Micro-electromechanical gyroscope and method for compensating output thermal drift in a micro-electromechanical gyroscope

Abstract

Embodiments of the present disclosure relate to a microelectromechanical gyroscope and a method for compensating for output thermal drift in a microelectromechanical gyroscope. The microelectromechanical gyroscope includes a support structure; a sense mass coupled to the support structure with degrees of freedom along a drive direction and a sense direction, the drive direction and the sense direction being perpendicular to each other; and a calibration structure facing the sense mass and separated from the sense mass by a gap having an average width, the calibration structure being movable relative to the sense mass such that displacement of the calibration structure causes a change in the average width of the gap. A calibration actuator controls the relative position of the calibration structure relative to the sense mass and the average width of the gap.

Description

Technical Field

[0001] The present disclosure relates to a micro-electromechanical gyroscope and a method for compensating for output thermal drift in a micro-electromechanical gyroscope. Background Art

[0002] It is well known that in a micro-electromechanical gyroscope, the stability of the zero-rate output (ZRO) is a key parameter for performance quality and can be crucial for very high accuracy.

[0003] Quadrature error is one of the main factors determining the zero-rate output (ZRO) range of a MEMS gyroscope. Simply put, quadrature error is caused by imperfections that affect the output signal. Briefly, a MEMS gyroscope comprises a driving mass constrained by a support structure to oscillate with (at least) one degree of freedom according to a driving direction; and a sensing mass constrained by the driving mass to be dragged along the driving direction and to oscillate relative to the driving mass with (at least) one degree of freedom according to a sensing direction perpendicular to the driving direction. When the support structure rotates about a rotation axis perpendicular to the driving and sensing directions, the sensing mass experiences a virtual force in the sensing direction due to the drag, depending on the angular velocity and the velocity in the driving direction. The displacement of the sensing mass caused by the virtual force is converted into an electrical signal proportional to the angular velocity relative to the rotation axis. Other known solutions employ a single movable mass constrained by a support structure and capable of oscillating with a certain degree of freedom along the driving direction and a certain degree of freedom along the sensing direction. Thus, the mass acts as both the driving mass and the sensing mass.

[0004] Due to unavoidable imperfections associated with the manufacturing of the connection elements between the support structure and the movable mass or masses, the actuation direction is not perfectly perpendicular to the sensing direction. This results in a displacement in the sensing direction caused by the same actuation motion, leading to a quadrature noise signal component that is 90° phase-shifted relative to the desired signal. This component is present even when the gyroscope is stationary and causes an offset in the output signal. The amplitude and stability of this offset over lifetime are critical parameters for new-generation gyroscopes.

[0005] Through the dependence of phase on temperature, orthogonality error is also one of the factors that has the greatest impact on zero-rate output stability.

[0006] It is known to take some measures to reduce the drift of the zero-rate output, but these measures are not entirely satisfactory for several reasons.

[0007] The first known solution is so-called series compensation. In practice, the same correction, determined statistically, is applied to all gyroscopes in a series. The output is corrected digitally based on the estimated quadrature for the series and the measured temperature. While attractive because it's inexpensive, this solution isn't particularly accurate because it's not personalized. Consequently, device parameters that deviate from the device parameters used as the basis for determining the series compensation exhibit residual drift in the output.

[0008] A more accurate solution is to calibrate the gyroscopes individually, determining a specific correction and applying it digitally to each device. This provides significantly higher accuracy, but the process is expensive and time-consuming.

[0009] According to another known solution, closed-loop dynamic compensation is performed. A gyroscope is provided with electrodes and a sensing circuit configured to sense the actual deflection continuously or over samples, and a closed-loop compensation circuit that determines a compensation signal based on the sensed deflection and applies the compensation signal to the output signal. This solution can be very accurate, enabling the compensation to be adapted to the actual conditions of the gyroscope and also being robust to drift that occurs over the device's lifetime. However, the compensation circuit used has a complex architecture and is expensive in terms of both production costs and energy consumption, another essential parameter. Summary of the Invention

[0010] The present disclosure aims to provide a micro-electromechanical gyroscope and a method for compensating output thermal drift in a micro-electromechanical gyroscope that allows overcoming or at least alleviating the above-mentioned limitations.

[0011] According to the present disclosure, a micro-electromechanical gyroscope and a method for compensating for output thermal drift in the micro-electromechanical gyroscope are provided.

[0012] In at least one embodiment, a microelectromechanical gyroscope includes a support structure. A sense mass is coupled to the support structure with degrees of freedom along a drive direction and a sense direction, the drive direction and the sense direction being transverse or perpendicular to each other. A calibration structure faces the sense mass and is separated from the sense mass by a gap having an average width. The calibration structure is movable relative to the sense mass such that displacement of the calibration structure causes a change in the average width of the gap. A calibration actuator is configured to control a relative position of the calibration structure relative to the sense mass and the average width of the gap.

