MEMS component

Abstract

The invention relates to a MEMS component for sensing fluid mass flows, comprising: a substrate having a recess, a beam construction at least partially spanning the substrate recess, which is anchored to the substrate on at least one side, wherein the beam construction comprises 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 second beam planes coupling the first and second beam planes to one another in their movement, wherein the beam construction is arranged in such a way that when an external force acts perpendicular to its main extension plane, a distance between the first and second beams changes.

Description

The invention relates to a MEMS component.Prior ArtPatent specification EP 2 664 058 B1 discloses a micromechanical component.Patent specification EP 3 568 595 B1 discloses a micromechanical device.Laid-open specification EP 3 796 671 A1 discloses a piezoelectric MEMS microphone.Laid-open specification CN 107872760 A discloses a MEMS microphone.Laid-open specification CN 114520947 A discloses a microphone arrangement.Capacitive MEMS microphones are particularly powerful with regard to signal-to-noise ratio, energy consumption and further processing. This has led to a substantial displacement of the electret microphones by the MEMS microphones.The development of MEMS microphones with a double diaphragm has once again led to a marked increase in the signal-to-noise ratio. In this concept, the fluidic, noisy damping between the rigid back electrode (back plate) and the movable dynamic pressure membrane is almost completely dispensed with. This is achieved in that the baking plate is mounted in a reduced pressure region between two membranes coupled to one another.In documents US 9,181,080 and US 9,986,344 two such double diaphragm microphones are disclosed. A disadvantage of this arrangement is the high mechanical rigidity of the double diaphragm structure, which limits its deflection capability and thus limits its sensitivity.Disclosure of the InventionThe object on which the invention is based is to provide a MEMS component.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 dependent claims.According to a first aspect, there is provided a MEMS device for sensing fluid mass flows, comprising:a substrate having a recess,a beam construction at least partially spanning the substrate recess, which beam construction is anchored on at least one side to the substrate,wherein the beam construction comprises a first beam plane having a first electrode layer and a second beam plane having a second electrode layer spaced apart therefrom and having a plurality of second beams, and a plurality of connecting elements between the first and the second beam plane, said connecting elements coupling the first and the second beam plane to one another in their movement,wherein the beam structure is configured such that upon the action of an external force perpendicular to its main extension plane, a distance between the first and second beams changes.Directional mass flow sensors or microphones are based in particular on the fact that the flow field of the fluid or the sound velocity brings about a relative deflection of electrodes due to dynamic pressure. For this purpose, the dynamic pressure element should have a suitable bending stiffness that is as low as possible. Bending beams represent a good compromise between low bending stiffness and high robustness. In order to be able to build as small as possible microphones with high signal-to-noise behavior and high sensitivity, a high measurement capacitance density is desirable. The arrangement of electrodes along a periphery, as described in the prior art described above, is only conditionally suitable for this purpose.According to the concept described here, at least two bar planes arranged one above the other with electrodes integrated thereon are used to generate a measurement signal over the entire transducer surface and not only in the region of the periphery. In this case, the two beam planes are connected to one another at suitable points via a plurality of connecting elements in such a way that, on the one hand, their movement is realized in a manner coupled to one another. On the other hand, their deformation is independent of each other, which leads to a relative change in distance which can be read out capacitively. A vertical spacing of the beam planes or electrodes is realized in particular via a sacrificial layer deposition, which can be effected substantially thinner and more precisely than lateral spacings defined by lithographic methods. The MEMS device can thus be manufactured with a higher sensitivity and a lower variance.The concept described here brings about, in particular, a high capacity density and a large design freedom.Furthermore, the concept described here advantageously makes it possible to provide a MEMS component which, in comparison with the aforementioned prior art, enables a small structural size with the same power or a higher power with the same structural size.The abbreviation "MEMS" stands for micro-electromechanical system (micro-electromechanical system).The beams may be formed of the electrode layers themselves, for example. The electrode layers are arranged or applied, for example, on the beam.In one embodiment of the MEMS component, it is provided that one of the beam planes has a greater thickness and / or is constructed differently from the other of the beam planes.This brings about, for example, the technical advantage that one of the planes can be designed to be more rigid than the other plane. In this way, the deformation under load during operation can be designed to be advantageous in a targeted manner, for example in order to increase robustness with respect to overloading or in order to increase sensitivity.The fact that the beam planes can be constructed differently