In-situ calibration device and method for micro-scale silicon-based stress sensor

Abstract

The invention discloses an in-situ calibration device and method for a micro-scale silicon-based stress sensor. The device comprises a four-point bending loading structure, a force loading control unit, a micro-scale silicon-based stress sensor calibration structure, a bridge test unit and an upper computer control system, a miniature four-point bending loading structure and an in-situ calibration structure containing a stress sensor are combined, and the in-situ calibration structure utilizes a signal fan-out flexible printed board to carry out signal extraction, so that the sensitivity coefficient of the micro-scale silicon-based stress sensor is calibrated, namely, the relation that the output voltage of the stress sensor changes along with stress is obtained. According to the invention, accurate calibration of the micro-scale silicon-based stress sensor can be realized, and the stress transmission error in the calibration process is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ calibration of stress sensors, and in particular to an in-situ calibration device and method for microscale silicon-based stress sensors. Background Art

[0002] In the context of the development of autonomous driving, electrification and the Internet of Everything, the miniaturization, shortened time to market and enhanced functionality of electronic devices and systems have brought new reliability challenges. Using integrated micro-scale silicon-based stress sensors to obtain stress state data inside electronic devices and systems, and relying on these stress data to carry out fault location, health monitoring and life prediction is a key technical means to support the solution of reliability problems.

[0003] There is little research on microscale silicon-based stress sensors in the prior art, and there is no specific calibration method or device. For traditional stress sensors, a four-point bending test structure is used for calibration. The sensor is bonded to the surface of a standard test structure (stainless steel, aluminum alloy, etc.). When different force loads are applied, the sensor and the standard test structure deform at the same time. The strain sensor signal is led out using a wire, and the electrical signal is collected through external test equipment to achieve calibration testing of the stress sensor. For microscale silicon-based stress sensors, the above calibration structures cannot achieve calibration testing. The main reasons include:

[0004] (1) Microscale silicon-based stress sensors are integrated inside electronic devices and systems, and it is impossible to calibrate electronic devices and systems containing stress sensors (there is a large transmission error when applying stress loads by bonding them to a standard test structure, and it cannot be quantified); (2) Microscale silicon-based stress sensors are small in size and hard, and it is difficult to bond the stress sensors to the surface of a standard calibration structure for calibration; (3) Microscale silicon-based stress sensor signals are difficult to extract, and there is a large fluctuation when extracting them using the existing probe method, resulting in a large calibration error.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] The technical problem to be solved by the present invention is that the existing calibration method and device of stress sensors are not suitable for micro-scale silicon-based stress sensors, which will cause large calibration errors of micro-scale silicon-based stress sensors. The purpose of the present invention is to provide an in-situ calibration device and method for micro-scale silicon-based stress sensors. The present invention combines a micro four-point bending loading structure and an in-situ calibration structure containing a stress sensor, and the in-situ calibration structure uses a signal fan-out flexible printed circuit board to lead out signals, so as to calibrate the sensitivity coefficient of the micro-scale silicon-based stress sensor, that is, to obtain the relationship between the output voltage of the stress sensor and the stress change. The present invention can realize the precise calibration of the micro-scale silicon-based stress sensor and reduce the stress transfer error during the calibration process.

[0007] The present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides an in-situ calibration device for a microscale silicon-based stress sensor, the device comprising:

[0009] The four-point bending loading structure is used to clamp the micro-scale silicon-based stress sensor calibration structure to generate horizontal stress, and also measures the force load applied to the micro-scale silicon-based stress sensor calibration structure through a force sensor; and feeds back the horizontal stress and force load to the force loading control unit;

[0010] The force loading control unit is used to calculate the horizontal stress and force load according to the feedback from the four-point bending loading structure, and adjust the displacement of the lower support in the four-point bending loading structure through closed-loop feedback so that the measured force load reaches the set value after adjustment;

[0011] A microscale silicon-based stress sensor calibration structure is used for sensitivity calibration of the microscale silicon-based stress sensor. The signal interconnection of the microscale silicon-based stress sensor on the calibration structure is led out to the flexible printed board, and then the flexible printed board is connected to the bridge test unit.

