MEMS component

Abstract

The invention relates to a MEMS component for sensing fluid mass flows, comprising: a substrate having a recess, a beam structure at least partially spanning the substrate recess and being anchored to the substrate on at least one side, wherein the beam structure has a first beam plane having a plurality of first beams and a first electrode layer and has a second beam plane spaced apart from the first beam plane and having a plurality of second beams and a second electrode layer and has a plurality of connecting elements between the first and the second beam plane coupling the first and the second beam plane to each other in terms of movement, wherein the beam structure is designed in such a way that a distance between the first and the second beams changes when an external force acts perpendicularly on the main extension plane of the beam structure.

Description

[0001] Description

[0002] title

[0003] MEMS component

[0004] The invention relates to a MEMS component.

[0005] State of the art

[0006] The patent EP 2 664 058 B1 discloses a micromechanical component.

[0007] The patent EP 3 568 595 B1 discloses a micromechanical device.

[0008] The published patent application EP 3 796 671 A1 discloses a piezoelectric MEMS microphone.

[0009] The published patent application CN 107872760 A discloses a MEMS microphone.

[0010] The published patent application CN 114520947 A discloses a microphone arrangement.

[0011] Capacitive MEMS microphones are particularly efficient in terms of signal-to-noise ratio, power consumption, and processability. This has led to a widespread replacement of electret microphones by MEMS microphones.

[0012] The development of MEMS microphones with dual diaphragms has once again led to a significant improvement in the signal-to-noise ratio. This concept almost completely eliminates the fluidic, noisy damping between the rigid backplate and the movable dynamic pressure diaphragm. This is achieved by mounting the backplate in a vacuum region between two coupled diaphragms. Two such dual diaphragm microphones are disclosed in US Pat. Nos. 9,181,080 and 9,986,344. The disadvantage of this arrangement is the high mechanical rigidity of the dual diaphragm structure, which limits its deflectability and thus its sensitivity.

[0013] Disclosure of the invention

[0014] The object underlying the invention is to provide a MEMS component.

[0015] This object is achieved by means of the subject matter according to the independent claim. Advantageous embodiments of the invention are the subject matter of the respective dependent subclaims.

[0016] According to a first aspect, a MEMS component for sensing fluid mass flows is provided, comprising: a substrate having a recess, a beam structure which at least partially spans the substrate recess and is anchored to the substrate on at least one side, wherein the beam structure has a first beam plane having a plurality of first beams and a first electrode layer, and a second beam plane spaced therefrom having a plurality of second beams and a second electrode layer, and a plurality of connecting elements between the first and the second beam plane which couple the first and the second beam plane to one another in their movement, wherein the beam structure is configured such that a distance between the first and second beams changes when an external force acts perpendicularly on its main extension plane.

[0017] Directional mass flow sensors and microphones rely primarily on the fluid flow field or sound velocity, due to dynamic pressure, causing a relative deflection of the electrodes. To achieve this, the dynamic pressure element should have a suitable, preferably low, flexural rigidity. Cantilever beams represent a good compromise between low flexural rigidity and high robustness. To build microphones that are as small as possible with a high signal-to-noise ratio and high sensitivity, a high capacitance density is desirable. The arrangement of electrodes along a periphery, as described in the prior art described above, is only partially suitable for this purpose.

[0018] According to the concept described here, at least two beam planes arranged one above the other with integrated electrodes are used to generate a measurement signal across the entire transducer surface and not just in the peripheral region. The two beam planes are connected to one another via a plurality of connecting elements at suitable points so that, on the one hand, their movement is coupled to one another. On the other hand, their deformation is independent of one another, resulting in a relative change in distance that can be capacitively read. A vertical spacing of the beam planes or electrodes is achieved in particular via a sacrificial layer deposition, which can be achieved much more thinly and precisely than lateral distances defined using lithographic methods. The MEMS component can therefore be manufactured with greater sensitivity and smaller variance.

[0019] The concept described here results in a high capacity density and a great deal of design freedom.

[0020] Furthermore, the concept described here can advantageously provide a MEMS component which, compared to the above-mentioned prior art, enables a small size with the same performance or a higher performance with the same size.

[0021] The abbreviation "MEMS" stands for micro-electro-mechanical system.

[0022] The beams can, for example, be formed from the electrode layers themselves. The electrode layers are, for example, arranged or applied to the beam. In one embodiment of the MEMS component, one of the beam planes has a greater thickness and / or is constructed differently from the other beam plane.

