A multi-force signal MEMS sensor resistant to inertial interference and a manufacturing method thereof
By designing a multi-force signal MEMS sensor with a movable external comb tooth structure, the problem of inertial interference of the six-axis force sensor in a dynamic environment is solved, and accurate measurement of six-axis force and torque signal and low-dimensional coupling effects are achieved.
Patent Information
- Application Number
- CN202211399694.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-09
- Publication Date
- 2025-02-07
- Estimated Expiration
- 2042-11-09
AI Technical Summary
Existing six-axis force sensors are susceptible to inertial interference in dynamic environments, resulting in reduced measurement signal error and accuracy.
A multi-force signal MEMS sensor is designed to reflect the magnitude of the force signal by changing the spacing between the pairs of capacitor plates, and by designing the external comb teeth into a movable structure, reducing the relative displacement caused by inertia, thereby reducing the Generation of interference signals.
It realizes accurate measurement of six-axis force and torque signals in a dynamic environment, and effectively reduces inertial interference, improves measurement accuracy and signal decoupling effect.
Smart Images
Figure CN115711691B_ABST
Abstract
Description
Technical Field
[0001] The present invention provides a multi-force signal MEMS sensor capable of resisting inertial interference and a manufacturing method thereof. The sensor can realize the measurement function of six-axis force and torque and can eliminate the interference of inertial effect on the measurement signal. Background Art
[0002] Sensor technology is very important for signal measurement, identification and accurate information exchange. Sensors have long become a symbol of advanced technology. Currently, sensors with different working principles are used in various industries. As a sensor with complete force and torque measurement functions in three-dimensional space, the six-axis force sensor can identify and sense force signals in multiple directions and has a very wide range of applications.
[0003] Most of the existing force signal sensors are three-axis force sensors, which can only detect force signals in the three directions of X, Y, and Z in three-dimensional space. However, the force signal in space is complex, and the detection of torque signals in three-dimensional space should also have corresponding detection means, so six-axis force sensors have emerged. In traditional six-axis force sensors, due to the large number of detection dimensions, signal cross-coupling is difficult to avoid. If the cross-coupling cannot be handled well, large errors will inevitably occur, resulting in a significant reduction in measurement accuracy. Therefore, the decoupling of inter-dimensional signals of six-axis force sensors is also an important issue.
[0004] The sensing unit of the traditional differential capacitive sensor is mainly composed of a comb-tooth capacitance pair consisting of a movable differential comb and a fixed differential comb. When the sensor is affected by an external force signal, the movable differential comb will move, while the fixed differential comb will remain stationary. At this time, a capacitance change output will be generated, reflecting the magnitude of the force signal. However, the sensor does not always work in a static environment. When the sensor is in a dynamic environment, the movable differential comb of the device will have a slight displacement due to inertia. This slight displacement will also cause an output with a capacitance change, which can be called an inertial interference output. This output should be avoided as much as possible in the actual design and application of the sensor. Summary of the invention
[0005] The object of the present invention is to provide a multi-force signal MEMS sensor that can resist inertial interference.
[0006] The present invention adopts the capacitive measurement principle, that is, the capacitance value is changed by changing the spacing between the capacitor plates, so as to reflect the size of the force signal, and includes a central boss, a movable main board, a Z-axis plate, internal comb teeth, external comb teeth, electrodes on the external comb teeth, a U-shaped beam, a peripheral fixed beam, electrodes on the peripheral fixed beam, a glass plate and electrodes on the glass plate;
[0007] The central boss is located at the center of the movable mainboard, and four Z-axis pole plates are connected to the movable mainboard, respectively located at 45°, 135°, 225° and 315° directions of the movable mainboard; two internal comb teeth are connected to each side of the movable mainboard, and a total of eight internal comb teeth are connected, and the two internal comb teeth on the same side have a certain distance;
[0008] The external comb teeth are connected to the peripheral fixed beam, and two external comb teeth are connected to each side of the inner side of the peripheral fixed beam, and a total of eight external comb teeth are connected, and two external comb teeth on the same side have a certain distance; the area of each external comb tooth close to the peripheral fixed beam is covered by the external comb tooth upper electrode;
[0009] Each inner comb tooth is placed in the middle of the gap between the corresponding outer comb teeth, and the inner comb teeth and the outer comb teeth do not touch each other, and each inner comb tooth has the same initial spacing with the adjacent outer comb teeth;
[0010] The peripheral fixed beam is connected to the movable main board by a U-shaped beam, and the U-shaped beam is respectively located at the right, bottom, left and top of the movable main board; the peripheral fixed beam is covered with the peripheral fixed beam upper electrode;
[0011] The bottom of the external fixed beam is bonded to the upper surface of the glass plate, and the central boss, the movable main board, the Z-axis pole plate, the inner comb teeth, the outer comb teeth, and the U-shaped beam are not in contact with the upper surface of the glass plate and are suspended;
[0012] The thickness of the outer comb teeth is greater than that of the inner comb teeth, and the area of the Z-axis electrode plate is greater than the area of the electrode on the glass plate.
