# Patent

## Title
MEMS multi-axis gyroscope Z-axis electrode structure

## Abstract

Various examples include microelectromechanical die for sensing motion that includes symmetrical proof-mass electrodes interdigitated with asymmetrical stator electrodes. Some of these examples include electrodes that are curved around an axis orthogonal to the plane in which the electrodes are disposed. An example provides vertical flexures coupling an inner gimbal to a proof-mass in a manner permitting flexure around a horizontal axis.

## Background
CLAIM OF PRIORITY
This application is a continuation-in-part of and claims the benefit of priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/813,443, filed on Jan. 31, 2013, which is a U.S. National Stage Filing under 35 U.S.C. 371 from International Patent Application Serial No. PCT/US2011/052006, filed on Sep. 16, 2011, and published on Mar. 22, 2012 as WO 2012/037501 A2, which claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 61/384,247, entitled “LOW-QUADRATURE SUSPENSION SYSTEM FOR MULTI-AXIS GYROSCOPES,” filed Sep. 18, 2010 and U.S. Provisional Patent Application Ser. No. 61/384,512, entitled “IMPROVED QUADRATURE REDUCTION STRUCTURE FOR RESONATING MICROMACHINED DEVICES,” filed Sep. 20, 2010, each of which is incorporated by reference in its entirety.
This application also claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 61/593,691, entitled “MEMS MULTI-AXIS GYROSCOPE WITH CENTRAL SUSPENSION AND GIMBAL STRUCTURE,” filed on Feb. 1, 2012, which is incorporated by reference herein in its entirety.


BACKGROUND
Quadrature error is one of the primary factors that limit the performance of micromachined sensors such as gyroscopes. Considering the relative magnitudes of the drive and sense oscillations, even an extremely small part of the drive motion coupling into a sense-mode could dominate over the Coriolis response.
Practically, fabrication imperfections may result in less-than-ideal geometries in structures such as gyroscope structures. Less-than-ideal geometries can cause a drive oscillation to partially couple into a sense-mode. Even though several cross-coupling approaches exist, such as elastic, viscous and electrostatic coupling approaches, in certain cases the elastic coupling due to anisoelasticity in the suspension elements increases in magnitude beyond a desired level.
In sensor systems such as gyroscope systems with out-of-plane operational modes, anisoelasticity between the in-plane and out-of-plane directions is the dominating source of Quadrature error. Sidewall tilt or skew in deep reactive-ion etching (“DRIE”) can result in deviation of the cross-section of the flexure bearings from a rectangle to a parallelogram, causing the principle axes of elasticity of the suspension flexure bearings to deviate from parallel and orthogonal to the device surface. In an example, single or multi-axis micromachined sensor structures such as gyroscope structures can suffer from high-quadrature error caused at least in part by DRIE skew.
Additionally, prior resonators rely on simple straight flexure bearings to generate a flexing structure to allow the device to displace in resonance. This creates significant problems when etching creates a skew in the flexure bearing, causing large undesired displacement, often actuating a sense mechanism.



BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
FIG. 1 illustrates a sensor structure including a suspension structure, according to an example.
FIG. 2A illustrates a portion of a suspension, according to an example.
FIG. 2B illustrates the suspension of FIG. 8A, in a bending state in which a top portion is bent upward, in an example.
FIG. 2C illustrates the suspension of FIG. 8A, in a bending state in which a top portion is bent downward, in an example.
FIG. 3 illustrates torsional motion of a suspended structure about a Z-axis, according to an example.
FIG. 4 illustrates torsional motion of a suspended structure about an X-axis, according to an example.
FIG. 5 illustrates torsional motion of a suspended structure about a Y-axis, according to an example.
FIG. 6 illustrates a 2-Axis Gyroscope including a low quadrature error suspension, according to an example.
FIG. 7 illustrates a 3-Axis Gyroscope including a low quadrature error suspension, according to an example.
FIG. 8 illustrates quadrature error for an example suspension.
FIG. 9 illustrates a drive mode, according to an example.
FIG. 10 illustrates a four bend flexure bearing, according to an example.
FIG. 11 illustrates a flexure bearing including a flexing flexure bearing and a non-flexing flexure bearing, according to an example.
FIG. 12 illustrates a flexure bearing including a flexing flexure bearing shorter than the flexure bearing of FIG. 11, and a non-flexing flexure bearing shorter than the non-flexing flexure bearing of FIG. 11, according to an example.
FIG. 13A illustrates a suspension with large clearances, according to an example.
FIG. 13B illustrates stresses related to flexing of flexures bearings.
FIG. 14A illustrates a suspension including a switchback, according to an example.
FIG. 14B illustrates a sectional taken at 14B of FIG. 14A.
FIG. 14C illustrates a sectional taken at 14C of FIG. 14A.
FIG. 14D illustrates a sectional taken at 14D of FIG. 14A.
FIG. 15 illustrates the suspension of FIG. 14 flexed in torsion around a Z-axis, according to an example.
FIG. 16A illustrates the suspension of FIG. 14 flexed in torsion around a Z-axis, according to an example.
FIG. 16B illustrates the suspension of FIG. 14 flexed about a Y-axis, according to an example.
FIG. 16C illustrates the suspension of FIG. 14 flexed about the X-axis, according to an example.
FIG. 16D illustrates the suspension of FIG. 14 flexed in displacement along a Y-axis, according to an example.
FIG. 17 shows a method of making a low-quadrature-error suspension, according to an embodiment.
FIG. 18 shows a method of making vibration rejection z-axis electrodes, according to an embodiment.



