MEMS sensor and self-calibration method

Abstract

The invention provides an MEMS (Micro Electro Mechanical System) sensor and a self-calibration method. The MEMS sensor comprises a base and a sensitive film arranged on the base, an adjusting layer is arranged on the sensitive film; wherein the adjusting layer is used for generating deformation under the action of external excitation voltage; the shape of the sensitive film is adjusted through deformation of the adjusting layer, so that the difference value between the zero point position of the sensitive film and a preset reference point is within a preset range. According to the invention, the self-calibration of the MEMS sensor can be realized, and the accuracy of the MEMS sensor in the long-term use process is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of MMES products, and more specifically, to a MEMS sensor and a self-calibration method. Background Art

[0002] With the progress of society and the development of technology, in recent years, the size of electronic products such as mobile phones, computers, and wearable devices has been continuously reduced, and people have higher and higher performance requirements for these portable electronic products, which also requires the size of the electronic parts that match them to be continuously reduced, and the performance and consistency to be continuously improved. MEMS products integrated by MEMS (Micro-Electro-Mechanical-System, referred to as MEMS) technology have begun to be applied in batches to such electronic products. Their packaging volume is smaller than that of traditional electronic devices, for example, MEMS sensors are favored by most manufacturers.

[0003] For example, the principle of the existing MEMS pressure sensor is to convert the change in the spacing between the upper and lower capacitor plates into air pressure output, that is, to change the capacitance value by changing the position of the plates, and ultimately achieve pressure detection. However, during the long-term use or placement of the pressure sensor or such sensors, zero point drift will occur, affecting the detection accuracy.

[0004] Therefore, there is an urgent need for a MEMS sensor that can achieve self-calibration during long-term application to ensure long-term stability of accurate detection. Summary of the invention

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

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

[0007] In addition, an optional technical solution is that the adjustment layer includes a piezoelectric material layer arranged on the side of the sensitive film away from the base by pasting, sputtering or spraying; wherein the piezoelectric material layer includes 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, an optional technical solution is that resistor strips distributed in a bridge pattern are arranged on the sensitive film; and the regulating layer is arranged to avoid the resistor strips.

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

[0010] In addition, an optional technical solution is that the adjustment layer is arranged at a local position of the sensitive film, and the adjustment layer is arranged at at least two locations on the sensitive film, and the adjustment layer is evenly or symmetrically distributed about the center of the sensitive film.

[0011] On the other hand, the present invention also provides a MEMS sensor self-calibration method for self-calibrating the above-mentioned MEMS sensor; wherein, the method includes: after the MEMS sensor is assembled, recording the initial zero point data of the sensitive film; turning on the self-calibration function, reading the current zero point data of the MEMS sensor, and obtaining the difference between the current zero point data and the initial zero point data; determining the excitation voltage applied to the adjustment layer of the MEMS sensor according to the difference; deforming the adjustment 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.

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

[0013] In addition, an optional technical solution is to determine the excitation voltage applied to the adjustment layer of the MEMS sensor based on the difference, including: adjusting the output voltage of the ASIC chip based on the difference between the differential signal voltage of the MEMS and 0; wherein the output voltage acts as the excitation voltage on the adjustment layer.

[0014] In addition, an optional technical solution is to deform the adjustment layer through the excitation voltage, including: applying the excitation voltage to the adjustment layer to control the deformation of the adjustment layer, and driving the sensitive film to produce corresponding deformation through the adjustment layer; detecting the differential signal voltage output by the sensitive film in real time, and when the difference between the differential signal voltage and 0 is within a preset range, recording and fixing the excitation voltage.

[0015] In addition, an optional technical solution is that the output voltage of the ASIC chip is controlled by a register.

[0016] By utilizing the above-mentioned MEMS sensor and self-calibration method, an adjustment layer is set on the sensitive membrane of the MEMS. The adjustment layer can produce corresponding deformation under the action of an external excitation voltage, and then the shape of the sensitive membrane can be adjusted by the deformation of the adjustment layer, so that the zero point position of the sensitive membrane is close to the preset reference point, thereby achieving a self-calibration effect on the MEMS sensor and ensuring that the long-term detection accuracy of the product is stable and reliable.