[0013] Beneficial effects of the present invention:
[0014] Advantage 1: The multi-force signal MEMS sensor has achieved innovation in the design of anti-inertial interference. The sensing unit of the traditional differential capacitor structure is composed of movable comb teeth and fixed comb teeth. When subjected to external force signals, only the movable comb teeth can be displaced, while the fixed comb teeth cannot. Therefore, when inertia occurs, the movable comb teeth and the fixed comb teeth are relatively displaced, resulting in the output of unnecessary capacitance signals. In the structure proposed by the present invention, the structure that was originally supposed to be fixed comb teeth is changed to movable comb teeth located on the outside, so that when inertia occurs, the internal comb teeth and the external comb teeth are displaced together, which greatly reduces the relative displacement that causes the interference signal, thereby achieving the function of anti-inertial interference.
[0015] Advantage 2: The multi-force signal MEMS sensor has achieved innovation in the design of the decoupling method. The designed sensor has a special structure, the thickness of the outer comb teeth is greater than the thickness of the inner comb teeth, and the area of the Z-axis plate is greater than the area of the electrode on the glass plate. This enables the sensor to achieve decoupling between various signals while realizing six-axis force and torque signal detection. This structure has low self-decoupling cost and easy implementation process. It does not require the subsequent processing of coupled signals through curve compensation and other means, and the decoupling effect is obvious. In the signal output by the sensor during operation, the coupled signal accounts for only a very small proportion and can be almost ignored.
[0016] Advantage three: The multi-force signal MEMS sensor has refined the distribution of the comb tooth structure. The purpose of the comb tooth structure design is to generate a differential signal. This processing method can greatly improve the linearity of the sensor output capacitance and force relationship curve. Two external comb teeth are connected to each inner side of the peripheral fixed beam, and a total of 8 external comb teeth are connected. This refined design greatly improves the measurement sensitivity of the comb tooth sensor unit, and because its 8 external comb teeth are independent of each other, the characteristics of the output capacitance signal of a certain external comb tooth can be observed separately, and the type, direction, size and other information of the force signal can be judged by analyzing the overall changes in the capacitance of each part. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a top view of the structure of the present invention.
[0018] Figure 2 It is a three-dimensional schematic diagram of the structure of the present invention.
[0019] Figure 3 It is a right side view of the structure of the present invention.
[0020] Figure 4 It is a partial top view of the silicon device in the present invention.
[0021] Figure 5 It is a three-dimensional schematic diagram of the silicon device part in the present invention.
[0022] Figure 6 It is a schematic diagram of the structure of the inner comb teeth and the outer comb teeth in the present invention.
[0023] Figure 7 It is a partial top view of the glass plate in the present invention.
[0024] Figure 8 It is a flow chart of the sensor processing technology in the present invention. DETAILED DESCRIPTION
[0025] The present invention comprises a central boss, a movable main board, a Z-axis plate, internal comb teeth, external comb teeth, electrodes on the external comb teeth, a U-shaped beam, a peripheral fixed beam, electrodes on the peripheral fixed beam, a glass plate, and electrodes on the glass plate. In terms of sensing principle, the sensor measurement principle is a capacitive measurement principle, that is, the capacitance value is changed by changing the spacing between the capacitor plates, thereby reflecting the size of the force signal.
