Micromechanical structure and method for operating a micromechanical structure

Abstract

Micromechanical structure (1), in particular a rotation rate sensor, with a substrate (2) having a main extension plane (100), a first Coriolis element (3) and a second Coriolis element (4), wherein the first Coriolis element (3) can be driven to a first oscillation (31) along a second direction (Y) parallel to the main extension plane (100) and wherein the second Coriolis element (4) can be driven to a second oscillation (41) antiparallel to the first oscillation (31), wherein a first deflection (35) of the first Coriolis element (3) and a second deflection (45) of the second Coriolis element (4) can each be detected along a first direction (X) parallel to the main extension plane (100) and perpendicular to the second direction (Y), characterized in that the micromechanical structure (1) further comprises a rocker element (5) which is connected both to the first Coriolis element (3),and is coupled directly or indirectly to the second Coriolis element (4), wherein the rocker element (5) has a torsion axis (50) substantially parallel to the second direction (Y), , wherein the torsion axis (50) is arranged along the first direction (X) between the first and second Coriolis elements (3, 4), wherein the first Coriolis element (3) is drivable by means of a first drive frame (30) for the first oscillation (31) and the second Coriolis element (4) is drivable by means of a second drive frame (40) for the second oscillation (41), wherein the first Coriolis element (3) and the first drive frame (30) and / or the second Coriolis element (4) and the second drive frame (40) are each coupled to one another by means of first spring elements (32, 42), wherein the first spring elements (32, 42) are formed softer along the first direction (X) than along the second direction (Y) and / or than along a third direction (Z) perpendicular to the main extension plane (100), wherein the rocker element (5) has a recess (51) in which the first Coriolis element (3), the second Coriolis element (4), the first drive frame (30) and / or the second drive frame (40) are arranged parallel to the main extension plane (100).

Description

State of the art

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

[0002] Such micromechanical structures are generally known. For example, WO 02 / 066 928 A1 discloses a yaw rate sensor comprising a first and a second Coriolis element. The first and second Coriolis elements are arranged above a surface of a substrate, wherein excitation means are provided by which the Coriolis elements can be excited to oscillate parallel to a first axis, and wherein detection means are provided by which a deflection of the Coriolis elements due to a Coriolis force in a second axis, which is perpendicular to the first axis, can be detected. The first and second axes are aligned parallel to the surface of the substrate. This yaw rate sensor thus only enables the detection of a yaw rate perpendicular to the surface of the substrate.Furthermore, another yaw rate sensor is known from the publication US 2008 / 0 078 246 A1, in which a first and a second Coriolis element are connected to a rocker structure. The rocker structure is pivotable about a torsion axis parallel to a substrate surface, wherein the first and second Coriolis elements are excited to oscillate parallel to the substrate surface. A yaw rate oriented parallel to the main extension plane and perpendicular to the oscillation of the Coriolis elements causes a Coriolis force acting perpendicular to the substrate surface on the Coriolis elements, causing the rocker structure to perform a torsional deflection about the torsion axis. This yaw rate sensor thus only enables the detection of a yaw rate parallel to the substrate surface.

[0003] Further micromechanical structures, in particular yaw rate sensors, are known from the document DE 10 2007 012 163 A1. Disclosure of the invention

