High-precision piezoresistive pressure sensor and design method

Abstract

The invention relates to the technical field of pressure sensors, in particular to a high-precision piezoresistive pressure sensor and a design method, and the sensor comprises a substrate which is provided with a sensitive film; four piezoresistors are arranged on the sensitive film, every two of the four piezoresistors are connected in series and then are connected in parallel to form a Wheatstone bridge, and the sensitivities of the four piezoresistors are equal. According to the piezoresistive pressure sensor, the sensitivities of the four piezoresistors are the same by adjusting the positions of the piezoresistors, so that the linearity of the piezoresistive pressure sensor is reduced, and when the sensitivities of the four piezoresistors are the same, the nonlinear error of the sensor is the lowest, so that the measurement precision of the finally designed piezoresistive pressure sensor is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and particularly relates to a high-precision piezoresistive pressure sensor and a design method thereof. Background Art

[0002] High-precision piezoresistive pressure sensors have important application values in the fields of aerospace, petrochemical industry, and industrial medical field. In the aerospace field, high-precision pressure sensors are used for pressure monitoring of aircraft, measurement of aviation atmospheric data systems, and ballistic analysis. Accurate pressure data ensures the flight safety and performance of aircraft. In the petrochemical industry, high-precision pressure sensors are used to monitor and control pressure conditions to ensure the safety and efficiency of the production process. In motor vehicles, high-precision pressure sensors are used to monitor engine pressure, tire pressure, etc. to ensure the driving performance and safety of the vehicle. In the medical field, high-precision pressure sensors are used to monitor physiological parameters such as the blood pressure and breathing pressure of patients to assist doctors in diagnosis and treatment. In industrial processes, high-precision pressure sensors are used to monitor and control pressure conditions to ensure the stability and efficiency of the control process. In environmental monitoring, high-precision pressure sensors are used for marine monitoring and meteorological observation to analyze and predict changes in the marine environment.

[0003] Because the piezoresistive effect requires the resistivity of longitudinal piezoresistors and transverse piezoresistors to change in opposite directions, the arrangement directions of longitudinal stress piezoresistors and transverse stress piezoresistors need to be consistent. However, the non-uniformity of the stress distribution on the thin film results in different sensitivities of the piezoresistors, thus reducing the linearity of the piezoresistive pressure sensor and leading to low measurement accuracy of the piezoresistive pressure sensor.

[0004] Therefore, it is necessary to provide a high-precision piezoresistive pressure sensor and a design method to solve the above problems. Summary of the Invention

[0005] In order to improve the measurement accuracy of the piezoresistive pressure sensor, the present invention provides a high-precision piezoresistive pressure sensor and a design method thereof, which solve the existing problems by adjusting the piezoresistors to make the sensitivities of all piezoresistors on the sensitive thin film equal.

[0006] A high-precision piezoresistive pressure sensor of the present invention adopts the following technical solutions, including: A substrate, on which a sensitive thin film is provided; And four piezoresistors, which are arranged on the sensitive thin film. Among them, the four piezoresistors are connected in series in pairs and then in parallel to form a Wheatstone bridge, and the sensitivities of all piezoresistors are equal.

[0007] Preferably, the stress area on the sensitive thin film is divided into two transverse stress concentration areas and two longitudinal stress concentration areas; Wherein, a piezoresistor is disposed in each of the transverse stress concentration region and the longitudinal stress concentration region, and the sensitivities of all the piezoresistors are equal; or a piezoresistor is disposed in each of the longitudinal stress concentration regions, and the other two piezoresistors are symmetrically disposed with respect to the center line of the sensitive film, and the sensitivities of all the piezoresistors are equal.

[0008] Preferably, when a piezoresistor is disposed in each of the transverse stress concentration region and the longitudinal stress concentration region, the piezoresistor in the transverse stress concentration region is disposed transversely at the maximum stress position of the transverse stress concentration region, the piezoresistor in the longitudinal stress concentration region is disposed longitudinally, and is disposed 5 μm away from the maximum stress position of the longitudinal stress concentration region towards the longitudinal edge of the sensitive film.

