Membrane sensor and self-calibration method

Abstract

The application provides a MEMS sensor and a self-calibration method, wherein the MEMS sensor comprises a base and a sensitive film arranged on the base; an adjusting layer is arranged on the sensitive film; the adjusting layer is used for generating deformation under the action of an external excitation voltage; the shape of the sensitive film is adjusted through the deformation of the adjusting layer, so that the difference between the zero point position of the sensitive film and a preset reference point is within a preset range. The self-calibration of the MEMS sensor can be realized by using the above-mentioned application, and the accuracy of the MEMS sensor in a long-term use process is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of MEMS product, more particularly, to a MEMS sensor and a self-calibration method. BACKGROUND

[0002] With the progress of society and the development of technology, in recent years, the volume of electronic products such as mobile phones, computers and wearable devices is continuously reduced, and people's performance requirements for these portable electronic products are also increasingly high, thereby requiring the volume of electronic parts matched with them to be continuously reduced and the performance and consistency to be continuously improved. MEMS (Micro-Electro-Mechanical-System, referred to as MEMS) process integrated MEMS products begin to be mass applied to such electronic products, and the packaging volume is smaller than that of traditional electronic devices, for example, MEMS sensors favored by most manufacturers.

[0003] For example, the principle of the existing MEMS air pressure sensor is to convert the change of the distance between the upper and lower capacitor plates into air pressure output, that is, to change the capacitance value through the position change of the electrode plate, and finally to realize the detection of pressure, but during the long-term use or placement of the air pressure sensor or such sensor, zero drift may occur, which affects the detection accuracy.

[0004] Therefore, there is an urgent need for a MEMS sensor that can realize self-calibration during long-term application to ensure long-term stability of detection accuracy. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a MEMS sensor and a self-calibration method to solve the problem that the existing MEMS product is prone to zero drift during long-term use or placement, thereby affecting the detection accuracy of the sensor.

[0006] The MEMS sensor provided by the present application comprises a base and a sensitive membrane arranged on the base; an adjusting layer is arranged on the sensitive membrane; wherein the adjusting layer is used to generate deformation under the action of an external excitation voltage; the shape of the sensitive membrane is adjusted through the deformation of the adjusting layer, so that the difference between the zero point position of the sensitive membrane and the preset reference point is within a preset range.

[0007] In addition, the optional technical solution is that the adjusting layer comprises a piezoelectric material layer arranged on the side of the sensitive membrane away from the base by pasting, sputtering or spraying; wherein the piezoelectric material layer comprises a PZT layer, an AIN layer, an ALN layer, a ZnO layer, a PVD F layer or a lead-free piezoelectric ceramic layer.

[0008] In addition, the optional technical scheme is that the sensitive film is provided with resistance strips in the form of an electric bridge; and the adjusting layer avoids the resistance strips.

[0009] In addition, the optional technical scheme is that the shape of the adjusting layer includes at least one of a circle, a square, a diamond, and a sector; and the size of the adjusting layer is not greater than the size of the sensitive film.

[0010] In addition, the optional technical scheme is that the adjusting layer is arranged at a local position of the sensitive film, and the adjusting layer is arranged at at least two positions on the sensitive film and is uniformly or symmetrically distributed about the center of the sensitive film.

[0011] In addition, the optional technical scheme is that the adjusting layer is arranged at a local position of the sensitive film, and the adjusting layer is arranged at at least two positions on the sensitive film and is uniformly or symmetrically distributed about the center of the sensitive film.

[0012] In addition, the optional technical scheme is that the difference between the current zero point data and the initial zero point data is obtained, including: receiving an instruction of starting the self-calibration function through an ASIC chip connected with the MEMS sensor; and detecting the difference between the differential signal voltage of the MEMS sensor and 0 as the difference between the current zero point data and the initial zero point data through the ASIC chip.

[0013] In addition, the optional technical scheme is that the difference between the current zero point data and the initial zero point data is obtained, including: receiving an instruction of starting the self-calibration function through an ASIC chip connected with the MEMS sensor; and detecting the difference between the differential signal voltage of the MEMS sensor and 0 as the difference between the current zero point data and the initial zero point data through the ASIC chip.

[0014] In addition, the optional technical scheme is that the difference between the current zero point data and the initial zero point data is obtained, including: receiving an instruction of starting the self-calibration function through an ASIC chip connected with the MEMS sensor; and detecting the difference between the differential signal voltage of the MEMS sensor and 0 as the difference between the current zero point data and the initial zero point data through the ASIC chip.

