Sensor structure and gyroscope sensor

Abstract

Sensor structure (1) comprising a substrate (2) having a principal extension plane (100), a first seismic mass (10) and a second seismic mass (20), wherein the first and the second seismic mass (10, 20) are deflectable relative to the substrate (2) along a deflection direction (101) substantially perpendicular to the principal extension plane (100), wherein the first and the second seismic mass (10, 20) are coupled to each other via a rigid coupling rocker (30) pivotable about a rocker axis (31) parallel to the principal extension plane (100), wherein the first seismic mass (10) is suspended from the substrate (2) by means of a first suspension spring (11), characterized in that the sensor structure (1) comprises a substantially rigid first coupling beam (12) which is located between the first suspension spring (11) and the first seismic mass (10) is arranged.

Description

State of the art

[0001] The invention is based on a sensor structure according to the preamble of claim 1.

[0002] Such structures are generally known. For example, German patent DE 10 2009046 506 A1 discloses a gyroscope sensor with Coriolis elements for measuring a gyroscope rate that extends parallel to a principal extension plane of the sensor substrate. Further disclosures are found in patents US 2010 / 0037690 A1, US 2011 / 0132087 A1, US 2011 / 0219875 A1, US 2003 / 0005767 A1, and DE 102009000606 A1. The sensor comprises a first and a second Coriolis element, which are connected to each other via a rigid coupling beam acting as a rocker and two springs, and are excited to oscillate in opposite phases, parallel and antiparallel to an axis of oscillation extending parallel to the principal extension plane. The Coriolis elements are further attached to the substrate via additional spring elements.When the rotation rate is parallel to the principal plane and perpendicular to the axis of oscillation, Coriolis forces act on the first and second Coriolis elements. These forces act perpendicular to the principal plane and deflect the first and second Coriolis elements perpendicular to the principal plane. The rotation rate sensor also incorporates detection means in the form of surface electrodes between the substrate and the Coriolis elements. These surface electrodes overlap the Coriolis elements perpendicular to the principal plane, forming a plate capacitor structure. This structure enables capacitive measurement of the change in distance between the Coriolis elements and the surface electrodes. The deflection of the two Coriolis elements is determined from this measured change in distance, and the rotation rate is then calculated differentially.The use of two separate seismic masses allows for differentiation between applied rotation rate and applied acceleration. Coupling via the rocker arm achieves a common oscillation frequency for both seismic masses, requiring only one drive and detection circuit. This is particularly important because such sensor structures are typically operated resonantly at their respective frequencies. In addition to the desired operating modes, "drive mode" and "detection mode," there are undesirable parallel modes whose frequency differs only slightly from the desired antiparallel operating modes in the prior art. The parallel detection mode, in particular, can lead to large deflections and thus a false signal when externally excited due to resonance amplification. This is generally undesirable due to its susceptibility to interference frequencies.Therefore, embodiments are of interest for application, especially in the automotive sector, in which the parallel mode's frequency is as far above the antiparallel useful mode as possible. Disclosure of the invention

[0003] The sensor structure and the gyroscope according to the dependent claims have the advantage over the prior art that the frequency difference between the desired antiparallel detection modes and the undesired parallel detection modes is increased. This advantageously makes the sensor structure more stable against external interference vibrations. These advantages are achieved by connecting at least the first seismic mass to the substrate via the substantially rigid coupling beam. The coupling beam then acts as a kind of guide rail, suppressing strong deflection of the outer region, i.e., the region facing away from the coupling rocker. A parasitic parallel vibration would cause the coupling beam to bend, so that the parallel detection mode is strongly suppressed in its deflection and shifted to higher frequencies.In particular, the parasitic parallel detection mode is shifted to higher frequencies than the desired antiparallel detection mode. This significantly increases vibration sensitivity compared to the prior art. The at least one first suspension spring is preferably connected directly or indirectly to the substrate. The sensor structure preferably comprises a first and a second detection means, wherein the first detection means particularly preferably comprises a first surface electrode overlapping the first seismic mass in the direction of displacement, and the second detection means comprises a second surface electrode overlapping the second seismic mass in the direction of displacement. The first surface electrode is preferably arranged in a substrate-fixed manner between the substrate and the first seismic mass and forms a plate capacitor with the first seismic mass for capacitive measurement of the displacement of the first seismic mass.Similarly, the second surface electrode is arranged, in particular, in a substrate-fixed manner between the substrate and the second seismic mass and forms a plate capacitor with the second seismic mass for capacitive measurement of the displacement of the second seismic mass. The micromechanical structure according to the invention comprises, in particular, a MEMS (Micro Electro Mechanical System) device manufactured using a semiconductor manufacturing process. The substrate preferably comprises a semiconductor material, in particular silicon, which is structured accordingly to form the first and second movable masses, the coupling rocker, and the at least one coupling element. The structuring is preferably carried out using a lithography, etching, deposition, and / or bonding process.

