Microelectromechanical systems (MEMS) magnetic sensor unit, its calibration and manufacturing methods and electronic equipment

Abstract

This document discloses a microelectromechanical system (MEMS) magnetic sensor unit, its calibration and manufacturing method, and an electronic device thereof. The calibration method includes: scanning a DC bias voltage on the MEMS magnetic sensor using a fixed AC excitation; obtaining a first DC bias voltage corresponding to the maximum AC output amplitude of the MEMS magnetic sensor; applying the first DC bias voltage to the MEMS magnetic sensor; applying acoustic source excitation to the MEMS magnetic sensor; measuring a first output sensitivity of the MEMS magnetic sensor; and obtaining the gain parameters of the ASIC chip corresponding to the MEMS magnetic sensor based on the first output sensitivity.

Description

Technical Field

[0001] The embodiments disclosed herein relate to the field of microelectromechanical systems (MEMS) magnetic sensor technology, and specifically to a calibration method for a MEMS magnetic sensor, a manufacturing method for a single MEMS magnetic sensor unit, a single MEMS magnetic sensor unit, and an electronic device. Background Technology

[0002] In existing technologies, calibration methods are typically used during the final testing process to calibrate the packaged microelectromechanical system (MEMS) capacitive sensors to achieve the target sensitivity. This process involves acoustically measuring the initial sensitivity Sens0 at a low bias voltage Vb0, calculating the bias voltage Vb for the target sensitivity Sens, applying the bias voltage Vb, and measuring the corresponding sensitivity.

[0003] However, MEMS magnetic sensors do not have the same capacitance configuration as MEMS capacitive sensors for the same calibration. Examples of MEMS magnetic sensors include microphones, pressure sensors, and accelerometers. Summary of the Invention

[0004] One object of this disclosure is to provide a new technical solution for calibrating magnetic sensors in microelectromechanical systems.

[0005] According to a first aspect of this disclosure, a calibration method for a microelectromechanical system (MEMS) magnetic sensor is provided, comprising: scanning a DC bias voltage on the MEMS magnetic sensor using a fixed AC excitation; obtaining a first DC bias voltage corresponding to the maximum AC output amplitude of the MEMS magnetic sensor; applying the first DC bias voltage to the MEMS magnetic sensor; applying an acoustic source excitation to the MEMS magnetic sensor; measuring a first output sensitivity of the MEMS magnetic sensor; and obtaining a gain parameter of an ASIC chip corresponding to the MEMS magnetic sensor based on the first output sensitivity.

[0006] According to a second aspect of this disclosure, a method for manufacturing a microelectromechanical system (MEMS) magnetic sensor unit is provided, comprising: forming a MEMS magnetic sensor; calibrating the MEMS magnetic sensor using a calibration method for MEMS magnetic sensors according to an embodiment; and setting a gain parameter of the MEMS magnetic sensor in a storage device for the MEMS magnetic sensor.

[0007] According to a third aspect of this disclosure, a microelectromechanical system (MEMS) magnetic sensor unit manufactured using the manufacturing method of the MEMS magnetic sensor according to the embodiments is provided.

[0008] According to a fourth aspect of this disclosure, an electronic device is provided, including a microelectromechanical system magnetic sensor unit according to an embodiment.

[0009] According to embodiments of this disclosure, magnetic sensors for microelectromechanical systems can be calibrated quickly.

[0010] Other features and advantages of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0011] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present disclosure and, together with their description, serve to explain the principles of the present disclosure.

[0012] Figure 1 A schematic flowchart of a calibration method for a magnetic sensor of a microelectromechanical system according to an embodiment of the present disclosure is shown.

[0013] Figure 2 A schematic flowchart of a calibration method for a magnetic sensor of a microelectromechanical system according to an embodiment of the present disclosure is shown.

[0014] Figure 3 A schematic cross-sectional view of a microelectromechanical system magnetic sensor according to an embodiment of the present disclosure is shown.

[0015] Figure 4 A schematic diagram showing the change of magnetoresistive resistance with magnetic field in a microelectromechanical system magnetic sensor according to an embodiment of the present disclosure is shown.

[0016] Figure 5 A schematic diagram showing the output voltage variation with magnetic field in a microelectromechanical system magnetic sensor according to an embodiment of the present disclosure is shown.

[0017] Figure 6 A simulation diagram illustrating the relationship between the magnetic field and the Z-position of the magnetic reluctance according to an embodiment of the present disclosure is shown.

[0018] Figure 7 A schematic top view of a microelectromechanical system magnetic sensor according to an embodiment of the present disclosure is shown.

