MEMS Element For Movement Of A Mass Element Of A Sound Transducer For Generating And / Or Receiving A Sound Signal, And Sound Transducer With Such A MEMS Element
By designing the cavity structure and high rigidity connecting elements in the substrate of the MEMS element, the problems of depth stop and resonance frequency deviation of traditional MEMS elements are solved, the stability and motion transmission efficiency of the actuator element are improved, and the cost is reduced .
Patent Information
- Application Number
- CN202380043473.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-06-01
- Filing Date
- 2023-05-15
- Publication Date
- 2025-01-10
AI Technical Summary
Traditional MEMS elements have deviations in depth stop accuracy and resonance frequency, resulting in the actuator elements being easily damaged and the resonance frequency is inaccurate.
By designing the cavity structure in the substrate of the MEMS element, a more accurate depth stop and highly rigid connecting element is formed, ensuring that the movement energy of the actuator element is accurately transmitted to the mass element, and the height and transverse dimensions of the cavity are adjusted. To optimize the geometry and resonance frequency of the actuator element.
Improves the adjustment accuracy and breaking strength of the actuator elements, reduces the risk of damage, and achieves more precise resonance frequency adjustment and motion transmission, reducing the cost of the sound transducer.
Smart Images
Figure CN119301967A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a MEMS element for movement of a mass element of a sound transducer to generate and / or receive sound signals.
[0002] The idea is to put the mass element of the sound transducer into a lifting motion state by one or more MEMS elements, thereby emitting sound or being deflected in the opposite direction by the sound, and to detect the sound signal by the MEMS element. Background Art
[0003] A problem with conventional MEMS components is that, due to the configuration of the MEMS component and the associated manufacturing process, the depth stop often has a corresponding deviation from the target specification, so that the precision for adjusting the depth stop is insufficient. As a result, the fracture limit of the actuator element is exceeded and the MEMS component is damaged.
[0004] Furthermore, in conventional MEMS components, the configuration of the actuator element, which has a direct influence on the resonance frequency, is produced by a groove process, and the size of the groove process may be inaccurate due to tilting and expansion depending on the process. Therefore, according to the prior art, MEMS components may have large deviations from each other in their resonance frequencies. Summary of the invention
[0005] These problems are to be solved by the present invention.
[0006] The present invention relates to a MEMS element for use in the movement of a mass element of a sound transducer to generate and / or receive sound signals.
[0007] One aspect of the present invention is that the MEMS element is manufactured from a substrate, wherein the MEMS element has an actuator element, which has at least one piezoelectric element mounted on the actuator element for movement of the actuator element in a vertical direction relative to a main extension plane of the MEMS element, wherein the geometry of the actuator element is defined by a cavity of the substrate, wherein the MEMS element has a connecting element arranged on the actuator element for connecting the actuator element to a mass element of the sound transducer and transmitting the movement of the actuator element to the mass element, wherein the connecting element has a higher rigidity than the actuator element, and wherein the cavity is configured in the substrate so that the substrate itself forms a depth stop for the actuator element in the vertical direction.
[0008] Advantageously, the geometry of the actuator element and the configuration of the depth stop by means of the cavity can be realized more precisely than in the prior art, which in turn leads to a more precise adjustment of the resonance frequency of the push rod element and reduces the risk of the actuator element exceeding the breaking limit.
[0009] A further advantage is that the actuator element can be moved in a simple manner by adjusting the rigidity, while at the same time, due to the increased rigidity of the connecting element, the movement can also be transmitted to the mass element of the sound transducer in a manner that is as loss-free as possible.
[0010] An acoustic transducer is understood to be a system which converts non-mechanical energy (usually electrical energy) into mechanical energy in a suitable manner by means of a piezoelectric element, thereby generating an acoustic signal. This conversion effect can usually be reversed in the same way, i.e. the mechanical energy of the received acoustic signal is converted into electrical energy, wherein the generated electrical signal can be evaluated accordingly. For example, an acoustic transducer can be designed as an ultrasonic transducer and receive or emit corresponding ultrasonic signals.