[0012] The bridge test unit is used to measure the output voltage of the microscale silicon-based stress sensor, correspond to the applied horizontal stress, draw the image of stress and output voltage and perform linear fitting to obtain the sensitivity coefficient;

[0013] The host computer control system is used to control the force loading control unit and the bridge test unit, control the force loading control unit to apply the set horizontal stress, and control the bridge test unit to measure the output voltage of the micro-scale silicon-based stress sensor when the horizontal stress is applied stably.

[0014] Further, the four-point bending loading structure includes two lower supports and two upper supports, and the horizontal positions of the upper supports and the lower supports can be adjusted independently to match the positions of the required calibration force sensors;

[0015] When in use, the microscale silicon-based stress sensor calibration structure is placed in the slots of the two lower supports, and the vertical position of the upper support is fixed. The lower support moves vertically upward. When the lower support moves to the vicinity of the upper support position, the microscale silicon-based stress sensor calibration structure is clamped by the upper and lower supports to generate horizontal stress.

[0016] Further, a microscale silicon-based stress sensor is arranged at the center of the microscale silicon-based stress sensor calibration structure;

[0017] It also includes a flexible printed board, which is hollowed out in the center. The flexible printed board is pasted on the surface of the micro-scale silicon-based stress sensor calibration structure and the corresponding micro-scale silicon-based stress sensor protrudes through the hollow part. The signal of the micro-scale silicon-based stress sensor is interconnected and led out to the flexible printed board by gold wire bonding.

[0018] Furthermore, the microscale silicon-based stress sensor calibration structure is a rectangular strip calibration structure formed by cutting a silicon wafer.

[0019] Furthermore, the rectangular strip calibration structure has a length ranging from 50 mm to 100 mm, a width ranging from 5 mm to 10 mm, and a thickness ranging from 0.1 mm to 1 mm.

[0020] Furthermore, the number of the microscale silicon-based stress sensors is one or more.

[0021] Furthermore, the microscale silicon-based stress sensor Pad is bonded to the flexible printed circuit board pad through gold wire bonding to lead the signal of the microscale silicon-based stress sensor to the flexible printed circuit board.

[0022] In a second aspect, the present invention further provides an in-situ calibration method for a microscale silicon-based stress sensor, which is applied to the above-mentioned in-situ calibration device for a microscale silicon-based stress sensor; the method comprises:

[0023] Step 1, preparing a microscale silicon-based stress sensor calibration structure, including one or more microscale silicon-based stress sensors at the center of the microscale silicon-based stress sensor calibration structure, bonding the designed hollow flexible printed circuit board to the microscale silicon-based stress sensor calibration structure, and then interconnecting and leading the signal of the microscale silicon-based stress sensor to the flexible printed circuit board by gold wire bonding;

[0024] Step 2, adjusting the positions of the upper support and the lower support of the four-point bending loading structure, placing the microscale silicon-based stress sensor calibration structure on the lower support, and adjusting the position of the microscale silicon-based stress sensor calibration structure so that the microscale silicon-based stress sensor at its center is between the two lower supports;

[0025] Step 3, connecting the flexible printed circuit board to the bridge test unit, connecting the four-point bending loading structure to the force loading control unit, and simultaneously connecting the bridge test unit and the force loading control unit to the host computer control system respectively;

[0026] Step 4: After completing the connection of each unit, the initial output voltage of the microscale silicon-based stress sensor is measured when no stress is applied. After the test is completed, the value of each loading force is set by the host computer control system. After the loading is completed, the output voltage of the microscale silicon-based stress sensor is tested. After the test is completed, the force loading is cancelled so that the sensor returns to its initial state.

[0027] Step 5, according to the four-point bending stress calculation method, the stress on the surface of the microscale silicon-based stress sensor calibration structure is obtained by using the size of the loaded force and the length, width and thickness parameters of the microscale silicon-based stress sensor calibration structure, and a curve of the stress value under the stress load and the output voltage of the stress sensor is drawn. The slope is obtained by linear fitting, and the slope is the sensitivity coefficient of the microscale silicon-based stress sensor.