[0023] This provides the technical advantage, for example, that one of the planes can be designed to be stiffer than the other. This allows for targeted, advantageous deformation under load during operation, for example, to increase robustness against overload or to enhance sensitivity.

[0024] The fact that the beam levels can be constructed differently means in particular that one of the beam levels has a different layer structure than the other of the beam levels.

[0025] In one embodiment of the MEMS component, it is provided that the beam construction has a third beam plane spaced apart from the first and second beam planes, comprising a plurality of third beams, with a third electrode layer, and a plurality of further connecting elements between the third beam plane and at least one of the first and second beam planes, coupling the third beam plane and one of the first and second beam planes to one another in their movement.

[0026] This provides the technical advantage, for example, of enabling differential capacitive evaluation of a measurement signal. Furthermore, it provides the technical advantage of improving the signal-to-noise ratio.

[0027] The third beam level can, for example, have a greater thickness and / or be constructed differently from, for example, the first beam level and / or, for example, the second beam level. For example, the third beam level has a different layer structure than the first beam level and / or the second beam level. In one embodiment of the MEMS component method, it is provided that the beams of the beam levels are arranged vertically and / or laterally offset from one another.

[0028] This provides the technical advantage, for example, that the fill factor of the beam area, i.e. the area of ​​the substrate recess covered by the beams, can be varied...

[0029] In one embodiment of the MEMS component, it is provided that it comprises a suspension beam on which the beam construction is suspended.

[0030] This provides the technical advantage, for example, that the beam construction can be arranged efficiently.

[0031] In one embodiment of the MEMS component, it is provided that the beams of one of the beam planes extend in both longitudinal directions from the suspension beam.

[0032] This results in the technical advantage, for example, that a larger dynamic measuring range can be realized.

[0033] In one embodiment of the MEMS component, it is provided that a respective longitudinal extension of the beams of one of the beam planes is different.

[0034] This, for example, creates the technical advantage that the beams deform differently under load. This results in a greater change in capacitance and thus greater sensitivity....

[0035] In one embodiment of the MEMS component, the beams of the second and / or third beam levels each have a connection to the first beam level at both ends. This provides the technical advantage, for example, of preventing the beams from becoming jammed or stuck together.

[0036] In one embodiment of the MEMS component, it is provided that the beams of the second and / or third beam levels each have at least one free end.

[0037] This results in the technical advantage, for example, that measurement signals with higher intensity can be generated.

[0038] In one embodiment of the MEMS component, it is provided that the respective free end has an electrically insulated stop.

[0039] This provides the technical advantage, for example, that sticking and short circuits between the beam levels can be efficiently prevented.

[0040] In one embodiment of the MEMS component, it is provided that the respective free end has an electrically insulating stop.

[0041] A stop within the meaning of the description may, for example, be an electrically insulated stop and / or may, for example, be an electrically insulating stop.

[0042] A beam in the sense of the description is, for example, a bending beam.

[0043] The connecting elements, which also include the other connecting elements, connect the beam levels to be joined, for example, at points or in webs. This means that the connecting elements connect the beam levels to be joined at points or webs.

[0044] Beam levels within the meaning of the description are, in particular, arranged one above the other. This means, in particular, that the first beam level and the second beam level are arranged one above the other. This means, in particular, that the third beam level and the first beam level, or the second beam level, are arranged one above the other. For example, the third beam level is located below the first beam level, while, for example, the second beam level is located above the first beam level.

[0045] A MEMS component within the meaning of the description is, for example, a capacitive MEMS component.

[0046] A MEMS component in the sense of the description is, for example, a MEMS component that can detect a directional measurement variable.

[0047] A MEMS component within the meaning of the description is, for example, a mass flow sensor, in particular a directional mass flow sensor.

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

[0049] The MEMS component is, for example, an acoustic transducer or a pressure sensor. The pressure sensor is, for example, a relative pressure sensor. The acoustic transducer is, for example, a microphone, particularly a directional microphone.

[0050] Whenever only "component" is written, it should always be understood that this refers to the MEMS component.

[0051] The acoustic transducer is, for example, a loudspeaker.

[0052] The embodiments and exemplary embodiments described here can be combined with one another in any way, even if this is not explicitly described.