[0013] In at least one embodiment, a method includes compensating for output thermal drift in a microelectromechanical gyroscope, including arranging a calibration structure of the microelectromechanical gyroscope facing a sense mass and spaced apart from the sense mass by a gap having an average width, and moving the calibration structure to change the average width of the gap.

[0014] In at least one embodiment, a system includes a microelectromechanical gyroscope comprising: a support structure having a surface; a cover coupled to the support structure; a chamber defined by the support structure and the cover; an anchor portion extending from the support structure into the chamber; a sensing mass coupled to the support structure via a plurality of flexible portions and covering the surface of the support structure; a fulcrum portion coupled to an end of the anchor portion spaced apart from the surface of the support structure, the fulcrum portion having a fulcrum axis; a calibration structure coupled to the fulcrum portion, the calibration structure having: a calibration plate coupled to the fulcrum portion, the calibration plate having a first portion on a first side of the fulcrum axis and a second portion on a second side of the fulcrum axis, the first portion overlapping the sensing mass; a gap extending from the calibration plate to the sensing mass; and a processing unit coupled to the microelectromechanical gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a better understanding of the present disclosure, some embodiments thereof will now be described, by way of non-limiting example only, and with reference to the accompanying drawings, in which:

[0016] Figure 1 is a cross-sectional view of a micro-electromechanical gyroscope according to one embodiment of the present disclosure.

[0017] Figure 2 yes Figure 1 The MEMS gyroscope Figure 1 Top view taken along line II-II.

[0018] Figure 3 yes Figure 1 Simplified block diagram of a MEMS gyroscope;

[0019] Figure 4 and Figure 5 are plots of quantities related to the series of gyroscopes before and after the series of calibration operations, respectively;

[0020] Figure 6 and Figure 7 Shown respectively Figure 1 The micro-electromechanical gyroscope is in a first operating configuration and a second operating configuration;

[0021] Figures 8-13 yes Figure 1 Cross-sectional views of a semiconductor wafer in successive steps of a fabrication process of a MEMS gyroscope;

[0022] Figure 14 is a top view of a micro-electromechanical gyroscope according to various embodiments of the present disclosure, with portions removed for clarity;

[0023] Figure 15 yes Figure 14 The MEMS gyroscope Figure 14 Front view taken along line XV-XV;

[0024] Figure 16 is a top view of a micro-electromechanical gyroscope according to yet another embodiment of the present disclosure, with portions removed for clarity;

[0025] Figure 17 yes Figure 16 The MEMS gyroscope Figure 16 A front view taken along line XVII-XVII of FIG. 1; and

[0026] Figure 18 is a simplified block diagram of an electronic system incorporating a microelectromechanical gyroscope according to the present disclosure. DETAILED DESCRIPTION

[0027] refer to Figure 1 A micro-electromechanical gyroscope according to an embodiment of the present disclosure is schematically illustrated and indicated using reference numeral 1 , and includes a packaging structure 2 , a movable sensing mass 3 , and a calibration structure 5 .

[0028] The package structure 2 comprises a support structure 6 and a cover 7, which are joined together in a hermetically sealed manner and define between them a hermetically closed and sealed chamber 8. A controlled atmosphere, such as low-pressure argon, is present in the chamber 8. The support structure 6 may be a single monolithic semiconductor body or comprise several layers, such as a single-crystal substrate and one or more epitaxial layers connected to each other and to the substrate directly or via an intermediate layer, such as a dielectric layer, for example silicon oxide, or a conductive layer, such as a suitably doped polysilicon layer.

[0029] The sensing mass 3 and calibration structure 5 are housed in a chamber 8. The support structure 6 and cover 7 define the chamber 8, which may be referred to as a cavity.

[0030] Sense mass 3 is made of a semiconductor material, such as single-crystal epitaxial silicon, and is constrained to support structure 6 by a flexible portion 10. Flexible portion 10 is configured to allow sense mass 3 to oscillate relative to support structure 6 along a drive direction DD, which is parallel to a face 6 a of support structure 6 (which may be referred to as a surface), and along a sense direction DS, which is transverse or perpendicular to face 6 a and drive direction DD. A drive actuator 12 is operable to cause sense mass 3 to oscillate along drive direction DD at a controlled frequency and amplitude. For example, drive actuator 12 may include a set of electrodes fixed to support structure 6 and a set of movable electrodes fixed to sense mass 3, coupled in a comb-finger configuration.