[0028] Furthermore, the formula for the four-point bending stress calculation method is:

[0029]

[0030] Wherein, σ is the stress of the stress sensor at the calibration structure to be calculated; F is the applied force load, which is measured by the force sensor, where the force sensor is inside the force loading unit and is different from the microscale silicon-based stress sensor;

[0031] L and d are the parameters of the four-point bending loading structure, t and h are the geometric parameters of the microscale silicon-based stress sensor calibration structure, L is the distance between the two upper supports in the four-point bending loading structure, d is the distance between the two lower supports in the four-point bending loading structure, t is the thickness of the microscale silicon-based stress sensor calibration structure, and h is the width of the microscale silicon-based stress sensor calibration structure.

[0032] Furthermore, the microscale silicon-based stress sensor calibration structure prepared in step 1 has a length of 90 mm, a width of 5.4 mm, and a thickness of 0.72 mm.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] 1. The present invention provides an in-situ calibration device and method for a microscale silicon-based stress sensor. The present invention combines a micro four-point bending loading structure and an in-situ calibration structure containing a stress sensor, and the in-situ calibration structure uses a signal fan-out flexible printed circuit board to lead out signals, thereby realizing the calibration of the sensitivity coefficient of the microscale silicon-based stress sensor, that is, obtaining the relationship between the output voltage of the stress sensor and the stress change. The present invention can realize the precise calibration of the microscale silicon-based stress sensor and reduce the stress transfer error during the calibration process.

[0035] 2. The present invention takes into account the small size of the microscale silicon-based stress sensor. The existing signal extraction method often uses a probe. Then, after the force load is applied, the signal extraction using the probe will cause load fluctuations, resulting in a large calibration error. Therefore, the present invention uses a flexible plate gold wire bonding method to extract the signal, which can not only ensure the stability of the signal, but also avoid the error of the stress load due to the large deformation characteristics of the flexible plate, thereby ensuring the measurement accuracy.

[0036] 3. The present invention is mainly aimed at stress sensors. Considering that the principle of stress sensors is based on the semiconductor piezoresistive effect, stress directly causes the sensor resistance to change, thereby affecting the change of the bridge voltage. In order to calibrate the stress sensor, it is necessary to use a four-point bending loading structure to apply a single-direction stress load (which cannot be achieved on a cantilever beam platform). BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0038] Figure 1 This is a schematic diagram of an in-situ calibration device for a micro-scale silicon-based stress sensor of the present invention;

[0039] Figure 2 A three-dimensional model diagram of an in-situ calibration device for a micro-scale silicon-based stress sensor of the present invention;

[0040] Figure 3 This is a front view of a three-dimensional model of an in-situ calibration device for a micro-scale silicon-based stress sensor of the present invention;

[0041] Figure 4 A top view of a three-dimensional model of an in-situ calibration device for a micro-scale silicon-based stress sensor of the present invention;

[0042] Figure 5 This is a schematic diagram of the calibration structure of the microscale silicon-based stress sensor of the present invention;

[0043] Figure 6 It is a schematic diagram of the calibration results of the stress sensor of the present invention.

[0044] Reference numerals and corresponding component names:

[0045] 1-four-point bending loading structure, 2-force loading control unit, 3-microscale silicon-based stress sensor calibration structure, 4-bridge test unit, 5-upper computer control system, 11-lower support, 12-upper support, 31-microscale silicon-based stress sensor, 32-flexible printed circuit board. DETAILED DESCRIPTION

[0046] Hereinafter, the term "include" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0047] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0048] The expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify the various constituent elements in various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing an element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0049] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0050] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0051] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0052] However, the existing calibration methods and devices for stress sensors are not suitable for microscale silicon-based stress sensors, which may cause large calibration errors of microscale silicon-based stress sensors. The present invention designs an in-situ calibration device and method for microscale silicon-based stress sensors. The present invention combines a micro four-point bending loading structure and an in-situ calibration structure containing a stress sensor, and the in-situ calibration structure uses a signal fan-out flexible printed circuit board to lead out signals, thereby calibrating the sensitivity coefficient of the microscale silicon-based stress sensor, that is, obtaining the relationship between the output voltage of the stress sensor and the stress change. The present invention can achieve accurate calibration of microscale silicon-based stress sensors and reduce stress transfer errors during the calibration process.

