MEMS sensor and method for compensating systematic measurement deviations in MEMS sensor

Abstract

The invention relates to a MEMS sensor (100) comprising: a substrate (40) having a main plane of extension; a vibration mass (60) which is movably suspended in the z-direction (1000) relative to the substrate (40); and a sensor device (90) for detecting a measurement signal dependent on the position of the vibration mass (60). The at least two resonators (10, 11, 12) are suspended in an elastically movable manner relative to the substrate in the z-direction (1000). The actuatable electrode arrangement (30) is designed to resonate each of the at least two resonators (10, 11, 12) in order to generate a mechanical resonant vibration and to capacitively detect an interference variable dependent on at least one resonant frequency of the resonant vibration. The invention also relates to a method for compensating for systematic measurement deviations of a MEMS sensor (100).

Description

Technical Field

[0001] The invention relates to a MEMS sensor (MEMS: Microelektromechanisches System, Mikrosystem Micro-Electromechanical System, Microsystem), such as a MEMS inertial sensor or a MEMS acceleration sensor, and also to a method for compensating for systematic measurement deviations that typically occur in MEMS sensors. Background Art

[0002] Acceleration sensors are often designed as capacitive sensors. The seismic mass of a capacitive acceleration sensor can be designed as an asymmetric rocker. For example, EP 0773 443A1 describes a micromechanical acceleration sensor with a seismic mass designed as an asymmetric rocker. DE 10 2020205 616A1 discloses an acceleration sensor with a sensor device that generates a measurement signal that is related to the position of a moving mass. The sensor device can, for example, have a total of four upper and lower electrodes, wherein the upper and lower electrodes are electrically connected to each other, in particular in pairs, so that a differential signal corresponding to the difference between a first capacitance and a second capacitance can be detected and evaluated. Summary of the invention

[0003] Based on this background, it is an object of the present invention to provide an improved MEMS sensor and an improved method for compensating for systematic measurement deviations in MEMS sensors.

[0004] The above-mentioned object is achieved by the present invention. Advantageous embodiments of the present invention are described in detail herein.

[0005] A MEMS sensor, in particular a MEMS acceleration sensor or a MEMS inertial sensor, comprises a substrate with a main extension plane, a seismic mass suspended movably relative to the substrate, and a sensor device for detecting a measurement signal related to the position of the seismic mass relative to the substrate. According to the invention, in addition to the sensor device, at least two resonators are additionally provided, which are suspended in a manner elastically movable relative to the substrate in a z-direction extending perpendicularly to the main extension plane. For this purpose, in a configuration, the at least two resonators are, for example, elastically suspended on the seismic mass or on an anchoring portion fixedly connected to the substrate. The controllable electrode assembly is constructed to resonantly excite each of the at least two resonators, in particular corresponding to the resonant frequency of the resonator, and to capacitively detect a disturbance variable related to the resonant frequency of the resonantly excited resonator. In order to control the electrode assembly, the electrode assembly can be connected to a control and analysis and evaluation unit, which is also constructed to compensate for systematic measurement deviations in the measurement signal of the sensor device as a function of the detected disturbance variable.

[0006] The resonant frequency of the excited resonator is dependent on the mechanical distortion or deformation of the substrate, in particular due to the electrostatic spring softening effect, so that the capacitive detection of the interference variable can provide an independent measure of the unknown deformation, which only occurs during operation, in particular. It is thus possible to identify faults or to determine fault-related interference variables during operation and / or during calibration, in particular in real time, in order to compensate for deviations in the measurement signal of the sensor device.

[0007] The resonant frequency is determined by the mechanical vibration spectrum of the resonator. The control and evaluation unit of the MEMS sensor is designed, in particular in addition to conventional sensors, to control the electrode arrangement for resonantly exciting the resonator in a corresponding frequency range in order to excite the resonator to a corresponding resonant vibration.

[0008] The MEMS sensor, in particular a MEMS acceleration sensor or a MEMS inertial sensor, is designed to compensate for systematic measurement deviations. The substrate forms a layer in the layer structure of the MEMS sensor and therefore represents in particular deformations of the layer structure, which are caused by the production or assembly of the MEMS sensor or only occur during the operation of the MEMS sensor. Preferably, the at least two resonators are formed by recesses in a layer of the layer structure.

[0009] According to one possible embodiment, the seismic mass is designed as a deflectable, in particular asymmetrical, rocker, which is anchored to the substrate via at least one torsion spring so that it can be displaced about a torsion axis.