[0019] Figure 8 It shows along Figure 7 A cross-sectional view of line A-A' in the diagram.

[0020] Figure 9 A schematic block diagram of a microelectromechanical system magnetic sensor unit according to an embodiment of the present disclosure is shown.

[0021] Figure 10 A schematic flowchart illustrating a method for manufacturing a microelectromechanical system magnetic sensor unit according to an embodiment of the present disclosure is shown.

[0022] Figure 11A schematic diagram of an electronic device according to an embodiment of the present disclosure is shown. Detailed Implementation

[0023] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present disclosure.

[0024] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this disclosure or its application or use.

[0025] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0026] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0028] Currently, performance variations occur in microelectromechanical system (MEMS) magnetic sensors during the manufacturing process. These performance variations lead to inconsistencies in the final product's performance, resulting in product instability—a situation manufacturers want to avoid. Typically, performance consistency of MEMS magnetic sensors is improved by refining the manufacturing process. However, this approach can significantly increase the manufacturing cost of MEMS magnetic sensors. In many cases, even these improvements are insufficient to meet the performance requirements of the final product.

[0029] Here, the target sensitivity of the microelectromechanical system (MEMS) magnetic sensor is achieved by calibrating it. Since the working principle of the MEMS magnetic sensor differs from that of a capacitive sensor, a different calibration method is required.

[0030] The magnetic source, magnetoresistive element, and microelectromechanical system (MEMS) structure of a MEMS magnetic sensor can vary significantly in manufacturing. For example, the magnetic source can be a permanent magnet thin film pattern, a current line, or another magnetoresistive element with a current parallel to the magnetoresistive element. Therefore, the final performance of the manufactured MEMS magnetic sensors can vary considerably.

[0031] Magnetic sensors in microelectromechanical systems (MEMS) can be calibrated using purely acoustic methods. However, this method requires a considerable amount of calibration time, which is detrimental to improving production efficiency.

[0032] Figure 1 A schematic flowchart of a calibration method for a magnetic sensor of a microelectromechanical system according to an embodiment of the present disclosure is shown.

[0033] like Figure 1 As shown, in step S11, the DC bias voltage of the microelectromechanical system magnetic sensor is scanned using a fixed AC excitation.

[0034] Here, by simulating the excitation of the mechanical mechanism of the magnetic sensor of the microelectromechanical system through AC excitation, the time and accuracy of excitation and measurement of the mechanical mechanism can be significantly reduced.

[0035] Here, a higher frequency AC excitation is preferred. For example, the fixed AC excitation frequency is greater than 10 kHz, or greater than 20 kHz, or within the range of +5 kHz to -5 kHz of the frequency response resonant frequency of the MEMS magnetic sensor. Using such an AC excitation allows for obtaining a larger amplitude of the MEMS mechanical components with a smaller AC excitation amplitude. This enables faster calibration speeds. In particular, using an AC excitation near the frequency response resonant frequency allows for even faster calibration speeds. Ideally, calibration can be achieved with an excitation of a few millivolts. Furthermore, by using such an AC excitation, several milliseconds of calibration time can be saved in some cases compared to certain other AC excitation methods. This is beneficial for improving production efficiency.

[0036] In step S12, a first DC bias voltage corresponding to the maximum AC output amplitude of the microelectromechanical system magnetic sensor is obtained.

[0037] In step S13, a first DC bias voltage is applied to the microelectromechanical system magnetic sensor.

[0038] In step S14, an acoustic source excitation is applied to the microelectromechanical system (MEMS) magnetic sensor. The acoustic source excitation is, for example, an excitation of 1 kHz and 94 dBSPL.

[0039] The DC bias voltage, the first DC bias voltage, and the fixed AC excitation are applied to the Z-position tuning electrode of the microelectromechanical system magnetic sensor.

[0040] In step S15, the first output sensitivity of the microelectromechanical system magnetic sensor is measured.

[0041] In step S16, the gain parameters of the ASIC chip corresponding to the microelectromechanical system magnetic sensor are obtained based on the first output sensitivity.

[0042] The gain parameter is the gain of the ASIC chip and is equal to the difference between the sensor target sensitivity and the first output sensitivity.

[0043] The first DC bias voltage and the gain parameter are stored in the memory used to configure the ASIC chip.

[0044] Here, the microelectromechanical system (MEMS) magnetic sensor includes, for example, a coplanar sensing mechanism, comprising a coplanar magnetic source and a magnetoresistive resistor. In such a MEMS, even minute differences in the coplanar sensing mechanism can significantly affect the sensor's sensitivity. Therefore, employing the calibration method disclosed herein during manufacturing can effectively improve product consistency. Furthermore, the calibration method disclosed herein enhances calibration efficiency, thereby improving production efficiency.

