Inertial sensor with integrated damping structure

Abstract

An inertial sensor includes a movable mass spaced apart from a surface of a substrate. The movable mass is adapted to move about a rotational axis located between a first end and a second end of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate. The inertial sensor further includes a damping system configured to limit movement of the movable mass in a second direction perpendicular to the first direction. The damping system includes a first damping structure coupled to the movable mass; a second damping structure adjacent to the first damping structure, the first and second damping structures being spaced apart from the surface of the substrate; and a spring structure interconnected between the movable mass and the second damping structure.

Description

Technical Field

[0001] The present invention relates generally to micro-electromechanical systems (MEMS) inertial sensors. More particularly, the present invention relates to inertial sensors with integrated damping structures. Background Art

[0002] Microelectromechanical system (MEMS) sensors are widely used in applications such as automobiles, inertial guidance systems, home appliances, protection systems for various devices, and many other industrial, scientific, and engineering systems. These MEMS sensors sense physical conditions such as acceleration, pressure, angular rotation, or temperature and provide an electrical signal representative of the sensed physical condition.

[0003] Capacitive sensing MEMS inertial sensor designs are highly desirable for operating in both acceleration and angular rotation environments and in miniaturized devices, at least in part due to the relatively low cost of the sensors. Capacitive accelerometers sense changes in capacitance with respect to acceleration to alter the output of an energized circuit. One common form of accelerometer is a dual-layer capacitive sensor with a "teeter-totter" configuration. This commonly used sensor type uses a movable mass or plate that rotates above a substrate under Z-axis acceleration. The accelerometer structure can measure two different capacitances to determine differential capacitance or relative capacitance. Summary of the Invention

[0004] Aspects of the disclosure are defined in the following claims.

[0005] In a first aspect, an inertial sensor is provided, comprising: a substrate; a movable mass spaced apart from a surface of the substrate, the movable mass adapted to move about a rotational axis located between first and second ends of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate; and a damping system configured to limit movement of the movable mass in a second direction perpendicular to the first direction. The damping system comprises: a first damping structure coupled to the movable mass; a second damping structure adjacent to the first damping structure, the first and second damping structures spaced apart from the surface of the substrate; and a spring structure interconnected between the movable mass and the second damping structure.

[0006] In a second aspect, an inertial sensor is provided, comprising: a substrate; a movable mass spaced apart from a surface of the substrate, the movable mass adapted to move about a rotational axis located between a first end and a second end of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate, the movable mass comprising a first portion between the rotational axis and the first end and a second portion between the rotational axis and the second end, wherein the mass of the second portion is greater than the mass of the first portion; and a damping system located in the second portion, the damping system configured to limit movement of the movable mass in a second direction perpendicular to the first direction. The damping system comprises: a plurality of first damping structures coupled to the movable mass; a plurality of second damping structures interleaved with the plurality of first damping structures, the first and second damping structures spaced apart from the surface of the substrate; and a spring structure interconnected between the movable mass and the second damping structure.

[0007] In a third aspect, an inertial sensor is provided, comprising: a substrate; a movable mass block, the movable mass block being spaced apart from a surface of the substrate, the movable mass block being adapted to move around a rotation axis located between a first end and a second end of the movable mass block in response to a first force applied to the movable mass block in a first direction perpendicular to the surface of the substrate, the movable mass block comprising a first portion between the rotation axis and the first end and a second portion between the rotation axis and the second end, wherein the mass of the second portion is greater than the mass of the first portion; and a damping system, the damping system being located in the second portion and being configured to limit the movement of the movable mass block in a second direction perpendicular to the first direction. The damping system includes: a first damping structure, which is connected to the movable mass block; a second damping structure, which is adjacent to the first damping structure, the first and second damping structures are spaced apart from the surface of the substrate; and a spring structure, which is interconnected between the movable mass block and the second damping structure, wherein the first and second damping structures are separated by a gas-containing gap having a predetermined width, the second damping structure is configured to be immovable relative to the first damping structure in response to a second force applied to the movable mass block in the second direction, the first damping structure is configured to move together with the movable mass block in response to the second force, and the width of the gap decreases as the first damping structure moves in the second direction, thereby squeezing the gas in the gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings are used to further illustrate various embodiments and to explain various principles and advantages of the present invention. Like reference numerals refer to identical or functionally similar elements throughout the different views. The drawings are not necessarily drawn to scale and are incorporated into and form a part of this specification together with the detailed description below.

