DE102022200338A1 - Micromechanical sensor device - Google Patents

Abstract

Micromechanical sensor device (100), comprising:- a first seismic mass element (10); and- a second seismic mass element (20); wherein the two seismic mass elements (10, 20) have different stiffness-to-mass ratios; whereinthe seismic mass elements (10, 20) are fixed to the same anchor elements (1, 2) with spring elements (1a, 1b, 2a, 2b); and wherein an assembly of substrate anchorages of static electrodes (12a...12n) operatively cooperating with electrodes (11a...11n, 21a...21n) of the seismic mass elements (10, 20) are arranged substantially at the same centroid is.

Description

The present invention relates to a micromechanical sensor device. The present invention also relates to a method for producing a micromechanical sensor device. The present invention also relates to a method for operating a micromechanical sensor device.

State of the art

MEMS acceleration sensors have been known for a long time. In such an acceleration sensor, a seismic mass suspended on elastic springs is deflected by an acceleration for a single measuring axis. This deflection is measured capacitively with differentially arranged electrodes, with one capacitance value increasing during the deflection, while another capacitance value decreasing during the deflection.

The acceleration sensors mentioned can be used side by side in a single MEMS chip, e.g. Low-g sensors can be used, for example, to detect the orientation of a display (smartphone), high-g sensors, for example, to detect fast movements.

object of the invention

It is an object of the invention to provide an improved micromechanical sensor device.

• - ein erstes seismisches Massenelement; und
• - ein zweites seismisches Massenelement; wobei die beiden seismischen Massenelemente unterschiedliche Steifigkeits-Masse-Verhältnisse auf-

weisen; wobei
die seismischen Massenelemente mit Federelementen an denselben Ankerelementen fixiert sind; und wobei
eine Gesamtheit von Substratverankerungen von statischen Elektroden, die funktional mit Elektroden der seismischen Massenelemente zusammen- wirken, im Wesentlichen im selben Schwerpunkt angeordnet ist.According to a first aspect, the object is achieved with a micromechanical sensor device, having:

• - a first mass seismic element; and
• - a second seismic mass element; where the two seismic mass elements have different stiffness-to-mass ratios

point; whereby
the seismic mass elements are fixed to the same anchor elements with spring elements; and where
a set of substrate anchorages of static electrodes functionally cooperating with electrodes of the mass seismic elements are arranged substantially in the same center of gravity.

An effect of mechanical stress can advantageously be significantly reduced or eliminated by this proposed structure. A constant offset signal can be easily distinguished from true acceleration because the same elements are involved in these signals. When acceleration is applied, the seismic masses react differently because they have different stiffnesses and masses.

• - Bereitstellen eines ersten seismischen Massenelements; und
• - Bereitstellen eines zweiten seismischen Massenelements; wobei die beiden seismischen Massenelemente unterschiedliche Steifigkeits-Masse-Verhältnisse aufweisen; wobei die seismischen Massenelemente mit Federelementen an denselben Ankerelementen fixiert werden; und wobei

eine Gesamtheit von Substratverankerungen von statischen Elektroden, die funktional mit Elektroden der seismischen Massenelemente zusammen- wirken, im Wesentlichen im selben Schwerpunkt angeordnet wird.According to a second aspect, the object is achieved with a method for producing a micromechanical sensor device, having the steps:

• - providing a first mass seismic element; and
• - providing a second seismic mass element; wherein the two seismic mass elements have different stiffness-to-mass ratios; wherein the seismic mass elements are fixed to the same anchor elements with spring elements; and where

a set of substrate anchorages of static electrodes functionally cooperating with electrodes of the seismic mass elements is arranged substantially in the same center of gravity.

1. a) Generieren von Wertepaaren aus Messwerten, die jeweils mittels eines ersten seismischen Massenelements und eines zweiten seismischen Massenelements gemessen werden, wobei die seismischen Massenelement in unterschiedlichen Messbereichen messen;
2. b) Ermitteln eines Roh-Offset-Signals; und
3. c) Herausrechnen des Roh-Offset-Signals aus den in Schritt a) ermittelten Wertepaaren.