[0031] The sensing mass 3 , which is made conductive by doping, is capacitively coupled to a sensing electrode 13 , which is arranged on the face 6 a of the support structure 6 and faces the sensing mass 3 .

[0032] The calibration structure 5 is connected to a fulcrum portion 15 fixed to the support structure 6 by means of an anchor portion 16 and can rotate about a fulcrum axis F, which is parallel to the face 6 a and transverse or perpendicular to both the drive direction DD and the sense direction DS. In more detail, the calibration structure 5 includes a calibration plate 17 and a coupling mass 18, which is capacitively coupled to calibration electrodes 20 on the face 6 a of the support structure 6. The calibration plate 17 and the coupling mass 18 are combined to form a single rigid body. The fulcrum portion 15 is located at the end of the anchor portion, spaced apart from the face 6 a of the support structure 6.

[0033] The calibration plate 17 is connected to the fulcrum portion 15 and has a first portion 17a and a second portion 17b opposite the fulcrum portion 15. In one embodiment, the calibration plate 17 is eccentric relative to the fulcrum portion 15 so that the first portion 17a has a larger size than the second portion 17b. The first portion 17a faces the sensing mass 3 on the side opposite to the support structure 6 and is separated from the sensing mass 3 by a gap 21. The sensing mass 3 is therefore located between the sensing electrode 13 and the calibration structure 5 along the sensing direction DS. As explained in detail below, the average width W of the gap 21 is determined by the rest position of the sensing mass 3 and the position of the calibration structure 5. When the calibration plate 17 is in a position such as Figure 1 In the position shown, the first portion 17a is located on a first side of the fulcrum axis F and the second portion is located on a second side of the fulcrum axis F.

[0034] The coupling proof mass 18 is capacitively coupled to the calibration electrode 20 and is therefore subject to an electrostatic force, the sign and strength of which are related to the bias voltage of the calibration electrode 20 .

[0035] The gyroscope 1 is provided with Figure 3 Schematically illustrated is a control unit 25, which, among other things, has the task of determining the bias voltage of calibration electrode 20. Control unit 25 comprises a drive device 26 configured to cause sensing mass 3 to oscillate along a drive direction DD at a controlled frequency and amplitude; a sensing device 27 configured to sense the displacement of sensing mass 3, acting as a movable mass, along a sensing direction DS and convert the sensed displacement into an output signal SO indicative of the rotational speed of gyroscope 1; a calibration module 28, and a charge pump 30. Calibration module 28 drives charge pump 30, which is coupled to calibration electrode 20 and sets calibration voltage VC. Thus, in practice, calibration electrode 20 and charge pump 30 define a calibration actuator configured to control the relative position of calibration structure 5 relative to sensing mass 3, and in particular, the average width W of gap 21.

[0036] Compensation for temperature-induced drift of the zero-rate output of gyroscope 1 occurs as follows. Initially, a series of calibrations is applied, which in one embodiment is performed by calibration module 28 by acting on sensing device 27 to modify output signal SO. The series of calibrations is determined on a statistical basis by observing samples of gyroscopes having the same structure as gyroscope 1. The average error is determined from the drift distribution of the zero-rate output of the samples ( Figure 4 ) and the corresponding correction is applied to all gyroscopes in the series. The effect of series calibration is as follows Figure 5 The residual difference in temperature drift is due to the spread of the quality factor Q, which varies from device to device due to process imperfections. The quality factor Q is affected by the mobility of the gas molecules in chamber 8, which in turn is related to the distance to the surrounding mass. Specifically, in gyroscope 1, the quality factor Q is proportional to the square root of the average width W of the gap 21 between the sensing mass 3 and the first portion 17a of the calibration plate 17 (i.e., the portion of the calibration structure 5 facing the sensing mass 3 itself):

[0037]

[0038] By acting on the calibration electrode 20, the electrostatic force applied to the calibration structure 5 can be modulated by means of the coupled mass 18, and thus the amplitude of the gap 21 can be varied by correspondingly modifying the quality factor Q, in order to cancel or in any case significantly reduce the temperature drift of the output signal SO in the absence of rotation, i.e. zero rate output (ZRO). Figure 1 In the embodiment, the electrostatic force, via modulation of the calibration electrode 20, allows the calibration structure 5 to rotate counterclockwise to reduce the width W of the gap 21 and the quality factor Q, which can be referred to as a first rotation direction, and to rotate clockwise to increase the width W of the gap 21 and the quality factor Q, which can be referred to as a second rotation direction opposite the first rotation direction. Correction of the quality factor Q is very simple and quick to perform and can therefore be performed on each individual device without expending significant time to substantially eliminate offsets in the output signal SO caused by quadrature errors. The control unit 25 itself can be provided with a calibration function, which can be activated, for example, on command or when certain stability conditions occur. In this way, calibration of the zero-rate output can be performed not only at the factory before use, but also subsequently during the device's service life to eliminate components that may arise due to aging, thermomechanical stress, and generally, environmental factors.