[0015] In addition, the output voltage of the ASIC chip is controlled by a register.

[0016] By using the MEMS sensor and the self-calibration method, the adjusting layer is arranged on the sensitive membrane of the MEMS, the adjusting layer can generate corresponding deformation under the action of the external excitation voltage, and then the shape of the sensitive membrane can be adjusted through the deformation of the adjusting layer, so that the zero position of the sensitive membrane is close to the preset reference point, and the self-calibration effect of the MEMS sensor can be realized, and the long-time detection precision stability and reliability of the product can be ensured.

[0017] To the accomplishment of the foregoing and related ends, one or more aspects of the application comprise the features hereinafter fully described. The following description and the annexed drawings set forth in detail certain illustrative aspects of the application. These aspects are indicative, however, of but a few of the various ways in which the principles of the application can be employed. Other aspects and advantages of the application will be apparent from the following detailed description of the application, as defined in the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0018] Other objects and results of the application will become more fully apparent from the following description taken in conjunction with the accompanying drawings. In the drawings:

[0019] Figure 1 Flow chart of the MEMS sensor according to the embodiment of the application;

[0020] Figure 2 Structure diagram of the adjusting layer according to the embodiment of the application;

[0021] Figure 3 Structure diagram of the adjusting layer according to another embodiment of the application;

[0022] Figure 4 Structure diagram of the adjusting layer according to another embodiment of the application;

[0023] Figure 5 Structure diagram of the adjusting layer according to another embodiment of the application;

[0024] Figure 6 Structure diagram of the adjusting layer according to another embodiment of the application;

[0025] Figure 7 Flow chart of the MEMS sensor according to the first embodiment of the application;

[0026] Figure 8 Flow chart of the MEMS sensor according to the second embodiment of the application.

[0027] Among the reference signs: base 1, sensitive membrane 2, conditioning layer 3, conditioning layer 31, conditioning layer 32, conditioning layer 31', conditioning layer 32', electric resistance strip 4.

[0028] The same reference numbers in all the figures indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0029] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It can be evident, however, that embodiments of the present application can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.

[0030] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0031] Those skilled in the art can understand that, unless specifically stated, the singular forms "a", "an" and "the" used herein also include the plural forms. It should be further understood that the use of the phrase "comprising" in the specification of the present application means that the features, integers, steps, operations, elements and / or components described exist, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that the phrase "and / or" used herein includes any one of the associated listed items and all combinations of the associated listed items.

[0032] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as that generally understood by those skilled in the art to which the present application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have meanings consistent with those in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as such.

[0033] To describe the MEMS sensor and self-calibration method in detail, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0034] Figure 1 A schematic structure of a MEMS sensor according to an embodiment of the present application is shown.

[0035] As shown in the drawings, Figure 1 The MEMS sensor according to the embodiment of the present application comprises a base 1 and a sensitive membrane 2 arranged on the base 1; an adjusting layer 3 is arranged on the sensitive membrane 2; wherein the adjusting layer 3 is used to generate deformation under the action of an external excitation voltage; the shape of the sensitive membrane 2 is adjusted through the deformation of the adjusting layer 3, so as to adjust the zero position of the sensitive membrane 2, so that the difference between the zero position of the sensitive membrane 2 and the preset reference point is within a preset range, and the self-calibration of the MEMS sensor is completed.

[0036] The adjusting layer 3 can be a piezoelectric material layer arranged on the sensitive membrane 2, which can be arranged on one side of the sensitive membrane 2 away from the base 1 or both sides of the sensitive membrane 2 by various ways such as pasting, sputtering or spraying; wherein the piezoelectric material layer can adopt various piezoelectric material thin layers such as PZT layer, AIN layer, ALN layer, ZnO layer, PVDF layer or lead-free piezoelectric ceramic layer, the adjusting layer 3 can generate deformation after an external excitation voltage is applied, and the corresponding deformation amount will change with the change of the excitation voltage, thereby the MEMS sensor combines the principle of piezoresistor to complete deformation adjustment and realize the self-calibration effect of the MEMS sensor.