According to a third aspect, the object is achieved with a method for operating a micromechanical sensor device, having the steps:

1. a) Generation of pairs of values from measured values which are each measured by means of a first seismic mass element and a second seismic mass element, the seismic mass elements measuring in different measurement ranges;
2. b) determining a raw offset signal; and
3. c) Calculating the raw offset signal from the pairs of values determined in step a).

According to a fourth aspect, the object is achieved with a computer program product with program code means for carrying out the method for operating a proposed micromechanical sensor device when it runs on an electronic device or is stored on a computer-readable data carrier.

Advantageous developments of the proposed micromechanical sensor device are the subject of the respective dependent claims.

An advantageous further development of the micromechanical sensor device provides that the static electrodes, which are functionally connected to the electric which interact with the seismic mass elements, are arranged close to one another in a defined manner.

A further advantageous development of the micromechanical sensor device provides that the seismic mass elements are each fixed to their own anchor elements, with the substrate anchor points of the anchor elements being arranged close to one another in a defined manner. In this way, different electrical potentials can be applied to the seismic masses. Furthermore, the same static electrodes can also be used in this variant for reading out the electrical signals.

A further advantageous development of the micromechanical sensor device provides that one of the seismic mass elements encloses the other of the seismic mass elements in a ring shape.

A further development of the micromechanical sensor device provides that the seismic mass elements are C-shaped and engage in one another in a detection plane.

Further advantageous developments of the micromechanical sensor device provide that the sensor device is an in-plane sensor device or an out-of-plane sensor device.

A further development of the micromechanical sensor device provides that the first seismic mass element is used for a high-g sensor and the second seismic mass element is used for a low-g sensor.

The invention is described in detail below with further features and advantages on the basis of several figures. Elements that are the same or have the same function have the same reference numbers therein. The figures are intended in particular to clarify the principles that are essential to the invention and do not necessarily have to be drawn to scale for this purpose.

Device features disclosed result analogously from corresponding disclosed method features and vice versa. This means in particular that features, technical advantages and technical advantages relating to the proposed micromechanical sensor device result from corresponding versions, features and technical advantages relating to the method for producing a proposed micromechanical sensor device and from corresponding embodiments, features and technical advantages relating to the method for operating a proposed micromechanical sensor device result and vice versa.

• 1 eine herkömmliche mikromechanische Sensoreinrichtung;
• 2 eine erste Ausführungsform einer vorgeschlagenen mikromechanischen Sensoreinrichtung;
• 3 die vorgeschlagenen mikromechanischen Sensorvorrichtung von Figur zu zwei bei einer Auslenkung;
• 4 eine weitere Ausführungsform einer vorgeschlagenen mikromechanischen Sensoreinrichtung;
• 5 ein Auslenkungsdiagramm, das ein Wirkprinzip des vorgeschlagenen Verfahrens erläutert;
• 6 ein prinzipielles Ablaufdiagramm eines vorgeschlagenen Verfahrens zum Herstellen einer vorgeschlagenen mikromechanischen Sensoreinrichtung; und
• 7 ein Ablaufdiagramm eines Verfahrens zum Betreiben einer vorgeschlagenen mikromechanischen Sensoreinrichtung.

In the figures shows:

• 1 a conventional micromechanical sensor device;
• 2 a first embodiment of a proposed micromechanical sensor device;
• 3 the proposed micromechanical sensor device from Figure to two in a deflection;
• 4 a further embodiment of a proposed micromechanical sensor device;
• 5 a deflection diagram that explains an operating principle of the proposed method;
• 6 a basic flowchart of a proposed method for producing a proposed micromechanical sensor device; and
• 7 a flowchart of a method for operating a proposed micromechanical sensor device.

