Mechanically amplified high-precision and high-stability angular rate sensor

Abstract

Architecture and methods for constructing MEMS-based angular rate sensors of high precision, high stability are provided. The structure includes implementations that allow suppression of in-phase movement of coupled masses, mechanical enhancement of drive movement in a drive block, and mechanical enhancement of Coriolis effect induced movement in a sense block. The proposed architecture minimizes the mechanical momentum generated by the actuation forces in the drive, sense, and Q compensation blocks compared to the prior art. In addition, the method includes several implementations for achieving stress decoupling between the MEMS device and the environment and reducing anchor damping.

Description

Technical Field

[0001] Aspects of the present invention generally relate to the design and fabrication of angular rate sensors (ARS). More specifically, aspects of the present invention are directed to microelectromechanical systems (MEMS) vibratory gyroscopes for tactical and navigation-grade applications. Background Art

[0002] US 2010 / 0313657 A1 and US 11,118,907 B2 disclose examples of prior art devices that are very large, posing challenges to manufacturing and effective function. The proof mass and other device elements, which should be rigid, become flexible in out-of-plane directions, thereby compromising device function. Another shortcoming of such prior art devices is that the drive and sense modes are not fully decoupled. Furthermore, these devices are prone to quadrature errors caused by residual orthogonal drive motion inherent in the mechanical couplings between the various proof masses and levers shown. For example, US 11,118,907 B2 shows a U-shaped decoupled flexure that fails to eliminate residual orthogonal motion, leading to quadrature errors.

[0003] US20140260615A1 describes a lever having four initially parallel rigid beams connected by flexible joints. The lever dampens the in-phase movement of a vibrating element.

[0004] WO2022248647A1 describes a dual-mass device that partially addresses the aforementioned issues. However, in the disclosed arrangement, the mechanical momentum associated with the actuation forces within the drive and quadrature compensation masses becomes a secondary source of uncompensated quadrature error. Consequently, the drive and detection masses are not properly aligned.

[0005] Aspects of the present invention solve the problems of the prior art. Summary of the Invention

[0006] The invention is defined in the accompanying set of claims. Further aspects / embodiments / examples not included in the invention are also described.

[0007] Aspects of the present invention relate to dual-mass and quad-mass tuning fork angular rate sensors that address limitations of and improve upon the prior art.

[0008] The device measures angular rate about the Z-axis. It includes a substrate that defines a "reference surface" or "reference plane." The Z-axis is defined as the axis perpendicular to the reference plane. Conveniently, the reference plane is the plane of the wafer on which the MEMS structure (mass, beams, frame, anchors, etc.) is fabricated.

[0009] According to an independent aspect, there is provided a dual-mass micro-electromechanical system (MEMS) device for measuring Z-axis angular rate according to claim 1 .

[0010] Advantageously, the paired mechanical amplifiers can be configured to provide linearly coupled, amplified anti-phase drive mode motion and balanced to minimize energy dissipation to the substrate, resulting in increased drive mode quality factor, improved stability of the drive mode motion, and improved angular random walk of the device.

[0011] Advantageously, the additional mechanical amplifier can be configured to provide linearly coupled, amplified anti-phase sense mode motion and balanced to minimize energy dissipation to the substrate, resulting in increased sense mode quality factor, increased rate sensitivity, increased signal-to-noise ratio, and improved angular random walk of the device.

[0012] According to a subsidiary aspect of the present invention, there is provided a four-mass micro-electromechanical system (MEMS) device for measuring Z-axis angular rate, the device being implemented by mechanically connecting two dual-mass devices as defined above, to advantageously achieve better performance, improved stability and improved suppression of vibration and linear acceleration (reduced ARW).

[0013] It will be appreciated that the mass of the shuttle block is minimised without affecting its mechanical rigidity.

[0014] Suppressing the in-phase motion of the proof mass means that the anti-phase motion is retained as the fundamental resonant mode of the system, which significantly improves bias stability and ARW. In this configuration, the drive mode corresponding to the anti-phase motion of the proof mass is the fundamental mode. The function of the drive structure is to excite and maintain the drive mode oscillation at a predefined, stable amplitude.

[0015] Because the stability of the drive mode amplitude is directly related to the stability of the ARS, accurately measuring this amplitude is crucial for high-precision, high-stability devices. For devices with a frame according to the first aspect of the invention, the structure that provides mechanical amplification of the drive mode motion allows for better signal-to-noise ratio within the block that controls the drive mode amplitude. Conveniently, the same mechanical amplifier also suppresses in-phase movement of the frame, and therefore the proof mass.

[0016] "Coriolis-induced movement" refers to the vibrational motion of the proof mass produced by the Coriolis force, which is perpendicular to both the drive motion and the angular rate vector, and therefore occurs in the Y direction. "Sensed motion" refers to the Coriolis-induced motion of the proof mass and the motion of the sense shuttle, which is conveniently amplified and translated back into the X direction.