[0017] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By referring to the following description in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more clear and easy to understand. In the accompanying drawings:

[0019] Figure 1 is a flow chart of a MEMS sensor according to an embodiment of the present invention;

[0020] Figure 2 is a schematic structural diagram of an adjustment layer according to an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of an adjustment layer according to another embodiment of the present invention;

[0022] Figure 4 is a schematic structural diagram of an adjustment layer according to another embodiment of the present invention;

[0023] Figure 5 is a schematic structural diagram of an adjustment layer according to another embodiment of the present invention;

[0024] Figure 6 is a schematic structural diagram of an adjustment layer according to another embodiment of the present invention;

[0025] Figure 7 This is a flow chart of a MEMS sensor according to Embodiment 1 of the present invention;

[0026] Figure 8 FIG. 4 is a flow chart of a MEMS sensor according to the second embodiment of the present invention.

[0027] The reference numerals are: base 1 , sensitive film 2 , adjustment layer 3 , adjustment layer 31 , adjustment layer 32 , adjustment layer 31 ′, adjustment layer 32 ′, resistor strip 4 .

[0028] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0029] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0030] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, 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 term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

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

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

[0034] Figure 1 FIG. 4 shows a schematic structure of a MEMS sensor according to an embodiment of the present invention.

[0035] like Figure 1 As shown, the MEMS sensor of the embodiment of the present invention includes a base 1 and a sensitive film 2 arranged on the base 1; an adjustment layer 3 is arranged on the sensitive film 2; wherein the adjustment layer 3 is used to generate deformation under the action of an external excitation voltage; the shape of the sensitive film 2 is adjusted by the deformation of the adjustment layer 3 to adjust the zero point position of the sensitive film 2, so that the difference between the zero point position of the sensitive film 2 and the preset reference point is within a preset range, thereby completing the self-calibration of the MEMS sensor.

[0036] Among them, the adjustment layer 3 can be a piezoelectric material layer arranged on the sensitive film 2, which can be arranged on the side of the sensitive film 2 away from the base 1 or on both sides of the sensitive film 2 by various methods such as pasting, sputtering or spraying; wherein, the piezoelectric material layer can adopt a variety of piezoelectric material thin layers such as PZT layer, AIN layer, ALN layer, ZnO layer, PVDF layer or lead-free piezoelectric ceramic layer. The adjustment layer 3 can be deformed after applying an external excitation voltage, and as the excitation voltage changes, the corresponding deformation amount will also change, thereby enabling the MEMS sensor to complete deformation adjustment in combination with the principle of piezoresistance, thereby realizing the self-calibration effect of the MEMS sensor.

[0037] The MEMS sensor of the embodiment of the present invention is further provided with a plurality of resistor bars 4 on its sensitive film 2, and a bridge distribution is formed between the resistor bars. Under ideal conditions, the differential signal voltage output by the MEMS sensor when the bridge is balanced is 0. When the sensitive film 2 is deformed during long-term placement or use, the resistance value of the resistor bars 4 thereon will also change, thereby causing the bridge balance to be broken and the output differential signal voltage to be non-0. Accordingly, the MEMS sensor can be calibrated by the differential signal voltage output by it.

[0038] Specifically, the adjustment layer 3 is located on the sensitive film 2 and avoids the resistor strips 4. The shape of the adjustment layer 3 can be adapted according to the sensitive film 2, and the size of the adjustment layer 3 is not larger than the size of the sensitive film 2. For example, the adjustment layer 3 and the sensitive film 2 can be set to have the same shape (avoiding the resistor strips 4), or the size of the adjustment layer 3 can be reduced and only set in a local area inside the sensitive film 2. Figure 1 In the schematic structure shown, the sensitive film 2 arranged on the base 1 is a rectangular structure, and the adjustment layer 3 can be a circular structure arranged inside it. The circular structure of the adjustment layer 3 can adjust the deformation of most areas of the sensitive film 2, which can ensure uniform stress distribution, and will not cause deformation of the sensitive area due to stress concentration problems, causing deformation of the varistor and nonlinear effects, thereby improving sensitivity and stability.