[0009] Preferably, when a piezoresistor is disposed in each of the longitudinal stress concentration regions and the other two piezoresistors are symmetrically disposed with respect to the center line of the sensitive film, among them, all four piezoresistors are disposed longitudinally, and the two piezoresistors in the longitudinal stress concentration region are disposed 28 μm away from the maximum stress position of the longitudinal stress concentration region towards the center direction of the sensitive film.

[0010] The design method of a high-precision piezoresistive pressure sensor of the present invention adopts the following technical solutions, including: Obtain the maximum stress positions corresponding to the transverse stress concentration region and the longitudinal stress concentration region; Coincide the center line of the piezoresistor with the maximum stress position; Take the direction from the edge of the sensitive film towards the center direction or from the center of the sensitive film towards the edge of the sensitive film as the moving direction, and move the position of the piezoresistor corresponding to the longitudinal stress concentration region multiple times; Obtain the nonlinear error after each movement, and take the position corresponding to the minimum nonlinear error as the optimal position of the piezoresistor corresponding to the longitudinal stress concentration region.

[0011] Preferably, the moving range when moving from the edge of the sensitive film towards the center direction is: 1 to 300 μm.

[0012] Preferably, the moving range when moving from the edge of the sensitive film towards the center direction is: 1 to 100 μm.

[0013] Preferably, the expression of the nonlinear error is:

[0014] In the formula, A is the area of the first transverse stress concentration region; x_A, y_A are the coordinates of the center of the piezoresistor in the first transverse stress concentration region on the sensitive film; is the sensitivity of the first piezoresistor in the first transverse stress concentration region; B is the area of the second transverse stress concentration region; x_B, y_B are the coordinates of the center of the piezoresistor in the second transverse stress concentration region on the sensitive film; is the sensitivity of the second piezoresistor in the second transverse stress concentration region; C is the area of the first longitudinal stress concentration region; x_C, y_C are the coordinates of the center of the piezoresistor in the first longitudinal stress concentration region on the sensitive film; is the sensitivity of the third piezoresistor in the first longitudinal stress concentration region; D is the area of the second longitudinal stress concentration region; x_D, y_D are the coordinates of the center of the piezoresistor in the second longitudinal stress concentration region on the sensitive film; is the sensitivity of the fourth piezoresistor in the second longitudinal stress concentration region; is the average sensitivity of all piezoresistors; is the maximum pressure at the piezoresistor measurement point, where the maximum pressures at the measurement points corresponding to the four piezoresistors are the same; is the piezoresistive coefficient; σ x is the sensitive film x stress in the direction of; σ y is the sensitive film y stress in the direction of.

[0015] The beneficial effects of the present invention are: By adjusting the positions of the piezoresistors on the sensitive film with non-uniform stress, the sensitivities of the four piezoresistors at different positions are made the same on the non-uniformly distributed sensitive film, that is, by adjusting the positions of the piezoresistors, the sensitivities of the four piezoresistors are made the same, thereby reducing the linearity of the piezoresistive pressure sensor, and when the sensitivities of the four piezoresistors are the same, the non-linear error of the sensor is the lowest. Therefore, the measurement accuracy of the finally designed piezoresistive pressure sensor is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 is a schematic structural diagram of Embodiment 1 of a high-precision piezoresistive pressure sensor of the present invention; Figure 2 is a schematic structural diagram of Embodiment 2 of a high-precision piezoresistive pressure sensor of the present invention; Figure 3 is a schematic diagram of the principle of the Wheatstone bridge in the embodiments of the present invention; Figure 4Trend diagram of the change in the non - linear error of the sensor when adjusting the position of the piezoresistor under the conditions of Embodiment 1 of the present invention; Figure 5 Trend diagram of the change in the non - linear error of the sensor when adjusting the position of the piezoresistor under the conditions of Embodiment 2 of the present invention; Figure 6 Trend diagram of the stress change on the center line of the sensitive film of the sensor with a boss - film structure in Embodiment 2 of the present invention.

