Accelerometer

Abstract

The invention provides an accelerometer which comprises a substrate and a cover body, a single-axis accelerometer in the accelerometer comprises fixed comb teeth, a first anchor point and a second anchor point, and the first anchor point is connected with the second anchor point through an elastic beam; the fixed comb teeth are connected to the first anchor point, and the first anchor point is connected to the cover body; the second anchor point is connected to the substrate, and the substrate is provided with a wire used for being electrically connected with the outside so as to be suitable for loading an electric signal on the second anchor point; the other single-axis accelerometer in the accelerometers comprises a first mass block and a spring beam, the first mass block is connected with the spring beam and can turn over around the spring beam, an electrode matched with the first mass block is arranged on the substrate, and the first mass block is connected with the spring beam and can turn over around the spring beam. The first mass blocks and the corresponding electrodes form first detection capacitors located on the two sides of the spring beam, and the mass block, located on one side of the spring beam, of the first mass blocks is larger than the mass block on the other side of the spring beam in area and mass.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor devices, in particular to a kind of accelerometer. BACKGROUND

[0002] MEMS (Micro Electro Mechanical System) inertial sensor is a kind of widely used in smart phone, wearable device, unmanned aerial vehicle, game controller, electric toothbrush, sweeping robot and other consumer electronic products Micro sensor.In MEMS inertial sensor, acceleration sensor is the most typical, most basic and largest quantity sensor in inertial sensor, commonly used in mobile phone, wearable device, toy, small household appliance and other consumer electronics.

[0003] The most mainstream accelerometer is three-axis capacitive accelerometer, which has simple structure, low cost and high sensitivity and linearity.There are mainly two design directions of three-axis shared mass structure and three-axis separate structure in the mainstream market, wherein the required area of three-axis shared mass structure is smaller, which can further reduce cost, but to some extent, due to the shared mass of design end, three axes will inevitably affect each other, causing unstable zero offset and poor stress resistance. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a single-axis accelerometer, which is suitable for X-axis or Y-axis accelerometer, comprising a substrate and a cover, and a fixed comb tooth arranged in a cavity defined by the substrate and the cover;The single-axis accelerometer further comprises a first anchor point (used as a mechanical anchor point) and a second anchor point (used as an electrical anchor point), and the first anchor point and the second anchor point are connected by an elastic beam;The fixed comb tooth is connected to the first anchor point, and the first anchor point is connected to the cover;The second anchor point is connected to the substrate, and the substrate is arranged with a wire for external electrical connection, so as to be suitable for loading electrical signal on the second anchor point.

[0005] Further, the single-axis accelerometer further comprises a movable mass and a third anchor point, the movable mass is movably connected to the third anchor point along the detection direction, and the movable mass comprises a first comb tooth, and the first comb tooth and the fixed comb tooth constitute a detection capacitor.

[0006] Further, the single-axis accelerometer further comprises a damping comb tooth and a fourth anchor point, the damping comb tooth is connected to the fourth anchor point, and the movable mass further comprises a second comb tooth, and the damping comb tooth and the second comb tooth constitute a damping structure.

[0007] Further, the third anchor point and the fourth anchor point are connected by an elastic beam, the third anchor point is connected to the cover, and the fourth anchor point is connected to the substrate, so as to be suitable for loading electrical signal on the fourth anchor point.

[0008] The application further provides another single-axis accelerometer, which is suitable for being used as a Z-axis accelerometer, comprising a substrate, a first mass block and a spring beam, the first mass block is connected with the spring beam and can overturn around the spring beam, the substrate is provided with electrodes matched with the first mass block, the first mass block and the corresponding electrodes form first detection capacitors on both sides of the spring beam, and the first mass block on one side of the spring beam is larger in area and mass than that on the other side.

[0009] Further, the single-axis accelerometer further comprises a second mass block, the substrate is provided with electrodes matched with the second mass block, and the second mass block and the corresponding electrodes form second detection capacitors on both sides of the spring beam.