[0004] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0005] According to a preferred embodiment, the second seismic mass is suspended from the substrate by means of a second suspension spring. The sensor structure comprises a substantially rigid second coupling beam, which is arranged between the second suspension spring and the second seismic mass. When the first and second seismic masses are in a rest position, the second coupling beam is oriented substantially parallel to the first coupling beam. This advantageously achieves effective suppression of the parallel detection mode and, in particular, a shift of the parallel detection mode to higher frequencies, since both the first and second coupling beams must bend during the parallel detection mode. However, the first and second coupling beams are essentially rigid with respect to bending, thus suppressing this vibration mode.

[0006] According to a preferred embodiment, a first end region of the first coupling beam is attached to the first seismic mass, and a second end region of the first coupling beam is attached to the first suspension spring. In a rest position of the seismic mass, the coupling beam extends substantially parallel to the principal extension plane and perpendicular to the rocking axis. Advantageously, the first seismic mass is further suspended from the substrate by the first coupling beam. The first suspension spring is, in particular, attached to a substrate-fixed anchoring. For the purposes of the present invention, the term "rest position" refers specifically to the position of the sensor structure in which the first and second seismic masses are at substantially the same distance from the substrate (i.e., there is no deflection about the rocking axis).

[0007] According to a preferred embodiment, the first coupling beam is designed to be bendable at its first end about a bending axis parallel to the rocking axis relative to the first seismic mass. Advantageously, a slight bending or tilting of the first coupling beam relative to the first seismic mass is possible in the transition region between the first coupling beam and the seismic mass, so that the freedom of movement of the seismic mass along the deflection direction is not excessively restricted. The first coupling beam is preferably significantly narrower than the first seismic mass, parallel to the rocking axis.

[0008] According to a preferred embodiment, a further first end region of the second coupling beam is attached to the second seismic mass, and a further second end region of the second coupling beam is attached to the second suspension spring. Furthermore, it is preferably provided that the second coupling beam is bendable in its further first end region about a further bending axis parallel to the rocking axis relative to the second seismic mass. The second coupling beam is thus preferably symmetrical to the first coupling beam, so that the symmetry of the sensor structure is not disturbed with respect to a plane of symmetry perpendicular to the main extension plane and passing through the rocking axis.

[0009] According to a preferred embodiment, the coupling rocker is connected to the substrate by means of at least one torsion spring extending parallel to the rocker axis, and / or the distance between the second end region and the substrate along the deflection direction is essentially equal to the distance between the further second end region and the substrate. It is also conceivable that the distance between the torsion spring and the substrate is essentially equal to the distance between the second end region and the substrate.Advantageously, the freedom of movement of the first and second seismic masses is thus restricted to an antiparallel rocking motion around the rocking axis, since a parallel movement of the first and second seismic masses along the deflection direction would require bending of the first coupling beam, the second coupling beam and / or the coupling rocker due to the limited available installation space between the suspension springs.

[0010] According to a preferred embodiment, the first seismic mass comprises a first Coriolis element, which can be driven by means of first drive means to a first drive oscillation parallel to the main extension plane and perpendicular to the rocking axis, and the second seismic mass comprises a second Coriolis element, which can be driven by means of second drive means to a second drive oscillation antiparallel to the first drive oscillation. Advantageously, this allows the sensor structure to be operated as a Coriolis sensor.

[0011] According to a preferred embodiment, the first drive means comprises a first drive frame that at least partially encloses the first Coriolis element parallel to the main extension plane, wherein the first drive frame has a first opening for the passage of the first coupling beam and a second opening for the passage of the coupling rocker, and / or wherein the second drive means comprises a second drive frame that at least partially encloses the second Coriolis element parallel to the main extension plane, wherein the second drive frame has a further first opening for the passage of the second coupling beam and a further second opening for the passage of the coupling rocker. This advantageously enables a comparatively compact sensor structure.

[0012] Another object of the present invention is a gyroscope sensor comprising a sensor structure according to the invention. Advantageously, a gyroscope sensor for measuring gyroscope rates about a rotation axis parallel to the rocker axis is thus realized, which exhibits reduced vibration sensitivity compared to the prior art.

[0013] Exemplary embodiments of the present invention are shown in the drawings and explained in more detail in the following description. Brief description of the drawings

[0014] They show Fig. 1a and Fig. 1b a schematic top view and a sectional view of a sensor structure according to a first embodiment of the present invention and Fig. 2a, Fig. 2b and Fig. 2c Schematic perspective views of a sensor structure according to a second embodiment of the present invention. Embodiments of the invention

[0015] In the various figures, identical parts are always marked with the same reference symbols and are therefore usually only named or mentioned once.