[0010] At least two resonators are preferably spaced apart from one another laterally in a plane of the layer structure perpendicular to the z-direction (or parallel to the main extension plane) so that even small deviations of the plane-parallel layer arrangement can be reliably detected. Particularly preferably, the resonators are arranged on opposite sides of the torsion axis, in particular mirror-symmetrically with respect to the torsion axis.

[0011] Preferably, each resonator is assigned a drive electrode and a detection electrode, so that the respectively assigned resonator can be resonantly excited by means of the drive electrode, and a measurement variable related to the resonant frequency of the resonantly excited resonator can be detected by means of the detection electrode. The separate detection electrode advantageously improves the measurement accuracy of detecting the interference variable related to the resonant frequency of the resonantly excited resonator.

[0012] In order to compensate for systematic measurement deviations, the resonators are preferably designed as single-sided or double-sided suspended structural elements, in particular substantially in the form of beams, fingers, pistons or forks. It is further preferred that these structural elements are designed in the same way so that at least two resonators, in particular the four resonators provided in the embodiment, substantially, thus in particular in the absence of mechanical stress, have the same mechanical vibration spectrum.

[0013] In a possible embodiment of the electrode assembly, the drive electrode and the detection electrode are arranged in a plane extending substantially parallel to the main extension plane, in particular on a substrate. Alternatively, a sandwich arrangement is also possible, in which the drive electrode and the detection electrode are arranged relative to each other in two planes extending substantially parallel to the main extension plane. In this arrangement, the resonator is arranged between the drive electrode and the detection electrode and is spaced apart from these electrodes in the z direction.

[0014] In one embodiment, at least three, preferably four, resonators are provided which are spaced apart from one another in a plane perpendicular to the stacking direction in an arrangement deviating from a collinear arrangement in the transverse direction. In other words, the resonators are arranged in this plane such that the surface curvature of the substrate is detectable in the main extension plane, in particular in the x-direction and the y-direction.

[0015] To generate a measurement signal of the sensor device, the position of the movable mass is capacitively detected with respect to at least one spatial direction, for example with respect to the z direction. The resonator is, for example, elastically fastened to the seismic mass of the MEMS sensor so that the movement of the resonator is coupled to the movement of the seismic mass.

[0016] In a method for compensating for systematic measurement deviations of a MEMS sensor, at least two resonators are excited to produce mechanical resonant vibrations by means of the electrode assembly already described, and a disturbance variable associated with the resonant frequency of the resonant vibrations is capacitively detected. Systematic measurement deviations in the measurement signal of the sensor device are compensated based on the detected disturbance variable.

[0017] The measured variable related to the resonant frequency of the resonantly excited resonator is, due to the electrostatic spring softening effect, in particular related to the size of the gap or deflection of the resonator relative to the substrate, in particular to any deformation of the substrate related to the position of the resonator. The detected interference variable thus provides a signal suitable for compensating the output signal, which also includes interference variables of unknown origin, which may only occur when the MEMS sensor is installed and / or during operation of the MEMS sensor.

[0018] Preferably, systematic measurement deviations in the output signal of the MEMS sensor are compensated in an analog or digital manner using the detected disturbance variable.

[0019] Further preferably, for resonant excitation of the resonator, a pulsed or continuous excitation signal, in particular a harmonic excitation signal or an excitation signal with a time-varying frequency, is applied to the counter-electrode component, in particular to the drive electrode.

[0020] Further details and advantages of the present invention are explained in detail below based on the exemplary embodiments described in the accompanying drawings. In the drawings:

[0021] Figures 1A to 1C A cross section and two top views are shown for describing an acceleration sensor;

[0022] Figure 2 Shown by Figures 1A to 1C A cross section of an accelerometer used to describe how the accelerometer functions;

[0023] Figure 3 Shown by Figures 1A to 1C Cross section of an accelerometer under mechanical stress applied to the accelerometer;

[0024] Figure 4 The mechanical operating principle of a MEMS sensor, which is designed for compensating systematic measurement deviations and is based on two resonantly excited resonators, is schematically shown in a schematic sectional view;

[0025] Figure 5 Shown in a schematic cross-sectional view Figure 4 Details of the mechanical principle of action;

[0026] 6a to 6d show exemplary different configurations which can be detected based on the aforementioned mechanical action principle;

[0027] Figure 7 The implementation of a resonator in a layer complex of a MEMS sensor is shown in a perspective view;

