Multi-dimensional force mems sensor resistant to inertial environmental disturbances

Abstract

The application discloses a multi-dimensional force MEMS sensor against inertia environmental interference. It comprises a substrate, a six-axis force sensor and an accelerometer. The six-axis force sensor is of a capacitive measurement principle. When subjected to an external force signal, the interval between the comb-tooth capacitor electrode plates of the sensor changes, thereby changing the capacitance value, and finally reflecting the size of the force signal. The accelerometer is also of a capacitive measurement principle. The application utilizes the measurement result of the accelerometer to correct the interference signal generated by the six-axis force sensor when subjected to inertia effect. The final result after correction is the measurement result with the inertia interference in the dynamic environment eliminated, so that accurate measurement is realized.

Description

TECHNICAL FIELD

[0001] The application provides a device capable of resisting inertial environmental interference and integrating a MEMS capacitive six-axis force sensor and a MEMS capacitive accelerometer and a manufacturing method thereof. The multi-dimensional force sensor can realize six-axis force and torque measurement through the six-axis force sensor, can detect the size of the inertial signal generated in the dynamic environment through the accelerometer, and corrects the interference effect of the inertial signal on the six-axis force sensor by using the detection result, so as to realize accurate measurement of force and torque signals in the dynamic environment. BACKGROUND

[0002] Sensing technology is an important technology for realizing signal sensing, measurement, identification, and information interaction and feedback. Sensors, as the core devices for realizing these functions, have been widely used in various fields such as military, machinery, medical treatment, vehicle manufacturing, and mobile devices. A six-axis force sensor has complete multi-dimensional force and torque measurement functions in the entire three-dimensional space and can detect force signals in multiple directions. An accelerometer is a common MEMS device for measuring acceleration. A general three-axis accelerometer can measure linear acceleration in each direction in space.

[0003] A six-axis force sensor can well replace the functions of a three-axis force sensor. The six-axis force sensor can not only measure force signals in X, Y, and Z directions in space like a three-axis force sensor, but also measure torque in these three directions, and can be flexibly used in many scenarios. However, the actual application of the six-axis force sensor may also face some potential problems. First, due to the large number of simultaneously detected dimensions, cross-talk between signals in complex scenarios is difficult to avoid. If a certain method is not used to weaken the cross-talk, the accuracy of the measurement results will be greatly affected, resulting in reduced measurement accuracy and reliability. Second, in general, the sensing unit of a differential capacitive sensor mainly consists of a movable part and a fixed part. The movable part of the six-axis force sensor has a relatively large mass and may also displace when affected by inertia in a dynamic environment. When the sensor is affected by external force signals, the movable part will also move, while the fixed part remains stationary. At this time, an interference signal output caused by inertia will be generated, which will also affect the normal operation of the device. Therefore, the above problems should be solved to greatly improve the reliability and measurement accuracy of the sensor. SUMMARY

[0004] In view of the above problems, the application provides a device integrated with a MEMS capacitive six-axis force sensor and a MEMS capacitive accelerometer and resistant to inertial environmental interference, which can realize six-axis force and torque measurement through the six-axis force sensor, detect the size of the inertial signal generated in a dynamic environment through the accelerometer, and correct the interference of the inertial signal on the six-axis force sensor by using the detection result, so as to realize accurate measurement of force and torque signals in a dynamic environment.

[0005] The application comprises a substrate, a six-axis force sensor and an accelerometer, wherein the six-axis force sensor is of a capacitive measurement principle, and when subjected to an external force signal, the distance between the pairs of comb-shaped capacitive electrode plates of the sensor changes, thereby changing the capacitance value and finally reflecting the size of the force signal.

[0006] The accelerometer is also of a capacitive measurement principle, and when subjected to acceleration in the X and Y directions, the distance between the pairs of comb-shaped capacitive electrode plates of the accelerometer in the X and Y axial directions changes, thereby changing the capacitance value in the corresponding direction; when subjected to acceleration in the Z direction, the normal area between the pairs of comb-shaped capacitive electrode plates of the accelerometer changes, thereby changing the capacitance value in the corresponding direction.

[0007] The measurement result of the accelerometer is used to correct the interference signal generated when the six-axis force sensor is subjected to inertial action, and the final result after correction is the measurement result in which the inertial interference in a dynamic environment is eliminated, so as to realize accurate measurement.