[0009] Figure 1 shows a plan view of a micro-electromechanical system (MEMS) inertial sensor according to an embodiment;

[0010] Figure 2 Show Figure 1 Side view of the inertial sensor;

[0011] Figure 3 Show Figure 1 A plan view of an inertial sensor subjected to a force in a direction perpendicular to a sensing direction of the inertial sensor.

[0012] Figure 4 Show Figure 1 A partial enlarged plan view of the inertial sensor;

[0013] Figure 5 Shows the force in the direction perpendicular to the sensing direction. Figure 4 A magnified partial plan view of the view;

[0014] Figure 6 shows a plan view of an inertial sensor according to another embodiment; and

[0015] Figure 7 A plan view of an inertial sensor according to yet another embodiment is shown. DETAILED DESCRIPTION

[0016] In general, the embodiments disclosed herein require a microelectromechanical system (MEMS) inertial sensor with an integrated damping structure to improve sensitivity and reliability in a small form factor required for various functions. More specifically, a Z-axis seesaw-type inertial sensor includes a damping structure that effectively damps in-plane parasitic modes while having little impact on the area of ​​the movable mass. Although an inertial sensor in the form of an accelerometer is described herein, it should be understood that the damping structure can be adapted for use with other inertial sensors to achieve improved sensitivity and / or reliability.

[0017] This disclosure is provided to further explain at least one embodiment of the present invention in an enabling manner. This disclosure is further provided to enhance understanding and appreciation of the inventive principles and advantages of the present invention and is not intended to limit the present invention in any way. The present invention is defined solely by the appended claims, including any amendments made during the pendency of this application and all equivalents of those claims as issued.

[0018] It should be understood that the use of relational terms such as first and second, top and bottom, etc. (if any) is used solely to distinguish one entity from another entity or one action from another action, and does not necessarily require or imply any actual such relationship or order between such entities or actions. In addition, some figures may be illustrated using various shading and / or hatching to distinguish different elements produced within various structural layers. These different elements within the structural layers may be produced using current and emerging microfabrication technologies such as deposition, patterning, and etching. Thus, although different shading and / or hatching are used in the illustrations, different elements within the structural layers may be formed from the same material.

[0019] refer to Figure 1-2 , Figure 1 shows a plan view of a MEMS inertial sensor 20 according to an embodiment, and Figure 2 A side view of the inertial sensor 20 is shown. The inertial sensor 20, in the form of an accelerometer, is configured as a "seesaw" type inertial sensor. Therefore, the inertial sensor 20 is referred to herein as an accelerometer 20. By convention, the accelerometer 20 is shown as having a generally planar structure in the XY plane, wherein Figure 1 The middle X axis 22 points left and right, Figure 1 The Y axis 24 points up and down, and Figure 1 The Z axis 26 points out of the page (perpendicular to the X axis 22 and the Y axis 24). Figure 2 A three-dimensional coordinate system is presented in the side view illustration of FIG, wherein the X-axis 22 points left and right on the page, the Z-axis 26 points up and down on the page, and the Y-axis 24 points out of the page. In general, the accelerometer 20 is suitable for sensing the accelerometer 20 while damping parasitic motion in the XY plane. Figure 2 Arrow 28 in FIG. 2 represents the Z-axis acceleration.

[0020] The accelerometer 20 includes a substrate 30 having a generally planar surface 32. Electrode elements 34, 36 (see Figure 2) and a suspension anchor 38 are formed on the surface 32 of the substrate 30. The movable mass 40 is spaced apart from the surface 32 of the substrate 30. More specifically, the accelerometer 20 includes suspension springs 42, 44 interconnecting the movable mass 40 and the suspension anchor 38 so that the movable mass 40 is suspended above the substrate 30. The suspension anchor 38 is located approximately in the center of the opening 46 along a rotational axis 48 of the movable mass 40, wherein the rotational axis 48 is located between a first end 50 and a second end 52 of the movable mass 40.

