Drive and sense stress relief apparatus

A MEMS device is provided comprising a mass configured to move along a first axis and a second axis substantially perpendicular to the first axis; a drive structure coupled to the mass and configured to cause the mass to move along the first axis; a sense structure coupled to the mass and configured to detect motion of the mass along the second axis; a stress relief structure coupled to one of the drive structure or the sense structure; and at least one anchor coupled to an underlying substrate of the MEMS device, wherein the stress relief structure is coupled to the at least one anchor and the at least one anchor is disposed outside of the stress relief structure.

FIELD

The present application relates to stress relief structures for microelectromechanical systems (MEMS) inertial sensors.

BACKGROUND

MEMS devices may comprise multiple moving masses coupled together by one or more couplers. For example, gyroscopes (sometimes referred to simply as “gyros”) are devices which are sensitive to rotation, and therefore which can be used to detect rotation. MEMS gyroscopes typically include a movable body, sometimes referred to as a “proof mass,” to which an electrical signal is applied to produce motion predominantly along a particular axis. This is referred to as driving the proof mass, and the axis along which the proof mass is driven is sometimes referred to as the drive axis. When the gyroscope experiences rotation, the proof mass additionally moves along an axis different than the drive axis, sometimes referred to as the sense axis. The motion of the proof mass along the sense axis is detected, providing an indication of the rotation experienced by the gyroscope. For some MEMS gyroscopes, driving the proof mass may comprise causing motion of the proof mass in-plane. For some MEMS gyroscopes, rotation may be detected by sensing out-of-plane motion of the proof mass.

BRIEF SUMMARY

Some aspects are directed to a MEMS device comprising: a mass configured to move along a first axis and a second axis substantially perpendicular to the first axis; a drive structure coupled to the mass and configured to cause the mass to move along the first axis; a sense structure coupled to the mass and configured to detect motion of the mass along the second axis; and a stress relief structure comprising a frame coupled to one of the drive structure or the sense structure, wherein the frame comprises: a plurality of L-shaped beams including a first L-shaped beam coupled to the one of the drive structure or the sense structure at at least one first point and a second L-shaped beam coupled to the one of the drive structure or the sense structure at at least one second point; and a plurality of U-shaped beams including a first U-shaped beam coupled to a vertex of the first L-shaped beam and a second U-shaped beam coupled to a vertex of the second L-shaped beam.

Some aspects are directed to a MEMS device comprising: a mass configured to along a first axis and a second axis substantially perpendicular to the first axis; a drive structure coupled to the mass and configured to cause the mass to move along the first axis; a sense structure coupled to the mass and configured to detect motion of the mass along the second axis; a stress relief structure coupled to one of the drive structure or the sense structure; and at least one anchor coupled to an underlying substrate of the MEMS device, wherein the stress relief structure is coupled to the at least one anchor and the at least one anchor is disposed outside of the stress relief structure.

Some aspects are directed to a stress relief structure for coupling to one of a drive structure or a sense structure of a MEMS device, the stress relief structure comprising: a frame comprising: a plurality of L-shaped beams including a first L-shaped beam and a second L-shaped beam; and a plurality of U-shaped beams including a first U-shaped beam coupled to a vertex of the first L-shaped beam and a second U-shaped beam coupled to a vertex of the second L-shaped beam, wherein the frame exhibits rotational symmetry within an x-y plane.

DETAILED DESCRIPTION

MEMS devices, such as MEMS gyroscopes, are subject to stress which may lead to non-linearity and quadrature. Quadrature is motion of the proof mass in the direction orthogonal to the drive motion, which is ideally 90° out of phase with the Coriolis response. Typically, quadrature is undesirable, as the gyroscope may be unable to distinguish between electrical signals resulting from quadrature as opposed to those resulting from rotation, and thus the accuracy of the gyroscope at detecting rotation may be negatively impacted by the occurrence of quadrature.

Aspects of the present application relate to stress relief structures and related aspects which function to improve stress relief of a MEMS device, thereby improving the linearity of the MEMS device and reducing quadrature. According to some aspects, the stress relief structures described herein reduce shear, normal, and/or dynamic resonator stresses in a MEMS device. According to some aspects, the improved stress relief structures improve the overall symmetry of the MEMS device.

In some embodiments, a MEMS device is provided having anchors which improve stress relief of the MEMS device. For example, the MEMS device may be configured such that anchors are connected to other components of the MEMS device by multiple connections (e.g., two connections, four connections) disposed symmetrically about the anchor. In some embodiments, the MEMS device is configured having multiple pivot points (e.g., at least two pivot points, at least three pivot points) about an anchor.