[0039] In addition, Figures 2 to 4 In the embodiments shown, the shape of the adjustment layer can also be set to a combination of at least one or more of a variety of shapes such as a fan, a diamond, a square, etc., to adapt to different types of resistor strips (piezoresistors) and the shape of the cavity of the base 1. In addition, due to the problem of stress concentration and inconsistent changes in the sensitive film 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 and different types of piezoelectric materials to achieve more refined sensitive film driving.

[0040] In another specific embodiment of the present invention, the adjustment layer 3 is arranged at a local position of the sensitive film 2, and the adjustment layer 3 is arranged at at least two locations on the sensitive film, and at least the two adjustment layers 3 are evenly or symmetrically distributed about the center of the sensitive film 2. This scheme can reduce the influence of the adjustment layer 3 on the sensitive layer during the signal detection process and save the laying area of ​​the adjustment layer 3. Different adjustment areas are formed by multiple adjustment layers 3, and then the core position of the sensitive film 2 is deformed and adjusted. At this time, the shape of the adjustment layer 3 can be circular, long or elliptical, etc., as long as it can adjust the deformation of the sensitive film 2.

[0041] Specifically, Figure 5 and Figure 6 The schematic structures of the adjustment layers according to the embodiments of the present invention are respectively shown.

[0042] like Figure 5 and Figure 6 As shown, in this embodiment, the shape of the adjustment layer is further divided into regions based on various shapes such as circle, sector, diamond, square, etc. The adjustment layers in different regions use different piezoelectric materials. One adjustment layer can be divided into at least two regions, and the materials of the adjustment layers in different regions are different. Therefore, the characteristics of the adjustment layer can be differentiated according to the deformation differences near the connection position between the sensitive film 2 and the base 1 and its center position during the force process, thereby improving the adjustment accuracy of the sensitive film during the self-calibration process.

[0043] Specifically, when the shape of the adjustment layer is distributed as a circle in the center (adjustment layer 31) and a fan-shaped arrangement around it (adjustment layer 32) and avoids the resistor 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 in the center and a trapezoidal arrangement around it, the piezoelectric materials of the adjustment layer 31' and the adjustment layer 32' can also be set to be different. In this way, by setting different materials in different areas of the piezoelectric material, the problem of inconsistent force deformation of the sensitive membrane can be overcome.

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

[0045] Corresponding to the above-mentioned MEMS sensor, the present invention further provides a MEMS sensor self-calibration method, which is used to perform self-calibration on the above-mentioned MEMS sensor.

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

[0047] like Figure 7 As shown, the MEMS sensor self-calibration method according to the first embodiment of the present invention includes:

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

[0049] Specifically, after the MEMS sensor is assembled, it is necessary to determine the initial zero point position, that is, the initial zero point data. The process first determines the product reference point, and then after the product group leader is completed, the zero point data of the bridge on the current sensitive membrane is recorded through fixed instructions, so that after the product self-calibration function is turned on, the real-time read zero point of the bridge and the previously stored zero point are compared to obtain the difference, and then the adjustment layer is controlled according to the difference, and the deformation of the sensitive membrane is controlled through the adjustment layer, and finally the zero point of the bridge is adjusted.

[0050] S200: Turn on 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, an instruction to start the self-calibration function can be received by an ASIC chip that is connected to the MEMS sensor. Since the differential signal voltage of the bridge is 0 in the default ideal state, the difference between the differential signal voltage of the MEMS and 0 can be detected by the ASIC chip as the difference between the current zero point data and the initial zero point data.

[0052] Among them, the user can judge the resting state of the product by himself or through the device to ensure that its calibration is carried out under the condition of meeting the resting conditions, and then turn on the self-calibration function. At this time, the external ASIC chip connected to the MEMS sensor will receive the instruction to turn on the self-calibration function, and then detect the differential signal voltage output by the current MEMS sensor, and determine the difference with 0 based on the differential signal voltage.

[0053] S300: Determine an 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 act directly on the adjustment layer as an excitation voltage, and the excitation voltage can be controlled by a register.