[0004] The micromechanical structure according to the invention and the method according to the invention for operating a micromechanical structure according to the independent claims have the advantage over the prior art that both the second rotation rate parallel to the main extension plane and the first rotation rate perpendicular to the main extension plane can be measured with the one micromechanical structure. Furthermore, the micromechanical structure is designed to be comparatively compact in terms of installation space, so that wafer area and thus manufacturing costs can be saved in an advantageous manner, and furthermore, a significantly simplified integration of the micromechanical structure can be achieved. These advantages are achieved in that the micromechanical structure has the rocker structure, which is at least indirectly coupled to the first and second Coriolis elements.The second rotation rate causes Coriolis forces acting on the first and second Coriolis elements parallel to the third direction, which are transmitted directly or indirectly to the rocker structure, so that the torsional deflection of the rocker structure is induced as a function of the Coriolis forces parallel to the third direction. Measuring this torsional deflection thus allows the second rotation rate to be determined. At the same time, the first deflection of the first Coriolis element and the second deflection of the second Coriolis element are measured, thereby enabling the first rotation rate to be determined independently of the second rotation rate. Advantageously, the micromechanical structure according to the invention allows, in particular, a fully differential determination of the first rotation rate and a fully differential determination of the second rotation rate, so that a comparatively good signal-to-noise ratio can be achieved in both cases.The micromechanical structure can be manufactured comparatively cost-effectively, particularly using a standard micromechanical manufacturing process, with the substrate preferably comprising a semiconductor substrate, particularly preferably a silicon substrate. Preferably, the micromechanical structure has a further rocker element, which is substantially identical in construction to the rocker element and is arranged parallel to the rocker element.

[0005] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0006] According to one embodiment of the invention, the torsion axis is arranged along the first direction between the first and second Coriolis elements. This preferably results in a comparatively compact design of the micromechanical structure that is essentially mirror-symmetrical relative to a mirror plane running perpendicular to the main extension plane and parallel to the torsion axis.

[0007] According to one embodiment of the invention, it is provided that the first Coriolis element can be driven by means of a first drive frame for the first oscillation and the second Coriolis element can be driven by means of a second drive frame for the second oscillation, wherein the first Coriolis element and the first drive frame and / or the second Coriolis element and the second drive frame are coupled to one another by means of first spring elements, wherein the first spring elements are softer along the first direction than along the second direction and / or along a third direction perpendicular to the main extension plane. The first and second drive frames in conjunction with the first spring elements advantageously ensure decoupling of the drive for the first and second oscillation from the first and second deflection.This results in comparatively efficient first and second comb electrode structures being preferably used to excite the first and second oscillations, wherein fixed electrodes firmly connected to the substrate and counterelectrodes coupled to the first and second Coriolis elements are arranged in an interlocking manner along the second direction, such that the counterelectrodes and the fixed electrodes overlap along the first direction. Advantageously, the counterelectrodes are arranged on the first and second drive frames, respectively, which are coupled to the first and second Coriolis elements in such a way that the first and second drive frames perform essentially no movement along the first direction.Alternatively, the Coriolis forces parallel to the third direction, which are caused by the second rotation rate, act directly on the first and second drive frames, causing the torsional deflection of the rocker element, wherein the first and second Coriolis elements in this case perform essentially no deflection parallel to the third direction. By means of position feedback control (closed-loop operation), the deflection of the drive frame due to a Coriolis force along the third direction is preferably reduced. The first and / or second oscillations are preferably driven by means of a comb drive and / or a plate drive.

[0008] According to a preferred embodiment, it is provided that the rocker element is coupled to the first Coriolis element via the first drive frame and to the second Coriolis element via the second drive frame, wherein second spring elements are preferably arranged between the first drive frame and the rocker element and / or between the second drive frame and the rocker element, which second spring elements are particularly preferably designed to be softer along the second direction than along the first and / or third direction. Advantageously, the second spring elements are designed to be harder with respect to the third direction than with respect to the second direction, so that a movement of the Coriolis elements along the third direction is transmitted to the rocker element due to the second rotation rate, while the first and second oscillations are not transmitted to the rocker element.The rocker element is therefore driven to torsional deflection when the second rotation rate is present.

[0009] According to one embodiment of the invention, the rocker element has a recess in which the first Coriolis element, the second Coriolis element, the first drive frame, and / or the second drive frame are arranged parallel to the main extension plane, advantageously realizing a particularly compact arrangement of the micromechanical structure. The rocker element is preferably attached to the substrate by means of torsion springs and, in the present embodiment, is advantageously not driven to move parallel to the torsion axis or parallel to the torsion springs.