means, in particular, that one of the beam planes has a different layer construction than the other of the beam planes.In one embodiment of the MEMS component, it is provided that the beam construction has a third beam plane, which has a plurality of third beams and is spaced apart from the first and the second beam plane, having a third electrode layer, and a plurality of further connecting elements, which couple the third beam plane and one of the first and the second beam planes to one another in terms of their movement, between the third beam plane and at least one of the first and the second beam planes.This brings about, for example, the technical advantage that differential-capacitive evaluation of a measurement signal is made possible. Furthermore, this brings about the technical advantage, for example, that a signal-to-noise ratio can be increased.The third beam plane can have a greater thickness, for example, and / or be constructed differently from, for example, the first beam plane and / or, for example, the second beam plane. For example, the third beam plane has a different layer structure than the first beam plane and / or than the second beam plane.In one embodiment of the method of the MEMS component, it is provided that the beams of the beam planes are arranged vertically and / or laterally offset with respect to one another.This has the technical advantage, for example, that the fill factor of the beam region, i.e., the area of the substrate recess covered by the beams, can be varied...In one embodiment of the MEMS component, it is provided that it comprises a suspension beam, on which the beam construction is suspended.This brings about, for example, the technical advantage that the beam construction can be arranged efficiently.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.This brings about, for example, the technical advantage that a larger dynamic measurement range can be realized.In one embodiment of the MEMS component, it is provided that a respective longitudinal extent of the beams of the one of the beam planes is different.This brings about, for example, the technical advantage that the beams are deformed differently under load. This results in a greater change in capacitance and thus a greater sensitivity...In one embodiment of the MEMS component, it is provided that the beams of the second and / or the third beam planes each have a connection to the first beam plane at both ends.This brings about the technical advantage, for example, that interlocking or adhesive bonding of the beams can be avoided.In one embodiment of the MEMS component, it is provided that the beams of the second and / or the third beam planes each have at least one free end.This brings about the technical advantage, for example, that measurement signals can be generated with higher intensity.In one embodiment of the MEMS component, provision is made for the respective free end to have an electrically insulated stop.This brings about the technical advantage, for example, that adhesion and a short circuit between the beam planes can be efficiently prevented.In one embodiment of the MEMS component, it is provided that the respective free end has an electrically insulating stop.A stop in the sense of the description can be, for example, an electrically insulated stop and / or can be, for example, an electrically insulating stop.A beam in the sense of the description is, for example, a bending beam.The connecting elements, wherein the other connecting elements are also included therewith, connect the beam planes to be connected, for example, in a point-like or web-like manner. This therefore means that the connecting elements connect the beam planes to be connected to one another at points or webs.Bar planes in the sense of the description are arranged in particular one above the other. This thus means in particular that the first beam plane and the second beam plane are arranged one above the other. This therefore means in particular that the third beam plane and the first beam plane or the second beam plane are arranged one above the other.For example, the third beam plane is located below the first beam plane, wherein, for example, the second beam plane is located above the first beam plane.A MEMS component in the sense of the description is, for example, a capacitive MEMS component.A MEMS component in the sense of the description is, for example, a MEMS component which can capture, for example, a directional measurement variable.A MEMS component in the sense of the description is, for example, a mass flow sensor, in particular a directional mass flow sensor.The phrase "at least one(s)" means "one(s) or more.".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, in particular a directional microphone.If only "component" is written, it is always to be read as well that this is the MEMS component.The acoustic transducer is, for example, a loudspeaker.The embodiments and exemplary embodiments described here can be combined with one another in any desired manner, even if this is not explicitly described.The invention is explained in more detail below with reference to preferred exemplary embodiments. The following are shown here: FIG. 1 shows a first MEMS component in a cross-sectional view, FIG. 2 shows a plan view of the first MEMS component of FIG. 1, FIG. 3 shows a second MEMS component in a cross-sectional view, FIG. 4 shows the second MEMS component in a plan view, FIG. 5 shows a third MEMS component in a cross-sectional view, FIG. 6 shows the third MEMS component in a plan view, FIG. 7 shows a fourth MEMS component in a cross-sectional view, FIG. 8 shows the fourth MEMS component in a plan view, FIG. 9 shows a fifth MEMS component in a cross-sectional view, FIG. 10 shows the fifth MEMS component in a plan view, FIG. 11 shows a sixth MEMS component in a cross-sectional view, and