Thus, according to an aspect of the present application, there is provided a MEMS device comprising a mass configured to move along a first axis and a second axis substantially perpendicular to the first axis, a drive structure coupled to the mass and configured to cause the mass to move along the first axis, a sense structure coupled to the mass and configured to detect motion of the mass along the second axis, and a stress relief structure comprising a frame coupled to one of the drive structure or the sense structure, wherein the frame comprises: a plurality of L-shaped beams including a first L-shaped beam coupled to the one of the drive structure or the sense structure at at least one first point and a second L-shaped beam coupled to the one of the drive structure or the sense structure at at least one second point, and a plurality of U-shaped beams including a first U-shaped beam coupled to a vertex of the first L-shaped beam and a second U-shaped beam coupled to a vertex of the second L-shaped beam.

Some embodiments provide for a MEMS device comprising a mass configured to move along a first axis and a second axis substantially perpendicular to the first axis, a drive structure coupled to the mass and configured to cause the mass to move along the first axis, a sense structure coupled to the mass and configured to detect motion of the mass along the second axis, a stress relief structure coupled to one of the drive structure or the sense structure, and at least one anchor coupled to an underlying substrate of the MEMS device, wherein the stress relief structure is coupled to the at least one anchor and the at least one anchor is disposed outside of the stress relief structure.

In some embodiments, there is provided a stress relief structure for coupling to one of a drive structure or a sense structure of a MEMS device, the stress relief structure comprising a frame comprising a plurality of L-shaped beams including a first L-shaped beam and a second L-shaped beam, and a plurality of U-shaped beams including a first U-shaped beam coupled to a vertex of the first L-shaped beam and a second U-shaped beam coupled to a vertex of the second L-shaped beam, wherein the frame exhibits rotational symmetry within an x-y plane.

In some embodiments, aspects of the present disclosure may be implemented in a MEMS inertial sensor, such as a MEMS gyroscope. Example MEMS gyroscopes in which aspects of the present disclosure may be implemented in are provided and further described herein, for example, inFIGS.11A-11B.

The aspects and embodiments described above, as well as additional aspects and embodiments, are described further below. These aspects and/or embodiments may be used individually, all together, or in any combination, as the technology is not limited in this respect.

FIG.1Aillustrates an example MEMS device100having stress relief structures which reduce one or more types of stress (e.g., normal, shear, dynamic) experienced by the MEMS device thereby reducing non-linearity and quadrature of the MEMS device, according to some non-limiting embodiments.FIG.1Aillustrates aspects of the present disclosure which may facilitate improved stress relief for the MEMS device100. It should be appreciated that aspects ofFIG.1Aand some subsequent figures shown herein have been simplified for the purposes of illustration. Additional details of components of the MEMS device100are shown in subsequent figures. Further, the MEMS devices described herein may have one or more additional features not shown in the illustrated embodiments. The example MEMS device100may comprise a portion of a larger MEMS device, for example, as shown inFIGS.11A-11B.

The MEMS device100comprises a proof mass102. The proof mass102may be suspended above and coupled to an underlying substrate (not shown). The MEMS device100may be configured to detect angular rates through detection of Coriolis forces. For example, the proof mass102may be configured to move along a first axis (e.g., the x-axis) and a second axis substantially perpendicular to the first axis (e.g., the y-axis). In some embodiments, the proof mass102may be configured to move in-plane and/or out-of-plane.

The Coriolis effect, and hence a Coriolis force, arises when 1) a proof mass oscillates; and 2) the MEMS device (e.g., MEMS gyroscope) is subjected to angular motion. In the example shown inFIGS.1A-1C, the proof mass102may be driven to oscillate along the x-axis, and a Coriolis force arises when the proof mass102undergoes angular motion in the plane of the page (e.g., the x-y plane, about an axis through the page). The Coriolis force may cause the proof mass102to be displaced along the y-axis. The MEMS device100may be configured to sense the displacement of the proof mass102to measure rotation. In some embodiments, for example as shown inFIGS.11A-11B, one or more additional proof masses may be provided to sense rotation about a same or different axis as proof mass102.

MEMS device100further comprises drive structures104and sense structures106. A drive structure is a structure configured to cause motion of a proof mass of the MEMS device100. Drive structures104may include drive capacitors, in which electrostatic forces are used to cause motion of the proof mass102. For example, a drive structure104may comprise a first plurality of electrodes being spaced a distance from a second plurality of electrodes which are coupled to the underlying substrate. A voltage may be applied to the second plurality of electrodes causing the distance between the first and second plurality of electrodes to change. The drive structures may therefore oscillate in response to the voltage applied to the second plurality of electrodes by virtue of the change in distance between the first and second plurality of electrodes. Motion of the drive structures104may be transferred to the proof mass102as further described herein.

A sense structure is a structure configured to detect motion of a proof mass of the MEMS device100. For example, sense structures106may sense motion of the proof mass102caused by Coriolis forces arising when the proof mass102undergoes angular motion. Motion of the proof mass102caused by Coriolis forces may be transferred to the sense structures106causing the sense structures to oscillate as further described herein. Sense structures106may include sense capacitors, in which electrostatic forces are generated when a distance between electrodes coupled to a sense structure and electrodes coupled to the underlying substrate is changed. The Coriolis translational motion of the proof mass may be determined based on the generated electrostatic Coriolis force due to angular rotation.

