MEMS gyroscope with improved quadrature error rejection

Abstract

The present disclosure relates to a MEMS gyroscope with improved quadrature error rejection. The MEMS gyroscope is formed by a substrate, a first mass and a second mass, wherein the first mass and the second mass are suspended above the substrate and in a rest state extend in an extension plane defining a first direction and a second direction transverse to the first direction. The MEMS gyroscope further has a drive structure coupled to the first mass and configured to, in use, move the first mass in the first direction, and an elastic coupling structure extending between the first mass and the second mass and configured to couple movement of the first mass in the first direction with movement of the second mass in the second direction. The elastic coupling structure has a first portion having a first stiffness and a second portion having a second stiffness greater than the first stiffness.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a MEMS (Micro-Electro-Mechanical System) gyroscope, which has improved quadrature error rejection with respect to yaw movements, in particular. BACKGROUND

[0002] As known, gyros obtained with MEMS technology are formed in a die of semiconductor material (for example, silicon) and comprise at least one or more moving masses suspended above a substrate and free to oscillate with respect to the substrate with one or more degrees of freedom.

[0003] The moving mass is capacitively coupled to the substrate by means of a drive electrode, configured to make the moving mass oscillate in a drive direction, and a detection electrode, configured to detect the displacement of the moving mass in a detection direction.

[0004] When the MEMS gyroscope is rotated around an axis of rotation with an angular velocity, the moving mass, which oscillates with a linear velocity in a direction perpendicular to the axis of rotation, is subjected to a Coriolis force, which is directed in a direction perpendicular to the axis of rotation and to the direction of the linear velocity.

[0005] In particular, MEMS gyros of the single-axis, dual-axis or tri-axis type are known, which are configured to detect a yaw movement associated with a yaw angular velocity of the MEMS gyroscope around an axis perpendicular to the plane of extension of the moving mass.

[0006] In this regard, MEMS gyros with two detection masses are known. These comprise a first moving mass, a second moving mass and an elastic element coupling the first moving mass with the second moving mass. The first moving mass is kept oscillating in a drive direction by means of a drive electrode, the drive direction lying in the plane of extension of the first and second moving masses. The elastic element is configured to transform the oscillation of the first moving mass into an oscillation of the second moving mass in a sense direction, the sense direction lying in the plane of extension of the first and second moving masses and being perpendicular to the drive direction. Therefore, when the MEMS gyroscope is subjected to a yaw angular velocity, the second moving mass is affected by a Coriolis force in a direction perpendicular to the sense direction (and parallel to the drive direction). A detection electrode is configured to detect the yaw movement of the second moving mass and to generate a corresponding detection signal.

[0007] A key parameter to determine the performance of a MEMS gyroscope is the stability of the detection signal in the absence of rotation (zero rate output, ZRO). In other words, it is desirable that, in the absence of rotation of the MEMS gyroscope, when the first moving mass is actuated in the drive direction, the movement of the second moving mass does not generate any variation in the detection signal.

[0008] However, in known MEMS gyroscopes, the elastic coupling element has an asymmetry due to process variability associated with the manufacturing of the elastic coupling element between the first moving mass and the second moving mass. This means that the sense direction also comprises an orthogonal component parallel to the drive direction (and perpendicular to the sense direction). Thus, even in the absence of rotation of the MEMS gyroscope, the orthogonal component generates a variation of the detection signal, also called orthogonal error.

[0009] A method to reduce the asymmetry of the elastic coupling element envisages, during the process of manufacturing the MEMS gyroscope, the use of a dedicated lithography machine and / or mask, which enables to reduce the process variability.

[0010] However, this method requires an increase in the cost and time of manufacturing the MEMS gyroscope.

[0011] According to another method, an additional electrode configured to compensate the orthogonal error is also integrated in the MEMS gyroscope.

[0012] However, the additional electrode can increase the footprint of the die and requires an additional manufacturing step. Thus, this method also increases the difficulty of the MEMS gyroscope and the manufacturing time and cost.

[0013] Moreover, the orthogonal compensation electrode makes the design of the control circuit of the MEMS gyroscope more complex. SUMMARY

[0014] The present disclosure aims to overcome the drawbacks of the known art.

[0015] In at least one embodiment, a MEMS gyroscope comprises: a substrate; a first mass and a second mass, the first mass and the second mass being suspended above the substrate and extending in a rest state in an extension plane, the extension plane defining a first direction and a second direction transverse to the first direction; a drive structure coupled to the first mass and configured to move, in use, the first mass in the first direction; and an elastic coupling structure extending between the first mass and the second mass and configured to couple the movement of the first mass in the first direction with the movement of the second mass in the second direction, wherein the elastic coupling structure comprises a first portion having a first stiffness and a second portion having a second stiffness, the second stiffness being greater than the first stiffness. BRIEF DESCRIPTION OF DRAWINGS

[0016] For a better understanding of the present disclosure, reference will now be made, purely by way of non-limiting example, to the accompanying drawings, wherein:

[0017] Figure 1 a top view of the present MEMS gyroscope is shown according to one embodiment;

[0018] Figure 2 a top view of a portion of the MEMS gyroscope in use is shown; Figure 1

[0019] Figure 3 a top view of the present MEMS gyroscope is shown according to different embodiments;

[0020] Figure 4 a top view of the present MEMS gyroscope is shown according to another embodiment; and

[0021] Figure 5 a block diagram of an electronic device incorporating the present MEMS gyroscope is shown. DETAILED DESCRIPTION

[0022] Figure 1 A MEMS gyroscope 1 of the single-axis type is shown in a Cartesian reference system XYZ comprising a first axis X, a second axis Y and a third axis Z.

[0023] The MEMS gyroscope 1 is obtained in a die of a semiconductor material, for example silicon, and comprises a substrate 5 and a first mobile mass 7 and a second mobile mass 10 suspended above the substrate 5.

[0024] The first mobile mass 7 and the second mobile mass 10 are substantially planar, mainly extending in the plane XY and here have an approximately rectangular shape.

[0025] The first mobile mass 7 and the second mobile mass 10 are coupled to a first anchoring region 13A and to a second anchoring region 13B, respectively, by means of a first elastic connection (flexure) 15A and a second elastic connection (flexure) 15B, the first anchoring region 13A and the second anchoring region 13B being fixed to the substrate 5.