[0055] S400: deforming the adjustment layer through an 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, an excitation voltage is applied to the adjustment layer to control the deformation of the adjustment layer, and the sensitive film is driven to produce corresponding deformation through the adjustment layer. 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 accordingly. When the differential signal voltage is close to 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 adjustment layer to adjust the sensitive film of the sensor to a fixed position, thereby realizing self-calibration of the sensor. The self-calibration can be started by user operation or set through the device to realize timed calibration.

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

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

[0059] S201: Determine the resting state of the product through the user or the device;

[0060] S202: When the product is in a static state and meets the calibration requirements, the self-calibration function is turned on;

[0061] S203: receiving a self-calibration start instruction through an ASIC chip connected to the MEMS;

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

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

[0064] S206: controlling the output voltage to change, causing the adjustment layer and the sensitive film (layer) to deform, so as to change the differential signal output by the MEMS;

[0065] S207: Detecting the adjusted differential voltage signal until it meets the preset requirements, and recording and fixing the output voltage configuration at this time;

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

[0067] It should be noted that the above-mentioned embodiments of the self-calibration method of the MEMS sensor and the embodiments of the MEMS sensor can be referred to each other, and will not be described one by one here.

[0068] According to the MEMS sensor and self-calibration method of the present invention, an adjustment layer is provided on the sensitive membrane of the MEMS, and the adjustment layer can produce corresponding deformation under the action of an external excitation voltage, and then the shape of the sensitive membrane can be adjusted by the deformation of the adjustment layer, so that the zero point position of the sensitive membrane 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 static state of the product after assembly, self-calibration can be performed, which is relatively feasible. The device can perform timed calibration or the user can perform calibration by himself, and it is suitable for regular zeroing calibration of various differential pressure devices.

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

Claims

1. A MEMS sensor, comprising a base and a sensitive film arranged on the base; characterized in that: An adjustment layer is arranged on the sensitive film; wherein, The regulating layer is used to generate deformation under the action of an external excitation voltage; The shape of the sensitive film is adjusted by the deformation of the adjustment layer, so that the difference between the zero point position of the sensitive film and the preset reference point is within a preset range.

2. The MEMS sensor according to claim 1, characterized in that: The adjustment layer includes a piezoelectric material layer disposed on the side of the sensitive film away from the base by pasting, sputtering or spraying; wherein, The piezoelectric material layer includes a PZT layer, an AIN 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: Resistor strips distributed in a bridge pattern are arranged on the sensitive film; The regulating layer is arranged to avoid the resistor strip.

4. The MEMS sensor according to claim 1, characterized in that: The shape of the adjustment layer includes at least one of a circle, a square, a diamond, and a fan; The size of the regulating layer is not greater than that of the sensitive film.

5. The MEMS sensor according to claim 1, characterized in that: The adjustment layer is arranged at a local position of the sensitive film, and the adjustment layer is arranged at at least two positions on the sensitive film, and the adjustment layer is evenly or symmetrically distributed about the center of the sensitive film.

6. A MEMS sensor self-calibration method, characterized in that: Used to self-calibrate the MEMS sensor according to any one of claims 1 to 5; wherein the method comprises: After the MEMS sensor is assembled, the initial zero point data of the sensitive film is recorded; Turning on the self-calibration function, reading the current zero point data of the MEMS sensor, and obtaining the difference between the current zero point data and the initial zero point data; Determining an excitation voltage applied to the adjustment layer of the MEMS sensor according to the difference; The adjustment layer is deformed by 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.

7. The MEMS sensor self-calibration method according to claim 6, characterized in that: Obtaining a difference between the current zero point data and the initial zero point data, comprising: An instruction to start a self-calibration function is received through an ASIC chip that is in communication with the MEMS sensor; The difference between the differential signal voltage of the MEMS and 0 is detected by the ASIC chip as the difference between the current zero point data and the initial zero point data.

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

9. The MEMS sensor self-calibration method according to claim 7, characterized in that: The adjusting layer is deformed by the excitation voltage, comprising: Applying the excitation voltage to the adjustment layer to control the adjustment layer to deform, and driving the sensitive film to produce corresponding deformation through the adjustment layer; The differential signal voltage output by the sensitive film is detected in real time, and when the difference between the differential signal voltage and 0 is within a preset range, the excitation voltage is recorded and fixed.

10. 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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