[0028] Figure 8 Shown in cross-section Figure 7 resonator;

[0029] Fig. 9 Shown in top view Figure 7 resonator;

[0030] Fig.10 Another embodiment of a MEMS sensor configured to compensate for systematic measurement deviations is shown in a top view;

[0031] Fig.11 A cross-sectional view shows Fig.10MEMS sensors;

[0032] Fig.12 Shown in perspective Fig.10 MEMS sensors;

[0033] Fig.13 Shown in detail Fig.10 Resonators of MEMS sensors;

[0034] Fig.14 A detailed view of the back side of the MEMS sensor with a channel structure for electrical contact;

[0035] Fig.15 Another embodiment of a MEMS sensor is shown in a top view;

[0036] Fig.16 A further implementation of a resonator in a layer complex of a MEMS sensor is shown in a top view;

[0037] Fig.17 Shown in cross-section Fig.16 resonator;

[0038] Fig.18 Shown in perspective Fig.16 resonator;

[0039] Fig.19 Shown in side view Fig.16 resonator; DETAILED DESCRIPTION

[0040] Identical or mutually corresponding elements are provided with the same reference symbols in all figures.

[0041] Figures 1A to 1C A cross section and two top views are shown for describing an acceleration sensor having a sensor arrangement 90 for detecting measurement signals which are generated as a function of inertial forces and / or acceleration forces acting on the sensor.

[0042] exist Figure 1A The capacitive acceleration sensor shown in cross section in FIG. 4 is designed to detect an acceleration oriented perpendicularly to a wafer or flat substrate 40 (in the z direction) and to determine a magnitude corresponding to this acceleration. For this purpose, a seismic mass 60 designed as an asymmetrical rocker is arranged above substrate 40 in a positionally variable manner. Seismic mass 60 is connected to two torsion springs 70 (see FIG. 4 ). Figure 1B ) is connected to the anchor bolt 20, which is fixedly arranged on the substrate 40. The torsion spring 70 (see in particular Figure 1B ) extends along a torsion axis 72, about which the seismic mass 60 designed as a rocker can change position.

[0043] Seismic mass 60 comprises a first upper electrode 80a arranged on a first side of torsion axis 72 and a second upper electrode 80b arranged on a second side of torsion axis 72. Due to additional mass 62, second electrode 80b has a greater mass than first measuring electrode 80a.

[0044] The counter electrodes, referred to as first and second bottom electrodes 84a, 84b, are fixedly arranged on substrate 40. The sensor principle of the acceleration sensor is therefore based on a spring-mass system in which the movable seismic mass 60 forms two plate capacitors with the counter electrodes 84a and 84b fixed on wafer 40. Figure 1C Counter electrodes 24a and 24b shown in a top view are arranged relative to electrodes 80a and 80b of seismic mass 60 such that the position of seismic mass 60 relative to substrate 40 can be determined by evaluating a first capacitance between electrode 80a and an associated first counter electrode 84a and a second capacitance between electrode 80b and an associated second counter electrode 84b.

[0045] Figure 2 Shown by Figures 1A to 1C The cross section of an accelerometer is used to describe the function of the accelerometer. Figure 2 1000 is subjected to acceleration in the z direction, a force directed toward the substrate 40 acts on the second upper electrode 80b due to the additional mass 62. Due to the acceleration, the seismic mass 60 configured as a rocker changes position around the torsion axis 72, so that the first average distance d1 between the first upper electrode 80a and the first lower electrode 84a increases, and the second average distance d2 between the second upper electrode 80b and the second lower electrode 84b decreases.

[0046] The capacitance changes of the two capacitors formed by the upper electrodes 80a and 80b and the lower electrodes 84a and 84b correspond to the changes in the distances d1 and d2, which can then be evaluated to determine or determine the applied acceleration. Methods for evaluating capacitance changes are known from the background art and are therefore not discussed further here.

[0047] Figure 3 Shown by Figures 1A to 1C Cross section of an accelerometer with mechanical stress applied to the accelerometer.

[0048] exist Figure 3The mechanical stress acts on the wafer or substrate 40, and the substrate 40 is bent asymmetrically along the y direction by the mechanical stress. Due to the asymmetrical bending of the substrate 40, for example, the first average distance d1 between the first upper electrode 80a and the first lower electrode 84a changes. Similarly, under the influence of the mechanical stress, the second average distance d2 between the second upper electrode 80b and the second lower electrode 84b increases or decreases.

