MEMS capacitive acceleration sensor sensitive structure and sensor with stress isolation

Abstract

The present invention relates to the field of micro-electromechanical system manufacturing technology, in particular to a MEMS capacitive acceleration sensor sensitive structure and sensor with stress isolation, comprising a sensitive mass block frame, movable electrode comb teeth, non-movable electrode comb teeth, a U-shaped sensitive beam, a stress isolation structure and a stop structure. When the system is subjected to changes in ambient temperature, the generated thermal stress is released through the stress transfer beam and the stress concentration beam, so that the stress is isolated outside the sensitive U-shaped sensitive elastic beam, thereby avoiding affecting the sensor scale factor and ensuring the temperature consistency of its performance; at the same time, by setting the stress concentration beam and the stress transfer beam connected to the isolation anchor point, support for the far end of the sensitive mass block frame is achieved, which can improve the modal separation ratio, reduce the cross-axis sensitivity, improve the overload resistance and stability, and avoid being affected by the acceleration in the non-sensitive axis direction. The problem of low detection accuracy, poor stability and incomplete stress release of the existing sensitive chip in the sensitive axis direction is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems (MEMS) manufacturing, and in particular to a MEMS capacitive acceleration sensor sensitive structure with stress isolation and a sensor. Background Art

[0002] Acceleration measurement technology is of great significance in fields such as scientific research and consumer electronics. It is a core technology for important applications such as inertial navigation, geological exploration, earthquake monitoring, fault diagnosis, and attitude capture. It has also spawned a wide range of products tailored to meet diverse needs. With the continuous advancement of semiconductor processing and manufacturing technology, microelectromechanical systems (MEMS) devices have emerged. With their advantages of high precision, low power consumption, compact size, and low cost, they are now used in many fields, particularly in the transportation and aerospace industries. MEMS accelerometers are becoming increasingly intelligent and integrated, gradually replacing traditional accelerometers.

[0003] There are three main acceleration detection schemes for MEMS capacitive accelerometers: comb-tooth capacitive accelerometers, seesaw capacitive accelerometers, and sandwich capacitive accelerometers.

[0004] Among them, the comb-tooth capacitive accelerometer is one of the most intensively researched and widely used MEMS accelerometers. The detection principle of a comb-tooth capacitive accelerometer is as follows: when subjected to acceleration in the sensitive direction, the sensitive mass drives the movable electrode comb teeth to move, causing displacement. This causes a change in the gap or facing area between the movable and fixed electrode comb teeth, resulting in a change in capacitance. A CV converter converts the capacitance change signal into a voltage change signal. A proportional-integral-derivative (PID) control system then adjusts the DC voltage fed back to the capacitive comb teeth to maintain the sensitive mass in a constant equilibrium position. The feedback voltage from the PID control system reflects the magnitude of the input acceleration. Comb-tooth capacitive accelerometers are typically manufactured through a multi-layer bonding process, including substrate and structural layers. These layers involve various materials, such as glass, silicon, and gold. The varying thermal expansion coefficients between these materials lead to thermal stress within the structure. This thermal stress causes changes in the sensitive elastic beam, affecting the comb-tooth capacitive accelerometer's scale factor and reducing the temperature consistency of sensor performance.

[0005] The existing technology for reducing the stress of the sensitive chip of the comb-tooth capacitive acceleration sensor is usually to design a stress isolation structure. The specific method is to arrange the mass block anchor point at the center of the chip structure and dissipate the stress through the stress isolation frame. For example, the "mouth"-shaped stress isolation frame disclosed in the Chinese invention patent with the authorization publication number CN113138292B and the "king"-shaped stress isolation frame disclosed in the Chinese invention patent with the publication number CN115407084A. Although the above technical solutions can reduce the thermal stress generated inside the structure due to the different thermal expansion coefficients between materials, because its anchor point is set in the middle and the stress isolation frame surrounds almost the entire comb-tooth capacitive acceleration sensor sensitive chip, there is no anchor point for fixing the far end of the chip in the sensitive axis direction. In addition, the sensitive elastic beam is also set at the far end of the chip in the sensitive axis direction, resulting in the sensitive structure being prone to complex modes and a small modal separation ratio, which affects the detection accuracy in the sensitive axis direction. In addition, the cross-axis sensitivity is high and it is easily affected by the acceleration in the non-sensitive axis direction.

