MEMS microphone

Abstract

The invention relates to a MEMS microphone (101, 201, 301, 401), comprising a membrane (103) for receiving a sound pressure, a signal conversion element (111), and a lever element (109), which is coupled to the membrane (103) and to the signal conversion element (111), the lever element (109) being provided for receiving the sound pressure from the membrane (103). When the membrane (103) is deflected, a tilting movement is generated and the generated tilting movement is transmitted to the signal conversion element (111).

Description

Technical Field

[0001] The invention relates to a MEMS microphone. Background Art

[0002] Publication CN 112383869A discloses a piezoelectric MEMS transducer.

[0003] Publication EP 2 579 616 A1 discloses an acoustic transducer.

[0004] The published patent application DE 10 2021 206 005 A1 discloses a micromechanical component for a microphone device.

[0005] The published document DE 10 2014 212 340 A1 discloses a microphone. Summary of the invention

[0006] The object of the present invention is to provide a MEMS microphone.

[0007] This object is achieved by the subject matter of the present invention. Advantageous embodiments of the present invention are further developments.

[0008] According to one aspect, a MEMS microphone is provided, which includes: a membrane for receiving sound pressure, a signal conversion element and a lever element, which is coupled to the membrane and the signal conversion element, wherein the lever element is configured to generate a tilting motion when the membrane is deflected and transmit the generated tilting motion to the signal conversion element.

[0009] The invention is based on and includes the following knowledge: The above-mentioned object is achieved by using a closed or partially closed membrane for detecting the deflection caused by the sound pressure. The membrane is, for example, completely or partially connected to a substrate (usually a carrier) and, for example, spans a cavity in the substrate. It is provided that a lever element is used, which is coupled to the membrane and generates a tilting movement, which is transmitted to a signal converter element. Such a signal converter element, for example, generates a capacitive signal due to the transmitted tilting movement, which is related to the deflection and thus to the sound pressure.

[0010] The membrane therefore does not have to move relative to one or two fixed counter electrodes, which has the result that, on the one hand, the acoustic movement of the membrane is virtually undamped and, on the other hand, very good signal quality can be ensured.

[0011] Thus, a sensitive MEMS microphone with low noise and good linearity can be provided. In this way, a MEMS microphone with good dielectric robustness can also be provided. In addition, such a MEMS microphone can be manufactured simply and cost-effectively.

[0012] The deflection of the membrane is transmitted to the signal conversion element via the lever element. The membrane can be anchored externally on a substrate (usually a carrier), in particular all around, so that very thin membranes can be used which still have high robustness. In addition, very thin and therefore light membranes can also be used.

[0013] For example, a polysilicon film is provided which has a thickness of less than 4 μm, for example a film thickness of 2 μm.

[0014] Due to the anchoring, for example very large but light and therefore sensitive membranes can be used.The membrane as a sound capturing element therefore does not have to be stabilized itself, but is stabilized, for example, by suspending the membrane on a substrate, usually a carrier.

[0015] Furthermore, the lever element can be designed, for example, in such a way that the lever element is light but rigid. The movable part of the signal converter element can also be selected to be light but rigid.

[0016] Lightness and rigidity mean, in particular, that the natural frequency of the pure lever element is high, for example greater than 30 kHz.

[0017] In general, it is advantageously possible to design a microphone with a high natural frequency and simultaneously a high sensitivity in such an arrangement. The natural frequency can be set in a targeted manner, for example, by means of layer stresses in the membrane and / or by means of suspension springs between the membrane and the substrate (usually a carrier), so that even with larger membranes high natural frequencies, i.e. natural frequencies of more than 15 kHz in particular, can be achieved. By clamping the membrane on the substrate, for example, gas flow bypasses can be completely or partially prevented. In addition, a good robustness of the component with respect to particles and liquids can be achieved in this way.

[0018] The abbreviation "MEMS" stands for "Micro-Electro-Mechanical Systems".

[0019] In one embodiment of the MEMS microphone, it is provided that the lever element is attached to the membrane eccentrically or centrally relative to the membrane.

[0020] This results in the technical advantage that a particularly effective attachment of the lever element to the membrane is achieved.

[0021] In the case of a central arrangement, a correspondingly large deflection of the membrane can be effectively transmitted to the signal converter element.

[0022] In one embodiment of the MEMS microphone, provision is made for a recess to be provided in the membrane in the case of a central attachment in order to compensate for different tilting movements between the lever element and the membrane.

[0023] This results in the technical advantage that different tilting movements between the lever element and the membrane can be effectively compensated for.

[0024] In one embodiment of the MEMS microphone, it is provided that the lever element is attached to the membrane at the attachment point in such a way that a tilting movement of the membrane corresponds essentially to a tilting movement of the lever element.