[0017] Advantageously, these devices include a mechanical structure that amplifies the Y-direction movement of the proof mass caused by the Coriolis effect into the X-direction movement of the sensing shuttle. The amplification mechanism has many advantages: i. It suppresses the parasitic in-phase movement of the proof mass and the sense shuttle, thereby highly rejecting all common-mode signals originating from the environment, such as shock and vibration; ii. It amplifies the mechanical Coriolis movement, thereby improving several key performance parameters of the device, such as sensitivity and ARW; iii. It reduces the sensing actuation force required to counteract the Coriolis force, providing particular advantages for devices operating in closed loop; and iv. It converts the Y-direction movement caused by the Coriolis effect into an X-direction sensing movement, which is not possible with prior art components (including, for example, known levers).

[0018] Point iv is a particular benefit over prior art devices because the mechanical structure provides better mechanical decoupling between the sensing motion and the driving motion, better vibration suppression, and better linewidth control in the DRIE process and therefore better geometry control during manufacturing.

[0019] Advantageously, in the absence of Z-axis angular rate, the drive mode and sense mode are decoupled from each other such that when one mode is excited, the other mode is not affected.

[0020] The drive shuttle mass is mechanically constrained to move in the drive mode direction (X). On the slave side, the first pair of vibrating structures are mechanically connected via at least one in-phase motion suppression element. This suppression element may also include other components, such as a spring that allows rotation about the Z axis. The inclusion of at least one suppression element has the advantage of suppressing the in-phase motion of the proof mass, meaning that this mode is forced to move to a relatively high frequency. In contrast, in known devices (e.g., the Sensonor SAR10, SAR100, and SAR500 devices), in-phase motion is often the fundamental mode, and therefore, it is unintentionally excited and acts as a parasitic oscillation, which degrades performance.

[0021] Preferably, the drive mode and the sense mode are parallel to the reference plane.

[0022] The device represents a tuning fork vibrating gyroscope with decoupled drive and sense modes, and combines in-plane linear motion for both the drive and sense modes. "In-plane" motion refers to motion that occurs within or parallel to a reference plane. This is in contrast to "out-of-plane" motion that occurs outside the reference plane. In-plane linear drive and sense motion offers a number of advantages over out-of-plane alternatives. In particular, the in-plane linear drive and sense motion of the angular rate sensor allows for large motion amplitudes, advantageously achieving much higher sensitivity to Coriolis forces than out-of-plane alternatives. Furthermore, all devices that use out-of-plane motion inherently suffer from out-of-plane unbalanced momentum acting on the mechanical structure.

[0023] Further dependent aspects are provided in the claims.

[0024] By mechanically connecting two such devices, an improved four-mass angular rate sensor device can be obtained. Such a device advantageously has better performance than its two-mass equivalent, with improved stability and improved suppression of vibration and linear acceleration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Hereinafter, the present invention and additional examples will be described in detail with reference to the accompanying drawings, in which: Figure 1 A schematic diagram of a dual-mass angular rate sensor is shown, which includes a mechanical amplifier for both drive motion and Coriolis motion.

[0026] Figure 2 Illustration of the mechanical amplifier that drives the motion.

[0027] Figure 3 Diagram showing a mechanical amplifier of Coriolis motion.

[0028] Figure 4 The general geometry of the mechanical amplifier employed is illustrated.

[0029] Figure 5 Shown is a schematic diagram of a dual-mass angular rate sensor with a mechanical amplifier for the Coriolis motion.

[0030] Figure 6 A practical implementation of a dual-mass angular rate sensor including a mechanical amplifier for Coriolis motion according to aspects of the invention is shown.

[0031] Figure 7 A schematic diagram of a four-mass angular rate sensor is shown, which includes mechanical amplifiers for both drive and Coriolis motion.

[0032] Figure 8An implementation of a four-mass angular rate sensor is shown, with mechanical amplifiers for both drive and Coriolis motion.

[0033] Figure 9 Shown is a schematic diagram of a four-mass angular rate sensor with a mechanical amplifier for the Coriolis motion.

[0034] Figure 10 Shown is a diagram depicting the drive motion configuration from Figure 7 Schematic diagram of the device.

[0035] Figure 11 Shown is a diagram depicting a sensory motion configuration from Figure 7 Schematic diagram of the device.

[0036] Figure 12 Shown for Figure 7 FEM simulation of the actuation motion of the device shown in FIG.

[0037] Figure 13 Shown for Figure 7 FEM simulation of the sensing motion of the device shown in FIG.

[0038] Figure 14 Shown is a diagram depicting the drive motion configuration from Figure 5 Schematic diagram of the device.

[0039] Figure 15 Shown is a diagram depicting a sensory motion configuration from Figure 5 Schematic diagram of the device.

[0040] Figure 16 Shown for Figure 5 FEM simulation of the actuation motion of the device shown in FIG.

[0041] Figure 17 Shown for Figure 5 FEM simulation of the sensing motion of the device shown in FIG.

[0042] Figure 18 An embodiment of a mechanical amplifier of Coriolis motion is shown.

[0043] Figure 19 A schematic diagram of the drive mode lever is shown.

[0044] Figure 20 An example of an actuating lever movable pivot is shown.

[0045] Figure 21 An example of a drive lever fixed pivot is shown.

[0046] Figure 22 An example of an anchor point damping reduction structure is shown.

[0047] Figure 23 Shown are the electrical blocks within a dual-mass angular rate sensor including a mechanical amplifier for the Coriolis motion.