[0008] The application has the following beneficial effects:

[0009] Advantage 1: The multi-dimensional force MEMS sensor realizes innovation in structure and function. In practical applications, the movable main plate part of a traditional six-axis force sensor has a relatively large mass, so when working in a dynamic environment, the movable main plate part is also displaced due to inertial action, while the fixed comb-shaped part remains unchanged, at this time, an interference signal output caused by inertial action is generated, which may affect the parameters and performance of the device. In the structure of the application, an accelerometer for detecting and correcting the inertial signal is additionally processed and manufactured, because the accelerometer is sensitive to a dynamic environment, it can realize measurement of the displacement amount caused by inertial action and measurement of the capacitive signal, and serve as a correction signal; the measurement result of the six-axis force sensor is corrected by calculation of the correction signal, and the effective measurement result after elimination of interference is obtained, so as to realize the function of accurate measurement.

[0010] Advantage two: the multi-dimensional force MEMS sensor realizes innovation in the design of structural self-decoupling. The designed sensor structure is special, the thickness of the external comb teeth is greater than the thickness of the internal comb teeth, and the area of the Z-axis pole plate is greater than the area of the electrode on the glass plate, which enables the sensor to realize six-axis force and torque signal detection while decoupling between signals. This structure self-decoupling has low cost, simple implementation principle, and high processing feasibility, and does not need to process coupled signals through curve compensation and other means in the later stage, and the decoupling effect is obvious, and the coupled signal in the output signal of the sensor during operation only accounts for a very small proportion and can be ignored.

[0011] Advantage three: the multi-dimensional force MEMS sensor refines the distribution of the comb structure. The purpose of the comb structure design is to generate a differential signal, which can greatly improve the linearity of the sensor output capacitance and force relationship curve. For the six-axis force sensor part, each side of the movable main plate is connected with 2 groups of movable comb teeth, and a total of 8 groups of movable comb teeth are connected; for the accelerometer part, each side of the mass block is provided with 20 comb teeth, and a total of 80 comb teeth are connected. This refined design greatly improves the sensitivity of the comb sensing unit measurement, and can also observe the characteristics of the output capacitance signal of a certain external comb tooth due to its combination with the fixed comb tooth. By analyzing the capacitance change of each part, the type, direction, size and other information of the force signal can be determined. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural top view of the present application;

[0013] Figure 2 is a three-dimensional schematic diagram of the structure of the present application;

[0014] Figure 3 is a front view of the structure of the present application;

[0015] Figure 4 is a top view of the six-axis force sensor part in the present application;

[0016] Figure 5 is a schematic diagram of the glass plate part in the present application;

[0017] Figure 6 is a top view of the accelerometer part in the present application;

[0018] Figure 7 is a sensor processing process flowchart in the present application. DETAILED DESCRIPTION

[0019] The present application provides a multi-dimensional force MEMS sensor resistant to inertial environmental interference, which comprises a substrate, a six-axis force sensor and an accelerometer.

[0020] The six-axis force sensor is of a capacitive measurement principle. When an external force signal is applied, the distance between the pairs of comb-shaped capacitor plates of the sensor changes, thereby changing the capacitance value, and finally reflecting the size of the force signal. The accelerometer is also of a capacitive measurement principle. When affected by acceleration in the X and Y directions, the distance between the pairs of comb-shaped capacitor plates of the accelerometer in the X and Y axis directions changes, thereby changing the capacitance value in the corresponding direction. When affected by acceleration in the Z direction, the normal area between the pairs of comb-shaped capacitor plates of the accelerometer changes, thereby changing the capacitance value in the corresponding direction.

[0021] The multi-dimensional force MEMS sensor includes a substrate, a six-axis force sensor, and an accelerometer.

[0022] The six-axis force sensor includes a central boss, a movable main plate, Z-axis plates, movable combs, fixed combs, fixed comb upper electrodes, U-shaped beams, peripheral fixed beams, peripheral fixed beam upper electrodes, a glass plate, and glass plate upper electrodes.

[0023] The central boss is located at the center of the movable main plate. Four Z-axis plates are connected to the movable main plate and are located at 45°, 135°, 225°, and 315° directions of the movable main plate, respectively. The movable combs are connected to the movable main plate. Two movable combs are connected to each side of the movable main plate, and a total of eight movable combs are connected. Each movable comb is uniformly provided with 15 pairs of combs. The two movable combs on the same side have a certain spacing.