DETAILED DESCRIPTION
Unwanted sidewall flex can negatively affect the performance of flexure bearings (“flexures”), such as flexure bearings that support one or more portions of a microelectromechanical systems (“MEMS”) structure such as a die. In an example, if one or more sidewalls have an angle error, an in-plane drive motion can cause out-of-plane motion, such as when the skew axis is along a flexure bearing or beam length. In an example, when skewed pliable or compliant flexure bearings or beams are located on opposite sides during a drive motion, a resulting out-of-plane deflection can cause or contribute to quadrature error. In an example, a low-quadrature suspension system aims at reducing or cancelling undesired out-of-plane motion.
FIG. 1 illustrates a sensor structure including a suspension structure, according to an example. Various examples disclose a low-quadrature suspension system for a sensor. In an example, a suspension structure can be utilized in a torsional multi-axis micromachined gyroscope system with a proof-mass such as a single proof-mass 104. In an example, a proof-mass 104 is suspended at its center with a single central anchor 106. In an example, one or more flexure bearings connect the anchor 106 to the proof-mass 104, such as to the proof-mass main frame 116. In an example, one or more flexures allow the proof-mass to oscillate torsionally about three perpendicular axes. In an example, suspension flexure bearings or beams provide in-plane and out-of-plane deflections, allowing the proof-mass to oscillate torsionally about the x, y, and z axes.
An example includes a fixed portion 118, wherein the anchor 106 is coupled to the fixed portion 118. In an example, a first nonlinear suspension member 108 is coupled to anchor 106 on a side of the anchor. In an example, a second nonlinear suspension member 120 coupled to the anchor on the same side of the anchor, the second nonlinear suspension member having a shape and location mirroring the first nonlinear suspension member about an anchor bisecting plane 122, such as a x-Z-plane. Various examples include a proof-mass 104 that is planar, the proof-mass suspended at least in part by the first nonlinear suspension member 108 and the second nonlinear suspension member 120 such that the proof-mass is rotable about the anchor 106 and is slideable in a plane parallel to the fixed portion, such as in the x-y plane.
In an example, a C-shaped flexure bearing 108 includes a inner portion 110 coupled to the anchor 106 and extending toward the anchor bisecting plane 122, a center portion 114 having a proximal portion and a distal portion, with a proximal portion coupled to the inner portion 110 and a distal portion extending away from the anchor 106 along the anchor bisecting plane 122 and coupled to a outer portion 112 extending away from the anchor bisecting plane 122. In an example, the center portion 114 is perpendicular the inner portion 110 and the outer portion 112. In an examples, the center portion 114 is parallel the anchor bisecting plane 122.
In an examples, the anchor 106, the first nonlinear suspension member 108, the second nonlinear suspension member 120 and the proof-mass 104 are formed of a monolithic material. In an example, the fixed portion 118 comprises a fixed monolithic material other than the monolithic material of the anchor 106, the first nonlinear suspension member 108, the second nonlinear suspension member 120 and the proof-mass 104. In an example, the fixed portion 118 comprises a fixed monolithic material the same as the monolithic material of the anchor 106, the first nonlinear suspension member 108, the second nonlinear suspension member 120 and the proof-mass 104.
In an example, flexure bearings are disposed on each side of the central anchor, such as on opposite sides of the anchor. In an example, out-of-plane motion caused by each C-shaped flexure bearing on a side is cancelled out by its symmetric counterpart. Accordingly, in an example, the quadrature error induced on each flexure bearing is locally reduced or cancelled.
In an example, a central suspension structure 102 is utilized in a sensor, such as a 6 degree of freedom (“DOF”) sensor 100, such as a monolithic 6-DOF sensor, that is comprised of symmetric flexures bearings. In an example, the symmetric flexure bearings include “C-shaped flexure bearings” 108. In an example, each C-shaped flexure bearing includes inner 110 and outer 112 flexure bearings and a high-stiffness connection flexure bearing 114 between two flexure bearings. In an example, the inner flexure bearing 112 is connected to the anchor 106 on one end, and the outer flexure bearing 112 is connected to the proof-mass 104 on another end. In an example, the suspension system 102 is formed by a total of eight C-shaped flexure bearings 108. In an example, two symmetric C-shaped flexure bearings are located on each of the four sides of a central anchor structure.
In an example, a suspension system provides three gyroscope operational modes: torsional in-plane about the Z-axis for the drive motion; torsional out-of-plane about the X-axis for the Y-axis gyroscope sense motion; and torsional out-of-plane about the Y-axis for the X-axis gyroscope sense motion. In an example, the oscillation modes can be switched between each other.
FIG. 2A illustrates a portion of a suspension, according to an example. FIG. 2B illustrates the suspension of FIG. 2A, in a bending state in which a top portion is bent upward, in an example. FIG. 2C illustrates the suspension of FIG. 2A, in a bending state in which a top portion is bent downward, in an example. The examples shown illustrate the deformation profile in each direction of the suspension mechanism. In an example, bending occurs equal and opposite in both deformation cases illustrates in FIG. 2B and FIG. 2C. In an example, in each direction the two flexure bearings bend in opposite ways. In an example, by creating opposing out-of-plane deformations that cancel each other, the overall out-of-plane deformation from one end of the flexure to the other is minimized.
FIG. 3 illustrates torsional motion of a suspended structure about a Z-axis, according to an example. In an example, a suspension system 300 comprises two symmetric C-shaped flexure bearings 302, 304 on each side of a central anchor structure 306. In an example, one or both of the C-shaped flexure bearings 302, 304 is formed of a high-stiffness connection flexure bearing 308 disposed between two flexure bearings 310, 312. In an example, during in-plane torsional motion, such as motion parallel to the plane of the figure, the out-of-plane motion caused by the deflection of the flexure bearings in each C-shaped flexure bearing on a side is cancelled out by a symmetric counterpart 310′, 312′. Accordingly, quadrature error induced on each flexure bearing is locally reduced or cancelled.
The illustrated example illustrates torsional motion about a Z-Axis, i.e. an axis extending into and out of the page. In an example, during the in-plane torsional motion, the inner 310 and outer 312 flexure bearings in each C-shaped flexure bearing bend in-plane. In an example, the high-stiffness connection bearings 308 do not experience significant bending. For a counterclockwise rotation of the proof-mass about the Z-axis, top part of the proof-mass moves left as shown. In an example, the high-stiffness connection bearings both move left. As a result, the inner and outer flexures on the right C-shaped flexure bearing bend down, while the ones on the left C-shaped flexure bearing bend up. Thus, in an example, the motion results in deflections in opposite directions in the symmetric C-shaped flexure bearing flexures. Since the flexures in symmetric C-shaped flexure bearings deflect in opposite directions, the out-of-plane motion caused by the deflection of the flexure bearings in each C-shaped flexure bearing on a side is cancelled out by its symmetric counterpart. Thus, the quadrature error induced on each flexure bearing is locally cancelled.
FIG. 4 illustrates torsional motion of a suspended structure about an X-axis, according to an example. In an example, a suspension structure can be utilized in a torsional multi-axis micromachined gyroscope system with a proof-mass such as a single proof-mass 404. In an example, a proof-mass 404 is suspended at its center with a single central anchor 406. In an example, one or more flexure bearings 402 connect the anchor 406 to the proof-mass 404. In an example, during the out-of-plane torsional motion about the X-axis, primarily the C-shaped suspension pairs 412, 412′ on the Y-axis sides of the anchor deflect. In an example, the inner flexure bearings 410, 410′ in these C-shaped suspensions bend torsionally about the X-axis, acting as a torsional hinge.
In an example, the die is wafer shaped, with each of a first nonlinear suspension member 408 and a second nonlinear suspension member 412 having a substantially rectangular cross-section with the height of the cross-section smaller than the width.
FIG. 5 illustrates torsional motion of a suspended structure about a Y-axis, according to an example. In an example, a suspension structure can be utilized in a torsional multi-axis micromachined gyroscope system with a proof-mass such as a single proof-mass 404. In an example, a proof-mass 404 is suspended at its center with a single central anchor 406. In an example, one or more flexure bearings 402 connect the anchor 406 to the proof-mass 404. In an example, during the out-of-plane torsional motion about the Y-axis, primarily the C-shaped suspension pairs 412, 412′ on the X-axis sides of the anchor deflect. The inner flexure bearings in these C-shaped flexure bearings 414, 414′ bend torsionally about the Y-axis, acting as a torsional hinge.