[0048] Figure 24 Shown are the electrical blocks within a four-mass angular rate sensor including mechanical amplifiers for both drive and Coriolis motion.

[0049] Figure 25 A preferred embodiment of a comb drive for drive and sense mode actuation and detection is shown.

[0050] Figure 26 A preferred embodiment of a comb drive for a quadrature compensation block is shown.

[0051] Figure 27 A preferred embodiment of a comb drive for the frequency adjustment block is shown.

[0052] Figure 28 A C-SOI wafer is shown as the preferred starting material for fabricating the device.

[0053] Figure 29 A general cross-sectional view of a micromachined C-SOI wafer is shown.

[0054] Figure 30 FIG. 4 shows an overall cross-sectional view of the completed angular rate sensor. DETAILED DESCRIPTION

[0055] A first embodiment of the present invention comprises a dual-mass architecture that includes a mechanical amplifier for both drive mode motion and Coriolis motion, thereby addressing several limitations of conventional single-axis MEMS angular rate devices.

[0056] A second embodiment of the present invention comprises a quad-mass architecture that includes mechanical amplifiers for both drive-mode and Coriolis motion. This is achieved by coupling two dual-mass devices according to the first embodiment to achieve complete symmetry, thereby providing complete suppression of external vibrations, shocks, and linear accelerations, as well as achieving a higher quality factor.

[0057] A third embodiment of the invention comprises a dual-mass architecture based on the preferred embodiment, which includes only a mechanical amplifier for the Coriolis motion, which is a compromise between size and performance.

[0058] A fourth embodiment of the present invention comprises a four-mass architecture with only a mechanical amplifier for the Coriolis motion. This is achieved by coupling two dual-mass devices according to the third embodiment to achieve complete symmetry, thereby providing complete suppression of external vibrations, shocks, and linear accelerations, as well as achieving a higher quality factor.

[0059] Figure 1 The diagram shows the measurement Z Mechanical schematic diagram of a first embodiment of a dual-mass MEMS device (100) for axial angular rate, including mechanical amplifiers (4) and (13) for both drive motion and Coriolis motion, where white circles represent movable pivots and black rectangles represent anchor points.

[0060] The device (100) comprises: a first pair of identical vibrating structures, namely an upper drive block 101 and a lower drive block 102, each block comprising a proof mass block 1, each proof mass block 1 being mechanically coupled to a drive shuttle block 2. The drive shuttle block 2 is electrostatically actuated in the drive mode direction ( X ) produces the drive mode motion of the proof mass 1. The first pair of vibrating structures are elastically connected to the synchronization "frames" 6 and 7 by frame couplings 9 so that the drive mode corresponds to the anti-phase movement of the proof masses, while the in-phase movement of the proof mass 1, the drive shuttle 2 and the frames 6, 7 is suppressed. It will be understood that by "frame" we mean any rigid element that can take any suitable shape. The frames 6, 7 are rigid and do not rotate like a lever (as opposed to a lever). Figure 5 In contrast to the embodiment described in , the frames 6, 7 are constrained to move only in a direction perpendicular to the drive pattern. Their movement is therefore solely translational, in contrast to the rotational movement of the lever.

[0061] The device (100) further comprises a second pair of identical vibration structures, namely a left sensing block 103 and a right sensing block 104, each of which comprises a sensing shuttle block 11. The first pair of vibration structures and the second pair of vibration structures are elastically coupled to each other by a mechanical structure 13, which converts the vibration caused by the Coriolis effect of the verification mass 1 into a sensed ... Y The movement is converted into the amplification of the sensing shuttle 11 X Move towards.

[0062] Each block is suspended above the substrate by sets of flexures, described later, which are in turn attached to the substrate by fixed anchors 17 (also called pedestals). This anchoring method via the pedestals rather than directly to the device frame allows the active elements of the device to be decoupled from mechanical stresses and strains induced by the environment or the assembly.

[0063] The driving shuttle 2 is mainly connected to the substrate through the main driving spring 5, connected to the proof mass 1 through the Y-direction guide spring 10, and connected to the outer synchronization frame 6 and the inner synchronization frame 7 through the mechanical amplifier formed by the rigid beam 4. The movement of the driving shuttle 2 is along X The axis is constrained by a guide flexible member 3. The guide flexible member 3 is conveniently realized as a multi-pronged spring tethered to the base 17.

[0064] The outer synchronization frame 6 and the inner synchronization frame 7 are connected to each other by a set of structures 9, which are designed so that the in-phase movement of the frames is suppressed. Y The movement of the shaft is limited by the guide flexible member 8. The guide flexible member 8 is conveniently realized as a multi-pronged spring tethered to the base 17.

[0065] The sensing shuttle 11 is coupled to the substrate primarily through the main sensing spring 14 and to the proof mass 1 through the mechanical amplifier beam 13 and the sensing mode movable pivot 15. X The movement of the shaft is limited by the guide flexibility 12. The guide flexibility 12 is conveniently realized as a multi-pronged spring tethered to the base 17.

[0066] The movable pivot 15 is constrained by the guide flexible member 16 to move only along Y The guide flexible member 16 is conveniently realized as a multi-pronged spring tethered to the base 17 .