[0037] The MEMS sensor according to the embodiment of the present application further comprises a plurality of resistance strips 4 arranged on the sensitive membrane 2, and the resistance strips are arranged in a bridge distribution; in an ideal state, the differential signal voltage output by the MEMS sensor bridge balance is 0, when the sensitive membrane 2 generates deformation in the process of long-term placement or use, the resistance value of the resistance strips 4 thereon will also change, thereby breaking the bridge balance and the differential signal voltage output is not 0; accordingly, the MEMS sensor can be calibrated through the differential signal voltage output by the MEMS sensor.

[0038] Specifically, the adjusting layer 3 is arranged on the sensitive membrane 2 and avoids the resistance strips 4, the shape of the adjusting layer 3 can be adapted to the sensitive membrane 2, and the size of the adjusting layer 3 is not greater than the size of the sensitive membrane 2, for example, the adjusting layer 3 and the sensitive membrane 2 can be set to be consistent in shape (avoiding the resistance strips 4), or the size of the adjusting layer 3 is reduced and only arranged in the internal local area of the sensitive membrane 2. Figure 1 As shown in the schematic structure, the sensitive membrane 2 arranged on the base 1 is in a rectangular structure, and the adjusting layer 3 can be in a circular structure arranged in the internal part of the sensitive membrane 2, the circular adjusting layer 3 can adjust the deformation of most areas of the sensitive membrane 2, and can ensure that the stress is uniformly distributed, so that the piezoresistor deformation and nonlinear effect caused by the deformation of the sensitive area due to stress concentration problem are avoided, and the sensitivity and stability are improved.

[0039] In addition, in Figures 2 to 4 In the embodiments shown, the shape of the adjustment layer can also be set as at least one or a combination of multiple shapes such as a fan shape, a diamond shape, a square shape, etc., to adapt to different types of resistance strips (piezoresistors) and the shape of the cavity of the base 1. In addition, due to the stress concentration problem and the inconsistent change of the sensitive membrane in the subsequent foreseeable MEMS sensor design, the adjustment layer can also be formed on the base 2 of the MEMS by depositing or sputtering different areas of different types of piezoelectric materials to achieve more refined driving of the sensitive membrane.

[0040] In another specific embodiment of the present application, the adjustment layer 3 is arranged at a local position of the sensitive membrane 2, and the adjustment layer 3 is arranged at least at two positions on the sensitive membrane, and the at least two adjustment layers 3 are uniformly or symmetrically distributed about the center of the sensitive membrane 2. This scheme can reduce the influence of the adjustment layer 3 on the sensitive layer during signal detection and save the laying area of the adjustment layer 3. Different adjustment regions are formed by the multiple adjustment layers 3, and then the core position of the sensitive membrane 2 is deformed and adjusted. At this time, the shape of the adjustment layer 3 can be circular, long direction, or oval, etc., which can adjust the deformation of the sensitive membrane 2.

[0041] Specifically, Figure 5 and Figure 6 The schematic structures of the adjustment layers of the embodiments of the present application are shown in FIGS. 1 to 4.

[0042] As Figure 5 and Figure 6 shown, in this embodiment, the shape of the adjustment layer is further divided into regions on the basis of multiple shapes such as a circular shape, a fan shape, a diamond shape, a square shape, etc. Different piezoelectric materials are used for the adjustment layers in different regions. One adjustment layer can be divided into at least two regions, and the materials of the adjustment layers in different regions are different. Thus, the characteristics of the adjustment layer can be set differently according to the deformation difference of the sensitive membrane 2 and the base 1 near the connection position and the center position of the sensitive membrane during stress, thereby improving the adjustment accuracy of the sensitive membrane during self-calibration.

[0043] Specifically, when the shape of the adjustment layer is distributed as a circular shape at the center (adjustment layer 31) and a fan shape around the center (adjustment layer 32) and avoids the resistance strip, the piezoelectric materials of the adjustment layer 31 and the adjustment layer 32 can be set to be different. When the shape of the adjustment layer is distributed as a diamond shape at the center and a trapezoidal shape around the center, the piezoelectric materials of the adjustment layer 31' and the adjustment layer 32' can also be set to be different. Thus, by setting different materials in different regions of the piezoelectric material, the problem of inconsistent deformation of the sensitive membrane under stress can be overcome.

[0044] In addition, it should be noted that the MEMS sensor of the embodiment of the present application can be a differential pressure device of various types such as a barometric pressure sensor, a sphygmomanometer, etc. provided with a MEMS chip, and the shape thereof is not limited to the specific structure shown in the drawings.

[0045] Corresponding to the above-described MEMS sensor, the present application also provides a MEMS sensor self-calibration method for self-calibrating the above-described MEMS sensor.