[0018] In the figure: 1, sensitive film; 2, first transverse stress concentration area; 3, second longitudinal stress concentration area; 4, first piezoresistor; 5, third piezoresistor; 6, second piezoresistor; 7, fourth piezoresistor; 8, first longitudinal stress concentration area; 9, second transverse stress concentration area. Detailed implementation manners

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] An embodiment of a high - precision piezoresistive pressure sensor of the present invention includes: a substrate, on which a sensitive film 1 is provided; the side length of the sensitive film 1 is 2 mm, and four piezoresistors are provided on the sensitive film 1. Among them, the four piezoresistors are connected in series in pairs and then in parallel to form a Wheatstone bridge, and the sensitivities of the four piezoresistors are equal. It should be noted that making the sensitivities of the four piezoresistors equal is to improve the linearity (i.e., the lowest non - linearity), thereby improving the measurement accuracy of the piezoresistive pressure sensor.

[0021] Embodiment 1 Exemplarily, as Figure 1 shown, in order to ensure that the sensitivities of the four piezoresistors are equal, in this Embodiment 1, taking the flat - type sensitive film 1 as an example, the flat - type sensitive film 1 is arranged on the substrate, and the stress area of the flat - type sensitive film 1 is divided into two transverse stress concentration areas and two longitudinal stress concentration areas. Among them, one piezoresistor is arranged in each of the transverse stress concentration area and the longitudinal stress concentration area, and the sensitivities of all piezoresistors are equal.

[0022] Exemplarily, as Figure 1As shown, a first piezoresistor 4 along the transverse direction is provided in the first transverse stress concentration area 2, and a second piezoresistor 6 along the transverse direction is provided in the second transverse stress concentration area 9; a third piezoresistor 5 along the longitudinal direction is provided in the first longitudinal stress concentration area 8, and a fourth piezoresistor 7 along the longitudinal direction is provided in the second longitudinal stress concentration area 3. The first piezoresistor 4 is arranged at the maximum stress position of the first transverse stress concentration area 2, the second piezoresistor 6 is arranged at the maximum stress position of the second transverse stress concentration area 9, and the third piezoresistor 5 and the fourth piezoresistor 7 are offset 5 μm from the maximum stress position of the corresponding longitudinal stress concentration area towards the longitudinal edge of the sensitive film 1.

[0023] It should be noted that the first piezoresistor 4 and the second piezoresistor 6 are piezoresistors arranged transversely, that is, the first piezoresistor 4 and the second piezoresistor 6 are affected by transverse stress and have transverse sensitivity. The third piezoresistor 5 and the fourth piezoresistor 7 are piezoresistors arranged longitudinally, that is, the third piezoresistor 5 and the fourth piezoresistor 7 are affected by longitudinal stress and have longitudinal sensitivity. In this embodiment 2, the first piezoresistor 4 and the second piezoresistor 6 are fixed, and by adjusting the positions of the third piezoresistor 5 and the fourth piezoresistor 7 on the sensitive film 1 with non-uniform stress, the sensitivities of the third piezoresistor 5 and the fourth piezoresistor 7 are adjusted so that the sensitivities of the first piezoresistor 4, the second piezoresistor 6, the third piezoresistor 5 and the fourth piezoresistor 7 are equal, that is, as Figure 6 shown, it is defined that moving towards the center of the sensitive film 1 is negative and moving towards the longitudinal edge of the sensitive film 1 is positive. By moving the third piezoresistor 5 and the fourth piezoresistor 7, the linearity of the sensor at different positions of the third piezoresistor 5 and the fourth piezoresistor 7 as shown in Figure 3 is obtained. It can be seen from Figure 4 that when the third piezoresistor 5 and the fourth piezoresistor 7 are offset 5 μm towards the longitudinal edge of the corresponding sensitive film 1, the output non-linear error of the sensor is close to 0.001% FS, that is, at this time, the sensitivities of the first piezoresistor 4, the second piezoresistor 6, the third piezoresistor 5 and the fourth piezoresistor 7 are equal.

[0024] Embodiment 2 Exemplarily, as Figure 2 shown, in order to ensure that the sensitivities of the four piezoresistors are equal, in this embodiment 2, the sensitive film 1 with a boss structure is taken as an example, that is, the sensitive film 1 is arranged on the substrate through the boss structure, the boss structure is arranged at the center of the sensitive film 1, and boss stress concentration areas are also formed on the film around the boss structure. Among them, one piezoresistor is arranged in each longitudinal stress concentration area, and the other two piezoresistors are symmetrically arranged about the center line of the sensitive film 1 in the boss stress concentration area, and the sensitivities of all piezoresistors are equal.