[0011] For example, an acoustic transducer can be used in a microphone or speaker, but can also be used in an ultrasonic sensor system.
[0012] The emitted sound signal is generated by a mass element of the sound transducer, which is set in motion by a MEMS element, or by a received sound signal, which can be detected by the MEMS element. For example, the mass element can be designed as a diaphragm or piston-like.
[0013] In particular, a plurality of sound transducers may constitute a sound transducer array.
[0014] A “MEMS component” is understood to be a micro-electromechanical system which combines or integrates electronic and mechanical components in a very small space.
[0015] The MEMS element has an actuator element, which can be designed, for example, in the form of a cantilever or a diaphragm and can be set in motion by a piezoelectric element or can also transmit a movement to the piezoelectric element for evaluation.
[0016] Here, the actuator element is mounted on a suspension element which is more rigid than the actuator element and is, for example, the remaining substrate of the MEMS element. Furthermore, a connecting element is arranged on the actuator element, which serves to connect the actuator element to the mass element and to enable a movement in one direction or in the other direction, respectively.
[0017] The connecting element can here comprise individual or all layers which are also present in the actuator element and can accordingly be designed as a continuation of the actuator element or also project beyond the actuator element at least in a vertical direction relative to a main extension plane of the actuator element.
[0018] For example, the piezoelectric element can be designed as a piezoelectric layer.
[0019] For example, a correspondingly pretreated silicon wafer can be used as a substrate, which is then processed accordingly to obtain the desired configuration of the MEMS element with suspension elements, actuator elements and connecting elements. The substrate can also be a combination of wafers, which are connected, for example, by wafer bonds and can include layer systems and structuring parts accordingly. For example, a cavity SOI wafer can also be considered as a substrate.
[0020] In engineering mechanics, "rigidity" is understood to be a parameter that describes the relationship between the load acting on an object and its elastic deformation. The rigidity of an object depends, among other things, on its material and its geometry.
[0021] A “cavity” is understood to be a hollow space in a substrate.
[0022] In particular, the cavity in the substrate is parallel here to a main extension plane below the actuator element.
[0023] Furthermore, a "depth stop" is to be understood as a stop for the actuator element, which is used to stop the movement of the actuator element at a certain point. In particular, the actuator element is configured as a region of the upper side of the cavity, wherein the depth stop is a region of the lower side of the cavity.
[0024] One embodiment of the invention provides that the depth stop is defined by the height of the cavity.
[0025] The advantage here is that the height of the cavity in the substrate can be adjusted very precisely depending on the process technology.
[0026] The “height of the cavity” is understood to mean the distance between the bottom and the top of the cavity when the MEMS element is not loaded, ie the top and the bottom of the cavity extend substantially parallel to each other.
[0027] One embodiment of the invention provides that the rigidity of the actuator element and / or the connecting element is adjusted according to the material and / or thickness and / or structuring of the corresponding element. Advantageously, this simply enables the rigidity of the corresponding element to be adjusted as desired.
[0028] “Material” is to be understood as meaning the chemical composition of the respective element, which in turn has an influence on its rigidity.
[0029] "Structured" is understood to mean the configuration of an element, which can, for example, have corresponding recesses or openings in order to change its rigidity. For example, the actuator element can be configured in a spoke-like manner in order to maintain a low rigidity, while the suspension element and the connecting element do not have corresponding recesses in order to maintain a high rigidity in contrast.
[0030] "Thickness" is to be understood as the extension of the element in the vertical direction relative to the main extension plane of the MEMS element. In theory, this also falls under the term "structuring", but due to the special significance of the thickness for the rigidity properties of the element, it is explicitly emphasized again here.