FIG. 12 shows the sixth MEMS component in a plan view.The same reference numerals can be used below for the same features.FIG. 1 shows a first MEMS device 100 for sensing fluid mass flows.The first MEMS component 100 comprises a substrate 101 which has a recess 103. Furthermore, the first MEMS component 100 comprises a beam construction 107, which at least partially spans the recess 103.A semiconductor layer 105, which is, for example, an insulation layer and which at the same time serves as an etching stop for the etching of the substrate recess, is formed on the substrate 101. The beam structure 107 is anchored at one side to the substrate 101.The beam construction 107 comprises a first beam plane 109, a plurality of connecting elements 111 and a second beam plane 113.The first beam plane 109 comprises a plurality of first beams 114. The second beam plane 113 comprises a plurality of second beams 115. The first and the second beam plane 109, 113 are arranged one above the other. In this case, the first beam plane 109 is located below the second beam plane 113. The first beam plane 109 is anchored to the substrate 101.The connecting elements 111 connect the first beams 114 to the second beams 115 at points. The connection by the connecting elements 111 causes a mechanical coupling of the first beams 114 to the second beams 115 in their movement. The connecting elements can be designed to be electrically insulated in order to electrically separate the beams from one another. In this case, the beam structure 107 is configured such that, when an external force or pressure acts perpendicularly on its main extension plane, a distance between the electrode layers changes, which leads to a change in the measurement capacitance. Thus, a vertical deflection of the beam construction 107 generates a tensile stress in one of the beam planes, while the other one comes under compressive stress, so that the beams thereof bulge out.By way of example, a first electrode layer 117 and a second electrode layer 119 are drawn in in the sense of this description. The two electrode layers 117, 119 together form a readable capacitance. The electrode layers may be formed by the beams themselves, for example.Furthermore, according to the first MEMS component 100, a one-sided suspension of the beam construction 107 is provided. Furthermore, it is provided that the beam planes are of different thicknesses or have a different layer structure. In the present case, for example, the first beam plane 109 is configured to be thicker than the second beam plane 113. In other words, the first beams 114 of the first beam plane 109 are thicker than the second beams 115 of the second beam plane 113.FIG. 2 shows a plan view of the first MEMS component 100. A longitudinal direction of the first MEMS component 100 is identified by an arrow with the reference symbol 201. A transverse direction of the first MEMS device 100 is indicated by an arrow with the reference sign 203.The first MEMS device 100 is, for example, a directional microphone. The first MEMS component 100 thus comprises a beam construction 107 arranged parallel one above the other in two planes, with connecting elements 111, in particular at the beam ends.FIG. 3 shows a second MEMS component 301.A beam construction 303 of the second MEMS device 301 is suspended on a suspension beam 305, from which the first beams 114 of the first beam plane 109 extend.Analogously to FIGS. 1 and 2, a beam construction 303 arranged parallel one above the other in two planes and having connecting elements 111 at the beam ends is also provided in the second MEMS component 301. Furthermore, a suspension beam 305 is provided. Furthermore, two cross beams 401, 403 are provided for connecting the individual second longitudinal beams 115 of the second beam plane 113, which in particular shows the plan view according to FIG. 4. Analogously to the first MEMS component 100, the beam planes 109, 113 here too have different thicknesses or have a different layer structure. Furthermore, the connecting elements 111 respectively bring about an electrically insulating connection of the two beam planes at both beam ends.FIG. 5 shows a third MEMS component 501 having a beam construction 503. In the beam construction 503, a third beam plane 505 having a plurality of third beams 507 is provided in addition to the first beam plane 109 and the second beam plane 113. The third bar plane 505 is located below the first bar plane 109.Thus, a beam construction arranged parallel in three planes one above the other with connecting elements 111 at the beam ends is also provided here. Furthermore, a suspension beam 305 is provided, on which the beam construction 503 is suspended. The beam construction 503 is suspended on the substrate 101 via the suspension beam 305.Furthermore, there are also cross beams here, the cross beams 401, 403, which connect the individual second (double) longitudinal beams 115 of the second beam plane 113. Furthermore, there are further crossbars analogous to the crossbars 401, 403, which similarly connect the third beams 507 of the third beam plane 505 at their ends, which is not visible, however, on account of the representations shown in FIGS. 5 and 6, wherein FIG. 6 shows the third MEMS component 501 in a plan view.A thickness or a layer structure of the third beam plane 505 and the second beam plane 113 is symmetrical. Furthermore, a connection of the three beam planes 109, 113, 505 at both beam ends is provided via the connecting elements 111. The third MEMS device 501 is, for example, a directional microphone.The third beam plane 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, i.e. the central beam plane carries two electrodes: one upwards, the other downwards.FIG. 7 shows a fourth MEMS component 701, the beam construction 703 of which is constructed substantially analogously to the