[0024] The fixed combs are bonded to the glass plate and are independent of each other. Each fixed comb is provided with a fixed comb upper electrode covering the area close to the peripheral fixed beam. Each movable comb is located in the gap of the fixed comb, and the fixed comb and the movable comb do not contact each other. Each movable comb has the same fixed initial spacing with the adjacent fixed comb.

[0025] The peripheral fixed beam is located at the outermost part of the six-axis force sensor and is bonded to the glass plate. The peripheral fixed beam is connected to the movable main plate through the U-shaped beam as a medium. The U-shaped beam is located at the right, lower, left, and upper of the movable main plate, and there are four U-shaped beams. The upper surface of the connection part of each U-shaped beam and the peripheral fixed beam is covered by the peripheral fixed beam upper electrode.

[0026] The central boss, the movable main plate, the Z-axis plates, the movable combs, the fixed combs, the U-shaped beams, and the peripheral fixed beams are all made of silicon. The fixed comb upper electrode, the peripheral fixed beam upper electrode, and the glass plate upper electrode are all made of gold.

[0027] The bottom of the outer fixed beam is bonded to the upper surface of the glass plate, the bottom of the fixed comb tooth is bonded to the upper surface of the glass plate, the glass plate is bonded to the substrate, the central boss, the movable main plate, the Z-axis pole plate, the movable comb tooth, the upper electrode of the peripheral fixed beam, and the U-shaped beam are all not in contact with the upper surface of the glass plate and are suspended.

[0028] The principle of the six-axis force sensor measuring force in the Z-axis direction in three-dimensional space is that when the sensor receives force in the Z-axis direction, the Z-axis pole plate is displaced in the corresponding direction, the distance between the Z-axis pole plate and the upper electrode of the glass plate changes, and thus the capacitance value also changes. The principle of the six-axis force sensor measuring force in the X / Y-axis direction in three-dimensional space is that when the sensor receives force in the X / Y direction, the distance between the movable comb tooth and the fixed comb tooth in the corresponding direction changes, and thus the capacitance value in the corresponding direction also changes. The principle of the six-axis force sensor measuring torque in the Z-axis direction in three-dimensional space is that when the sensor receives torque in the Z-axis direction, the movable main plate and each part connected thereto jointly rotate along the Z-axis, the distance between each movable comb tooth and fixed comb tooth changes, and thus the capacitance value also changes. The principle of the six-axis force sensor measuring torque in the X / Y-axis direction in three-dimensional space is that when the sensor receives torque in the X / Y direction, the movable main plate and each part connected thereto jointly rotate along the X / Y axis, at this time, the distance between the two groups of Z-axis pole plates parallel to the X / Y axis and the upper electrode of the glass plate changes, and the change trends are necessarily opposite, thus the capacitance value changes, and the direction along the X / Y axis can be determined to be positive or negative according to the change trend.

[0029] The decoupling principle of the six-axis force sensor for force in the X-axis direction, force in the Y-axis direction, and torque in the Z-axis direction is that in the structural design, the thickness of the fixed comb tooth is greater than that of the movable comb tooth, and the area of the Z-axis pole plate is greater than that of the upper electrode of the glass plate. When the sensor receives force in the X / Y-axis direction, the distance between the movable comb tooth and the fixed comb tooth in the X / Y direction changes, at this time, the distance between the movable comb tooth and the fixed comb tooth in the Y / X-axis direction is almost unchanged, the total opposite area of the comb tooth is unchanged, since the area of the Z-axis pole plate is greater than that of the upper positive electrode of the glass plate, the opposite area of the Z-axis pole plate and the upper electrode of the glass plate is also unchanged, thus the capacitance in the Y / X direction is almost unchanged, and the capacitance in the Z direction is also unchanged, thus no large coupling output is generated. When the sensor receives torque in the Z-axis direction, the distance between the Z-axis pole plate and the upper electrode of the glass plate is unchanged, the opposite area is also unchanged, while the distance between the movable comb tooth and the fixed comb tooth changes, and the capacitance value changes. At this time, the decoupling of force in the X-axis direction, force in the Y-axis direction, and torque in the Z-axis direction is achieved.

