阅读说明：本技术 具有偏移锚负载抑制的mems传感器 (MEMS sensor with offset anchor load rejection ) 是由 M·汤普森 H·乔哈里-加勒 L·巴尔达萨雷 S·尼灿 K·威廉姆斯 于 2018-08-27 设计创作，主要内容包括：一种MEMS传感器包括MEMS层、盖层和基板层。MEMS层包括悬置的弹簧-质块系统,该悬置的弹簧-质块系统响应于感测到的惯性力而移动。悬置的弹簧-质块系统从一个或多个锚悬置。锚通过锚定部件耦合到盖层和基板层中的每一个。锚定部件被偏移,使得施加到盖层或基板层的力引起锚的旋转,并且使得悬置的弹簧-质块系统基本上保持在原始MEMS层内。(A MEMS sensor includes a MEMS layer, a cap layer, and a substrate layer. The MEMS layer includes a suspended spring-mass system that moves in response to a sensed inertial force. The suspended spring-mass system is suspended from one or more anchors. The anchor is coupled to each of the cap layer and the substrate layer by an anchor member. The anchor member is biased such that a force applied to the cap layer or substrate layer causes rotation of the anchor and such that the suspended spring-mass system remains substantially within the original MEMS layer.)

1. A microelectromechanical MEMS device comprising:

an anchor system bonded to the cap layer and to the substrate layer;

a proof mass coupled to an anchor system via a spring;

a sensing element coupled between the proof mass and the substrate layer, wherein the sensing element outputs a signal in response to movement of the proof mass in a first direction;

wherein a force applied to the anchor system moves the anchor system and the spring in a first direction, an

Wherein the proof mass remains substantially stationary when the first force is applied to the anchor system.

2. The MEMS device of claim 1, wherein the anchor system rotates at a connection with the spring when the first force is applied.

3. The MEMS device of claim 2, wherein movement of the anchor system urges the proof mass in a negative first direction relative to the anchor system.

4. The MEMS device of claim 3, wherein movement of the anchor system in the first direction balances movement of the proof mass in the negative first direction, thereby causing the proof mass to remain substantially stationary.

5. The MEMS device of claim 1, wherein the anchor system comprises an anchor block coupled to the post, the standoff, and the spring, and wherein the post is bonded to the cap layer and the standoff is bonded to the substrate layer.

6. The MEMS device of claim 5, wherein the posts and standoffs are misaligned.

7. The MEMS device of claim 6, wherein the posts and standoffs do not overlap.

8. The MEMS device of claim 6, wherein the post and the support substantially overlap.

9. The MEMS device of claim 5, wherein the posts are connected to a top of the anchor block and the cap layer is above the anchor block, and wherein the standoffs are connected to a bottom of the anchor block and the substrate layer is below the anchor block.

10. The MEMS device of claim 6, wherein misalignment of the strut and the support translates and rotates the anchor block when the first force is applied.

11. The MEMS device of claim 10, wherein a combination of translation and rotation of the anchor system maintains the proof mass substantially stationary.

12. The MEMS device of claim 1, wherein the MEMS device is an accelerometer, magnetometer, gyroscope, barometer, or microphone.

13. The MEMS device of claim 5, wherein the anchor system further comprises a second anchor block coupled to the proof mass via a second spring, wherein the second anchor block is coupled to the support post and a second standoff, and wherein the second standoff is bonded to the substrate.

14. The MEMS device of claim 13, wherein a force applied to the anchor system moves the anchor block, the second anchor block, the spring, and the second spring in a first direction, and wherein the proof mass remains substantially stationary when the first force is applied to the anchor system.

15. The MEMS device of claim 14, wherein the support post is misaligned relative to the support and the second support, and wherein the anchor block and the second anchor block rotate when the first force is applied to move the proof mass in the negative first direction.

16. The MEMS device of claim 15 wherein movement of the anchoring system in the first direction balances motion of the proof mass in the negative first direction due to rotation of the anchoring system, resulting in the proof mass remaining substantially stationary.

17. A microelectromechanical MEMS device comprising:

a cover comprising a first anchoring system;

a substrate comprising a second anchoring system, wherein at least one sensing electrode is located on a surface of the substrate; and

a MEMS layer bonded to each of the lid and the substrate to define a cavity, wherein the MEMS layer comprises a suspended spring-mass system, wherein the suspended spring-mass system comprises:

at least one movable mass, wherein at least a portion of the at least one movable mass is located at a first distance from the at least one sensing electrode to form at least one sensing capacitor; and

at least one anchor mass coupled to the at least one movable mass to suspend the at least one movable mass within the MEMS layer, wherein the at least one anchor mass is coupled to at least a portion of the first anchor system and at least a portion of the second anchor system, and wherein in response to a force in a direction perpendicular to the MEMS layer, the first anchor system and the second anchor system cause the at least one anchor fixed mass to move in the direction and cause the at least one movable mass to remain a first distance from the at least one sensing electrode to form the at least one sensing capacitor.

18. The MEMS device of claim 17, further comprising:

a strut through which the at least one anchored mass is coupled to a first anchoring system; and

a mount, wherein the at least one anchor mass is coupled to a second anchor system through the mount.

19. The MEMS device of claim 18, wherein the posts and standoffs are misaligned.

20. A microelectromechanical MEMS device comprising:

a cover;

a substrate, wherein at least one sensing electrode is located on a surface of the substrate;

a MEMS layer bonded to each of the lid and the substrate to define a cavity, wherein the MEMS layer comprises a suspended spring-mass system;

at least one strut coupled to the cover and to one or more anchoring masses of the suspended spring-mass system;

at least one standoff coupled to the cover and to one or more anchor masses of the suspended spring mass system,

wherein the at least one standoff is offset relative to the at least one strut such that the at least one standoff and the at least one strut do not overlap on opposing faces of the one or more anchored masses, an

Wherein, in response to a force perpendicular to the MEMS layer, the one or more anchor masses move in the direction of the force and at least one proof mass of the spring-mass system is substantially stationary.