[0039] Figure 6 Shown in a first operational configuration Figure 1 MEMS gyroscope 1. Figure 6As shown, when the microelectromechanical gyroscope 1 is in the first operating configuration, the calibration plate 17 is in the first position. When in the first operating configuration, the calibration plate 17 has been rotated in the counterclockwise direction so that the first portion 17a has been rotated toward the sensing mass 3 and the second portion 17b has been rotated away from the calibration electrode 20. When the calibration plate 17 is in the first position, the average width W is reduced so that Figure 6 The average width W shown in Figure 1 The average width W is shown in .

[0040] Figure 7 Shown Figure 1 The MEMS gyroscope 1 is in Figure 6 The first operating configuration shown is different from the second operating configuration. Figure 7 As shown, when the microelectromechanical gyroscope 1 is in the second operating configuration, the calibration plate 17 is in the second position. When in the second operating configuration, the calibration plate 17 has been rotated in a clockwise direction so that the first portion 17a has been rotated away from the sense mass 3 and the second portion 17b has been rotated towards the calibration electrode 20. When the calibration plate 17 is in the second position, the average width W increases so that Figure 7 The average width W shown in Figure 1 The average width W is shown in .

[0041] It should be readily understood that the first position of the calibration plate 17 is different from the second position of the calibration plate. Figure 6 In the first position shown, the calibration plate 17 is in the Figure 7 When the calibration plate 17 is in the first position, the second portion 17b of the calibration plate 17 is closer to the sensing mass 3 than when the calibration plate 17 is in the second position shown. Figure 7 The second position shown is further away from the calibration electrode 20 than that shown in FIG.

[0042] Figure 1 The gyroscope 1 can be referenced by the following Figures 8 to 16 In practice, as described in detail below, the sensing mass 3, the coupling mass 18 and the anchoring portion 16 of the fulcrum portion 15 on one side and the calibration plate 17 on the other side are obtained from two structural layers grown epitaxially on each other.

[0043] refer to Figure 8A first dielectric layer 51, such as silicon oxide, is grown on a substrate 6' of a wafer 50 of semiconductor material (e.g., single-crystal silicon). A conductive layer (not shown), such as polycrystalline silicon, is deposited on the first dielectric layer 51 and shaped to form the sensing electrode 13 and the calibration electrode 20. A first sacrificial layer 53, such as thermally grown or deposited silicon oxide, is formed on the first dielectric layer 51, above the sensing electrode 13 and the calibration electrode 20. The first sacrificial layer 53 is selectively etched in locations corresponding to the peripheral (outer periphery) portions of the anchor 16 and the support structure 6, which will be formed later. A first epitaxial layer 55 is then formed on the first sacrificial layer 53. The first epitaxial layer 55 has a thickness determined based on the desired characteristics of the microelectromechanical structure and can be, for example, between 2 and 80 μm. After epitaxial growth, the first epitaxial layer 55 is planarized, for example, by CMP (chemical mechanical polishing), to a desired final thickness.

[0044] Figure 9 The first epitaxial layer 55 in the wafer is etched to define the bottom portion of the desired structure and other desired areas. Specifically, in this step, the drive actuator 12 and the flexible portion 10 (not shown here) can be formed by the first epitaxial layer 55. In addition, the first epitaxial layer 55 is intended to separate the various parts of the sensing mass 3, the coupling mass 18, and the anchoring portion 16 from each other. To this end, the wafer 50 is covered with a resist mask (not shown) and subjected to dry etching to form a trench 61 completely passing through the first epitaxial layer 55. The resist mask can be referred to as a first trench mask. The etching automatically stops on the first sacrificial layer 53.

[0045] Then, a second sacrificial layer 60, for example of TEOS (tetraethylorthosilicate), is deposited to a thickness of, for example, 1 to 2 μm. The second sacrificial layer 60 partially fills the trench 61, for example, to one-third of its depth, but this filling, as well as the degree and depth of filling, are not critical. The second sacrificial layer 60 is then planarized.

[0046] like Figure 10 As shown, the second sacrificial layer 60 is selectively etched and removed using a mask layer (not shown), thereby forming an opening 62. The mask layer can be referred to as a second anchoring mask. The etching of the second sacrificial layer 60 automatically terminates on the first epitaxial layer 55. Typically, the second anchoring opening 62 is formed in an area where a connection area needs to be formed between the first epitaxial layer 55 and the second epitaxial layer to be formed later. Specifically, here, the second anchoring opening 62 is formed in a position corresponding to the fulcrum portion 15, the bonding area between the coupling mass block 18 and the calibration plate 17, and the peripheral portion of the wafer 50.