In the illustrated embodiments, the proof mass102comprises two drive structures (first and second drive structures104A,104B) and two sense structures (first and second sense structures106A,106B). However, any suitable number of drive structures and sense structures may be implemented and coupled to the proof mass102.

According to some embodiments, the MEMS device100further comprises an improved stress relief structure108shown inFIG.1A, which couples a frame of a drive and/or sense structure to one or more respective anchors. In the illustrated embodiment, there is provided a stress relief structure108coupled to each of the drive structures104and sense structures106. The stress relief structure108may comprise a means for relieving stress between the drive or sense structure to which the stress relief structure is coupled to and an anchor coupled to the underlying substrate. For example, the stress relief structure108may decrease shear, normal, and/or dynamic resonator stresses affecting the drive or sense structure to which the stress relief structure is coupled. The stress relief structure108may decrease quadrature, in some embodiments.

The stress relief structure108may comprise at least one U-shaped beam and at least one L-shaped beam, as is further described herein. In some embodiments, the stress relief structures may be coupled to respective frames of one or more drive structures and one or more sense structures of the MEMS gyroscope. In particular, for a MEMS gyroscope having decoupled drive and sense structures, both the drive and sense structures may have stress relief structures of the type described herein. Further aspects of the stress relief structure108are described herein.

The one or more respective anchors to which a stress relief structure108is coupled may be disposed substantially outside of the frame of the drive or sense structure to which the stress relief structure is coupled. For example, as shown inFIG.1A, the stress relief structure108coupled to drive structure104is coupled to anchor112which is disposed substantially outside of a frame of drive structure104as well as substantially outside stress relief structure108. Anchors of the MEMS device100, such as anchor112, may be coupled to an underlying substrate. The stress relief structure108may be coupled directly to the respective anchors.

According to some embodiments, the MEMS device100comprises multiple anchor connections111,113for coupling the MEMS device100to a respective anchor. The anchor connections111,113may be substantially symmetric to each other, as shown inFIG.1A(e.g., at anchor112, anchor110). For example, in some embodiments, the MEMS device comprises at least two anchor connections for coupling components of the MEMS device to a respective anchor, the at least two anchor connections being disposed substantially opposite each other (e.g., at diagonals of the anchor). In some embodiments, the MEMS device comprises four anchor connections for coupling components of the MEMS device to a respective anchor, each of the four anchors being disposed substantially opposite each other (e.g., at sides of the anchor).

According to some embodiments, respective anchors of the MEMS device100(e.g., anchor110, anchor112) may be configured having at least two pivot points, as shown inFIG.1A. Further aspects of anchor pivots are described herein, for example, with respect toFIGS.9A-10B.

As described herein, motion may be transferred between a respective drive structure104or sense structure106and the proof mass102. For example, in a drive mode of operation described further herein, motion of a drive structure104may be transferred to the proof mass102causing proof mass102to oscillate. In a sense mode of operation, motion of the proof mass102arising from Coriolis forces may be transferred to the sense structure106. Such transfer of motion may be facilitated by a coupler between the proof mass102and respective drive or sense structures. The coupler may comprise a pair of levers114. The levers114may be coupled together at point118. According to some embodiments, respective levers of the MEMS device may be configured have at least two pivot points, as shown inFIG.1Aat point118.

FIGS.1B-1Cillustrate motion of the example MEMS device100ofFIG.1Ain a drive mode and a sense mode, respectively. For simplicity, not all aspects of the MEMS device100ofFIG.1Aare illustrated inFIGS.1B-1C.

FIG.1Billustrates motion of the example MEMS device100ofFIG.1Ain a drive mode, according to some non-limiting embodiments. As described herein, the MEMS device100ofFIG.1Amay be a MEMS gyroscope configured to detect angular rates through detection of Coriolis forces. In this example, the proof mass102is driven to oscillate along the x-axis, and a Coriolis force arises when the proof mass102undergoes angular motion in the plane of the page, about an out-of-plane axis (e.g., the z-axis) causing the proof mass to be displaced along the y-axis. The MEMS device100may be configured to sense the displacement of the proof mass to measure rotation.

As described herein, the MEMS device100may comprise one or more drive structures104A,104B configured to drive the proof mass along the x-axis. In the illustrated embodiment ofFIG.1B, the MEMS device100comprises two drive structures104A,104B coupled to the proof mass102and disposed substantially opposite each other. Motion of the drive structures104A,104B may be transferred to the proof mass102via levers114. A pair of levers114may be coupled to a respective drive structure104. When the drive structure104oscillates, the pair of levers114may pivot, as shown inFIG.1B, about pivot point115. In some embodiments, each of the levers114have multiple pivot points, as described herein.