Background

Many articles such as smartphones, smartwatches, tablets, automobiles, aerial drones (aerial drones), appliances, aircraft, motion aids, and game controllers may utilize motion sensors during their operation. In many applications, various types of motion sensors (such as accelerometers and gyroscopes) may be analyzed separately or together to determine various information for a particular application. For example, gyroscopes and accelerometers may be used in gaming applications (e.g., smart phones or game controllers) to capture complex motions of a user, drones and other aircraft may determine orientation based on gyroscope measurements (e.g., roll, pitch, and yaw), and vehicles may utilize the measurements to determine direction (e.g., for dead reckoning) and safety (e.g., to identify a slip or roll condition).

Motion sensors such as accelerometers and gyroscopes may be fabricated as micro-electromechanical (MEMS) sensors fabricated using semiconductor fabrication techniques. MEMS sensors can include a movable proof mass that can respond to forces such as linear acceleration (e.g., for MEMS accelerometers), angular velocity (e.g., for MEMS gyroscopes), and magnetic fields. The operation of the movable proof mass by these forces may be measured based on the movement of the proof mass in response to the forces. In some implementations, this movement is measured based on the distance between the movable proof mass and the sensing electrode, which form a capacitor for sensing the movement.

MEMS sensors may be constructed from multiple layers bonded together, such as a cap layer, a MEMS layer, and a substrate layer. The movable MEMS component of the MEMS sensor may be located within the MEMS layer and anchored to one or both of the cap layer and the substrate layer. If the position of the MEMS component relative to the sensing electrode is different from the expected position, the capacitance used to determine the inertial force may be incorrect. Deviations from the expected position of the MEMS component can be caused by a variety of conditions, such as manufacturing tolerances, manufacturing errors, stresses experienced during packaging with other components or sensor operation.

Disclosure of Invention

In an embodiment of the present disclosure, an exemplary microelectromechanical (MEMS) device includes: an anchor system bonded to the cap layer and to the substrate layer, an proof mass coupled to the anchor system via a spring, and a sensing element coupled between the proof mass and the substrate layer, wherein the sensing element outputs a signal in response to movement of the proof mass in a first direction. In an embodiment, a force applied to the anchor system moves the anchor system and the spring in a first direction, and the proof mass remains substantially stationary when the first force is applied to the anchor system.

In an embodiment of the present disclosure, an exemplary microelectromechanical (MEMS) device includes: a cover comprising a first anchoring system; a substrate comprising a second anchoring system, wherein at least one sensing electrode is located on a surface of the substrate; and a MEMS layer bonded to each of the lid and the substrate to define a cavity, wherein the MEMS layer comprises a suspended spring-mass system. In an embodiment, a suspended spring-mass system comprises: at least one movable mass, wherein at least a portion of the at least one movable mass is located at a first distance from the at least one sensing electrode to form at least one sensing capacitor; and at least one anchor mass coupled to the at least one movable mass to suspend the at least one movable mass within the MEMS layer, wherein the at least one anchor mass is coupled to at least a portion of the first anchor system and at least a portion of the second anchor system, and wherein in response to a force in a direction perpendicular to the MEMS layer, the first anchor system and the second anchor system move the at least one anchor mass in the direction of the force and cause the at least one movable mass to remain a first distance from the at least one sensing electrode to form at least one sensing capacitor.

In an embodiment of the present disclosure, an exemplary microelectromechanical (MEMS) device includes: a cover; a substrate, wherein at least one sensing electrode is located on a surface of the substrate; and a MEMS layer bonded to each of the lid and the substrate to define a cavity, wherein the MEMS layer comprises a suspended spring-mass system. In an embodiment, the MEMS device further comprises: at least one strut coupled to the cover and one or more anchoring masses of the suspended spring-mass system; and at least one standoff coupled to the cover and the one or more anchored masses of the suspended spring-mass system, wherein the at least one standoff is offset relative to the at least one support post such that the at least one standoff and the at least one support post do not overlap on opposing faces of the one or more anchored masses, and wherein, in response to a force perpendicular to the MEMS layer, the one or more anchored masses move in the direction of the force and the at least one proof mass of the spring-mass system is substantially stationary.

Drawings

The above and other features of the present disclosure, its nature and various advantages will become more apparent from the following detailed description considered in conjunction with the accompanying drawings in which:

FIG. 1 shows an illustrative motion sensing system in accordance with an embodiment of the present disclosure;

FIG. 2 shows an illustrative MEMS sensor in accordance with an embodiment of the present disclosure;

FIG. 3A shows a cross-section of components of an illustrative MEMS sensor with vertically stacked anchors in accordance with some embodiments of the present disclosure;

FIG. 3B illustrates a cross-section of components of an illustrative MEMS sensor having vertically stacked anchors experiencing a vertical compressive force in accordance with some embodiments of the present disclosure;

FIG. 4 shows an illustrative MEMS layer of a MEMS accelerometer with vertically stacked anchors experiencing a vertical compressive force in accordance with some embodiments of the present disclosure;

FIG. 5A illustrates a cross-section of components of an illustrative MEMS sensor with offset anchors in accordance with some embodiments of the present disclosure;

FIG. 5B illustrates a cross-section of components of an illustrative MEMS sensor with offset anchors experiencing a vertical compressive force according to some embodiments of the present disclosure; and

figure 6 illustrates an exemplary MEMS layer of a MEMS accelerometer with offset anchors experiencing a vertical compressive force according to some embodiments of the present disclosure.

Detailed Description

Inertial sensors are designed and fabricated as micro-electromechanical (MEMS) accelerometers. The MEMS layer is formed using semiconductor processing techniques to include the mechanical components of the sensor and electrical connections to other components of the MEMS accelerometer (such as CMOS circuitry located within or outside the sensor die, such as a CMOS layer that also serves as a substrate or cap layer within the sensor die). The MEMS layer is hermetically sealed within other semiconductor layers, such as underlying substrate layers and cap layers.