[0021] For consistency throughout the following description of the figures, any structure directly connected to or formed on the surface 32 of the substrate 30, such as the suspension anchor 38, is shown with an "X" through it. Elements suspended above the surface 32 of the substrate 30 are shown with narrow hatching pointing downward and to the right. The spring structure suspended above the surface 32 is generally represented by a solid line.

[0022] The movable mass 40 includes a first portion 54 between the rotation axis 48 and the first end 50 and a second portion 56 between the rotation axis 48 and the second end 52. The movable mass 40 is adapted to rotate about the rotation axis 48 in response to a first force (e.g., Z-axis acceleration 28) applied to the movable mass 40 in a first direction perpendicular to the surface 32 of the substrate 30 (e.g., parallel to the Z-axis 26). When intended for use as a seesaw-type accelerometer, the second portion 56 of the movable mass 40 can be formed to have a relatively greater mass than the first portion 54 of the movable mass 40. Typically, the greater mass of the second portion 56 can be created by offsetting the rotation axis 48 so that the second portion 56 is longer than the first portion 54. In other configurations, this mass difference can be achieved by adding mass to the second portion 56 relative to the first portion 54, removing mass from the first portion 54 relative to the second portion 56, and so on. However, in embodiments, the greater mass of the second portion 56 may be achieved at least in part by adding mass in the form of a damping system formed at the second end 52 of the movable mass 40 and suspended above the surface 32 of the substrate 30 .

[0023] In seesaw-type inertial sensor designs, it is difficult to eliminate parasitic motion in the plane of the movable mass. This parasitic motion may occur in a direction parallel to the Y-axis 24 and / or in a direction parallel to the X-axis 22 and / or as an in-plane pivoting motion about the Z-axis 26. This in-plane parasitic motion is often underdamped due to a high Q factor and a relatively heavy movable mass. The Q factor is a dimensionless parameter that describes the degree to which an oscillator may be underdamped. A higher Q factor indicates a lower rate of energy loss relative to the oscillator's stored energy (that is, the oscillations die out more slowly). Therefore, in the event of an in-plane high-g shock, particularly when the high-g shock is close to the resonant peak of the movable mass, the movable mass may strike the travel stop or stop frame at high speed and with high contact force. Such a high-g shock can damage the movable mass and / or the travel stop or stop frame. Unfortunately, damaging high-g shocks can be difficult to avoid during assembly or in field applications.

[0024] Various approaches have been used to avoid this problem. For example, fixed damping fingers have been implemented to reduce or limit oscillations caused by the effects of high-g shock events. Such damping fingers are coupled to the surface of the substrate and may be located within openings extending through the movable mass. Damping occurs through a squeeze film effect, whereby gas between the fixed damping fingers and the openings in the movable mass is squeezed as the movable mass translates in response to in-plane parasitic motion. In such a configuration, significant damping can be achieved by adding sufficient fixed damping fingers. However, the openings extending through the movable mass consume area of ​​the movable mass. In practice, in response to higher damping requirements, the area consumption of the movable mass can be even greater. As the area of ​​the movable mass decreases, the actual mass or weight of the movable mass decreases accordingly. Consequently, the sensitivity of the inertial sensor may be correspondingly reduced. Alternatively, a larger die size may be required to achieve the desired sensitivity, which is contrary to the goal of minimizing die size.

[0025] Another approach is to tune the parasitic motion to frequencies to which the inertial sensor is unlikely to be exposed. This approach requires a predefined "safe zone" as a design target. However, this approach may not be practical for many inertial sensors because the predefined "safe zone" is difficult to define. In addition, steering parasitic modes can be a challenge to maintain high sensitivity performance. The embodiments described herein require suspended movable damping fingers (instead of the fixed damping fingers discussed above) that significantly improve damping while having little impact on the area of ​​the movable element.