Description of Embodiments

Due to mechanical stress (e.g. housing stress, temperature stress, intrinsic layer stress, etc.), seismic mass elements of a micromechanical sensor device can be deflected without applied acceleration, resulting in a so-called constant offset, which results in an undesired stress. In principle, in order to calibrate this constant offset, the total acceleration of the micromechanical sensor for each sensing axis must be known. A difference to this predefined acceleration is the named constant offset. This typically occurs during a final check of the sensor in a manufacturing process.

The mentioned constant offset can change in the course of the lifetime of the sensor. A problem with recalibrating the constant offset at the customer's site can be that there is no clearly defined acceleration. The orientation of the sensor in three-dimensional space is typically not known and the 1g gravity of the earth is randomly distributed over all three sensing axes of the accelerometer.

1 FIG. 1 shows a plan view of a conventional micromechanical sensor device 100 in the form of an acceleration sensor. A first seismic mass element 10 can be seen, which is anchored to two anchor elements 1, 2 with spring elements 1a, 2a. You can also see electro 11a...11f, which are arranged on the first seismic mass element 10, which functionally interact with static electrodes 12a...12n arranged on the substrate (not shown) in order to thereby generate an electrical voltage.

A second seismic mass element 20 is arranged to the side of the first seismic mass element 10, which is anchored to the substrate via two anchor elements 3, 4 with spring elements 3a, 4a and which functionally interact with static electrodes 22a...22n anchored to the substrate. As a result, in the event of mechanical stress on the substrate, an electrical offset voltage is generated in this way, which causes an incorrect electrical signal and impairs the operating behavior of micromechanical sensor device 100 .

It is proposed to provide a combined MEMS accelerometer with at least two different stiffness-to-mass ratios (e.g. high-g, low-g) to calibrate the offset of both accelerometers during operation. Both sensors are connected to the same anchoring points on the substrate, so that their stress-induced deflection relative to sensor electrodes is very similar.

An implementation of the principle explained above is proposed, which is 2 is shown in a top view of a first specific embodiment of micromechanical sensor device 100 .

It can be seen that the two seismic mass elements 10, 20 are each anchored to the same anchor element 1, 2 with spring elements 1a, 1b or 2a, 2b. Furthermore, it can be seen that the electrodes 11a...11n, 21a...21n of the seismic mass elements 10, 20 interact with the same static electrodes 12a...12n anchored on the substrate. As a result, the configuration is such that a center of gravity of a total of the static electrodes 12a . . . 12n in the detection direction (x-direction) of the seismic mass elements 10, 20 or the electrodes is essentially identical. The static electrodes, which functionally interact with the electrodes (11a...11n, 21a...21n) of the seismic mass elements (10, 20), are arranged close to one another in a defined manner, preferably only a few μm.

As a result, stress acting from outside acts in the same way on the two seismic mass elements 10, 20 and on the static electrodes 12a...12n, as a result of which an electrical offset signal, which is generated thereby, has a simple effect can be calculated from a measurement signal. An operating behavior of the micromechanical sensor device 100 designed in this way can advantageously be significantly improved. The embodiment of 2 shows an in-plane acceleration sensor with two seismic mass elements 10, 20.

In contrast, a "real" acceleration causes a difference in the deflection of the two sensors, depending on the respective stiffness-to-mass ratio of the sensor. An algorithm can be used to distinguish the real acceleration from the constant offset, or to calculate the constant offset from the measurement signal.

A significant contribution to the stress-induced deflection of (e.g. in-plane) accelerometers is the relative displacement of the anchoring points of the seismic mass elements compared to the static measuring electrodes. The seismic mass elements of acceleration sensors are typically anchored to the subsoil by means of springs with anchoring points.

It is proposed to connect two separate seismic mass elements to the subsoil (e.g. substrate) at the same anchoring points using spring elements. Due to the stress, these anchor points are displaced relative to their sensor electrodes. This corresponds to a static pre-deflection of each of the two seismic mass elements and leads to a constant offset in both measurement channels.