[0010] According to a preferred embodiment, the rocker element is arranged along the first direction between the first and second Coriolis elements, wherein third spring elements are preferably arranged between the first Coriolis element and the rocker structure and / or between the second Coriolis element and the rocker structure, which third spring elements are particularly preferably softer along the first direction than along the second and / or third direction. Advantageously, the first and second Coriolis elements are directly coupled to the rocker structure, wherein the third spring elements only transmit the Coriolis forces to be detected parallel to the third direction to the rocker structure, while Coriolis forces parallel to the first direction essentially do not cause any torsional deflection of the rocker structure.

[0011] According to a preferred embodiment, it is provided that the first deflection is detectable by means of a first detection element and / or that the second deflection is detectable by means of a second detection element, wherein the first detection element is preferably arranged within a first recess in the first Coriolis element and / or the second detection element is arranged within a second recess in the second Coriolis element. The first and the second detection element preferably allow a fully differential evaluation of the first rotation rate, wherein the first and second detection elements particularly preferably comprise a plate capacitor structure embedded in the first and second recesses, respectively. The first and / or second detection elements preferably comprise finger electrode structures, ie interdigital structures.The first and second detection elements are preferably mounted on the first and second Coriolis elements such that the first and second detection elements are movable with respect to movements along the detection direction and rigid with respect to movements along the drive direction.

[0012] According to a preferred embodiment, a torsional deflection of the rocker element about the torsional axis can be detected by means of third detection elements, which are preferably arranged along the third direction between the rocker element and the substrate. The third detection elements preferably comprise surface electrodes and counter-surface electrodes, wherein the counter-surface electrodes preferably comprise opposite end regions of the rocker structure perpendicular to the torsional axis, which cooperate with surface electrodes in the form of a plate capacitor arrangement to detect the torsional deflection. The surface electrodes are arranged in particular on the substrate along the third direction between the counter-surface electrodes and the substrate. The detection of the torsional deflection is determined in particular fully differentially via a change in the electrical capacitance between the surface electrodes and the counter-surface electrodes.Alternatively, the third detection elements comprise a cover electrode, so that the rocker element is arranged between the substrate and the cover electrode along the third direction. Particularly preferably, the third detection elements comprise both the surface electrode and the cover electrode.

[0013] A further subject of the present invention is a method for operating a micromechanical structure, wherein the first deflection of the first Coriolis element and the second deflection of the second Coriolis element are measured to determine a first rotation rate oriented parallel to a third direction perpendicular to the main extension plane, and wherein a torsional deflection of the rocker element about the torsional axis is measured to determine a second rotation rate parallel to the first direction. Advantageously, as already explained in detail above, a determination of both the first and the second rotation rate independently of one another is made possible with only a single micromechanical structure. Preferably, the first and second Coriolis elements are operated in a closed-loop mode (position feedback controlled).

[0014] According to one embodiment of the invention, the first Coriolis element is driven by a first drive frame for the first oscillation, and the second Coriolis element is driven by a second drive frame for the second oscillation. Preferably, the first drive frame is driven by a first comb electrode structure and the second drive frame is driven by a second comb electrode structure, so that a comparatively efficient excitation of the first and second oscillations can be achieved. Alternatively, it is conceivable to drive the first and second oscillations each by means of a plate drive.