[0053] The invention is explained in more detail below using preferred embodiments. These show:

[0054] Fig. 1 shows a first MEMS component in a cross-sectional view,

[0055] Fig. 2 is a plan view of the first MEMS component of Fig. 1, Fig. 3 is a cross-sectional view of a second MEMS component,

[0056] Fig. 4 the second MEMS component in a plan view,

[0057] Fig. 5 shows a third MEMS component in a cross-sectional view,

[0058] Fig. 6 the third MEMS component in a plan view,

[0059] Fig. 7 shows a fourth MEMS component in a cross-sectional view,

[0060] Fig. 8 the fourth MEMS component in a plan view,

[0061] Fig. 9 shows a fifth MEMS component in a cross-sectional view,

[0062] Fig. 10 the fifth MEMS component in a plan view,

[0063] Fig. 11 a sixth MEMS component in a cross-sectional view and

[0064] Fig. 12 the sixth MEMS component in a top view.

[0065] In the following, the same reference symbols may be used for the same features.

[0066] Fig. 1 shows a first MEMS component 100 for sensing fluid mass flows.

[0067] The first MEMS component 100 comprises a substrate 101 having a recess 103. The first MEMS component 100 further comprises a beam structure 107 that at least partially spans the recess 103. A semiconductor layer 105, which is, for example, an insulating layer, is formed on the substrate 101 and simultaneously serves as an etch stop for etching the substrate recess. The beam structure 107 is anchored to the substrate 101 on one side.

[0068] The beam construction 107 comprises a first beam level 109, a plurality of connecting elements 111 and a second beam level 113.

[0069] The first beam level 109 comprises a plurality of first beams 114. The second beam level 113 comprises a plurality of second beams 115. The first and second beam levels 109, 113 are arranged one above the other. The first beam level 109 is located below the second beam level 113. The first beam level 109 is anchored to the substrate 101.

[0070] The connecting elements 111 connect the first beams 114 to the second beams 115 at specific points. The connection by the connecting elements 111 mechanically couples the first beams 114 to the second beams 115 in their movement. The connecting elements can be electrically insulated to electrically separate the beams from one another. The beam structure 107 is configured such that, upon application of an external force or pressure perpendicular to its main extension plane, the distance between the electrode layers changes, leading to a change in the measuring capacitance. Thus, a vertical deflection of the beam structure 107 generates tensile stress in one of the beam planes, while the other is subjected to compressive stress, causing its beams to bulge.

[0071] For example, a first electrode layer 117 and a second electrode layer 119 are shown in the context of this description. The two electrode layers 117, 119 together form a readable capacitance. The electrode layers can, for example, be formed by the bars themselves.

[0072] Furthermore, according to the first MEMS component 100, a one-sided suspension of the beam structure 107 is provided. Furthermore, it is provided that the beam levels have different thicknesses or a different layer structure. In the present case, for example, the first beam level 109 is thicker than the second beam level 113. In other words, the first beams 114 of the first beam level 109 are thicker than the second beams 115 of the second beam level 113.

[0073] Fig. 2 shows a top view of the first MEMS component 100. A longitudinal direction of the first MEMS component 100 is indicated by an arrow with the reference numeral 201. A transverse direction of the first MEMS component 100 is indicated by an arrow with the reference numeral 203.

[0074] The first MEMS component 100 is, for example, a directional microphone. The first MEMS component 100 thus comprises a beam structure 107 arranged parallel to one another in two planes, with connecting elements 111, particularly at the beam ends.

[0075] Fig. 3 shows a second MEMS device 301 .

[0076] A beam structure 303 of the second MEMS component 301 is suspended from a suspension beam 305, from which the first beams 114 of the first beam level 109 extend.

[0077] Analogous to Figs. 1 and 2, the second MEMS component 301 also features a beam structure 303 arranged parallel in two planes one above the other, with connecting elements 111 at the beam ends. A suspension beam 305 is also provided. Two transverse beams 401, 403 are provided for connecting the individual second longitudinal beams 115 of the second beam plane 113, as shown in particular in the plan view according to Fig. 4. Analogous to the first MEMS component 100, the beam planes 109, 113 are of different thicknesses and have different layer structures. Furthermore, the connecting elements 111 each provide an electrically insulating connection between the two beam planes at both beam ends.

[0078] Fig. 5 shows a third MEMS component 501 comprising a beam structure 503. In addition to the first beam level 109 and the second beam level 113, the beam structure 503 includes a third beam level 505 comprising a plurality of third beams 507. The third beam level 505 is located below the first beam level 109.

[0079] Thus, a beam structure arranged parallel to one another in three planes with connecting elements 111 at the beam ends is also provided here. Furthermore, a suspension beam 305 is provided, from which the beam structure 503 is suspended. The beam structure 503 is suspended from the substrate 101 via the suspension beam 305.

