Planar semiconductor technology-based six-dimensional force sensor and preparation method thereof

Abstract

The invention relates to the technical field of sensors, and provides a six-dimensional force sensor based on a planar semiconductor process and a preparation method thereof, and the six-dimensional force sensor comprises a central bearing platform, a housing, an elastic beam and a buffer beam. One end of the elastic beam is connected to the center bearing table, the other end of the elastic beam is connected to the buffer beam, the buffer beam and the elastic beam are orthogonally arranged, and the end, away from the elastic beam, of the buffer beam is connected to the shell. Wherein the surfaces of the elastic beam and the buffer beam are provided with six groups of strain gauges, and the six groups of strain gauges are respectively used for measuring forces in three directions and moments in three directions. According to the method, the multi-load-step-based least square method linear matrix decoupling is adopted, so that the inter-dimensional coupling error of the six-dimensional force sensor is reduced to below 2%. According to the invention, the six-dimensional force sensor is prepared by adopting a planar semiconductor process, the difficulties of side surface attachment and side wall lead binding of the strain gauges are avoided, and the six-dimensional force sensor has the advantages of simple process, low manufacturing cost and small crosstalk error.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and more specifically, to a six-dimensional force sensor based on a planar semiconductor process and a preparation method thereof. Background Art

[0002] In recent years, as intelligent robots have gradually become the mainstream in the field of robot development, the key components to achieve intelligence, and the research and development of six-dimensional force sensors have gradually become important. In the robotics industry, most industrial robots still rely on position control to complete their work, such as typical production robotic arms. As an important information sensing element for robots to interact with the outside world, six-dimensional force sensors provide key sensing information for realizing robot force control, which plays a key role in the robot's high-precision operations under complex working conditions and the advancement of its flexibility and intelligence. Six-dimensional force sensors are a type of sensor that can simultaneously detect forces in the X, Y, and Z axes (i.e., Fx, Fy, Fz) and moments around these three coordinate axes (i.e., Mx, My, Mz). It uses precisely designed elastic bodies and signal conditioning circuits to measure and feedback six independent force and torque components in three-dimensional space in real time to ensure the comprehensiveness and accuracy of the measurement results.

[0003] The working principle of the six-dimensional force sensor is based on the conversion of physical deformation and electrical signals. Taking the resistive strain sensor as an example, when the elastic body is subjected to external force, it will deform, and this deformation causes the resistance value of the strain gauge attached to the elastic body to change. By measuring the change in resistance value, the magnitude of the external force and torque can be inferred. According to the different sensing elements, the six-dimensional force sensor is mainly divided into strain gauge type, optical type, and piezoelectric / capacitive type. Among them, strain gauge sensors are widely used in the market due to their high sensitivity, large measurement range, high reliability, and mature technology. Strain gauge sensors can be further divided into metal resistance strain gauges and silicon strain gauges. Among them, silicon strain sensors are particularly outstanding in terms of stability, signal-to-noise ratio and stiffness, and silicon strain gauges work based on the principle of piezoresistive effect, which has greater sensitivity than metal strain gauges.

[0004] According to the structure of the elastic body, the six-axis force sensor can be divided into three-beam, cross-beam, eight-beam and other structures. The traditional six-axis force sensor attaches the strain gauge on the elastic beam, senses the strain of the elastic body and causes the corresponding resistance change, which is then converted into a voltage signal output. Usually, the strain gauge is attached to the upper and lower surfaces of the elastic beam to sense and measure the pressure and deformation in the vertical direction (such as Fz, Mx and My), and the strain gauge is attached to the left and right sides of the elastic beam to sense and measure the pressure and deformation in the horizontal direction (such as Fx, Fy and Mz). The problem brought about by this is that the side attachment of the strain gauge and the bonding of the bonding wires are difficult, which affects the measurement accuracy of the six-axis force sensor. Summary of the invention

[0005] 1. Technical issues to be resolved The technical problem to be solved by the present invention is that the side mounting and wire bonding operations of the strain gauge of the existing six-dimensional force sensor are difficult, and the measurement accuracy of the six-dimensional force sensor is low.

[0006] (II) Technical solution To achieve the above object, the technical solution adopted by the present invention is: In a first aspect, the present invention provides a six-dimensional force sensor based on a planar semiconductor process, comprising a central support platform, a housing, an elastic beam and a buffer beam; one end of the elastic beam is connected to the central support platform, the other end of the elastic beam is connected to the buffer beam, the buffer beam is arranged orthogonally to the elastic beam, and the end of the buffer beam away from the elastic beam is connected to the housing; Among them, six groups of strain gauges are arranged on the surface of the elastic beam and the buffer beam, each group of the strain gauges forms an independent Wheatstone full-bridge circuit, and the six groups of strain gauges are respectively used to measure the forces in the three directions of Fx, Fy, and Fz and the moments in the three directions of Mx, My, and Mz.