[0047] Later, in Figure 11In the embodiment of the present invention, a second epitaxial layer 65 is grown, the thickness of which here also depends on the desired microelectromechanical structure and here also can be comprised between 2 and 80 μm. Generally, the second epitaxial layer 65 can be thinner than the first epitaxial layer 55, but the opposite can also occur and the present disclosure is not limited to any specific ratio between the thicknesses of the epitaxial layers 55, 65.

[0048] After epitaxial growth, the second epitaxial layer 65 is planarized, for example by CMP (chemical mechanical polishing), and brought to the desired final thickness. In this way, the structural layer formed by the first and second epitaxial layers 55, 65 (also referred to as the total epitaxial layer) reaches its final thickness, which typically varies between 20 and 80 μm.

[0049] Wafer 50 such as Figure 12 To this end, the wafer 50 is covered with a resist mask (not shown) and subjected to dry etching. In this step, the portions of the epitaxial layers 55, 65 not covered by the second trench mask are removed over the entire thickness of the epitaxial layer, and the etching stops on the first sacrificial layer 53.

[0050] Specifically, in this step, the sensing mass 3 , the calibration plate 17 and the coupling mass 18 are defined.

[0051] Then, Figure 13 , the second sacrificial layer 60 and the remaining parts of the first sacrificial layer 53 are removed, thereby releasing the movable mass and the calibration structure 5 .

[0052] Finally, a cover wafer (not shown) corresponding to the cover 7 is bonded to the wafer 50 by means of an adhesive layer and the composite wafer thus obtained is cut to form Figure 1 The peripheral portions of the epitaxial layers 55 , 65 in each die together with corresponding portions of the substrate 6 ′ form the support structure 6 of the gyroscope 1 .

[0053] refer to Figure 14 and Figure 15 A micro-electromechanical gyroscope 100 according to an embodiment of the present disclosure includes a packaging structure 102, a sensing mass 103, and a calibration structure 105. The packaging structure 102 includes a support structure 106 and a lid 107, which are joined or coupled together in a hermetically sealed manner and define a hermetically closed chamber 108 therebetween, in which a controlled atmosphere, such as low-pressure argon, exists.

[0054] The sensing mass 103 and calibration structure 105 are housed in a chamber 108. The support structure 106 and the cover 107 define the chamber 108, which may be referred to as a cavity.

[0055] Sense mass 103 of semiconductor material is frame-shaped and constrained to support structure 106 by flexible portion 110. Flexible portion 110 is configured to allow sense mass 103 to oscillate relative to support structure 106 along a drive direction DD′ and along a sense direction DS′, both of which are parallel to face 106a of support structure 106 and transverse or perpendicular to each other. A drive actuator 112 is operable to cause sense mass 103 to oscillate along drive direction DD′ at a controlled frequency and amplitude.

[0056] Sensing electrodes 113 fixed to support structure 106 face respective sides of sensing mass 103 and are capacitively coupled to respective sides of sensing mass 103. In one embodiment, sensing electrodes 113 are arranged inside the frame structure of sensing mass 103.

[0057] Calibration structure 105 is defined by mass 109, which is connected to support structure 106 by means of flexible portion 115, which allows movement along sensing direction DS'. Calibration structure 105 has a first side 105a facing one side of sensing mass 103 and spaced apart from sensing mass 103 by a gap 121. The average width W' of gap 121 is determined by the rest position of sensing mass 103 and the position of calibration structure 105. In addition, calibration structure 105 is capacitively coupled to calibration electrode 120, which is arranged on support structure 106 and faces a second side 105b of calibration structure 105 opposite first side 105a. Calibration electrode 120 can be connected to Figure 3 The charge pump 30 is used in combination with the calibration module 28 to form a calibration actuator controlled by the calibration module 28. The calibration structure 105 is thus subjected to an electrostatic force whose strength is related to the bias voltage of the calibration electrode 120. By acting on the calibration electrode 120, the electrostatic force applied to the calibration structure 105 can be modulated, and thus the amplitude of the gap 121 can be modified to cancel or in any case significantly reduce the temperature drift of the zero-rate output by correspondingly modifying the quality factor Q. In particular, in Figure 14 and Figure 15 In an embodiment, calibration structure 105 may be moved closer to sense mass 103 to reduce width W′ and quality factor Q of gap 121 , and moved away from sense mass 103 to reduce width W′ and quality factor Q of gap 121 .