[0026] Therefore, the accelerometer 20 further includes a damping system 58 configured to limit the movement of the movable mass 40 in a direction perpendicular to the Z-axis 26. Figure 1-2 In the example of FIG. 5 , a damping system 58 is configured to limit the movement of the movable mass 40 in response to parasitic forces parallel to the Y-axis 24. The damping system 58 is suspended above the surface 32 of the substrate and is located at the second portion 56 of the movable mass 40. In addition, the damping system 58 causes the second portion 56 to have a greater mass relative to the first portion 54, as will be discussed in greater detail below. The accelerometer 20 further includes at least one travel stop 60 (six shown) coupled to or otherwise formed on the surface 32 of the substrate 30. As will be discussed further below, the damping system 58 is configured to reduce the contact force between the movable mass 40 and the travel stop 60 in response to limiting the movement of the movable mass 40. Although the travel stop 60 is shown as a separate structure, in other embodiments, a single travel stop may be configured as a frame structure surrounding the movable mass 40 and the damping system 58.

[0027] The damping system 58 includes a plurality of first damping structures 62, a plurality of second damping structures 64, and one or more spring structures 66 (two shown) interconnected between the movable mass 40 and the second damping structures 64. Each of the first damping structures 62 and the second damping structures 64 is arranged in a comb-like configuration such that the second damping structures 64 are generally interleaved with the first damping structures 62.

[0028] The first damping structure 62 is coupled to and extends from the second end 52 of the movable mass 40. Additionally, each spring structure 66 includes a first spring end 68 extending from the second end 52 of the movable mass 40. A beam element 70 is spaced apart from the surface 32 of the substrate 30 and laterally displaced from the second end 52 of the movable mass 40. Second spring ends 72 of the spring structures 66 are coupled to the beam element 70. Additionally, the second damping structure 64 is coupled to the beam element 70 and extends from the beam element 70 toward the second end of the movable mass 40. Thus, the spring structures 66, together with the beam element 70, suspend the second damping structure 64 from the movable mass 40 above the surface 32 of the substrate 30.

[0029] Generally, the greater mass of the second portion 56 of the movable mass 40 relative to the first portion 54 of the movable mass 40 is crucial for generating the seesaw motion of the movable mass 40 under Z-axis acceleration 28. The second portion 54 includes two damping structure arrays. One damping structure array, such as the first damping structure 62, is directly connected to the movable mass 40. Simultaneously, the other damping structure array, such as the second damping structure 64, is connected to the movable mass 40 via a spring structure 66. Thus, both the first damping structure 62 and the second damping structure 64 contribute to the mass of the second portion 54 of the movable mass 40 providing a greater torque under Z-axis acceleration 28, and thus providing a higher sensitivity to Z-axis acceleration 28.

[0030] The rotational axis 48 is substantially parallel to the surface 32 of the substrate 30, and in this configuration, the rotational axis 48 is parallel to the Y-axis 24. The beam element 70 has a longitudinal dimension 74 (e.g., length) between first and second beam ends 76, 78 of the beam element 70, wherein the longitudinal dimension 74 is parallel to the rotational axis 48. That is, the beam element 70 is aligned with the Y-axis 24. The accelerometer 20 further includes first and second damping stops 80, 82 coupled to the surface 32 of the substrate and located near corresponding ones of the first and second beam ends 76, 78.

[0031] See now Figure 3 , Figure 3 1 shows a plan view of the inertial sensor 20 when it is subjected to a force in a direction perpendicular to the sensing direction of the inertial sensor 20. In this case, the force may be a high g shock event represented by arrow 84 generally parallel to the Y axis 24. This force is referred to herein as the Y axis acceleration 84, labeled A. Y The Y-axis acceleration 84 is applied to the movable mass 40 in a direction parallel to the Y-axis 24 , thereby causing an in-plane parasitic motion of the movable mass 40 .