[0049] Thus, in the acceleration sensor, mechanical stresses applied, for example via force or pressure, to at least a part of the acceleration sensor, in particular to a subunit of the housing or substrate 40, cause a capacitance change of the capacitor composed of the upper electrodes 80a and 80b and the lower electrodes 84a and 84b. Normally, an evaluation device (not shown) of the acceleration sensor cannot distinguish between a capacitance change caused by stress influences and a capacitance change caused by the acceleration of the acceleration sensor.

[0050] It is desirable that inertial sensors or acceleration sensors do not generate measurement signals without external excitation or force, which could be incorrectly interpreted by the evaluation electronics as inertial forces or accelerations acting on the sensor. However, in practical applications, the measurement signals of such commonly constructed sensor devices are usually characterized by systematic measurement deviations, which are also called biases or offsets and are caused, for example, by process-related defects in the sensor during production and / or stresses, deformations of the layer structure and / or by assembly errors. However, measurement deviations caused by random effects, such as incorrect assembly of the sensor, are often not determined in advance.

[0051] Figure 4 The schematic sectional view shows the mechanical operating principle of a device 1 for detecting disturbance variables that are associated with typically occurring systematic measurement errors of MEMS sensors, in particular MEMS inertial sensors or MEMS acceleration sensors. The device 1 is implemented as a layer composite of a MEMS sensor 100 and comprises at least two resonators 10, 11, 12 that can be excited to resonate natural vibrations.

[0052] In the example shown, at least two resonators 10, 11, 12 are elastically suspended on a seismic mass 60, which is fastened to an anchor 20 in a manner that allows for displacement about a torsion axis 72. The anchor 20 is fixedly connected to a stationary flat substrate 40 in such a way that a gap 50 is formed between the substrate 40 and the resonators 10, 11, 12. The main extension plane of the substrate 40 extends perpendicularly to the plane of the drawing. The resonators 10, 11, 12 are provided to be excited to resonant vibrations by means of an electrode assembly 30. For this purpose, the electrode assembly 30 has two drive electrodes 31, which are arranged on the substrate 40 opposite the front of the resonators 10, 11, 12.

[0053] The resonance excitation of the resonators 10, 11, 12 is carried out by actuating or applying a voltage to the electrode assembly 30, in particular the drive electrode 31. Figure 4 The control and evaluation unit 95 (see in particular Fig.10 ), which is connected to the electrode assembly 30.

[0054] For example, the resonant excitation of the resonators 10, 11, 12 can be performed continuously during the operation of the MEMS sensor 100 by means of a harmonic drive signal, or alternatively only for a short duration during calibration of the MEMS sensor 100, in particular before the start of operation of the MEMS sensor 100. Alternatively, the excitation can be performed by means of a so-called chirp signal, i.e. an excitation signal with a time-varying frequency, in particular a frequency that increases or decreases over time.

[0055] The electrode assembly 30 is also designed to capacitively detect interference variables that are related to the resonance frequency of the resonantly excited resonators 10, 11, 12. Such interference variables may be caused, for example, by a relative shift of the resonance frequencies of the two resonators 11, 12, which can be caused in particular by mechanical distortions. The capacitive determination of such interference variables is used in particular to compensate for systematic measurement deviations in the measurement signal of the MEMS sensor 100, which is provided independently of the sensor device 90 of the MEMS sensor 100. The sensor device 90 can be provided in a conventional manner, in particular as described at the beginning with reference to FIGS. 1 to 12. Figure 3 As described, it is designed to detect a measurement signal which is dependent on the position of the seismic mass relative to substrate 40. From the measurement signal of sensor device 90, a measure of the acceleration acting on MEMS sensor 100 can be derived.

[0056] In a possible embodiment, the detection of one or more resonance frequencies or disturbance variables related to the resonance frequencies is carried out by means of the drive electrode 31 itself, but preferably a separate detection electrode 32 is provided for this purpose, which is located at Figure 4 and 5 Not explicitly shown.

[0057] The resonators 10 , 11 , 12 are preferably designed to be largely identical in terms of structure, so that they form mechanical resonant structures which, in particular within the scope of manufacturing accuracy, have essentially the same natural frequency spectrum or resonance spectrum.

[0058] The elastic suspension of resonators 10, 11, 12 is preferably achieved by the structural design of resonators 10, 11, 12 themselves and their attachment to seismic mass 60 or - alternatively - to anchoring 25 which is fixed relative to substrate 40 (see in particular Fig.15 ).