The MEMS layer includes a suspended spring-mass system, wherein one or more proof masses are suspended within the MEMS layer by springs. The proof mass is constrained in its movement by springs and, in some embodiments, by additional components such as the mass and levers. These springs and additional components collectively facilitate motion of the proof mass along one or more axes for sensing linear acceleration. A sense electrode is positioned adjacent each proof mass (or additional sense masses in some embodiments) in the direction of the sensed linear acceleration, forming a capacitor that varies based on the distance between the proof mass and the sense electrode. In an exemplary z-axis accelerometer, the sensing electrodes are located on another layer parallel to the proof mass.

The suspended spring-mass system is suspended from an anchor, which in turn is secured to one or both of the cap layer and the substrate layer such that the anchor does not move in response to the sensed inertial forces. In an embodiment of the present disclosure, the anchor comprises two anchor masses within the MEMS layer. Each anchor mass is joined to both the cap layer and the substrate layer by a respective anchor member. The engagement of the anchor mass with the anchor member is offset (e.g., the engagement from the anchor mass to the substrate anchor member is offset relative to the engagement of the anchor mass to the lid anchor member) such that at least 75% of the engagements are non-overlapping.

In various circumstances, such as due to fabrication of the MEMS inertial sensor, assembly with other components in the device, and end use applications, forces may be applied to the cap layer and/or substrate layer. Due to the offset of the engagement of the anchor mass with the anchor member, the force imparted to the anchor mass from the cover or substrate (e.g., via the anchor member) causes rotation of the anchor mass. This results in a rotational displacement of the anchored mass in the direction of the force and a counteracting displacement of the suspended spring-mass system in the opposite direction. Thus, the suspended spring-mass system remains substantially aligned within the MEMS layer, with an angle to the plane of the original MEMS layer position of less than 5%.

Fig. 1 depicts an exemplary motion sensing system 10 according to some embodiments of the present disclosure. Although specific components are depicted in fig. 1, it should be understood that other suitable combinations of sensors, processing components, memory, and other circuitry may be utilized as desired for different applications and systems. In an embodiment as described herein, the motion sensing system may include at least the MEMS inertial sensor 12 (e.g., a single-axis or multi-axis accelerometer, a single-axis or multi-axis gyroscope, or a combination thereof) and support circuitry, such as processing circuitry 14 and memory 16. In some embodiments, one or more additional sensors 18 (e.g., additional MEMS gyroscopes, MEMS accelerometers, MEMS microphones, MEMS pressure sensors, and compasses) may be included within the motion processing system 10 to provide an integrated motion processing unit ("MPU") (e.g., including 3-axis MEMS gyroscope sensing, 3-axis MEMS accelerometer sensing, microphones, pressure sensors, and compasses).

The processing circuitry 14 may include one or more components that provide the necessary processing based on the requirements of the motion processing system 10. In some embodiments, the processing circuitry 14 may include hardware control logic that may be integrated within the chip of the sensor (e.g., on the substrate or cap of the MEMS inertial sensor 12 or other sensor 18, or on an adjacent portion of the chip to the MEMS inertial sensor 12 or other sensor 18) to control the operation of the MEMS inertial sensor 12 or other sensor 18 and to perform processing aspects of the MEMS inertial sensor 12 or other sensor 18. In some embodiments, the MEMS inertial sensor 12 and other sensors 18 may include one or more registers that allow aspects of the operation of the hardware control logic to be modified (e.g., by modifying the values of the registers). In some embodiments, the processing circuitry 14 may also include a processor, such as a microprocessor, that executes software instructions, such as software instructions stored in the memory 16. The microprocessor may control the operation of the MEMS inertial sensor 12 by interacting with hardware control logic and processing signals received from the MEMS inertial sensor 12. The microprocessor may interact with other sensors in a similar manner.

Although IN some embodiments (not depicted IN FIG. 1), MEMS inertial sensors 12 or other sensors 18 may communicate directly with external circuitry (e.g., via a serial bus or direct connection to sensor outputs and control inputs), IN one embodiment, processing circuitry 14 may process data received from MEMS inertial sensors 12 and other sensors 18 and communicate with external components via a communication interface 20 (e.g., an SPI or I2C bus, or a Controller Area Network (CAN) or local interconnect network (L IN) bus IN automotive applications). processing circuitry 14 may convert signals received from MEMS inertial sensors 12 and other sensors 18 into appropriate units of measurement (e.g., based on settings provided by other computing units communicating over communication bus 20) and perform more complex processing to determine measurements such as heading or Euler angles, and IN some embodiments to determine from the sensor data whether particular activity (e.g., walking, running, braking, skidding, rolling, etc.) is occurring.

In some embodiments, certain types of information may be determined in a process that may be referred to as sensor fusion based on data from the plurality of MEMS inertial sensors 12 and other sensors 18. By combining information from various sensors, information useful in various applications (such as image stabilization, navigation systems, automotive control and security, dead reckoning, remote control and gaming devices, activity sensors, three-dimensional cameras, industrial automation, and many other applications) may be able to be accurately determined.

An exemplary MEMS inertial sensor (e.g., MEMS inertial sensor 12) may include one or more movable proof masses configured in a manner that allows the MEMS inertial sensor (e.g., MEMS accelerometer or MEMS gyroscope) to measure a desired force (e.g., linear acceleration, angular velocity, magnetic field, etc.) along an axis. In some embodiments, one or more movable proof masses may be suspended from anchor points, which may refer to any portion of the MEMS sensor that is fixed, such as anchors attached to a substrate layer (e.g., CMOS layer) parallel to the MEMS layer of the device, a cap layer parallel to the MEMS layer, a frame of the MEMS layer of the device, or any other suitable portion of the MEMS device that is fixed relative to the movable proof mass. The proof masses may be arranged in a manner such that they move in response to a measured force. The motion of the detection mass relative to a fixed surface (e.g., fixed sensing electrodes extending into the MEMS layer or positioned parallel to the movable mass on the substrate) in response to the measured force is measured and scaled to determine the desired inertial parameters.