[0006] A Chinese invention patent with the authorization publication number CN115078767B discloses a MEMS accelerometer sensor sensitive structure that uses a four-sided stress release structure. Although this structure ensures the overall modal state of the comb-tooth capacitive accelerometer sensitive structure, the stress and deformation generated by thermal expansion at the anchor points set at the edges of the chip are the greatest, and the stress release is not thorough enough, resulting in a less effective effect than when the anchor points are set in the center. Summary of the Invention

[0007] In response to the problems in the prior art of the comb-tooth capacitive acceleration sensor's sensitive chip having complex modes and a small modal separation ratio, which result in low accuracy in sensitive axis direction detection, poor stability, and incomplete stress release, the present invention provides a MEMS capacitive acceleration sensor sensitive structure and sensor with stress isolation.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a MEMS capacitive acceleration sensor sensitive structure with stress isolation. A rectangular coordinate system is established with the center point of the acceleration sensor sensitive structure as the origin, the horizontal axis as the X-axis, and the vertical axis as the Y-axis. The acceleration sensor sensitive structure is symmetrical about the Y-axis along the horizontal axis and about the X-axis along the vertical axis, and includes a plurality of sensitive mass block frames, a plurality of detection comb connection structures, and a plurality of stress isolation structures, provided on a substrate.

[0010] The detection comb tooth connection structure is fixed on the substrate through a single detection comb tooth anchor point, and a plurality of non-movable electrode comb teeth are arranged on both sides of the detection comb tooth connection structure along the Y-axis direction;

[0011] The sensitive mass frames are symmetrically arranged along the Y-axis and move along the sensitive axis. Two groups of sensitive mass frames near the Y-axis are connected to each other, and the remaining adjacent sensitive mass frames are connected by a U-shaped connection structure. A stop structure is fixed on the substrate within the U-shaped connection structure through a stress isolation anchor point, and the U-shaped connection structure is connected to a U-shaped elastic sensitive beam. A plurality of movable electrode comb teeth are provided on the sensitive mass frame, and the movable electrode comb teeth correspond one-to-one with the non-movable electrode comb teeth to form a capacitor structure.

[0012] The stress isolation structure includes a stress transfer beam connected to a U-shaped elastic sensitive beam, wherein the stress transfer beam is arranged along the Y-axis direction and fixed to the substrate through a central anchor point; two stress concentration beams extending along the X-axis are respectively provided at the two ends of the stress transfer beam, and the stress concentration beams are connected to a stop structure.

[0013] Furthermore, the width of the U-shaped connection structure is ≥150 μm.

[0014] Furthermore, the detection comb anchor points are symmetrically arranged with the X-axis as the symmetry axis.

[0015] Furthermore, the stress concentration beam has a length along the X-axis direction of ≥50 μm and a width of ≤15 μm.

[0016] Furthermore, the aspect ratios of the movable electrode comb teeth and the non-movable electrode comb teeth are both ≤30.

[0017] Furthermore, the sizes of the detection comb anchor points and the center anchor point are both ≥100*100 μm and ≤300*300 μm.

[0018] Furthermore, the stop structure includes a plurality of rectangular protrusions arranged in sequence along the X direction, and the distance between the rectangular protrusions and the U-shaped connecting structure is less than 2 / 3 of the gap between the plates of the capacitor structure.

[0019] Furthermore, the width of the stress transfer beam is ≥200 μm.

[0020] Furthermore, the stiffness of the stress concentration beam is ≥20 times the stiffness of the U-shaped elastic sensitive beam.