FIG. 6 illustrates a 2-Axis Gyroscope including a low quadrature error suspension, according to an example. In an example, a structure 602 can be utilized in various torsional multi-axis micromachined gyroscope systems with a single proof-mass 604 that is suspended at its center with a single central anchor 606. The flexures 608 connect the anchor to the proof-mass 604, and allow the proof-mass to oscillate torsionally about all three axes. The illustrated example senses motion about each of the X-axis and the Y-axis, and proves three gyroscope operational modes: torsional in-plane about the Z-axis for the drive motion; torsional out-of-plane about the X-axis for the Y-axis gyroscope sense motion; and torsional out-of-plane about the Y-axis for the X-axis gyroscope sense motion. In an example, one or more comb electrodes 616 are coupled to a fix portion of the device and sense motion of comb electrodes 618 coupled to the proof-mass 604. In an example, the comb teeth of the comb electrodes 618 are disposed along an axis that bisects an angle between the X-axis and the X-axis.
FIG. 7 illustrates a 3-Axis Gyroscope including a low quadrature error suspension, according to an example. In an example, a structure 702 can be utilized in various torsional multi-axis micromachined gyroscope systems with a single proof-mass 704 that is suspended at its center with a single central anchor 706. The flexures 708 connect the anchor to the proof-mass 704, and allow the proof-mass to oscillate torsionally about all three axes. In an example, a device function as an a three-axis (“X/Y/Z”) gyroscope. In an example, the suspension system 702 provides similar gyroscope operational modes to the device illustrated in FIG. 6. In an example, the illustrated device of FIG. 7 includes additional flexures 720 that provide for the Z-axis sense mode. In an example, one or more comb electrodes 716 are coupled to a fix portion of the device and sense motion of comb electrodes 718 coupled to the proof-mass 704. In an example, the comb teeth of the comb electrodes 718 are disposed along an axis that bisects an angle between the X-axis and the X-axis.
FIG. 8 illustrates quadrature error for an example suspension. In an example, the angle of the flexure bearings has a significant effect on the quadrature. In an example, for each design the angle can be chosen to optimize the quadrature error arising from skew of the resonator flexure bearing flexures. In an example, for the desired implementation of the suspension system, the optimal angle is 15 degrees. In an example, the optimal angle is structure shape dependent, and is selected based on the structure of a respective device. In an example, for a desired structure, two flexure bearings are set at the same angular shift, but two flexure bearings could easily be set at different angles.
FIG. 9 illustrates a drive mode, according to an example. The inventors recognized that skew effect creates quadrature errors in suspension configurations including an anchor 906, and that they could minimize the effect by creating opposite skews on the same flexure 902 or flexure pair 904. Accordingly, there are two flexing flexure bearings separated by a frame, each of which deforms in the opposite direction in the drive mode of operation. The opposite directions of the deformation cause the skew to create out-of-plane deformation in opposite directions, which cancel each other out at the final connection to the moving component. This is used to replace an existing mechanism which only includes one flexure bearing, the skew of which causes deformation in only one direction, creating a lot of out-of-plane motion without any canceling.
However, in some examples, the inner 910, 910′ and outer 912, 912′ flexure bearings are rotated so that deformation causes one flexure bearing to bend up and one flexure bearing to bend downward during drive mode actuation. In an example, the drive mode is a rotational mode about a central anchor. In an example, for each of the four suspension pairs 404, the drive mode causes one to deform in one direction and the other in the other direction.
FIG. 10 illustrates a four bend flexure bearing, according to an example. In an example, the flexure 1002 can include more than one bend. In an example, this can allow for more tightly controlled out-of-plane motion. In an example, a number of switchbacks 1004 are included. In an example, the switchbacks define a zigzag that extends from the anchor 1006 to the proof-mass 1005. In an example, the zigzag includes switchbacks of a regular amplitude along the patter extending from the anchor 1006 to the proof-mass 1005. In additional embodiments, the amplitude varies. In an example, the switchbacks have a C-shape, with top 1008 and bottom 1014 members parallel to one another, but not parallel to a high-stiffness portion 1016.
FIG. 11 illustrates a flexure bearing including a flexing flexure bearing and a non-flexing flexure bearing, according to an example. In an example, a flexure 1102 can also be parameterized by lengthening or shortening the flexing flexure bearings 1110, 1114 or the non-flexing flexure bearing(s) 1112. In the example shown in FIG. 12, the outer flexing flexure bearing 1110 and non-flexing flexure bearing 1112 have been shortened.
FIG. 12 illustrates a flexure bearing including a flexing flexure bearing shorter than the flexure bearing of FIG. 11, and a non-flexing flexure bearing shorter than the non-flexing flexure bearing of FIG. 11, according to an example. The outer flexing flexure bearing 1210 and non-flexing flexure bearing 1212 have been shortened compared to the components of FIG. 11.
FIG. 13A illustrates a suspension with large clearances, according to an example. FIG. 13B illustrates stresses related to flexing of flexures bearings. In the examples, there are voids 1302 disposed between the flexure bearing 1304 and the proof-mass 1306.
FIGS. 14A-D illustrate a die 1400 including various features, according to an example. The features can be used alone, or in combination. One feature is a switchback 1402. The switchback 1402 extends between nonlinear suspension member, e.g., a C-shaped flexure bearing 1406, and the proof-mass 1408. The addition of the switchback 1402 can further reduce quadrature error, at least because it reduces out-of-plane flexing due at least in part to DRIE etching, such as by offsetting bending of one bearing with bending of another bearing across a plane, such as plane 1422. Out-of-plane bending can be offset by bending a second flexure bearing 1407, which can be disposed across plane 1423.
Such offsetting is illustrated in FIG. 15. In FIG. 15, a first bearing 1502 bends away from the proof-mass 1508, while a bearing disposed across a horizontal reference plane 1510 bends toward the proof-mass. A bearing 1506 across the vertical reference plane 1512 and across the horizontal reference plane 1510 also bends away from the proof-mass 1508, in substantially the same way as the 1506, which can offset quadrature error by restoring balance to the flexure bearing suspension.
Returning to FIG. 14A and the description of the switchback 1402, the nonlinear suspension member 1406, e.g., a C-shaped flexure bearing, includes a first or inner portion 1410, a second or center portion 1420, and a third or outer portion 1412. In an example, the outer portion 1412 has a proximal portion coupled to the center portion 1420. In an example, a distal portion of the outer portion 1412 extends away from the anchor bisecting plane 1422. In an example, the outer portion 1412 is coupled with a fourth portion 1402, e.g., part of a switchback, of the first nonlinear suspension member 1406. In an example, the fourth portion 1402 is coupled to the distal portion of the outer portion 1412 at a proximal portion of the fourth portion 1402. In an example, the fourth portion 1402 extends from its proximal portion toward the anchor 1404 to its distal portion. In an example, the distal portion of the fourth portion 1402 is coupled to a fifth portion 1424 of the first nonlinear suspension member 1406. In an example, the fifth portion 1424 extends toward the anchor bisecting plane 1422. In an example, the inner portion 1410 and the outer portion 1412 are linear and parallel. Overall, switchback 1402 examples provide for additional flexing, and offsetting of that flexing, versus suspensions without a switchback 1402.
A second feature is nonsymmetrical stator finger electrodes, as illustrated specifically in FIGS. 14C-D. The electrode structures partially illustrated in FIGS. 14C and 14D are configured for use in a MEMS multi-axis gyroscope with an anti-phase linear Z-axis rotation sense mode. In some examples, the two proof-masses 1454 and 1456 can move in opposite directions. An example of such motion is illustrated in FIG. 16D. Stators 1430, 1431 are anchored by respective side anchors 1428, 1429, in an example. In various examples, electrodes on opposite sides of the central anchor 1404 should be sensitive to concurrent outward or inward motion of the proof-masses to achieve differential pickup of that motion. Thus, stator electrodes that are symmetrical about the Y-Z axis should not be used, as this design would not sense differential motion, as differential motion sensing relies on providing a capacitance differential between two sides of the device, and if the stator electrodes are symmetrical, the capacitance would change similarly on both sides of the Y-Z axis.
The illustrated Z-axis rotation sensing electrode structure senses differential motion. The structure provides for differential detection of anti-phase sense motion, with proof-mass fingers that are symmetric about the Y-Z plane 1422, while stator electrodes that are not symmetric about the Y-Z plane. Symmetrical electrode configurations are desirable for vibration rejection. The disclosed electrodes provide proof-mass electrodes that are symmetrical across the Y-Z plane. The symmetrical proof-mass electrodes achieve improved vibration rejection versus nonsymmetrical designs.