[0031] A further embodiment of the invention provides that the connecting element is arranged laterally on the actuator element and forms a head, wherein the cavity is opened so that the connecting element is separated from the rest of the substrate.
[0032] Advantageously, the geometry of the actuator element and the resonance frequency are defined by the lateral dimensions of the cavity, which can usually be adjusted very precisely depending on the method selected for realizing the cavity. The height d of the depth stop can in turn be defined by the height of the cavity, which can usually also be adjusted very precisely depending on the method selected for realizing the cavity. In addition, it is particularly easy to produce MEMS elements from substrates with cavities, whereby the costs of MEMS elements can be kept low.
[0033] In this case, a corresponding configuration of the actuator element can form, for example, a so-called cantilever, which can be understood to be a movable arm.
[0034] In particular, the cavity is open in one direction or on one side, and particularly preferably open downwards, so that the connecting element is only still connected to the actuator element and no longer to the rest of the substrate as a suspension element.
[0035] In this case, the connecting element is arranged in the main extension plane at one end of the actuator element, for example on the right side, while the actuator element is in turn connected to the suspension element at its other end, ie on the left side.
[0036] In particular, a “terminal” may be understood to mean a so-called stub.
[0037] According to one embodiment of the invention, at least two piezoelectric elements are mounted on the actuator element, which piezoelectric elements can be controlled in a phase-shifted manner.
[0038] The advantage here is that an S-shaped deflection can be achieved, wherein the stroke and the breaking strength of the actuator element are increased in turn.
[0039] For example, by actuating the phase shift, it can be achieved that one of the piezoelectric elements bends to the left while the other piezoelectric element bends to the right, so that a corresponding deformation of the actuator element can be achieved depending on the position of the piezoelectric elements on the actuator element.
[0040] According to a further embodiment of the invention, the cavity has regions with different heights, wherein in particular the region of the cavity with the smallest height serves as a depth stop.
[0041] It is advantageous here that the properties of the elements adjoining the cavity can be influenced accordingly by the different heights. For example, the rigidity of the actuator element can be influenced thereby.
[0042] According to a further embodiment of the invention, the actuator element and the connecting element are arranged concentrically in a main extension plane of the MEMS element, wherein the connecting element is arranged centrally, wherein the cavity extends below the actuator element and the connecting element parallel to the main extension plane.
[0043] Advantageously, a further embodiment of the actuator element and the connecting element is achieved which in particular allows a more uniform transmission of the movement of the actuator element to the mass element of the sound transducer, since the connecting element is moved accordingly from a plurality of sides by the actuator element.
[0044] For example, the actuator element can be embodied in a diaphragm-shaped manner and can be arranged accordingly around the connecting element, for example in a circular shape when viewed from above the MEMS element, although other geometries are also possible.
[0045] According to a further embodiment of the invention, the cavity has a lower height in the region of the connecting element than in the region of the actuator element, so that an indirect depth stop for the actuator element is formed by the connecting element.
[0046] It is advantageous here that in the region of the connecting element the depth stop can be adjusted better due to the lower height of the cavity, while in the region of the actuator element an improved damping property of the actuator element can be achieved due to the relatively greater height.
[0047] The invention further relates to a sound transducer having a MEMS element according to the invention, wherein an actuator element of the MEMS element is connected to a mass element of the sound transducer via a connecting element of the MEMS element. BRIEF DESCRIPTION OF THE DRAWINGS
[0048] Figure 1 A side section through a sound transducer with a first specific embodiment of a MEMS element configured according to the invention is shown.
[0049] Figure 2 A side section through a sound transducer with a second specific embodiment of a MEMS element configured according to the invention is shown.
[0050] FIG. 3 shows method steps for producing a MEMS component according to the prior art.