[0046] As a specific example, Figure 7 A schematic flow of the MEMS sensor self-calibration method according to the first embodiment of the present application is shown.

[0047] As Figure 7 shown, the MEMS sensor self-calibration method of the first embodiment of the present application comprises:

[0048] S100: After the MEMS sensor is assembled, the initial zero point data of the sensitive membrane is recorded.

[0049] Specifically, after the MEMS sensor is assembled, the initial zero point position, i.e. the initial zero point data, needs to be determined. The process first determines the product reference point, and then records the zero point data of the bridge on the current sensitive membrane after the product assembly is completed. After the product self-calibration function is started, the difference between the real-time reading of the bridge zero point and the previously stored zero point is obtained, and then the difference is used to control the adjustment layer, and the deformation control of the sensitive membrane is realized through the adjustment layer, and finally the adjustment of the bridge zero point is realized.

[0050] S200: Start the self-calibration function, read the current zero point data of the MEMS sensor, and obtain the difference between the current zero point data and the initial zero point data.

[0051] Specifically, the instruction for starting the self-calibration function can be received by the ASIC chip connected to the MEMS sensor. Since the differential signal voltage of the bridge is 0 in the default ideal state, the ASIC chip can detect the difference between the differential signal voltage of the MEMS and 0 as the difference between the current zero point data and the initial zero point data.

[0052] Wherein, the user can determine the resting state of the product by himself or through the device to ensure that the calibration is carried out under the condition that the resting condition is met, and then the self-calibration function is started. At this time, the external ASIC chip connected to the MEMS sensor will receive the instruction for starting the self-calibration function, and then detect the differential signal voltage output by the current MEMS sensor, and determine the difference from 0 according to the differential signal voltage.

[0053] S300: Determine the excitation voltage applied to the adjustment layer of the MEMS sensor according to the difference.

[0054] Specifically, the output voltage of the ASIC chip can be adjusted according to the difference between the differential signal voltage of the MEMS and 0; wherein the output voltage can directly act on the adjusting layer as the excitation voltage, and the excitation voltage can be controlled through a register.

[0055] S400: deforming the adjusting layer through the excitation voltage to adjust the zero point position of the sensitive film, so that the difference between the current zero point data and the initial zero point data is within a preset range.

[0056] Specifically, the excitation voltage is applied to the adjusting layer to control the deformation of the adjusting layer, and the adjusting layer drives the sensitive film to produce corresponding deformation, and at the same time, the differential signal voltage output by the sensitive film is detected in real time; when the difference between the differential signal voltage and 0 is within a preset range, the excitation voltage is recorded and fixed; for example, during the change of the excitation voltage, the differential signal voltage also changes correspondingly; when the differential signal voltage approaches 0mv, the excitation voltage at this time can be configured, recorded and fixed; finally, when the MEMS sensor is powered on, the recorded excitation voltage is applied to the adjusting layer, so that the sensitive film of the sensor can be adjusted to a fixed position, realizing self-calibration of the sensor; the self-calibration can be started by user operation or set by equipment to realize timing calibration.

[0057] As a specific example, Figure 8 A schematic flow of the self-calibration method of the MEMS sensor according to the second embodiment of the present application is shown.

[0058] As Figure 8 shown, the self-calibration method of the MEMS sensor according to the second embodiment of the present application comprises:

[0059] S201: judging the resting state of the product by the user or the equipment;

[0060] S202: starting the self-calibration function when the resting state of the product meets the calibration requirements;

[0061] S203: receiving the self-calibration starting instruction through the ASIC chip connected with the MEMS;

[0062] S204: detecting the difference between the differential signal voltage output by the current MEMS and 0 through the ASIC chip as the difference of the differential signal;

[0063] S205: adjusting the output voltage of the ASIC chip, i.e. the excitation voltage, according to the difference of the differential signal;

[0064] S206: controlling the change of the output voltage to cause the deformation of the adjusting layer and the sensitive film (layer) to change the differential signal output by the MEMS;

[0065] S207: the adjusted differential voltage signal is implemented until the preset requirement is met, and the output voltage at this time is recorded and fixed;

[0066] S208: when the MEMS sensor is powered on, the recorded excitation voltage is directly loaded to the adjustment layer, so as to realize the adjustment of the MEMS zero point and self-calibration.

[0067] It should be noted that the embodiments of the self-calibration method of the MEMS sensor described above can be mutually referenced with the embodiments of the MEMS sensor, and will not be described one by one here.