[0030] The decoupling principle of the six-axis force sensor for the moment of force in the X-axis direction, the moment of force in the Y-axis direction and the force in the Z-axis direction is as follows: when the sensor is subjected to the moment of force in the X / Y-axis direction, the spacing between the two groups of Z-axis polar plates in parallel direction of the X / Y-axis and the electrode on the glass plate changes, and the change trend is necessarily opposite, so the capacitance value changes, and at this time, since the fixed comb tooth thickness is greater than the movable comb tooth thickness, the total facing area does not change, so no coupling output is generated. When the sensor is subjected to the force in the Z-axis direction, the spacing between the four Z-axis polar plates and the electrode on the glass plate changes, and the change trend is the same, so the capacitance value changes, and since the fixed comb tooth thickness is greater than the movable comb tooth thickness, the total facing area does not change, so no coupling output is generated. At this time, the decoupling of the moment of force in the X-axis direction, the moment of force in the Y-axis direction and the force in the Z-axis direction is realized.

[0031] In the accelerometer structure, a mass block, an anchor point, a mass block comb tooth, an accelerometer fixed comb tooth and an accelerometer fixed beam are included. The mass block is a cubic structure and is connected to the four anchor points through straight beams. The four anchor points are located on the substrate and are located at 45°, 135°, 225° and 315° directions of the mass block respectively. The straight beams have the same thickness as the mass block and are suspended without contacting the substrate.

[0032] There are 20 mass block comb teeth evenly distributed on each side of the mass block. There are accelerometer fixed beams distributed on the facing direction of each side of the mass block. Each accelerometer fixed beam has 20 accelerometer fixed comb teeth evenly distributed on the side close to the mass block.

[0033] Each mass block comb tooth is located in the gap of the accelerometer fixed comb tooth, and the mass block comb tooth and the accelerometer fixed comb tooth do not contact each other. Each mass block comb tooth has the same initial spacing with the adjacent accelerometer fixed comb tooth. The thickness of the accelerometer fixed comb tooth is the same as the thickness of the mass block. The accelerometer fixed comb teeth located at 0° and 180° directions of the mass block are suspended without contacting the substrate, and the facing thickness with the mass block comb tooth is half of the thickness of the accelerometer fixed comb tooth, and the height is higher than the height of the mass block comb tooth. The accelerometer fixed comb teeth located at 90° and 270° directions of the mass block are suspended without contacting the substrate, and the facing thickness with the mass block comb tooth is half of the thickness of the accelerometer fixed comb tooth, and the height is lower than the height of the mass block comb tooth.

[0034] The principle that the accelerometer measures acceleration in X / Y axis direction in three-dimensional space is that when the accelerometer is affected by acceleration in X / Y direction, the distance between the mass block comb teeth and the fixed comb teeth of the accelerometer in the corresponding direction changes, and thus the capacitance value in the corresponding direction also changes. The principle that the accelerometer measures acceleration in Z axis direction in three-dimensional space is that when the accelerometer is affected by acceleration in Z direction, the facing area of the mass block comb teeth and the fixed comb teeth of the accelerometer in the corresponding direction changes, and thus the capacitance value in the corresponding direction also changes. If the mass block is affected by acceleration in the positive direction of Z axis, the mass block moves in the positive direction of Z axis, and the facing area of the mass block comb teeth and the fixed comb teeth of the accelerometer in the 0° and 180° direction of the mass block increases, while the facing area of the mass block comb teeth and the fixed comb teeth of the accelerometer in the 90° and 270° direction of the mass block decreases; if the mass block is affected by acceleration in the negative direction of Z axis, the mass block moves in the negative direction of Z axis, and the facing area of the mass block comb teeth and the fixed comb teeth of the accelerometer in the 0° and 180° direction of the mass block decreases, while the facing area of the mass block comb teeth and the fixed comb teeth of the accelerometer in the 90° and 270° direction of the mass block increases, and the direction of acceleration in Z axis can be determined according to the law.

[0035] The six-axis force sensor has a differential structure, and has high sensitivity and linearity. When the multi-dimensional force MEMS sensor works in a dynamic environment, the six-axis force sensor contained therein can measure forces and moments in each direction in space. Since the movable main plate of the six-axis force sensor has a certain mass, when it is affected by inertia in a dynamic environment, the movable main plate and the parts connected thereto, such as movable comb teeth, will also displace in a certain direction, and thus the movable comb teeth and the fixed comb teeth will change the distance therebetween, and thus a capacitance output is generated. However, the multi-dimensional force MEMS sensor contains an independently working accelerometer, which can measure the acceleration generated by inertia and output a capacitance signal, and thus the measurement result of the accelerometer can be used to correct the interference signal generated by the six-axis force sensor when affected by inertia, and the final result after correction is the measurement result in which the interference of inertia in a dynamic environment is eliminated, so that accurate measurement is realized.

