CN118294047A - MEMS multidimensional force sensor based on island structure - Google Patents
MEMS multidimensional force sensor based on island structure Download PDFInfo
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- CN118294047A CN118294047A CN202410433250.8A CN202410433250A CN118294047A CN 118294047 A CN118294047 A CN 118294047A CN 202410433250 A CN202410433250 A CN 202410433250A CN 118294047 A CN118294047 A CN 118294047A
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- 239000013598 vector Substances 0.000 claims abstract description 6
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- 239000000463 material Substances 0.000 claims description 6
- 238000005530 etching Methods 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 3
- 239000000758 substrate Substances 0.000 claims description 3
- 230000001939 inductive effect Effects 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 description 10
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- 238000004806 packaging method and process Methods 0.000 description 6
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- 230000008859 change Effects 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
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- 238000004088 simulation Methods 0.000 description 2
- 229910000570 Cupronickel Inorganic materials 0.000 description 1
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 description 1
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- 239000007769 metal material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 229910000623 nickel–chromium alloy Inorganic materials 0.000 description 1
- 238000012858 packaging process Methods 0.000 description 1
- 230000005622 photoelectricity Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
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Abstract
The invention discloses an island structure-based MEMS multidimensional force sensor, which comprises a strain body, a stress body, a sensitive element and a frame for supporting the strain body, wherein a plurality of raised island structures are arranged above the strain body and positioned at the center and the edge of the strain body, the sensitive element is arranged on the upper surface of the island structure, and the stress body is positioned on the island structure at the center. When an external force vector is applied to a stress body of the MEMS multidimensional force sensor, the stress body transmits an external force to a strain body of the MEMS multidimensional force sensor, so that the strain body deforms, and a sensitive element positioned on the strain body generates a corresponding output signal.
Description
Technical Field
The invention relates to a MEMS multidimensional force sensor, in particular to a MEMS multidimensional force sensor based on an island structure.
Technical Field
The multi-dimensional force sensor can sense force and torque in multiple dimensions at the same time by taking a Cartesian coordinate system as a reference, and output an electrical signal of the measured force vector or torque, so that the multi-dimensional force sensor has wide application prospect. The MEMS multidimensional force sensor can realize the precise measurement of force vectors and torque, and can precisely control the force in instruments and equipment such as robots, intelligent equipment and the like.
The multi-dimensional force sensor mainly comprises a metal strain gauge type multi-dimensional force sensor and an MEMS multi-dimensional force sensor. The multi-dimensional force sensor is a traditional force sensor which is widely applied at present, and is formed by sticking a plurality of metal strain gages on a strain body, wherein copper-nickel or nickel-chromium alloy is generally adopted as a strain force sensing resistor. When an external force is applied to the sensor, strain in the multidimensional force sensor can deform, so that the metal force sensitive resistor stuck on the strain sensor can stretch together, and the resistance value of the strain sensor can correspondingly change along with the lengthening or shortening of the metal material, so that the strain sensor is converted into an electric signal to detect multidimensional force and torque. Although the measuring range of the metal strain gauge type multidimensional force sensor is large, the problems of large size and weight, low resolution and sensitivity, poor linearity, large hysteresis, low response speed, high cost and the like exist, and the application of the metal strain gauge type multidimensional force sensor to high-precision and miniaturized equipment is limited.