[0067] The beam 4 as a whole forms a mechanical amplifier of the drive mode motion.In a similar manner, the beam 13 as a whole forms a mechanical amplifier of the Coriolis motion.

[0068] Figure 2 The operation of the drive blocks 101, 102 is shown schematically, illustrating the amplification of the drive mode motion. Y When the direction is applied to the outer synchronization frame 6 and the inner synchronization frame 7, it is conveniently arranged to Y The beam 4 forms a non-zero angle with the axis, forcing the shuttle block 2 to move along X The shuttle 2 forces the proof mass 1 to follow via the beam 10. Due to the geometry of the system, as will be shown below, the shuttle 2 X The shaft displacement 20 is greater than the synchronous frame 6, 7 Y Axis displacement 21.

[0069] Furthermore, the frame coupler 9 connecting the synchronization frames 6 and 7 is designed to inhibit the in-phase movement of the frames. In a preferred embodiment of the frame coupler 9, the movable pivot 18 of the frame coupler 9 is constrained to move only in phase by a set of flexible members tethered to the base 17. XThe synchronization frames 6 and 7 and the frame coupling 9 ensure that the drive blocks 101 and 102 move in opposite phases.

[0070] Figure 3 A preferred embodiment of a structure for mechanically amplifying Coriolis motion is schematically illustrated. The structure comprises: - Four symmetrically arranged rigid beams 13, each beam 13 and Y The axes form a non-zero angle. Each beam 13 is attached to the proof mass 1 and the sensing shuttle 11. The length is L The beam is rigid under normal operating conditions, but its joints are flexible, allowing the Coriolis force (along the Y axis) or by sensing an electrostatic force (along the X axis) changes the internal angle when loaded; - A paired main sensing spring system 14 which limits the connection of the connector to the sensing shuttle block 11 to only X Movement of axes; and - Two pairs of pivot Y-direction guide springs 16 which restrict the two movable pivots 15 connected to the proof mass 1 to move only in the direction Y Movement of the axis.

[0071] Due to the geometry of the spring and beam and the anchoring method, in-phase movement of the sensing shuttle 11 and the proof mass 1 is suppressed. In other words, the spring can be connected to a corresponding anchoring damping structure.

[0072] It will be appreciated that under normal operating conditions the movable pivot 15 is designed such that it allows the internal angle between the rigid beams 13 to vary.

[0073] In existence along Z In the case of an angular velocity of the axis, the Coriolis force will act on the proof mass in opposite directions due to the anti-phase driving motion of the proof mass 1, thereby pushing the movable pivot 15 in opposite directions along the Y axis. Y The movable pivot 15 is connected to the sensing shuttle block 11) and the main sensing spring 14, forcing the shuttle block 11 to move along the axis of the sensor. X Due to the geometry of the system, as will be shown below, the shuttle block 11 X Axis displacement greater than the proof mass 1 and the movable pivot 15 Y In addition, the mechanical amplifier shown also suppresses the movement of the sensing shuttle 11 along the X The in-phase movement of the verification mass block 1 along the Y Direction of in-phase movement.

[0074] A key requirement for the proper function of the mechanical amplifier is to constrain the movable pivot 15 to move only along YThis can be achieved by using a Y-direction guide spring 16 tethered to the base 17. The Y-direction guide spring 16 allows Y direction of bending, but for the X The force in the direction has an elastic force that resists it.

[0075] Figure 4 The method of calculating the amplification factor of the preferred mechanical amplifier is shown. Assuming that the beam 13 remains rigid (maintains its length L ), geometrically, a small vertical displacement y (21) of the movable pivot 15 corresponds to an amplified displacement x (20) of the sensing shuttle 11, where θ is the angle of rest between the rigid beam 13 and the Y direction:

[0076] As a typical example, for the angle θ =15°, and the magnification factor ζ=x / y =3.73 is obtained.

[0077] refer to Figure 4 , it will be understood that the balance of forces means that:

[0078] Preferably, for simplicity, the mechanical amplifier of the drive mode motion 4, the mechanical amplifier of the Coriolis motion 13 and the frame coupler 9 are designed in a similar manner. In a subordinate aspect of the invention, these three mechanical structures can be designed and optimized independently.

[0079] Figure 5 A mechanical schematic diagram of a second embodiment of a dual-mass MEMS device (110) for measuring Z-axis angular rate is shown, which only includes a mechanical amplifier (13) for Coriolis motion. Figure 5 The device comprises a first pair of identical vibrating structures, namely an upper drive mass 101 and a lower drive mass 102. Each of the upper drive mass 101 and the lower drive mass 102 includes a proof mass 1, each mechanically coupled to a drive shuttle mass 2. Drive shuttle mass 2 generates a drive mode motion of proof mass 1 in the drive mode direction (X) via electrostatic actuation. The first pair of vibrating structures 101, 102 are elastically connected by a synchronization lever 22, which is attached to the substrate via a fixed pivot 23. The fixed pivot only allows rotation about the Z axis, resulting in a drive mode corresponding to anti-phase movement of proof mass 1, while in-phase movement of proof mass 1 and drive shuttle mass 2 is suppressed.

[0080] The device further includes a second pair of identical vibrating structures, namely a left sensing mass 103 and a right sensing mass 104 , each of which includes a sensing shuttle mass 11 .