FIG.1Cillustrates motion of the example MEMS device100ofFIG.1Ain a sense mode, according to some non-limiting embodiments. In the illustrated embodiment, the sense mode of the MEMS device100comprises motion of the proof mass102along the y-axis. As described herein, the MEMS device100may be configured to sense the rotation of the proof mass102about an out-of-plane axis (e.g., the z-axis) caused by Coriolis forces to detect rotation. In particular, the MEMS device may comprise one or more sense structures106A106B configured to sense motion of the proof mass102along the y-axis to measure Coriolis forces acting upon the proof mass102. In the illustrated embodiment ofFIG.1C, the MEMS device comprises two sense structures106A,106B coupled to the proof mass102and disposed substantially opposite each other.

Motion of the sense structures106A,106B may be coupled to the proof mass102via levers114. A pair of levers114may be coupled to a respective sense structure106. When the proof mass102oscillates, the pair of levers114may pivot, as shown inFIG.1C, about pivot point115. In some embodiments, each of the levers114have multiple pivot points, as described herein.

Although in the illustrated embodiment, the drive and sense modes are along the x and y axes, respectively, in other embodiments, drive and sense motion may be along any combination of the x, y, and/or z axes.

MEMS gyroscopes, as described herein are subject to high non-linearity and shear stress which can cause quadrature. The inventors have recognized that implementing the MEMS device with a stress relief structure and related aspects described herein may be advantageous to improve stress relief of the MEMS device thereby reducing non-linearity and quadrature.FIG.2is an enlarged view of a portion of the example MEMS device ofFIG.1, according to some non-limiting embodiments, highlighting aspects of the technology described herein which may provide for improved stress relief of the MEMS device.

For example,FIG.2illustrates a stress relief structure108which couples a frame of the drive and/or sense structure to a respective anchor, here, anchor112. The anchor112is coupled to a frame122of the stress relief structure108by an arm126. In some embodiments, the arm126may be rigid. In some embodiments, the arm126may be coupled to each of the frame122and the anchor112via one or more springs. The arm126may be coupled to the anchor112at a plurality of points. In some embodiments, connections to the anchor112are disposed symmetrically about the anchor112. For example, as shown inFIG.2, the MEMS device100comprises four connections to the anchor112disposed on respective sides of the anchor112. Further aspects of the anchor connections are described herein.

In some embodiments, the MEMS device100may comprise multiple pivot points about the one or more anchors that are coupled to a drive or sense structure. For example, the MEMS device100comprises three pivot points128. Further aspects of the multiple pivot points are described herein.

As shown inFIG.2, the MEMS device100comprises one or more anchors coupled to an outer frame of the MEMS device. For example, anchor110is shown inFIG.2. As described herein, for example, with respect toFIGS.10A-10B, the anchor110may comprise multiple pivot points (e.g., at least two pivots, at least three pivots) such that the MEMS device100can pivot about each of the multiple pivot points of the anchor110. In some embodiments, an outer frame of the MEMS device100may be coupled to the anchor110via one or more springs120. Connections to the anchor112may be disposed symmetrically about the anchor110. For example, as shown inFIG.2, the MEMS device100comprises four connections to the anchor110disposed on respective sides of the anchor110.

FIG.2illustrates a first lever114of the coupler that couples drive structure104to proof mass102. As shown inFIG.2, lever114comprises a box spring. The MEMS device100may comprise two pivot points115disposed on the box spring, such that the lever114is configured to pivot about the two pivot points115. The pivot points115of lever114shown inFIG.2are disposed on opposite diagonals of the box spring.

FIGS.3-5illustrate aspects of a stress relief structure coupled to a MEMS device.FIG.3is a schematic diagram of an example stress relief structure108coupled to a drive structure of a MEMS inertial sensor, according to some non-limiting embodiments.

In the illustrated embodiment ofFIG.3, the stress relief structure104is coupled to a frame122of a drive structure104. In some embodiments, a stress relief structure may additionally or alternatively be coupled to one or more sense structures of the MEMS device. As shown inFIG.3, the drive structure104may be disposed substantially inside of the stress relief structure104.

As described herein, the stress relief structure108may comprise a means for relieving stress between the drive or sense structure to which the stress relief structure is coupled to and an anchor coupled to the underlying substrate. For example, the stress relief structure108may decrease shear, normal, and/or dynamic resonator stresses affecting the drive or sense structure to which the stress relief structure is coupled. The stress relief structure108may decrease quadrature, in some embodiments.

The stress relief structure108may comprise a frame140comprised of a plurality of beams. For example, as shown in the illustrated embodiment, frame140comprises a plurality of L-shaped beams132and a plurality of U-shaped beams134.

At least one of the plurality of L-shaped beams132may be coupled to the drive or sense structure disposed substantially inside the frame140of the stress relief structure108. In the illustrated embodiment, the frame140comprises four L-shaped beams. The frame140may comprise a respective one of the plurality of L-shaped beams132in each corner of the frame140.