The MEMS multidimensional force sensor is an MEMS sensor which utilizes a sensitive element to measure force-induced deformation, and consists of a strain body, a stress body, the sensitive element and a supporting frame. The strain body is a structure of a film, a beam and the like with a certain thickness, which is obtained by etching a substrate material, the stress body is a structure positioned in the center of the strain body, and the sensitive element is embedded in the strain body. When an external force vector is applied to a stress body of the MEMS multidimensional force sensor, the stress body transmits an external force to a strain body of the sensor, so that the strain body forms a shape, and a sensitive element embedded on the strain body generates a corresponding output. MEMS multidimensional force sensors can be measured by piezoresistance, piezoelectricity, capacitance, photoelectricity, etc., wherein piezoresistance MEMS multidimensional force sensors are most commonly used. The force sensitive resistor of the piezoresistive MEMS multidimensional force sensor is integrated in a strain body structure, stress/strain generated under the action of external load enables the resistance value of the force sensitive resistor to change, and the change quantity of the force sensitive resistor is further converted into a voltage signal in a Wheatstone bridge mode to detect the force or torque. Piezoresistive MEMS multidimensional force sensors typically use monocrystalline silicon as force sensitive resistor, which has a very high strain sensitivity coefficient. Common strain-type structures for MEMS multidimensional force sensors are diaphragm-type, cross-beam, double-cantilever, etc. Compared with a metal strain gauge type multidimensional force sensor, the MEMS multidimensional force sensor has the advantages of small size, high resolution, good linearity, small hysteresis, good temperature stability, high response speed, low cost and the like.
The application of MEMS technology has led to a substantial reduction in the size of multidimensional force sensors, but at the same time the strain body size has also been reduced. This results in practical applications in which it is difficult to apply an external force accurately to the central location on the strain body, and a small deviation will result in a large output inter-dimensional coupling. In addition, the MEMS multidimensional force sensor is limited by the preparation materials and the size of the MEMS multidimensional force sensor, compared with a metal strain gauge multidimensional force sensor, the MEMS multidimensional force sensor has the problem of small measuring range, the measuring range is required to be enlarged through packaging, and the packaging error can cause the deviation of the position of the external force applied to the strain body, so that the MEMS multidimensional force sensor can generate high coupling. Coupling is a major problem faced by MEMS multidimensional force sensors and is also an important factor limiting the wide application of MEMS multidimensional force sensors. Therefore, there is an urgent need to address the coupling problem of MEMS multidimensional force sensors.
Disclosure of Invention
In order to reduce the problem of coupling between output dimensions of the MEMS multidimensional force sensor caused by stress position deviation, the invention provides an island structure-based MEMS multidimensional force sensor. The MEMS multidimensional force sensor realized by the island structure effectively compensates the problem of large coupling while ensuring the advantages of small size, high resolution, high sensitivity, high linearity, low hysteresis, high response speed, low cost and the like, and the effect of the invention is still effective after the extended-range packaging, so that the MEMS multidimensional force sensor with wide range and low coupling can be realized. The MEMS multidimensional force sensor based on the island structure is expected to replace the traditional metal strain gauge multidimensional force sensor, and is widely applied in the fields of robots, high-precision automatic control and the like.
Based on the above purpose, the invention provides the following technical scheme:
An island structure-based MEMS multidimensional force sensor comprises a supporting frame, a strain body, a stress body and a sensitive element. The support frame is positioned around the strain body and is used for supporting the strain body; a plurality of raised island structures are arranged above the strain body, and the island structures are square, round or rectangular in shape and are positioned at the center and the edge of the strain body; the sensitive element is arranged on the upper surface of the island structure; the stress body is positioned on the island structure at the central position of the strain body.
The working principle of the MEMS multidimensional force sensor based on the island structure is as follows: when an external force vector is applied to a stress body of the MEMS multidimensional force sensor, the stress body transmits an external force to a strain body of the MEMS multidimensional force sensor, so that the strain body deforms, and a sensitive element positioned on the strain body generates a corresponding output signal. The island structure can reduce stress asymmetry introduced by force transfer asymmetry, thereby reducing inter-dimensional coupling of the multi-dimensional force sensor.
The thickness range of the island structure is larger than, smaller than or equal to the thickness of the strain body.
The strain body is a membrane, a beam or a beam-membrane combined structure based on the island structure MEMS multidimensional force sensor.
The sensing element is a piezoresistive, capacitive, inductive or piezoelectric element and the like.