[0081] The first pair of vibration structures and the second pair of vibration structures are elastically connected to each other through a mechanical structure 13, which verifies that the Coriolis effect of the mass block 1 Y The movement is converted into the amplification of the sensing shuttle 11 X Move towards.

[0082] The drive shuttle block 2 is coupled to a synchronization lever 22 via a drive-lever movable pivot 19, which allows translational movement of the drive shuttle block 2 along the X-axis and rotational movement of the lever 22 about the Z-axis.

[0083] like Figure 5 The embodiment shown does not use a mechanical amplifier for the drive mode motion and uses levers instead of frames to achieve synchronization of the drive masses. The result may be reduced device performance, but the advantage is a smaller size.

[0084] Figure 6 Pictured Figure 5 A practical implementation of the embodiment of the dual-mass MEMS device 110 shown in FIG.

[0085] Figure 7 The schematic diagram of a four-mass MEMS angular rate sensor 200 is shown, which includes a mechanical amplifier for both drive motion and Coriolis motion. The device is mechanically connected to two dual-mass devices 100 with a frame (shown in FIG. Figure 1 ) is achieved to advantageously obtain better performance, improved stability and improved suppression of vibration and linear acceleration. Mechanical coupling and synchronization are achieved by rigidly connecting the sensing connection beam 24 of the innermost sensing shuttle block 11.

[0086] Figure 8 Shown Figure 7 A practical implementation of the four-mass MEMS device 200 is shown in FIG.

[0087] Figure 9 The diagram shows a schematic diagram of a four-mass MEMS angular rate sensor 210 having only a mechanical amplifier for the Coriolis motion, which is mechanically connected to two dual-mass devices 110 with levers (shown in FIG. Figure 5 ) is achieved to advantageously obtain better performance, improved stability and improved suppression of vibration and linear acceleration. Mechanical coupling and synchronization are achieved by a drive connection spring 25 connecting the innermost drive shuttle block 2 and a sense connection spring 26 connecting the innermost sense shuttle block 11.

[0088] Figure 10 The dual-mass device 100 with a frame is depicted in a drive mode configuration (shown in FIG. Figure 1 ), clearly illustrating the anti-phase movement of the two proof masses 1 and the drive shuttle 2, the deformed main drive spring 5, the vertically displaced synchronization frames 6 and 7, and the deformed frame connector 9.

[0089] Advantageously, the Coriolis mechanical amplifier 13 and the sensing shuttle block 11 are conveniently left undisturbed, ie the sensing mode is mechanically decoupled from the driving mode.

[0090] Frames 6 and 7 allow the two drive blocks 101 and 102 to be synchronized. Guide flexure 8 constrains frames 6 and 7 along Y Movement of the axis.

[0091] The movable pivot 15 allows the proof mass 1 to move along X The linear movement of the axis does not interfere with the Coriolis mechanical amplifier 13.

[0092] Figure 11 The dual-mass device 100 (shown in FIG. 1 ) with a frame depicted in a sensing mode configuration is shown. Figure 1 ), which clearly illustrates the anti-phase movement of the two verification masses 1 and the sensing shuttle 11, the deformed main sensing spring 14, the sensing pivot Y-direction guide spring 16 and the verification mass Y-direction guide spring 10, and the vertically displaced pivot 15.

[0093] The drive shuttle block 2 and the synchronizing frames 6 and 7 are conveniently kept undisturbed, ie the drive mode is mechanically decoupled from the sense mode.

[0094] The rigid beam 13 and the main sensing spring 14 allow the two sensing masses 103 and 104 to be synchronized.

[0095] Figure 12 Shown Figure 7 and Figure 8 FEM simulation of the driven motion of the four-mass device 200 with frame illustrated in . To better visualize the deformation, the fixed electrodes have been removed and the deformation has been exaggerated.

[0096] Figure 13 Shown Figure 7 and Figure 8 FEM simulation of the sensed motion of the four-mass device 200 with frame illustrated in . To better visualize the deformation, the fixed electrodes have been removed and the deformation has been exaggerated.

[0097] Figure 14 A dual-mass device 110 with a lever is depicted in a drive mode configuration (shown in FIG. Figure 5) is a mechanical schematic diagram, which clearly illustrates the anti-phase movement of the two verification masses 1 and the drive shuttle block 2, the deformed main drive spring 5 and the rotating synchronization lever 22.

[0098] The Coriolis mechanical amplifier 13 and the sensing shuttle block 11 are conveniently left undisturbed, ie the sensing mode is mechanically decoupled from the driving mode.

[0099] The lever 22 allows synchronization of the two drive masses 101 and 102. The fixed pivot 23 is tethered to the center of the pivot 22, which only allows rotation about the Z axis.

[0100] The movable pivot 19 allows rotation of the lever 22 without interfering with the linear movement of the drive shuttle block 2 along the X-axis.

[0101] The movable pivot 15 allows linear movement of the proof mass 1 along the X-axis without disturbing the Coriolis mechanical amplifier 13 .

[0102] Figure 15 A dual-mass device 110 with a lever (shown in FIG. Figure 5 ), which clearly illustrates the anti-phase movement of the two verification masses 1 and the sensing shuttle 11, the deformed main sensing spring 14, the sensing pivot Y-direction guide spring 16 and the verification mass Y-direction guide spring 10, and the vertically displaced pivot 15.