[0025] This results in the technical advantage that a particularly sensitive MEMS microphone is provided in which no additional distortions occur in the signal transducer element, in the lever element or in the membrane when the membrane is deflected.

[0026] In one embodiment of the MEMS microphone, it is provided that the lever element is coupled to the membrane at a distance from the membrane in order to prevent the membrane from striking the lever element.

[0027] This results in the technical advantage that in the event of large deflections, the membrane can be effectively prevented from striking the lever element.

[0028] In one embodiment of the MEMS microphone, it is provided that the lever element is connected to the membrane via a mechanical connecting element, which has a height in a partial region of at least three times the membrane thickness and covers an area of ​​the membrane of less than 25% of the membrane area, in order to compensate for different tilting movements between the lever element and the membrane. The area here refers in particular to the area of ​​the main extension plane of the membrane. The area is in particular the horizontal area of ​​the membrane when the membrane is in the rest position.

[0029] This results in the technical advantage that different tilting movements between lever and membrane can be compensated for.

[0030] In one embodiment, the MEMS microphone comprises a carrier, in particular a substrate, on which the membrane, the signal conversion element and the lever element are arranged, wherein the membrane is at least partially attached to, in particular suspended from, the carrier via at least one spring.

[0031] This results in the following technical advantage, for example: stresses can be effectively reduced.

[0032] In one embodiment of the MEMS microphone, it is provided that at least one spring is helical.

[0033] This results in the following technical advantages, for example: the tension in the layer can be compensated by the rotational movement of the membrane. The membrane properties are therefore no longer dependent on the layer tension of the membrane. In addition, the suspension of the membrane can be designed to be particularly soft.

[0034] In one embodiment, the MEMS microphone includes a stop structure for the membrane in at least one of the two deflection directions of the membrane.

[0035] This results in the technical advantage that in the event of an overload, the membrane can be effectively prevented from striking the lever element.

[0036] The expression "at least one" means "one or more".

[0037] This means that the expression “in at least one of the two deflection directions of the membrane” means the following: in one of the two deflection directions of the membrane or in both deflection directions.

[0038] The deflection direction, which may also be referred to as the first deflection direction, points in the direction of the carrier. The other deflection direction, which may also be referred to as the second deflection direction, points away from the carrier.

[0039] In one embodiment of the MEMS microphone, it is provided that the stop structure has a carrier region of the carrier formed below the at least one spring as a stop for the membrane in a deflection direction toward the carrier.

[0040] This results in, for example, the following technical advantage: the stop structure can be formed effectively.

[0041] In one embodiment of the MEMS microphone, it is provided that the stop structure has a cover formed over the at least one spring as a stop for the membrane in a deflection direction away from the carrier.

[0042] This results in the following technical advantage: the stop structure can be formed effectively.

[0043] In one embodiment, the MEMS microphone comprises a carrier, in particular a substrate, on which the membrane, the signal transducer element and the lever element are arranged, wherein the membrane is directly attached to the carrier.

[0044] This results in the technical advantage that the film is effectively attached to the carrier.

[0045] The signal conversion element may be, for example, a signal conversion element according to DE 10 2021 206 005. Accordingly, the signal conversion element may be a transducer element which generates a capacitive signal in a hermetically closed region, wherein a pressure lower than the external pressure is enclosed in this region.

[0046] In the sense of this specification, the signal conversion element converts the tilting motion transmitted by the lever element into a signal, such as a voltage signal. The signal conversion element is, for example, configured to convert the tilting motion transmitted by the lever element into a signal, such as a voltage signal. The signal is, for example, an electrical signal. For example, the signal conversion element includes two opposing electrodes, which form a capacitor, wherein one of the two electrodes is a fixed electrode and the other of the two electrodes is a movable electrode, to which the tilting motion is transmitted by the lever element. The voltage applied to the capacitor is particularly related to the distance between the two electrodes. Since the distance is changed by the transmitted tilting motion, the applied voltage is also changed, so that the deflection of the membrane can be inferred by voltage measurement. The applied voltage is thus related to the deflection of the membrane.

[0047] The signal conversion element comprises, for example, two stationary counter-electrodes: a first counter-electrode and a second counter-electrode, which are arranged on a carrier. These stationary counter-electrodes can also be referred to as stator electrodes.

[0048] Above the two counter-electrodes, for example, a movable electrode of the signal conversion element is arranged, which electrode can perform a tilting movement and whose movement can be determined, for example, by measuring the capacitance with respect to a corresponding one of the two counter-electrodes. The movable electrode can also be referred to as an actuator electrode. The lever element is, for example, configured to generate a tilting movement when the membrane is deflected and to transmit the generated tilting movement to the movable electrode. Thus, the deflection of the membrane is transmitted to the movable electrode of the signal conversion element by means of the lever element.