[0026] The first flexures 15A each extend between the first mobile mass 7 and the respective first anchoring region 13A, here in a direction parallel to the first axis X.

[0027] The second flexures 15B each extend between the second mobile mass 10 and the respective second anchoring region 13B, here in a direction parallel to the second axis Y.

[0028] ​Furthermore, in this embodiment, the first moving mass 7 and the second moving mass 10 are also coupled to the central anchoring region 20 via a respective first flexure 15A and a respective second flexure 15B, the central anchoring region 20 being fixed to the substrate 5.

[0029] The first flexure 15A and the second flexure 15B can be linear or folded elastic elements and are configured in a manner known per se so as to enable the first moving mass 7 and the second moving mass 10 to move with one or more degrees of freedom, respectively.

[0030] In detail, in this embodiment, the first flexure 15A and the second flexure 15B enable the first moving mass 7 and the second moving mass 10 to move along a first axis X and a second axis Y, respectively.

[0031] The MEMS gyroscope 1 comprises an elastic coupling structure 25 extending between and coupling together the first moving mass 7 and the second moving mass 10.

[0032] The coupling structure 25 is formed by a rigid portion 26, a peripheral flexible portion 27 and a central flexible portion 28.

[0033] The rigidity of the rigid portion 26 is greater than the rigidity of the peripheral flexible portion 27 and of the central flexible portion 28, for example by a factor of 10 to 100.

[0034] The peripheral flexible portion 27 comprises a first arm 30 extending from the first moving mass 7 in a direction parallel to the first axis X and a second arm 31 extending from the second moving mass 10 in a direction parallel to the second axis Y.

[0035] The rigid portion 26 comprises a first connecting arm 33 and a second connecting arm 34 each extending between a respective first end 38 coupled to the peripheral flexible portion 27 and a respective second end 39 coupled to the central flexible portion 28.

[0036] In detail, the first ends 38 of the first connecting arm 33 and of the second connecting arm 34 are coupled to the end portions of the first arm 30 and of the second arm 31 of the peripheral flexible portion 27, respectively.

[0037] The first connecting arm 33 and the second connecting arm 34 extend from the respective first ends 38 in a direction parallel to the tilt direction C (here represented by a dashed line) in a plane XY transverse to the first axis X and to the second axis Y, forming an angle a with respect to the first axis X, here an angle of 45°.

[0038] The first arm 30 and the second arm 31 of the outer flexible portion 27 have smaller dimensions than the first connecting arm 33 and the second connecting arm 34, thereby having greater flexibility than the first connecting arm 33 and the second connecting arm 34.

[0039] In detail, in this embodiment, the first arm 30 and the second arm 31 of the peripheral flexible portion 27 each have a corresponding width measured in a direction parallel to the second axis Y and in a direction parallel to the first axis X, respectively. This width is smaller than the width measured in the plane XY in the direction C′ (by...). Figure 1 The width of the first connecting arm 33 and the second connecting arm 34 is measured in a parallel direction (represented by the dotted line in the figure), and the direction C′ is perpendicular to the tilt direction C.

[0040] For example, the width of the first arm 30 and the second arm 31 of the peripheral flexible portion 27 can be included between one-hundredth and one-tenth of the width of the first connecting arm 33 and the second connecting arm 34.

[0041] Furthermore, in this embodiment, the first arm 30 and the second arm 31 of the peripheral flexible portion 27 each have a corresponding length measured in a direction parallel to the first axis X and in a direction parallel to the second axis Y, respectively, which is less than the length of the first connecting arm 33 and the second connecting arm 34 measured in a direction parallel to the tilt direction C.

[0042] For example, the lengths of the first arm 30 and the second arm 31 of the peripheral flexible portion 27 can be included between one-hundredth and one-tenth of the lengths of the first connecting arm 33 and the second connecting arm 34.

[0043] In this embodiment, the thickness of the first arm 30 and the second arm 31 of the peripheral flexible portion 27 along the third axis Z is equal to the thickness of the first connecting arm 33 and the second connecting arm 34.

[0044] However, the thickness of the first arm 30 and / or the second arm 31 of the peripheral flexible portion 27 may also be different from the thickness of the first connecting arm 33 and / or the second connecting arm 34.

[0045] The central flexible portion 28 includes a first arm 36 and a second arm 37 coupled together at the joint end 40. For example, as... Figure 1 As shown, the first arm 36 and the second arm 37 meet at the joint end 40, such that the central flexible portion 28 has a V-shape, and the V-shaped joint end 40 extends inward toward the central anchoring region, as... Figure 1 As shown.

[0046] The first arm 36 of the central flexible portion 28 extends between the engaging end 40 and the second end 39 of the first connecting arm 33 in a direction parallel to the first axis X.

[0047] The second arm 37 of the central flexible portion 28 extends between the junction end 40 and the second end 39 of the second connecting arm 34 in a direction parallel to the second axis Y.

[0048] The first arm 36 and the second arm 37 of the central flexible portion 28 have a smaller size than the first connecting arm 33 and the second connecting arm 34, so as to have a greater flexibility than the first connecting arm 33 and the second connecting arm 34.

[0049] In detail, in this embodiment, the first arm 36 of the central flexible portion 28 and the second arm 37 of the central flexible portion 28 each have a respective width measured parallel to the second axis Y and parallel to the first axis X, respectively, which is smaller than the width of the first connecting arm 33 and of the second connecting arm 34 measured in the plane XY parallel to the direction C’.

[0050] For example, the width of the first arm 36 and of the second arm 37 of the central flexible portion 28 can be comprised between one and ten percent of the width of the first connecting arm 33 and of the second connecting arm 34.

[0051] Moreover, in this embodiment, the first arm 36 of the central flexible portion 28 and the second arm 37 of the central flexible portion 28 each have a respective length measured parallel to the first axis X and parallel to the second axis Y, respectively, which is smaller than the length of the first connecting arm 33 and of the second connecting arm 34 measured parallel to the oblique direction C.

[0052] For example, the length of the first arm 36 and of the second arm 37 of the central flexible portion 28 can be comprised between one and ten percent of the length of the first connecting arm 33 and of the second connecting arm 34.

[0053] In this embodiment, the first arm 36 and the second arm 37 of the central flexible portion 28 have a thickness along the third axis Z equal to the thickness of the first connecting arm 33 and of the second connecting arm 34.