[0025] Exemplarily, as Figure 2As shown in the figure, in Embodiment 2, the third piezoresistor 5 and the fourth piezoresistor 7 are arranged 28 μm away from the center of the sensitive film 1 along the maximum stress position of the corresponding longitudinal stress concentration area. The first piezoresistor 4 is arranged in the boss stress concentration area of the sensitive film 1 between the center of the sensitive film 1 and the third piezoresistor 5, and the second piezoresistor 6 is arranged in the boss stress concentration area of the sensitive film 1 between the center of the sensitive film 1 and the fourth piezoresistor 7. The first piezoresistor 4 and the second piezoresistor 6 are symmetric about the center line of the sensitive film 1. Among them, the first piezoresistor 4, the second piezoresistor 6, the third piezoresistor 5 and the fourth piezoresistor 7 are all arranged longitudinally, and the first piezoresistor 4 and the fourth piezoresistor 7 are in series, and the second resistor 6 and the third resistor 5.

[0026] It should be noted that in Embodiment 2, when only four longitudinally arranged piezoresistors are arranged on the sensitive film 1, that is, the first piezoresistor 4, the second piezoresistor 6, the third piezoresistor 5 and the fourth piezoresistor 7 are all arranged longitudinally. At this time, the positions of the first piezoresistor 4 and the second piezoresistor 6 remain fixed. By adjusting the positions of the third piezoresistor 5 and the fourth piezoresistor 7, that is, moving the third piezoresistor 5 and the fourth piezoresistor 7 inward or outward of the sensitive film 1 to adjust the nonlinear error of the sensor, the adjustment results are as follows Figure 5 As shown in the figure, from Figure 5 it can be seen that when the third piezoresistor 5 and the fourth piezoresistor 7 move 28 μm toward the middle of the sensitive film 1, the nonlinear error of the sensor is reduced to 0.001% FS. At this time, the sensitivities of the first piezoresistor 4, the second piezoresistor 6, the third piezoresistor 5 and the fourth piezoresistor 7 are equal.

[0027] An embodiment of a design method for a high-precision piezoresistive pressure sensor includes: Step 1, obtain the maximum stress positions corresponding to the transverse stress concentration area and the longitudinal stress concentration area; Step 2, arrange the center line of the piezoresistor to coincide with the maximum stress position; Step 3, use the direction from the edge of the sensitive film to the center or from the center of the sensitive film to the edge of the sensitive film as the moving direction, that is Figure 1 the E-E direction in the figure, move the position of the piezoresistor corresponding to the longitudinal stress concentration area multiple times; Step 4, obtain the nonlinear error after each movement, and use the position corresponding to the minimum nonlinear error as the optimal position of the piezoresistor corresponding to the longitudinal stress concentration area.

[0028] It should be noted that when the piezoresistor moves in the area of uneven stress concentration, the resistivity of the piezoresistor also changes. By adjusting the moving distance of the piezoresistor, the sensitivities of the four piezoresistors are made the same, which reduces the linearity. Among them, the stress distribution area of the transverse stress concentration area is smaller than that of the longitudinal stress concentration area, that is, the sensitivity of the transverse stress piezoresistor is lower. Therefore, the piezoresistor arranged in the transverse stress concentration area is arranged on the center line of the transverse stress concentration area and remains stationary. By adjusting the piezoresistor arranged on the longitudinal stress center line in the longitudinal stress concentration area to move 1-100 μm to the left (negative direction) or 1-300 μm to the right (positive direction), the sensitivity of the longitudinal stress piezoresistor on the sensitive film 1 is increased or decreased, so that the sensitivity of the piezoresistor in the longitudinal stress concentration area is the same as that of the piezoresistor in the transverse stress concentration area. When the sensitivities of the four piezoresistors are the same, the non-linear error of the sensor is the lowest.

[0029] On the premise that the piezoresistor in the transverse stress concentration area remains stationary, when the moving distance of the piezoresistor in the longitudinal stress concentration area changes within the range of -100 to 200 μm, the linearity of the output result of the Wheatstone bridge first decreases from 0.1% FS to 0% FS (zero) and then increases to 0.1% FS. When the non-linear error is reduced to zero, it is the optimal design result.