[0032] In response to a high-g Y-axis acceleration 84 parallel to the Y-axis 24, the movable mass 40, along with the first and second damping structures 62, 64 of the damping system 58, may collectively undergo in-plane torsional motion (i.e., pivotal motion about the Z-axis 26). For example, a positive Y-axis force 84 causes the Z-axis 26 to rotate, causing the second portion 56 of the movable mass 40, having a greater mass, to translate in an opposite direction, such as the negative Y-direction. The movable mass 40, along with the first and second damping structures 62, 64, moves until one of the first and second beam ends 76, 78 contacts a corresponding one of the damping stops 80, 82. That is, no damping effect occurs until either of the first and second beam ends 76, 78 contacts a corresponding one of the damping stops 80, 82. However, once one of the first and second beam ends 76, 78 contacts a corresponding one of the damping stops 80, 82, the second damping structure 64 becomes immobile relative to the first damping structure 62. That is, the spring structure 66 flexes appropriately so that the first damping structure 62 can continue to move along with the movable mass 40. Thus, the gap between the first and second damping structures 62, 64 becomes smaller. This relative movement enables the squeeze film damping effect to occur.

[0033] Combine Figure 3 refer to Figure 4 and 5 , Figure 4 A partially enlarged plan view of the inertial sensor 20 is shown, and Figure 5 8. FIG. 8 shows an enlarged partial plan view of the inertial sensor 20 when subjected to a Y-axis acceleration 84. The damping system 58 includes a plurality of staggered first and second damping structures 62, 64, each creating a gas-containing gap 86. As best shown in FIG. Figure 4 As seen in FIG, the first and second damping structures 62, 64 are separated by a gas-containing gap 86 having a defined width 88, thereby providing damping. In some embodiments, the gas may be air. However, other suitable gases may be implemented in other embodiments.

[0034] exist Figure 3 and 5 In the example presented in FIG, the movable mass 40 moves together with the first and second damping structures 62, 64 of the damping system 58 until the second beam end 78 of the beam 70 contacts the second damping stop 82. As a result, the second damping structure 64 becomes temporarily stationary while the first damping structure 62 continues to move due to the Y-axis acceleration 84. As best seen in FIG. Figure 5 As seen in FIG, the first damping structure 62 moves relative to the second damping structure 64 causing the width 88 of the gap 86 to decrease. The damping effect occurs when gas present in the gap 86 is squeezed between the first and second damping structures 62, 64 in response to the width 88 of the gap 86 decreasing.

[0035] Due to the parasitic Y-axis acceleration 84, the damping can cause a reduction or limitation of the in-plane parasitic motion of the movable mass 40. That is, the damping effect can limit the movement of the movable mass 40 along the Y-axis 24. However, the damping stops 80, 82 may not be sufficient to completely prevent the in-plane parasitic motion of the movable mass 40. As such, in some embodiments, the accelerometer 20 additionally includes a travel stop 60. The damping that occurs after the second damping structure 64 becomes temporarily stationary can significantly reduce the contact force between the movable mass 40 and the travel stop 60 to correspondingly reduce the risk of the travel stop 60 breaking. Thereafter, after the Y-axis acceleration 84 is eliminated, the restoring force allows the movable mass 40 and the first and second damping structures 62, 64 to return to their nominal positions ( Figure 1 ).

[0036] The damping effect of the damping system 58 depends, among other things, on the number and length of the first and second damping structures 62, 64, which complement each other. Thus, the design of the accelerometer 20 can be tuned to have more damping (e.g., by increasing the number of damping structures 62, 64 and / or by increasing the length of the damping structures 62, 64) or less mass, depending on the specific design requirements.

[0037] Thus, embodiments require a movable suspension damping structure that significantly improves damping of Y-axis acceleration 84 while having little or no impact on the area of ​​a single mass seesaw design, such as movable mass 40. However, this damping approach is not limited to damping in-plane parasitic motion in directions parallel to the Y-axis 24. Additionally, this damping approach can be implemented to improve damping in both the X-direction and the Y-direction ( Figure 6 ) or in the X direction only ( Figure 7 ) damping.

[0038] Figure 6 A plan view of an inertial sensor 90 according to another embodiment is shown. Again, the inertial sensor 90 is configured as a "seesaw" type accelerometer. As such, the accelerometer 90 is adapted to sense the Z-axis acceleration 28, represented by the circled black dot to indicate its direction is out of the page, while the accelerometer 90 damps in-plane parasitic motion along both the X-axis 22 and the Y-axis 24. The accelerometer 90 is similar to the accelerometer 20 ( Figure 1 ). Therefore, common features will use the same reference numerals, and the description of such features will be shortened or omitted for the sake of brevity.