[0021] A sensor comprises the above-mentioned MEMS capacitive acceleration sensor sensitive structure with stress isolation.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a MEMS capacitive acceleration sensor sensitive structure with stress isolation. A rectangular coordinate system is established with the center point of the acceleration sensor sensitive structure as the origin, the horizontal axis as the X-axis, and the vertical axis as the Y-axis. The acceleration sensor sensitive structure is symmetrical about the Y-axis along the horizontal axis and about the X-axis along the vertical axis. It includes a sensitive mass frame, movable electrode comb teeth, non-movable electrode comb teeth, a U-shaped sensitive beam, a stress isolation structure, and a stop structure. By setting the stress transfer beam and stress concentration beam of the stress isolation structure, when the acceleration sensor is affected by ambient temperature changes and its size expands due to heat or contracts due to cold, the thermal stress generated by the different thermal expansion coefficients between the substrate layer and the structural layer is released through the stress transfer beam and the stress concentration beam. The stress is isolated outside the sensitive U-shaped elastic sensitive beam, thereby avoiding affecting the scale factor of the comb-tooth capacitive acceleration sensor and ensuring the temperature consistency of the sensor performance. At the same time, a stress isolation anchor point is provided at the far end in the sensitive axis direction. By setting the stress concentration beam and stress transfer beam connected to it, support is achieved for the far end of the sensitive mass block frame, thereby improving the modal separation ratio, reducing the cross-axis sensitivity, and improving the out-of-plane overload resistance and stability of the acceleration sensor, thereby avoiding the influence of acceleration in the non-sensitive axis direction.

[0024] It is characterized in that the width of the U-shaped connection structure is ≥150μm, which can effectively reduce the modal complexity of the sensitive structure of the acceleration sensor, is easy to design, and further improves its stability.

[0025] The detection comb anchor points are symmetrically arranged with the X-axis as the symmetry axis, which can further improve the balance of the structure and ensure the accuracy of the measurement.

[0026] The length of the stress concentration beam along the X-axis direction is ≥50μm and the width is ≤15μm, which can prevent the stress concentration beam from breaking due to high stress in a high temperature environment during wafer bonding. After the break, the sensitive mass block is supported by the central anchor point, the vibration mode changes, and the acceleration sensor may not work properly.

[0027] The aspect ratios of the movable electrode comb teeth and the non-movable electrode comb teeth are both ≤30, which avoids additional displacement of the ends of the electrode comb teeth when subjected to acceleration, thereby ensuring the output linearity of the acceleration sensor.

[0028] The sizes of the detection comb anchor point, stress isolation anchor point and central anchor point are all ≥100*100μm and ≤300*300μm, which ensures effective anchoring while avoiding excessive size that increases stress inside the sensitive structure of the acceleration sensor and reduces output stability.

[0029] The stop structure includes a plurality of rectangular protrusions arranged in sequence along the X direction. The distance between the rectangular protrusions and the U-shaped connection structure is less than 2 / 3 of the gap between the plates of the capacitor structure. The stop structure can effectively resist overload and at the same time avoid the complexity of the acceleration sensor mode and the difficulty of design.

[0030] The width of the stress transfer beam is ≥200 μm to ensure that the stress transfer beam does not suffer from complex deformations such as transverse deformation along the X-axis.

[0031] The stiffness of the stress concentration beam is ≥20 times that of the U-shaped elastic sensitive beam, so as to avoid the stiffness of the stress concentration beam being close to the stiffness of the spring mass system and being seriously affected by temperature.

[0032] The present invention provides a sensor comprising the above-mentioned stress-isolated MEMS capacitive acceleration sensor sensitive structure. The sensor has the characteristics of high measurement accuracy, good stability, strong overload resistance, etc., and has better practical value and economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a schematic diagram of a sensitive structure of a MEMS capacitive acceleration sensor with stress isolation according to the present invention.

[0034] Figure 2 This is a partially enlarged schematic diagram of the stress isolation structure of a MEMS capacitive acceleration sensor sensitive structure with stress isolation of the present invention.

[0035] Among them, 1-U-shaped elastic sensitive beam, 2-sensitive mass block frame, 3-U-shaped connection structure, 4-detection comb tooth anchor point, 5-detection comb tooth connection structure, 6-center anchor point, 7-stress concentration beam, 8-stress isolation anchor point, 9-stress transfer beam, 10-stop structure, 11-non-movable electrode comb teeth, 12-movable electrode comb teeth. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0039] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0041] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0042] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0043] Example 1

[0044] The present invention discloses a MEMS capacitive acceleration sensor sensitive structure with stress isolation, referring to Figure 1 , a rectangular coordinate system is established with the center point of the acceleration sensor sensitive structure as the origin, the horizontal axis as the X-axis, and the vertical axis as the Y-axis; the acceleration sensor sensitive structure is symmetrical about the Y-axis along the horizontal axis direction and about the X-axis along the vertical axis direction, and includes a plurality of sensitive mass block frames 2, a plurality of detection comb connection structures 5, and a plurality of stress isolation structures provided on the substrate;

[0045] The detection comb teeth connection structure 5 is fixed on the substrate through a single point detection comb teeth anchor point 4. A plurality of non-movable electrode comb teeth 11 are arranged on both sides of the detection comb teeth connection structure 5 along the Y-axis direction.