[0051] Figure 4 shows the method for manufacturing according to Figure 1 Method steps for a MEMS component according to a first embodiment. DETAILED DESCRIPTION
[0052] Figure 1 A lateral section through a sound transducer with a first embodiment of a MEMS element configured according to the invention is shown. A sound transducer 101 is shown for generating and / or receiving a sound signal 120. To this end, the sound transducer 101 has a mass element 110 and a MEMS element 11 for the movement of the mass element 110 of the sound transducer 101. Here, the MEMS element 11 is made of a substrate 21.
[0053] The MEMS element 11 has an actuator element 31, which has two piezoelectric elements 35 mounted on the actuator element 35 for moving the actuator element 31 in a vertical direction relative to the main extension plane 15 of the MEMS element 11. In principle, a single piezoelectric element 35 is also conceivable here. In addition, the deflection of the mass element 110 caused by the reception of the sound signal 120 by the actuator element 31 and the piezoelectric element 35 mounted thereon can naturally also be detected with the aid of the MEMS element 11. The piezoelectric element 35 can be mounted on the actuator element 31 as a corresponding piezoelectric layer and can be controlled or read out by an electronic device (not shown). In particular, the piezoelectric element 35 can be controlled in a phase-shifted manner here to achieve an S-shaped deflection of the actuator element 31.
[0054] In addition, the MEMS element 11 has a connection element 51, which is in particular directly connected to the actuator element 31, for connecting the actuator element 31 to the mass element 110 of the sound transducer 101 and transmitting the movement of the actuator element 31 to the mass element 110, wherein the connection element 51 has a higher rigidity than the actuator element 31. The connection element 51 can be connected to the mass element 110 by a connection device 111, for example, the connection device can be configured as an adhesive. The greater rigidity of the connection element 51 relative to the rigidity of the actuator element 31 is achieved here by a greater thickness of the connection element 51 relative to the thickness of the actuator element 31, wherein the thickness refers to the dimension of the respective element 31, 51 in the vertical direction.
[0055] The actuator element 31 is also connected to a suspension element 71 which forms the rest of the substrate 21 and has a greater rigidity than the actuator element 31 , which in turn is achieved by an increased thickness.
[0056] Furthermore, the geometry of the actuator element 31 is defined by the cavity 41 of the substrate 21, wherein the cavity 41 is configured in the substrate 21 such that the substrate 21 itself forms a depth stop 61 for the actuator element 31 in the vertical direction relative to the main extension plane 15. The depth stop 61 is defined by the height h of the cavity 41.
[0057] In particular, the connecting element 51 is arranged laterally on the actuator element 31 and forms an end, wherein the cavity 41 is opened, separating the connecting element 51 from the rest of the substrate 21, so that the actuator element 31 and the connecting element 51 are movable accordingly. By a corresponding configuration, the actuator element 31 and the connecting element 51 can move around the suspension element 71 as a support point, as indicated by the corresponding double arrow. Alternatively, the depth stop can also be defined by the width of the opening between the connecting element 51 and the rest of the substrate 21.
[0058] The MEMS element 11 can also be connected to the carrier element 130 via a connecting element 131 , which is in turn configured as an adhesive, for example. The carrier element is configured as a PCB, for example.
[0059] Figure 2 A side section through a sound transducer with a second specific embodiment of a MEMS element configured according to the invention is shown.
[0060] A sound transducer 102 is shown, which is connected to Figure 1 Like the sound transducer 101 in the embodiment, the sound transducer 102 is used to generate and / or receive a sound signal 120. To this end, the sound transducer 102 again has a mass element 110 and a MEMS element 12 for the movement of the mass element 110 of the sound transducer 102. The MEMS element 12 is made of a substrate 22.