The island-structure-based MEMS multidimensional force sensor has the following arrangement principle of the sensitive elements on the island structure: under the action of the measured axial force, the output signal corresponding to the axis is the largest, but the influence of other axes on the output signal is the smallest, namely the inter-dimensional coupling is the smallest.
The MEMS multidimensional force sensor based on the island structure is characterized in that the shape of the stress body is square, round, rectangular and the like.
And the inner wall and the outer wall of the supporting frame are square, round, polygonal and other structures with through holes or cavities.
The MEMS multidimensional force sensor based on the island structure forms the island structure by selectively etching or corroding a small part of the strain body material from the front side after the strain body is formed by selectively etching or corroding a part of the substrate material from the back side.
The island structure MEMS multidimensional force sensor provided by the invention has the following technical advantages:
1) When the stress point is not positioned at the center of the strain body, the island structure MEMS multidimensional force sensor can greatly reduce the coupling between the output dimensions; compared with the existing MEMS multidimensional force sensor, the island structure MEMS multidimensional force sensor provided by the invention has the advantage of low coupling;
2) The island structure MEMS multidimensional force sensor can reduce the inter-dimensional coupling caused by packaging errors, has the advantage of low coupling after packaging, and finally can realize the measuring range compared with a metal strain gauge multidimensional force sensor, but has the advantages of small inter-dimensional coupling, small size, high resolution, good linearity, small hysteresis, high response speed and low cost compared with a metal strain gauge, thus realizing the multidimensional force sensor with low coupling, wide measuring range, small size, high resolution, good linearity, small hysteresis, high response speed and low cost.
Drawings
FIG. 1 is a top view and a cross-sectional view of an island film structure MEMS three-dimensional force sensor in accordance with an embodiment of the present invention;
FIG. 2 is a top view and a cross-sectional view of an island beam structure MEMS three-dimensional force sensor in accordance with an embodiment of the present invention;
FIG. 3 is a graph showing the comparison result of input and output characteristic curves of an island film structure MEMS three-dimensional force sensor and a flat film structure MEMS three-dimensional force sensor when a stress point is deviated;
in the figure:
1-a support frame; 2-strain variants; 3-an island structure of a strain body; 4-an island structure at a central location; 5-a force-bearing body; 6-force sensitive resistor.
Detailed Description
The invention is further described by way of example with reference to the accompanying drawings, but in no way limit the scope of the invention.
The invention provides an island structure-based MEMS three-dimensional force sensor, which is shown in fig. 1 and 2, wherein the strain body of fig. 1 is of a diaphragm type and is called an island film structure, and the strain body of fig. 2 is of a cross beam and is called an island beam structure. The MEMS three-dimensional force sensor comprises a strain body, a force-receiving body, a sensing element (force-sensitive resistor) and a support frame. The island structures are positioned on the upper surface of the strain body, five islands are respectively that one island structure is positioned at the right center of the upper surface of the strain body and the edges of the upper surface of the four strain bodies, namely, the four island structures except the island structure at the center are respectively positioned at gaps between four sides of the island structure at the center and the supporting frame, and the shapes and the areas of the four island structures are identical.
In the packaging process or practical application of the MEMS three-dimensional force sensor, the stress body is not positioned at the exact center of the strain body due to packaging errors or stress point deviation, and the deviation is set to be 20um. Since the coupling of Fy to the X bridge is constant at 0, the coupling of Fy to the Z bridge is constant at 0, the coupling of Fx to the Y bridge is constant at 0, and the coupling of Fz to the X bridge is the same as the coupling of Fz to the Y bridge. The following analysis therefore mainly takes the two terms Fz to X bridge coupling and Fx to Z bridge coupling.
The finite element simulation software is used for simulation, when the side length of a diaphragm is 2.2mm x 2.2mm, the thickness of the diaphragm is 60um, and the thickness of an island structure is 40um, the input-output characteristic curve of the MEMS three-dimensional force sensor based on the island structure is shown in fig. 3 (a). As can be seen from the figure, the inter-dimensional couplings are respectively: the coupling of Fz to the X bridge is 3.5% and the coupling of Fx to the Z bridge is 4.4%.