[0015] Embodiments of the present invention are illustrated in the drawings and explained in more detail in the following description. Short description of the drawings

[0016] It shows Fig. 1 a schematic plan view of a micromechanical structure according to a first embodiment of the present invention and Fig. 2 a schematic plan view of a micromechanical structure according to a second embodiment of the present invention. Embodiments of the invention

[0017] In Fig. 1 shows a schematic plan view of a micromechanical structure 1 according to a first embodiment of the present invention, wherein the micromechanical structure 1 has a substrate 2 with a main extension plane 100. The micromechanical structure 1 further comprises a first and a second Coriolis element 3, 4, wherein the first and the second Coriolis element 3, 4 are designed to be movable relative to the substrate 2 and are elastically coupled to one another by means of a fourth spring element 6. The first Coriolis element 3 is driven by means of a first drive frame 30 to perform a first oscillation 31 along a second direction Y parallel to the main extension plane 100, wherein the first drive frame 30 is driven by means of a first comb electrode structure 37.The first Coriolis element 3 and the first drive frame 30 are elastically coupled to one another via first spring elements 32, wherein the first spring elements 32 are harder along the second direction Y than along a first direction X perpendicular to the second direction Y and parallel to the main extension plane 100. The second Coriolis element 4 is excited, analogously to the first Coriolis element 3, by means of a second drive frame 40 to a second oscillation 41 along the second direction Y, wherein the second oscillation 41 is antiparallel to the first oscillation 31. The second drive frame 40 is coupled to the second Coriolis element 4 by means of further first spring elements 42 and is driven by means of a second comb electrode structure 47.The micromechanical structure 1 further comprises a rocker element 5, which is fastened to the substrate 2 by means of torsion springs 7, wherein the rocker element 5 is pivotable about a torsion axis 50 defined by the torsion springs 7, which runs parallel to the second direction Y. The torsion springs 7 are fastened to the substrate 2 by means of anchoring elements 7'. The first drive frame 30 is coupled to the rocker structure 5 via second spring elements 33, and the second drive frame 40 is coupled via further second spring elements 43, wherein the second and further second spring elements 33, 43 are designed to be softer along the second direction Y than along a third direction Z perpendicular to the main extension plane 100. The drive movements of the first and second drive frames 30, 40 along the second direction Y are thus not transmitted, or only insignificantly transmitted, to the rocker element 5.When a first rotation rate is present, which has an axis of rotation parallel to the third direction Z, Coriolis forces act on the first and second Coriolis elements 3, 4 along the first direction, wherein the first Coriolis element 3 is deflected to a first deflection 35 along the first direction X due to the first oscillation 31 and the second Coriolis element 4 is deflected to a second deflection 45 antiparallel to the first deflection 35 along the first direction X due to the second oscillation 41. The first deflection 35 can be detected by means of a first detection element 36, which is arranged in a first recess of the first Coriolis element 3 and comprises a first plate capacitor structure, while the second deflection 45 can be detected by means of a second detection element 46, which is arranged in a second recess of the second Coriolis element 4.A differential evaluation of first detection signals from the first detection element 36 and second detection signals from the second detection element 46 thus allows the first rotation rate to be determined. When a second rotation rate is present, which has a rotation axis parallel to the first direction X, further Coriolis forces act on the first and second Coriolis elements 3, 4 along the third direction Z, which are antiparallel to one another due to the antiparallel first and second oscillations 31, 41. This means that one of the first and second Coriolis elements 3, 4 is lowered toward the substrate 2, while the other of the first and second Coriolis elements 3, 4 is raised relative to the substrate 2.These further Coriolis forces are transmitted to the first and second drive frames 30, 40 via the first spring elements 32 and the further first spring elements 42 and are transmitted from the first and second drive frames 30, 40 to the rocker element 5 by means of the second spring elements 33 and the further second spring elements 43. Alternatively, it is conceivable that the further Coriolis forces along the second direction Z act essentially only on the first and second drive frames 30, 40 and are transmitted to the rocker structure 5 via the second spring elements 33 and the further second spring elements 43, wherein the first and second Coriolis elements 3, 4 essentially do not perform any deflections along the third direction Z induced by the further Coriolis forces along the third direction Z.Since the torsion axis 50 runs along the second direction Y between the first and second Coriolis elements 3, 4, a torque about the torsion axis 50 acts on the rocker element 5. The rocker element 5 is thus excited to a torsional deflection 52 about the torsion axis 50 as a function of the second rotation rate. The micromechanical structure 1 has third detection means 53 for capacitively measuring the torsional deflection 52, wherein the third detection means 53 have counter-surface electrodes at the ends of the rocker element 5 opposite each other along the first direction X, which counter-surface electrodes interact with substrate-fixed surface electrodes. The surface electrodes are arranged along the third direction Z between the counter-surface electrodes and the substrate 2.Alternatively, it is conceivable that additional surface electrodes are arranged on a side of the counter-surface electrodes facing away from the substrate 2, so that the counter-surface electrodes are arranged along the third direction Z between the surface electrodes and the additional surface electrodes. Optionally, additional substrate anchors (not shown) are implemented on the first Coriolis element 3, the second Coriolis element 4, the first drive frame 30, the second drive frame 40, and / or the rocker structure 5.