[0054] However, the thickness of the first arm 36 and / or of the second arm 37 of the central flexible portion 28 can also be different from the thickness of the first connecting arm 33 and / or of the second connecting arm 34.

[0055] The MEMS gyroscope 1 further comprises a drive structure 45 (of the capacitive type, and coupled to the first mobile mass 7) and a detection structure 46 (of the capacitive type, and coupled to the second mobile mass 10).

[0056] The drive structure 45 comprises a fixed electrode 48 fixed to the substrate 5, and a mobile electrode 49 integrated with respect to the first mobile mass 7.

[0057] In this embodiment, the drive structure 45 is a comb drive. In detail, the moving electrodes 49 comprise a plurality of protrusions 50 extending from the first moving mass 7 parallel to the first axis X, and the fixed electrodes 48 comprise a plurality of protrusions 51 extending parallel to the first axis X and crossing with respect to the protrusions 50 of the moving electrodes 49.

[0058] However, the drive structure 45 can have a shape different from Figure 1 the one illustrated. For example, the number, shape and arrangement of the fixed electrodes 48 and of the moving electrodes 49 can vary. Additionally or as an alternative, the drive structure 45 can be a parallel plate capacitor.

[0059] The detection structure 46 is configured to detect a yaw movement of the second moving mass 10 parallel to the first axis X, and to generate a corresponding yaw output signal.

[0060] In detail, the detection structure 46 comprises fixed electrodes 54 fixed to the substrate 5, and moving electrodes 55 integrated with respect to the second moving mass 10.

[0061] In this embodiment, the detection structure 46 is a capacitor having a parallel plate structure. In detail, the moving electrodes 55 comprise a plurality of protrusions 56 extending from the second moving mass 10 parallel to the second axis Y, and the fixed electrodes 54 comprise a plurality of fixed portions 57 extending parallel to the second axis Y, each fixed portion 57 being at a distance from a corresponding protrusion 56 along the first axis X.

[0062] However, the detection structure 46 can have a shape different from Figure 1 the one illustrated. For example, the number, shape and arrangement of the fixed electrodes 54 and of the moving electrodes 55 can vary. Additionally or as an alternative, the detection structure 46 can be a comb drive.

[0063] The MEMS gyroscope 1 further comprises drive contact pads 60 and detection contact pads 62 electrically coupled to the drive structure 45 and to the detection structure 46, respectively, through respective connection tracks (not illustrated here).

[0064] The drive contact pads 60 and the detection contact pads 62 enable the MEMS gyroscope 1 to be coupled to an external control circuit (not illustrated here). The external control circuit can be obtained in the same die as the MEMS gyroscope 1 or in a separate die.

[0065] In use, a drive voltage is applied to the drive structure 45. The drive voltage causes the first moving mass 7 to move in a main drive direction M p X parallel to the first axis X, for example oscillating at a resonance frequency of the MEMS gyroscope 1. By way of example, Figure 2A simplified and enlarged detail of the MEMS gyroscope 1 is shown, in which the first mobile mass 7 is in a main drive direction M p is offset with respect to a rest position (indicated by a dashed line for the sake of clarity), here to the right.

[0066] The elastic coupling structure 25 undergoes deformations in response to the movements of the first mobile mass 7.

[0067] In detail, the peripheral flexible portion 27 and the central flexible portion 28 undergo deformations such that the first ends 38 of the first and second connecting arms 33 and 34 move away from each other and the second ends 39 of the first and second connecting arms 33 and 34 move closer to each other.

[0068] In a first approximation, the first and second connecting arms 33 and 34 do not undergo deformations, since they have a much greater stiffness than the arms 30, 31 and 36, 37 of the peripheral and central flexible portions 27 and 28, respectively, and undergo rotations in the plane XY around an axis parallel to the third axis Z.

[0069] The displacement of the first end 38 of the second connecting arm 34 causes the second mobile mass 10 to move along a sense drive direction M p perpendicular to the main drive direction M i ( upwards in the example). Figure 2

[0070] Furthermore, the first and second arms 30 and 31 of the peripheral flexible portion 27 undergo deformations in order to compensate for the pseudo-movements of the first and second mobile masses 7 and 10 along a direction transverse to the first axis X and a direction transverse to the second axis Y, respectively. In fact, the first mobile mass 7 undergoes a displacement only in the main drive direction M p and the second mobile mass 10 undergoes a displacement only in the sense drive direction M i .

[0071] Moreover, the Applicant has verified that the first and second connecting arms 33 and 34, which extend transversely to the first and second axes X and Y (i.e. in a direction transverse to the main drive direction M p and in a direction transverse to the sense drive direction M i , can be subject to greater process variability than the arms 30, 31 and 36, 37 of the peripheral and central flexible portions 27 and 28, which extend respectively in a direction parallel to the first axis X and in a direction parallel to the second axis Y.

[0072] In fact, during the photolithography steps for defining the coupling structure 25, the known photolithography machines can cause a reduction in the accuracy of the definition of the portions of the coupling structure 25 which extend in certain directions.

[0073] ​Therefore, the dimensions of these portions of the coupling structure 25 can be subject to greater process variability, which can result in a high variability of the corresponding elastic deformation characteristics.

[0074] By increasing the stiffness of the portions of the MEMS gyroscope 1 subject to greater process variability, it is possible to compensate for the effect of this process variability on the performance of the MEMS gyroscope 1.

[0075] In fact, the stiffness of the first and second connecting arms 33 and 34 is greater than the stiffness of the arms 30, 31 and 36, 37 of the peripheral and central flexible portions 27 and 28, respectively, and therefore, in use, the fact of not experiencing deformations in the first approximation makes the coupling between the movements in the main drive direction M p and in the sense drive direction M i unaffected by any possible asymmetries due to process variability.

[0076] Therefore, when the MEMS gyroscope 1 does not experience a yaw angular velocity Ω z about the third axis Z, the second moving mass 10 does not move along the first axis X to the first approximation, and the detection structure 54 does not detect any variation of the capacitance associated with the yaw movement.

[0077] In other words, in the first approximation, the coupling structure 25 is able to suppress the quadrature error associated with the yaw movement. Therefore, the MEMS gyroscope 1 has a high stability of the yaw output signal.