Each L-shaped beam may comprise two legs141joined together at a vertex142. For example, a first end of a leg141may be coupled to the drive structure104and a second end of the leg141may be coupled to the other leg141of the L-shaped beam132at the vertex142. Accordingly, the L-shaped beam132may be coupled to the drive structure104at two points, a first point144A by a first leg141and a second point144B by a second leg141.

In some embodiments, the legs141have substantially the same length. In other embodiments, one of the legs141is longer than the other of the two legs141. In some embodiments, the legs141are integral with each other. In other embodiments, the legs141are coupled together at the vertex142by any suitable coupling means.

U-shaped beams134and L-shaped beam132may be relatively more rigid than spring124coupling the stress relief structure108to anchors130in a drive mode (e.g., motion along the x-axis) and sense mode (e.g., motion along the y-axis). In some embodiments, the frame140of the stress relief structure108, including the U-shaped beams134and L-shaped beams132, are made of silicon. As described herein, the U-shaped beams134may provide stress relief for the MEMS device100. The L-shaped beams132may provide stress relief for the MEMS device100and may additionally ensure there is no inadvertent tilting of the drive structure104and stress relief structure108.

At least one U-shaped beam134may be provided being coupled to an L-shaped beam132of the frame140. For example, the frame comprises four U-shaped beams134in the illustrated embodiment. A respective one of the plurality of U-shaped beams134is coupled to a respective one of the plurality L-shaped beams132such that the frame140comprises a U-shaped beam134and a L-shaped beam132in each of the four corners of the frame140.

Each U-shaped beam134may comprise two legs146,148coupled together by a spacer147. The legs146,148may be substantially parallel to each other. The spacer147may separate a first leg146from a second leg148of the U-shaped beam134along a horizontal axis (e.g., an x-axis). Each of the legs146,148may have a largest dimension along a vertical axis (e.g., a y-axis) substantially perpendicular to the horizontal axis. In the illustrated embodiment, the first leg146is longer than the second leg148. In other embodiments, the first and second legs146,148may have a same length.

As described herein, a U-shaped beam134may be coupled to an L-shaped beam132. As shown inFIG.3, the U-shaped beam134is coupled to the vertex142of the L-shaped beam132, where legs141of the L-shaped beam132are coupled together.

In some embodiments, one of more of the U-shaped beams134may be coupled to each other. For example, as shown inFIG.3, a coupler150is provided for coupling two U-shaped beams134together (via legs146of the respective U-shaped beams134). Frame140comprises two couplers150for coupling adjacent pairs of U-shaped beams134together.

At least one of the plurality of U-shaped beams134may be coupled to an anchor130via a spring124. As shown in the illustrated embodiment, the anchor130is disposed substantially outside of the frame140and outside of the drive structure104. Springs124may be provided for coupling the U-shaped beams134of the frame140of the stress relief structure108to the anchors130.

As shown in the illustrated embodiments, the stress relief structure108is symmetric. For example, the stress relief structure108, including frame140, exhibits in-plane (e.g., x-y plane) rotational symmetry. In particular, the stress relief structure108has second order rotational symmetry. For example, the configuration of the stress relief structure108appears identically when the stress relief structure108is rotated by 180 degrees.

FIG.4illustrates a portion of the example MEMS device100ofFIG.1illustrating the example stress relief structure108ofFIG.3being coupled to a drive structure104of the MEMS device100, according to some non-limiting embodiments. In particular,FIG.4illustrates the stress relief structure108ofFIG.3implemented as part of MEMS device100. As shown inFIG.4, the drive structure104is disposed substantially within the frame140of the stress relief structure108. AlthoughFIG.4illustrates only a single stress relief structure108and a single drive structure104, it should be understood that one or more additional stress relief structures may be implemented, for example, being coupled to a second drive structure of the MEMS device100or to one or more sense structures of the MEMS device100as shown inFIG.5.

FIG.5illustrates an enlarged portion of the example MEMS device100ofFIG.1illustrating the example stress relief structure108ofFIG.3being coupled to a sense structure106of the MEMS device100, according to some non-limiting embodiments. As shown inFIG.5, the sense structure106is disposed substantially within the frame140of the stress relief structure108. In some embodiments, both of a drive structure104and a sense structure106may be coupled to a respective stress relief structure106. In some embodiments, for example, as shown inFIG.1A, the MEMS device100may comprise a respective stress relief structure108coupled to each drive structure104and each sense structure106. AlthoughFIG.5illustrates only a single stress relief structure108and a single sense structure106, it should be understood that one or more additional stress relief structures may be implemented, for example, being coupled to a second sense structure of the MEMS device100.

FIG.6is a schematic diagram illustrating aspects of the example MEMS device100ofFIG.1when in motion, according to some non-limiting embodiments. In particular,FIG.6illustrates two pivot points128A,128B of the MEMS device100. The pivots points128A,128B are disposed on opposing diagonals of the anchor112. Accordingly, the MEMS device100may be configured to pivot about anchor112at pivot points128A,128B.