[0045] exist Figure 1 In microelectromechanical systems (MEMS), a magnetic sensor can be, for example, a MEMS microphone. Figure 1 In this configuration, the reluctance 25 and the magnetic source 26 are coplanar. The moving part 24 is movable relative to the stationary part 23. After manufacturing is complete, Figure 1 The microelectromechanical system (MEMS) magnetic sensors shown can exhibit significant performance (sensitivity) variations. Currently, electronic device manufacturers have increasingly stringent performance requirements for MEMS magnetic sensors. Significant performance variations can reduce the yield of final electronic products. Therefore, it is necessary to improve the performance consistency of MEMS magnetic sensors. For MEMS magnetic sensors, especially those with coplanar magnetic sensing structures, the calibration method proposed here can calibrate MEMS magnetic sensors with high efficiency.

[0046] Typically, to determine the DC bias voltage and measure the final sensitivity, multiple acoustic source excitations are applied to the magnetic sensor. Each acoustic source excitation test is time-consuming, usually exceeding 100 ms. However, here, only a single acoustic source excitation test is required, and the processing of non-acoustic source excitations (e.g., electrical excitation processing) is very fast, for example, less than 1 ms. Therefore, the calibration method of this embodiment allows for faster calibration of the magnetic sensor in a microelectromechanical system, achieving higher production efficiency.

[0047] Furthermore, in traditional capacitive MEMS microphones, the initial sensitivity and target sensitivity are not linearly related due to the nonlinear relationship between sensitivity and bias voltage. However, here, by fixing the bias voltage, linear calibration can be achieved using the simple linear relationship between the initial sensitivity and target sensitivity. This method allows for higher calibration efficiency.

[0048] Figure 2 A schematic flowchart of a calibration method for a magnetic sensor of a microelectromechanical system according to an embodiment of the present disclosure is shown. Figure 2 As shown, the microelectromechanical system (MEMS) magnetic sensor includes a substrate 21, a sacrificial layer 22, a stationary component 23, a moving component 24, a magnetoresistive element 25, a magnetic source 26, and an interconnect structure 27. Passivation layers can be applied to the stationary component 23, the moving component 24, the magnetoresistive element 25, and the magnetic source 26 to protect these components. Figure 2 Only one magnetoresistive element 25 is shown in the diagram. Those skilled in the art will understand that multiple magnetoresistive elements can be provided as needed to improve the sensitivity of the magnetic sensor in the microelectromechanical system.

[0049] Figure 3 A schematic cross-sectional view of a microelectromechanical system (MEMS) magnetic sensor according to an embodiment of the present disclosure is shown. Figure 3 The diagram shows two magnetoresistors, MR1 and MR2, and a magnetic source, MS. (See diagram for reference.) Figure 3 As shown, the pinning direction of the magnetoresistive reluctance is the X-direction. The magnetic field generated by the magnetic source MS is shown by the dashed line, and the direction of the magnetic field is indicated by the arrow. The magnetic source MS moves up and down along the MZ direction. As the MS moves, MR1 / MR2 can be positioned between +Z and -Z relative to the MS. When MR1 / MR2 is at position +Z relative to the MS, the magnetic field direction received by MR1 is -X, and the magnetic field direction received by MR2 is +X; when MR1 / MR2 is at position -Z relative to the MS, the magnetic field direction received by MR1 is +X, and the magnetic field direction received by MR2 is -X. When the MS moves between the +Z and -Z positions, the resistance of MR1 changes due to the change in the magnetic field received by MR1. The position change of the MS can be determined by detecting the change in the resistance of MR1. Similarly, the position change of the MS can be determined by detecting the change in the resistance of MR2. Figure 3 In the MS, MR1 and MR2 are located on opposite sides of the MS. Thus, the resistance changes of MR1 and MR2 can produce differential results, thereby improving the detection effect.

[0050] Figure 4 A schematic diagram illustrating the variation of magnetoresistive resistance with a magnetic field in a microelectromechanical system (MEMS) magnetic sensor according to an embodiment of this disclosure is shown. Figure 4 As shown, when the magnetic field BX applied to the magnetoresistor is negative, the resistance of the magnetoresistor is at its maximum value Rmax; when the magnetic field applied to the magnetoresistor is positive, the resistance of the magnetoresistor decreases as the magnetic field strength BX increases, eventually decreasing to the minimum value Rmin.