[0018] In Fig. 2 shows a schematic plan view of a micromechanical structure 1 according to a second embodiment of the present invention, wherein the second embodiment essentially corresponds to the one shown in Fig. 1, wherein the first rocker structure 5 does not have a recess 51 in which the first Coriolis element 3, the second Coriolis element 4, the first drive frame 30 and the second drive frame 40 are arranged, but rather the rocker structure 5 is arranged along the first direction X between the first and the second Coriolis element 3, 4. The rocker structure 5 therefore has no direct coupling by means of the second spring elements 33 to the first drive frame 30 and by means of the further second spring elements 43 to the second drive frame 40, but is coupled to the first drive frame 30 only indirectly via the first Coriolis element 3 and to the second drive frame 40 only indirectly via the second Coriolis element 4.For this purpose, a third spring element 34 is arranged between the first Coriolis element 3 and the rocker structure 5, which is softer along the first and / or second direction X, Y than along the third direction Z. Similarly, a further third spring element 44 is formed between the second Coriolis element 4 and the rocker structure 5. When the second rotation rate is present, the rocker structure 5 is now deflected directly by the first and second Coriolis elements 3, 4 via the third and further third spring elements 34, 44 to the torsional deflection 52.

[0019] In a third embodiment (not shown) of the micromechanical structure 1 according to the present invention, which essentially corresponds to the one shown in Fig.2, the first drive frame 30 or the first comb electrode structure 37 are arranged in a further first recess in the first Coriolis element 3 and the second drive frame 40 or the second comb electrode structure 47 are arranged in a further second recess in the second Coriolis element 4. Preferably, the further first recess and the further second recess are each open in the direction of the rocker structure 5, so that the first drive frame 30 is directly coupled to the rocker structure 5 by means of first spring elements 32 and the second drive frame 40 is directly coupled to the rocker structure 5 by means of further first spring elements 42. Alternatively, it is conceivable that the first drive frame 30 is arranged within a recess in the first Coriolis element 3 and that, analogously, the second drive frame 40 is arranged within a recess in the second Coriolis element 4.Other permutations of the arrangements of Coriolis elements, drive frame and rocker structure are also conceivable.