[0068] According to the MEMS sensor and the self-calibration method of the present application, the adjustment layer is arranged on the sensitive film of the MEMS, the adjustment layer can generate corresponding deformation under the action of the external excitation voltage, and then the shape of the sensitive film can be adjusted through the deformation of the adjustment layer, so that the zero point position of the sensitive film is close to the preset reference point. As long as the air pressure on both sides of the product is constant, or consistent with the rest state after the product is assembled, self-calibration can be performed, the feasibility is relatively strong, and the device can be used for timing calibration or the user can operate calibration, which is suitable for periodic zero calibration of various differential pressure devices.

[0069] The MEMS sensor and the self-calibration method according to the present application are described above with reference to the accompanying drawings in an exemplary manner. However, those skilled in the art should understand that various improvements can be made to the MEMS sensor and the self-calibration method of the present application described above without departing from the content of the present application. Therefore, the protection scope of the present application should be determined by the content of the appended claims.

Claims

1. A MEMS sensor, comprising a base and a sensitive membrane disposed on the base; characterized in that, An adjustment layer is provided on the sensitive membrane; wherein, The regulating layer is used to generate deformation under the action of an external excitation voltage; The shape of the sensitive membrane is adjusted by the deformation of the adjustment layer so that the difference between the zero point position of the sensitive membrane and the preset reference point is within a preset range. The adjustment layer includes a piezoelectric material layer disposed on the side of the sensitive film away from the base by attaching, sputtering or spraying, and the adjustment layer is divided into regions, with different piezoelectric material layers used in different regions. A resistor strip distributed in a bridge pattern is provided on the sensitive membrane, and the adjustment layer is disposed to avoid the resistor strip.

2. The MEMS sensor according to claim 1, characterized in that, The piezoelectric material layer includes a PZT layer, an AlN layer, an AlN layer, a ZnO layer, a PVDF layer, or a lead-free piezoelectric ceramic layer.

3. The MEMS sensor according to claim 1, characterized in that, The shape of the adjustment layer includes at least one of the following: circular, square, rhomboid, and fan-shaped. The size of the adjustment layer is not larger than the size of the sensitive membrane.

4. The MEMS sensor according to claim 1, characterized in that, The adjustment layer is disposed at a local location on the sensitive membrane, and the adjustment layer is disposed at least in two locations on the sensitive membrane, and the adjustment layer is uniformly or symmetrically distributed about the center of the sensitive membrane.

5. A self-calibration method for a MEMS sensor, characterized in that, For self-calibrating a MEMS sensor as described in any one of claims 1-4; wherein the method includes: After the MEMS sensor is assembled, record the initial zero-point data of the sensitive membrane; Enable the self-calibration function, read the current zero-point data of the MEMS sensor, and obtain the difference between the current zero-point data and the initial zero-point data; The excitation voltage applied to the conditioning layer of the MEMS sensor is determined based on the difference. The adjustment layer is deformed by the excitation voltage to adjust the zero point position of the sensitive membrane, so that the difference between the current zero point data and the initial zero point data is within a preset range.

6. The MEMS sensor self-calibration method according to claim 5, characterized in that, Obtaining the difference between the current zero-point data and the initial zero-point data includes: The ASIC chip, which is connected to the MEMS sensor, receives a command to enable the self-calibration function. The ASIC chip detects the difference between the differential signal voltage of the MEMS and 0, and uses this difference as the difference between the current zero-point data and the initial zero-point data.

7. The MEMS sensor self-calibration method according to claim 6, characterized in that, Determining the excitation voltage applied to the conditioning layer of the MEMS sensor based on the difference includes: The output voltage of the ASIC chip is adjusted based on the difference between the differential signal voltage of the MEMS and 0; wherein, The output voltage serves as the excitation voltage and is applied to the regulating layer.

8. The MEMS sensor self-calibration method according to claim 6, characterized in that, The deformation of the adjustment layer by the excitation voltage includes: The excitation voltage is applied to the regulating layer to control the deformation of the regulating layer, and the regulating layer drives the sensitive membrane to produce a corresponding deformation. The differential signal voltage output by the sensitive membrane is detected in real time. When the difference between the differential signal voltage and 0 is within a preset range, the excitation voltage is recorded and fixed.

9. The MEMS sensor self-calibration method according to claim 8, characterized in that, The output voltage of the ASIC chip is controlled by a register.

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