[0058] refer to Figure 16 and Figure 17A micro-electromechanical gyroscope 200 according to an embodiment of the present disclosure includes a packaging structure 202, a driving mass 201, a sensing mass 203, and a calibration structure 205. The packaging structure 202 includes a support structure 206 and a cover 207, which are joined or coupled together in a hermetically sealed manner and define a hermetically closed chamber 108 therebetween, in which a controlled atmosphere, such as low-pressure argon, exists.

[0059] The drive mass 201, sense mass 203, and calibration structure 205 are housed in a chamber 208. The support structure 206 and cover 207 define the chamber 208, which may be referred to as a cavity.

[0060] The drive mass 201 of semiconductor material is C-shaped and constrained to the support structure 206 by a flexible portion 210a. The flexible portion 210a is configured to allow the drive mass 201 to oscillate relative to the support structure 206 along a drive direction DD" that is parallel to a face 206a of the support structure 206 itself. A drive actuator 212 is operable to cause the drive mass 201 to oscillate along the drive direction DD" at a controlled frequency and amplitude.

[0061] A sensing mass 203, also made of a semiconductor material, is housed inside the driving mass 201 and faces the open side and is constrained to the driving mass 201 by a flexible portion 210b. The flexible portion 210b is configured to allow the sensing mass 203 to oscillate relative to the driving mass 201 and, therefore, relative to the support structure 206, along a sensing direction DS″ that is parallel to the face 206a of the support structure 206 and transverse or perpendicular to the driving direction DD″.

[0062] Sensing electrode 213 fixed to support structure 206 faces one side of sensing mass 203 and is capacitively coupled to one side of sensing mass 203. In one embodiment, sensing electrode 213 is arranged between sensing mass 203 and a closed side of C-shaped sensing mass 203.

[0063] The calibration structure 205 is defined by a mass 209 connected to the support structure 206 by a flexible portion 215 that allows movement in a sensing direction D". The calibration structure 205 has a first side 205a facing one side of the sensing mass 203 and spaced apart from the sensing mass 203 by a gap 221. The average width W" of the gap 221 is determined by the rest position of the driving mass 201 and the position of the calibration structure 205. In addition, the calibration structure 205 is capacitively coupled to a calibration electrode 220 that is arranged on the support structure 206 and faces a second side 205b of the calibration structure 205 opposite the first side 205a. The calibration electrode 220 can be connected to Figure 3The charge pump 30 is used in combination to form a calibration actuator controlled by the calibration module 28. Also in this case, by acting on the calibration electrode 220, the amplitude of the gap 221 can be modified by correspondingly modifying the quality factor Q, so as to cancel or in any case significantly reduce the temperature drift of the zero-rate output.

[0064] Figure 18 The electronic system 300 is shown as any type, specifically, but not limited to, a wearable device such as a watch, smart bracelet, or wristband; a computer such as a mainframe, personal computer, laptop, or tablet; a smartphone; a digital music player, a digital camera, or any other device for processing, storing, transmitting, or receiving information. The electronic system 300 may be a general-purpose or device-embedded processing system, a device, or a further system.

[0065] The electronic system 300 includes a processing unit 302, a memory device 303, a micro-electromechanical gyroscope according to the present disclosure (e.g., Figure 1 The electronic system 300 may also include a microelectromechanical gyroscope 1) and may also be provided with an input / output (I / O) device 305 (e.g., a keyboard, a pointer, a touch screen, or some other suitable type of input or interface device), a wireless interface 306, peripheral devices 307.1, ..., 307.N, and possibly other auxiliary devices not shown here. The components of the electronic system 300 may be directly and / or indirectly communicatively coupled to each other via a bus 308. The electronic system 300 may also include a battery 309. It should be noted that the scope of the present disclosure is not limited to embodiments having one or all of the listed devices.

[0066] Depending on design preferences, the processing unit 302 may include, for example, one or more microprocessors, microcontrollers, etc. The processing unit 302 may include, for example, one or more processors, controllers, etc.

[0067] The memory device 303 may include various types of volatile memory devices and non-volatile memory devices, such as SRAM and / or DRAM memory and solid-state memory for the volatile type, and magnetic disks and / or optical disks for the non-volatile type.

[0068] Finally, it is clear that modifications and variations may be made to the microelectromechanical gyroscope and to the method described without departing from the scope of the present disclosure, as defined in the appended claims.