[0046] The sensitive mass frames 2 are symmetrically arranged along the Y-axis and move along the sensitive axis. Two groups of sensitive mass frames 2 near the Y-axis are connected to each other, and the remaining adjacent sensitive mass frames 2 are connected by a U-shaped connection structure 3. A stop structure 10 is fixed to the substrate within the U-shaped connection structure 3 via a stress isolation anchor point 8, and the U-shaped connection structure 3 is connected to a U-shaped elastic sensitive beam 1. A plurality of movable electrode comb teeth 12 are provided on the sensitive mass frame 2. The movable electrode comb teeth 12 correspond one-to-one with the non-movable electrode comb teeth 11 to form a capacitor structure.

[0047] See also Figure 2 The stress isolation structure includes a stress transfer beam 9 connected to the U-shaped elastic sensitive beam 1. The stress transfer beam 9 is arranged along the Y-axis direction and is fixed to the substrate through a central anchor point 6; two ends of the stress transfer beam 9 are respectively provided with two stress concentration beams 7 extending along the X-axis, and the stress concentration beam 7 is connected to the stop structure 10.

[0048] By arranging the stress transfer beam 9 and the stress concentration beam 7 of the stress isolation structure, when the acceleration sensor is affected by changes in ambient temperature and its size expands due to heat or contracts due to cold, the thermal stress generated by the different thermal expansion coefficients between the substrate layer and the structural layer is released through the stress transfer beam 9 and the stress concentration beam 7. The stress is isolated outside the sensitive U-shaped elastic sensitive beam 1, thereby avoiding affecting the scale factor of the comb-tooth capacitive acceleration sensor and ensuring the temperature consistency of the sensor performance. At the same time, a stress isolation anchor point 8 is provided at the far end in the sensitive axis direction. By arranging the stress concentration beam 7 and the stress transfer beam 9 connected thereto, support is achieved for the far end of the sensitive mass block frame 2, thereby improving the modal separation ratio, reducing the cross-axis sensitivity, improving the out-of-plane overload resistance and stability of the acceleration sensor, and avoiding the influence of acceleration in the non-sensitive axis direction.

[0049] Example 2

[0050] The present invention discloses a MEMS capacitive acceleration sensor sensitive structure with stress isolation, referring to Figure 1 , a rectangular coordinate system is established with the center point of the acceleration sensor sensitive structure as the origin, the horizontal axis as the X-axis, and the vertical axis as the Y-axis; the acceleration sensor sensitive structure is symmetrical about the Y-axis along the horizontal axis direction and about the X-axis along the vertical axis direction, and includes a plurality of sensitive mass block frames 2, a plurality of detection comb connection structures 5, and a plurality of stress isolation structures provided on the substrate;

[0051] The detection comb tooth connection structure 5 is fixed on the substrate through a single point detection comb tooth anchor point 4. The detection comb tooth anchor point 4 is symmetrically arranged with the X axis as the symmetry axis. A plurality of non-movable electrode comb teeth 11 are arranged on both sides of the detection comb tooth connection structure 5 along the Y axis direction.

[0052] The sensitive mass frame 2 is symmetrically arranged along the Y-axis and moves along the sensitive axis. The two groups of sensitive mass frames 2 near the two sides of the Y-axis are connected to each other, and the remaining adjacent sensitive mass frames 2 are connected by a U-shaped connection structure 3. The width of the U-shaped connection structure 3 is ≥150μm. A stop structure 10 is fixed on the substrate within the U-shaped connection structure 3 via a stress isolation anchor point 8, and the U-shaped connection structure 3 is connected to a U-shaped elastic sensitive beam 1. The sensitive mass frame 2 is provided with a plurality of movable electrode comb teeth 12. The movable electrode comb teeth 12 correspond one-to-one with the non-movable electrode comb teeth 11 to form a capacitor structure. The aspect ratio of the movable electrode comb teeth 12 to the non-movable electrode comb teeth 11 is ≤30.