[0016] In Fig. 1a and Fig. Figure 1b shows a schematic top view and a sectional view of a sensor structure 1 according to a first embodiment of the present invention. The sensor structure 1 comprises a substrate 2 with a principal extension plane 100, a first seismic mass 10 movable relative to the substrate 2, and a second seismic mass 20 movable relative to the substrate 2. The first and second seismic masses 10 and 20 are each coupled to a common and substantially rigid coupling rocker 30 via connecting springs 32. The coupling rocker 30 is attached to a substrate-fixed substrate anchor 34 by means of torsion springs 33 such that a rocking movement of the coupling rocker 30 about a rocking axis 31 parallel to the principal extension plane 100 is enabled.On one of the torsion rockers 33, along a side facing away from the main extension plane 100, the first seismic mass 10 is connected to a first end region of a substantially rigid first coupling beam 12. A second end region of the first coupling beam 12 is connected to a first suspension spring 11, which engages a further substrate-fixed anchorage 17. Similarly, the sensor structure 1 has a second coupling beam 22, which is attached at a first end region to one of the torsion rockers 33 along a side of the second seismic mass 20 facing away from the main extension plane 100, and at a second end region to a second suspension spring 21. The second suspension spring 21 is attached to a further substrate-fixed anchorage 27. Fig. Figure 1a shows that the extent of the first coupling beam 12, the second coupling beam 22, and the coupling rocker 30 parallel to the rocker axis 31 is less than the extent of the first seismic mass 10 and the second seismic mass 20. From the Fig. Figure 1b shows that the first and second seismic masses 10, 20 move antiparallel along the direction of displacement 101 when the coupling rocker 30 rocks about the rocker axis 31. Preferably, the first and second seismic masses 10, 20 are driven by means of drive means (not shown) to antiparallel drive oscillations along a drive direction 102 that is parallel to the main extension plane 100 and perpendicular to the rocker axis 31. When a rotation rate parallel to the rocker axis 31 is applied to the sensor structure 1, antiparallel Coriolis forces act on the first and second seismic masses 10, 20 along the direction of displacement 101. The first and second seismic masses 10, 20 thus cause the rocking motion about the rocker axis 31 and are deflected along the direction of displacement 101.These deflections are measured by means of a first and a second detection means 40, 41, wherein the first detection means 40 comprises a first surface electrode overlapping the first seismic mass 10 in the deflection direction 101, and the second detection means 41 comprises a second surface electrode overlapping the second seismic mass 20 in the deflection direction 101. The first surface electrode is fixed to the substrate between the substrate 2 and the first seismic mass 10 and forms a plate capacitor with the first seismic mass 10 for the capacitive measurement of the deflection of the first seismic mass 10. Similarly, the second surface electrode 20 is fixed to the substrate between the substrate 2 and the second seismic mass 20 and forms a plate capacitor with the second seismic mass 20 for the capacitive measurement of the deflection of the second seismic mass 20.A differential evaluation of the signals then provides a measure of the displacement of the first and second seismic masses 10, 20 and thus of the applied rotation rate. By guiding the first and second seismic masses 10, 20 via the first and second coupling beams 12, 22, a common and parallel movement of the seismic masses 10, 20 towards or away from substrate 2 is suppressed, since this would require the first and second coupling beams 12, 22 to bend. In other words, the parasitic parallel oscillation of the first and second seismic masses 10, 20 is shifted to higher frequencies and thus moves away from the antiparallel detection oscillation.