[0069] The microelectromechanical gyroscope can be summarized as comprising: a support structure (6; 106; 206); a sensing mass (3; 103; 203) coupled to the support structure (6; 106; 206) with a certain degree of freedom along a driving direction (DD; DD'; DD") and a sensing direction (DS; DS') perpendicular to each other; a calibration structure (5; 105; 205) facing the sensing mass (3; 103; 203) and spaced apart from the sensing mass (3; 103; 203) by a gap (21; 121; 221) having an average width (W; W'; W") ), a calibration structure (5; 105; 205) is movable relative to the sensing mass (3; 103; 203) such that displacement of the calibration structure (5; 105; 205) results in a change in the average width (W; W′; W″) of the gap (21; 121; 221); a calibration actuator (20, 30; 120, 30; 220, 30) configured to control the relative position of the calibration structure (5; 105; 205) relative to the sensing mass (3; 103; 203) and the average width (W; W′; W″) of the gap (21; 121; 221).

[0070] The calibration actuator (20, 30; 120, 30; 220, 30) may include: a calibration electrode (20; 120; 220) arranged on a support structure (6; 106; 206) and capacitively coupled to a calibration structure (5; 105; 205); and a bias source (30) coupled to the calibration electrode (20; 120; 220).

[0071] The driving direction (DD) can be parallel to the surface (6a) of the support structure (6) and the sensing direction (DS) can be perpendicular to the surface (6a) and perpendicular to the driving direction (DD), and the calibration structure (5) can be connected to a fulcrum portion (15) fixed to the support structure (6) and can rotate around a fulcrum axis (F), which is parallel to the surface (6a) and perpendicular to both the driving direction (DD) and the sensing direction (DS).

[0072] The calibration structure (5) may include a calibration plate (17) coupled to the fulcrum portion (15) and may have a first portion (17a) and a second portion (17b) opposed to the fulcrum portion; the first portion (17a) faces the sensing mass (3) on a side of the sensing mass (3) opposite to the support structure (6) and may be spaced apart from the sensing mass (3) by a gap (21).

[0073] The calibration structure (5) may include a coupling mass (18) rigidly bonded to the second portion (17b) of the calibration plate (17) and capacitively coupled to the calibration electrode (20).

[0074] The gyroscope may comprise at least one sensing electrode (13), the at least one sensing electrode (13) being arranged on a face (6a) of the support structure (6) and facing the sensing mass (3) and being capacitively coupled to the sensing mass (3), wherein the sensing mass (3) may be arranged between the sensing electrode (13) and the calibration structure (5) along a sensing direction (DS).

[0075] Both the driving direction (DD'; DD") and the sensing direction (DS'; DS") may be parallel to the face (106a; 206a) of the support structure (106; 206a).

[0076] The calibration structure (105; 206) may have a first side (105a; 205a) facing a side of the sensing mass (103; 203) and spaced apart from the sensing mass (103; 203) by a gap (121; 221), and a calibration electrode (120; 220) facing a second side (105b; 205b) of the calibration structure (105; 205) opposite the first side (105a; 205a).

[0077] The calibration structure (105; 205) is movable relative to the sensing mass (103; 203) along a sensing direction (DS'; DS").

[0078] The gyroscope may include at least one sensing electrode (113; 213), the at least one sensing electrode (113; 213) being fixed to a support structure (106; 206), wherein the sensing mass (103; 203) may be frame-shaped and the sensing electrode (113; 213) may be capacitively coupled to respective sides of the sensing mass (103; 203).

[0079] The sensing electrode (113; 213) may be arranged inside the sensing mass (102; 203).

[0080] The gyroscope may include a drive mass (201) movable relative to a support structure (206) along a drive direction (DD"), and a sensing mass (203) constrained by the drive mass (201) so as to be dragged by the drive mass in the drive direction (DD") and movable relative to the drive mass (201) along a sensing direction (DS").

[0081] The gyroscope may comprise a cover (7; 107; 207) connected in an airtight manner to a support structure (6; 106; 206) to form an airtightly closed chamber (8; 108; 208) between the cover (7; 107; 206) and the support structure (6; 106; 206), wherein a sensing mass (3; 103; 203) and a calibration structure (5; 105; 205) may be accommodated inside the chamber (8; 108; 208).

[0082] The electronic system can be summarized as including a processing unit (402) and a gyroscope (1; 100; 200).

[0083] A method for compensating for output thermal drift in a microelectromechanical gyroscope, the microelectromechanical gyroscope being summarized as comprising: a support structure (6; 106; 206); and a sensing mass (3; 103; 203) coupled to the support structure (6; 106; 206) with a degree of freedom along a drive direction (DD; DD'; DD") and a sensing direction (DS; DS') perpendicular to each other; and a calibration structure (5; 105; 205) facing the sensing mass (3; 103; 203) and aligned with the sensing mass (3; 1 03; 203) is spaced apart by a gap (21; 121; 221) having an average width (W; W'; W"); the method comprises arranging a calibration structure (5; 105; 205) facing the sensing mass (3; 103; 203) and spaced apart from the sensing mass (3; 103; 203) by a gap (21; 121; 221) having an average width (W; W'; W"); and moving the calibration structure (5; 105; 205) to change the average width (W; W'; W") of the gap (21; 121; 221).