[0053] In particular, the present invention takes into account the small size of the microscale silicon-based stress sensor. The existing signal extraction method often uses a probe. Then, after the force load is applied, the signal extraction using the probe will cause load fluctuations, resulting in a large calibration error. Therefore, the present invention uses a flexible plate gold wire bonding method to extract the signal, which can not only ensure the stability of the signal, but also avoid the error of the stress load due to the large deformation characteristics of the flexible plate, thereby ensuring the measurement accuracy.

[0054] At the same time, unlike strain sensors, the present invention is mainly aimed at stress sensors. Considering that the principle of stress sensors is based on the semiconductor piezoresistive effect, stress directly causes the sensor resistance to change, thereby affecting the change of the bridge voltage. In order to calibrate the stress sensor, it is necessary to use a four-point bending loading structure to apply a single-direction stress load (which cannot be achieved on a cantilever beam platform).

[0055] Among them, the microscale silicon-based stress sensor targeted by the present invention is a stress sensor prepared on the surface of a silicon wafer using the semiconductor piezoresistive effect, including two types of stress sensors, one is an x-direction stress sensor sensitive to stress in the x-direction, and the other is a y-direction stress sensor sensitive to stress in the y-direction, and its sensitive gate size is about 150μm×150μm.

[0056] Example 1

[0057] like Figure 1 As shown, the present invention is an in-situ calibration device for micro-scale silicon-based stress sensors. The present invention mainly calibrates the sensitivity coefficient (single-direction stress-output voltage change relationship) of the developed micro-scale silicon-based stress sensor. The device includes:

[0058] The four-point bending loading structure 1 is used to clamp the micro-scale silicon-based stress sensor calibration structure 3 to generate horizontal stress, and also measure the force load applied to the micro-scale silicon-based stress sensor calibration structure 3 through a force sensor; and feed back the horizontal stress and force load to the force loading control unit 2;

[0059] The force loading control unit 2 is used to calculate the horizontal stress and force load fed back from the four-point bending loading structure 1, and adjust the displacement of the lower support in the four-point bending loading structure 1 through closed-loop feedback, so that the measured force load reaches the set value after adjustment;

[0060] A microscale silicon-based stress sensor calibration structure 3 is used for sensitivity calibration of the microscale silicon-based stress sensor, and the signal interconnection of the microscale silicon-based stress sensor on the calibration structure is led out to the flexible printed board, and then the flexible printed board is connected to the bridge test unit 4;

[0061] The bridge test unit 4 is used to measure the output voltage of the micro-scale silicon-based stress sensor, correspond to the applied horizontal stress, draw an image of the stress and the output voltage and perform linear fitting to obtain the sensitivity coefficient;

[0062] The host computer control system 5 is used to control the force loading control unit 2 and the bridge test unit 4, control the force loading control unit 2 to apply the set horizontal stress, and control the bridge test unit 4 to measure the output voltage of the micro-scale silicon-based stress sensor when the horizontal stress is applied stably.

[0063] In this embodiment, the four-point bending loading structure 1 includes two lower supports 11 and two upper supports 12, and the horizontal positions of the upper supports 12 and the lower supports 11 can be adjusted independently to match the positions of the required calibration force sensors;

[0064] When in use, the microscale silicon-based stress sensor calibration structure 3 is placed in the slots of the two lower supports 11, and the vertical position of the upper support 12 is fixed, and the lower support 11 moves vertically upward. When the lower support 11 moves to the vicinity of the position of the upper support 12, the microscale silicon-based stress sensor calibration structure 3 is clamped by the upper support 12 and the lower support 11, generating horizontal stress;

[0065] In addition, the four-point bending loading structure 1 also includes a force sensor, which is used to measure the force load applied to the microscale silicon-based stress sensor calibration structure 3. The force load and the above horizontal stress are fed back to the force loading control unit 2 for closed-loop feedback adjustment, and the set force load value is reached after adjustment.