If, on the other hand, an external excitation, e.g. in the form of an acceleration, acts on this structure, the two seismic mass elements 10, 20 are deflected differently. If the stiffness-to-mass ratio of one seismic mass element is significantly higher (e.g. high-g sensor) than another seismic mass element, the deflection will be significantly less.

In other words, any deflection caused by mechanical stress results in an equal change in a gap distance between electrodes, whereas any deflection caused by acceleration results in gap distance changes according to the relative stiffness-to-mass ratios of the two seismic mass elements.

In a very compact arrangement, it may be advantageous to form a low-g mass element as a ring enclosing the anchor elements and the high-g element (not shown).

3 shows a proposed micromechanical sensor device 100 in action, with an acceleration in direction R a relative movement A of the sensor electrode 11c with the stati rule electrode 12e is indicated. This relative movement A affects all electrodes of the seismic mass element 10, 20 or all static electrodes 12a...12n.

In order to provide a sensor device 100 with a high sensing capacity, it can be advantageous to "electrically split" the two seismic mass elements 10, 20, for example by separating the anchor elements 1, 2 into two electrically separate but locally close anchor elements, as in 4 shown. With such a configuration, the movement of the two mass elements 10, 20 can be detected with the same static electrodes, a very compact design of the sensor device 100 also being advantageously supported in this way.

This embodiment of the proposed micromechanical sensor device 100 is distinguished by a “very dense detection structure”. It can be seen that in this variant the seismic mass elements 10, 20 are each again anchored to an anchor element 1, 2 or 3 and 4 with spring elements 1a, 2a or 3a, 4b.

The two anchor elements 1...4 are arranged so close together that a common center of gravity of the static electrodes 12a...12n in the detection plane (xy plane) is essentially identical, so that external stress (e.g. due to mechanical or thermal bending, etc.) also similar to the before the variant of 1 acts immediately. As a result, a constant offset voltage generated due to external stress can also be easily calculated from the measurement signal in this variant.

The variant of the embodiment of 4 also advantageously allows the seismic mass elements 10, 20 to be subjected to different electrical potentials after the anchor elements 1 and 3 or 2 and 4 are electrically isolated from one another.

Other embodiments that are not shown can provide, for example, for the seismic mass elements 10, 20 to be U-shaped or C-shaped and to intermesh in a detection plane (x-y plane). Further specific embodiments not shown in the figures provide that it is not an out-of-plane acceleration sensor that has, for example, a seesaw structure or an out-of-plane plate structure.

5 12 is a diagram showing a relationship between external acceleration B and displacement D of the seismic mass elements 10, 20 in response thereto. The constant stress displacement is similar for both mass elements 10,20. The way in which an algorithm works is recognizable, with which the undesired electrical offset voltage can be calculated out of an electrical measurement signal. It can be seen that a deflection is different due to the two different seismic mass elements 10, 20, with the first mass element 10 with the greater mass or the greater stiffness-to-mass ratio being deflected less (curve V1) and the second seismic mass element 20 with the smaller one Mass or the smaller stiffness-to-mass ratio is further deflected (curve V2).

In both cases, the result is a constant deflection OF, i.e. a deflection caused by stress, which can easily be calculated from a measurement signal.

It is also conceivable, as an application, to apply different test signals in order to determine a sensitivity of the micromechanical sensor device 100 .

The proposed micromechanical sensor device 100 can advantageously be used for all MEMS sensor concepts in which the sensor technology is based on the deflection relative to sensor elements (e.g. acceleration sensors, gyroscopes, pressure sensors, etc.).

6 shows a basic sequence of a proposed method for producing a proposed micromechanical sensor device 100.

In step 200, a first seismic mass element 10 is provided.

In a step 210, a second seismic mass element 20 is provided, with the two seismic mass elements 10, 20 measuring in different measurement ranges, with the seismic mass elements 10, 20 being fixed to the same anchor elements 1, 2 with spring elements 1a, 1b, 2a, 2b , and wherein a whole of substrate anchorages of static electrodes 12a...12n operatively cooperating with electrodes 11a...11n, 21a...21n of the seismic mass elements 10, 20 are arranged substantially in the same centroid.