The sectional views in FIGS. 14C-D illustrate interdigitation details on opposing sides of a die, according to an example. Although the electrodes are “pixilated” in appearance, smooth, continuous electrodes are contemplated, as are those demonstrating the features of DRIE. In FIG. 14C, the left stator 1430 has stator fingers 1450 outside (e.g., further away from a central anchor 1404) the proof-mass 1446 fingers 1452, while the right stator 1430′ illustrated in FIG. 14D has stator fingers 1452′ inside the proof-mass 1446′ figures 1452′. Notice that the small capacitive gaps are on the left side of the stator fingers in both electrodes of FIGS. 14C and 14D, and that the proof-mass fingers are fully symmetrical. When proof-mass 1454 of FIG. 14C moves to the left, capacitance of the electrodes in that figure increases. When the proof-mass 1456 of FIG. 14D moves to the right, capacitance of electrode in that illustrate decreases. Thus, differential capacitance is produced, which can be detected.
In an example, Z-axis gyro sense motion is sensed via differential proof-mass sensing, while in-phase motion, i.e. motion of the proof-masses in the same direction, is rejected. In various examples, drive motion (1448 in FIG. 14B) is torsional about the Z-axis (see FIG. 15 and FIG. 16A). Z-axis gyro sense motion is based on proof-masses 1454 and 1456 that oscillate in opposite directions. FIG. 16D illustrates such motion. The Z-axis sense motion is linear in-plane (e.g., the X-Y plane) and anti-phase (e.g., proof-masses 1454 and 1456 oscillate in opposite directions).
A third feature includes vertical flexures 1426, illustrated in FIGS. 14A and 14B. In an example, the vertical flexures 1426 allow the proof-mass frame to deflect more than other portions of the die, such as the inner gimbal 1458, and are useful for adjusting the Y-axis sense resonant frequency. The illustrated gimbal structure provides a flexure 1426 that deflects only for the Y-axis sense mode of the gyroscope, in which the proof-mass 1408 rotates around the X-axis, as illustrated in FIG. 16C. Thus, it allows a designer to adjust the Y-axis sense resonant frequency independent from the drive and X-axis sense frequencies. This enables improvement of the central suspensions to minimize quadrature error in X and Y axes simultaneously.
For example, a fixed portion or substrate can be coupled to an anchor 1404. A fixed portion includes a package substrate, for examples. A first nonlinear suspension member 1406 can be coupled to anchor 1404 on a side of the anchor 1404. A second nonlinear suspension member 1407 coupled to the anchor 1404 on the same side of the anchor 1404. The second nonlinear suspension member can have a shape and location mirroring the first nonlinear suspension member about an anchor 1404 bisecting plane, although the present subject matter is not so limited. One or both of the first nonlinear suspension member and the second nonlinear suspension member can form part of an inner gimbal 1458 of the microelectromechanical die 1400.
A proof-mass 1408 that is planar can be coupled to the inner gimbal 1458. The proof-mass can be suspended by a first suspension 1460 member disposed on a first side of the anchor 1404. The proof-mass can be suspended by a second suspension member 1462 disposed on a second side of the anchor 1404. The first suspension member 1460 can be coupled opposite the first side of the anchor.
The die 1400 can define a first gap 1464. The gap 1464 can extend along a first side 1466 of the anchor 1404. A second gap 1468 can extend along a second side 1470 of the anchor 1404. The second gap 1468 can be opposite the first side 1466. Each of the first gap 1464 and the second gap 1468 can extend between the inner gimbal 1458 and the proof-mass 1408.
The first gap 1464 can extend from the first suspension member 1460 to the second suspension member 1462. The second gap 1468 can extend from the first suspension member 1460 to the second suspension member 1462. One or both of the first gap and the second gap can be C-shaped. The first C-shape can define a first opening 1472 that opens to a second opening 1474 of the second C-shape of the second gap 1468.
The first C-shape can include a first end portion 1482 and a second end portion 1484, with a center portion 1486 extending between the first end portion and the second end portion. The first end portion and the second end portion can be perpendicular to the center portion. A first canted portion 1488 can extend between the first end portion 1482 and the center portion and a second canted portion 1490 can extend between the second end portion 1484 and the center portion. The first gap can be a mirrored shape of the second gap and the first gap can be mirrored along the anchor bisecting plane.
The first gap can define a first vertical flexure 1476 and a second vertical flexure 1478. The second gap can define a third vertical flexure 1426 and a fourth vertical flexure 1480. Each of the first, second, third and fourth vertical flexures can be elongate, with a length longer than a width. Each respective length can extend away from a respective suspension member. Each respective length can extend away from the anchor bisecting plane 1422.
In an example, a solid proof-mass frame structure, such as the structure illustrated in FIG. 7, depends on the central suspension system to set the drive and X/Y sense frequencies. Thus, all three frequencies and quadrature error in two axes may be improved simultaneously.
The gimbal structure illustrated in FIGS. 14A-D provides an extra degree of freedom to adjust the Y-axis sense mode. In an example, central flexures 1426 extend away from an inner gimbal 1458 along the Y-axis. These flexures can flex vertically. FIG. 16C illustrates flex of the flexures to enable the proof-mass to rotate around the X-axis. In an example, one or more flexures 1426 can connect the inner gimbal 1458 to the proof-mass 1408 frame. In an example, these flexures 1426 deflect only for the Y-axis sense mode of the gyroscope. The added out-of-plane flexures allow for adjustment of the Y-axis sense resonant frequency independent from the drive and X-axis sense frequencies.
In various examples, drive motion (1448 in FIG. 14B) is torsional about the Z-axis, such as about the central anchor 1404. FIG. 15 illustrates the suspension of FIG. 14 flexed in torsion around a Z-axis, according to an example and FIG. 16A also illustrates the suspension of FIG. 14 flexed in torsion around a Z-axis, according to an example. FIG. 16B illustrates the suspension of FIG. 14 flexed about a Y-axis, according to an example. In these examples, the flexures 1426 demonstrate limited flex. FIG. 16C, however, illustrates the suspension of FIG. 14 flexed about the X-axis, flexing flexures 1426, according to an example. In an example, the Y-axis sense motion is out-of-plane torsional about the X-axis.
An additional feature of FIGS. 14A-D includes curved finger electrodes. These can be insensitive to rotational drive motion. Various examples can include electrodes that are curved around an axis orthogonal to the plane in which the electrodes are disposed. Curved finger electrodes, e.g. fingers 1450 and 1452, can be less sensitive to the rotational drive motion such as the motion illustrated in FIG. 16A. In an example, while proof-mass electrodes are rotating with respect to stator electrodes, gap distance between the electrodes remains the similar or the same. This can preserve a similar capacitance, in some examples. However, in some examples, the area of one electrode facing the other changes, which can provide a differential capacitance, allowing for sensing or rotation around the Z-axis. Thus, providing curved electrodes to maintain a gap distance between proof-mass electrodes and stator electrodes as the die rotates about an axis orthogonal to a plane in which the electrodes are exposed can optionally provide a no or low capacitance change, or a desired capacitance change that can be sensed to detect the rotation.
A microelectromechanical die 1400 can couple with a substrate such as a package to form a packaged integrated circuit. A proof-mass 1408 can be coupled to the substrate at an anchor 1404. The proof-mass can include a first portion 1454 that can be moveable with respect to the anchor 1404. The first portion can include a first proof-mass electrode 1452. A second portion 1456 of the proof-mass 1408, opposite the first portion 1454 with respect to the anchor 1404, can be moveable with respect to the anchor 1404 and the first portion 1454. The second portion 1456 can include a second proof-mass electrode 1452′. The proof-mass 1408 can define a first opening 1492 on a first side of the anchor 1404, such as on the first side of the plane 1423. The first portion 1454 of the proof-mass can be moveably coupled in the opening 1492 to the substrate.
The first proof-mass electrode 1452 can be one of a first plurality of proof-mass electrodes extending into the opening 1492. The plurality can be spaced apart from one another. The proof-mass 1408 can define a second opening 1494 on the second side of the anchor, such as on the first side of the plane 1423. The second portion 1456 can be coupled inside the second opening 1494. The second proof-mass electrode 1452′ can be one of a second plurality of proof-mass electrodes extending into the opening 1494, spaced apart from one another.
A first stator 1430 can be coupled to the substrate, such as via anchor 1428, and can include a first stator electrode 1450. The first stator electrode 1450 can extend alongside the first proof-mass electrode 1452 of the proof-mass to form a first electrode pair. A second stator 1431 can be coupled to the substrate and can include a second stator electrode 1451, opposite the first stator electrode 1450. The second stator electrode 1451 can extend alongside the second proof-mass electrode 1452′ of the second portion 1456 of the proof-mass 1408 to form a second electrode pair. The first electrode pair can form a first capacitor. The second electrode pair can form a second capacitor.
The first proof-mass electrode of the proof-mass can be opposite the second proof-mass electrode of the proof-mass, across the anchor and wherein the first stator electrode can be coupled to the substrate opposite the second anchored electrode, across the anchor.