[0061] Furthermore, the MEMS element 12 has an actuator element 32, which has two piezoelectric elements 35 mounted on the actuator element 32 for movement of the actuator element 32 in a vertical direction relative to the main extension plane 15 of the MEMS element 12 (as indicated by the double arrow). Alternatively, it is also conceivable to use a single annular piezoelectric element instead of the two piezoelectric elements 35. Furthermore, the MEMS element 12 can naturally also be used to detect the deflection of the mass element 110 due to the reception of the sound signal 120 by the actuator element 32 and the piezoelectric element 35 mounted there. The piezoelectric element 35 can in turn be mounted on the actuator element 32 as a corresponding piezoelectric layer and can be controlled or read out by an electronic device (not shown). In particular, the piezoelectric element 35 can be controlled in a phase-shifted manner to achieve an S-shaped deflection of the actuator element 32.
[0062] Furthermore, the MEMS element 12 has a connecting element 52, which is in particular directly connected to the actuator element 32, for connecting the actuator element 32 to the mass element 110 of the sound transducer 102 and transmitting the movement of the actuator element 32 to the mass element 110, wherein the connecting element 52 has a higher rigidity than the actuator element 32. The connecting element 52 can be connected to the mass element 110 via a connecting device 111, which is configured as an adhesive or the like, for example. The higher rigidity of the connecting element 52 relative to the rigidity of the actuator element 32 can be achieved by corresponding structuring of the actuator element 32, because the actuator element is configured in a spoke-like manner in a top view (not shown) and has corresponding recesses or through-holes, while the connecting element 52 does not have such recesses or through-holes.
[0063] The actuator element 32 is connected radially outwardly to a surrounding suspension element 72 , which forms the rest of the substrate 22 and also has a higher rigidity than the actuator element 32 , which in turn is achieved by the absence of a corresponding recess.
[0064] Furthermore, the geometry of the actuator element 32 is also influenced by the cavity 42 of the substrate 22 and can be defined in particular thereby, wherein the cavity 42 is configured in the substrate 22 such that the substrate 22 itself forms a depth stop 62 for the connecting element 52 and thus indirectly for the actuator element 32 in a vertical direction relative to the main extension plane 15. The depth stop 62 is defined by the height h of the cavity 42. In particular, the cavity 42 has regions with correspondingly different heights h, wherein in particular the region of the cavity 42 with the lowest height h serves as the depth stop 62. Accordingly, the cavity 42 has a lower height h in the region of the connecting element 52 than in the region of the actuator element 32, so that an indirect depth stop 62 for the actuator element 32 is formed by the connecting element 52.
[0065] The MEMS element 12 can in turn be connected to a carrier element 130 via a connection element 131 , which is configured, for example, as an adhesive, and the carrier element is configured, for example, as a PCB.
[0066] FIG. 3 shows method steps for manufacturing a MEMS element according to the prior art.
[0067] Thus, in method step a), a substrate 220 is provided which is in the form of an SOI wafer.
[0068] In the subsequent method step b), the piezoelectric element 35 can be applied as a piezoelectric layer.
[0069] In method step c), a notching process is then carried out in order to produce the actuator element 230 and the connecting element 250 .
[0070] Subsequently, in method step d), a depth stop 260 is produced for the actuator element 230 on one side and a suspension 270 is produced on the other side by bonding the product of method step c) to the carrier element 130 designed as a wafer by means of wafer bonding 132, thereby obtaining a MEMS element designed as a cantilever, similar to Figure 1 MEMS element 11. However, in the prior art, the device has to handle and separate very fragile structures on the wafer 130 during the manufacturing process, which causes difficulties. In addition, the vertical spacing d of the depth stop 260 can only be adjusted in an insufficiently precise manner by means of the wafer bond 132. In addition, the geometry and therefore the resonance frequency of the actuator element 230 are defined according to method step c) by a groove process, and the dimensions of the groove process may be inaccurate due to tilting and expansion depending on the process.
[0071] Figure 4 shows a method for making a Figure 1 Method steps for a MEMS component according to a first embodiment.
[0072] In method step a), a substrate 21 with cavities 41 is provided, wherein this is a cavity SOI wafer in this case. Alternatively, a substrate with corresponding cavities can also be produced by means of porous silicon technology or by means of a groove process for cavities.