[0010] Further, the first mass block and the second mass block are respectively provided with matched damping comb teeth, and the two form a damping structure.

[0011] The application further provides a two-axis accelerometer, which comprises two single-axis accelerometers of the first kind and is used for detecting acceleration signals in two directions perpendicular to each other.

[0012] The application further provides another two-axis accelerometer, which comprises one single-axis accelerometer of the first kind and one single-axis accelerometer of the second kind and is used for detecting acceleration signals in two directions perpendicular to each other.

[0013] The application further provides a three-axis accelerometer, which comprises two single-axis accelerometers of the first kind and one single-axis accelerometer of the second kind and is used for detecting acceleration signals in three directions perpendicular to each other.

[0014] The three-axis accelerometer of the application adopts a three-axis separate structure, which is beneficial to reducing mutual interference among the three axes and improving stability; the single-axis accelerometers are provided with comb tooth structures with damping effects, so that the device can resist vibration and impact and the reliability of the device is improved to a certain extent; the Z-axis accelerometer is provided with through holes for reducing air damping, so as to reduce Z-axis noise; the XY-axis accelerometer is provided with two types of anchor points, which are connected to the substrate and the cover respectively, and the Z-axis accelerometer is provided with a compensation electrode, so that the influence of deformation of the substrate on the device can be effectively avoided.

[0015] The concept, specific structure and technical effects of the application will be further described below with reference to the drawings, so as to fully understand the purpose, features and effects of the application. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1is a structural schematic diagram of a top view of a three-axis accelerometer of an embodiment of the present application;

[0017] Figure 2 is Figure 1 is a structural schematic diagram of a side view of an internal structure of a Y-axis accelerometer;

[0018] Figure 3 is Figure 1 is a structural schematic diagram of a side view of an internal structure of a Z-axis accelerometer;

[0019] Figure 4 is Figure 1 is a structural schematic diagram of another side view of an internal structure of a Z-axis accelerometer, wherein the substrate is in a normal state;

[0020] Figure 5 is Figure 4 is a structural schematic diagram of a substrate in a deformed state. DETAILED DESCRIPTION

[0021] In the description of the embodiments of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. The drawings are schematic or conceptual drawings, and the relationship between the thickness and width of each part, as well as the proportional relationship between each part, etc. are not exactly the same as the actual values.

[0022] Figure 1 A structural schematic diagram of a three-axis accelerometer of an embodiment of the present application is shown, which adopts a three-axis separation design, including a Y-axis accelerometer located in the upper right, an X-axis accelerometer located in the upper left, and a Z-axis accelerometer located in the lower part. As shown in Figures 2 to 5 , Figure 1 The structure in the above is arranged in a cavity defined by the substrate D2 and the cover D1, which can protect the internal structure, and the cavity is arranged to a predetermined air pressure, such as 0.1-1 standard atmosphere, which can be set according to the actual needs of the device, and is not limited here. The substrate D2 is provided with a wire (such as a metal wire) connected to the corresponding structure in the above cavity, to realize electrical connection with the corresponding structure.

[0023] In the Y-axis accelerometer, the movable mass M2 is connected to the anchor A29 through the spring beams S3 and S4, so that the movable mass M2 is adapted to move along the Y-axis direction. The comb electrodes E21, E22, E23 and E24 are connected to the anchors A22, A23, A26 and A27 respectively, and the anchors A21, A24, A25 and A28 are connected to the anchors A22, A23, A26 and A27 through the elastic beams C21, C24, C23 and C26 respectively. The anchors A210 and A211 are connected to the anchor A29 through the elastic beams C22 and C25 respectively, and the other sides of the anchors A210 and A211 are connected to the damping combs B21 and B22 respectively.