[0026] The central boss is located at the center of the movable mainboard, and four Z-axis pole plates are connected to the movable mainboard, respectively located at 45°, 135°, 225° and 315° directions of the movable mainboard. The internal comb teeth are connected to the movable mainboard, and two internal comb teeth are connected to each side of the movable mainboard, with a total of 8 internal comb teeth connected. Each internal comb tooth has 15 pairs of comb teeth evenly distributed, and the two internal comb teeth on the same side have a certain spacing.
[0027] The external comb teeth are connected to the peripheral fixed beam, and two external comb teeth are connected to each side of the inner side of the peripheral fixed beam, and a total of 8 external comb teeth are connected. 15 pairs of comb teeth are evenly distributed on each external comb tooth, and the two external comb teeth on the same side have a certain spacing. The area of each external comb tooth close to the peripheral fixed beam is covered by the external comb tooth upper electrode.
[0028] Each inner comb tooth is placed in the middle of the gap between the outer comb teeth, and the inner comb teeth and the outer comb teeth do not contact each other, and each inner comb tooth has the same initial spacing with the adjacent outer comb teeth.
[0029] The peripheral fixed beam is connected to the movable main board by a U-shaped beam, and the U-shaped beam is respectively located at the right, bottom, left and top of the movable main board. The peripheral fixed beam is covered with the peripheral fixed beam upper electrode.
[0030] The materials of the central boss, movable main board, Z-axis pole plate, inner comb teeth, outer comb teeth, U-shaped beam, and outer fixed beam are all silicon. The materials of the electrodes on the outer comb teeth, the electrodes on the outer fixed beam, and the electrodes on the glass plate are all gold.
[0031] The bottom of the external fixed beam is bonded to the upper surface of the glass plate, and the central boss, movable main board, Z-axis pole plate, internal comb teeth, external comb teeth, and U-shaped beam are not in contact with the upper surface of the glass plate and are suspended.
[0032] The principle of the sensor measuring the force in the Z-axis direction in three-dimensional space is: when the sensor is subjected to the force in the Z-axis direction, the Z-axis electrode plate is displaced in the corresponding direction, the distance between the Z-axis electrode plate and the electrode on the glass plate changes, and thus the capacitance value also changes.
[0033] The principle of the sensor measuring the force in the X / Y axis direction in three-dimensional space is: when the sensor is subjected to the force in the X / Y direction, the spacing between the inner comb teeth and the outer comb teeth in the corresponding direction changes, so the capacitance value in the corresponding direction also changes.
[0034] The principle of the sensor measuring the torque in the Z-axis direction in three-dimensional space is: when the sensor is subjected to the torque in the Z-axis direction, the movable mainboard and the parts connected to it rotate along the Z-axis together, and the spacing between each internal comb tooth and external comb tooth changes, so the capacitance value also changes.
[0035] The principle of the sensor measuring the torque in the X / Y axis direction in three-dimensional space is: when the sensor is subjected to the torque in the X / Y direction, the movable main board and the parts connected to it rotate together along the X / Y axis. At this time, the distance between the two sets of Z-axis plates parallel to the X / Y axis and the electrodes on the glass plate changes, and the change trend must be opposite. Therefore, the capacitance value changes, and it can be judged whether it is in the positive direction or negative direction along the X / Y axis based on the change trend.