[0084] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above detailed description. Generally speaking, in the appended claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments claimed and the full scope of their equivalents. Therefore, the claims are not limited by the present disclosure.

Claims

1. A micro-electromechanical system gyroscope comprising: Support structure; a sensing mass coupled to the support structure with a degree of freedom along a drive direction and a sensing direction, the drive direction and the sensing direction being perpendicular to each other; a calibration structure facing the sensing mass and spaced apart from the sensing mass by a gap having an average width, the calibration structure being movable relative to the sensing mass such that displacement of the calibration structure causes a change in the average width of the gap; as well as A calibration actuator is configured to control a relative position of the calibration structure with respect to the sense mass and the average width of the gap.

2. The gyroscope of claim 1 , wherein the calibration actuator comprises: a calibration electrode disposed on the support structure and capacitively coupled to the calibration structure; and a bias source coupled to the calibration electrode.

3. The gyroscope according to claim 2, wherein: The driving direction is parallel to a face of the support structure, and the sensing direction is perpendicular to the face and perpendicular to the driving direction; and The calibration structure is connected to a fulcrum portion fixed to the support structure, and the calibration structure rotates about a fulcrum axis that is parallel to the plane and perpendicular to both the driving direction and the sensing direction.

4. The gyroscope according to claim 3, wherein: The calibration structure includes a calibration plate coupled to the fulcrum portion and having a first portion and a second portion opposed about the fulcrum portion; and The first portion faces the sensing mass on a side of the sensing mass opposite the support structure and is spaced apart from the sensing mass by the gap.

5. The gyroscope of claim 4 , wherein the calibration structure comprises: A coupling proof-mass is rigidly joined to the second portion of the calibration plate and capacitively coupled to the calibration electrode.

6. The gyroscope according to claim 3, comprising: At least one sensing electrode is arranged on the face of the support structure, facing the sensing mass and capacitively coupled to the sensing mass, and wherein the sensing mass is arranged between the sensing electrode and the calibration structure along the sensing direction.

7. The gyroscope of claim 2, wherein the drive direction and the sense direction are both parallel to a face of the support structure.

8. The gyroscope of claim 7 , wherein the calibration structure has a first side that faces a side of the sense mass and is separated from the sense mass by the gap, and wherein the calibration electrode faces a second side of the calibration structure that is opposite the first side.

9. The gyroscope of claim 7, wherein the calibration structure is movable relative to the sensing mass along the sensing direction.

10. The gyroscope according to claim 7, comprising: At least one sensing electrode is fixed to the support structure, and wherein the sensing mass is frame-shaped and the sensing electrodes are capacitively coupled to respective sides of the sensing mass. The gyroscope according to claim 10 , wherein the sensing electrode is arranged inside the sensing mass.

12. The gyroscope according to claim 7, comprising: a drive mass movable relative to the support structure in the drive direction, and wherein the sensing mass is constrained by the drive mass so as to be dragged by the drive mass in the drive direction and movable relative to the drive mass in the sensing direction.

13. The gyroscope according to claim 1, comprising: A cover is joined to the support structure in an airtight manner to form an airtight closed chamber between the cover and the support structure, and wherein the sensing mass and the calibration structure are accommodated in the chamber.

14. A method for compensating for output thermal drift in a micro-electromechanical system gyroscope, comprising: arranging a calibration structure of the micro-electro-mechanical gyroscope facing a sensing mass of the micro-electro-mechanical gyroscope and spaced apart from the sensing mass by a gap having an average width; The calibration structure is moved to change the average width of the gap.

15. The method of claim 14, wherein moving the calibration structure to change the average width of the gap comprises: The calibration plate of the calibration structure is rotated in a counterclockwise direction, thereby rotating a first portion of the calibration plate toward a sense mass of the micro-electro-mechanical gyroscope and a second portion of the calibration plate away from a calibration electrode of the micro-electro-mechanical gyroscope.

16. The method of claim 14, wherein moving the calibration structure to change the average width of the gap comprises: The calibration plate of the calibration structure is rotated in a clockwise direction, thereby rotating a first portion of the calibration plate away from the sensing mass of the micro-electro-mechanical gyroscope and rotating a second portion of the calibration plate toward the calibration electrodes of the micro-electro-mechanical gyroscope.

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