[0078] This makes it possible for the MEMS gyroscope 1 to have a stable output signal even without the inclusion of additional quadrature error compensation electrodes, which would involve an increase in the complexity of the control circuit of the MEMS gyroscope 1.

[0079] Furthermore, the process for manufacturing the MEMS gyroscope 1 does not require dedicated photolithography machines or masks to improve the suppression of the yaw quadrature error. Therefore, the MEMS gyroscope 1 can maintain low manufacturing costs and short manufacturing times.

[0080] Figure 3 A different embodiment of the present MEMS gyroscope is shown, here designated by 100. Moreover, the MEMS gyroscope 100 is of the single-axis type, configured to detect a yaw angular velocity of the MEMS gyroscope 100, and has a general structure similar to that of the MEMS gyroscope 1; therefore, the common elements are designated by the same reference numerals and are not further described. Figure 1

[0081] The MEMS gyroscope 100 has a substantially symmetrical structure with respect to two central axes A, B passing through the center O of the MEMS gyroscope 100 and parallel to the first and second axes X and Y, respectively.​

[0082] The MEMS gyroscope 100 comprises a substrate 5 and four moving masses suspended above the substrate 5, here called a first moving mass 7, a second moving mass 10, a third moving mass 107 and a fourth moving mass 110.

[0083] The first moving mass 7 and the third moving mass 107 are symmetrically arranged with respect to the second central axis B and are connected to the first anchor region 13A and the third anchor region 113A, respectively, by a first flexure 15A and a third flexure 115A, respectively.

[0084] The third flexure 115A is identical to the first flexure 15A, here symmetrically arranged with respect to the second central axis B and extending parallel to the first axis X, each flexure portion 115A being between a respective third anchor region 113A and the third moving mass 107.

[0085] The second moving mass 10 and the fourth moving mass 110 are symmetrically arranged with respect to the first central axis A and are connected to the second anchor region 13B and the fourth anchor region 113B, respectively, by a second flexure 15B and a fourth flexure 115B, respectively.

[0086] The fourth flexure 115B is identical to the second flexure 15B, here symmetrically arranged with respect to the first central axis A and extending parallel to the second axis Y, each fourth flexure 115B being between a respective fourth anchor region 113B and the fourth moving mass 110.

[0087] Moreover, in this embodiment, the first moving mass 7, the second moving mass 10, the third moving mass 107 and the fourth moving mass 110 are coupled to the central anchor region 20 by the first flexure 15A, the second flexure 15B, the third flexure 115A and the fourth flexure 115B, respectively.

[0088] The MEMS gyroscope 100 further comprises four coupling structures 25A to 25D, hereinafter also called a first coupling structure 25A, a second coupling structure 25B, a third coupling structure 25C and a fourth coupling structure 25D.

[0089] The coupling structures 25A to 25D are equal to the coupling structures 25 of the MEMS gyroscope 1 of Figure 1 respectively, and are symmetrically arranged with respect to each other with respect to the first central axis A and the second central axis B.

[0090] In detail, the first coupling structure 25A is symmetrical with respect to the second central axis B to the second coupling structure 25B and with respect to the first central axis A to the fourth coupling structure 25D. The third coupling structure 25C is symmetrical with respect to the first central axis A to the second coupling structure 25B and with respect to the second central axis B to the fourth coupling structure 25D.

[0091] The first coupling structure 25A extends between the first moving mass 7 and the second moving mass 10. The second coupling structure 25B extends between the second moving mass 10 and the third moving mass 107. The third coupling structure 25C extends between the third moving mass 107 and the fourth moving mass 110. The fourth coupling structure 25D extends between the fourth moving mass 110 and the first moving mass 7.

[0092] Also here, the coupling structures 25A to 25D comprise a rigid portion 26, a peripheral flexible portion 27 and a central flexible portion 28, respectively, as discussed above and not further described herein.

[0093] The MEMS gyroscope 100 comprises first and second drive structures 145A, 145B of the capacitive type, coupled to the first and third moving masses 7, 107, respectively, and first and second detection structures 146A, 146B of the capacitive type, coupled to the second and fourth moving masses 10, 110, respectively.

[0094] In this embodiment, the first and second drive structures 145A, 145B each form a respective parallel-plate capacitor configured to move the first and third moving masses 7, 107 along the first axis X, respectively.

[0095] In detail, the first drive structure 145A comprises a fixed electrode 148 arranged at a distance along the first axis X from a moving electrode fixed with respect to the first moving mass 7, here in particular formed by a wall 7A of the first moving mass 7 facing the fixed electrode 148.

[0096] The second drive structure 145B comprises a fixed electrode 149 arranged at a distance along the first axis X from a moving electrode fixed with respect to the third moving mass 107, here in particular formed by a wall 107A of the third moving mass 107 facing the fixed electrode 149.

[0097] However, the first and second drive structures 145A, 145B can have different configurations than the one described above. Figure 3The number, shape and arrangement of the fixed electrodes 148, 149 and of the moving electrodes 7A, 107A can vary from the illustrated shape. For example, the fixed electrodes 148, 149 and the moving electrodes 7A, 107A can be cross- bar capacitors.

[0098] The first detection structure 146A and the second detection structure 146B each form a respective parallel-plate capacitor and are configured to detect the movement of the second moving mass 10 and of the fourth moving mass 110, respectively, along the first axis X.

[0099] In detail, the first detection structure 146A comprises two fixed electrodes 150A, 150B each arranged at a distance from a respective moving electrode along the first axis X, the moving electrode being fixed with respect to the second moving mass 10. In particular, here the moving electrodes of the first detection structure 146A are formed by two walls 10A, 10B of the second moving mass 10, the walls 10A, 10B being mutually symmetrical with respect to the second central axis B and facing the fixed electrodes 150A, 150B, respectively.

[0100] The second detection structure 146B comprises two fixed electrodes 151A, 151B each arranged at a distance from a respective moving electrode along the first axis X, the moving electrode being fixed with respect to the fourth moving mass 110. In particular, here the moving electrodes of the second detection structure 146B are formed by two walls 110A, 110B of the fourth moving mass 110, the walls 110A, 110B being mutually symmetrical with respect to the second central axis B and facing the fixed electrodes 150A, 150B, respectively.

