the restoring force and the electrostatic force.

[0090] A region of the curve 809 is marked by a curly bracket with the reference number 812, wherein in this region the force behavior is proportional to the inverse of the square of the distance between membrane and electrode.

[0091] If the fingers are inserted into the corresponding recesses, and in particular if the fingers are much higher than a lateral distance between the fingers and the corresponding counter electrode, a constant force is generated between the membrane and the counter electrode, which is represented by a region marked by a curly bracket with the reference number 815 of the curve 809. In a transition region, the region marked by a curly bracket with the reference number 813, between these regions 812, 815, a very linear force behavior between deflection and force is effected by this arrangement.

[0092] By appropriately selecting the distances between the membrane and the counter electrode, the height of the fingers, the density of the fingers, the geometry of the recesses between the fingers and the selection of the applied voltage, this region 813 can be very well controlled, so that it can be ensured that the rest position, indicated by an arrow with the reference number 817, of such a MEMS microphone also lies in this very linear region.

[0093] A particularly favorable arrangement for the fingers is, for example, when the fingers have a height of at least a quarter of a gap width between the membrane and the counter electrode.

[0094] A particularly favorable arrangement for the fingers is, for example, when a gap in the horizontal direction between fingers is smaller than twice the gap width between the membrane and the counter electrode.

[0095] A particularly favorable arrangement for the fingers is, for example, when the height of the fingers is less than the gap width between the membrane and the counter electrode.

[0096] A particularly favorable arrangement for the fingers is when the width of the fingers is less than twice the gap width between the membrane and the electrode.

[0097] The comb structures therefore advantageously create an arrangement in which the unstable point, which leads to the diaphragm being attracted to the fixed counter electrode, can be avoided entirely or is only reached at a significantly greater deflection. Furthermore, such an arrangement advantageously enables the electrostatic counterforce in the area around the operating point to be made much more linear, thus enabling a very linear signal to be achieved even for large acoustic signals. In particular, unwanted harmonics, which can be generated by non-linearity in a microphone system, are thus advantageously avoided. A three-dimensional structuring of the diaphragm and counter electrode is therefore proposed in order to change the force behavior between the diaphragm and counter electrode.

[0098] In addition to the good linearity of such an arrangement, such a device has the particular advantage that the electrostatic force approaches a constant value, the 815 range, with increasing deflection during overload, thus increasing the restoring force again. The unstable point is only reached when the respective surfaces of the membrane and counter electrode come very close together. This point is essentially determined by the height of the fingers. Therefore, such an arrangement can also achieve significantly improved overload resistance.

[0099] Fig. 9 to 22 each show different points in time in manufacturing processes for producing a MEMS microphone according to the concept described here.

[0100] According to Fig. 9, a functional layer 905 is deposited and patterned on a substrate 901 or generally on a carrier. For example, a polysilicon layer is deposited. The functional layer 905 can form a counter electrode or a first membrane in the finished MEMS microphone. In the present case, the functional layer 905 will form a first membrane. Between this layer 905 and the substrate 901, a further layer with the reference numeral 903 is provided, which is a dielectric layer, i.e., an electrically insulating layer. The dielectric layer can be, for example, an oxide layer, i.e., SiO2. The dielectric layer can, for example, simultaneously be used as a sacrificial layer for an HF etch, i.e., an etch with hydrofluoric acid (HF: hydrogen fluoride).

[0101] According to Fig. 10, a sacrificial layer 1001 is deposited and structured on the layer 905 so that recesses 1003 are located in the sacrificial layer 1001. A top side of the sacrificial layer 1001 is designated by reference numeral 1005.

[0102] A sacrificial layer 1001 is deposited and structured. For example, an oxide layer is deposited as the sacrificial layer. For example, narrow trenches or holes, the recesses 1003, are etched in the electrode area. For example, a plasma etching process is used, which can etch very vertical structures into the oxide, with the walls deviating by less than 15° from the vertical.

[0103] According to Fig. 11, a functional layer 1101 is deposited on the top side 1005. The functional layer 1101 can be a polysilicon layer. The functional layer 1101 is removed down to the top side 1005, for example, using an etching process, such as a CMP process (CMP stands for "chemical mechanical polishing").

[0104] According to Fig. 12, the functional layer 1101 is removed except for the top side 1005 of the sacrificial layer 1001.