The first stator electrode 1450 can be one of a first plurality of stator electrodes interdigitated and paired with respective ones of the first plurality of proof-mass electrodes to form the first electrode pair. The second stator can be one of a second plurality of stator electrodes interdigitated and paired with respective ones of the second plurality of stator electrodes to form the second electrode pair
In a first vibratory mode of the die 1400 the first portion 1454 of the proof-mass can be to move away from the second portion 1456 of the proof-mass. The first stator electrode 1450 and second stator electrode 1451 can be arranged such that a distance between electrodes of the first electrode pair can be inversely proportional to a distance between electrodes of the second electrode pair. The first portion 1454 of the proof-mass can be symmetrical, across the anchor 1404, with the second portion 1456 of the proof-mass. The first stator 1430 can be asymmetrical, across the anchor 1404, with respect to the second stator 1431.
FIG. 18 shows a method of making vibration rejection z-axis electrodes, according to an embodiment. At 1802, an example includes forming a proof-mass. The example can include forming an anchor for coupling the proof-mass to a substrate. The example can include forming a first portion on a first side of the anchor, the first portion moveable with respect to the anchor and including a first proof-mass electrode. The example can include forming a second portion on a second side of the anchor, opposite the first side, the second portion including a second proof-mass electrode. At 1804, the example can include forming a first stator for coupling to the substrate, including forming a first stator electrode for extending alongside the first proof-mass electrode of the proof-mass to form a first electrode pair. At 1806, the example can include forming a second stator for coupling to the substrate, including forming a second stator electrode for extending alongside the second proof-mass electrode of the proof-mass to form a second electrode pair. According to the example at 1808, the proof-mass, the first stator and the second stator are formed such that in a first vibratory mode of the proof-mass a distance between electrodes of the first pair is inversely proportional to a distance between electrodes of the second electrode pair.
In the first vibratory mode the first plurality of stator electrodes can be configured to move away from the first plurality of stator electrodes and away from the anchor while the second plurality of stator electrodes can be configured to move toward the second plurality of stator electrodes and toward the anchor. The proof-mass can be configured to vibrate with respect to the substrate to vary the distances between the first plurality of stator electrodes and the first plurality of stator electrodes and to vary the distances between the second plurality of stator electrodes and the second plurality of stator electrodes.
One of the first plurality of stator electrodes, closest to the anchor, e.g., 1452, being a distance from one of the first plurality of stator electrodes, e.g. 1450, closest to the anchor, when one of the second plurality of stator electrodes, e.g. 1451, closest to the anchor, can be a greater distance from one of the second plurality of stator electrodes, e.g. 1452′, closest to the anchor.
Each of the first proof-mass electrode 1452 and the first stator electrode 1450 can be elongate. A distance D14 between the first proof-mass electrode and the first stator electrode can be substantially constant along the length L14 of each. Each of the second proof-mass electrode 1452′ and the second stator electrode 1451 can be elongate. A distance between the second proof-mass electrode and the second stator electrode being substantially constant along the length of each.
One or more of the first proof-mass electrode, the second proof-mass electrode, the first stator electrode and the second stator electrode can be curved. Each of the electrodes can be curved around an axis around which the proof-mass can be configured to rotate in a second vibratory mode. The axis can be the intersection between the plane 1422 and the plane 1423. The proof-mass can be formed into shape through material removal from a wafer, such as by excising material, such as through etching. Forming can include deep reactive-ion etching.
The die 1400 can be used to sense motion. Vibration of the first portion of a proof-mass and the second portion of a proof-mass can be excited so that the first portion and the second portion move together and apart in synchrony, toward a respective first stator and second stator. Motion of the die along a direction extending between the first portion of the proof-mass and the second portion of the proof-mass can be sensed by measuring a differential in respective capacitance values for the first stator and the second stator. The first proof-mass electrode 1452 can move toward a first stator electrode 1450 of a first stator 1430 while the second portion 1456 can include a second proof-mass electrode 1452′ that moves away from a second stator electrode 1451 of a second stator. Sensing motion can include sensing a differential between a first capacitance of a first electrode pair including the first proof-mass electrode and the first stator electrode and a second electrode pair including the second proof-mass electrode and the second stator electrode. The proof-mass can be rotated in the plane of the proof-mass, e.g. a plane parallel planes 1422 and 1423, without changing the measured differential in respective capacitance values for the first stator and the second stator. Rotation can occur without changing a distance between electrodes of the first electrode pair and without changing a distance between electrodes of the second electrode pair.
FIG. 17 shows a method of making a low-quadrature-error suspension, according to an embodiment. At 1702 the method includes etching a material to define an anchor. At 1704, the method includes etching the material to define a first nonlinear suspension member coupled to anchor on a side of the anchor. At 1706, the method includes etching the material to define a second nonlinear suspension member coupled to the anchor on the same side of the anchor, the second nonlinear suspension member having a shape and location mirroring the first nonlinear suspension member about an anchor bisecting plane. At 1708 the method includes etching the material to define a proof-mass that is planar, the proof-mass suspended at least in part by the first nonlinear suspension member and the second nonlinear suspension member such that the proof-mass is rotable about the anchor and is slideable in a plane parallel to the substrate.
Optional methods are possible, including methods in which etching includes deep reactive-ion etching. In some optional methods, the first nonlinear suspension member and the second nonlinear suspension member are part of a first set, comprising etching the material to define a second set of nonlinear suspension members opposite the first set. Some optional methods include etching a third set of nonlinear suspension members for coupling the anchor to the proof-mass and etching a fourth set of nonlinear suspension members for coupling the anchor to the proof-mass, wherein the third set and the fourth set have a similar for factor to the first set and the second set and are bisected by a second anchor bisecting plane perpendicular the first.
Additional Notes
The subject matter of the present document can be described using several examples. Example 1 can include a microelectromechanical die for sensing motion, that includes a fixed portion, an anchor coupled to the fixed portion, a first nonlinear suspension member coupled to anchor on a side of the anchor, a second nonlinear suspension member coupled to the anchor on the same side of the anchor, the second nonlinear suspension member having a shape and location mirroring the first nonlinear suspension member about an anchor bisecting plane and a proof-mass that is planar, the proof-mass suspended at least in part by the first nonlinear suspension member and the second nonlinear suspension member such that the proof-mass is rotable about the anchor and is slideable in a plane parallel to the fixed portion.
Example 2 includes the subject matter of example 1, wherein the first nonlinear suspension member has a C-shape.
Example 3 includes the subject matter of example 2, wherein the C-shape includes a inner portion coupled to the anchor and extending toward the anchor bisecting plane, a center portion having a proximal portion and a distal portion, with a proximal portion coupled to the inner portion and a distal portion extending away from the anchor along the anchor bisecting plane and coupled to a outer portion extending away from the anchor bisecting plane.
Example 4 includes the subject matter of example 3, wherein the outer portion of the first nonlinear suspension member has a proximal portion coupled to the center portion of the first nonlinear suspension member, and a distal portion extending away from the anchor bisecting plane, with a fourth portion of the first nonlinear suspension member coupled to the distal portion of the outer portion at a proximal portion of the fourth portion, and extending toward the anchor to a distal portion of the fourth portion that is coupled to a fifth portion of the first nonlinear suspension member that extends toward the anchor bisecting plane.
Example 5 includes the subject matter of any of examples 3-4, wherein the inner portion and the outer portion are linear and parallel.
Example 6 includes the subject matter of example 5, wherein the center portion is perpendicular the inner portion and the outer portion.
Example 7 includes the subject matter of any of examples 3-6, wherein the center portion is parallel the anchor bisecting plane.
Example 8 includes the subject matter of any of examples 1-7, wherein the anchor, the first nonlinear suspension member, the second nonlinear suspension member and the proof-mass are formed of a monolithic material.