beam construction 503 of the third MEMS component 501. In contrast, beams of the second beam plane 113 and the third beam plane 505 have a free beam end, with the exception of the lead beams, which are identified in FIG. 8, which shows the fourth MEMS component 701 in a plan view, by reference numerals 801, 803, 805 and 807. However, the feed bars of the third bar plane 505 are not visible in FIGS. 7 and 8 for the sake of illustration.According to the representations shown in FIGS. 7 and 8, the beam construction 703 is a beam construction with connecting elements 111 arranged parallel to and vertically offset from one another in two planes, only on feed 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 plane 113. Similarly, cross beams are provided for connecting the individual longitudinal beams 507 of the third beam plane 505. A thickness of the second beams 115 and the third beams 507 is symmetrical. Beams of the second and third beam planes 113, 505 have a free beam end in the direction of the suspension beams 305, with the exception of the feed beams 801, 803, 805, 807.FIG. 9 shows a fifth MEMS component 901, which is constructed substantially analogously to the fourth component 701. By contrast, the beam construction 903 of the fifth MEMS component 901 is a beam construction with connecting elements 111 arranged parallel to and vertically and laterally offset from one another in two planes only on lead beams 801, 803, 805, 807 and on cross beams 401, 403 (cf. also the plan view of the fifth MEMS component 901 shown in FIG. 10 ). The explanations made in connection with FIGS. 7 and 8 also apply analogously to the fifth MEMS component 901.FIG. 11 shows a sixth MEMS component 1101 having a beam structure 1103, which is a beam structure arranged parallel to and vertically offset from one another in two planes, with connecting elements 111 on transverse connecting beams. For the second beams 115 of the second beam plane 113, these cross-connection beams are denoted by the reference numerals 1201, 1203, 1205 and 1207. Feeder bars are designated with the reference numerals 1209, 1211, 1213, and 1215. These lead beams are visible only for the second beams 115 of the second beam plane 113 on the basis of the representations selected in FIGS. 11 and 12, wherein FIG. 12 shows a plan view of the sixth MEMS component 1101. These feed bars 1209, 1211, 1213, 1215 do not have a free bar end, in contrast to the further bars 115 of the second bar plane 113. The same applies analogously to the third beams 507 of the third beam plane 505.The sixth MEMS device 1101 is, for example, a differentially capacitive directional microphone.A thickness of the second beams 115 and the third beams 507 is, for example, symmetrical.Directional mass flow sensors or microphones are based on the fact that the flow field of the fluid or the sound velocity causes a relative deflection of electrodes due to dynamic pressure. For this purpose, the dynamic pressure element should have a suitable bending stiffness that is as low as possible. Bending beams represent a good compromise between low bending stiffness and high robustness. In order to be able to build as small as possible microphones with high signal-to-noise behavior and high sensitivity, a high measurement capacitance density is desirable. The arrangement of electrodes along a periphery as in the prior art is only conditionally suitable for this purpose.According to the concept described here, in particular at least two bar planes arranged one above the other with electrodes integrated thereon are used to generate a measurement signal over the entire transducer surface and not only in the region of the periphery. The two beam planes are connected to one another at suitable points via a plurality of connecting elements in such a way that, on the one hand, their movement is realized in a coupled manner to one another and, on the other hand, their deformation is independent of one another, which leads to a relative change in distance which can be read out capacitively. The vertical spacing of the beam planes or electrodes is therefore realized via a sacrificial layer deposition, which can be effected substantially thinner and / or more precisely than lateral spacings by means of lithographic methods. The component can thus be produced with a higher sensitivity and / or a lower variance.During the construction, it can be provided, for example, that one of the beam planes has a different thickness and / or a different layer construction than the other beam plane, in order to be able to suitably shift the position of the neutral fiber and / or to be able to increase the robustness.A third beam plane with a third electrode layer can enable, for example, differential-capacitive evaluation of the measurement signal. This measure allows the signal-to-noise ratio to be increased.The beams with the electrodes can be arranged vertically and / or laterally with respect to one another with respect to the main extension plane of the transducer region.The beam construction may be suspended from a suspension beam from which the beams extend in both longitudinal directions. These need not necessarily have the same longitudinal extent. In this way, a larger dynamic measurement range can be realized.The beams of the second and optionally third beam plane can have a connection to the first beam plane at both ends, for example. This can be advantageous in order to be able to avoid jamming and gluing of beams.The beams of the second and optionally third beam plane can alternatively have at least one free end. For example, this free end can have an electrically insulated stop in order to prevent sticking and a short circuit between the planes. Generally, however, potentially higher signals can be generated at a free end.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 2 664 058 B1