[0036] The application also provides a manufacturing method of the multi-dimensional force MEMS sensor, which comprises the following steps:

[0037] The manufacturing method of the accelerometer in the multi-dimensional force MEMS sensor is as follows:

[0038] A 4-inch silicon wafer is selected as a substrate, and the silicon wafer is polished on both sides and then cleaned.

[0039] Remove the oxide layer on the back of the silicon wafer, spin the photoresist on the back of the silicon wafer and bake, transfer the mask pattern to the photoresist by using the photoetch machine, then perform the first etching on the back of the silicon wafer with a depth of 35 μm, which is used to form the lower part of the fixed beam and anchor point of the accelerometer, remove the photoresist after forming, and clean the silicon wafer.

[0040] Perform the second etching on the back of the silicon wafer with a depth of 35 μm, which is used to form the lower part of the fixed comb and mass of the accelerometer.

[0041] Thin the front of the silicon wafer to a total thickness of 175 μm.

[0042] Spin the photoresist and mask on the front, etch the front of the silicon wafer according to the pattern with a depth of 35 μm, which is used to form the upper part of the fixed beam and the upper part of the fixed comb of the accelerometer.

[0043] Perform the second etching on the front of the silicon wafer according to the pattern with a depth of 35 μm, which is used to form the lower part of the fixed beam of the accelerometer.

[0044] Finally, etch through the silicon wafer according to the pattern, which completely forms the fixed beam, fixed comb, mass, mass comb and anchor point structure of the accelerometer. Thus, the accelerometer is completed.

[0045] The manufacturing method of the six-axis force sensor in the multi-dimensional force MEMS sensor is as follows:

[0046] Select another silicon wafer, polish the back, and then clean the silicon wafer.

[0047] Clean the silicon wafer to form a SiO2 oxide layer on the surface.

[0048] Remove the oxide layer on the back of the silicon wafer, spin the photoresist on the back of the silicon wafer and bake, transfer the mask pattern to the photoresist by using the photoetch machine, then perform the first etching on the back of the silicon wafer with a depth of 70 μm, which is used to form the anchor point bonded with the glass and the lower part of the fixed comb, remove the photoresist after forming, and clean the silicon wafer.

[0049] 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 430 μm, and polish. Then spin the photoresist on the front of the silicon wafer, perform the first RIE etching on the front of the silicon wafer with a depth of 30 μm, which is used to initially form the boss structure, remove the photoresist and clean.

[0050] After spinning the photoresist and mask on the front, sputter 250 nm of gold layer on the front according to the pattern for the first time, which is used as the electrode layer of the fixed comb for the lead wire.

[0051] Front side spin-coating, mask, the front side of the silicon wafer in the previous step for the second etching, etching depth of 40 μm, this step is used to form the upper part of the external comb teeth, and completely form the boss structure.

[0052] In the silicon wafer front side by mask pattern second sputtering 250 nm gold layer, as the peripheral fixed beam on the electrode layer for lead.

[0053] Finally, the third etching, according to the silicon layer mask pattern etching through the silicon wafer, this step is used to form the device on the movable comb, Z axis plate, U type beam structure.

[0054] Using glass plate, and cleaning. First, the surface of the glass plate is washed with oxygen, to improve the adhesion of the metal layer and the glass plate surface, then sputtering 250 nm thick gold layer on the front side of the glass plate.

[0055] The surface of the gold layer is spin-coated with photoresist, and the pattern of the gold electrode is transferred to the deposited gold layer. Then wet etching is used to etch the gold layer into the pre-designed shape. This step is used to form the gold electrode and gold pad structure on the glass plate. After etching, the residual photoresist is removed and cleaned.

[0056] First, the back side of the silicon wafer and the front side of the glass plate are aligned and bonded. Thus, the six-axis force sensor is completed.

[0057] The back side of the glass plate is aligned and bonded with the front side of the substrate silicon wafer. Finally, the finished product is cut and packaged after bonding. Thus, the multi-dimensional force MEMS sensor is completed.

[0058] In order to better understand the present application, the following will be described in detail in conjunction with the drawings and examples.