Example 9 includes the subject matter of example 8, wherein the fixed portion comprises a fixed monolithic material other than the monolithic material of the anchor, the first nonlinear suspension member, the second nonlinear suspension member and the proof-mass.
Example 10 includes the subject matter of any of examples 1-9, wherein the fixed portion comprises a fixed monolithic material the same as the monolithic material of the anchor, the first nonlinear suspension member, the second nonlinear suspension member and the proof-mass.
Example 11 includes the subject matter of any of examples 1-10, wherein the die is wafer shaped, with each of the first nonlinear suspension member and the second nonlinear suspension member have a substantially rectangular cross-section with the height of the cross-section smaller than the width.
Example 12 includes a that includes etching a material to define an anchor, etching the material to define a first nonlinear suspension member coupled to anchor on a side of the anchor, etching the material to define a second nonlinear suspension member coupled to the anchor on the same side of the anchor, the second nonlinear suspension member having a shape and location mirroring the first nonlinear suspension member about an anchor bisecting plane and etching the material to define a proof-mass that is planar, the proof-mass suspended at least in part by the first nonlinear suspension member and the second nonlinear suspension member such that the proof-mass is rotable about the anchor and is slideable in a plane parallel to the substrate.
Example 13 includes the subject matter of example 12, wherein etching includes deep reactive-ion etching.
Example 14 includes the subject matter of any of examples 12-13, wherein the first nonlinear suspension member and the second nonlinear suspension member are part of a first set, comprising etching the material to define a second set of nonlinear suspension members opposite the first set.
Example 15 includes the subject matter of example 14, comprising etching a third set of nonlinear suspension members for coupling the anchor to the proof-mass and etching a fourth set of nonlinear suspension members for coupling the anchor to the proof-mass, wherein the third set and the fourth set have a similar for factor to the first set and the second set and are bisected by a second anchor bisecting plane perpendicular the first.
Example 16 can include any of the preceding examples, wherein a microelectromechanical die senses motion. The example can include a substrate. The example can include a proof-mass coupled to the substrate at an anchor. The proof-mass can include a first portion moveable with respect to the anchor, the first portion including a first proof-mass electrode. The example can include a second portion of the proof-mass, opposite the first portion with respect to the anchor, the second portion moveable with respect to the anchor and the first portion, the second portion including a second proof-mass electrode. The example can include a first stator coupled to the substrate and including a first stator electrode extending alongside the first proof-mass electrode of the first portion of the proof-mass to form a first electrode pair. The example can include a second stator coupled to the substrate and including a second stator electrode, opposite the first stator electrode, and extending alongside the second proof-mass electrode of the second portion of the proof-mass to form a second electrode pair. According to the examples, in a first vibratory mode, in which the first portion of the proof-mass is to move away from the second portion of the proof-mass, the proof-mass, first stator electrode and second stator electrode are arranged such that a distance between electrodes of the first electrode pair is inversely proportional to a distance between electrodes of the second electrode pair.
Example 17 can include any of the preceding examples wherein the first proof-mass electrode of the proof-mass is opposite the second proof-mass electrode of the proof-mass, across the anchor and wherein the first stator electrode is coupled to the substrate opposite the second anchored electrode, across the anchor.
Example 18 can include any of the preceding examples wherein the first portion of the proof-mass is symmetrical, across the anchor, with the second portion of the proof-mass, and the first stator is asymmetrical, across the anchor, with respect to the second stator.
Example 19 can include any of the preceding examples wherein the first electrode pair comprises a first capacitor, and the second electrode pair comprises a second capacitor.
Example 20 can include any of the preceding examples wherein each of the first proof-mass electrode and the first stator electrode are elongate, with a distance between the first proof-mass electrode and the first stator electrode being substantially constant along the length of each
Example 21 can include any of the preceding examples wherein each of the second proof-mass electrode and the second stator electrode are elongate, with a distance between the second proof-mass electrode and the second stator electrode being substantially constant along the length of each.
Example 22 can include any of the preceding examples wherein the proof-mass defines a first opening on a first side of the anchor, with the first portion of the proof-mass moveably coupled therein, with a first plurality of proof-mass electrodes, including the first proof-mass electrode, extending into the opening, spaced apart from one another. In the example the proof-mass can define a second opening on the second side of the anchor, with the second portion coupled therein, with a second plurality of proof-mass electrodes, including the second proof-mass electrode, extending into the opening, spaced apart from one another.
Example 23 can include any of the preceding examples wherein the first stator electrode is one of a first plurality of stator electrodes interdigitated and paired with respective ones of the first plurality of proof-mass electrodes to form the first electrode pair; and wherein the second stator electrode is one of a second plurality of stator electrodes interdigitated and paired with respective ones of the second plurality of stator electrodes to form the second electrode pair.
Example 24 can include any of the preceding examples wherein, in the first vibratory mode, the first plurality of stator electrodes is configured to move away from the first plurality of stator electrodes and away from the anchor while the second plurality of stator electrodes is configured to move toward the second plurality of stator electrodes and toward the anchor.
Example 25 can include any of the preceding examples wherein the proof-mass is configured to vibrate with respect to the substrate to vary the distances between the first plurality of stator electrodes and the first plurality of stator electrodes and to vary the distances between the second plurality of stator electrodes and the second plurality of stator electrodes, with one of the first plurality of stator electrodes, closest to the anchor, being a distance from one of the first plurality of stator electrodes, closest to the anchor, when one of the second plurality of stator electrodes, closest to the anchor, is a greater distance from one of the second plurality of stator electrodes, closest to the anchor.
Example 26 can include any of the preceding examples wherein the first proof-mass electrode, the second proof-mass electrode, the first stator electrode and the second stator electrode are curved, wherein each of the electrodes curves around an axis around which the proof-mass is configured to rotate in a second vibratory mode.
Example 27 can include any of the preceding examples and can include forming a proof-mass, including forming an anchor for coupling the proof-mass to a substrate. The example can include forming a first portion on a first side of the anchor, the first portion moveable with respect to the anchor and including a first proof-mass electrode. The example can include forming a second portion on a second side of the anchor, opposite the first side, the second portion including a second proof-mass electrode. The example can include forming a first stator for coupling to the substrate, including forming a first stator electrode for extending alongside the first proof-mass electrode of the proof-mass to form a first electrode pair. The example can include forming a second stator for coupling to the substrate, including forming a second stator electrode for extending alongside the second proof-mass electrode of the proof-mass to form a second electrode pair. According to the example, the proof-mass, the first stator and the second stator are formed such that in a first vibratory mode of the proof-mass a distance between electrodes of the first pair is inversely proportional to a distance between electrodes of the second electrode pair.
Example 28 can include any of the preceding examples wherein forming includes deep reactive-ion etching.
Example 29 can include any of the preceding examples wherein forming the first proof-mass electrode, forming the second proof-mass electrode, forming the first stator electrode and forming the second stator electrode includes forming each with a curvature, with each curving around an axis around which the proof-mass rotates in a second vibratory mode.
Example 30 can include any of the preceding examples comprising forming a first capacitor with the first electrode pair and forming a second capacitor with the second electrode pair.
Example 31 can include any of the preceding examples wherein forming the first proof-mass electrode and the first stator electrode includes forming a first distance between them that is substantially constant along a length of the first electrode pair, and forming the second proof-mass electrode and the second stator electrode includes forming a second distance between them that is substantially constant along a length of the second electrode pair.