[0036] The decoupling principle of the sensor for the force in the X-axis direction, the force in the Y-axis direction, and the moment in the Z-axis direction is as follows: in the structural design, the thickness of the outer comb teeth is greater than the inner comb teeth, and the area of the Z-axis plate is greater than the electrode area on the glass plate. When the sensor is subjected to the force in the X / Y-axis direction, the spacing between the inner comb teeth and the outer comb teeth in the X / Y-axis direction changes, and at this time, the spacing between the inner comb teeth and the outer comb teeth in the Y / X-axis direction is almost unchanged, and the total area of the comb teeth facing each other is unchanged. Since the area of the Z-axis plate is larger than the area of the positive electrode on the glass plate, the area of the Z-axis plate and the electrode facing each other on the glass plate is also unchanged, so the capacitance in the Y / X direction is almost unchanged, and the capacitance in the Z direction is also unchanged, so no large coupling output is generated. When the sensor is subjected to the moment in the Z-axis direction, the spacing between the Z-axis plate and the electrode on the glass plate remains unchanged, and the facing area remains unchanged, while the spacing between the inner comb teeth and the outer comb teeth changes, and the capacitance value changes. At this time, the decoupling of the force in the X-axis direction, the force in the Y-axis direction, and the moment in the Z-axis direction is achieved.
[0037] The decoupling principle of the sensor for the torque in the X-axis direction, the torque in the Y-axis direction, and the force in the Z-axis direction is as follows: when the sensor is subjected to the torque in the X / Y-axis direction, the distance between the two sets of Z-axis plates parallel to the X / Y-axis and the electrodes on the glass plate changes, and the trend of the change in the distance must be opposite, so the capacitance value changes. At this time, since the thickness of the outer comb teeth is greater than the thickness of the inner comb teeth, the total area facing each other remains unchanged, so no coupling output is generated. When the sensor is subjected to the force in the Z-axis direction, the distance between the four Z-axis plates and the electrodes on the glass plate changes, and the trend of the change is the same, so the capacitance value changes. Since the thickness of the outer comb teeth is greater than the thickness of the inner comb teeth, the total area facing each other remains unchanged, so no coupling output is generated either. At this time, the decoupling of the torque in the X-axis direction, the torque in the Y-axis direction, and the force in the Z-axis direction is achieved.
[0038] The central boss, movable mainboard, internal comb teeth and external comb teeth of the sensor are all suspended structures supported by beams and are not bonded to the glass plate, so they can be displaced in all directions. When the sensor works in a dynamic environment, due to inertia, the movable mainboard and its connected parts, such as the internal comb teeth, will be displaced in a certain direction, and at this time, the external comb teeth will also be displaced in the same direction. During the simultaneous displacement of the internal and external comb teeth in the same direction, the relative displacement is very small, so almost no interfering capacitance output is generated, thereby achieving anti-inertial interference.
[0039] In order to better understand the present invention, it is described in detail below with reference to the accompanying drawings.
[0040] like Figure 1 As shown, a structural top view of a multi-force signal MEMS sensor includes a central boss 1, a movable main board 2, a Z-axis pole plate 3a, internal comb teeth 4a, external comb teeth 5a, an electrode 6a on the external comb teeth, a U-shaped beam 7a, a peripheral fixed beam 8a, an electrode 9a on the peripheral fixed beam, and a glass plate 10.
[0041] like Figure 2 As shown, a three-dimensional schematic diagram of the structure of a multi-force signal MEMS sensor includes a central boss 1, a movable main board 2, a Z-axis pole plate 3a, internal comb teeth 4a, external comb teeth 5a, an electrode 6a on the external comb teeth, a U-shaped beam 7a, a peripheral fixed beam 8a, an electrode 9a on the peripheral fixed beam, and a glass plate 10.
[0042] like Figure 3 As shown, a right side view of a multi-force signal MEMS sensor includes a central boss 1, a Z-axis plate 3a, a peripheral fixed beam 8a, and a glass plate 10.
[0043] like Figure 4As shown, a partial top view of a silicon device in a multi-force signal MEMS sensor includes a central boss 1, Z-axis pole plates 3a, 3b, 3c, 3d, internal comb teeth 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, and electrodes 9a, 9b, 9c, 9d on the peripheral fixed beam.
[0044] like Figure 5 As shown, a three-dimensional schematic diagram of the silicon device part in a multi-force signal MEMS sensor includes external comb teeth 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, electrodes on the external comb teeth 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, U-shaped beams 7a, 7b, 7c, 7d, and peripheral fixed beams 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h.
[0045] like Figure 6 As shown, a structure diagram of internal comb teeth and external comb teeth in a multi-force signal MEMS sensor includes internal comb teeth 4a, external comb teeth 5a, and external comb teeth upper electrodes 6a.