[0030] Exemplarily, the expression of the non-linear error is:

[0031] In the formula, A is the area of the first transverse stress concentration area; x_A, y_A are the coordinates of the center of the piezoresistor in the first transverse stress concentration area on the sensitive film; is the sensitivity of the first piezoresistor in the first transverse stress concentration area; B is the area of the second transverse stress concentration area; x_B, y_B are the coordinates of the center of the piezoresistor in the second transverse stress concentration area on the sensitive film; is the sensitivity of the second piezoresistor in the second transverse stress concentration area; C is the area of the first longitudinal stress concentration area; x_C, y_C are the coordinates of the center of the piezoresistor in the first longitudinal stress concentration area on the sensitive film; is the sensitivity of the third piezoresistor in the first longitudinal stress concentration area; D is the area of the second longitudinal stress concentration area; x_D, y_D are the coordinates of the center of the piezoresistor in the second longitudinal stress concentration area on the sensitive film; is the sensitivity of the fourth piezoresistor in the second longitudinal stress concentration area; is the average sensitivity of all piezoresistors; is the maximum pressure at the piezoresistor measurement point, where the maximum pressures at the measurement points corresponding to the four piezoresistors are the same; is the piezoresistive coefficient; σ x is the sensitive film x stress in the direction; σ y is the sensitive film y stress in the direction.