[0059] The disturbance quantity associated with the resonant frequency of the resonator 10, 11, 12 excited by the resonance is caused by the electrostatic spring softening effect (which is described below for Figure 5 The deflection of the resonator 10 relative to the substrate 40 is related to the gap 50 or the size of the deflection (to be further explained), in particular to a possible deformation of the substrate 40 related to the position of the resonator 10. Since it is difficult to directly measure the deflection, especially for MEMS sensors 100, such as MEMS inertial sensors, MEMS acceleration sensors or MEMS rotational speed sensors, a disturbance variable related to one or more resonance frequencies is capacitively detected. The detected disturbance variable is related to the changing capacitance between the resonator 10, 11, 12 and the electrode assembly 30, in particular the detection electrode 32.

[0060] In the absence of a separate detection electrode 32, the capacitance is detected between the resonator 10 and the drive electrode 31. The change in capacitance can be demodulated accordingly in order to obtain, in particular, a DC current measurement signal representing the interference variable.

[0061] The softening effect of electrostatic springs Figure 5Schematically shown in . If there is a potential difference between the resonator 10, 11, 12 and the electrode assembly 30, surface charges are typically formed on the surfaces of the electrode arrangement 30 and the resonator 10, 11, 12 that are opposite to each other. The surface charges produce an attractive interaction between the electrode assembly 30 and the resonator 10, 11, 12, which interaction is related to a plurality of parameters, such as the local relative distance between the individual resonators 10, 11, 12 and the electrode assembly 30. The force thus generated between the resonator 10, 11, 12 and the electrode assembly 30 is typically a smooth function of the last-mentioned parameter. The relative distance between the resonator 10, 11, 12 and the electrode assembly 30 can be expressed as the sum of the dynamic deflection of the resonator 10, 11, 12 relative to the electrode assembly 30 and the width of the gap 50. With the help of the Taylor expansion with respect to this dynamic deflection, a linear term can be obtained, which is related to the width of the gap 50.

[0062] The motion of each resonator 10, 11, 12 is determined by an equation of motion of the form:

[0063]

[0064] Wherein, m represents the mass of the resonators 10, 11, 12, u represents the dynamic deflection, g represents the width of the gap 50, and k represents the stiffness of the resonator 10 ( The force f is expressed in the usual way as the second derivative of the dynamic deflection u with respect to time. e (u; g) is obtained by the following formula:

[0065]

[0066] Here, ε represents the dielectric constant, V1 represents the voltage applied to the resonators 10, 11, 12, and V2 represents the voltage applied to the electrode assembly 30. e The Taylor expansion of (u; g) with respect to the dynamic deflection u yields:

[0067] f e (u; g) = f (1) (u;g)u+f (2) (u; g)u 2 +f (3) (u; g)u 3 +…, where the coefficient f (1) (u;g),f (2) (u; g) and f (3) (u; g) is determined by Taylor expansion, so that the resonant frequency ω is obtained by the following formula:

[0068]

[0069] Since the coefficient f (1)(u; g) is related to the size of the gap 50, so when the gap width changes, especially when the gap width changes due to mechanical stress and / or deformation of the substrate 40, the resonance frequency ω changes. As a result, the width of the gap 50 can thus be locally scanned with resonators 10 spaced apart from each other in space in order to identify, in particular, deformations of the substrate 40 or of a layer composite having the substrate 40.

[0070] Instead of the embodiment shown in Figure 4 and 5 , the resonators 10, 11, 12 can also be elastically movably suspended on an anchoring part 25 rigidly connected to the substrate (see in particular Fig.15 ). In this case, the resonators 10, 11, 12 do not move with the vibrating mass 60 about the torsional axis 72.

[0071] Figures 6a to 6d exemplarily and schematically show different configurations that can be detected by means of the measurement principle presented here.

[0072] Figure 6a shows the static or ideal configuration in which there is no mechanical stress or deformation. In this case, the dynamic deflection g a of the first resonator 11 b corresponds to the dynamic deflection g a of the second resonator 12, b i.e., g a = g b = g0. For the resonance frequencies ω a of the first and second resonators, b correspondingly ω

[0073] Figure 6b shows an asymmetric deformation of the substrate 40. Accordingly, the dynamic deflection g a of the first resonator 11 is greater than in the rest position (g a > g0), while the dynamic deflection g b of the second resonator 12 is smaller than in the rest position (g b < g0). For the resonance frequencies ω a of the first and second resonators 11, 12, b correspondingly ω a > ω0 or ω b < ω0.