[0049] The MEMS microphone comprises, for example, a sealing layer which seals or seals the two counter electrodes and the movable electrode. The sealing layer is thus responsible in particular for sealing the structure consisting of the counter electrode and the movable electrode, for example to seal off a vacuum in this area, for example to reduce damping.

[0050] A carrier in the sense of the present description is, for example, a substrate.

[0051] The membrane can be formed, for example, as a MEMS functional layer.

[0052] Generally speaking, elements of a MEMS microphone, such as a membrane, a lever element, a counter electrode, a movable electrode and / or a closing layer, can each be formed as a MEMS functional layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The present invention will be explained in more detail below with the aid of preferred embodiments. In the accompanying drawings:

[0054] Figure 1 showing a first MEMS microphone in a cross-sectional view,

[0055] Figure 2showing a second MEMS microphone in cross-sectional view,

[0056] Figure 3 A third MEMS microphone is shown in cross-sectional view,

[0057] Figure 4 A fourth MEMS microphone is shown in cross-sectional view and

[0058] Figure 5 The fourth MEMS microphone is shown in a top view. DETAILED DESCRIPTION

[0059] The same reference numerals may be used below for the same features.

[0060] Figure 1 A first MEMS microphone 101 is shown in a cross-sectional view.

[0061] The first MEMS microphone 101 includes a membrane 103 for receiving sound pressure. The membrane 103 is attached to a substrate 105 and spans a cavity 107 in the substrate 105.

[0062] The first MEMS microphone 101 comprises a lever element 109 coupled to the membrane 103. The lever element 109 is further coupled to a signal transducer element 111 of the first MEMS microphone 101. The lever element 109 is configured to generate a tilting movement when the membrane 103 is deflected and to transmit the generated tilting movement to the signal transducer element 111.

[0063] In other words, the lever element 109 is coupled to the membrane 103 and, when the membrane 103 is deflected, generates a tilting movement which is transmitted to the signal conversion element 111 .

[0064] Since the membrane 103 does not have to move relative to one or two fixed counter electrodes, on the one hand the acoustic movement of the membrane 103 is virtually undamped and on the other hand a very good signal quality can be ensured.

[0065] In the first MEMS microphone 101, the lever element 109 is attached to the membrane 103 eccentrically with respect to the membrane 103. The attachment point 113 of the lever element 109 on the membrane 103 is selected such that the tilting of the membrane 103 coincides with the tilting movement of the lever element 109 fixed to the signal conversion element 111. Thus, a particularly sensitive MEMS microphone can be provided in which no additional distortion is caused when the membrane 103 is deflected, either in the signal conversion element 111, in the lever element 109 or in the membrane 103.

[0066] The signal conversion element 111 comprises two stationary counter-electrodes: a first counter-electrode 115 and a second counter-electrode 117, which are arranged on the substrate 105. The stationary counter-electrodes 115, 117 may also be referred to as stator electrodes.

[0067] A movable electrode 119 of the signal conversion element 111 is arranged above the two counter-electrodes 115, 117, which can perform a tilting movement and whose movement can be determined, for example, by measuring the capacitance with a corresponding one of the two counter-electrodes 115, 117. The movable electrode 119 can also be referred to as an actuator electrode.

[0068] MEMS microphone 101 comprises a sealing layer 121 which seals or seals the two counter electrodes 115, 117 and movable electrode 119. Sealing layer 121 thus ensures sealing of the structure consisting of counter electrodes 115, 117 and movable electrode 119, for example to seal off a vacuum in this region, for example to reduce damping.

[0069] Figure 2 The second MEMS microphone 201 is shown in a cross-sectional view.

[0070] In the second MEMS microphone 201, the lever element 109 is attached in the center of the membrane in order to transmit the greatest possible deflection to the signal conversion element 111. The membrane 103 has a recess 203 in the membrane center, which can bring about compensation of different tilting movements between the lever element 109 and the membrane 103.

[0071] Figure 3 A third MEMS microphone 301 is shown in a cross-sectional view. When using a connecting element 303, a distance is created between the membrane 103 and the lever element 109 in order to prevent the membrane 103 from hitting the lever element 109 in the case of large deflections of the membrane 103. The connecting element 303 can be particularly thin and high in order to be able to compensate for different tilting movements between the lever element 109 and the membrane 103.

[0072] The use of a particularly thin membrane which is nevertheless subjected to tensile stress is particularly advantageous. Thus, a large area can be spanned and the natural frequency of the membrane can be set by the tensile stress, wherein the low mass of the membrane results in a high sensitivity.

[0073] For applications where layers with tensile stress cannot be provided or for arrangements in which these layers are also used to construct signal conversion elements, Figure 4 and 5 An arrangement such as that shown in is particularly advantageous.

[0074] Figure 4 A fourth MEMS microphone 401 is shown in a cross-sectional view.