Example 32 can include any of the preceding examples, including a method for sensing motion with a microelectromechanical die, comprising. The example can include exciting vibration of a first portion of a proof-mass and a second portion of a proof-mass so the first portion and the second portion move together and apart in synchrony, toward a respective first stator and second stator. The example can include sensing motion of the die along a direction extending between the first portion of the proof-mass and the second portion of the proof-mass by measuring a differential in respective capacitance values for the first stator and the second stator.
Example 33 can include any of the preceding examples wherein the first portion includes a first proof-mass electrode that moves toward a first stator electrode of a first stator while the second portion includes a second proof-mass electrode that moves away from a second stator electrode of a second stator.
Example 34 can include any of the preceding examples wherein sensing motion includes sensing a differential between a first capacitance of a first electrode pair including the first proof-mass electrode and the first stator electrode, and a second electrode pair including the second proof-mass electrode and the second stator electrode.
Example 35 can include any of the preceding examples, including rotating the proof-mass, in the plane of the proof-mass, without changing the measured differential in respective capacitance values for the first stator and the second stator.
Example 36 can include any of the preceding examples, including rotating the proof-mass, in the plane of the proof-mass, without changing a distance between electrodes of the first electrode pair and without changing a distance between electrodes of the second electrode pair.
Example 37 can include any of the preceding claims including a microelectromechanical die for sensing motion. The example can include a fixed portion. The example can include an anchor coupled to the fixed portion. The example can include a first nonlinear suspension member coupled to anchor on a first side of the anchor. The example can include a second nonlinear suspension member coupled to the anchor on the first side of the anchor, the second nonlinear suspension member having a shape and location mirroring the first nonlinear suspension member about an anchor bisecting plane. According to the example, the first nonlinear suspension member and the second nonlinear suspension member are part of an inner gimbal of the microelectromechanical die. The example can include a proof-mass that is planar, the proof-mass suspended by a first suspension member disposed on a first side of the anchor and a second suspension member disposed on a second side of the anchor opposite the first side, with the die defining a first gap extending along a first side of the anchor and a second gap extending along a second side of the anchor, opposite the first side, with each of the first gap and the second gap extending between the inner gimbal and the proof-mass, wherein the inner gimbal is supported at least in part by the first nonlinear suspension member and the second nonlinear suspension member such that the proof-mass is rotable about the anchor and is slideable in a plane parallel to the fixed portion.
Example 38 can include any of the preceding claims, wherein the first gap extends from the first suspension member to the second suspension member, and the second gap extends from the first suspension member to the second suspension member.
Example 39 can include any of the preceding claims, wherein the first gap and the second gap are C-shaped, with a first C-shape defining a first opening that opens to a second opening of a second C-shape.
Example 40 can include any of the preceding claims, wherein the first gap defines a first vertical flexure and a second vertical flexure, and the second gap defines a third vertical flexure and a fourth vertical flexure.
Example 41 can include any of the preceding claims, wherein each of the first, second, third and fourth vertical flexures are elongate, with a length longer than a width, with each respective length extending away from a respective suspension member.
Example 42 can include any of the preceding claims, wherein each respective length extends away from the anchor bisecting plane.
Example 43 can include any of the preceding claims, wherein the first C-shape includes a first end portion and a second end portion, with a center portion extending between the first end portion and the second end portion.
Example 44 can include any of the preceding claims, wherein the first end portion and the second end portion are perpendicular to the center portion.
Example 45 can include any of the preceding claims, wherein a first canted portion extends between the first end portion and the center portion and a second canted portion extends between the second end portion and the center portion.
Example 46 can include any of the preceding claims, wherein the first gap is a mirrored shape of the second gap and the first gap is mirrored along the anchor bisecting plane.
Example 47 can include a method including forming a material to define an inner gimbal for coupling with an anchor for anchoring to a substrate. The example can include forming the material to define a first nonlinear suspension member coupled to anchor on a first side of the anchor. The example can include forming the material to define a second nonlinear suspension member coupled to the anchor on the first side of the anchor, the second nonlinear suspension member having a shape and location mirroring the first nonlinear suspension member about an anchor bisecting plane. The example can include forming the material to define a proof-mass that is planar, the proof-mass suspended by a first suspension member disposed on a first side of the anchor and a second suspension member disposed on a second side of the anchor opposite the first side, with a first gap extending along a first side of the anchor and a second gap extending along a second side of the anchor, opposite the first side, with each of the first gap and the second gap extending between the proof-mass and the inner gimbal.
Example 48 can include any of the preceding claims, wherein forming includes deep reactive-ion etching.
Example 49 can include any of the preceding claims, wherein the first nonlinear suspension member and the second nonlinear suspension member are part of a first set, comprising etching the material to define a second set of nonlinear suspension members opposite the first set.
Example 50 can include etching a third set of nonlinear suspension members for coupling the anchor to the proof-mass and etching a fourth set of nonlinear suspension members for coupling the anchor to the proof-mass
Example can include any of the preceding claims, wherein the third set and the fourth set have a similar for factor to the first set and the second set and are bisected by a second anchor bisecting plane perpendicular the first.
Example 51 can include any of the preceding claims, wherein etching the first gap and the second gap includes forming each into a C-shape, with a first C-shape of the first gap opens to a second C-shape of the second gap.
Example 52 can include a method for sensing motion with a microelectromechanical die, comprising. The example can include rotating a proof-mass with respect to an inner gimbal that is coupled to a substrate via an anchor, by. The example can include deforming a first nonlinear suspension member, that couples the proof-mass to a first side of the anchor, out-of-plane of the plane of the proof-mass, above the proof-mass. The example can include deforming a second nonlinear suspension member, that couples the proof-mass to the first side of the anchor, out-of-plane of the plane of the proof-mass on an opposite first side of the plane of the proof-mass, below the proof-mass. The example can include deforming a first suspension member, that supports the proof-mass and that is disposed on a first side of the anchor, and a second suspension member, that is disposed on a second side of the anchor opposite the first side, with the die defining a first gap extending along a first side of the anchor and a second gap extending along a second side of the anchor, opposite the first side, with each of the first gap and the second gap extending between the inner gimbal and the proof-mass.
Example 53 can include any of the preceding claims, wherein deforming a first suspension member, that supports the proof-mass and that is disposed on a first side of the anchor, and a second suspension member, that is disposed on a second side of the anchor opposite the first side includes deforming a first vertical flexure and a second vertical flexure, each defined by the first gap, and a third vertical flexure and a fourth vertical flexure, each defined by the second gap.
Example 54 can include any of the preceding claims, wherein during a first half of a rotation cycle, the first and second vertical flexures are deformed away from the anchor, and the third and fourth vertical flexure are deformed toward the anchor, and during a second half of a rotation cycle, the first and second vertical flexures are deformed toward from the anchor, and the third and fourth vertical flexure are deformed away the anchor.
Example 55 can include any of the preceding claims, wherein deforming of the flexures includes bending.
Example 56 can include any of the preceding claims, wherein an anchor bisecting plane bisects the anchor vertically and passes between the first and second nonlinear suspension members, between the first and second suspension members.
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. The above description is intended to be illustrative, and not restrictive. In other examples, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description.
The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