In order to illustrate the low coupling characteristic of the island-structure-based MEMS three-dimensional force sensor compared with the traditional flat-film-structure-based MEMS three-dimensional force sensor, the flat-film-structure-based MEMS three-dimensional force sensor is tested, wherein the thickness of a diaphragm is 100um, and the rest parameters are the same. The input-output characteristic curve of the flat membrane structure MEMS three-dimensional force sensor is shown in FIG. 3 (b) by using finite element simulation software for simulation. As can be seen from the figure, the inter-dimensional couplings are respectively: the coupling of Fz to the X bridge is 22.5% and the coupling of Fx to the Z bridge is 15%.
Thus, in the present example, the island structure based MEMS three-dimensional force sensor of the present invention has a 6.5-fold reduced coupling compared to a flat film structure MEMS three-dimensional force sensor. In addition, the thicknesses of the membrane strain body and the island structure were changed, and the coupling value was changed as shown in table 1, wherein the island structure thickness 0um is the case of the flat membrane structure of the control group. It can be seen from table 1 that the thicker the island structure, the lower the coupling value, indicating that the island structure proposed by the present invention has the effect of reducing coupling.
TABLE 1
| Film thickness (um) | Island thickness (um) | Fx to Z bridge coupling (%) | Fz to X bridge coupling (%) |
| 100 | 0 | 15 | 22.5 |
| 90 | 10 | 12 | 10 |
| 80 | 20 | 8.5 | 6.3 |
| 70 | 30 | 6.3 | 4.2 |
| 60 | 40 | 4.4 | 3.5 |
It should be noted that the purpose of the disclosed embodiments is to aid further understanding of the present invention, but those skilled in the art will appreciate that: various alternatives and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the present invention should not be limited to the disclosure of the present embodiment, but the scope of the invention is defined by the claims.
Claims (7)
1. An island structure-based MEMS multidimensional force sensor comprises a supporting frame, a strain body, a stress body and a sensitive element. The support frame is positioned around the strain body and is used for supporting the strain body; a plurality of raised island structures are arranged above the strain body, and the island structures are square, round or rectangular in shape and are positioned at the center and the edge of the strain body; the sensitive element is arranged on the upper surface of the island structure; when an external force vector is applied to the stress body of the MEMS multidimensional force sensor, the stress body transmits external force to the strain body of the MEMS multidimensional force sensor, so that the strain body deforms, and a sensitive element positioned on the strain body generates a corresponding output signal.
2. The island-based MEMS multidimensional force sensor of claim 1, wherein the sensing element is a piezoresistive, capacitive, inductive or piezoelectric element.
3. The island-based MEMS multidimensional force sensor of claim 1, wherein the strain body is a membrane, a beam, or a beam-membrane bonded structure.
4. The island-based MEMS multidimensional force sensor of claim 1, wherein the arrangement principle of the sensing elements on the island structure is as follows: under the action of the measured axial force, the output signal corresponding to the axis is the largest, but the influence of other axes on the output signal is the smallest, namely the inter-dimensional coupling is the smallest.
5. The island-based MEMS multidimensional force sensor of claim 1, wherein the force body is square, circular, rectangular in shape.
6. The island-based MEMS multidimensional force sensor of claim 1, wherein the inner and outer walls of the support frame are square, circular, polygonal, etc. shaped structures with through holes or cavities.
7. The island-based MEMS multidimensional force sensor of claim 1, wherein the island structure is formed by selectively etching or corroding a small portion of the strain body material from the front side of the strain body after forming the strain body by selectively etching or corroding a small portion of the substrate material from the back side.
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| Publication Number | Publication Date |
|---|---|
| CN118294047A true CN118294047A (en) | 2024-07-05 |
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