[0053] See also Figure 2 The stress isolation structure includes a stress transfer beam 9 connected to the U-shaped elastic sensitive beam 1, the width of the stress transfer beam 9 is ≥200μm, the stress transfer beam 9 is arranged along the Y-axis direction, and is fixed to the substrate through the central anchor point 6; the two ends of the stress transfer beam 9 are respectively provided with two stress concentration beams 7 extending along the X-axis, the length of the stress concentration beam 7 along the X-axis direction is ≥50μm, the width is ≤15μm, the stiffness of the stress concentration beam 7 is ≥20 times the stiffness of the U-shaped elastic sensitive beam 1, the stress concentration beam 7 is connected to the stop structure 10, and the stop structure 10 includes a plurality of rectangular protrusions arranged in sequence along the X-direction, and the distance between the rectangular protrusion and the U-shaped connection structure 3 is less than 2 / 3 of the gap between the capacitor structure plates.

[0054] Preferably, the sizes of the detection comb anchor points 4 and the central anchor point 6 are both ≥100*100 μm and ≤300*300 μm.

[0055] Example 3

[0056] The present invention also provides a MEMS capacitive acceleration sensor with stress isolation, comprising a substrate and the above-mentioned MEMS capacitive acceleration sensor sensitive structure with stress isolation.

[0057] See also Figure 1 and Figure 2The acceleration sensor sensitive structure includes a U-shaped elastic sensitive beam 1, a detection comb anchor point 4, a detection comb connection structure 5, a center anchor point 6, a stress isolation anchor point 8, a stress concentration beam 7, a stress transfer beam 9, a sensitive mass frame 2, movable electrode comb teeth 12, non-movable electrode comb teeth 11, a U-shaped connection structure 3, and a stop structure 10. A coordinate system is established with the center point of the acceleration sensor sensitive structure as the origin, the horizontal axis as the X-axis, and the vertical axis as the Y-axis. The acceleration sensor sensitive structure is symmetrically arranged with the X-axis as the axis of symmetry in the longitudinal direction and symmetrically arranged with the Y-axis as the axis of symmetry in the transverse direction.

[0058] The U-shaped elastic sensitive beam 1 is connected to the sensitive mass block frame 2; the sensitive mass block frame 2 is in the shape of a "mouth", can move along the sensitive axis direction, is set to 4, and is symmetrically arranged along the X axis and symmetrically arranged along the Y axis. The two sensitive mass block frames 2 located at the center of the acceleration sensor sensitive structure close to the Y axis are directly connected, and the sensitive mass block frame 2 located at the edge of the acceleration sensor sensitive structure is connected to the adjacent sensitive mass block frame 2 located in the center through a U-shaped connecting structure 3; the distance between the U-shaped connecting structure 3 and the rectangular protrusion of the stop structure 10 is less than 2 / 3 of the gap between the plates of the comb-tooth capacitor structure; the width of the U-shaped connecting structure 3 is not less than 150μm, otherwise the mode of the acceleration sensor will be complex and difficult to design.

[0059] The non-movable electrode comb teeth 11 are symmetrically arranged on both sides of the detection comb tooth connection structure 5, and the detection comb tooth connection structure 5 is fixed to the substrate via the detection comb tooth anchor points 4. The movable electrode comb teeth 12 are provided on the sensitive mass frame 2. The movable electrode comb teeth 12 correspond one-to-one with the non-movable electrode comb teeth 11, and the corresponding movable electrode comb teeth 12 and the non-movable electrode comb teeth 11 form a comb tooth capacitance structure; the movable electrode comb teeth 12 are arranged in sequence along two parallel sides of the frame of the sensitive mass frame 2, and the movable electrode comb teeth 12 are parallel to the X-axis;

[0060] The stress transfer beam 9 is connected to the U-shaped elastic sensitive beam 1, so that the sensitive mass block frame 2 can move along the sensitive axis direction. The connection is located at the edge of the stress transfer beam 9 and near the stress concentration beam 7, and the stress transfer beam 9 is fixed to the substrate through the central anchor point 6. The central anchor point 6 is located on the X-axis. Two stress concentration beams 7 are respectively provided at the two ends of the stress transfer beam 9. The stress concentration beam 7 is connected to the stop structure 10, and the stop structure 10 is fixed to the substrate through the stress isolation anchor point 8. The stress isolation anchor point 8 is set at the far end in the sensitive axis direction. The far end of the sensitive mass block frame 2 is supported by the stress concentration beam 7 and the stress transfer beam 9 connected thereto, which can reduce the modal separation ratio, reduce the cross-axis sensitivity, and improve the out-of-plane overload resistance of the acceleration sensor.