[0066] In this embodiment, the microscale silicon-based stress sensor calibration structure 3 is a rectangular strip calibration structure (silicon strip structure) formed by cutting a silicon wafer, and the microscale silicon-based stress sensor calibration structure 3 includes a flexible printed circuit board 32 for signal fan-out, and one or more microscale silicon-based stress sensors 31 are arranged at the center of the microscale silicon-based stress sensor calibration structure 3;

[0067] Specifically, the flexible printed circuit board 32 is hollowed out in the center. The flexible printed circuit board 32 is pasted on the surface of the microscale silicon-based stress sensor calibration structure 3 and protrudes through the hollow part to correspond to the microscale silicon-based stress sensor 31, that is, the flexible printed circuit board 32 is prevented from covering the microscale silicon-based stress sensor 31 in the center of the silicon strip; the outer ring of the flexible board can be bonded to the silicon strip to ensure that the microscale silicon-based stress sensor Pad and the flexible printed circuit board pad can be gold-wire bonded, and the signal of the microscale silicon-based stress sensor 31 is interconnected and led out to the flexible printed circuit board 32 by gold-wire bonding.

[0068] In this embodiment, the rectangular strip calibration structure has a length range of 50 mm to 100 mm, a width range of 5 mm to 10 mm, and a thickness range of 0.1 mm to 1 mm. In specific implementation, the length is 90 mm, the width is 5.4 mm, and the thickness is 0.72 mm.

[0069] When the present invention is implemented, Figure 6 As shown, Figure 6 is the calibration result of the stress sensor (the output voltage signal of the sensor under different stresses can be obtained), Figure 6 The horizontal axis is the stress value calculated by the formula, Figure 6 The vertical axis is the output voltage value of the microscale silicon-based stress sensor.

[0070] The key points of the present invention are: (1) the calibration of the microscale silicon-based stress sensor is carried out by preparing a corresponding calibration structure (rectangular strips cut from silicon wafers + flexible printed circuit boards), thereby avoiding the error caused by the probe lead-out signal. At the same time, due to the characteristics of the flexible printed circuit board, the stress transfer error during the calibration process is reduced; (2) the designed four-point bending loading structure can match smaller rectangular strips (length 50mm to 100mm, width 5mm to 10mm, thickness 0.1mm to 1mm), and provide uniaxial stress for the calibration structure. The force loading control unit can realize precise control of the force load with a control accuracy of 0.01N.

[0071] Example 2

[0072] The difference between this embodiment and embodiment 1 is that this embodiment provides an in-situ calibration method for a microscale silicon-based stress sensor, which is applied to an in-situ calibration device for a microscale silicon-based stress sensor in embodiment 1; the method comprises:

[0073] Step 1, prepare a microscale silicon-based stress sensor calibration structure 3, for example, prepare a rectangular strip calibration structure with a length of 90 mm, a width of 5.4 mm, and a thickness of 0.72 mm; include one or more microscale silicon-based stress sensors 31 at the center of the microscale silicon-based stress sensor calibration structure 3, bond the designed hollow flexible printed circuit board 32 to the microscale silicon-based stress sensor calibration structure 3, and then interconnect the signal of the microscale silicon-based stress sensor 31 to the flexible printed circuit board by gold wire bonding;

[0074] Step 2, adjusting the positions of the upper support 12 and the lower support 11 of the four-point bending loading structure 1, for example, setting the distance between the two lower supports to 40 mm, and the distance between the two upper supports to 70 mm, placing the microscale silicon-based stress sensor calibration structure 3 on the lower support 11, and adjusting the position of the microscale silicon-based stress sensor calibration structure 3 so that the microscale silicon-based stress sensor 31 at its center is between the two lower supports 11;

[0075] Step 3, connecting the flexible printed circuit board 32 to the bridge test unit 4, connecting the four-point bending loading structure 1 to the force loading control unit 2, and simultaneously connecting the bridge test unit 4 and the force loading control unit 2 to the host computer control system 5 respectively;