One or more of pivot points128A,128B may be static stress relief pivot points that act as a stress relief mechanism for the static stress deformations resulting from environmental and package stresses. It should be appreciated that any number of static stress relief pivot points may be implemented. For example, in some embodiments, the MEMS device100may comprise a single static stress relief pivot point about anchor112. In the illustrated embodiment, pivot point128B serves as a static stress relief pivot point. In some embodiments, one or more additional pivot points may be provided for static stress relief.

In some embodiments, one or more of pivot points128A,128B may serve as dynamic pivot points, for example, to facilitate a drive mode of the MEMS device100. In particular, pivot point128A is disposed at the point where the lever114is coupled to the anchor112. During drive and sense modes of operation, as shown inFIGS.1B-1C, levers114may pivot about pivot point128A. Accordingly, pivot point may be referred to as a dynamic pivot as it facilitates the motion of the levers114in drive and sense modes of the MEMS device100.

As shown inFIG.6, two anchors112may be coupled to drive structure via arms126. In some embodiments, such as the embodiment illustrated inFIG.6, there may be multiple pivot points128A,128B about each of the anchors112.

FIGS.7A-7Bare enlarged views of the example MEMS device100ofFIG.1illustrating mechanically aspects of the schematic diagram ofFIG.6, according to some non-limiting embodiments. As shown inFIG.7A, dynamic pivot point128A is provided where lever114is coupled to anchor112. Static stress relief pivot point128B is also provided. As shown inFIG.7A, the static stress relief pivot point128B is disposed diagonally opposite pivot point128A. An additional pivot point128C is provided about anchor112. Pivot point128C may be a static stress relief pivot point.

FIG.7Billustrates an enlarged view of the portion of the example MEMS device100shown inFIG.7A, according to some non-limiting embodiments.FIG.7Bdepicts pivot points128disposed about anchor112, as described herein.

The inventors have recognized that configuring the anchors of the MEMS device with at least two pivot points may significantly reduce quadrature experienced by the MEMS device which would otherwise result from diagonal rotation of the drive and sense structures by releasing stress of the MEMS device.

FIGS.8-10Billustrate aspects of the MEMS device relating to symmetric anchor connections.FIG.8is an enlarged view of the example MEMS device100ofFIG.1illustrating symmetric anchor connections, according to some non-limiting embodiments. As described herein, the MEMS device100may comprise a plurality of anchors for coupling components (e.g., the proof mass102) of the MEMS device100to an underlying substrate.FIG.8illustrates anchor112, which, as described herein, may be coupled to levers114as well as to a drive or sense structure (e.g., via stress relief structure108). Although only a single anchor112is shown and labeled inFIG.8, the MEMS device100may include a plurality of anchors configured in the same manner as anchor112(e.g., being coupled to a lever114and stress relief structure108and having the symmetric anchor connections described herein).

FIG.8further illustrates anchor110. Anchor110may be coupled to an outer frame of the MEMS device100, as is further described herein, for example, with respect toFIGS.10A-10B. Although only a single anchor110is shown and labeled inFIG.8, the MEMS device100may include a plurality of anchors configured in the same manner as anchor112(e.g., being coupled to an outer frame of the MEMS device100and having the symmetric anchor connections described herein). The inventors have recognized that implementing multiple anchor connections which may be disposed symmetrically about an anchor in a MEMS device may improve the symmetry of the MEMS device, thereby reducing non-linearity and quadrature.

FIG.9Aillustrates an embodiment of the MEMS device having two anchor connections to an anchor112of the MEMS device100which is coupled to a drive structure (e.g., via stress relief structure108). For example, in the illustrated embodiment ofFIG.9A, the anchor connections902are coupled to opposite diagonals of the anchor112. Anchor connections902may be flexible in some embodiments, e.g., comprising springs. In some embodiments, anchor connections902may not be flexible.

FIG.9Afurther illustrates pivot points128A-C. As described herein, one or more of pivot points128B-128C may be static stress relief pivot points for relieving the static stress deformations resulting from environmental and package stresses. Pivot point128A may serve as a dynamic pivot point.

FIG.9Billustrates an embodiment of the MEMS device100having four anchor connections902to an anchor112of the MEMS device100which is coupled to a drive structure104(e.g., via stress relief structure108). For example, in the illustrated embodiment ofFIG.9B, each respective one the four anchor connections902is coupled to a respective side of the anchor112.

In bothFIGS.9A-9B, the anchor connections902are coupled to the drive structure104(e.g., through the stress relief structure108) with a drive-anchor connector904. Drive anchor connector904may be coupled to the anchor connections902through the static stress relief pivots128B,128C that act as a stress relief structure for the static stress deformations resulting from environmental and package stresses. Drive-anchor connector904may comprise arm126previously described herein. In some embodiments, drive-anchor connector904is coupled to the drive structure104(e.g., via stress relief structure108) by one or more springs (e.g., folded springs, as shown in the illustrated embodiment). In some embodiments, a lever114may be coupled to the anchor connections902at the pivot point128A that acts as a dynamic AC pivot during the drive and sense modes of the MEMS device100as shown inFIGS.1B-1C.