[0032] The embodiments of the present invention will be described below in conjunction with specific principles: The piezoresistive pressure sensor is a linear pressure sensor. The input pressure is converted into film stress through the sensitive film, and the piezoresistor converts the film stress into resistivity. The change in resistivity is detected by a Wheatstone bridge and output in the form of voltage. Among them, as Figure 3 shown, the output voltage signal obtained through the Wheatstone bridge is: (1) In the formula, V S is the power supply potential; R 1 is the resistance of the first piezoresistor on the Wheatstone bridge, R 2 is the resistance of the second piezoresistor on the Wheatstone bridge, R 3 is the resistance of the third piezoresistor on the Wheatstone bridge, R 4 is the resistance of the fourth piezoresistor on the Wheatstone bridge. Among them, each resistance R i is a function of the applied stress, that is: (2) In the formula, R i is the i resistance value of the R io th piezoresistor after the stress change of the sensitive film; i is the initial resistance value of the th piezoresistor; is the longitudinal piezoresistive coefficient; is the longitudinal stress; is the transverse piezoresistive coefficient; is the and piezoresistive coefficient in the direction perpendicular to; is the and Stress in the vertical direction; usually, a linear relationship is adopted to analyze the piezoresistive effect. According to the piezoresistive effect, for the design of a highly linear pressure sensor, the change in resistance and the pressure do not have a first-order linear relationship, and a second-order correction term needs to be added. Then, we have: (3) In the formula, the subscript i represents the i th piezoresistor in the Wheatstone bridge. is the first constant related to the sensitive film structure of the i th piezoresistor, is the second constant related to the sensitive film structure of the i th piezoresistor; Substitute formula (3) into formula (1), and assume R 2 R 3 = R 1 R 4. At this time, the output potential of the sensor is expressed by the pressure P , then we have: (4) Formula (4) is a second-order expression between the output potential V o and the input pressure P , where A = , B = , is the sensitivity of the first piezoresistor in the first transverse stress concentration zone; is the sensitivity of the second piezoresistor in the second transverse stress concentration zone; is the sensitivity of the third piezoresistor in the first longitudinal stress concentration zone; is the sensitivity of the fourth piezoresistor in the second longitudinal stress concentration zone. To further analyze the nonlinearity of the sensor, the definition of the nonlinear error of the sensor is introduced, that is, the nonlinear error expression is: (5) In the formula, NL i is the nonlinear error at the i th pressure measurement point; V o ( P i ) is the output potential of the sensor P i under the V o ( P m ) pressure measurement point; P m i P iis the i pressure of the nth measuring point; P m is the maximum pressure of the measuring point, and the output potential of the sensor V o ( p )'s calibration curve is a power series of pressure P and can be expressed as V o ( p ) = ap + bp 2 , where a represents the slope; b represents the quadratic coefficient; p represents the pressure of the measuring point; substituting into Equation (5) and simplifying, we can get: (6) where represents the nonlinear error when the pressure of the measuring point is p ; for V o ( p ) = ap + bp 2 , in the formula a >> bP m , so Equation (6) can be simplified to (7) It can be seen from Equation (7) that the nonlinear NL ( P ) is a quadratic function of pressure P . For a piezoresistive pressure sensor, the maximum nonlinear value in the entire working range appears at P = P m / 2, and its maximum nonlinear error is expressed as: (8) Assume a 2 and a 3 are positive, a 1 and a 4 are negative, define ( a 2 + a 3 - a 1 - a 4) / 4, and through calculation, the nonlinear error of the sensor is: (9) As can be seen from Equation (9), a2 is the sensitivity of the first piezoresistor in the first transverse stress concentration region; a3 is the sensitivity of the second piezoresistor in the second transverse stress concentration region; a1 is the sensitivity of the third piezoresistor in the first longitudinal stress concentration region; a4 is the sensitivity of the fourth piezoresistor in the second longitudinal stress concentration region; it should be noted that in this embodiment, the maximum pressure of the measurement points of the four piezoresistors is the same, and all are represented by P m denote 。 The non-linearity source of the sensor is that the sensitivities of the four piezoresistors are not the same, resulting in non-linearity in the output potential difference. Under the condition of constant voltage source power supply, the change in resistance is expressed by the piezoresistive effect as (10) In the formula, π 44 is the piezoresistive coefficient; S x is the stress in the x direction of the sensitive film; S y is the stress in the y direction of the sensitive film, S x - S y is the stress difference of the piezoresistor on the sensitive film, σ x is the stress in the x direction of the sensitive film; σ y is the stress in the y direction of the sensitive film. The sensitivity of the piezoresistor is not only related to the magnitude of the stress difference, but also related to the integral area of the stress difference. Among them, the magnitude of the stress difference is determined by the geometric shape of the sensitive film, but the stress difference integral can be adjusted by adjusting the position of the piezoresistor on the sensitive film. By changing the position of the piezoresistor on the sensitive film, the sensitivities of the four piezoresistors can be made equal, that is a 1 = a 2 = a 3 = a 4. Substituting into Equation (10), we can get: (11) In the formula, is the average sensitivity of all piezoresistors, a i ( NL i ) is the non-linearity value of the piezoresistive effect itself of the i-th piezoresistor, which can be subtracted by the Wheatstone bridge difference. a i is the sensitivity of the i-th piezoresistor. Therefore, the non-linearity error of the sensor is further expressed in the form of the stress integral of the piezoresistor as: (12) In the formula, A is the area of the first transverse stress concentration region; x_A and y_A are the coordinates of the center of the piezoresistor in the first transverse stress concentration region on the sensitive film; is the sensitivity of the first piezoresistor in the first transverse stress concentration region; B is the area of the second transverse stress concentration region; x_B and y_B are the coordinates of the center of the piezoresistor in the second transverse stress concentration region on the sensitive film; is the sensitivity of the second piezoresistor in the second transverse stress concentration region; C is the area of the first longitudinal stress concentration region; x_C and y_C are the coordinates of the center of the piezoresistor in the first longitudinal stress concentration region on the sensitive film; is the sensitivity of the third piezoresistor in the first longitudinal stress concentration region; D is the area of the second longitudinal stress concentration region; x_D and y_D are the coordinates of the center of the piezoresistor in the second longitudinal stress concentration region on the sensitive film; is the sensitivity of the fourth piezoresistor in the second longitudinal stress concentration region; is the average sensitivity of all piezoresistors; is the maximum pressure at the piezoresistor measurement point, where the maximum pressures at the measurement points corresponding to the four piezoresistors are the same; is the piezoresistive coefficient; σ x is the sensitive film x stress in the direction; σ y is the sensitive film y stress in the direction.

[0033] According to Equation (12), when the first piezoresistor 4 and the second piezoresistor 6 are arranged at the center positions of the corresponding transverse stress concentration regions and remain unchanged, only the positions of the third piezoresistor 5 and the fourth piezoresistor 7 are moved to adjust the sensitivity of the third piezoresistor 5 and the corresponding sensitivity of the fourth piezoresistor 7 . Until the sensitivities , , are equal after moving the positions of the third piezoresistor 5 and the fourth piezoresistor 7, the nonlinear error NL of the sensor is approximately zero.