[0059] Example:

[0060] As shown in Figure 1 , a structure top view of a multi-dimensional force MEMS sensor includes a substrate 1, a six-axis force sensor 2, an accelerometer 3, Z axis plates 6a, 6b, 6c, 6d, U-shaped beams 7a, 7b, 7c, 7d.

[0061] As shown in Figure 2 , a three-dimensional schematic view of a multi-dimensional force MEMS sensor structure includes a central boss 4, a movable main plate 5, Z axis plates 6a, U-shaped beams 7a, peripheral fixed beams 8, electrodes 9a, 9b, 9c, 9d on the peripheral fixed beams, and a mass 11.

[0062] As shown in Figure 3 , a front view of a multi-dimensional force MEMS sensor includes a substrate 1, a peripheral fixed beam 8, and a glass plate 10.

[0063] AsFigure 4 Figure 1 is a schematic diagram of a six-axis force sensor portion of a multi-dimensional force MEMS sensor, including movable combs 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, fixed combs 13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h, and fixed comb electrodes 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h.

[0064] Figure 2 is a schematic diagram of a glass plate portion of a multi-dimensional force MEMS sensor, including glass plate 10 and glass plate electrodes 15a, 15b, 15c, 15d. Figure 5

[0065] Figure 3 is a schematic diagram of an accelerometer portion of a multi-dimensional force MEMS sensor, including mass 11, anchor points 16a, 16b, 16c, 16d, mass combs 17a, 17b, 17c, 17d, accelerometer fixed beams 18a, 18b, 18c, 18d, and accelerometer fixed combs 19a, 19b, 19c, 19d. Figure 6

[0066] The working principle of a multi-dimensional force MEMS sensor according to the present application is as follows:

[0067] When a force in the X-axis direction is applied, 12a, 12b, 12e, 12f move, and the spacing between them and 13a, 13b, 13e, 13f changes accordingly, resulting in a change in capacitance output, indicating that a force in the X-axis direction has been detected.

[0068] When a force in the Y-axis direction is applied, 12c, 12d, 12g, 12h move, and the spacing between them and 13c, 13d, 13g, 13h changes accordingly, resulting in a change in capacitance output, indicating that a force in the Y-axis direction has been detected.

[0069] When a force in the Z-axis direction is applied, 6a, 6b, 6c, 6d move, and the spacing between them and 15a, 15b, 15c, 15d changes accordingly, resulting in a change in capacitance output, indicating that a force in the Z-axis direction has been detected.

[0070] When a moment in the X-axis direction is applied, 6c, 6d move closer to 15c, 15d, and 6a, 6b move farther away from 15a, 15b, resulting in a change in capacitance output, indicating that a moment in the X-axis direction has been detected.

[0071] When a moment in the Y-axis direction is applied, 6a, 6d move farther away from 15a, 15d, and 6b, 6c move closer to 15b, 15c, resulting in a change in capacitance output, indicating that a moment in the Y-axis direction has been detected.

[0072] ​​When a moment in the Z-axis direction is applied, the distance between 12a, 12c, 12e, 12g and 13a, 13c, 13e, 13g is reduced, the distance between 12b, 12d, 12f, 12h and 13b, 13d, 13f, 13h is increased, and a corresponding capacitance change output is generated, indicating that a moment in the Z-axis direction is detected.

[0073] In summary, the multi-dimensional force sensor of the embodiment can realize measurement of six-axis force and moment through the six-axis force sensor, can detect the inertia signal size generated in a dynamic environment through the accelerometer, and can correct the interference of the inertia signal on the six-axis force sensor by using the detection result, so that precise measurement of force and moment signals in a dynamic environment is realized. The structure and design idea have very high reference value for applications in the fields of industrial equipment, medical precision instrument equipment, and even robot hands.

[0074] The present example also relates to a manufacturing method of the multi-dimensional force MEMS sensor, which is described as follows in combination with a process flow:

[0075] Figure 7 The process flow chart of the sensor in the present application, the same filling pattern represents the same material.

[0076] (a) A 4-inch silicon wafer is selected, both sides are polished, and then the silicon wafer is cleaned and oxidized.