MEMS inertial sensors are used in a wide variety of end-use environments, ranging from wearable and internet of things (IoT) devices in consumer applications to vehicle and industrial environments. A particular MEMS inertial sensor package can be used in hundreds or even thousands of different end-use devices, each with its own unique assembly and packaging with other device components and unique end-use applications. Many of these devices are miniaturized and require assembly of the MEMS inertial sensor package in close proximity to other components or in a manner that subjects the MEMS inertial sensor to external stresses. Thus, MEMS inertial sensor packages can be subjected to a variety of forces due to manufacturing, assembly, and end-use applications. In some embodiments, these forces may be applied on a cap layer or a substrate layer of the sensor and applied to the MEMS device layers through a connection to one or both of those layers. If these forces result in a displacement of the position of certain MEMS layer components (e.g., the proof mass forming a capacitor with the sense electrode), the accuracy and sensitivity of the MEMS inertial sensor can be negatively impacted.

Fig. 2 illustrates an exemplary MEMS inertial sensor 200 according to an embodiment of the disclosure. In an embodiment, MEMS inertial sensor 200 includes cap layer 201, MEMS layer 202, and substrate layer 203. During the manufacturing process of MEMS inertial sensor 200, semiconductor manufacturing techniques may be used to create functional components of each of these layers, such as the suspended spring-mass system of MEMS layer 202, the posts of cap layer 201, and the standoffs, electrodes, and processing circuitry of substrate layer 203. The MEMS layer 202 may be bonded to each of the cap layer 201 and the substrate layer 202, forming a cavity 205.

The functional components of MEMS inertial sensor 200 may be located within cavity 205 and may include, in an exemplary embodiment, anchor mass 204, springs 208 and 212, proof masses 206 and 214, sense electrodes 216 and 218, support posts 220, and standoffs 222. Anchor masses 204, springs 208 and 212, and proof masses 206 and 214 may be formed within MEMS layer 202. In an exemplary embodiment, the anchored mass 204 may be joined to the support of the posts 220 and substrate layer 203 of the cap layer 201 such that the position of the anchored mass 204 is fixed during operation of the MEMS inertial sensor. Springs 208 and 212 may be coupled to anchor mass 204 (coupling not shown in the cross-section of fig. 2), and may also be coupled to proof masses 206 and 214 (coupling not shown in the cross-section of fig. 2). Springs 208 and 212 and proof masses 206 and 214 may be collectively referred to as a suspended spring-mass system, and in the exemplary embodiment of fig. 2, are suspended from anchor mass 204.

While the sense electrodes may be located in various positions (e.g., in-plane, out-of-plane, etc.) for various purposes (sense electrodes, compensation electrodes, drive electrodes, etc.), in the exemplary embodiment of fig. 2, sense electrodes 216 and 218 are located on a surface of substrate layer 203. Sense electrode 216 is positioned adjacent and parallel to proof mass 206 and forms a first capacitor with proof mass 206, while sense electrode 218 is positioned adjacent and parallel to proof mass 214 and forms a second capacitor with proof mass 214. The capacitance of each of the first and second capacitors is based on the distance between the respective sensing electrode and the proof mass. If this distance changes, the absolute value of the measured capacitance may not correspond to the actual inertial force, or the change in measured capacitance may be proportionally smaller (e.g., if the distance between the proof mass and the sense electrode increases, the change in distance due to the inertial force will result in a proportionally smaller change in capacitance) or proportionally larger (e.g., if the distance between the proof mass and the sense electrode decreases, the change in distance due to the inertial force will result in a proportionally larger change in capacitance).

As described herein, MEMS inertial sensor packages can be subjected to various forces due to manufacturing, assembly, and end-use applications. In some embodiments, these forces may be applied on a cap layer or a substrate layer of the sensor (e.g., as cap force 230 and/or substrate force 240) and applied to the MEMS device layers through a connection to one or both of these layers. If these forces cause positional displacement of certain MEMS layer components (e.g., proof masses that form capacitors with the sense electrodes), the accuracy and sensitivity of the MEMS inertial sensor can be negatively impacted.

Fig. 3A illustrates a cross-section of components of an illustrative MEMS sensor with vertically stacked anchors in accordance with some embodiments of the present disclosure, with a top view shown in the cross-sectional view of fig. 4. In the exemplary cross-section depicted in fig. 3A, certain portions of the MEMS sensor (e.g., the joined sidewalls, portions of the suspended spring-mass system, etc.) are omitted for ease of illustration. In the exemplary embodiment depicted in fig. 3A, the MEMS layer includes a first proof mass 304a, a first spring 306a, an anchor mass 310, a second spring 306b, and a second proof mass 304 b. First spring 306a couples first proof mass 304a to anchor mass 310, while second spring 306b couples second proof mass 304b to anchor mass 310. Although not shown in the cross-sectional views of fig. 3A and 3B, in the exemplary embodiment, first proof mass 304a is coupled to second proof mass 304B.

The cap layer 301 is located above the MEMS layer and the substrate layer 302 is located below the MEMS layer. The upper x-y planar surface of the MEMS layer faces the lower x-y planar surface of the cap layer 301 and the lower x-y planar surface of the MEMS layer faces the upper x-y planar surface of the substrate layer 302. Sense electrodes 314 and 316 are located on the upper x-y planar surface of substrate 302. Sense electrode 316 forms a capacitor with proof mass 304a and sense electrode 314 forms a capacitor with proof mass 304 b.