[0039] Accelerometer 90 includes a substrate 30 having a surface 32, electrode elements 34, 36 (not visible), and a suspension anchor 38 formed on surface 32 of substrate 30. A movable mass 40 is spaced from surface 32 of substrate 30 and suspended above substrate 30 via suspension springs 42, 44. Movable mass 40 includes first and second portions 54, 56 and is adapted to rotate about rotational axis 48 in response to Z-axis acceleration 28.

[0040] according to Figure 6 In some embodiments, the accelerometer 90 further includes a damping system 92 configured to limit movement of the movable mass 40 in a direction perpendicular to the Z-axis 26. Specifically, the damping system 92 is configured to limit movement of the movable mass 40 in response to parasitic forces parallel to the Y-axis 24 (e.g., the Y-axis acceleration 84) and in response to parasitic forces parallel to the X-axis 22 (referred to herein as the X-axis acceleration 94). The damping system 92 is located at the second portion 56 of the movable mass 40 and, therefore, contributes to the greater mass of the second portion 56 relative to the first portion 54. In some embodiments, the accelerometer 90 further includes a travel stop 60 coupled to or otherwise formed on the surface 32 of the substrate 30.

[0041] Similar to damping system 58, damping system 92 also includes a plurality of first damping structures 96 coupled to and extending from second end 52 of movable mass 40, and a plurality of second damping structures 98 coupled to and extending from beam element 100 toward second end 52 of movable mass 40. Beam element 100 is also parallel to rotational axis 48 and, therefore, aligned with Y-axis 24. Damping system 92 further includes one or more spring structures 102 (two shown) having a first spring end 104 coupled to second end 52 of movable mass and a second spring end 106 coupled to beam element 100. Along with first and second damping stops 80, 82, accelerometer 90 further includes third and fourth damping stops 108, 110 coupled to surface 32 of substrate 30 and located near a middle region 112 of beam element 100. In some embodiments, the beam element 100 further includes one or more protruding elements 114 , 116 (two shown) extending from the middle region 112 of the beam element 100 and corresponding to the locations of the third and fourth damping stops 108 , 110 .

[0042] Spring structure 102 is suitably configured to flex in-plane in both the X- and Y-directions to achieve a damping effect due to X-axis acceleration 94 and / or Y-axis acceleration 84. Damping in response to Y-axis acceleration 84 has been previously described. Damping in response to X-axis acceleration 94 occurs in a similar manner. For example, as protruding elements 114, 116 of beam element 100 contact third and fourth damping stops 108, 110 in response to X-axis acceleration 94, second damping structure 98 ceases movement, while first damping structure 96 continues to move with movable mass 40. Thus, squeeze film damping becomes effective in the X-direction in response to X-axis acceleration 94.

[0043] Figure 7 FIG2 shows a plan view of an inertial sensor 120 according to yet another embodiment. Again, the inertial sensor 120 is configured as a "seesaw" type accelerometer. As such, the accelerometer 120 is adapted to sense Z-axis acceleration 28, which is represented by the circled black dot to indicate that its direction is out of the page, while the accelerometer 120 damps in-plane parasitic motion along the X-axis 22. The accelerometer 120 is similar to the accelerometer 20 ( Figure 1 ) and accelerometer 90( Figure 6 ). Therefore, common features will use the same reference numerals, and the description of such features will be shortened or omitted for the sake of brevity.

[0044] Accelerometer 90 includes a substrate 30 having a surface 32, electrode elements 34, 36 (not visible), and a suspension anchor 38 formed on surface 32 of substrate 30. A movable mass 40 is spaced from surface 32 of substrate 30 and suspended above the substrate via suspension springs 42, 44. Movable mass 40 includes first and second portions 54, 56 and is adapted to rotate about rotational axis 48 in response to Z-axis acceleration 28.