7 shows a basic sequence of a method for operating a proposed micromechanical sensor device 100.

In a step 300, pairs of values are generated from measured values which are each measured by means of a first seismic mass element 10 and a second seismic mass element 20, with the seismic mass elements 10, 20 measuring in different measurement ranges.

In a step 310, a raw offset signal is determined.

In a step 320, the raw offset signal is calculated from the pairs of values determined in step a).

The procedure according to 7 can be embodied, for example, as a computer program product with program code means for carrying out the method if it runs on an electronic device (eg ASIC of the sensor device 100) or is stored on a computer-readable data carrier.

Although the proposed micromechanical sensor device is disclosed as an in-plane sensor device above, the sensor device can also be implemented as an out-of-plane sensor device, e.g. with a rocker structure or with a plate-shaped out-of-plane sensing element.

Although the invention has been described above on the basis of specific exemplary embodiments, the person skilled in the art can also implement embodiments that are not disclosed or only partially disclosed without departing from the core of the invention.

Claims (10)

Micromechanical sensor device (100), comprising: - a first seismic mass element (10); and - a second seismic mass element (20); wherein the two seismic mass elements (10, 20) have different stiffness-to-mass ratios; wherein the seismic mass elements (10, 20) are fixed to the same anchor elements (1, 2) with spring elements (1a, 1b, 2a, 2b); and wherein an assembly of substrate anchorages of static electrodes (12a...12n) operatively cooperating with electrodes (11a...11n, 21a...21n) of the seismic mass elements (10, 20) are arranged substantially at the same centroid is. Micromechanical sensor device (100) after claim 1 , characterized in that the static electrodes (12a... 12n) which functionally interact with the electrodes (11a... 11n, 21a...21n) of the seismic mass elements (10, 20) are arranged close to one another in a defined manner. Micromechanical sensor device (100) after claim 1 or 2 , characterized in that the seismic mass elements (10, 20) are each fixed to their own anchor elements (1...4), the substrate anchoring points of the anchor elements (1...4) being arranged close to one another in a defined manner. Micromechanical sensor device (100) according to one of the preceding claims, characterized in that one of the seismic mass elements (10, 20) encloses the other of the seismic mass elements (10, 20) in a ring shape. Micromechanical sensor device (100) according to one of Claims 1 until 3 , characterized in that the seismic mass elements (10, 20) are C-shaped and in a detection plane (x, y) interlock. Micromechanical sensor device (100) according to one of the preceding claims, characterized in that the sensor device (100) is an in-plane sensor device or an out-of-plane sensor device. Micromechanical sensor device (100) according to one of the preceding claims, wherein the first seismic mass element (10) is used for a high-g sensor and wherein the second seismic mass element (10) is used for a low-g sensor. Method for producing a micromechanical sensor device (100) having the steps: - Providing a first seismic mass element (10); and - providing a second seismic mass element (20); wherein the two seismic mass elements (10, 20) measure in different measurement ranges; wherein the seismic mass elements (10, 20) are fixed to the same anchor elements (1, 2) with spring elements (1a, 1b, 2a, 2b); and wherein an assembly of substrate anchorages of static electrodes (12a...12n) operatively cooperating with electrodes (11a...11n, 21a...21n) of the seismic mass elements (10, 20) are arranged substantially at the same centroid becomes. Method for operating a micromechanical sensor device (100), comprising the steps: a) generating pairs of values from measured values, each of which is determined by means of a first seismic mas senelements and a second seismic mass element are measured, wherein the seismic mass element measure in different measurement ranges; b) determining a raw offset signal; and c) calculating the raw offset from the pairs of values determined in step a). Computer program product with program code means for carrying out the method claim 9 when running on an electronic device or stored on a computer-readable medium.

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