[0103] The drive shuttle block 2 and the synchronising lever 22 are conveniently left undisturbed, ie the drive mode is mechanically decoupled from the sense mode.

[0104] The rigid beam 13 and the main sensing spring 14 allow the two sensing masses 103 and 104 to be synchronized.

[0105] Figure 16 Shown Figure 5 and Figure 6 FEM simulation of the driven motion of the dual-mass device 110 with lever illustrated in . In order to better visualize the deformation, the fixed electrodes have been removed and the deformation has been exaggerated.

[0106] Figure 17 Shown Figure 5 and Figure 6 FEM simulation of the sensed motion of the dual-mass device 110 with lever illustrated in . To better visualize the deformation, the fixed electrodes have been removed and the deformation has been exaggerated.

[0107] Figure 18 The preferred design of the Coriolis mechanical amplifier 13 according to the present invention is shown. Advantageously, the main drive spring 5 allows the proof mass 1 to move along XThe movable pivot 15 is constrained by the Y-direction guide spring 16 to move only along the Y In the presence of a Coriolis force acting along the Y axis, the movable pivot 15 pushes or pulls the rigid beam 13, which in turn moves along the X The shaft pushes or pulls the sensing shuttle 11 , loading the main sensing spring 14 at the same time.

[0108] The main sensing spring 14 and the guide flexible member 12 (see Figure 6 ) together constrain the two sensing shuttle blocks 11 to only move along X Advantageously, the springs 12, 14 and 16 are implemented as multi-pronged springs tethered to the base 17 to reduce stress levels and anchor point losses, thereby significantly improving the reliability and performance of the device.

[0109] For manufacturing purposes, in order to accurately control the dry etching process, a filling surface 28 is inserted. The filling surface 28 is tethered to the substrate by means of the pedestal 17.

[0110] Figure 19 A schematic diagram of a synchronous lever 22 according to an alternative embodiment of the invention (devices with levers 110 and 210) is shown. The lever 22 is tethered to the substrate by a fixed pivot 23 which only allows the fixed pivot to be moved about Z In order to decouple the rotational motion of the lever 22 from the linear movement of the drive shuttle block 2, the drive-lever pivots 19 have been designed and implemented. These drive-lever pivots 19 greatly reduce the rotational motion of the lever 22 along the Y The force exerted by the shaft on the drive shuttle block 2 FDy , this force may still result in a quadrature error signal despite the presence of a guide flexure for driving the shuttle block 3. Note that the implementation illustrated here is based on a similar design by the same author but submitted separately.

[0111] Figure 20 The preferred design of the drive-lever pivot 19 and the guide flexibility for the drive shuttle block 3 according to an alternative embodiment of the invention (devices with levers 110 and 210 ) is shown.

[0112] Figure 21 The preferred design of the lever fixing pivot 23 according to the alternative embodiment of the invention (devices 110 and 210 with levers) is shown. A set of at least 4 but preferably 6 "S" shaped springs 27 (each tethered to the substrate at one end) allows the lever 22 to move about Z The axis rotates while all translation is suppressed. A shock absorber 28 designed as a flexible cantilever beam with a stop is added to limit the rotation of the lever to a maximum value, thus protecting the device from large external mechanical shocks.

[0113] Applicable to all embodiments described herein, Figure 13 An innovative anchor point damping reduction structure 30 is shown in accordance with an embodiment of the present invention. Rather than directly connecting the movable universal spring 29 to its corresponding anchor point 17, a set of transverse restraining beams 31 are introduced to move the clamping / fixing surface of the universal spring 29 away from the anchor point 17, thereby reducing the energy transferred through the underside of the anchor point surface. Furthermore, a set of beams 32 are used to reduce the direct attachment area between the universal spring 29 and the anchor point 17, further reducing anchor point-related losses.

[0114] Figure 23 and Figure 24 The locations of the various electrical blocks are shown within a dual-mass device with a lever 110 and a four-mass device with a frame 200 , respectively.

[0115] The drive shuttle blocks 2 each include a drive actuation block 501 and a drive detection block 502 , wherein the former is used to electrostatically drive the first pair of vibrating structures (tines 101 and 102 ) into anti-phase oscillation, and the latter is used to measure / quantify the amplitude of the oscillation.

[0116] For the four-mass device 200 with a frame, the drive actuation block 501 is located on the outer synchronization frame 6 , while the drive detection block 502 is conveniently located on the drive shuttle block 2 .

[0117] For the dual-mass device with frame 110, both the drive actuation mass 501 and the drive detection mass 502 are located on the drive shuttle mass 2, aligned along the central horizontal axis of the proof mass 1. In an alternative embodiment of the present invention, the drive actuation mass and the drive detection mass can be combined into a single mass that will operate in a time-multiplexed mode, most of the time as an electrostatic actuator and part of the time as a capacitive amplitude detector.

[0118] In contrast to the prior art, these particular arrangements do not introduce undesirable mechanical momentum associated with drive mode motion.