[0045] according to Figure 7 In some embodiments, the accelerometer 120 further includes a damping system 122 configured to limit movement of the movable mass 40 in a direction parallel to the X-axis 22. Specifically, the damping system 122 is configured to limit movement of the movable mass 40 in response to parasitic forces (e.g., the X-axis acceleration 94) parallel to the X-axis 22. The damping system 122 is located at the second portion 56 of the movable mass 40 and thus contributes to the second portion 56 having a greater mass relative to the first portion 54. Although not shown, in some embodiments, the accelerometer 120 may further include a travel stop coupled to or otherwise formed on the surface 32 of the substrate 30 and proximate the first and second ends 50, 52 of the movable mass 40.

[0046] The damping system 122 includes a plurality of first damping structures 124 coupled to and extending from the second end 52 of the movable mass 40, and a plurality of second damping structures 126 coupled to and extending from one or more beam elements 128, wherein the beam elements 128 are spaced apart from and parallel to the surface 32 of the substrate 30. The second damping structures 126 are interleaved with the first damping structures 124. The damping system 122 further includes one or more spring structures 130 interconnected between the movable mass 40 and the second damping structures 126. The illustrated configuration includes two beam elements 128 and, therefore, two corresponding spring structures 130. However, it should be understood that alternative embodiments may include a single beam element 128 or more than two beam elements 128. According to the illustrated embodiment, each beam element 128 is oriented perpendicular to the rotation axis 48. That is, each beam element 128 is aligned with the X-axis 22.

[0047] A first spring end 132 of the spring structure 130 is coupled to the movable mass 40, and a second spring end 134 of the spring structure 130 is coupled to a first beam end 136 of the beam element 128. The second damping structure 126 is coupled to the beam element 128 and extends perpendicularly therefrom. More specifically, the first and second damping structures 124, 126 are oriented parallel to the rotational axis 48 such that they are aligned with the Y-axis 24. The accelerometer 120 further includes damping stops 138, 140 coupled to the surface 32 of the substrate 30 and located proximate the second beam end 142 of each beam element 128. In some embodiments, the beam element 128 may extend beyond the outer boundaries of the first and second damping structures 124, 126 toward the damping stops 138, 140.

[0048] The spring structure 124 is suitably configured to flex in-plane in the X-direction to achieve a damping effect due to the X-axis acceleration 94. Damping in response to the X-axis acceleration 94 occurs in a similar manner as described above. For example, as the second beam end 142 of the beam element 128 contacts the third and fourth damping stops 138 and 140 in response to the X-axis acceleration 94, the second damping structure 126 stops moving, while the first damping structure 124 continues to move with the movable mass 40. Thus, squeeze film damping becomes effective in the X-direction in response to the X-axis acceleration 94.

[0049] Embodiments disclosed herein require a microelectromechanical system (MEMS) inertial sensor with an integrated damping structure to improve sensitivity and reliability in a compact form factor required for various functions. More specifically, a Z-axis seesaw inertial sensor includes a damping structure that effectively damps in-plane parasitic modes while having little impact on the area of ​​the movable mass. Disclosed are damping structures that can attenuate in-plane parasitic motion along the X-axis, the Y-axis, or both the X-axis and the Y-axis.

[0050] This disclosure is intended to explain how to design and use various embodiments according to the present invention, not to limit the true, intended and fair scope and spirit thereof. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications or variations are possible in light of the above teachings. One or more embodiments are chosen and described in order to provide the best illustration of the principles of the invention and its practical applications, and to enable those skilled in the art to utilize the invention in various embodiments and with various modifications suitable for the particular use contemplated. All such modifications and variations, and all equivalents thereof, are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth of the rights fairly, legally and equitably granted and may be amended during the pendency of this patent application.

Claims

1. An inertial sensor, characterized in that: include: substrate; a movable mass spaced from a surface of the substrate, the movable mass adapted to move about a rotational axis located between a first end and a second end of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate; as well as a damping system configured to limit movement of the movable mass in a second direction perpendicular to the first direction, the damping system comprising: a first damping structure coupled to the movable mass; a second damping structure adjacent to the first damping structure, the first and second damping structures being spaced apart from the surface of the substrate; and a spring structure interconnected between the movable mass and the second damping structure; at least one travel stop coupled to the surface of the base plate proximate the movable mass, and the damping system is configured to reduce a contact force between the movable mass and the at least one travel stop in response to limiting movement of the movable mass in the second direction.