[0007] Preferably, it further comprises a signal acquisition module and a terminal, the six groups of Wheatstone full-bridge circuits are electrically connected to the input end of the signal acquisition module respectively, and the output end of the signal acquisition module is electrically connected to the terminal.

[0008] Preferably, the terminal adopts least squares linear matrix decoupling based on multiple load steps.

[0009] Preferably, the strain gauge is a semiconductor silicon strain gauge.

[0010] Preferably, the six groups of strain gauges are arranged on the upper and lower surfaces of the elastic beam and the buffer beam.

[0011] Preferably, each group of strain gauges comprises four strain gauges.

[0012] Preferably, the strain gauge is attached and fixed to the surfaces of the elastic beam and the buffer beam by means of resin material.

[0013] In a second aspect, the present invention further provides a method for preparing a six-dimensional force sensor based on a planar semiconductor process as described in any one of the above technical solutions, comprising the following steps: Prepare and connect the central bearing platform, the housing, the elastic beam and the buffer beam; Adhere each set of strain gauges to the upper and lower surfaces of the elastic beam and the buffer beam through a resin material; High temperature curing to fix each set of strain gauges to the elastic beam and the buffer beam; Lead welding is performed to electrically connect each set of strain gauges to form an independent Wheatstone full-bridge circuit to obtain a six-dimensional force sensor; Performing sealing and finished product inspection on the six-dimensional force sensor; Conducting finished product performance testing on the six-dimensional force sensor; After the finished product performance test is qualified, the six-dimensional force sensor is packaged.

[0014] Preferably, the method for preparing the strain gauge comprises the following steps: The silicon wafers are cleaned by the standard RCA process; Make masks, prepare substrate glue, and shape substrate; Spin-coat photoresist on the silicon wafer, use a mask to photolithographically form a sensitive piezoresistor pattern, and obtain a strain gauge resistance pattern; etching the silicon wafer to remove the photoresist, and rapidly annealing at 350° C. to obtain a strain gauge; Conduct resistance test on strain gauge resistors; The resistance film of the strain gauge is engraved by laser technology to adjust the resistance value of the strain gauge.

[0015] (III) Beneficial effects The above technical solution of the present invention has at least the following advantages: 1. The six-dimensional force sensor provided by the present invention can be prepared by a planar semiconductor process, and each set of strain gauges is set on the upper and lower surfaces of the elastic beam and the buffer beam. The strain gauges are only attached to the upper and lower surfaces of the elastic beam and the buffer beam, avoiding the operational difficulties caused by side attachment and sidewall lead binding, simplifying the operational difficulty, and reducing the process cost. In the present invention, six sets of strain gauges are set on the surface of the elastic beam and the buffer beam, and each set of strain gauges forms an independent Wheatstone full-bridge circuit. The six sets of strain gauges are used to measure the forces in the three directions of Fx, Fy, and Fz and the moments in the three directions of Mx, My, and Mz, respectively. By adopting the least squares linear matrix decoupling based on multiple load steps, the inter-dimensional coupling error of the six-dimensional force sensor is reduced to less than 2%. By fitting the linear relationship between the input and output, the inter-dimensional crosstalk can be minimized, the decoupling accuracy can be improved, and the measurement accuracy of the six-dimensional force sensor is greatly improved.

[0016] 2. In the present invention, the resistance material of the strain gauge is not the traditional metal foil strain gauge, but a P-type doped silicon strain gauge. The P-type doped silicon strain gauge has the largest piezoresistance coefficient and a sensitivity of up to 170, making it an ideal conversion material for measuring tiny deformations. In addition, its resistance temperature coefficient is small and its sensitivity temperature coefficient is negative, which can offset the temperature effect caused by the resistance and piezoresistance coefficient and achieve a temperature compensation effect.

[0017] 3. In the present invention, 24 strain gauges are arranged on the surfaces of the elastic beam and the buffer beam. The strain gauges are attached to the upper and lower surfaces of the sensor through resin materials and are cured at high temperature to form a highly stable and reliable connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic structural diagram of a six-dimensional force sensor based on a planar semiconductor process provided by an embodiment of the present invention.

[0020] Figure 2 It is a strain analysis cloud diagram of a six-dimensional force sensor based on a planar semiconductor process provided by an embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of strain gauge distribution in a six-dimensional force sensor based on planar semiconductor technology provided by an embodiment of the present invention.

[0022] Figure 4 This is a diagram of a strain gauge resistor group bridge in a six-dimensional force sensor based on a planar semiconductor process provided by an embodiment of the present invention.

[0023] The reference numerals in the figures are: 1. Buffer beam; 2. Center bearing platform; 3. Elastic beam; 4. Shell. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly located on the other element or indirectly located on the other element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element.