Anchor members 312 (e.g., struts) extend between the cover 301 and the anchor mass 310, forming an engagement surface on a portion of the upper x-y planar surface of the anchor mass 310. Another anchor member 308 (e.g., a standoff) extends between the substrate 302 and the anchor mass 310, forming an engagement surface on a portion of the lower x-y planar surface of the anchor mass 310. In the embodiment of FIG. 3A, support 312 and support 308 are substantially aligned in the x-y plane such that a central axis of support 312 passes through support 308 and a central axis of support 308 passes through support 312. In the exemplary embodiment of fig. 3A, support posts 312 and support 308 may be substantially aligned such that the engagement surface of anchor mass 310 to support posts 312 completely overlaps the engagement surface of anchor mass 310 to support 308. In other embodiments, the overlap of the engagement surfaces may not be complete (e.g., partially offset but mostly overlapping struts and abutments, struts and abutments that overlap at a center point but extend primarily differently (e.g., x-axis and y-axis)), but may be sufficient such that a z-axis force applied to the strut or abutment is experienced by other components as a force perpendicular to the plane of engagement with the anchor mass.

Fig. 3B illustrates a cross-section of components of an example MEMS sensor with vertically stacked anchors experiencing a vertical force according to some embodiments of the present disclosure. As described herein, a MEMS sensor may experience forces on the cover or substrate of the sensor for various reasons, such as during manufacturing, assembly with other components in the final device, or use. In some cases (e.g., due to manufacturing or assembly), these forces may be permanent over the life of the MEMS sensor. In the exemplary embodiment of FIG. 3B, the MEMS sensor of FIG. 3A experiences a negative z-axis force 330 on the cap layer 301.

In the exemplary embodiment of fig. 3B, the force 330 is distributed from the cap layer to the pillars 312 (and to other components, such as sidewalls of the MEMS sensor not depicted in fig. 3A). Because the anchor mass 310 and the support are directly vertically engaged, the same forces distributed to the support posts 312 are also distributed to the anchor mass 310 and the support 308, and through these components to the base plate 308. In some embodiments, force 330 may be sufficient to cause anchor mass 310 (and posts 312 and cover 301) to experience a negative z-direction displacement relative to substrate 302. While this displacement may occur in various ways, in the exemplary embodiment of fig. 3B, the compressive force applied to the support 308 (e.g., due to the force 330 and the counteracting force applied by the substrate 308) may be sufficient to cause physical compression of the support 308. In the embodiment of fig. 3B, the suspended spring-mass system (e.g., proof masses 304a and 304B and springs 306a and 306B) connected to the anchor mass may also experience a negative z-axis displacement of the anchor mass.

In fig. 3A and 3B, the z-axis displacement of the MEMS layer component due to the force 330 is depicted by an initial upper MEMS plane 320, an initial lower MEMS plane 322, a displaced upper MEMS plane 324, and a displaced lower MEMS plane 326. As can be seen from a comparison of these planes, the entire MEMS plane has been displaced in the negative z-direction toward the substrate 302 and the sense electrodes 314 and 316. Due to this displacement, the capacitor of fig. 3B may have a higher capacitance than the capacitor of fig. 3A, regardless of whether the MEMS sensor is sensing the measured external force. In addition, the capacitor of fig. 3B may have higher sensitivity and lower resolution than the capacitor of fig. 3A.

Figure 4 illustrates an exemplary MEMS layer of an out-of-plane sensing MEMS accelerometer with vertically stacked anchors experiencing a vertical compressive force according to some embodiments of the present disclosure. Fig. 4 depicts a particular component in a particular configuration and having particular attributes. Those of ordinary skill in the art will appreciate that fig. 4 may be modified in various ways in light of this disclosure. The component of FIG. 4 is formed within a MEMS device layer and includes two parallel MEMS device planes on opposite sides of the MEMS device layer forming parallel x-y planes. Although not depicted in fig. 4, the substrate layer may be positioned below and parallel to the lower MEMS device plane in the negative z-direction, while the cap layer may be positioned above and parallel to the upper MEMS device plane in the positive z-direction.

In some embodiments, the accelerometer of fig. 4 may include a first sensor portion 401 and a second sensor portion 403, each sensor portion including similar or identical components. The first and second sensor portions are oriented such that centers of masses associated with proof mass 402 (i.e., of first sensor portion 401) and with proof mass 418 (i.e., of second sensor portion 402) cause anti-phase movements in response to linear acceleration along the z-axis.

In an embodiment, first sensor portion 401 includes an anchored mass 410, which anchored mass 410 may be coupled to a cap layer (not depicted) by posts 442 and to a substrate layer (not depicted) by standoffs 440. The struts 442 may be joined to an upper x-y plane of the anchor mass 410 and the standoffs 440 may be joined to a lower x-y plane of the anchor mass 410. In the exemplary embodiment of fig. 4, the area of engagement with the support 442 may completely overlap the area of engagement with the support 440 such that the support 442, the anchored mass 410, and the support 440 are vertically aligned with respect to forces along the z-axis.

A suspended spring-mass system may be suspended from anchor mass 410. Anchor mass 410 may be coupled to proof mass 402 by torsion springs 404 and 416. In the exemplary embodiment of FIG. 4, proof mass 402 may be an asymmetric proof mass. Torsion springs 404 and 416 may be substantially rigid along the x-axis, may allow limited movement along the y-axis, and may have substantial torsional compliance to facilitate rotation of proof mass 402.

In an embodiment, second sensor portion 403 includes an anchored mass 426, which anchored mass 426 can be coupled to a cap layer (not depicted) by posts 452 and to a substrate layer (not depicted) by standoffs 450. The struts 452 can be joined to an upper x-y plane of the anchor mass 426 and the standoffs 450 can be joined to a lower x-y plane of the anchor mass 450. In the exemplary embodiment of fig. 4, the area of engagement with the support 452 can completely overlap the area of engagement with the support 450 such that the support 452, the anchored mass 426, and the support 450 are vertically aligned with respect to forces along the z-axis.

A suspended spring-mass system may be suspended from the anchor mass 426. Anchor mass 426 may be coupled to proof mass 418 by torsion springs 420 and 432. In the exemplary embodiment of FIG. 4, proof mass 418 may be an asymmetric proof mass. Torsion springs 420 and 432 may be substantially rigid along the x-axis, may allow limited movement along the y-axis, and may have substantial torsional compliance to facilitate rotation of proof mass 418.