[0080] Furthermore, there are also crossbeams here, the crossbeams 401, 403, which connect the individual second (double) longitudinal beams 115 of the second beam level 113. Furthermore, analogous to the crossbeams 401, 403, there are further crossbeams which, analogously to the third beams 507 of the third beam level 505, connect at their ends, but this is not visible due to the illustrations shown in Figs. 5 and 6, with Fig. 6 showing the third MEMS component 501 in a plan view.

[0081] The thickness or layer structure of the third beam level 505 and the second beam level 113 is symmetrical. Furthermore, the three beam levels 109, 113, and 505 are connected at both beam ends via connecting elements 111. The third MEMS component 501 is, for example, a directional microphone.

[0082] The third bar level 505 comprises a third electrode layer 509, which forms a readable capacitance with the first electrode layer 117. For example, a symmetrical arrangement is provided, ie, the middle bar level carries two electrodes: one facing upwards, the other facing downwards.

[0083] Fig. 7 shows a fourth MEMS component 701, whose beam construction 703 is constructed essentially analogously to the beam construction 503 of the third MEMS component 501. As a difference, beams of the second beam level 113 and the third beam level 505 have a free beam end, with the exception of the supply beams, which are identified by reference numerals 801, 803, 805, and 807 in Fig. 8, which shows the fourth MEMS component 701 in a plan view. However, the supply beams of the third beam level 505 are not visible in Figs. 7 and 8 for illustrative reasons.

[0084] According to the illustrations shown in Figures 7 and 8, the beam structure 703 is a beam structure arranged parallel to one another in two planes, vertically offset from one another, with connecting elements 111 only on supply beams 801, 803, 805, 807 and on cross beams 401, 403. Furthermore, a suspension beam 305 is provided. Furthermore, cross beams 401, 403 are provided for connecting the individual second longitudinal beams 115 of the second beam level 113. Similarly, cross beams are provided for connecting the individual longitudinal beams 507 of the third beam level 505. The thickness of the second beams 115 and the third beams 507 is symmetrical. Beams of the second and third beam levels 113, 505 have a free beam end in the direction of the suspension beam 305, with the exception of the supply beams 801, 803, 805, 807.

[0085] Fig. 9 shows a fifth MEMS component 901, which is constructed essentially analogously to the fourth component 701. The difference is that the beam construction 903 of the fifth MEMS component 901 is a parallel beam construction arranged vertically and laterally offset from one another in two planes, with connecting elements 111 only on the supply beams 801, 803, 805, 807 and on the cross beams 401, 403 (see also the top view of the fifth MEMS component 901 shown in Fig. 10). The statements made in connection with Figs. 7 and 8 also apply analogously to the fifth MEMS component 901.

[0086] Fig. 11 shows a sixth MEMS component 1101 having a beam structure 1103, which is a parallel beam structure arranged vertically offset from one another in two planes, with connecting elements 111 on cross-connection beams. For the second beams 115 of the second beam level 113, these cross-connection beams are designated by the reference numerals 1201, 1203, 1205, and 1207. Supply beams are designated by the reference numerals 1209, 1211, 1213, and 1215. Due to the representations chosen in Figs. 11 and 12, these supply beams are only visible for the second beams 115 of the second beam level 113, with Fig. 12 showing a plan view of the sixth MEMS component 1101. These supply beams 1209, 1211, 1213, 1215 do not have a free beam end, in contrast to the further beam 115 of the second beam level 113. The same applies analogously to the third beam 507 of the third beam level 505.

[0087] The sixth MEMS component 1101, for example, is a differential capacitive directional microphone.

[0088] For example, a thickness of the second beams 115 and the third beams 507 is symmetrical.

[0089] Directional mass flow sensors and microphones rely on the fluid flow field or sound velocity, due to dynamic pressure, causing a relative deflection of the electrodes. To achieve this, the dynamic pressure element should have a suitable, preferably low, flexural rigidity. Cantilever beams represent a good compromise between low flexural rigidity and high robustness. To build microphones that are as small as possible with a high signal-to-noise ratio and high sensitivity, a high capacitance density is desirable. The arrangement of electrodes along a periphery, as in the state of the art, is only partially suitable for this purpose.