[0077] (b) The oxide layer on the back of the silicon wafer is removed, photoresist is spin-coated on the back of the silicon wafer and baked, a mask plate pattern is transferred to the photoresist by using a photoetching machine, and then the back of the silicon wafer is etched for the first time to a depth of 35 μm. This step is used to form the lower part of the accelerometer fixed beam and anchor point. After formation, the photoresist is removed, and the silicon wafer is cleaned.

[0078] (c) The back of the silicon wafer is etched for the second time to a depth of 35 μm. This step is used to form the lower part of the lower accelerometer fixed comb and mass.

[0079] (d) The front of the silicon wafer is thinned to a total thickness of 175 μm.

[0080] (e) The photoresist and mask are spin-coated on the front, and the front of the silicon wafer is etched according to the pattern to a depth of 35 μm. This step is used to form the upper part of the higher accelerometer fixed comb and the upper part of the higher accelerometer fixed beam.

[0081] (f) The front of the silicon wafer is etched for the second time according to the pattern to a depth of 35 μm. This step is used to form the lower accelerometer fixed beam.

[0082] (g) Finally, etch through the silicon wafer according to the pattern, which completely forms the fixed beam, fixed comb of the accelerometer, mass, mass comb, anchor point structure. At this point, the accelerometer is completed.

[0083] The method for manufacturing the six-axis force sensor in the multi-dimensional force MEMS sensor is as follows:

[0084] (h) Select another silicon wafer, polish the back surface, and then clean the silicon wafer.

[0085] (i) The cleaned silicon wafer is oxidized to form a SiO2 oxide layer on the surface.

[0086] (j) Remove the oxide layer on the back surface of the silicon wafer, spin-coat photoresist on the back surface of the silicon wafer, and bake. Use a photoetching machine to transfer the mask pattern to the photoresist, then perform the first RIE etching on the back surface of the silicon wafer to a depth of 70 μm. This step is used to form the anchor point for bonding with the glass and the lower part of the fixed comb. After forming, remove the photoresist and clean the silicon wafer.

[0087] (k) Remove the SiO2 layer on the front surface of the silicon wafer. First, thin the front surface of the silicon wafer until the total thickness of the silicon wafer is 430 μm, and then polish. Then spin-coat photoresist on the front surface of the silicon wafer, and perform the first RIE etching on the front surface of the silicon wafer to a depth of 30 μm. This step is used to initially form the boss structure, and then remove the photoresist and clean.

[0088] (l) After spin-coating photoresist and masking on the front surface, sputter 250 nm of gold layer on the front surface according to the pattern for the first time, which is used as the electrode layer for the lead on the fixed comb.

[0089] (m) Spin-coat and mask again on the front surface, and perform the second etching on the front surface of the silicon wafer in the previous step to a depth of 40 μm. This step is used to form the upper part of the external comb, and completely form the boss structure.

[0090] (n) Sputter 250 nm of gold layer on the front surface of the silicon wafer according to the mask pattern for the second time, which is used as the electrode layer for the lead on the peripheral fixed beam.

[0091] (o) Finally, perform the third etching according to the silicon layer mask pattern to etch through the silicon wafer. This step is used to form the movable comb, Z-axis plate, U-shaped beam, and other structures on the device.

[0092] (p) Use a glass plate and clean it. First, perform oxygen washing on the surface of the glass plate to improve the adhesion between the metal layer and the surface of the glass plate, and then sputter 250 nm of gold layer on the front surface of the glass plate.

[0093] (q) spin photoresist on the surface of the gold layer, transfer the layout of the gold electrode to the gold layer that has been deposited, then use wet etching to etch the gold layer into the pre-designed shape, which is used to form the gold electrode, gold pad and other structures on the glass plate. After etching, remove the residual photoresist and clean.

[0094] (r) align the back of the silicon wafer and the front of the glass plate first, and then bond them, thus completing the fabrication of the six-axis force sensor.

[0095] (s) align and bond the back of the glass plate and the back of the accelerometer silicon wafer in the completed six-axis force sensor with the front of the substrate silicon wafer, and finally dice and package the finished product after bonding, thus completing the fabrication of the multi-dimensional force MEMS sensor.