Linear acceleration in the positive z-direction may cause proof mass 402 to move in the negative z-direction about an axis of rotation and proof mass 418 to move in the negative z-direction about its axis of rotation (e.g., in the embodiment of fig. 4 where torsion springs 404, 416, 420, and 432 are aligned along the x-axis, the axes of rotation of first sensor portion 401 and second sensor portion 403 are the same). The portions of proof mass 402 that are in the positive y-direction relative to torsion springs 404 and 416 may move toward the substrate and any sensing electrodes located under these portions of proof mass 402. Other portions of proof mass 402 may move away from the substrate and any sensing electrodes located under these other portions of proof mass 402. The portions of proof mass 418 that are located in the negative y-direction relative to torsion springs 420 and 432 may move toward the substrate and any sensing electrodes located under these portions of proof mass 418. Other portions of proof mass 418 may move away from the substrate and any sensing electrodes located under these other portions of proof mass 418.

Linear acceleration in the negative z-direction can cause proof mass 402 to move in the positive z-direction about its axis of rotation, and proof mass 418 can move in the positive z-direction about its axis of rotation. The portions of proof mass 402 that are in the positive y-direction relative to torsion springs 404 and 416 may move away from the substrate and any sensing electrodes located under these portions of proof mass 402. Other portions of proof mass 402 may move toward the substrate and any sensing electrodes located under these other portions of proof mass 402. The portions of proof mass 418 that are located in the negative y-direction relative to torsion springs 420 and 432 may move away from the substrate and any sensing electrodes located under these portions of proof mass 418. Other portions of proof mass 418 may move toward the substrate and any sensing electrodes located under these other portions of proof mass 418.

In the exemplary embodiment of fig. 4, a downward force is applied to the cap layer. This force is distributed to the anchor masses 410 and 426 via the struts 442 and 452. As depicted by the "X" in fig. 4, this causes the positions of anchor masses 410 and 426 to shift within the MEMS sensor to move closer to the substrate layer (e.g., based on the compressive force applied to supports 440 and 450). Thus, proof mass 402 is displaced closer to the substrate layers, thereby changing the capacitance of any capacitors formed with the sense electrodes formed on that layer. The suspended spring-mass system of proof mass 418 is suspended from anchor mass 426 and is not suspended from any components that never experience z-axis deflection of anchor mass 426. Thus, proof mass 418 is also displaced closer to the substrate layers, thereby changing the capacitance of any capacitors formed with the sense electrodes formed on that layer.

Fig. 5A illustrates a cross-section of components of an illustrative MEMS sensor with offset anchors in accordance with some embodiments of the present disclosure, wherein a top view is shown in the cross-sectional view of fig. 6. In the exemplary cross-section depicted in fig. 5A, certain portions of the MEMS sensor (e.g., the joined sidewalls, portions of the suspended spring-mass system, etc.) are omitted for ease of illustration. In the exemplary embodiment depicted in fig. 5A, the MEMS layer includes a first proof mass 504a, a first spring 506a, a first anchor mass 510a, a second anchor mass 510b, a second spring 506b, and a second proof mass 504 b. A first spring 506b couples first proof mass 504a to first anchor mass 510a and a second spring 508a couples second proof mass 506a to second anchor mass 510 a. Although not shown in the cross-sectional views of fig. 5A and 5B, in an exemplary embodiment, first proof mass 504a is coupled to second proof mass 504B.

The cap layer 501 is located above the MEMS layer and the substrate layer 502 is located below the MEMS layer. The upper x-y planar surface of the MEMS layer faces the lower x-y planar surface of the cap layer 501 and the lower x-y planar surface of the MEMS layer faces the upper x-y planar surface of the substrate layer 502. Sense electrodes 514 and 516 are located on the upper x-y planar surface of substrate 502. Sense electrode 516 forms a capacitor with proof mass 504a and sense electrode 514 forms a capacitor with proof mass 504 b.

An anchor member 512 (e.g., a strut) extends between the cover 501 and each of the first and second anchor masses 510a, 510 b. Support posts 512 form engagement surfaces on the positive x-side portion of the upper x-y planar surface of anchor mass 510a and engagement surfaces on the negative x-side portion of the upper x-y planar surface of anchor mass 510 b. Additional anchor members 508a and 508b (e.g., standoffs) extend between the substrate 502 and respective anchor masses 510a and 510 b. First pedestal 508a forms an engagement surface on the negative x-side of the lower x-y planar surface of first anchor mass 510 a. Second pedestal 508b forms an engagement surface on the positive x-side of the lower x-y plane of second anchor mass 510 b.

In the embodiment of FIG. 5A, the support posts 512 and the pedestals 508a and 508b are substantially offset in the x-y plane such that the central axis of the support posts 512 does not pass through either the first pedestal 508a or the second pedestal 508 b. The central axis of the first pedestal 508a does not pass through the post 512, and the central axis of the second pedestal 508a does not pass through the post 512.

Fig. 5B illustrates a cross-section of components of an exemplary MEMS sensor with offset anchoring experiencing a perpendicular force according to some embodiments of the present disclosure. As described herein, a MEMS sensor may experience forces on the cover or substrate of the sensor for various reasons, such as during manufacturing, assembly with other components in the final device, or during use. In some cases (e.g., due to manufacturing or assembly), these forces may be permanent over the life of the MEMS sensor. In the exemplary embodiment of FIG. 5B, the MEMS sensor of FIG. 5A experiences a negative z-axis force 530 on the cap layer 501.