## Claims

1. A microelectromechanical die for sensing motion, comprising:
a substrate;
a proof-mass coupled to the substrate at an anchor, the proof-mass including:
a first portion moveable with respect to the anchor, the first portion including a first proof-mass electrode; and
a second portion, opposite the first portion with respect to the anchor, the second portion moveable with respect to the anchor and the first portion, the second portion including a second proof-mass electrode;

a first stator coupled to the substrate and including a first stator electrode extending alongside the first proof-mass electrode of the first portion of the proof-mass to form a first electrode pair; and
a second stator coupled to the substrate and including a second stator electrode, opposite the first stator electrode, and extending alongside the second proof-mass electrode of the second portion of the proof-mass to form a second electrode pair;
wherein in a first vibratory mode, in which the first portion of the proof-mass is to move away from the second portion of the proof-mass, the proof-mass, the first stator electrode, and the second stator electrode are arranged such that a distance between electrodes of the first electrode pair is inversely proportional to a distance between electrodes of the second electrode pair.

2. The die of claim 1, wherein the first proof-mass electrode of the proof-mass is opposite the second proof-mass electrode of the proof-mass, across the anchor and wherein the first stator electrode is coupled to the substrate opposite the second stator electrode, across the anchor.

3. The die of claim 1, wherein the first portion of the proof-mass is symetrical, across the anchor, with the second portion of the proof-mass, and the first stator is asymmetrical, across the anchor, with respect to the second stator.

4. The die of claim 1, wherein the first electrode pair comprises a first capacitor, and the second electrode pair comprises a second capacitor.

5. The die of claim 1, wherein each of the first proof-mass electrode and the first stator electrode are elongate, with a distance between the first proof-mass electrode and the first stator electrode being substantially constant along the length of each., wherein each of the second proof-mass electrode and the second stator electrode are elongate, with a distance between the second proof-mass electrode and the second stator electrode being substantially constant along the length of each.

6. The die of claim 1, wherein the proof-mass defines
a first opening on a first side of the anchor, with the first portion of the proof-mass moveably coupled therein, with a first plurality of proof-mass electrodes, including the first proof-mass electrode, extending into the opening, spaced apart from one another; and
a second opening on a second side of the anchor, with the second portion coupled therein, with a second plurality of proof-mass electrodes, including the second proof-mass electrode, extending into the opening, spaced apart from one another.

7. The die of claim 6, wherein the first stator electrode is one of a first plurality of stator electrodes interdigitated and paired with respective ones of the first plurality of proof-mass electrodes to form the first electrode pair; and wherein the second stator electrode is one of a second plurality of stator electrodes interdigitated and paired with respective ones of the second plurality of stator electrodes to form the second electrode pair.

8. The die of claim 7, wherein, in the first vibratory mode, the first plurality of stator electrodes is configured to move away from the first plurality of stator electrodes and away from the anchor while the second plurality of stator electrodes is configured to move toward the the second plurality of stator electrodes and toward the anchor.

9. The die of claim 8, wherein the proof-mass is configured to vibrate with respect to the substrate to vary the distances between the first plurality of stator electrodes and the first plurality of stator electrodes and to vary the distances between the second plurality of stator electrodes and the second plurality of stator electrodes, with one of the first plurality of stator electrodes, closest to the anchor, being a distance from one of the first plurality of stator electrodes, closest to the anchor, when one of the second plurality of stator electrodes, closest to the anchor, is a greater distance from one of the second plurality of stator electrodes, closest to the anchor.

10. The die of claim 1, wherein the first proof-mass electrode, the second proof-mass electrode, the first stator electrode and the second stator electrode are curved, wherein each of the electrodes curves around an axis around which the proof-mass is configured to rotate in a second vibratory mode.

11. A method for sensing motion with a microelectromechanical die, comprising:
exciting vibration of a first portion of a proof-mass and a second portion of the proof-mass so the first portion and the second portion move together and apart in synchrony, toward a respective first stator and second stator; and
sensing motion of the die along a direction extending between the first portion of the proof-mass and the second portion of the proof-mass by measuring a differential in respective capacitance values for the first stator and the second stator.

12. The method of claim 11, wherein the first portion includes a first proof-mass electrode that moves toward a first stator electrode of a first stator while the second portion includes a second proof-mass electrode that moves away from a second stator electrode of a second stator.

13. The method of claim 12, wherein sensing motion includes sensing a differential between a first capacitance of a first electrode pair including the first proof-mass electrode and the first stator electrode, and a second electrode pair including the second proof-mass electrode and the second stator electrode.

14. The method of claim 11, including rotating the proof-mass, in the plane of the proof-mass, without changing the measured differential in respective capacitance values for the first stator and the second stator.

15. The method of claim 14, including rotating the proof-mass, in the plane of the proof-mass, without changing a distance between electrodes of a first electrode pair including the first proof-mass electrode and the first stator electrode, and without changing a distance between electrodes of a second electrode pair including the second proof-mass electrode and the second stator electrode.