[0101] However, the first detection structure 146A and the second detection structure 146B can have a shape different from Figure 3 The number, shape and arrangement of the fixed electrodes 150A, 150B, 151A, 151B and of the moving electrodes 10A, 10B, 110A, 110B can vary from the illustrated shape. For example, the fixed electrodes 150A, 150B, 151A, 151B and the moving electrodes 10A, 10B, 110A, 110B can be cross-bar capacitors.

[0102] Here, the MEMS gyroscope 100 further comprises a drive contact pad 60 electrically coupled to the first drive structure 145A and to the second drive structure 145B, and a detection contact pad 62 electrically coupled to the first detection structure 146A and to the second detection structure 146B.

[0103] In use, a drive voltage is supplied to the first 145A and second 145B drive structures, which causes the first 7 and third 107 mobile masses to move in a main drive direction Mp parallel to the first axis X, for example to oscillate at the resonant frequency of the MEMS gyroscope 100.

[0104] The drive voltage can be applied so that the relative movement of the first 7 and third 107 mobile masses is in phase or out of phase. For example, as indicated by the arrows M1, M2 in Figure 3 , the drive voltage can cause the first 7 and third 107 masses to move away from the central anchor region 20 in two opposite directions along the main drive direction Mp.

[0105] The coupling structures 25A-D undergo deformations in response to the movement of the first 7 and third 107 masses, each of the coupling structures 25A-D being as described above for the coupling structures 25 of the MEMS gyroscope 1 of Figure 1 , causes the second 10 and fourth 110 masses to move in an induced drive direction M i parallel to the second axis Y.

[0106] In detail, here the second 10 and fourth 110 mobile masses also move in two opposite directions along the induced drive direction M i away from the central anchor region 20, as indicated by the arrows M3, M4 in Figure 3 .

[0107] As mentioned above, the coupling structures 25A-D are not affected by possible process variations of the respective first 33 and second 34 connecting arms of the rigid portion 26. Therefore, in a first approximation, the movement of the second 10 and fourth 110 mobile masses does not have a component orthogonal to the first axis X.

[0108] Therefore, in the absence of a yaw angular velocity Ω z , the first 146A and second 146B detection structures do not detect any variation of the capacitance either.

[0109] The MEMS gyroscope 100 therefore has a stable output signal associated with the detection of the yaw angular velocity Ω z .

[0110] Figure 4 Different embodiments of the present MEMS gyroscope are shown, the present MEMS gyroscope being designated here by 200. The MEMS gyroscope 200 is of the triaxial type; i.e. it is configured to detect, in addition to the yaw angular velocity Ω z of the MEMS gyroscope 200, also a roll angular velocity Ωy and a pitch angular velocity Ω around an axis parallel to the first axis X x The MEMS gyroscope 200 has a general structure similar to that of the MEMS gyroscope 100 of Figure 3 ; therefore, common elements are designated by the same reference numerals and are not further described herein.

[0111] The MEMS gyroscope 200 has a substantially symmetrical structure with respect to two central axes A, B passing through the center O of the MEMS gyroscope 200 and parallel to the first axis X and to the second axis Y, respectively.

[0112] Moreover, the MEMS gyroscope 200 comprises a substrate 5 and four moving masses suspended above the substrate 5, here referred to as a first moving mass 207, a second moving mass 210, a third moving mass 217 and a fourth moving mass 220.

[0113] Here, the first moving mass 207, the second moving mass 210, the third moving mass 217 and the fourth moving mass 220 are also coupled to the central anchor region 20 and to the respective first anchor region 13A, second anchor region 13B, third anchor region 113A and fourth anchor region 113B via respective first, second, third and fourth flexures 15A, 15B, 115A and 115B.

[0114] In this embodiment, the first, second, third and fourth flexures 15A, 15B, 115A and 115B enable the first, second, third and fourth moving masses 207, 210, 217 and 220, respectively, to move along the first, second and third axes X, Y and Z.

[0115] Moreover, the MEMS gyroscope 200 here also comprises four coupling structures 25A to 25D coupling the first, second, third and fourth moving masses 207, 210, 217 and 220 together, as described above with reference to the MEMS gyroscope 100 of Figure 3 .

[0116] In this embodiment, the second and fourth moving masses 210 and 220 each laterally delimit a cavity designated by 225 and 226, respectively. The cavities 225, 226 extend throughout the thickness along the third axis Z of the second and fourth moving masses 210 and 220; i.e., they are through-type. In practice, here, the second and fourth moving masses 210 and 220 have an approximately frame-like shape.

[0117] The MEMS gyroscope 200 comprises first and second drive structures, here designated 245A, 245B, of the capacitive type, coupled to the first and third moving masses 207, 217, respectively.

[0118] In this embodiment, the first and second drive structures 245A, 245B are comb- finger capacitors. In detail, the first and second drive structures 245A, 245B each comprise a respective fixed electrode and a moving electrode, the fixed electrode being fixed to the substrate 5 and comprising a plurality of protrusions 251A, 251B, the moving electrode being integrated with respect to the first and third moving masses 207, 217, respectively, each moving electrode comprising a respective plurality of protrusions 253A, 253B.

[0119] In this embodiment, the MEMS gyroscope 200 comprises first and second yaw detection structures 260A, 260B, first and second roll detection structures 263A, 263B, and first and second pitch detection structures 265A, 265B.

[0120] The first and second yaw detection structures 260A, 260B are of the capacitive type and are coupled to the second and fourth moving masses 210, 220, respectively. In detail, the first and second yaw detection structures 260A, 260B comprise a first and a second fixed yaw electrode 270, 271, respectively, the first and second fixed yaw electrodes 270, 271 extending parallel to the second axis Y and being arranged within the first cavity 225 of the second moving mass 210 and within the second cavity 226 of the fourth moving mass 220, respectively.

[0121] The first and second yaw detection structures 260A, 260B further comprise a first and a second moving yaw electrode 275, 276, respectively. The first moving yaw electrode 275 extends parallel to the second axis Y from the second moving mass 210 towards the interior of the first cavity 225 so as to cross the first fixed electrode 270.

[0122] The second moving yaw electrode 276 extends parallel to the second axis Y from the fourth moving mass 220 towards the interior of the second cavity 226 so as to cross the second fixed electrode 271.