In the exemplary embodiment of FIG. 5B, force 530 is distributed from cap layer 501 to posts 512 (and to other components, such as sidewalls of the MEMS sensor not depicted in FIG. 5A). The struts 512 are joined to both the first and second anchor masses 510a, 510b, and therefore the total force applied to each anchor mass is half of the total force applied to the struts 512. First anchor 508a is offset from brace 512 and therefore also from the force applied to first anchor mass 510 a. The first anchor mass 510a rotates about the first pedestal 508a in a clockwise direction toward the base plate 502. The second seat 508b is similarly offset from the stanchion 512 and thus also from the force applied to the second anchor mass 510 b. The second anchor mass 510b rotates about the second seat 508b in a counterclockwise direction toward the substrate.

Clockwise rotation of first anchor mass 510a may also move first spring 506a and proof mass 504a, while counterclockwise rotation of second anchor mass 510b may also move second spring 506b and proof mass 504 b. In an exemplary embodiment, the dimensions and relative positions of posts 512, anchor masses 510a and 510b, and standoffs 508a and 508b may be such that springs 506a and 506b are partially pulled out of plane, while proof masses 504a and 504b experience an upward push that counteracts the effect to remain substantially in the original MEMS plane. The dimensions and relative positions may be configured such that a greater z-axis force resulting in a greater displacement of anchored masses 510a and 510b results in a corresponding greater positive displacement of proof masses 504a and 504 b. Thus, as depicted in fig. 5B, proof mass 504a and proof mass 504B can remain substantially aligned within the MEMS layer (e.g., forming an angle of less than 5% with the original MEMS layer plane) even though upper surface 522 of each of anchor masses 510a and 510B may experience a negative z-direction displacement relative to the original upper surface of MEMS layer 520.

Figure 6 illustrates an exemplary MEMS layer of a MEMS accelerometer with offset anchors experiencing a vertical compressive force according to some embodiments of the present disclosure. Fig. 6 depicts specific components in a specific configuration and having specific characteristics. Those of ordinary skill in the art will appreciate that fig. 6 may be modified in a variety of ways in accordance with the present disclosure. The component of FIG. 6 is formed within a MEMS device layer and includes two parallel MEMS device planes on opposite sides of the MEMS device layer forming parallel x-y planes. Although not depicted in fig. 6, the substrate layer may be positioned below and parallel to the lower MEMS device plane in the negative z-direction, while the cap layer may be positioned above and parallel to the upper MEMS device plane in the positive z-direction.

In some embodiments, the accelerometer of figure 6 may comprise a first sensor portion 601 and a second sensor portion 603, each sensor portion comprising similar or identical components. The first and second sensor portions are oriented such that centers of masses associated with proof mass 602 (i.e., of first sensor portion 601) and with proof mass 618 (i.e., of second sensor portion 603) cause anti-phase movements in response to linear acceleration along the z-axis.

In one embodiment, first sensor portion 601 includes a first anchor mass 610a and a second anchor mass 610 b. Pillars 640 can be coupled to both the cap layer and anchor masses 610a and 610 b. Support posts 640 form engagement surfaces on the positive x-side portion of the upper x-y planar surface of anchor mass 610a and engagement surfaces on the negative x-side portion of the upper x-y planar surface of anchor mass 610 b. The first mount 642a can be coupled to the substrate layer and the anchor mass 610a, and the second mount 642b can be coupled to the substrate layer and the anchor mass 610 b. First abutment 642a forms an engagement surface on the negative x-side of the lower x-y planar surface of first anchor mass 610 a. Second seat 642b forms an engagement surface on the positive x-side of the lower x-y plane of second anchor mass 610 b.

In the embodiment of fig. 6, the post 640 and the pedestals 642a and 642b are substantially offset in the x-y plane such that the central axis of the post 640 does not pass through either of the first pedestal 642a or the second pedestal 642 b. The central axis of the first mount 642a does not pass through the post 640 and the central axis of the second mount 642b does not pass through the post 640. The first pedestal 642a is bonded to only the first anchor mass 610a within the MEMS layer, and the second pedestal 642b is bonded to only the second anchor mass 610b within the MEMS layer. Anchor masses 610a and 610b are discontinuous and are directly coupled only by interengagement to posts 640.

In the exemplary embodiment of fig. 6, the overlap of the engagement surfaces may be partial (e.g., the overlap between the surface associated with strut 640 and the surface associated with each of the brackets 642a and 642b is less than 25%). In additional embodiments, the separation between the engagement surfaces may be greater than the separation depicted in fig. 6.

A suspended spring-mass system may be suspended from anchor masses 610a and 610 b. First anchor mass 610a may be coupled to proof mass 602 by torsion springs 604 and 616. In the exemplary embodiment of FIG. 6, proof mass 602 may be an asymmetric proof mass. Torsion springs 604 and 616 may be substantially rigid with respect to movement in the x-y plane under normal operating conditions and may facilitate rotation about the x-axis about proof mass 602.

In an embodiment, the second sensor portion 603 includes a first anchor mass 626a and a second anchor mass 626 b. The struts 650 may be coupled to both the cap layer and the anchor masses 626a and 626 b. The struts 650 form engagement surfaces on the positive x-side portion of the upper x-y planar surface of anchor mass 626a and engagement surfaces on the negative x-side portion of the upper x-y planar surface of anchor mass 626 b. The first pedestal 652a can be coupled to the substrate layer and the anchor mass 626a, and the second pedestal 652b can be coupled to the substrate layer and the anchor mass 626 b. First pedestal 652a forms an engagement surface on the negative x-side of the lower x-y planar surface of first anchor mass 626 a. Second pedestal 652b forms an engagement surface on the positive x-side of the lower x-y planar surface of second anchor mass 626 b.

In the embodiment of FIG. 6, the support column 650 and the pedestals 652a and 652b are substantially offset in the x-y plane such that the central axis of the support column 650 does not pass through either of the first pedestal 652a or the second pedestal 652 b. The central axis of the first pedestal 652a does not pass through the support column 650, and the central axis of the second pedestal 652b does not pass through the support column 650. The first pedestal 652a is bonded to only the first anchor mass 626a within the MEMS layer, and the second pedestal 652b is bonded to only the second anchor mass 626b within the MEMS layer. The anchor masses 626a and 626b are discontinuous and directly coupled only by interengagement to the struts 650.