[0090] According to the concept described here, at least two beam planes arranged one above the other with integrated electrodes are used to generate a measurement signal across the entire transducer surface and not just in the peripheral region. The two beam planes are connected to one another via a plurality of connecting elements at suitable points in such a way that, on the one hand, their movement is coupled to one another, and on the other hand, their deformation is independent of one another, resulting in a relative change in distance that can be capacitively read. The vertical spacing of the beam planes or electrodes is thus realized via a sacrificial layer deposition, which can be achieved much thinner and / or more precisely than lateral spacing using lithographic methods. The component can therefore be manufactured with higher sensitivity and / or smaller variance.

[0091] During construction, it may be provided, for example, that one of the beam levels has a different thickness and / or a different layer structure than the other beam level in order to be able to shift the position of the neutral fiber appropriately and / or to increase the robustness.

[0092] A third beam level with a third electrode layer, for example, can enable differential capacitive evaluation of the measurement signal. This measure can increase the signal-to-noise ratio.

[0093] The bars with the electrodes can be arranged vertically and / or laterally to each other with respect to the main extension plane of the transducer region.

[0094] The beam structure can be suspended from a suspension beam, from which beams extend in both longitudinal directions. These beams do not necessarily have to have the same longitudinal extension. This allows for a larger dynamic measuring range.

[0095] For example, the beams of the second and, if applicable, third beam level can be connected to the first beam level at both ends. This can be advantageous to prevent the beams from snagging or sticking together.

[0096] Alternatively, the beams of the second and, if applicable, third beam level can have at least one free end. For example, this free end can have an electrically isolated stop to prevent sticking and short circuits between the levels. However, in general, potentially higher signals can be generated with a free end.

Claims

Claims 1 . MEMS component (100, 301, 501, 701, 901, 1101) for sensing fluid mass flows, comprising: a substrate (101) having a recess (103), a beam construction (107, 303, 503, 703, 903, 1103) which at least partially spans the substrate recess (103) and is anchored to the substrate (101) on at least one side, wherein the beam construction (107, 303, 503, 703, 903, 1103) has a first beam plane (109) having a plurality of first beams (114) with a first electrode layer (117) and a second beam plane (113) spaced therefrom having a plurality of second beams (115) with a second electrode layer (119) and a plurality of the first and the second Beam plane (109, 113) has connecting elements (111) between the first and the second beam plane (109, 113) which couple to one another in their movement, wherein the beam construction (107, 303, 503, 703, 903, 1103) is arranged in such a way thatthat when an external force acts perpendicular to their main plane of extension, a distance between the first and second beams (114, 115) changes., 2. MEMS component (100, 301, 501, 701, 901, 1101) according to claim 1, wherein one of the beam planes (109, 113) has a greater thickness and / or is constructed differently from the other of the beam planes (109, 113).

3. MEMS component (100, 301, 501, 701, 901, 1101) according to claim 1 or 2, wherein the beam construction (107, 303, 503, 703, 903, 1103) comprises a third beam plane (505) spaced apart from the first and second beam planes (109, 113) and comprising a plurality of third beams (507) with a third electrode layer (509) and a plurality of the third beam plane (505) and one of the first and second beam planes (109, 113) coupled to one another in their movement. further connecting elements (111) between the third beam level (505) and one of the first and second beam levels (109, 113).

4. MEMS component (100, 301, 501, 701, 901, 1101) according to one of the preceding claims, wherein the beam planes (109, 113, 505) are arranged vertically and / or laterally offset from one another.

5. MEMS component (100, 301, 501, 701, 901, 1101) according to one of the preceding claims, comprising a suspension beam (305) on which the beam construction (107, 303, 503, 703, 903, 1103) is suspended.

6. MEMS component (100, 301, 501, 701, 901, 1101) according to claim 5, wherein the beams (114, 115, 507) of one of the beam planes (109, 113, 505) extend in both longitudinal directions from the suspension beam (305).

7. MEMS component (100, 301, 501, 701, 901, 1101) according to claim 6, wherein the beams (114, 115, 507) extending in both longitudinal directions have different longitudinal extensions.

8. MEMS component (100, 301, 501, 701, 901, 1101) according to one of the preceding claims with regard to the third beam level (505) as far as dependent on claim 3, wherein the beams (115, 507) of the second and / or the third beam levels (113, 505) each have a connection to the first beam level (109) at both ends.

9. MEMS component (100, 301, 501, 701, 901, 1101) according to one of claims 1 to 7 with regard to the third beam level (505) as far as dependent on claim 3, wherein the beams (115, 507) of the second and / or the third beam levels (113, 505) each have at least one free end.

10. MEMS component (100, 301, 501, 701, 901, 1101) according to claim 9, wherein the respective free end has an electrically insulated stop.

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