[0123] The first and second roll detection structures 263A, 263B capacitively couple the first and third moving masses 207, 217 to the substrate 5, respectively.

[0124] In detail, the first roll detection structure 263A and the second roll detection structure 263B comprise, respectively, a respective fixed electrode 280, here indicated by a dashed line, fixed to the substrate 5 and arranged at a distance from the first mobile mass 207 and the third mobile mass 217, respectively, along the third axis Z.

[0125] In practice, here, the fixed electrode 280 of the first roll detection structure 263A and the fixed electrode 280 of the second roll detection structure 263B are arranged, respectively, below the first mobile mass 207 and the third mobile mass 217, facing the first mobile mass 207 and the third mobile mass 217.

[0126] The first pitch detection structure 265A and the second pitch detection structure 265B capacitively couple, respectively, the second mobile mass 210 and the fourth mobile mass 220 to the substrate 5.

[0127] In detail, the first pitch detection structure 265A and the second pitch detection structure 265B each comprise a respective fixed electrode 284, here indicated by a dashed line, fixed to the substrate 5 and arranged at a distance from the second mobile mass 210 and the fourth mobile mass 220, respectively, along the third axis Z.

[0128] In practice, here, the fixed electrode 284 of the first pitch detection structure 265A and the fixed electrode 284 of the second pitch detection structure 265B are arranged, respectively, below the second mobile mass 210 and the fourth mobile mass 220, facing the second mobile mass 210 and the fourth mobile mass 220.

[0129] The first drive structure 245A and the second drive structure 245B, and the first yaw detection structure 260A and the second yaw detection structure 260B, can have shapes different from Figure 4 the shapes illustrated, for example similar to Figure 1 and / or Figure 3 the shapes illustrated.

[0130] Additionally or as an alternative, the first roll detection structure 263A and the second roll detection structure 263B, and the first pitch detection structure 265A and the second pitch detection structure 265B, can have shapes and arrangements different from Figure 4 the shapes and arrangements illustrated.

[0131] The MEMS gyroscope 200 also comprises here drive contact pads 60, which are electrically coupled to the first and second drive structures 245A, 245B, and detection contact pads 62, which are here electrically coupled to the first and second yaw detection structures 260A, 260B, to the first and second roll detection structures 263A, 263B, and to the first and second pitch detection structures 265A, 265B.

[0132] In use, the coupling structures 25A to 25D enable the MEMS gyroscope 200 to have a low quadrature error with respect to yaw detection, as described above.

[0133] In addition, the roll detection structures 263A, 263B and the pitch detection structures 265A, 265B are also able to detect a roll movement and a pitch movement, respectively.

[0134] A roll movement is caused by an angular velocity Ω y of the MEMS gyroscope 200 around the second axis Y. Indeed, in the presence of a roll angular velocity Ω y , the first and third moving masses 207, 217 oscillating along the first axis X are subjected to a Coriolis force directed along the third axis Z. The first and third moving masses 207, 217 are free to move along the third axis Z and the roll detection structures 263A, 263B detect a variation of the capacitance associated with said movement.

[0135] A pitch movement is caused by an angular velocity Ω x of the MEMS gyroscope 200 around the first axis X. Indeed, in the presence of a pitch angular velocity Ω x , the second and fourth moving masses 210, 220 oscillating along the second axis Y are subjected to a Coriolis force directed along the third axis Z. The second and fourth moving masses 210, 220 are free to move along the third axis Z and the pitch detection structures 265A, 265B detect a variation of the capacitance associated with said movement.

[0136] As Figure 5 illustrated, the MEMS gyroscope 1, 100, 200 can be incorporated into an electronic device 350, for example a smartphone, a laptop, a wearable device such as a watch or a bracelet, a digital camera, etc.

[0137] The electronic device 350 comprises a processing unit 352 and a memory 354, which are operatively coupled to the MEMS gyroscope 1, 100, 200 via a bus 356.

[0138] Furthermore, the electronic device 350 can also include an input / output (I / O) device 360, such as a keyboard or a display for example, and a wireless interface 362 and / or a battery 364, which are also coupled to the bus 356.

[0139] Finally, it is clear that modifications and variations can be made to the MEMS gyroscope 1, 100, 200 described and illustrated herein, without thereby departing from the scope of the present disclosure, as defined in the attached claims.

[0140] For example, the present MEMS gyroscope can also be adapted to operate as a two-axis type gyroscope.

[0141] Moreover, the detection and drive structures of the MEMS gyroscope 1, 100, 200 can have a different shape and number than the one illustrated. The present MEMS gyroscope can also comprise a larger number of drive structures. For example, the MEMS gyroscope 1 can also comprise a drive structure coupled to the second moving mass 10 and configured to move the second moving mass 10 in the sense drive direction. For example, the MEMS gyroscope 100, 200 can also comprise additional drive structures coupled to the second moving mass and / or to the fourth moving mass and configured to move the second moving mass and / or the fourth moving mass in the sense drive direction.

[0142] The drive and / or detection structures can have different operating mechanisms, such as piezoelectric or electromagnetic type for example.

[0143] For example, the described embodiments can be combined to form other solutions.

[0144] The MEMS gyroscope (1; 100; 200) can be summarized as comprising: a substrate (5); a first mass (7; 107; 207, 217) and a second mass (10; 110; 210, 220), the first and second masses being suspended above the substrate and extending in a rest condition in an extension plane (XY) defining a first direction (X) and a second direction (Y) transverse to the first direction; a drive structure (48; 145A, 145B; 245A, 245B) coupled to the first mass and configured to move the first mass in the first direction in use; and a resilient coupling structure (25; 25A to 25D) extending between the first mass and the second mass and configured to couple the movement of the first mass in the first direction (X) with the movement of the second mass in the second direction (Y), wherein the resilient coupling structure comprises a first portion (27, 28, 30, 31, 36, 37) having a first stiffness and a second portion (26, 33, 34) having a second stiffness greater than the first stiffness.

[0145] The first portion (27, 28, 30, 31, 36, 37) of the elastic coupling structure can extend in a first direction and a second direction, and the second portion (26, 33, 34) can extend in the plane of extension in a third direction transverse to the first and second directions.

[0146] The elastic coupling structure (25; 25A-D) can be configured to move the second mass (10; 110; 210, 220) in the second direction (Y) in response to movement of the first mass (7; 107; 207, 217) in the first direction (X).