[0119] Each sensing shuttle block 11 includes a sensing actuation block 503 and a sensing detection block 504, wherein the former is used to electrostatically cancel / balance the movement of the sensing vibrating structures 103 and 104, while the latter is used to measure / quantify the amplitude of the residual oscillation. In an alternative embodiment of the present invention, the sensing actuation block and the sensing detection block can be combined into a single block, which will operate in a time-multiplexed mode, acting as an electrostatic actuator most of the time and as a capacitive amplitude detector part of the time.

[0120] In addition, each proof mass 1 includes a pair of quadrature error compensation blocks 505 , which can electrostatically compensate for the quadrature error.

[0121] Furthermore, for devices operating in mode matching, the sensing shuttle block 11 includes at least one frequency adjustment block 506 that is capable of adjusting the electrostatic damping until the sensing mode frequency matches the driving mode frequency.

[0122] As previously mentioned, and regardless of the actual implementation, these devices employ electrostatic actuation and capacitive sensing to generate and detect motion of various components. Figure 25 A preferred embodiment of a comb drive 35 for drive and sense mode actuation and detection is shown. It consists of fixed electrodes 33 (anchored to the substrate via base 17) and movable electrodes 34 (attached to the drive and sense shuttle blocks).

[0123] like Figure 25 As shown, an area closing scheme is preferred, wherein the common area between the comb fingers changes during movement. In an alternative embodiment of the present invention, a gap closing scheme may be employed, wherein the gap between the comb fingers changes.

[0124] The device can use an electrostatic quadrature compensation block 505, such as Figure 26 Block 505 comprises a set of comb drives 35, each having a fixed electrode 33 (anchored to the substrate via a base 17) and a movable electrode 34 (attached to the proof mass 1). Within the designed operating range, block 505 eliminates any residual quadrature error that may still exist.

[0125] The device also employs a frequency adjustment block 506, such as Figure 27 As shown. Block 506 consists of a set of combs 35, each having a fixed electrode 33 (anchored to the substrate via a base 17) and a movable electrode 34 (attached to the sense shuttle block 11). Block 506 electrostatically damps the sense mode motion in a controlled manner, thereby adjusting its resonant frequency downward to match the drive mode frequency for mode-matched operation.

[0126] consider Figure 28 And regardless of which embodiment is chosen, the preferred starting material for fabricating the device is a cavity SOI (C-SOI) wafer 300, which consists of a substrate or handle wafer 301, a device layer 302, an insulating buried oxide (BOX) layer 303, a backside oxide layer 304 for controlling wafer bow and warpage, and a sealed cavity implemented in the substrate 305. The buried oxide layer 303 can be completely absent from the cavity, as shown, or present on the device layer or the substrate, or both.

[0127] Figure 29A generalized cross-sectional view of a micromachined C-SOI wafer is shown. Selected frontside metal layers 306 have been deposited and patterned to form electrical contacts and one side of the seal ring. Selected backside metal layers 307 have been deposited and optionally patterned to form electrical contacts to the substrate. DRIE is used to pattern the device layers in the region within the cavity to define DRIE trenches 308, mechanical structures 311 (combs, fingers, springs, proof masses, shuttles, levers, etc.), anchor points 310, and a die frame 309.

[0128] Figure 30 The overall cross-sectional view of the angular rate device after fabrication is shown. Figure 29 This is achieved by wafer-level bonding between the MEMS wafer 300 and a cover wafer 400 containing electrical wiring. At least one front-side oxide layer 401 is used to provide insulation between the various conductive elements. At least one selected front-side metal layer 402 has been deposited and patterned to form the electrical contacts and the second side of the seal ring, and to ensure the necessary signal routing from the electrodes on the MEMS wafer 300 to the device pads 403 on the cover wafer 400.

[0129] Description of Reference Signs 100 2-mass MEMS ARS structure with frame 110 2-mass MEMS ARS structure with lever 200 4-mass MEMS ARS structure with frame 210 4-mass MEMS ARS structure with lever 300 C-SOI wafer 400 covered silicon wafer 1 Verification mass 2 Drive shuttle block 3 Guide flexible piece for driving the shuttle block 4 Driver Amplifier Beam 5 Main drive spring 6 External synchronization framework 7 Internal synchronization framework 8 Flexible guide element for synchronization frame 9 Reverse frame connector 10 Verify the Y-direction guide spring of the mass block 11 Sensor shuttle block 12 Guide flexible piece for sensing shuttle block 13 Sense amplifier beam 14 Main sensing spring 15 Movable pivots for sensing mode 16 Pivot Y-direction guide spring 17 Anchor 18 Frame coupler pivot 19 Drive-Lever Pivot 20 Amplified displacement X 21 Source displacement Y 22 Synchronous Lever 23 Lever fixed pivot 24 Sensing beam 25 Drive connection spring 26 Sensing connection spring 27 Fixed pivot spring 28 Fixed pivot shock absorber 29 Universal Beam 30 Anchor point damping reduction structure 31 Transverse restraint beam 32 Beam with reduced anchorage area 33 Fixed electrode (stator) 34 movable electrodes 35 Drive / Sense Comb Driver 36 Q-compensated comb 37 F-Adjusting Comb 38 Filling Surface 101 Upper drive vibration structure 102 Lower drive vibration structure 103 Left sensing vibration structure 104 Right sensing vibration structure 300 C-SOI wafer 301 C-SOI handle wafer (substrate) 302 C-SOI device layer 303 buried oxide 304 back oxide 305 cavity 306 front metal 307 back metal 308 DRIE groove 309 chip frame 310 Anchor / Base 311 Mechanical Structure 312 Reference Plane 400 covered silicon wafer 401 Insulating Oxide 402 Metal Layers 1 and 2 403 pad 501 drive actuator block 502 drive detection block 503 sensing actuator block 504 sensing detection block 505 Q-Compensation Block 506 F-adjustment block