[0073] In method step b), the piezoelectric element 35 is deposited and structured into a piezoelectric layer. This may include further layers (not shown), such as electrode layers, barrier layers, etc.
[0074] In method step c), the cavity 41 is opened downward on one side, thereby forming an opening 45 which separates the actuator element 31 and the connecting element 51 from the rest of the substrate 21 and accordingly enables them to move. This results in a MEMS element which is connected to the substrate 21 and to the connecting element 51. Figure 1 The MEMS elements 11 of the embodiment of the present invention differ only in the number of piezoelectric elements 35. The manufacturing process can also include further steps, such as placing markings or separating the elements.
Claims
1. A MEMS element (11, 12) for moving a mass element (110) of a sound transducer (101, 102) to generate and / or receive a sound signal (120), wherein: The MEMS element is made of a substrate (21, 22), wherein the MEMS element (11, 12) has an actuator element (31, 32), wherein the actuator element has at least one piezoelectric element (35) mounted on the actuator element (31, 32) for movement of the actuator element (31, 32) in a vertical direction relative to a main extension plane (15) of the MEMS element (11, 12), wherein the geometry of the actuator element (31, 32) is influenced by a cavity (41, 42) of the substrate (21), wherein the MEMS element (11, 12) has a cavity (41, 42) arranged on the actuator element A connecting element (51, 52) on the substrate (21, 22) is used to connect the actuator element (31, 32) to the mass element (110) of the sound transducer (101, 102) and transmit the movement of the actuator element (31, 32) to the mass element (110), wherein the connecting element (51, 52) has a higher rigidity than the actuator element (31, 32), and wherein the cavity (41, 42) is configured in the substrate (21, 22) so that the substrate (21, 22) itself forms a depth stop (61, 62) for the actuator element (31, 32) in the vertical direction.
2. The MEMS element (10, 11) according to claim 1, characterized in that The depth stop (61, 62) is defined by the height (h) of the cavity (41, 42).
3. The MEMS element (11, 12) according to any one of the preceding claims, characterized in that The rigidity of the actuator element (31, 32) and / or the connecting element (51, 52) is adjusted depending on the material and / or thickness and / or structuring of the corresponding element (31, 32, 51, 52).
4. The MEMS element (11) according to any one of the preceding claims, characterized in that The connecting element (51) is arranged laterally on the actuator element (31) and forms a termination, wherein the cavity (41) is opened so that the connecting element (51) is separated from the rest of the substrate (21).
5. The MEMS element (11, 12) according to any one of the preceding claims, characterized in that At least two piezoelectric elements (35) are mounted on the actuator elements (31, 32), which piezoelectric elements can be controlled in a phase-shifted manner.
6. The MEMS element (11, 12) according to any one of the preceding claims, characterized in that The cavity (41, 42) has regions with different heights (h), wherein in particular the region of the cavity (41, 42) with the smallest height (h) serves as a depth stop (61, 62).
7. The MEMS element (12) according to any one of the preceding claims, characterized in that The actuator element (42) and the connecting element (52) are arranged concentrically in the main extension plane (15) of the MEMS element (12), wherein the connecting element (52) is arranged centrally, and wherein the cavity (42) extends below the actuator element (42) and the connecting element (52) parallel to the main extension plane (15).
8. The MEMS element (12) according to claim 7, characterized in that The cavity (42) has a smaller height (h) in the region of the connecting element (52) than in the region of the actuator element (32), so that an indirect depth stop (62) for the actuator element (32) is formed by the connecting element (52).
9. A sound transducer (101, 102) having a MEMS element (11, 12) according to any one of the preceding claims, wherein: The actuator element (31, 32) of the MEMS element (11, 12) is connected to the mass element (110) of the sound transducer (101, 102) via the connecting element (51, 52) of the MEMS element (11, 12).