[0147] The first direction (X) can be perpendicular to the second direction (Y).

[0148] The ratio between the second stiffness and the first stiffness can be between 10 and 100.

[0149] The first portion (27) of the elastic coupling structure (25; 25A-D) can comprise a first arm (30) coupled to the first mass and a second arm (31) coupled to the second mass, the second portion (26) of the elastic coupling structure extending between the first and second arms of the first portion of the elastic coupling structure.

[0150] The first portion (28) of the elastic coupling structure (25; 25A-D) can have a junction end (40) and can be formed by a first arm (36) and a second arm (37), the first and second arms extending from the junction end and being coupled to the second portion (26) of the elastic coupling structure (25; 25A-D).

[0151] The first arm (30, 36) can extend in the first direction (X) and the second arm (31, 37) can extend in the second direction (Y).

[0152] The second portion (26) of the elastic coupling structure (25; 25A-D) can comprise first and second connecting arms (33, 34) extending in the plane of extension in a third direction transverse to the first and second directions, the first connecting arm (33) extending from the first arm (30, 36) of the first portion (27, 28) of the elastic coupling structure, the second connecting arm (34) extending from the second arm (31, 37) of the first portion (27, 28) of the elastic coupling structure.

[0153] The first portion of the elastic coupling structure can have a size that can be smaller than a size of the second portion of the elastic coupling structure.

[0154] The MEMS gyroscope can further comprise a detection structure (46; 146A, 146B; 260A, 260B) coupled to the second arm (10; 110; 210, 220) and configured to detect, in use, movement of the second mass in the first direction (X) in the event that the MEMS gyroscope is rotated (Oz) about a fourth direction (Z) perpendicular to the first and second directions (X, Y).

[0155] The MEMS gyroscope can further comprise a first anchor region (13A; 113A, 20) and a second anchor region (13B; 113B, 20) fixed to the substrate (5), and a first flexure (15A; 115A) extending between the first mass (7; 107; 207, 217) and the first anchor region (13A; 113A, 20), and a second flexure (15B; 115B) extending between the second mass and the second anchor region (13B; 113B, 20).

[0156] The MEMS gyroscope (100; 200) can further comprise a third mass (107; 217) and a fourth mass (110; 220) suspended above the substrate, wherein the resilient coupling structure can be a first resilient coupling structure (25A), the MEMS gyroscope can further comprise a second resilient coupling structure, a third resilient coupling structure and a fourth resilient coupling structure (25B, 25C, 25D), wherein the second resilient coupling structure extends between the first mass and the fourth mass, the third resilient coupling structure extends between the fourth mass and the third mass, and the fourth resilient coupling structure extends between the second mass and the third mass.

[0157] The MEMS gyroscope can have a first and second axis of symmetry (A, B) parallel to the first and second directions, respectively, wherein the first mass can be symmetrical to the third mass with respect to the second axis of symmetry, the second mass can be symmetrical to the fourth mass with respect to the first axis of symmetry, the first resilient coupling structure can be symmetrical to the second resilient coupling structure with respect to the second axis of symmetry and to the fourth resilient coupling structure with respect to the first axis of symmetry, and the third resilient coupling structure can be symmetrical to the second resilient coupling structure with respect to the first axis of symmetry and to the fourth resilient coupling structure with respect to the second axis of symmetry.

[0158] The MEMS gyroscope (100; 200) can comprise a second drive structure (145B; 245B) coupled to the third mass and configured to move the third mass in the first direction in use, and a second detection structure coupled to the fourth mass and configured to detect movement of the fourth mass in the first direction (X) in use in the event that the MEMS gyroscope rotates (Ωz) about a fourth direction (Z) perpendicular to the first and second directions (X, Y).

[0159] The MEMS gyroscope (200) can further comprise a roll detection structure (263A, 263B) and / or a pitch detection structure (265A, 265B), wherein the roll detection structure can be configured to detect movement of the first mass and / or the third mass in a fourth direction (Z) perpendicular to the first and second directions (X, Y) in the event that the MEMS gyroscope rotates (Ωy) about the second direction (Y), and the pitch detection structure can be configured to detect movement of the second mass and / or the fourth mass in the fourth direction in the event that the MEMS gyroscope rotates (Ωx) about the first direction (X).

[0160] The detection structures can be of a capacitive type.

[0161] The drive structures can be of a capacitive type.

[0162] The various embodiments described above can be combined to provide further embodiments. If the concepts of the various patents, applications, and publications are employed to provide further embodiments, the various aspects of the embodiments can be modified.

[0163] These and other changes can be made to the embodiments in light of the above-detailed description. The terms used in the following claims should not be construed to limit the claims to the specific embodiments disclosed in the specification and claims. Rather, the scope of the claims should be construed to include all embodiments falling within the scope of the claims and their equivalents. Thus, the claims are not limited to the embodiments and practices described herein.

Claims

1. A microelectromechanical system, MEMS, device, comprising: a MEMS gyroscope, comprising: a substrate; a first mass and a second mass, the first mass and the second mass being suspended above the substrate and extending in an extension plane in a rest state, the extension plane defining a first direction and a second direction transverse to the first direction; a drive structure coupled to the first mass and configured to move the first mass in the first direction in use; and a resilient coupling structure extending between the first mass and the second mass and configured to couple movement of the first mass in the first direction to movement of the second mass in the second direction, the resilient coupling structure comprising a first portion having a first stiffness and a second portion having a second stiffness, the second stiffness being greater than the first stiffness, wherein the first portion of the resilient coupling structure extends in the first direction and the second direction, and wherein in the extension plane, the second portion extends in a third direction, the third direction being transverse to the first direction and the second direction.

2. The MEMS device of claim 1, wherein the resilient coupling structure is configured to move the second mass in the second direction in response to movement of the first mass in the first direction.

3. The MEMS device of claim 1, wherein the first direction is perpendicular to the second direction.

4. The MEMS device of claim 1, wherein a ratio between the second stiffness and the first stiffness is comprised between 10 and 100.

5. The MEMS device of claim 1, wherein the first portion of the resilient coupling structure comprises a first arm coupled to the first mass and a second arm coupled to the second mass, the second portion of the resilient coupling structure extending between the first arm and the second arm of the first portion of the resilient coupling structure.