[0026] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention, and do not indicate that a device or element must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0027] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating relative importance or indicating the number of technical features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The specific implementation of the present invention is described in more detail below in conjunction with specific embodiments: like Figure 1 As shown, an embodiment of the present invention provides a six-dimensional force sensor based on a planar semiconductor process, including a central bearing platform 2, a housing 4, an elastic beam 3 and a buffer beam 1; one end of the elastic beam 3 is connected to the central bearing platform 2, the other end of the elastic beam 3 is connected to the buffer beam 1, the buffer beam 1 is arranged orthogonally to the elastic beam 3, and the end of the buffer beam 1 away from the elastic beam 3 is connected to the housing 4; wherein, six groups of strain gauges are arranged on the surface of the elastic beam 3 and the buffer beam 1, each group of strain gauges forms an independent Wheatstone full bridge circuit, and the six groups of strain gauges are respectively used to measure the forces in the three directions of Fx, Fy, and Fz and the moments in the three directions of Mx, My, and Mz. Specifically, the elastic beam 3 is used to bear external forces, and the strain of each group of strain gauges changes, bends when subjected to force, and transmits the force to each group of strain gauges; the stiffness and geometric shape of the elastic beam 3 can also be adjusted to achieve measurement of different force ranges. The buffer beam 1 is used as an elastic support to reduce coupling between beams and improve measurement sensitivity.

[0028] In one embodiment, it also includes a signal acquisition module and a terminal, the six groups of Wheatstone full-bridge circuits are electrically connected to the input end of the signal acquisition module respectively, and the output end of the signal acquisition module is electrically connected to the terminal.

[0029] In one of the embodiments, the terminal uses a least squares linear matrix decoupling based on multiple load steps.

[0030] In one embodiment, the strain gauge is a semiconductor silicon strain gauge, specifically a P-type doped silicon strain gauge.

[0031] In one embodiment, six sets of strain gauges are arranged on the upper and lower surfaces of the elastic beam and the buffer beam, avoiding the side position arrangement, avoiding the operational difficulties caused by side mounting and side wall lead binding, simplifying the operational difficulty, and reducing the process cost.

[0032] In one embodiment, each set of strain gauges includes four strain gauges.

[0033] In one of the embodiments, the strain gauge is attached and fixed to the surface of the elastic beam and the buffer beam by means of a resin material, and a high-stability and high-reliability connection is formed by high-temperature curing.

[0034] like Figure 2 As shown, according to the stress distribution cloud diagram analysis on the elastic beam and the buffer beam on the six-dimensional force sensor, the maximum stress distribution position under the uniaxial load is accurately located, thereby determining the corresponding strain gauge placement point of each set of strain gauges. Figure 3 As shown, 24 strain gauges are arranged on the surface of the elastic beam and the buffer beam (the 24 strain gauges are FxR1, FxR2, FxR3, FxR4, FyR1, FyR2, FyR3, FyR4, FzR1, FzR2, FzR3, FzR4, MxR1, MxR2, MxR3, MxR4, MyR1, MyR2, MyR3, MyR4, MzR1, MzR2, MzR3, MzR4) and the strain gauges are attached to the upper and lower surfaces of the elastic beam and the buffer beam through resin material, and are cured at high temperature to form a highly stable and reliable connection.

[0035] Preferably, the strain gauge is a semiconductor silicon strain gauge, such as Figure 4 As shown, each set of strain gauges forms an independent Wheatstone full bridge circuit, and there are 6 sets of full bridge circuits in total. The 6 sets of Wheatstone full bridge circuits are respectively connected to the input end of the signal acquisition module, and the output end of the signal acquisition module is connected to the terminal.

[0036] Preferably, the embodiment of the present invention adopts a least squares linear matrix decoupling based on multi-load steps. Assuming that all input and output values ​​are linear, each set of data consists of input values ​​and their corresponding output values ​​in six dimensions, and a multi-load step method is used to calibrate the six-dimensional force sensor in a single-axis static manner. Each calibration only applies a force / torque load in a single-axis direction, and the number of calibrations is much greater than the number of dimensions. The force / torque load vector is , , , , , ,……, … .

[0037] The static calibration input force matrix is ​​as follows: ; The corresponding output voltage matrix is ​​obtained through multi-load step single-axis static calibration, and then the least square method is used for decoupling fitting. Finally, the decoupling is performed by solving the inverse matrix of the calibration matrix. The decoupling accuracy of this method can reach less than 2%. The calibration matrix A obtained by solving is as follows: ; This embodiment adopts a least squares linear matrix decoupling based on multiple load steps. By fitting the linear relationship between input and output, it can minimize inter-dimensional crosstalk and improve decoupling accuracy, so that the inter-dimensional coupling error of the six-dimensional force sensor is reduced to less than 2%.