[0074] Figures 6c and 6d show a symmetric deformation of the substrate 40. The dynamic deflection g a of the first resonator 11 corresponds to the dynamic deflection of the second resonator 12, and thus g a = g bIn the example of FIG. 6 c , the dynamic deflection of the resonators 10 , 11 , 12 is greater than in the static position shown in FIG. 6 a , so that g a =g b >g0 or for the resonant frequency ω a =ω b >ω0. FIG. 6d shows a configuration in which the deformation of the substrate 40 leads to a reduction in the gap width, in which case ω applies accordingly. a =ω b＜ ω0.

[0075] Since the resonance frequency ω of the first resonator 11 a and the resonant frequency ω of the second resonator 12 b The change in is proportional to the size of the gap 50, so not only the symmetrical deformation of the substrate 40 but also the asymmetrical deformation thereof can be detected.

[0076] The device 1 for detecting interference variables can be realized by means of conventional processes in the layer composite of the MEMS sensor 100. Here, the aforementioned substrate 40 forms a layer in the layer structure of the MEMS sensor 100. The resonators 10, 11, 12 are spaced apart from each other in the lateral direction in a plane parallel to the main extension plane of the substrate 40 (xy plane).

[0077] Figure 7 , 8 , 9 schematically show possible embodiments of a resonator 10 integrated in a layer complex of a MEMS sensor 100 .

[0078] In the exemplary embodiment shown, the resonator 10 is designed as a beam suspended on one side with a substantially rectangular cross section, which is formed in a layer 110 of the MEMS sensor 100. A oscillatable structural element 15 suspended on one side, in particular a beam, has proven to be advantageous for the resonator 10, since it has an increased stability of the resonance frequency with respect to inherent stresses and process defects.

[0079] The shape of the resonator 10 is predetermined, for example, photolithographically by means of a mask, or—as an alternative—is obtained by exposing holes or trenches that open into the layer 110 , for example by etching.

[0080] Optionally, a stop 111 is provided, in particular at the vibrating free end of the resonator 10, which stop can be produced, for example, by means of a further mask, in order to prevent the resonator 10 from being pulled into the electrode assembly 30. This serves in particular to increase the robustness of the resonator 10 against stress peaks and / or external mechanical influences, such as impacts.

[0081] In the layer 110, the resonator 10 is designed as a substantially beam-shaped structural element 15 with a vibrating free end, which is optionally connected via an intermediate layer 120 to a further layer 130 in which the electrode assembly 30 is formed. The interconnected layers 110, 120, 130 form an anchor for the resonator 10, so that the resonator can be set into vibration by applying a voltage to the drive electrode 31.

[0082] The anchor formed by interconnected layers 110, 120, 130 is, for example, rigidly connected to anchor bolt 20, so that the movement of resonators 10, 11, 12 is decoupled from the movement of seismic mass 60. Alternatively, the anchor formed by interconnected layers 110, 120, 130 may be mounted on anchor bolt 20 as part of seismic mass 60 so that it can be displaced about torsion axis 72.

[0083] Figures 7 to 9 The drive electrode 31 and the detection electrode 32 extend substantially in a plane parallel to a main extension plane of the substrate 40 , ie in particular taking into account production tolerances and in the absence of mechanical deformations and / or mechanical stresses.

[0084] Figures 16 to 19 A further possible embodiment of a resonator 10 integrated in a layer composite of a MEMS sensor 100 is schematically shown, which resonator has an electrode assembly 30 with drive and detection electrodes 31, 32 arranged opposite each other in the z direction. The drive electrode 31 and the detection electrode 32 are arranged opposite each other in two planes extending substantially parallel to the main extension plane. In this case, the resonator 10, 11, 12 is located in the middle region between the drive and detection electrodes 31, 32, so that the resonator is spaced apart from the drive electrode 31 and the detection electrode 32 in the z direction 1000.

[0085] The detection electrode 32 , which is designed as an upper electrode in the exemplary embodiment shown, is attached via a further intermediate layer 140 to the layer 110 in which the resonators 10 , 11 , 12 are formed. Figures 16 to 19 The embodiment of the invention corresponds essentially to the embodiment described above, ie, in particular with the exception of the arrangement and construction of the electrode assembly 30. Figures 7 to 9 The arrangement described is therefore referred to the description related thereto.