[0061] When the ambient temperature changes, the thick and long stress transfer beam 9 expands due to heat and contracts due to cold, causing the stress concentration beam 7 connected to the stress transfer beam 9 to undergo a large deformation, so that the stress is highly concentrated on the stress concentration beam 7 rather than on the U-shaped elastic sensitive beam 1, making its stiffness stable and not affected by temperature changes. The scale factor of the acceleration sensor is therefore stable, and the temperature coefficient of the scale factor is reduced.

[0062] Preferably, the stiffness of the stress concentration beam 7 is greater than or equal to 20 times the stiffness of the U-shaped elastic sensitive beam 1; the stiffness of the stress concentration beam 7 and the stiffness of the U-shaped elastic sensitive beam 1 will both affect the stiffness of the spring mass system of the acceleration sensor, so the stiffness of the stress concentration beam 7 is not less than 20 times that of the U-shaped elastic sensitive beam 1, otherwise the stiffness of the stress concentration beam 7 is close to the stiffness of the spring mass system and this stiffness is seriously affected by temperature.

[0063] Preferably, the length of the stress concentration beam 7 is ≥50 μm and the width is ≤15 μm. Otherwise, in a high temperature environment during wafer bonding, the stress concentration beam 7 may break due to high stress. After the break, the sensitive mass block is supported by the central anchor point 6, the vibration mode changes, and the acceleration sensor may not work properly.

[0064] Preferably, the width of the stress transfer beam 9 is at least 200 μm to ensure that the stress transfer beam 9 does not suffer from complex deformation such as lateral deformation along the X-axis.

[0065] Preferably, since wet etching may over-etch the protruding structure of the stop structure 10, the aspect ratio of the rectangular protrusion of the stop structure 10 is 2:1 or above, or additional small rectangles are added at the convex corners of the rectangular protrusion for convex corner compensation.

[0066] Preferably, the aspect ratio of the movable electrode comb teeth to the non-movable electrode comb teeth is ≤30:1, otherwise the ends of the electrode comb teeth will generate additional displacement when subjected to acceleration, thereby reducing the linearity of the acceleration sensor.

[0067] Preferably, the substrate is made of silicon or glass;

[0068] Preferably, the size of the detection comb anchor points 4 and the central anchor point 6 is ≥100×100 μm and ≤300×300 μm. Otherwise, large-sized anchor points will cause greater internal stress in the sensitive structure of the acceleration sensor and reduce output stability.

[0069] The central anchor points 6 on the two stress transfer beams 9 are both located on the X-axis and are symmetrical to each other along the Y-axis. Therefore, the displacement of the stress transfer beam 9 to both ends is consistent; the detection comb anchor points 4 are all close to the X-axis; the sensitive mass block frame 2 is only supported by the U-shaped elastic sensitive beam 1, and the stiffness of the U-shaped elastic sensitive beam 1 is relatively low, generally between 20N / m and 200N / m. Therefore, when the ambient temperature changes, the sensitive mass block frame 2 is almost free to expand from the center to the periphery due to heat or contract due to cold, driving the movable electrode comb 12 to move. The detection comb tooth connection structure 5 is fixed at only one end by the detection comb tooth anchor point 4 near the center of the acceleration sensor on the X-axis. When the ambient temperature changes, it also expands due to heat or contracts due to cold from the center to the surrounding area, driving the displacement of the non-movable electrode comb teeth 11 to be close to the displacement of the movable electrode comb teeth 12. Therefore, when the ambient temperature changes, the relative displacement between the movable electrode comb teeth 12 and the non-movable electrode comb teeth 11 is greatly reduced, the zero bias temperature coefficient of the acceleration sensor is greatly reduced, and the output stability of the acceleration sensor is improved.