Claims

[1] Micromechanical structure (1), in particular a rotation rate sensor, with a substrate (2) having a main extension plane (100), a first Coriolis element (3) and a second Coriolis element (4), wherein the first Coriolis element (3) can be driven to a first oscillation (31) along a second direction (Y) parallel to the main extension plane (100) and wherein the second Coriolis element (4) can be driven to a second oscillation (41) antiparallel to the first oscillation (31), wherein a first deflection (35) of the first Coriolis element (3) and a second deflection (45) of the second Coriolis element (4) can each be detected along a first direction (X) parallel to the main extension plane (100) and perpendicular to the second direction (Y), characterized bythat the micromechanical structure (1) further comprises a rocker element (5) which is directly or indirectly coupled to both the first Coriolis element (3) and the second Coriolis element (4), wherein the rocker element (5) has a torsion axis (50) substantially parallel to the second direction (Y), wherein the torsion axis (50) is arranged along the first direction (X) between the first and second Coriolis elements (3, 4), wherein the first Coriolis element (3) is drivable by means of a first drive frame (30) for the first oscillation (31) and the second Coriolis element (4) is drivable by means of a second drive frame (40) for the second oscillation (41), wherein the first Coriolis element (3) and the first drive frame (30) and / or the second Coriolis element (4) and the second drive frame (40) are each coupled to one another by means of first spring elements (32, 42), wherein the first spring elements (32, 42) are formed softer along the first direction (X) than along the second direction (Y) and / or than along a third direction (Z) perpendicular to the main extension plane (100), wherein the rocker element (5) has a recess (51) in which the first Coriolis element (3), the second Coriolis element (4), the first drive frame (30) and / or the second drive frame (40) are arranged parallel to the main extension plane (100). [2] Micromechanical structure (1) according to claim 1, characterized byin that the rocker element (5) is coupled to the first Coriolis element (3) via the first drive frame (30) and to the second Coriolis element (4) via the second drive frame (40), wherein second spring elements (33, 43) are preferably arranged between the first drive frame (30) and the rocker element (5) and / or between the second drive frame (40) and the rocker element (5), which spring elements are particularly preferably designed to be softer along the second direction (Y) than along the first and / or third direction (X, Z). [3] Micromechanical structure (1) according to one of the preceding claims, characterized byin that the rocker element (5) is arranged along the first direction (X) between the first and the second Coriolis element (3, 4), wherein preferably between the first Coriolis element (3) and the rocker element (5) and / or between the second Coriolis element (4) and the rocker element (5) third spring elements (34, 44) are arranged, which are particularly preferably designed to be softer along the first direction (X) than along the second and / or third direction (Y, Z). [4] Micromechanical structure (1) according to one of the preceding claims, characterized bythat the first deflection (35) is detectable by means of a first detection element (36) and / or that the second deflection (45) is detectable by means of a second detection element (46), wherein preferably the first detection element (36) is arranged within a first recess in the first Coriolis element (3) and / or the second detection element (46) is arranged within a second recess in the second Coriolis element (4). [5] Micromechanical structure (1) according to one of the preceding claims, characterized by that a torsional deflection (52) of the rocker element (5) about the torsional axis (50) can be detected by means of third detection elements (53), which are preferably arranged along the third direction (Z) between the rocker element (5) and the substrate (2). [6] Method for operating a micromechanical structure (1) according to one of the preceding claims, characterized bythat to determine a first rotation rate, which is aligned parallel to a third direction (Z) perpendicular to the main extension plane (100), the first deflection (35) of the first Coriolis element (3) and the second deflection (45) of the second Coriolis element (4) are measured, and that to determine a second rotation rate parallel to the first direction (X), a torsional deflection (52) of the rocker element (5) about the torsional axis (50) is measured, wherein the torsion axis (50) is arranged along the first direction (X) between the first and second Coriolis elements (3, 4), wherein the first Coriolis element (3) is driven by means of a first drive frame (30) for the first oscillation (31) and the second Coriolis element (4) is driven by means of a second drive frame (40) for the second oscillation (41), wherein the first Coriolis element (3) and the first drive frame (30) and / or the second Coriolis element (4) and the second drive frames (40) are each coupled to one another by means of first spring elements (32, 42), wherein the first spring elements (32, 42) are formed softer along the first direction (X) than along the second direction (Y) and / or than along a third direction (Z) perpendicular to the main extension plane (100), wherein the rocker element (5) has a recess (51) in which the first Coriolis element (3), the second Coriolis element (4), the first drive frame (30) and / or the second drive frame (40) are arranged parallel to the main extension plane (100). [7] Method according to claim 6, characterized by that the first drive frame (30) is driven by means of a first comb electrode structure (37) and the second drive frame (40) is driven by means of a second comb electrode structure (47).

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