[0051] Figure 5 A schematic diagram illustrating the output voltage variation with a magnetic field in a microelectromechanical system (MEMS) magnetic sensor according to an embodiment of the present disclosure is shown. For example, it can be utilized... Figure 3The two magnetoresistors shown are used in a bridge configuration to generate an output. For example... Figure 5 As shown, the output voltage Vout is at its minimum when the magnetic field BX is negative. As the magnetic field BX increases in the positive direction, the output voltage Vout gradually increases from its minimum value to its maximum value. Once the output voltage Vout reaches its maximum value, it stops increasing.

[0052] Figure 6 A simulation diagram illustrating the relationship between the magnetic field and the Z-position of the magnetic reluctance according to an embodiment of the present disclosure is shown. Figure 6 As shown in the figure, for example, taking MR2 as an example, the change of the magnetic field received by MR2 with the change of Z position is shown by the curve in the figure. Figure 6 Box 61 in the diagram indicates the available operating region. Within operating region 61, the curve is substantially linear. Typically, the magnetoresistive resistance is set to 0 Z relative to the magnetic source position, thus ensuring the microelectromechanical system (MEMS) magnetic sensor operates optimally. According to... Figure 6 In microelectromechanical systems (MEMS) magnetic sensors, the operating point can differ depending on the initial position of the magnetoresistive reluctance relative to the magnetic source, leading to variations in sensitivity. Furthermore, the resistance curve of each magnetoresistive reluctance relative to the magnetic field strength may also differ. In these cases, calibrating the MEMS magnetic sensor can improve its performance consistency, thereby enabling the production of products with more consistent performance.

[0053] Figure 7 A schematic top view of a microelectromechanical system magnetic sensor according to an embodiment of the present disclosure is shown. Figure 7 Microelectromechanical systems (MEMS) layer 71 is shown. The material of MEMS layer 71 can be silicon or polysilicon. Slits 72 are etched into MEMS layer 71. Dashed boxes 73 show what can be independent windows, in which the underlying substrate does not directly support MEMS layer 71. Electrodes 74 are disposed on the substrate. Figure 7 In this configuration, a magnetoresistive element 75 is positioned on the outer side of the slit 72, and a magnetic source 76 is positioned on the inner side of the slit 72. Since the independent window portion of the microelectromechanical system layer 71 located on the outer side of the slit 72 is relatively short, the magnetoresistive element 75 can be considered stationary during operation. Since the independent window portion of the microelectromechanical system layer 71 located on the inner side of the slit 72 is relatively long, the magnetic source 76 can move freely during operation.

[0054] Figure 8 It shows along Figure 7 A cross-sectional view of line A-A' in the diagram. (See diagram below.) Figure 8As shown, a sacrificial layer 82 is formed on the substrate 81. A microelectromechanical system (MEMS) layer 71 is formed on the sacrificial layer 82. An electrode 74 is formed on the MEMS layer 71. As explained earlier, the independent window portion of the MEMS layer 71 located inside the slit 72 is relatively long, therefore, this portion can serve as the movable portion 83; the independent window portion of the MEMS layer 71 located outside the slit 72 is relatively short, therefore, this portion can serve as the stationary portion 84. A magnetoresistive element 75 can be disposed on the stationary portion 84, and a magnetic source 76 can be disposed on the movable portion 83. The magnetic source 76 can be a magnetic film. Since there is no current flowing on the magnetic film, no additional power consumption of the MEMS magnetic sensor is caused by the movement of the movable portion.

[0055] exist Figure 7 and Figure 8 In the microelectromechanical system (MEMS) magnetic sensor shown, the final sensitivity of the sensor can vary significantly due to factors such as the distance between the magnetoresistive and magnetic source, their relative positions in the vertical direction (Z-direction), the magnetic field of the magnetic source, and the resistance variation characteristics of the magnetoresistive itself. To eliminate the impact of these differences on the final product, the sensitivity of the MEMS magnetic sensor can be improved by adding additional structures. However, these additional structures have limited effect on improving the performance of the MEMS magnetic sensor; furthermore, they increase manufacturing complexity and cost. Here, a novel calibration method is proposed that can improve the consistency of the sensitivity of the MEMS magnetic sensor with high efficiency without significantly increasing the manufacturing time.

[0056] Figure 9 A schematic block diagram of a microelectromechanical system magnetic sensor unit according to an embodiment of the present disclosure is shown.