[0046] like Figure 7 As shown, a top view of a glass plate portion in a multi-force signal MEMS sensor includes a glass plate 10 and electrodes 11a, 11b, 11c, and 11d on the glass plate.
[0047] The working principle of a MEMS sensor for multiple force signals of the present invention is:
[0048] When subjected to X-axis force, 4a, 4b, 4e, and 4f move, and the corresponding spacing between 5a, 5b, 5e, and 5f changes, generating a capacitance change output, indicating that X-axis force is detected.
[0049] When subjected to force in the Y-axis direction, 4c, 4d, 4g, and 4h move, and the corresponding spacing between 5c, 5d, 5g, and 5h changes, generating a capacitance change output, indicating that force in the Y-axis direction is detected.
[0050] When subjected to a force in the Z-axis direction, 3a, 3b, 3c, and 3d move, and the corresponding spacing between 11a, 11b, 11c, and 11d changes, generating a capacitance change output, indicating that a force in the Z-axis direction is detected.
[0051] When subjected to the torque in the X-axis direction, the distance between 3a, 3c and 11a, 11c increases, and the distance between 3b, 3d and 11b, 11d decreases, and a corresponding capacitance change output is generated, indicating that the torque in the X-axis direction is detected.
[0052] When subjected to a torque in the Y-axis direction, the distance between 3a, 3b and 11a, 11b increases, and the distance between 3c, 3d and 11c, 11d decreases, and a corresponding capacitance change output is generated, indicating that a torque in the Y-axis direction is detected.
[0053] When subjected to a torque in the Z-axis direction, the distance between 4a, 4c, 4e, 4g and 5a, 5c, 5e, 5g becomes smaller, and the distance between 4b, 4d, 4f, 4h and 5b, 5d, 5f, 5h becomes larger, resulting in a corresponding capacitance change output, indicating that a torque in the Z-axis direction is detected.
[0054] Figure 8 This is a processing flow chart of the sensor in the present invention, and the same filling pattern represents the same material.
[0055] (a) A 4-inch silicon wafer is used as the substrate, the back side is polished, and then the silicon wafer is cleaned.
[0056] (b) The cleaned silicon wafer is oxidized to form a SiO2 oxide layer on the surface.
[0057] (c) Remove the oxide layer on the back of the silicon wafer and spin-coat photoresist on the back of the silicon wafer. After spin coating, bake. Use a photolithography machine to transfer the mask pattern to the photoresist. Then perform the first RIE etching on the back of the silicon wafer with a depth of 30μm. This step is used to form the lower part of the outer comb teeth, form the post-resist removal, and clean the silicon wafer.
[0058] (d) The back side of the silicon wafer is spin coated and the mask pattern is transferred, and the back side of the silicon wafer is subjected to a second RIE etching with a depth of 40 μm. This step is used to form a peripheral fixing beam.
[0059] (e) Remove the SiO2 layer on the front of the silicon wafer. First, thin the front of the silicon wafer until the total thickness of the silicon wafer is 430μm, and then polish it. Then spin-coat the front of the silicon wafer with photoresist, and perform RIE etching on the front of the silicon wafer for the first time. The etching depth is 30μm. This step is used to initially form a boss structure and remove the resin for cleaning.
[0060] (f) After spin coating photoresist and masking on the front side, a 250nm gold layer is sputtered on the front side for the first time according to the pattern to serve as the electrode layer for the leads on the outer comb teeth.
[0061] (g) The front side is spin coated and masked again, and the front side of the silicon wafer in the previous step is etched for the second time with an etching depth of 40 μm. This step is used to form the upper part of the outer comb teeth and completely form the boss structure.
[0062] (h) A 250nm gold layer is sputtered a second time on the front side of the silicon wafer according to the mask pattern to serve as the electrode layer for the leads on the peripheral fixing beam.
[0063] (i) Finally, the third etching is performed to etch through the silicon wafer according to the silicon layer mask pattern. This step is used to form the internal comb teeth, Z-axis plate, U-shaped beam and other structures on the device.