2. The inertial sensor according to claim 1, wherein The movable mass includes a first portion between the rotation axis and the first end and a second portion between the rotation axis and the second end, wherein the mass of the second portion is greater than the mass of the first portion, and the damping system is located in the second portion.

3. The inertial sensor according to claim 2, wherein: The first and second damping structures of the damping system are configured to cause the second portion of the movable mass to have a greater mass relative to the first portion of the movable mass.

4. An inertial sensor, characterized in that: include: substrate; a movable mass spaced from a surface of the substrate, the movable mass adapted to move about a rotational axis located between a first end and a second end of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate; as well as a damping system configured to limit movement of the movable mass in a second direction perpendicular to the first direction, the damping system comprising: a first damping structure coupled to the movable mass; a second damping structure adjacent to the first damping structure, the first and second damping structures being spaced apart from the surface of the substrate; and a spring structure interconnected between the movable mass and the second damping structure; The first damping structure and the second damping structure are separated by a gas-containing gap having a predetermined width, the second damping structure is configured to be immovable relative to the first damping structure in response to a second force applied to the movable mass block in the second direction, the first damping structure is configured to move together with the movable mass block in response to the second force, and the width of the gap decreases as the first damping structure moves in the second direction, thereby squeezing the gas in the gap.

5. The inertial sensor according to claim 4, characterized in that Also includes: a plurality of first damping structures coupled to and extending from the second end of the movable mass, the first damping structure being one of the plurality of first damping structures; A plurality of second damping structures are provided, wherein the plurality of second damping structures are interleaved with the plurality of first damping structures, and the second damping structure is one of the plurality of second damping structures.

6. An inertial sensor, characterized in that: include: substrate; a movable mass spaced from a surface of the substrate, the movable mass adapted to move about a rotational axis located between a first end and a second end of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate; as well as a damping system configured to limit movement of the movable mass in a second direction perpendicular to the first direction, the damping system comprising: a plurality of first damping structures coupled to and extending from the second end of the movable mass, the first damping structure being one of the plurality of first damping structures; a plurality of second damping structures, the plurality of second damping structures being interleaved with the plurality of first damping structures, the second damping structure being one of the plurality of second damping structures; and a spring structure interconnected between the movable mass and the second damping structure; a first spring end of the spring structure coupled to the second end of the movable mass; and a beam element spaced apart from the surface of the substrate, the beam element being displaced from the second end of the movable mass, wherein the second spring end of the spring structure is coupled to the beam element, and the plurality of second damping structures are coupled to the beam element and extend from the beam element toward the second end of the movable mass.

7. The inertial sensor according to claim 6, wherein: The rotation axis is parallel to the surface of the substrate; The beam element has a longitudinal dimension between first and second beam ends of the beam element parallel to the axis of rotation; and The inertial sensor additionally includes first and second damping stops coupled to the surface of the base plate and located proximate corresponding ones of the first and second beam ends.

8. An inertial sensor, characterized in that: include: substrate; a movable mass spaced from a surface of the substrate, the movable mass adapted to move about a rotational axis between a first end and a second end of the movable mass in response to a first force applied to the movable mass in a first direction perpendicular to the surface of the substrate, the movable mass comprising a first portion between the rotational axis and the first end and a second portion between the rotational axis and the second end, wherein a mass of the second portion is greater than a mass of the first portion; and a damping system located in the second portion, the damping system being configured to limit movement of the movable mass in a second direction perpendicular to the first direction, the damping system comprising: a first damping structure coupled to the movable mass; a second damping structure adjacent to the first damping structure, the first and second damping structures being spaced apart from the surface of the substrate; and a spring structure interconnected between the movable mass and the second damping structure, wherein the first damping structure and the second damping structure are separated by a gas-containing gap having a predetermined width, the second damping structure being configured to be immovable relative to the first damping structure in response to a second force applied to the movable mass in the second direction, the first damping structure being configured to move with the movable mass in response to the second force, and the width of the gap decreasing as the first damping structure moves in the second direction, thereby squeezing gas in the gap.

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