Claims

1. A dual-mass mechanically amplified micro-electromechanical sensor (MEMS) device for measuring Z-axis angular velocity, comprising: a first pair of vibrating structures (101, 102), the first pair of vibrating structures (101, 102) being connected by a rigid frame (6, 7) for structurally providing anti-phase movement of the vibrating structures at a first predetermined frequency, at which the in-phase movement of the first pair of vibrating structures is suppressed and the vibrating structures are synchronized, wherein the rigid frame (6, 7) is configured to move perpendicular to the direction of motion of the drive mode; a second pair of vibrating structures (103, 104), the second pair of vibrating structures (103, 104) being configured as a sense mode mechanism to provide balanced anti-phase movement toward a second predetermined frequency in a direction of sense mode motion in which in-phase movement of the second pair of vibrating structures is suppressed; a pair of mechanical amplifying structures (4) elastically coupling the first pair of vibrating structures to the rigid frame (6, 7) for amplifying movement of the first pair of vibrating structures in the direction of drive mode motion relative to movement of the rigid frame; and a further mechanical amplifying structure (13) elastically coupling the first pair of vibrating structures and the second pair of vibrating structures to amplify the movement caused by the Coriolis effect, The direction of movement in the sensing mode is parallel to the direction of movement in the driving mode.

2. The device according to claim 1, wherein The first pair of vibrating structures includes a first proof mass and a second proof mass, each mechanically coupled to a first drive shuttle mass and a second drive shuttle mass, respectively, the drive shuttle masses for producing a drive-mode movement of the proof mass in the direction of the drive-mode motion.

3. The device according to claim 1 or 2, wherein The second pair of vibration structures includes a first sensing shuttle block and a second sensing shuttle block.

4. The device according to claim 2 or 3, wherein The drive shuttle block is mechanically constrained by a flexure to move only in the direction of the drive mode motion.

5. A device according to any one of the preceding claims, wherein The sense shuttle is mechanically constrained by a flexure to move only in the direction of the sense mode motion.

6. A device according to any one of the preceding claims, wherein The further mechanical amplification structure comprises four symmetrically arranged rigid beams, each rigid beam forming a non-zero angle with the direction of the Coriolis effect induced motion of the proof mass (Y axis).

7. The device according to claim 6, wherein The rigid beams are connected to the surrounding blocks by elastic joints or pivots for changing the internal angles between the rigid beams relative to the blocks along the Y The axis of movement is magnified along the X Movement of the axis.

8. The device according to any one of claims 2 to 7, wherein The further mechanical amplification structure comprises a pivot connected to the proof mass and an anchor point by a first spring system.

9. The device according to any one of claims 3 to 8, wherein The additional mechanical amplification structure includes a pivot connected to the sensing shuttle and an anchor point by a second spring system.

10. A device according to any one of the preceding claims, wherein The first pair of vibrating structures includes a first plurality of electrodes for drive movement actuation and a second plurality of electrodes for drive movement amplitude detection.

11. A device according to any one of the preceding claims, wherein The first pair of vibrating structures includes a second plurality of electrodes configured to enable both the drive movement actuation and the drive movement amplitude detection by time multiplexing.

12. A device according to any one of the preceding claims, wherein The second pair of vibrating structures includes a first plurality of electrodes for sensing movement actuation and a second plurality of electrodes for sensing movement amplitude detection.

13. A device according to any one of the preceding claims, wherein The second pair of vibrating structures includes a plurality of electrodes configured to implement both the sensed movement actuation and the sensed movement amplitude detection through time multiplexing.

14. A device according to any one of the preceding claims, wherein The proof mass includes a plurality of electrodes configured to compensate for residual quadrature error.

15. A device according to any one of the preceding claims, wherein The sense shuttle block includes a plurality of electrodes configured to electrostatically down-tune a sensing frequency until a match with a driving frequency is achieved.

16. A device according to any preceding claim, further comprising an anchor point damping reduction structure.

17. The device according to claim 16, wherein The anchor point damping reduction structure includes a plurality of lateral restraining beams for blocking lateral vibrations of the spring and for reflecting sound waves associated with the vibratory movement of the spring.

18. The device according to claim 17, wherein The anchor point damping reduction structure further comprises at least one anchoring area reduction beam, preferably a plurality of anchoring area reduction beams.

19. An angular rate MEMS device system comprising two mechanically coupled devices according to any one of the preceding claims.

20. A method of manufacturing a device according to any preceding claim, the method using a cavity-SOI (CSOI) wafer and comprising performing a DRIE process within a device layer of the CSOI wafer.

21. The method according to claim 20, wherein The method also includes wafer-level bonding of the CSOI wafer, wherein the overlying silicon wafer includes electrical routing of signals and device pads.

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