[0024] According to the design concept of the present application, the above anchors are divided into two categories, one is a mechanical anchor, which is used to connect or fix the comb structure, and the other is an electrical anchor, which is used to connect the wires on the substrate D2, and can also be used to connect or fix the comb structure, thereby providing electrical signals for the corresponding structure. Referring to Figure 1 and Figure 2 In the above anchors, the anchors A22, A23, A26, A27 and A29 are mechanical anchors, which are arranged to be connected to the cover D1, and the anchors A21, A24, A25, A28, A210 and A211 are electrical anchors, which are arranged to be connected to the substrate D2, thereby being adapted to load electrical signals on these anchors. The separate arrangement of the two types of anchors can effectively resist the influence of the deformation of the substrate D2 due to the stress gradient or temperature gradient on the device. When the substrate D2 deforms, since the mechanical anchors are connected to the cover D1, the influence of the deformation of the substrate D2 on the detection capacitance related structure can be avoided or minimized, and the mechanical anchors and the electrical anchors are connected through the elastic beams, so that when the electrical anchors change position due to the deformation of the substrate D2, the displacement of the electrical anchors can be buffered and offset by the elastic beams, thereby avoiding affecting the mechanical anchors.

[0025] The movable mass M2 is provided with comb electrodes that cooperate with the comb electrodes E21, E22, E23 and E24 respectively, thereby forming detection capacitances for Y-axis acceleration detection. Specifically, the movable mass M2 and the comb electrodes E21 and E24 together form a Y-axis detection capacitance C_Y1, and the movable mass M2 and the comb electrodes E22 and E23 together form a Y-axis detection capacitance C_Y2. The anchors A210 and A211 provide electrical signals for the movable mass M2, and the anchors A21, A24, A25 and A28 provide electrical signals for the comb electrodes E21, E22, E23 and E24 respectively.

[0026] When the accelerometer in this embodiment applies acceleration in the positive Y-axis direction, the movable mass M2 deforms under the applied acceleration, causing the spring beams S3 and S4 to move along the positive Y-axis. At this time, the distance between the comb teeth of the Y-axis sensing capacitor C_Y1 decreases, thus increasing the capacitance value of C_Y1. Simultaneously, the distance between the comb teeth of the Y-axis sensing capacitor C_Y2 increases, thus decreasing the capacitance value of C_Y2. The final output capacitance change is a differential result, ΔC_Y1 - ΔC_Y2. Since ΔC_Y1 is positive and ΔC_Y2 is negative, the final output is |ΔC_Y1| + |ΔC_Y2|.

[0027] The movable mass M2 is also equipped with damping combs that respectively cooperate with damping combs B21 and B22, thus forming a damping structure. Since the potentials on the movable mass M2 and the damping combs B21 and B22 are limited by the electrical signals loaded on the anchor points A210 and A211, which serve as electrical anchor points, the movable mass M2 and the damping combs B21 and B22 are at the same potential. That is, there is no electric field force between the damping combs of the damping structure. At the same time, the cavity in which it is located is at constant pressure, so air damping can be formed between the cooperating damping combs. This damping structure can enhance the damping effect of the movable mass M2 during movement. When subjected to impact, the damping structure can provide greater damping, which can slow down the movement of the movable mass M2 along the Y direction, reduce the collision risk of related structures, and improve reliability, vibration resistance, and impact resistance.

[0028] In the X-axis accelerometer, the movable mass M1 is connected to anchor point A19 via spring beams S1 and S2, thus allowing the movable mass M1 to move along the X-axis. Comb electrodes E11, E12, E13, and E14 are connected to anchor points A12, A13, A16, and A17, respectively. Anchor points A11, A14, A15, and A18 are connected to anchor points A12, A13, A16, and A17 via elastic beams C11, C12, C13, and C14, respectively. Anchor points A110 and A111 are connected to anchor point A19 via elastic beams C15 and C16, respectively. Simultaneously, damping comb teeth B11 and B12 are connected to the other side of anchor points A110 and A111, respectively.