[0017] In Fig. 2a, Fig. 2b and Fig. Figures 2c show schematic perspective views of a sensor structure 1 according to a second embodiment of the present invention, wherein the second embodiment is essentially the same as that shown on the basis of Fig. 1a and Fig. The first embodiment is similar to the first embodiment illustrated in Figure 1b, and the first embodiment differs in that it has a first and a second drive frame 14, 24 for driving the drive oscillations along the drive direction 102. The first drive frame 14 is set into an oscillation parallel to the drive direction 102 by means of first comb electrode drives 18 and transmits this oscillation to the first seismic mass 10 by means of springs 19. The first drive frame 14 only partially surrounds the first seismic mass 10, since the first drive frame 14 has a first opening 15 for the passage of the first coupling beam 12 and a second opening 16 for the passage of the coupling rocker 30. Similarly, the second drive frame 24 is set into an oscillation antiparallel to the oscillation of the first drive frame 14 by means of second comb electrode drives 28.The second drive frame 24 transmits this antiparallel oscillation to the second seismic mass 20 by means of further springs 29. The second drive frame 24 also only partially surrounds the second seismic mass 20, since the second drive frame 24 has a further first opening 25 for the passage of the second coupling beam 22 and a further second opening 26 for the passage of the coupling rocker 30. Fig. Figure 2b shows an antiparallel detection oscillation, the so-called useful mode, when a rotation rate is present. It can be seen that the antiparallel displacement of the first and second seismic masses 10, 20 is not impeded by the first and second coupling beams 12, 22. Fig. 2c, on the other hand, shows the unwanted parallel detection motion, the so-called parasitic parallel mode, of the first and second seismic masses 10, 20 along the deflection direction 101. Fig.Figure 2c shows that a bending of the coupling rocker 30, the first coupling beam 12, and / or the second coupling beam 22 is necessary to achieve such a parasitic parallel oscillation. The parallel detection movement is thus strongly suppressed and shifted to high frequencies. Furthermore, by using the separate first and second drive frames 14, 24, a partial decoupling of the drive and detection movements can be achieved, thus reducing coupling from the drive movement to the detection movement.

Claims

[1] Sensor structure (1) comprising a substrate (2) having a principal extension plane (100), a first seismic mass (10) and a second seismic mass (20), wherein the first and the second seismic mass (10, 20) are deflectable relative to the substrate (2) along a deflection direction (101) substantially perpendicular to the principal extension plane (100), wherein the first and the second seismic mass (10, 20) are coupled to each other via a rigid coupling rocker (30) pivotable about a rocker axis (31) parallel to the principal extension plane (100), wherein the first seismic mass (10) is suspended on the substrate (2) by means of a first suspension spring (11), characterized by , that the sensor structure (1) comprises a substantially rigid first coupling beam (12) which is arranged between the first suspension spring (11) and the first seismic mass (10). [2] Sensor structure (1) according to claim 1, wherein the second seismic mass (20) is suspended on the substrate (2) by means of a second suspension spring (21), wherein the sensor structure (1) comprises a substantially rigid second coupling beam (22) which is arranged between the second suspension spring (21) and the second seismic mass (20), wherein the second coupling beam (22) is preferably aligned substantially parallel to the first coupling beam (12) in a rest position of the first and second seismic masses (10, 20). [3] Sensor structure (1) according to one of the preceding claims, wherein a first end region of the first coupling beam (12) is attached to the first seismic mass (10) and a second end region of the first coupling beam (12) is attached to the first suspension spring (11), wherein the coupling beam (12) extends in a rest position of the seismic mass (10) substantially parallel to the main extension plane (100) and perpendicular to the rocking axis (31). [4] Sensor structure (1) according to one of the preceding claims, wherein the first coupling beam (12) is bendable in the first end region about a bending axis parallel to the rocking axis (31) relative to the first seismic mass (12). [5] Sensor structure (1) according to claim 2 or according to one of claims 3 or 4 insofar as it refers back to claim 2, wherein a further first end region of the second coupling beam (22) is attached to the second seismic mass (20) and a further second end region of the second coupling beam (22) is attached to the second suspension spring (21). [6] Sensor structure (1) according to claim 5, wherein the second coupling beam (22) in the further first end region is bendable about a further bending axis parallel to the rocking axis (31) relative to the second seismic mass (22). [7] Sensor structure (1) according to one of the preceding claims, wherein the coupling rocker (30) is connected to the substrate (2) by means of at least one torsion spring extending parallel to the rocker axis (31) and / or wherein, along the deflection direction (101), a distance between the second end region and the substrate (2) is substantially equal to a distance between the further second end region and the substrate (2). [8] Sensor structure (1) according to one of the preceding claims, wherein the first seismic mass (10) comprises a first Coriolis element which can be driven by means of first drive means (13) to a first drive oscillation parallel to the main extension plane (100) and perpendicular to the rocking axis (31), and wherein the second seismic mass (20) comprises a second Coriolis element which can be driven by means of second drive means to a second drive oscillation antiparallel to the first drive oscillation. [9] Sensor structure (1) according to claim 8, wherein the first drive means (13) comprise a first drive frame (14) at least partially enclosing the first Coriolis element parallel to the main extension plane (100), wherein the first drive frame (14) has a first opening (15) for passing the first coupling beam (12) and a second opening (16) for passing the coupling rocker (30), and / or wherein the second drive means (23) comprise a second drive frame (24) at least partially enclosing the second Coriolis element parallel to the main extension plane (100), wherein the second drive frame (24) has a further first opening (25) for passing the second coupling beam (22) and a further second opening (26) for passing the coupling rocker (30). [10] Rotation rate sensor (3) comprising a sensor structure (1) according to one of the preceding claims.

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