[0057] like Figure 9 As shown, the microelectromechanical system magnetic sensor unit 90 may include a housing 91, a microelectromechanical system magnetic sensor 92, an ASIC 93, and a connection 94 for connecting the microelectromechanical system magnetic sensor 92 and the ASIC 93.

[0058] Figure 10 A schematic flowchart illustrating a method for manufacturing a microelectromechanical system magnetic sensor unit according to an embodiment of the present disclosure is shown.

[0059] like Figure 10 As shown, in step S91, a microelectromechanical system magnetic sensor is formed.

[0060] In step S92, the microelectromechanical system magnetic sensor is calibrated using the calibration method for microelectromechanical system magnetic sensors as described above.

[0061] In step S93, the gain parameter of the microelectromechanical system magnetic sensor is set in the storage device for the microelectromechanical system magnetic sensor.

[0062] For example, the gain parameter can be stored in Figure 9 The gain parameters are stored in the memory of the ASIC 93. Thus, in actual use, the ASIC 93 directly uses these gain parameters to adjust the gain of the final signal, thereby achieving more consistent sensitivity. Alternatively, the gain parameters can be stored in additional memory.

[0063] Compared to other microelectromechanical system (MEMS) magnetic sensor units, the MEMS magnetic sensor unit disclosed herein has gain parameters specific to the MEMS magnetic sensor within it, thereby meeting the requirement for high sensitivity consistency.

[0064] Figure 11 A schematic diagram of an electronic device according to an embodiment of the present disclosure is shown.

[0065] like Figure 11 As shown, the electronic device 100 includes the microelectromechanical system (MEMS) magnetic sensor unit 101 described above. Here, the electronic device 100 is shown as a smartphone, and the MEMS magnetic sensor unit 101 is shown as a microphone. However, those skilled in the art will understand that the electronic device 100 can also be other electronic devices, such as tablet computers, smartwatches, VR / AR display devices, etc.; and the MEMS magnetic sensor unit 101 can also be other sensor devices, such as pressure sensors, accelerometers, etc.

[0066] Although some specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this disclosure.

Claims

1. A calibration method for a magnetic sensor in a microelectromechanical system, comprising: A DC bias voltage is scanned using a fixed AC excitation to a magnetic sensor in a microelectromechanical system. Obtain the first DC bias voltage corresponding to the maximum AC output amplitude of the microelectromechanical system magnetic sensor; A first DC bias voltage is applied to the magnetic sensor of the microelectromechanical system; Apply acoustic excitation to the magnetic sensor of the microelectromechanical system; Measuring the first output sensitivity of a magnetic sensor in a microelectromechanical system; and The gain parameters of the ASIC chip corresponding to the microelectromechanical system magnetic sensor are obtained based on the first output sensitivity. Wherein, the frequency of the fixed AC excitation is greater than 10kHz, or greater than 20kHz, or within the range of +5kHz to -5kHz of the frequency response resonance peak frequency of the microelectromechanical system magnetic sensor. The microelectromechanical system magnetic sensor includes a coplanar sensing mechanical structure, which includes a coplanar magnetic source and a magnetoresistive field.

2. The calibration method according to claim 1, wherein, The gain parameter is the gain of the ASIC chip and is equal to the difference between the sensor target sensitivity and the first output sensitivity.

3. The calibration method according to claim 1, wherein, The sound source excitation is a 1 kHz excitation with a 94 dB SPL.

4. The calibration method according to claim 1, wherein, The DC bias voltage, the first DC bias voltage, and the fixed AC excitation are applied to the Z-position tuning electrode of the microelectromechanical system magnetic sensor.

5. The calibration method according to claim 1, wherein, The first DC bias voltage and the gain parameter are stored in the memory used to configure the ASIC chip.

6. A method for manufacturing a single magnetic sensor unit for a microelectromechanical system, comprising: To form a magnetic sensor for a microelectromechanical system; The microelectromechanical system magnetic sensor is calibrated using the calibration method for the microelectromechanical system magnetic sensor according to any one of claims 1-5; and The gain parameters of the microelectromechanical system (MEMS) magnetic sensor are set in the storage device used for the MEMS magnetic sensor.

7. A microelectromechanical system (MEMS) magnetic sensor unit manufactured using the manufacturing method of the MEMS magnetic sensor unit according to claim 6, wherein, The microelectromechanical system (MEMS) magnetic sensor unit includes a housing, a MEMS magnetic sensor, an ASIC, and wiring for connecting the MEMS magnetic sensor and the ASIC. The storage device for the MEMS magnetic sensor is a memory in the ASIC.

8. An electronic device comprising a microelectromechanical system magnetic sensor unit according to claim 7.

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