[0064] (j) Use glass plates and clean them.
[0065] (k) The surface of the glass plate is first oxygen washed to improve the adhesion between the metal layer and the glass plate surface, and then a 250 nm thick gold layer is sputtered on the front side of the glass plate.
[0066] (l) Spin-coat the gold layer with photoresist, transfer the pattern of the gold electrode to the deposited gold layer, and then use wet etching to etch the gold layer into a pre-designed shape. This step is used to form structures such as gold electrodes and gold pads on the glass plate. After etching, remove the residual photoresist and clean it.
[0067] (m) Align the back of the silicon wafer and the front of the glass plate for bonding. Finally, slice and package the finished product after bonding. This completes the production of the multi-force signal MEMS sensor that is resistant to inertial interference.
[0068] In summary, the present invention is a MEMS sensor for multiple force signals, which can sense the force and torque signals of six axes in three-dimensional space, can achieve decoupling of signals between dimensions while making accurate measurements, and can achieve resistance to inertial interference in a dynamic environment. Existing force sensors are mainly based on three-axis force measurement, and the means of decoupling signals between dimensions are complex, and are prone to produce interference outputs affected by inertia in a dynamic environment. However, for complex situations, the use of the multi-force signal sensor that is resistant to inertial interference in the present invention can not only accurately measure the force and torque signals of each dimension, but also achieve low-dimensional coupling due to the structural characteristics, and self-resist inertial interference in a dynamic environment. The design of this structure has a very high reference value for applications in industrial devices, medical precision instruments and equipment, and even robotic arms. Therefore, the present invention provides a multi-force signal MEMS sensor that is resistant to inertial interference, which is of great significance for practical use in many industry fields.
Claims
1. A multi-force signal MEMS sensor that is resistant to inertial interference, adopts the capacitive measurement principle, that is, the capacitance value is changed by changing the spacing between the capacitor plates to reflect the size of the force signal, characterized by: It includes a central boss, a movable main board, a Z-axis pole plate, inner comb teeth, outer comb teeth, electrodes on the outer comb teeth, a U-shaped beam, a peripheral fixed beam, electrodes on the peripheral fixed beam, a glass plate, and electrodes on the glass plate; The central boss is located at the center of the movable mainboard, and four Z-axis pole plates are connected to the movable mainboard, respectively located at 45°, 135°, 225° and 315° directions of the movable mainboard; two internal comb teeth are connected to each side of the movable mainboard, and a total of eight internal comb teeth are connected, and the two internal comb teeth on the same side have a certain distance; The external comb teeth are connected to the peripheral fixed beam, and two external comb teeth are connected to each side of the inner side of the peripheral fixed beam, and a total of eight external comb teeth are connected, and two external comb teeth on the same side have a certain distance; the area of each external comb tooth close to the peripheral fixed beam is covered by the external comb tooth upper electrode; Each inner comb tooth is placed in the middle of the gap between the corresponding outer comb teeth, and the inner comb teeth and the outer comb teeth do not touch each other, and each inner comb tooth has the same initial spacing with the adjacent outer comb teeth; The peripheral fixed beam is connected to the movable main board by a U-shaped beam, and the U-shaped beam is respectively located at the right, bottom, left and top of the movable main board; the peripheral fixed beam is covered with the peripheral fixed beam upper electrode; The bottom of the peripheral fixed beam is bonded to the upper surface of the glass plate, and the central boss, the movable main board, the Z-axis pole plate, the inner comb teeth, the outer comb teeth, and the U-shaped beam are not in contact with the upper surface of the glass plate and are suspended; The thickness of the outer comb teeth is greater than that of the inner comb teeth, and the area of the Z-axis electrode plate is greater than the area of the electrode on the glass plate.
2. The multi-force signal MEMS sensor resistant to inertial interference according to claim 1, characterized in that: The materials of the central boss, movable main board, Z-axis pole plate, internal comb teeth, external comb teeth, U-shaped beam, and external fixed beam are all silicon; the materials of the electrodes on the external comb teeth, the electrodes on the peripheral fixed beam, and the electrodes on the glass plate are all gold.