[0029] As previously described, according to the design concept of the present invention, the anchor points are divided into two categories: mechanical anchor points and electrical anchor points. Among these anchor points, anchor points A12, A13, A16, A17, and A19 are mechanical anchor points, connected to the cover D1; anchor points A11, A14, A15, A18, A110, and A111 are electrical anchor points, connected to the substrate D2, thus suitable for loading electrical signals onto these anchor points. The arrangement of these two types of anchor points effectively resists the influence of deformation on the substrate D2 caused by stress or temperature gradients on the device. When the substrate D2 deforms, the mechanical anchor points connected to the cover D1 avoid or minimize the impact of the substrate D2 deformation on the sensing capacitor-related structure. Simultaneously, the mechanical and electrical anchor points are connected by an elastic beam, so that when the position of the electrical anchor points changes due to the deformation of the substrate D2, the elastic beam buffers and offsets the displacement of the electrical anchor points, thereby avoiding any impact on the mechanical anchor points.

[0030] The movable mass M1 is equipped with comb electrodes that respectively cooperate with comb electrodes E11, E12, E13, and E14, thus forming a detection capacitor for X-axis acceleration detection. Specifically, the movable mass M1 and comb electrodes E12 and E13 together form the X-axis detection capacitor C_X1, and the movable mass M1 and comb electrodes E11 and E14 together form the X-axis detection capacitor C_X2. Anchor points A110 and A111 provide electrical signals to the movable mass M1, and anchor points A11, A14, A15, and A18 provide electrical signals to the comb electrodes E11, E12, E13, and E14, respectively.

[0031] When the accelerometer in this embodiment applies acceleration in the positive X-axis direction, the movable mass M1 deforms under the applied acceleration, causing the spring beams S1 and S2 to move along the positive X-axis. At this time, the distance between the teeth of the X-axis sensing capacitor C_X1 decreases, thus increasing the capacitance value of C_X1. Simultaneously, the distance between the teeth of the X-axis sensing capacitor C_X2 increases, thus decreasing the capacitance value of C_X2. The final output capacitance change is a differential result, ΔC_X1 - ΔC_X2. Since ΔC_X1 is positive and ΔC_X2 is negative, the final output is |ΔC_X1| + |ΔC_X2|.

[0032] The movable mass M1 is also provided with damping combs that respectively cooperate with damping combs B11 and B12, thus forming a damping structure. Similar to the damping structure in the Y-axis accelerometer mentioned above, the cooperating damping combs can form air damping. This damping structure can enhance the damping effect of the movable mass M1 during movement. When subjected to impact, the damping structure can provide greater damping, which can slow down the movement of the movable mass M1 along the X direction, reduce the collision risk of related structures, and improve reliability, vibration resistance, and impact resistance.

[0033] In the Z-axis accelerometer, the movable mass M3 is connected to anchor points A31 and A32 via spring beams S5 and S6 and structural beams C31 and C32, thus allowing the movable mass M3 to rotate about the axis defined by spring beams S5 and S6. The two mass blocks on either side of the movable mass M3 located on spring beams S5 and S6 have an asymmetrical structure, with one side having a larger area and mass than the other. This side of the mass block has a through-hole array B33. The through-hole array B33 is designed to reduce the air resistance on the side with the larger area and mass when the movable mass M3 moves along the Z-axis. In other words, during movement, the air in the cavity passes through the through-hole array B33, thereby reducing the air resistance on the movable mass M3.

[0034] Mass blocks M4 and M5 are connected to anchor points A31 and A32 via structural beams C31 and C32, respectively. Simultaneously, damping comb teeth B31 and B32 are connected to both sides of mass blocks M4 and M5. Specifically, half of the comb teeth in damping comb tooth B31 are connected to mass block M4, and the other half to mass block M5. Similarly, half of the comb teeth in damping comb tooth B32 are connected to mass block M4, and the other half to mass block M5.