[0086] In the configuration, it is provided that the positions of the driving electrodes and the detection electrodes 31, 32 are changed. In particular, it can be provided that relative to Figures 7 to 9 Neutralize and / or Figures 16 to 19 The embodiment shown in FIG. 4 interchanges the positions of the drive and detection electrodes 31 , 32 , so that, for example, the detection electrode 32 is arranged opposite the vibratable free ends of the resonators 10 , 11 , 12 .

[0087] Figures 10 to 14 A MEMS sensor 100 is shown which, in the exemplary embodiment shown, is designed as an out-of-plane MEMS acceleration sensor with an asymmetric rocker and is designed to compensate for systematic measurement deviations. Fig.11 The cutting plane shown in Fig.10 XI is used in the illustration. MEMS sensor 100 shown has a sensor device 90 known per se, which is designed to detect a measurement signal that is dependent on the position of seismic mass 60 relative to sensor housing or substrate 40 .

[0088] In the example shown, movable mass 60 is formed by a layer structure comprising layers 108, 109, 110. The layer structure formed by these layers is arranged rotatably relative to the sensor housing about torsion axis 72. In this case, resonators 10, 11, 12 are introduced into layer 110, so that the movement of resonators 10, 11, 12 is coupled to the movement of seismic mass 60.

[0089] Figures 10 to 14 The exemplary embodiment of has a total of four resonators 10 spaced apart from one another, which can be driven by means of drive electrodes 31. To control the drive electrodes 31, they are connected to the control and evaluation unit 95 via a common drive channel 102 or via separate drive channels 102. Each resonator 10 is assigned a separate detection electrode 32. The resonators 10 are at the same potential, which is achieved by connecting them to the same channel 105.

[0090] In order to detect disturbance variables which are dependent on the resonance frequency of the resonantly excited resonators 10, 11, 12, separate detection channels 101 are provided which are assigned to the respective resonators 10, 11, 12 and are connected to the control and evaluation unit 95. The detected disturbance variables are locally dependent on the size or width of the gap 50 at the location of the resonator 10, 11, 12 and are therefore in particular the size of any deformation or distortion which may occur.

[0091] In order to provide a capacitive measurement signal which is dependent on the position of seismic mass 60, sensor device 90 is connected to control and evaluation unit 95 via further channels 103, 104. These further channels serve to capacitively detect the position of seismic mass 60 and, for this purpose, tap the capacitances of upper and lower electrodes 80a, 80b, 84a, 84b of sensor device 90 in a manner known per se, from which the measurement signal can be derived.

[0092] Control and evaluation unit 95 is designed to compensate for systematic measurement deviations in the measurement signal of sensor device 90 based on the detected disturbance variables.

[0093] The resonators 10 , 11 , 12 of the illustrated exemplary embodiment are arranged in pairs on opposite sides of the torsion axis 72 , in particular in a mirror-symmetrical manner with respect to the torsion axis 72 .

[0094] Fig.12 Shown in perspective Fig.10 MEMS sensors, Fig.13 and 14 Shown in detail Fig.10 The front and back sides of the MEMS sensor have electrical contacts in the form of a detection channel 101, a drive channel 102 and further channels 102, 103. The detection channel 101 is provided for contacting the detection electrode 32 assigned to the resonator 10, 11, 12. Correspondingly, the drive channel 102 is arranged for contacting the drive electrode 31.

[0095] Figures 10 to 14 The configuration of the embodiment of is easy to implement, but measurement errors induced by the movement of the movable mass 60 may occur.

[0096] Fig.15 A further exemplary embodiment is shown in which the movement of resonator 10 is decoupled from the dynamics of seismic mass 60 . For this purpose, resonators 10 , 11 , 12 can be suspended elastically on anchoring 25 which is rigidly connected to anchor bolt 20 , for example.

[0097] In the method for compensating systematic measurement deviations of a MEMS sensor 100, a resonator 10 is resonantly excited by means of an electrode assembly 30 and disturbance variables that are related to the resonant frequency of the resonantly excited resonator 10 are detected capacitively. Systematic measurement deviations in the measurement signal of the sensor device 95 are a measure of the force acting on the movable mass 60, which are compensated analogically or digitally as a function of the detected disturbance variables. The detected disturbance variables are related to the resonant frequency, in particular to the frequency shift of the resonantly vibrating resonator 10, which are linked to the structural properties of the MEMS sensor 100 via the electrostatic spring softening effect. In this way, deformations and distortions of the substrate or the layer complex can therefore be detected in particular, in order to provide a correspondingly compensated output signal that eliminates these disturbance variables.