[0038] An embodiment of the present invention further provides a method for preparing a six-dimensional force sensor based on a planar semiconductor process according to any one of the above embodiments, comprising the following steps: preparing and connecting a central bearing platform, a housing, an elastic beam and a buffer beam; Each set of strain gauges is attached to the upper and lower surfaces of the elastic beam and the buffer beam through a resin material; High temperature curing, fixing each set of strain gauges to the elastic beam and the buffer beam; Lead welding is performed to electrically connect each set of strain gauges to form an independent Wheatstone full-bridge circuit to obtain a six-dimensional force sensor; Carry out sealing and finished product inspection on six-axis force sensors; Conduct finished product performance test on the six-dimensional force sensor; After the finished product performance test is passed, the six-dimensional force sensor is packaged.

[0039] In one embodiment, the method for preparing the strain gauge comprises the following steps: Clean the silicon wafer using the standard RCA (Root Cause Analysis) process; Make masks, prepare substrate glue, and shape substrate; Spin-coat photoresist on the silicon wafer, use a mask to photolithographically form a sensitive piezoresistor pattern, and obtain a strain gauge resistance pattern; Etch the silicon wafer, remove the photoresist, and quickly anneal at 350°C to obtain the strain gauge; the purpose of annealing is to eliminate lattice defects; Conduct resistance test on strain gauge resistors; The resistance film of the strain gauge is engraved using a laser process to adjust the resistance value of the strain gauge.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A six-dimensional force sensor based on planar semiconductor technology, characterized in that: The invention comprises a central bearing platform, a shell, an elastic beam and a buffer beam; one end of the elastic beam is connected to the central bearing platform, the other end of the elastic beam is connected to the buffer beam, the buffer beam is arranged orthogonally to the elastic beam, and the end of the buffer beam away from the elastic beam is connected to the shell; Among them, six groups of strain gauges are arranged on the surface of the elastic beam and the buffer beam, each group of the strain gauges forms an independent Wheatstone full-bridge circuit, and the six groups of strain gauges are respectively used to measure the forces in the three directions of Fx, Fy, and Fz and the moments in the three directions of Mx, My, and Mz.

2. The six-dimensional force sensor based on planar semiconductor technology as claimed in claim 1, characterized in that: It also includes a signal acquisition module and a terminal. The six groups of Wheatstone full-bridge circuits are electrically connected to the input end of the signal acquisition module respectively, and the output end of the signal acquisition module is electrically connected to the terminal.

3. The six-dimensional force sensor based on planar semiconductor technology as claimed in claim 2, characterized in that: The terminal adopts least squares linear matrix decoupling based on multiple load steps.

4. The six-dimensional force sensor based on planar semiconductor technology as claimed in claim 1, characterized in that: The strain gauge is a semiconductor silicon strain gauge.

5. The six-dimensional force sensor based on planar semiconductor technology as claimed in claim 1, characterized in that: The six groups of strain gauges are arranged on the upper and lower surfaces of the elastic beam and the buffer beam.

6. The six-dimensional force sensor based on planar semiconductor technology as claimed in claim 1, characterized in that: Each group of strain gauges includes four strain gauges.

7. The six-dimensional force sensor based on planar semiconductor technology as claimed in claim 6, characterized in that: The strain gauge is attached and fixed to the surfaces of the elastic beam and the buffer beam through a resin material.

8. A method for preparing a six-dimensional force sensor based on a planar semiconductor process as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Prepare and connect the central bearing platform, the housing, the elastic beam and the buffer beam; Adhere each set of strain gauges to the upper and lower surfaces of the elastic beam and the buffer beam through a resin material; High temperature curing to fix each set of strain gauges to the elastic beam and the buffer beam; Lead welding is performed to electrically connect each set of strain gauges to form an independent Wheatstone full-bridge circuit to obtain a six-dimensional force sensor; Performing sealing and finished product inspection on the six-dimensional force sensor; Conducting finished product performance testing on the six-dimensional force sensor; After the finished product performance test is qualified, the six-dimensional force sensor is packaged.

9. The preparation method according to claim 8, characterized in that: The method for preparing the strain gauge comprises the following steps: The silicon wafers are cleaned by the standard RCA process; Make masks, prepare substrate glue, and shape substrate; Spin-coat photoresist on the silicon wafer, use a mask to photolithographically form a sensitive piezoresistor pattern, and obtain a strain gauge resistance pattern; etching the silicon wafer to remove the photoresist, and rapidly annealing at 350° C. to obtain a strain gauge; Conduct resistance test on strain gauge resistors; The resistance film of the strain gauge is engraved by laser technology to adjust the resistance value of the strain gauge.

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