[0035] The substrate D2 is provided with bottom electrodes E31, E32, E33, E34 and compensation electrodes E35, E36, which together with the movable mass block M3 form capacitors C_E31, C_E32, C_E33, C_E34, C_E35, C_E36, respectively, to form a detection capacitor for Z-axis acceleration detection. Specifically, the movable mass block M3, the bottom electrodes E32, E34 and the compensation electrode E35 together form the Z-axis detection capacitor C_Z1, that is, C_Z1 = C_E32 + C_E34 + C_E35. The movable mass block M3, the bottom electrodes E31, E33 and the compensation electrode E36 together form the Z-axis detection capacitor C_Z2, that is, C_Z2 = C_E31 + C_E33 + C_E36.

[0036] In this embodiment, the bottom electrodes E31, E32, E33, and E34 have the same area, and the bottom electrodes E31 and E32, E33 and E34, and compensation electrodes E35 and E36 are all symmetrically arranged along the axis defined by the spring beams S5 and S6. The sum of the areas of the compensation electrodes E35 and E36 is equal to the sum of the areas of the bottom electrodes E31, E32, E33, and E34, that is, S_E35=S_E36=2×S_E31=2×S_E32=2×S_E33=2×S_E34.

[0037] When the accelerometer in this embodiment is loaded with acceleration in the positive Z-axis direction, the movable mass block M3 undergoes torsional deformation of the spring beams S5 and S6 under the loading of acceleration. Since the mass blocks above the bottom electrodes E32 and E34 are larger, they move closer to the substrate D2. This means that the capacitance values ​​of capacitors C_E32 and C_E34 increase, while the capacitance values ​​of capacitors C_E31 and C_E33 decrease. The mass blocks M4 and M5 above the compensation electrodes E35 and E36 are firmly connected to the anchor points A31 and A32 and will not be displaced. Therefore, ΔC_E35 = ΔC_E36 = 0. So the total differential capacitance change Δf is as follows:

[0038] Δf=ΔC_Z1-ΔC_Z2

[0039] =(ΔC_E32+ΔC_E35+ΔC_E34)-(ΔC_E31+ΔC_E36+ΔC_E33)=(ΔC_E32-ΔC_E31)+(ΔC_E34-ΔC_E33)=|ΔC_E32|+|ΔC_E31|+|ΔC_E34|+|ΔC_E33|.

[0040] When the accelerometer is referenced, the substrate D2 deforms due to stress or temperature gradients on the substrate D2. Figure 4 and Figure 5 The figures show the normal state and the deformed state of substrate D2, respectively. At this time, the compensation electrodes E35 and E36 can compensate the detection capacitance of Z-axis acceleration detection to overcome the influence of deformation.

[0041] by Figure 5 Taking the deformation state of substrate D2 as an example, the bottom electrodes E31 and E32 on substrate D2 undergo displacement along the Z-axis. Specifically, the distance between bottom electrode E31 and movable mass block M3 decreases compared to normal, resulting in ΔC_E31 > 0, while the distance between bottom electrode E32 and movable mass block M3 increases compared to normal, resulting in ΔC_E32 < 0. Similarly, this results in ΔC_E35 > 0, ΔC_E33 > 0, and ΔC_E36 < 0, ΔC_E34 < 0. Given that each electrode is within a very limited area, the deformation of substrate D2 can be considered as follows:Figure 5 As shown, the relationship is linear, therefore the capacitance values ​​of the above capacitors change by essentially the same amount.

[0042] Based on the area relationship between the compensation electrode and the bottom electrode, i.e.

[0043] S_E35=S_E36=2×S_E31=2×S_E32=2×S_E33=2×S_E34,

[0044] It can be known

[0045] |ΔC_E35|=|ΔC_E36|=2×|ΔC_E31|=2×|ΔC_E32|=2×|ΔC_E33|=2×|ΔC_E34|.

[0046] At this point, the total output differential capacitance changes as follows:

[0047] Δf=ΔC_Z1-ΔC_Z2

[0048] =(ΔC_E32+ΔC_E35+ΔC_E34)-(ΔC_E31+ΔC_E36+ΔC_E33)=0-0

[0049] =0.