[0002] EP 3 568 595 B1

[0003] EP 3 796 671 A1

[0004] CN 107872760 A

[0005] CN 114520947 A

[0006] U.S. Pat. No. 9,181,080

[0009] U.S. Pat. No. 9,986,344

[0009]

Claims

A MEMS component (100, 301, 501, 701, 901, 1101) for sensing fluid mass flows, comprising: a substrate (101) having a recess (103), a beam structure (107, 303, 503, 703, 903, 1103) at least partially spanning the substrate recess (103) and anchored on at least one side to the substrate (101), wherein the beam structure (107, 303, 503, 703, 903, 1103) has a first beam plane (109) having a first electrode layer (117) and having a second beam plane (113) having a second electrode layer (119) spaced apart therefrom and having a plurality of second beams (115), and a plurality of the first and the second beam plane (109, 113) has connecting elements (111) coupling to one another in their movement between the first and the second beam plane (109, 113), wherein the beam structure (107, 303, 503, 703, 903, 1103) is configured such that a distance between the first and second beams (114, 115) changes when an external force acts perpendicularly on their main extension plane.The MEMS device (100, 301, 501, 701, 901, 1101) of 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).The MEMS device (100, 301, 501, 701, 901, 1101) according to claim 1 or 2, wherein the beam structure (107, 303, 503, 703, 903, 1103) comprises a third beam plane (505), which comprises a plurality of third beams (507) and is spaced apart from the first and the second beam plane (109, 113), having a third electrode layer (509), and a plurality of further connecting elements (111), which couple the third beam plane (505) and one of the first and the second beam planes (109, 113) to one another in terms of their movement, between the third beam plane (505) and the one of the first and the second beam planes (109, 113).The MEMS device (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 with respect to one another.The MEMS device (100, 301, 501, 701, 901, 1101) according to one of the preceding claims, comprising a suspension beam (305), on which the beam structure (107, 303, 503, 703, 903, 1103) is suspended.The MEMS device (100, 301, 501, 701, 901, 1101) of 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).The MEMS device (100, 301, 501, 701, 901, 1101) of claim 6, wherein the beams (114, 115, 507) extending in both longitudinal directions have different longitudinal extents.MEMS component (100, 301, 501, 701, 901, 1101) according to one of the preceding claims with regard to the third beam plane (505) insofar as it relates back to claim 3, wherein the beams (115, 507) of the second and / or of the third beam planes (113, 505) each have a connection to the first beam plane (109) at both ends.MEMS component (100, 301, 501, 701, 901, 1101) according to one of Claims 1 to 7 with respect to the third beam plane (505) insofar as it relates back to Claim 3, wherein the beams (115, 507) of the second and / or of the third beam planes (113, 505) each have at least one free end.The MEMS device (100, 301, 501, 701, 901, 1101) of claim 9, wherein the respective free end comprises an electrically insulated stop.

Images