[0034] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-precision piezoresistive pressure sensor, characterized in that, Comprising: a substrate, on which a sensitive thin film is disposed; and four piezoresistors disposed on the sensitive thin film, wherein after the four piezoresistors are connected in series in pairs and then connected in parallel to form a Wheatstone bridge, and the sensitivities of all the piezoresistors are equal.

2. The high-precision piezoresistive pressure sensor according to claim 1, characterized in that, The stress area on the sensitive thin film is divided into two transverse stress concentration areas and two longitudinal stress concentration areas; wherein, one piezoresistor is disposed in each of the transverse stress concentration area and the longitudinal stress concentration area, and the sensitivities of all the piezoresistors are equal; or one piezoresistor is disposed in each of the longitudinal stress concentration areas, and the other two piezoresistors are symmetrically disposed with respect to the center line of the sensitive thin film, and the sensitivities of all the piezoresistors are equal.

3. The high-precision piezoresistive pressure sensor according to claim 2, wherein, When one piezoresistor is disposed in each of the transverse stress concentration area and the longitudinal stress concentration area, the piezoresistor in the transverse stress concentration area is disposed transversely at the maximum stress position of the transverse stress concentration area, and the piezoresistor in the longitudinal stress concentration area is disposed longitudinally and is disposed 5 μm away from the longitudinal edge of the sensitive thin film along the maximum stress position of the longitudinal stress concentration area.

4. A high-precision piezoresistive pressure sensor according to claim 1, characterized in that, When one piezoresistor is disposed in each of the longitudinal stress concentration areas and the other two piezoresistors are symmetrically disposed with respect to the center line of the sensitive thin film, wherein, all the four piezoresistors are disposed longitudinally, and the two piezoresistors in the longitudinal stress concentration area are disposed 28 μm away from the center direction of the sensitive thin film along the maximum stress position of the longitudinal stress concentration area.

5. A design method for a high-precision piezoresistive pressure sensor, characterized in that, Comprising: obtaining the maximum stress positions corresponding to the transverse stress concentration area and the longitudinal stress concentration area; coinciding the center line of the piezoresistor with the maximum stress position; taking the direction from the edge of the sensitive thin film to the center direction or from the center of the sensitive thin film to the edge of the sensitive thin film as the moving direction, and moving the position of the piezoresistor corresponding to the longitudinal stress concentration area multiple times; obtaining the nonlinear error after each movement, and taking the position corresponding to the minimum nonlinear error as the optimal position of the piezoresistor corresponding to the longitudinal stress concentration area.

6. The design method of a high-precision piezoresistive pressure sensor according to claim 5, characterized in that, The moving range when moving from the edge of the sensitive thin film to the center direction is: 1 - 300 μm.

7. A design method of a high-precision piezoresistive pressure sensor according to claim 5, characterized in that The moving range when moving from the edge of the sensitive thin film to the center direction is: 1 - 100 μm.

8. A design method of a high-precision piezoresistive pressure sensor according to claim 5, characterized in that, The expression of the nonlinear error is: where A is the area of the first lateral stress concentration region; x_A and y_A are the coordinates of the center of the piezoresistor in the first lateral stress concentration region on the sensitive film; is the sensitivity of the first piezoresistor in the first lateral stress concentration region; B is the area of the second transverse stress concentration region; x_B and y_B are the coordinates of the center of the piezoresistor in the second transverse stress concentration region on the sensitive film; is the sensitivity of the second piezoresistor in the second transverse stress concentration region; C is the area of the first longitudinal stress concentration region; x_C, y_C are the coordinates of the center of the piezoresistor in the first longitudinal stress concentration region on the sensitive film; is the sensitivity of the third piezoresistor in the first longitudinal stress concentration region; D is the area of the second longitudinal stress concentration region; x_D and y_D are the coordinates of the center of the piezoresistor in the second longitudinal stress concentration region on the sensitive film; is the sensitivity of the fourth piezoresistor in the second longitudinal stress concentration region; is the average sensitivity of all piezoresistors; is the maximum pressure at the piezoresistor measurement point, where the maximum pressures at the measurement points corresponding to the four piezoresistors are the same; is the piezoresistive coefficient; σ x is the sensitive film x stress in the direction; σ y is the sensitive film y stress in the direction.

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