Claims

1. A multi-dimensional force MEMS sensor against inertia environmental interference, comprising a substrate, a six-axis force sensor and an accelerometer, the six-axis force sensor being of a capacitive measurement principle, when subjected to an external force signal, the spacing between the pairs of comb-shaped capacitive electrode plates of the sensor changes, thereby changing the capacitance value, and finally reflecting the size of the force signal; the accelerometer is also of a capacitive measurement principle, when subjected to acceleration in the X and Y directions, the spacing between the pairs of comb-shaped capacitive electrode plates of the accelerometer in the X and Y axis directions changes, thereby changing the capacitance value in the corresponding direction; when subjected to acceleration in the Z direction, the normal area between the pairs of comb-shaped capacitive electrode plates of the accelerometer changes, thereby changing the capacitance value in the corresponding direction; the measurement results of the accelerometer are used to correct the interference signal generated by the six-axis force sensor when subjected to inertia, the final results after correction are the measurement results with the inertia interference in the dynamic environment eliminated, thereby realizing accurate measurement; the six-axis force sensor comprises a central boss, a movable main plate, Z-axis electrode plates, movable combs, fixed combs, fixed comb upper electrodes, U-shaped beams, peripheral fixed beams, peripheral fixed beam upper electrodes, a glass plate and glass plate upper electrodes; the central boss is located at the center of the movable main plate, four Z-axis electrode plates are connected with the movable main plate and are located at 45°, 135°, 225° and 315° directions of the movable main plate respectively; the movable combs are connected with the movable main plate, two movable combs are connected on each side of the movable main plate, and a total of eight movable combs are connected, and 15 pairs of combs are uniformly distributed on each movable comb, and the two movable combs on the same side have a certain spacing; the fixed combs are bonded on the glass plate, and there are a total of eight fixed combs which are independent of each other, and the fixed comb upper electrodes cover the area near the peripheral fixed beams on each fixed comb; each movable comb is located in the gap of the fixed comb, and the fixed comb and the movable comb do not contact each other, and each movable comb and the adjacent fixed comb have the same fixed initial spacing; the peripheral fixed beams are located at the outermost part of the six-axis force sensor, are bonded on the glass plate, and the peripheral fixed beams and the movable main plate are connected by the U-shaped beams as the medium, and the U-shaped beams are located at the right, lower, left and upper of the movable main plate respectively, and there are a total of four U-shaped beams; the upper surface of the connection part of each U-shaped beam and the peripheral fixed beam is covered by the peripheral fixed beam upper electrode; the bottom of the peripheral fixed beam and the upper surface of the glass plate are bonded, the bottom of the fixed comb and the upper surface of the glass plate are bonded, the glass plate and the substrate are bonded, and the central boss, the movable main plate, the Z-axis electrode plates, the movable combs, the peripheral fixed beam upper electrodes and the U-shaped beams are not in contact with the upper surface of the glass plate and are suspended.

2. The multi-dimensional force MEMS sensor of claim 1, wherein: the thickness of the fixed comb is greater than that of the movable comb, and the area of the Z-axis electrode plate is greater than that of the glass plate upper electrode.

3. The multi-dimensional force MEMS sensor of claim 1, wherein: The accelerometer structure comprises a mass block, anchor points, mass block combs, accelerometer fixed combs, and accelerometer fixed beams; the mass block is a cubic structure and is connected to the four anchor points through straight beams, the four anchor points are located on the substrate and are respectively located at 45°, 135°, 225° and 315° directions of the mass block; the straight beams have the same thickness as the mass block and are not in contact with the substrate and are suspended.

4. The multi-dimensional force MEMS sensor of claim 3, wherein: The mass block has 20 mass block combs evenly distributed on each side; the mass block has accelerometer fixed beams distributed in the opposite direction of each side, the accelerometer fixed beams are located on the substrate, and each accelerometer fixed beam has 20 accelerometer fixed combs evenly distributed on the side close to the mass block.

5. The multi-dimensional force MEMS sensor of claim 3, wherein: Each mass block comb is located in the gap of the accelerometer fixed comb, and the mass block comb and the accelerometer fixed comb are not in contact with each other, and each mass block comb and the adjacent accelerometer fixed comb have the same initial spacing; The accelerometer fixed comb has the same thickness as the mass block; the accelerometer fixed combs located at 0° and 180° directions of the mass block are not in contact with the substrate and are suspended, and the thickness of the opposite mass block comb is half of the thickness of the accelerometer fixed comb, and the height is higher than the height of the mass block comb; the accelerometer fixed combs located at 90° and 270° directions of the mass block are not in contact with the substrate and are suspended, and the thickness of the opposite mass block comb is half of the thickness of the accelerometer fixed comb, and the height is lower than the height of the mass block comb.

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