[0070] The MEMS capacitive acceleration sensor with stress isolation in this embodiment can be widely used in detecting the linear acceleration of moving objects in various fields.

[0071] In summary, the present invention provides a MEMS capacitive acceleration sensor sensitive structure and sensor with stress isolation. By setting the stress transfer beam 9 and the stress concentration beam 7 of the stress isolation structure, the thermal stress is released through the stress transfer beam 9 and the stress concentration beam 7, and the stress is isolated outside the sensitive U-shaped elastic sensitive beam 1, thereby avoiding affecting the comb-tooth capacitive acceleration sensor scale factor and ensuring the temperature consistency of the sensor performance; at the same time, the stress isolation anchor point 8 at the far end of the sensitive axis direction, through the setting of the stress concentration beam 7 and the stress transfer beam 9 connected thereto, realizes the support of the far end of the sensitive mass block frame 2, thereby improving the modal separation ratio, reducing the cross-axis sensitivity, and improving the out-of-plane overload resistance and stability of the acceleration sensor, avoiding the influence of acceleration in the non-sensitive axis direction.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and replacements, and these modifications and replacements are also within the scope of protection covered by the claims.

Claims

1. A MEMS capacitive acceleration sensor with stress isolation, characterized in that: A rectangular coordinate system is established with the center point of the acceleration sensor as the origin, the horizontal axis as the X-axis, and the vertical axis as the Y-axis; the acceleration sensor is symmetrical about the Y-axis along the horizontal axis and about the X-axis along the vertical axis, and includes a plurality of sensitive mass block frames (2) arranged on a substrate, a plurality of detection comb connection structures (5), and a plurality of stress isolation structures; The detection comb tooth connection structure (5) is fixed on the substrate at a single point via a detection comb tooth anchor point (4), and a plurality of non-movable electrode comb teeth (11) are arranged on both sides of the detection comb tooth connection structure (5) along the Y-axis direction; The sensitive mass block frames (2) are symmetrically arranged along the Y axis and move along the sensitive axis direction; two groups of sensitive mass block frames (2) close to the Y axis are connected to each other, and the remaining adjacent sensitive mass block frames (2) are connected via a U-shaped connection structure (3); a stopper structure (10) is fixed on the substrate within the U-shaped connection structure (3) via a stress isolation anchor point (8), and the U-shaped connection structure (3) is connected to a U-shaped elastic sensitive beam (1); a plurality of movable electrode comb teeth (12) are provided on the sensitive mass block frame (2), and the movable electrode comb teeth (12) correspond to the non-movable electrode comb teeth (11) one by one to form a capacitor structure; The stress isolation structure comprises a stress transfer beam (9) connected to a U-shaped elastic sensitive beam (1), wherein the stress transfer beam (9) is arranged along the Y-axis direction and is fixed to the substrate via a central anchor point (6); two stress concentration beams (7) extending along the X-axis are respectively provided at two ends of the stress transfer beam (9), and the stress concentration beams (7) are connected to a stopper structure (10).

2. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The width of the U-shaped connecting structure (3) is ≥150 μm.

3. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The detection comb anchor points (4) are symmetrically arranged with the X-axis as the symmetry axis.

4. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The length of the stress concentration beam (7) along the X-axis direction is ≥50 μm, and the width of the stress concentration beam (7) is ≤15 μm.

5. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The aspect ratios of the movable electrode comb teeth (12) and the non-movable electrode comb teeth (11) are both ≤30.

6. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The sizes of the detection comb anchor points (4) and the central anchor point (6) are both ≥100*100 μm and ≤300*300 μm.

7. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The stop structure (10) comprises a plurality of rectangular protrusions arranged in sequence along the X direction, and the distance between the rectangular protrusions and the U-shaped connecting structure (3) is less than 2 / 3 of the gap between the plates of the capacitor structure.

8. The MEMS capacitive acceleration sensor with stress isolation according to claim 1, wherein: The width of the stress transfer beam is ≥200 μm.

9. The MEMS capacitive acceleration sensor with stress isolation according to any one of claims 1 to 8, characterized in that: The stiffness of the stress concentration beam (7) is ≥20 times the stiffness of the U-shaped elastic sensitive beam (1).

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