[0050] As can be seen from the above, the design of the compensation electrodes E35 and E36 in the Z-axis accelerometer can basically offset, or at least partially offset, the effect of the deformation on the substrate D2 caused by stress gradient or temperature gradient on the device.

[0051] The movable mass M3 is also provided with damping combs that respectively cooperate with damping combs B31 and B32, thus forming a damping structure. Similar to the damping structure in the X-axis and Y-axis accelerometers mentioned above, the cooperating damping combs can form air damping. This damping structure can enhance the damping effect of the movable mass M3 during movement. When subjected to impact, the damping structure can provide greater damping, which can slow down the movement and torsion of the movable mass M3 along the Y direction, reduce the collision risk of related structures, and improve reliability, vibration resistance, and impact resistance.

[0052] The triaxial accelerometer in this embodiment adopts a three-axis separate design of X-axis, Y-axis and Z-axis, which is easy to understand. An accelerometer of any one of the three axes can be used to form a single-axis accelerometer product, or an accelerometer of any two of the three axes can be used to form a two-axis accelerometer product.

[0053] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A single-axis accelerometer, comprising a substrate and a cover, and fixed comb teeth disposed within a cavity defined by the substrate and the cover, characterized in that, It also includes a first anchor point and a second anchor point, the first anchor point and the second anchor point being connected by an elastic beam; the fixed comb teeth are connected to the first anchor point, the first anchor point being connected to the cover body; the second anchor point is connected to the substrate, the substrate being provided with wires for external electrical connection, thereby adapting to load electrical signals on the second anchor point.

2. The single-axis accelerometer as described in claim 1, characterized in that, It also includes a movable mass block and a third anchor point. The movable mass block is movably connected to the third anchor point along the detection direction. The movable mass block includes a first comb tooth, which, together with the fixed comb tooth, constitutes a detection capacitor.

3. The single-axis accelerometer as described in claim 2, characterized in that, It also includes damping comb teeth and a fourth anchor point, the damping comb teeth being connected to the fourth anchor point, and the movable mass block also includes a second comb tooth, the damping comb teeth and the second comb tooth forming a damping structure.

4. The single-axis accelerometer as described in claim 3, characterized in that, The third anchor point and the fourth anchor point are connected by an elastic beam. The third anchor point is connected to the cover, and the fourth anchor point is connected to the substrate, thereby adapting for loading an electrical signal on the fourth anchor point.

5. A single-axis accelerometer, comprising a substrate, a first mass block, and a spring beam, wherein the first mass block is connected to the spring beam and is capable of rotating around the spring beam, and electrodes cooperating with the first mass block are disposed on the substrate, the first mass block and the corresponding electrodes forming a first detection capacitor located on both sides of the spring beam, characterized in that, The mass block located on one side of the spring beam has a larger area and mass than the mass block on the other side.

6. The single-axis accelerometer as described in claim 5, characterized in that, It also includes a second mass block, and an electrode that cooperates with the second mass block is disposed on the substrate. The second mass block and the corresponding electrode constitute a second detection capacitor located on both sides of the spring beam.

7. The single-axis accelerometer as described in claim 6, characterized in that, The first mass block and the second mass block are respectively provided with matching damping comb teeth, which together constitute a damping structure.

8. A biaxial accelerometer, characterized in that, It includes two single-axis accelerometers as described in any one of claims 1 to 4, which are used to detect acceleration signals in two mutually perpendicular directions.

9. A biaxial accelerometer, characterized in that, It includes one single-axis accelerometer as described in any one of claims 1 to 4 and one single-axis accelerometer as described in any one of claims 5 to 7, respectively used to detect acceleration signals in two mutually perpendicular directions.

10. A triaxial accelerometer, characterized in that, It includes two single-axis accelerometers as described in any one of claims 1 to 4 and one single-axis accelerometer as described in any one of claims 5 to 7, respectively used to detect acceleration signals in three mutually perpendicular directions.

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