In the exemplary embodiment of fig. 6, the overlap of the engagement surfaces may be partial (e.g., the overlap between the surface associated with the strut 650 and the surface associated with each of the standoffs 652a and 652b is less than 25%). In additional embodiments, the separation between the engagement surfaces may be greater than the separation depicted in fig. 6.

A suspended spring-mass system may be suspended from anchor masses 626a and 626 b. First anchor mass 626a may be coupled to proof mass 618 by torsion springs 620 and 632. In the exemplary embodiment of FIG. 6, proof mass 618 may be an asymmetric proof mass. Torsion springs 620 and 632 may be substantially rigid with respect to movement in the x-y plane under normal operating conditions and may facilitate rotation of proof mass 618 about the x-axis.

Linear acceleration in the positive z direction can cause proof mass 602 to rotate about its axis of rotation in the negative RX direction and can cause proof mass 618 to rotate about its axis of rotation in the positive RX direction (e.g., in the embodiment of fig. 6, where torsion springs 604, 616, 620, and 632 are aligned along the x-axis, the axes of rotation of both first sensor portion 601 and second sensor portion 603 are the same). The portions of proof mass 602 that are in the positive y-direction relative to torsion springs 604 and 616 may move toward the substrate and any sensing electrodes located under these portions of proof mass 602. Other portions of proof mass 602 may move away from the substrate and any sensing electrodes located below these other portions of proof mass 602. The portions of proof mass 618 that are in the negative y-direction relative to torsion springs 620 and 632 can move toward the substrate and any sensing electrodes located under these portions of proof mass 618. Other portions of proof mass 618 may be moved away from the substrate and any sensing electrodes located under these other portions of proof mass 618.

Linear acceleration in the negative z-direction can cause proof mass 602 to rotate about its axis of rotation in the positive RX direction, and can cause proof mass 618 to rotate about its axis of rotation in the negative RX direction. The portions of proof mass 602 that are in the positive y-direction relative to torsion springs 604 and 616 may move away from the substrate and any sensing electrodes located under these portions of proof mass 602. Other portions of proof mass 602 may move toward the substrate and any sensing electrodes located below these other portions of proof mass 602. The portions of proof mass 618 that are located in the negative y-direction relative to torsion springs 620 and 632 can move away from the substrate and any sensing electrodes located under these portions of proof mass 618. Other portions of proof mass 618 may be moved toward the substrate and any sensing electrodes located under these other portions of proof mass 618.

In an exemplary embodiment, the sense electrodes can be located on the substrate plane below the sensing mass to perform differential capacitive sensing based on rotation of proof masses 602 and 618 about the axis of rotation.

In an exemplary embodiment, if anchors 610a, 610b, 626a, and 626b are moved toward the substrate, proof masses 602 and 618 may also be moved toward the substrate because proof masses 602 and 618 are coupled to the anchors via torsion springs 604, 616, 620, and 632. If anchors 610a and 626a rotate with a positive RY motion and anchors 610b and 626b rotate with a negative RY motion, then torsion springs 608 and 624 may also rotate with a positive RY and torsion springs 612 and 628 may rotate with a negative RY. Rotation of the combined torsion springs moves proof masses 602 and 618 away from the substrate.

In an embodiment, the alignment between the stanchion and seat anchor is designed to cause the anchor to rotate during a top load force. By designing the stanchion and support to be misaligned, downward movement of the anchor can be counteracted by upward movement of the anchor angle, resulting in a net zero movement of the proof mass and sensing gap during applied forces. Thus, the downward motion of the anchoring system is balanced with the positive motion caused by the rotation of the anchor.

In the exemplary embodiment of fig. 6, a downward force is applied to the cap layer. This force is distributed to the first and second anchor masses 610a, 610b via the support posts 640 and to the first and second anchor masses 626a, 626b via the support posts 650. This moves at least a portion of the anchor masses 610a, 610b, 626a, and 626b closer to the substrate layer, as depicted by an "X" in fig. 6. Because struts 640 and 650 are offset from standoffs 642a, 642b, 652a and 652b, anchored masses 610a, 610b, 626a and 626b also rotate. This rotation is applied at the anchor ends of torsion springs 604, 616, 620, and 632, which causes proof masses 602 and 618 to remain substantially stationary even though all other components in the apparatus have moved at least partially toward the substrate.

Rotation of first and second anchor masses 610a and 610b may cause torsion springs 604, 616 and proof mass 602 to move. In an exemplary embodiment, the dimensions and relative positions of posts 640, anchor masses 610a and 610b, and standoffs 642a and 642b may be such that springs 604 and 616 are partially pulled out of plane, while the suspended spring-mass system experiences an upward push that counteracts the effect to remain substantially in the original MEMS plane. Rotation of first and second anchor masses 626a and 626b may cause torsion springs 620 and 632 and the proof mass to move. In an exemplary embodiment, the dimensions and relative positions of the posts 650, the anchored masses 626a and 626b, and the standoffs 652a and 652b may be such that the springs 620 and 632 are partially pulled out of plane, while the suspended spring-mass system experiences an upward push that counteracts the effect to remain substantially in the original MEMS plane.

The dimensions and relative positions of the struts, anchor masses, and standoffs may be configured such that a greater z-axis force causing a greater displacement of anchor masses 610a and 610b results in a corresponding greater positive displacement of the suspended spring-mass system. In this manner, the suspended spring-mass system can remain substantially statically positioned within the plane of the MEMS device, despite the wide range of z-axis forces exerted on the cap layer and the posts.

The foregoing description includes exemplary embodiments in accordance with the present disclosure. These examples are provided for purposes of illustration only and are not intended to be limiting. It will be understood that the present disclosure may be implemented in a form different from that explicitly described and depicted herein, and that various modifications, optimizations, and variations may be effected by those of ordinary skill in the art, consistent with the claims appended hereto.