[0076] Step 4, after completing the connection of each unit, the initial output voltage of the microscale silicon-based stress sensor 31 is measured when no stress is applied. After the test is completed, the upper computer control system 5 is used to set the loading force value to 0.5N. After the loading is completed, the output voltage test of the microscale silicon-based stress sensor 31 is performed. After the test is completed, the force loading is canceled to restore the sensor to its initial state. According to this method, the force loading of 1N, 1.5N, 2N, 2.5N and other forces and the sensor output voltage test are performed in sequence;

[0077] Step 5, according to the four-point bending stress calculation method, the stress on the surface of the microscale silicon-based stress sensor calibration structure 3 is obtained by using the size of the loaded force, the distance parameters between the upper support 12 and the lower support 11 of the four-point bending loading structure 1, and the length, width and thickness parameters of the microscale silicon-based stress sensor calibration structure 3, and a curve of the stress value under the stress load and the output voltage of the stress sensor is drawn. The slope is obtained by linear fitting, and the slope is the sensitivity coefficient of the microscale silicon-based stress sensor 31.

[0078] In this embodiment, the formula for calculating the four-point bending stress is:

[0079]

[0080] Wherein, σ is the stress of the stress sensor at the calibration structure to be calculated; F is the applied force load, which is measured by the force sensor, where the force sensor is inside the force loading unit and is different from the microscale silicon-based stress sensor;

[0081] L and d are parameters of the four-point bending loading structure, t and h are geometric parameters of the microscale silicon-based stress sensor calibration structure, L is the distance between the two upper supports in the four-point bending loading structure, d is the distance between the two lower supports in the four-point bending loading structure, t is the thickness of the microscale silicon-based stress sensor calibration structure 3, and h is the width of the microscale silicon-based stress sensor calibration structure 3.

[0082] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An in-situ calibration device for microscale silicon-based stress sensors, characterized in that: The device includes: A four-point bending loading structure (1) is used to clamp a micro-scale silicon-based stress sensor calibration structure (3) to generate horizontal stress, and also to measure the force load applied to the micro-scale silicon-based stress sensor calibration structure (3) through a force sensor; and to feed back the horizontal stress and the force load to a force loading control unit (2); A force loading control unit (2) is used to calculate the horizontal stress and force load fed back from the four-point bending loading structure (1), and to adjust the displacement of the lower support in the four-point bending loading structure (1) through closed-loop feedback so that the measured force load reaches a set value after adjustment; A microscale silicon-based stress sensor calibration structure (3) is used for sensitivity calibration of the microscale silicon-based stress sensor, and the signal interconnection of the microscale silicon-based stress sensor on the calibration structure is led out to a flexible printed board, and the flexible printed board is then connected to a bridge test unit (4); The bridge test unit (4) is used to measure the output voltage of the micro-scale silicon-based stress sensor, correspond to the applied horizontal stress, draw an image of the stress and the output voltage and perform linear fitting to obtain a sensitivity coefficient; The upper computer control system (5) is used to control the force loading control unit (2) and the bridge test unit (4), control the force loading control unit (2) to apply the set horizontal stress, and control the bridge test unit (4) to measure the output voltage of the micro-scale silicon-based stress sensor when the horizontal stress is applied stably.

2. The in-situ calibration device for microscale silicon-based stress sensors according to claim 1, characterized in that: The four-point bending loading structure (1) comprises two lower supports (11) and two upper supports (12), and the horizontal positions of the upper supports (12) and the lower supports (11) can be adjusted independently to match the positions of the required calibration force sensors; When in use, the microscale silicon-based stress sensor calibration structure (3) is placed in the slots of the two lower supports (11), and the vertical position of the upper support (12) is fixed. The lower support (11) moves vertically upward. When the lower support (11) moves to the vicinity of the position of the upper support (12), the microscale silicon-based stress sensor calibration structure (3) is clamped by the upper support (12) and the lower support (11), generating horizontal stress.

3. The in-situ calibration device for microscale silicon-based stress sensors according to claim 1, characterized in that: A microscale silicon-based stress sensor (31) is arranged at the center of the microscale silicon-based stress sensor calibration structure (3); It also includes a flexible printed board (32), the flexible printed board (32) is hollowed out at the center, the flexible printed board (32) is adhered to the surface of the microscale silicon-based stress sensor calibration structure (3) and a corresponding microscale silicon-based stress sensor (31) is protruded through the hollowed-out part, and the signal of the microscale silicon-based stress sensor (31) is interconnected and led out to the flexible printed board (32) by means of gold wire bonding.