[0075] At the edge of the membrane 103, the membrane 103 is suspended from the substrate 105 by a three-part spring 403. The first spring part 405 refers to the part of the spring 403 that is coupled to the substrate 105. The second spring part 407 refers essentially to the middle part of the spring 403. The third part 409 refers to the part of the spring that is coupled to the membrane 103.

[0076] The spring 403 or the three spring parts 405, 407, 409 have a spiral shape. Therefore, the stresses in the layer can be compensated by the rotational movement of the membrane 103. The membrane properties are therefore no longer dependent on the layer stress of the membrane 103. In addition, the suspension of the membrane 103 can also be configured to be particularly soft.

[0077] For example, multiple layers are used or utilized to set small distances between substrate 105 and spring 403 and between spring 403 and membrane 103 to keep the acoustic leakage paths as small as possible.

[0078] A small distance is, for example, a distance between 3 μm and 0.3 μm, wherein 3 μm and 0.3 μm are also included. Therefore, a distance between 3 μm and 0.3 μm, wherein 3 μm and 0.3 μm are also included, can be defined as a small distance, for example.

[0079] Furthermore, for example, a base region 411 and a covering formed by a further layer 413 can be provided above and below the spring, wherein the further layer 413 can be, for example, the same layer that is also used to form the lever element 109. Thus, the acoustic leakage path can be further reduced in an advantageous manner and at the same time, a stop structure can be provided in an advantageous manner for the membrane in two deflection directions, one towards the base 105 and one away from the base 105. Furthermore, in an advantageous manner, the membrane 103 can also be prevented from hitting the lever element 109 in the event of an overload.

[0080] Figure 5 A fourth MEMS microphone 401 is shown in a top view.

Claims

1. MEMS microphone (101, 201, 301, 401), including: a membrane (103) for receiving sound pressure, A signal conversion element (111) and a lever element (109) coupled to the membrane (103) and the signal conversion element (111), The lever element (109) is provided to generate a tilting movement when the membrane (103) is deflected and to transmit the generated tilting movement to the signal conversion element (111).

2. The MEMS microphone (101, 201, 301, 401) according to claim 1, wherein: The lever element (109) is attached to the membrane (103) eccentrically or centrally relative to the membrane (103).

3. The MEMS microphone (101, 201, 301, 401) according to claim 2, wherein: In the case of a central attachment, a recess (203) is provided in the membrane (103) in order to compensate for different tilting movements between the lever element (109) and the membrane (103).

4. The MEMS microphone (101, 201, 301, 401) according to any one of the preceding claims, wherein: The lever element (109) is attached to the membrane (103) at an attachment point (113) in such a way that the tilting of the membrane (103) corresponds essentially to the tilting movement of the lever element (109).

5. The MEMS microphone (101, 201, 301, 401) according to any one of the preceding claims, wherein: The lever element (109) is coupled to the membrane (103) at a distance from the membrane (103) to prevent the membrane (103) from colliding with the lever element (109).

6. The MEMS microphone (101, 201, 301, 401) according to any one of the preceding claims, wherein: The lever element (109) is connected to the membrane (103) via a mechanical connecting element (303), which has a height of at least three times the membrane thickness in a partial area and the area of ​​the membrane (103) covered by the connecting element is less than 25% of the area of ​​the membrane (103) to compensate for the different tilting movements between the lever element (109) and the membrane (103).

7. The MEMS microphone (101, 201, 301, 401) according to any of the preceding claims, comprising a carrier, in particular a substrate (105), on which the membrane (103), the signal conversion element (111) and the lever element (109) are arranged, wherein: The membrane (103) is at least partially attached to, in particular suspended from, the carrier via at least one spring (105).

8. The MEMS microphone (101, 201, 301, 401) according to claim 7, wherein: The at least one spring (105) is helical.

9. The MEMS microphone (101, 201, 301, 401) according to claim 7 or 8, comprising a stop structure (411; 413) for stopping the membrane (103) in at least one of the two deflection directions of the membrane (103).

10. The MEMS microphone (101, 201, 301, 401) according to claim 9, wherein: The stop structure (411; 413) has a carrier region of the carrier formed below the at least one spring (105) as a stop for the membrane (103) in a deflection direction toward the carrier.

11. The MEMS microphone (101, 201, 301, 401) according to claim 9 or 10, wherein: The stop structure (411; 413) has a cover formed over the at least one spring (105) as a stop for the membrane (103) in a deflection direction away from the carrier.

12. The MEMS microphone (101, 201, 301, 401) according to any one of claims 1 to 6, comprising a carrier, in particular a substrate (105), on which the membrane (103), the signal conversion element (111) and the lever element (109) are arranged, wherein: The membrane (103) is directly attached to the carrier.

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