[0105] Another sacrificial layer 1301 is deposited, which according to Fig. 13. The additional sacrificial layer 1301 is deposited on the top side 1005. The additional sacrificial layer can be, for example, an oxide layer.

[0106] For example, these two sacrificial layers are structured. A further functional layer 1401, which will later form the fixed counter electrode, is applied as shown in Fig. 14, deposited and structured. The further functional layer 1401 can be a polysilicon layer. Holes or trenches 1403 are provided above the underlying narrow trenches or holes, which are larger than these. A trench etching process is preferably used for this purpose, which creates etched walls that deviate less than 15° from the vertical. The two sacrificial layers are subsequently removed, for example. Layer 1401 forms a membrane for the MEMS microphone.

[0107] On the Fig. 14, a sacrificial layer 1501 is deposited and partially structured (as in Fig. 15). Trenches and holes 1503 are created, which are, for example, smaller than the underlying trenches or holes 1503. An oxide layer can be deposited as sacrificial layer 1501. Optionally, the oxide layer 1501 is planarized using a CMP process. The trenches or holes 1503 are etched, for example. For example, a plasma etching process is used that etches very vertical structures into the oxide, wherein the walls can deviate by less than 15° from the vertical. In particular, the structuring is not carried out over the entire height of the sacrificial layer 1501. For example, this is carried out using a time-controlled oxide etching using a plasma process.

[0108] A further functional layer, for example, a polysilicon layer, is deposited and patterned. This can be done, for example, as follows. First, a polysilicon layer 1601 is deposited, and then this layer is polished down to the height of the sacrificial layer, i.e., down to the top side 1505 of the sacrificial layer 1501 (see Fig. 16). Then, for example, accessions 1701 (cf. Fig. 17) are etched into the sacrificial layer 1501, for example, to generate corresponding support columns. Subsequently, a further functional layer, in particular a polysilicon layer, 1801 (cf. Fig. 18) is deposited and patterned. This additional functional layer 1801 will form a second membrane in the finished MEMS microphone.

[0109] The sacrificial layers are removed. According to Fig. 19, the sacrificial layers are removed via one or more etching accesses 1901. According to Fig. 20, the etching access(s) 1901 is / are sealed by a layer deposition 2001 or another process and, for example, a negative pressure is enclosed in a cavity 2003 between the two membranes.

[0110] Contact surfaces 2101 can be formed on the surface of the upper membrane (cf. Fig. 21).

[0111] According to Fig. 22, a via 2201 is etched from the back to the lower membrane.

[0112] Fig. 23 shows a complete MEMS microphone 2301 according to the manufacturing method described above and illustrated in the figures.

[0113] The method thus forms a first membrane 2303, the functional layer 905, and a second membrane 2305, the functional layer 1801, i.e. a double membrane, wherein a fixed counter electrode, the functional layer 1401, is provided between these two membranes 2303 and 2305.

[0114] Reference numeral 2307 denotes an electrode region used to detect the deflection of the diaphragms 2303 and 2305. Reference numeral 2309 denotes a region or regions of the electrode 1401 used for stiffness compensation, i.e., for generating an electrostatic force to compensate for the restoring force of the diaphragms 2303, 2305.

[0115] The reference numeral 2311 points to comb structures of the membranes 2303, 2305. These comb structures 2311 each have fingers 2313.

[0116] The reference numeral 2315 points to comb structures of the electrode 1401, wherein these comb structures 2315 each have fingers 2317.

[0117] Fig. 24 shows another MEMS microphone 2401 comprising a carrier 2403, a membrane 2405 and a fixed counter electrode 2407. Reference numeral 2409 indicates a comb structure of the membrane 2405, wherein this comb structure 2409 has a plurality of fingers 2411.

[0118] Reference numeral 2413 indicates an electrical insulation layer formed between the fingers 2411 and the membrane 2405, so that the fingers 2411 are electrically insulated from the membrane 2405.

[0119] The reference numeral 2415 points to a comb structure of the electrode 2407. This comb structure 2415 has several fingers 2417.

[0120] The concept described here is particularly applicable to a fully differential microphone arrangement. In particular, such an arrangement can also realize particularly simple counter electrodes arranged on both sides of a diaphragm (see Fig. 3).

[0121] The concept can be applied in particular to a double membrane with an internal counter electrode (cf. Fig. 23).