4. The in-situ calibration device for microscale silicon-based stress sensors according to claim 3, characterized in that: The microscale silicon-based stress sensor calibration structure (3) is a rectangular strip-shaped calibration structure formed by cutting a silicon wafer.

5. The in-situ calibration device for microscale silicon-based stress sensors according to claim 4, characterized in that: The rectangular strip calibration structure has a length ranging from 50 mm to 100 mm, a width ranging from 5 mm to 10 mm, and a thickness ranging from 0.1 mm to 1 mm.

6. The in-situ calibration device for microscale silicon-based stress sensors according to claim 3, characterized in that: The number of the microscale silicon-based stress sensors (31) is one or more.

7. The in-situ calibration device for microscale silicon-based stress sensors according to claim 3, characterized in that: The microscale silicon-based stress sensor Pad is bonded to the flexible printed circuit board pad via gold wires, so as to lead the signal of the microscale silicon-based stress sensor (31) to the flexible printed circuit board (32).

8. An in-situ calibration method for microscale silicon-based stress sensors, characterized in that: The method is applied to an in-situ calibration device for a microscale silicon-based stress sensor as claimed in any one of claims 1 to 7; the method comprises: Step 1, preparing a microscale silicon-based stress sensor calibration structure (3), including one or more microscale silicon-based stress sensors (31) at the center of the microscale silicon-based stress sensor calibration structure (3), bonding the designed hollow flexible printed circuit board (32) to the microscale silicon-based stress sensor calibration structure (3), and then interconnecting and leading the signal of the microscale silicon-based stress sensor (31) to the flexible printed circuit board by gold wire bonding; Step 2, adjusting the positions of the upper support (12) and the lower support (11) of the four-point bending loading structure (1), placing the microscale silicon-based stress sensor calibration structure (3) on the lower support (11), and adjusting the position of the microscale silicon-based stress sensor calibration structure (3) so that the microscale silicon-based stress sensor (31) at its center is located between the two lower supports (11); Step 3, connecting the flexible printed circuit board (32) to the bridge test unit (4), connecting the four-point bending loading structure (1) to the force loading control unit (2), and simultaneously connecting the bridge test unit (4) and the force loading control unit (2) to the host computer control system (5) respectively; Step 4, after completing the connection of each unit, the initial output voltage of the micro-scale silicon-based stress sensor (31) is tested when no stress is applied. After the test is completed, the value of each loading force is set using the host computer control system (5). After the loading is completed, the output voltage test of the micro-scale silicon-based stress sensor (31) is performed. After the test is completed, the force loading is cancelled so that the sensor returns to its initial state; Step 5, according to the four-point bending stress calculation method, the stress on the surface of the microscale silicon-based stress sensor calibration structure (3) is obtained by using the size of the loaded force and the parameters of the microscale silicon-based stress sensor calibration structure (3), and a curve of the stress value under the stress load and the output voltage of the stress sensor is drawn. The slope is obtained by linear fitting, and the slope is the sensitivity coefficient of the microscale silicon-based stress sensor (31).

9. The in-situ calibration method for microscale silicon-based stress sensors according to claim 8, characterized in that: The formula for the four-point bending stress calculation method is: Wherein, σ is the stress of the stress sensor at the calibration structure to be calculated; F is the applied force load, which is obtained by measuring the force sensor; L and d are the parameters of the four-point bending loading structure, t and h are the geometric parameters of the microscale silicon-based stress sensor calibration structure (3), L is the distance between the two upper supports in the four-point bending loading structure, d is the distance between the two lower supports in the four-point bending loading structure, t is the thickness of the microscale silicon-based stress sensor calibration structure (3), and h is the width of the microscale silicon-based stress sensor calibration structure (3).

10. The in-situ calibration method for microscale silicon-based stress sensors according to claim 8, characterized in that: The microscale silicon-based stress sensor calibration structure (3) prepared in step 1 has a length of 90 mm, a width of 5.4 mm, and a thickness of 0.72 mm.

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