FIG.10Aillustrates an embodiment of the MEMS device100having two anchor connections1002to an anchor110of the MEMS device100which is coupled to an outer frame1004of the MEMS device100. As described herein, MEMS device100may comprise an outer frame1004wherein the proof mass102is disposed substantially within the outer frame1004. As shown inFIGS.10A-10B, anchor110may be coupled to the outer frame1004of the MEMS device100via a plurality of connections1002.

In the illustrated embodiment ofFIG.10A, the anchor connections1002are coupled to opposite diagonals of the anchor110. In the illustrated embodiments ofFIG.10B, the MEMS device100comprises four anchor connections to anchor110. In the illustrated embodiment ofFIG.10B, each respective one of the four anchor connections1002may be coupled to a respective side of the anchor110.

Anchor connections1002may be flexible in some embodiments, e.g., comprising springs. In some embodiments, anchor connections1002may not be flexible.

In bothFIGS.10A-10B, the anchor connections1002are coupled to the outer frame1004via couplers1010. The MEMS device100may comprise dynamic AC pivot points1008joining the anchor connections1002to the couplers1010and to the outer frame1004. As described herein, dynamic pivot points may facilitate motion of components of the MEMS device100(e.g., the outer frame1004) during drive and sense modes as shown inFIGS.1B-1C. MEMS device100may further comprise a plurality of static stress relief pivot points1006. As described herein, static stress relief pivot points act as a stress relief structure for the static stress deformations of the MEMS device100resulting from environmental and package stresses.

As described herein, the stress relief structures and related aspects may be implemented in a MEMS gyroscope (e.g., a MEMS gyroscope configured to sense roll, pitch and/or yaw rotation). MEMS device100may form a portion of a larger MEMS device.FIG.11Aillustrates an example MEMS gyroscope1100having four proof masses1102, according to some non-limiting embodiments. In some embodiments, the MEMS1100gyroscope ofFIG.11Amay be configured to sense rotation about two or more axes. The MEMS gyroscope1100shown inFIG.11Acomprises four quadrants1104coupled together and arranged in a 2×2 formation. Each quadrant of the MEMS gyroscope1100ofFIG.11Amay have a proof mass1102and the stress relief structures and related mechanisms described herein (e.g., having additional pivot points and/or symmetric anchor connections coupling respective frames of drive and/or sense structures to an anchor). For example, each quadrant1104may be configured with some or all of the features of MEMS device100.

The proof masses1102in the respective quadrants may be configured to move anti-phase relative to an adjacent proof mass1102. That is, a proof mass1102may be configured to move in an opposite direction along a first axis in a drive mode relative to the motion of proof masses vertically and horizontally adjacent to the proof mass1102, and in a same direction along the first axis relative to motion of a proof mass diagonally adjacent to the proof mass1102. In a sense mode, the proof mass1102may be configured to move in an opposite direction along a second axis substantially perpendicular to the first axis relative to motion of the proof masses vertically and horizontally adjacent to the proof mass1102, and in a same direction along the second axis relative to the motion of a proof mass diagonally adjacent to the proof mass1102.

FIG.11Billustrates an example MEMS gyroscope1110having twelve proof masses, according to some non-limiting embodiments. In particular,FIG.11Billustrates an example of a MEMS gyroscope1110having three columns1120A,1120B,1120C, each column being configured to sense rotation about a respective axis (e.g., pitch, roll, or yaw rotation). In some embodiments, the MEMS gyroscope1110may be configured having two columns, with one or more columns being configured to sense rotation about multiple axes (e.g., one or more of pitch, roll, and/or yaw rotation). Each column may comprise at least three proof masses1102, with the MEMS gyroscope1110of the illustrated embodiment having four proof masses per column. The MEMS gyroscope1110ofFIG.11Bmay be implemented having the stress relief structures and related mechanisms described herein (e.g., having additional pivot points and/or symmetric anchor connections coupling respective frames of drive and/or sense structures to an anchor). For example, in some embodiments, the MEMS gyroscope1110ofFIG.11Bmay implement the stress relief structures and related mechanisms described herein in one or more of the columns of the MEMS gyroscope1110(e.g., in a column of the MEMS gyroscope1110configured to sense yaw rotation).

As described herein, MEMS devices having stress relief structures and additional aspects of stress relief of the types described herein may be deployed in various settings to detect angular rates, including sports, healthcare, military, and industrial applications, among others. A MEMS device (e.g., a MEMS inertial sensor such as a MEMS gyroscope, for example) may be mounted as a wearable sensor deployed in monitoring sports-related physical activity and performance, patient health, military personnel activity, or other applications of interest of a user. A MEMS gyroscope may be disposed in a smartphone, and may be configured to sense roll, pitch and/or yaw angular rates.