[0122] In particular, it is irrelevant whether the cavity enclosed between the membranes is hermetically sealed or open.

[0123] The above statements and the concept described here are not limited to MEMS microphones and are equally valid for MEMS pressure sensors, in particular MEMS relative pressure sensors. Compared to MEMS relative pressure sensors, MEMS microphones can, for example, have an additional pressure equalization hole through a transducer structure, which enables quasi-static pressure equalization. QUOTES CONTAINED IN THE DESCRIPTION

[0000] 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

[0000] KR 10-1496817 B1

[0002] CN 107872760 A

[0003] DE 10 2014 212 340 A1

[0004]

Claims

[1] MEMS arrangement, in particular MEMS microphone (101) or MEMS pressure sensor, comprising: a membrane (103) and a first fixed counter electrode (105), wherein the first counter electrode (105) is configured to generate a first electrostatic force on the membrane (103) upon application of a first electrical voltage between the membrane (103) and the first counter electrode (105) in order to reduce a restoring force of the membrane (103) generated upon deflection of the membrane (103) in the direction of the first counter electrode (105). [2] MEMS arrangement according to claim 1, comprising a second fixed counter electrode (107), wherein the membrane (103) is arranged between the first and the second counter electrode (105, 107), wherein the second counter electrode (107) is arranged to generate a second electrostatic force substantially canceling the first electrostatic force upon application of a second electrical voltage between the membrane (103) and the second counter electrode (107). [3] MEMS arrangement according to claim 1 or 2, comprising at least one mechanical stop (307) for the membrane (103), against which the membrane (103) strikes upon a restoring force generated upon deflection of the membrane (103) in the direction of one of the counter electrodes (105, 107), which is greater than the electrostatic force generated by the corresponding counter electrode (105, 107) upon striking the mechanical stop (307). [4] MEMS arrangement according to one of the preceding claims, comprising an overload detection device which is arranged to detect an overload case according to which the membrane (103) is attracted to one of the counter electrodes (105, 107), wherein the overload detection device is further arranged to reduce or switch off the electrical voltage applied to the corresponding counter electrode (105, 107) upon detection of an overload case. [5] MEMS arrangement according to one of the preceding claims, wherein the membrane (103) and one of the counter electrodes (105, 107) each have a comb structure (505, 509) having a plurality of comb-shaped fingers (507, 511), wherein from a certain deflection of the membrane (103) in the direction of the corresponding counter electrode (105, 107) the respective comb-shaped fingers (507, 511) of the two comb structures (505, 509) are interlocked. [6] MEMS arrangement according to claim 5, wherein a height of the fingers (507, 511) is at least a quarter of a gap width between the membrane (103) and the corresponding counter electrode (105, 107). [7] MEMS arrangement according to claim 5 or 6, wherein a gap in the horizontal direction between two fingers (507, 511) is smaller than twice a gap width between membrane (103) and the corresponding counter electrode (105, 107). [8] MEMS arrangement according to one of claims 5 to 7, wherein a height of the fingers (507, 511) is smaller than a gap width between the membrane (103) and the corresponding counter electrode (105, 107). [9] MEMS arrangement according to one of claims 5 to 8, wherein a width of the fingers (507, 511) is less than twice a gap width between the membrane (103) and the corresponding counter electrode (105, 107). [10] MEMS arrangement according to one of claims 5 to 9, wherein the membrane (103) has a vibration surface section (512) on which the fingers (507, 511) of the comb structure (505, 509) of the membrane (103) are arranged electrically insulated from the vibration surface section. [11] MEMS arrangement according to one of the preceding claims, comprising a further membrane (103) which forms a double membrane with the one membrane (103), wherein one of the counter electrodes (105, 107) is arranged between the two membranes (103). [12] MEMS arrangement according to one of the preceding claims, wherein at least one of the membranes (103) and one of the counter electrodes (105, 107) is divided into a first region (303) and a second region (305), which are either completely separated from each other or are connected to each other but are electrically insulated from each other. [13] A method for operating a MEMS device according to any one of the preceding claims, comprising the following steps: Applying a first electrical voltage between the membrane (103) and the first counter electrode (105) in order to generate a first electrostatic force on the membrane (103) in order to reduce a restoring force of the membrane (103) generated when the membrane (103) is deflected in the direction of the first counter electrode (105).

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