6. The MEMS device of claim 1, wherein the first portion of the resilient coupling structure has a junction end and is formed by a first arm and a second arm, the first arm and the second arm extending from the junction end and being coupled to the second portion of the resilient coupling structure.

7. The MEMS device of claim 5, wherein the first arm extends in the first direction and the second arm extends in the second direction.

8. The MEMS device of claim 5, wherein the second portion of the resilient coupling structure comprises a first connecting arm and a second connecting arm, the first connecting arm and the second connecting arm extending in a third direction in the extension plane, the third direction being transverse to the first direction and the second direction, the first connecting arm extending from the first arm of the first portion of the resilient coupling structure, the second connecting arm extending from the second arm of the first portion of the resilient coupling structure.

9. The MEMS device of claim 1, wherein a size of the first portion of the elastic coupling structure is smaller than a size of the second portion of the elastic coupling structure.

10. The MEMS device of claim 1, further comprising a detection structure coupled to the second mass and configured to detect, in use, movement of the second mass in the first direction in the event that the MEMS gyroscope is rotated about a fourth direction, the fourth direction being perpendicular to the first direction and the second direction.

11. The MEMS device of claim 1, further comprising first and second anchor regions fixed to the substrate, and first and second flexures extending between the first mass and the first anchor region and between the second mass and the second anchor region, respectively.

12. The MEMS device of claim 1, further comprising third and fourth masses suspended over the substrate, wherein the elastic coupling structure is a first elastic coupling structure, the MEMS gyroscope further comprising a second elastic coupling structure, a third elastic coupling structure, and a fourth elastic coupling structure, wherein the second elastic coupling structure extends between the first mass and the fourth mass, the third elastic coupling structure extends between the fourth mass and the third mass, and the fourth elastic coupling structure extends between the second mass and the third mass.

13. The MEMS device of claim 12, wherein the MEMS gyroscope has first and second axes of symmetry parallel to the first and second directions, respectively, wherein the first mass is symmetric to the third mass with respect to the second axis of symmetry, the second mass is symmetric to the fourth mass with respect to the first axis of symmetry, the first elastic coupling structure is symmetric to the second elastic coupling structure with respect to the second axis of symmetry and to the fourth elastic coupling structure with respect to the first axis of symmetry, and the third elastic coupling structure is symmetric to the second elastic coupling structure with respect to the first axis of symmetry and to the fourth elastic coupling structure with respect to the second axis of symmetry.

14. The MEMS device of claim 12, comprising: a second drive structure coupled to the third mass and configured to, in use, move the third mass in the first direction; and a second detection structure coupled to the fourth mass and configured to, in use, detect, in the event that the MEMS gyroscope is rotated about a fourth direction, movement of the fourth mass in the first direction, the fourth direction being perpendicular to the first direction and the second direction.

15. The MEMS device of claim 12, further comprising a roll detection structure and / or a pitch detection structure, wherein the roll detection structure is configured to detect movement of the first mass and / or the third mass in a fourth direction that is perpendicular to the first direction and the second direction in the event that the MEMS gyroscope is rotated about the second direction, and wherein the pitch detection structure is configured to detect movement of the second mass and / or the fourth mass in the fourth direction in the event that the MEMS gyroscope is rotated about the first direction.

16. A microelectromechanical system (MEMS) device, comprising: a MEMS gyroscope, comprising: a substrate; a first moving mass suspended above the substrate; a second moving mass suspended above the substrate; a resilient coupling structure, comprising: a first arm coupled to the first moving mass, the first arm having a first stiffness; a second arm coupled to the second moving mass, the second arm having a second stiffness; a first connecting arm coupled to and extending from the first arm, the first connecting arm having a third stiffness that is greater than the first and second stiffnesses; a second connecting arm coupled to and extending from the second arm, the second connecting arm having a fourth stiffness that is greater than the first and second stiffnesses; a central flexible portion coupled to the first connecting arm and to the second connecting arm, the central flexible portion extending from the first connecting arm to the second connecting arm, the central flexible portion having a fifth stiffness that is less than the third and fourth stiffnesses.

17. The device of claim 16, wherein the central flexible portion comprises: a junction end between the first connecting arm and the second connecting arm; a third arm extending from the first connecting arm to the junction end; and a fourth arm extending from the second connecting arm to the junction end, the fourth arm being coupled to the third arm at the junction end.

18. A microelectromechanical system (MEMS) device, comprising: a MEMS gyroscope, comprising: a substrate; a first moving mass suspended above the substrate, the first moving mass comprising a plurality of first protrusions protruding outward from the first moving mass; a second moving mass suspended above the substrate, the second moving mass comprising a plurality of second protrusions protruding outward from the second moving mass; a central anchor region; a first flexure coupling the first moving mass to the central anchor region; a second flexure coupling the second moving mass to the central anchor region; a first stationary electrode in electrical communication with the plurality of first protrusions; a second stationary electrode in electrical communication with the plurality of second protrusions; ​ a resilient coupling structure coupling the first moving mass to the second moving mass and configured to, in operation, transfer motion of the first moving mass to the second moving mass, the resilient coupling structure comprising a peripheral flexible portion, a central flexible portion, and a rigid portion, wherein the rigid portion has a rigidity greater than a rigidity of the peripheral flexible portion and the central flexible portion, wherein the peripheral flexible portion and the central flexible portion extend in a first direction and a second direction, and wherein, in the plane of extension, the rigid portion extends in a third direction, the third direction being transverse to the first direction and the second direction.

19. The MEMS device of claim 18, wherein the peripheral flexible portion comprises: a first arm coupled to the first moving mass, the first arm configured to, in operation, deform; a second arm coupled to the second moving mass, the second arm configured to, in operation, deform; wherein the rigid portion comprises: a first connecting arm coupled to and extending from the first arm; a second connecting arm coupled to and extending from the second arm; and wherein the central flexible portion is coupled to the first connecting arm and to the second connecting arm, the central flexible portion extending from the first connecting arm to the second connecting arm, and the central flexible portion configured to, in operation, deform, the central flexible portion comprising: a junction end between the first connecting arm and the second connecting arm; a third arm extending from the first connecting arm to the junction end; and a fourth arm extending from the second connecting arm to the junction end, the fourth arm coupled to the third arm at the junction end.

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