FIG.12is a block diagram illustrating a system1200comprising a MEMS device1202, a power unit1204, sense circuitry1206and input/output (I/O) interface1208. MEMS device1202may comprise any one or a combination of the MEMS devices described herein. In some embodiments, the MEMS device(s) may comprise a MEMS gyroscope configured to sense roll, pitch and/or yaw angular rates.

System1200may periodically transmit, via wired connections or wirelessly, data representing sensed angular rates to an external monitoring system, such as a computer, a smartphone, a tablet, a smartwatch, smartglasses, or any other suitable receiving device. I/O interface1208may be configured to transmit and/or receive data via Wi-Fi, Bluetooth, Bluetooth Low Energy (BLE), Zigbee, Thread, ANT, ANT+, IEEE 1202.15.4, IEEE 1202.11.ah, or any other suitable wireless communication protocol. Alternatively, or additionally, I/O interface1208may be configured to transmit and/or receive data using proprietary connectivity protocols. I/O interface1208may comprise one or more antennas, such as a microstrip antenna. In some embodiments, I/O interface1208may be connected to a cable, and may be configured to transmit and/or receive signals through the cable.

System1200may be powered using power unit1204. Power unit1204may be configured to power some or all of sense circuitry1206, I/O interface1208, and/or MEMS device1202. In some embodiments, power unit1204may comprise one or more batteries. System1200may, in at least some embodiments, consume sufficiently little power to allow for its operation for extended periods based solely on battery power. The battery or batteries may be rechargeable in some embodiments. Power unit1204may comprise one or more lithium-ion batteries, lithium polymer (LiPo) batteries, super-capacitor-based batteries, alkaline batteries, aluminum-ion batteries, mercury batteries, dry-cell batteries, zinc-carbon batteries, nickel-cadmium batteries, graphene batteries or any other suitable type of battery. In some embodiments, power unit1204may comprise circuitry to convert AC power to DC power. For example, power unit1204may receive AC power from a power source external to system1200, such as via I/O interface1208, and may provide DC power to some or all the components of system1200. In such instances, power unit1204may comprise a rectifier, a voltage regulator, a DC-DC converter, or any other suitable apparatus for power conversion.

Power unit1204may comprise energy harvesting components and/or energy storage components, in some embodiments. Energy may be harvested from the surrounding environment and stored for powering the system1200when needed, which may include periodic, random, or continuous powering. The type of energy harvesting components implemented may be selected based on the anticipated environment of the system1200, for example based on the expected magnitude and frequency of motion the system1200is likely to experience, the amount of stress the system is likely to experience, the amount of light exposure the system is likely to experience, and/or the temperature(s) to which the system is likely to be exposed, among other possible considerations. Examples of suitable energy harvesting technologies include thermoelectric energy harvesting, magnetic vibrational harvesting, electrical overstress harvesting, photovoltaic harvesting, radio frequency harvesting, and kinetic energy harvesting. The energy storage components may comprise supercapacitors in some embodiments.

As described above, MEMS devices of the types described herein may be deployed in various settings, for example, to detect angular rates. One such setting is in automobiles, or other vehicles, such as boats or aircrafts.FIG.13illustrates schematically an automobile1300comprising a system1200, according to some non-limiting embodiments. System1200may be disposed in any suitable location of automobile1300. In some embodiments, the system1200may comprise a package or housing attached to a suitable part of the automobile1300, with the MEMS device inside. In some embodiments, system1200may be configured to sense roll, pitch and/or yaw angular rates. System1200may be configured to provide, using I/O interface1208, sensed angular rates to a computer system disposed in automobile1300and/or to a computer system disposed on a base station outside automobile1300.

Another setting in which MEMS devices having stress relief aspects of the types described herein may be used is in sensor devices for sports applications, such as tennis, swimming, running, baseball, or hockey, among other possibilities. In some embodiments, a MEMS device of the types described herein may be a wearable fitness device. In other embodiments, the sensor may be part of a piece of sporting equipment, such as being part of a tennis racket, baseball bat, or hockey stick. Sense data from the sensor may be used to assess performance of the user.

Aspects of the technology described herein may provide one or more benefits, some of which have been previously described. Aspects of the technology described herein provide an improved stress relief structure and other aspects for improving stress relief of a MEMS device, such as a MEMS gyroscope. It should be appreciated that not all aspects and embodiments necessarily provide all of the benefits described herein. Further, it should be appreciated that aspects of the technology described herein may provide additional benefits to those described herein.

The expressions “substantially in a direction” and “substantially parallel to a direction” should be interpreted herein as parallel to the direction or angled with respect to the direction by less than 20°, including any value within that range.

The terms “approximately” and “about” may be used to mean±20% of a target value in some embodiments, within ±10% of a target value in some embodiments, within ±5% of a target value in some embodiments, and yet within ±2% of a target value in some embodiments. The terms “approximately” and “about” may include the target value.