Claims

1. A MEMS sensor (100), in particular a MEMS acceleration sensor or a MEMS inertial sensor, comprising: - a substrate (40) having a main extension plane; - a seismic mass (60) suspended relative to the substrate (40) so as to be movable in at least one z-direction (1000) perpendicular to the main extension plane; and - a sensor device (90) for detecting a measurement signal related to the position of the seismic mass (60) relative to the substrate (40), It is characterized in that - having at least two resonators (10, 11, 12) which are suspended so as to be elastically movable in the z direction (1000) relative to the substrate; A controllable electrode assembly (30) is designed to resonantly excite each of the at least two resonators (10, 11, 12) to generate a mechanical resonant oscillation and to capacitively detect a disturbance variable associated with at least one resonant frequency of the resonant oscillation.

2. The MEMS sensor (100) according to claim 1, wherein: The at least two resonators (10, 11, 12) are suspended elastically on the seismic mass (60) or elastically on an anchor (25) rigidly connected to the substrate (40).

3. The MEMS sensor (100) according to claim 1 or 2, wherein: The seismic mass (60) is designed as a deflectable, in particular asymmetrical, rocker which is anchored to the substrate (40) via at least one torsion spring (70) so as to be displaceable about a torsion axis (72).

4. The MEMS sensor (100) according to claim 2, wherein: The at least two resonators (10, 11, 12) are arranged at a distance from one another on opposite sides of the torsion axis (72), in particular in a mirror-symmetrical manner with respect to the torsion axis (72).

5. The MEMS sensor (100) according to any one of the preceding claims, wherein: Each resonator (10, 11, 12) is assigned a driving electrode (31) and a detection electrode (32), so that the respectively assigned resonator (10, 11, 12) can be resonantly excited by means of the driving electrode (31) and a disturbance variable related to the resonant frequency of the resonantly excited resonator (10, 11, 12) can be detected by means of the detection electrode (32).

6. The MEMS sensor (100) according to claim 5, wherein: The drive electrode (31) and the detection electrode (32) are arranged in a plane extending substantially parallel to the main extension plane.

7. The MEMS sensor (100) according to claim 5, wherein: The drive electrode (31) and the detection electrode (32) are arranged opposite to each other in two planes extending substantially parallel to the main extension plane, so that the resonator (10, 11, 12) is arranged between the drive electrode (31) and the detection electrode (32) and is spaced apart from the drive electrode (31) and the detection electrode (32) in the z direction (1000).

8. The MEMS sensor (100) according to any one of the preceding claims, wherein: The resonator (10, 11, 12) is designed as a structural element (15) which is elastically suspended on one side or on two sides, in particular substantially in the form of a beam, a finger, a piston or a fork, which extends substantially parallel to the main extension plane.

9. The MEMS sensor (100) according to claim 7 or 8, wherein: At least three, preferably four resonators (10, 11, 12) are provided, which are spaced apart from one another laterally in a plane parallel to the main extension plane in an arrangement different from a co-linear arrangement.

10. The MEMS sensor (100) according to any of the preceding claims has a control and analysis evaluation unit (95), which is configured to control the electrode assembly (30) to resonantly excite the resonator (10, 11, 12) and compensate for systematic measurement deviations in the measurement signal of the sensor device (95) based on detected interference quantities.

11. A method for compensating for systematic measurement deviations of a MEMS sensor (100), the MEMS sensor having a substrate (40) with a main extension plane, a seismic mass (60) suspended relative to the substrate (40) so as to be movable in at least one z-direction (1000) perpendicular to the main extension plane, and a sensor device (90) for detecting a measurement signal which is dependent on the position of the seismic mass (60) relative to the substrate (40), It is characterized in that Resonant excitation is provided for at least two resonators (10, 11, 12) which are suspended elastically in the z direction (1000) relative to the substrate (40) to generate mechanical resonant vibrations, and a disturbance variable associated with the resonant frequency of the resonant vibrations is capacitively detected, wherein systematic measurement deviations in the measurement signal of the sensor device are compensated based on the detected disturbance variable.

12. The method according to claim 11, wherein: The systematic measurement deviation in the measurement signal of the MEMS sensor (100) is compensated analogously or digitally.

13. The method according to claim 11 or 12, wherein: In order to resonantly excite the resonator (10, 11, 12), a pulsed or continuous excitation signal, in particular a harmonic excitation signal or an excitation signal with a time-varying frequency, is applied to the electrode assembly (30), in particular to the drive electrode (31).

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