MEMS magnetoresistive magnetic sensor and its fabrication method

Abstract

This disclosure presents a MEMS magnetoresistive magnetic sensor and its fabrication method. It includes: a first substrate with a cavity on its first surface; a passivation layer on a second surface of the first substrate; a magnetoresistor and a varistor embedded in the passivation layer on the surface away from the first substrate, with their positions corresponding to the cavity; a magnetic permeability layer on the passivation layer on the surface away from the first substrate, having through-holes; leads and pads on the magnetic permeability layer on the surface away from the first substrate, the leads and pads being electrically connected to the magnetoresistor and varistor respectively through the through-holes; and a second substrate with a connecting hole communicating with the cavity, the surface of the second substrate being bonded to the first surface of the first substrate to form bonding thermal stress. This method utilizes bonding thermal stress in conjunction with the varistor to eliminate the influence of temperature variations in the magnetoresistive effect in the magnetoresistor, effectively suppressing temperature drift in the magnetic sensor and significantly improving its measurement accuracy.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the field of magnetic sensor technology, specifically relating to a MEMS magnetoresistive magnetic sensor and its fabrication method. Background Technology

[0002] Magnetic sensors have developed into an important branch of the modern sensor industry, widely used in defense, industry, medical, and scientific fields. Currently, commonly used magnetic sensor types mainly include magnetoelectric magnetic sensors, Hall effect magnetic sensors, and magnetoresistive magnetic sensors. Among these, magnetoresistive magnetic sensors are the most widely used due to their advantages of low power consumption, high sensitivity, and small size, especially in the field of portable devices. However, the resistance of the magnetoresistive resistor that makes up a traditional magnetoresistive magnetic sensor easily changes with external temperature, resulting in a large temperature drift in the sensor output and severely reducing the measurement accuracy.

[0003] Furthermore, in traditional magnetoresistive magnetic sensors, the change in resistance of the magnetoresistor is only approximately linearly related to the square of the change in the magnetic field strength when the range of variation in the measured magnetic field strength is small, thus enabling the measurement of the magnetic field strength. This results in a generally limited measurement range for traditional magnetoresistive magnetic sensors, severely restricting their development. Summary of the Invention

[0004] The embodiments disclosed herein aim to at least solve one of the technical problems existing in the prior art, and disclose a MEMS magnetoresistive magnetic sensor and its fabrication method.

[0005] In a first aspect, embodiments of this disclosure provide a MEMS magnetoresistive magnetic sensor, comprising:

[0006] A first substrate, wherein a cavity is provided on a first surface of the first substrate;

[0007] A passivation layer is disposed on a second surface of the first substrate opposite to its first surface;

[0008] A magnetoresistor and varistors distributed on both sides of the magnetoresistor, wherein the magnetoresistor and the varistor are both embedded in the passivation layer on the surface away from the first substrate, and the positions of the magnetoresistor and the varistor correspond to the cavity;

[0009] A magnetic permeability layer is disposed on the surface of the passivation layer opposite to the first substrate, and the magnetic permeability layer is provided with through holes;

[0010] Leads and pads are disposed on the surface of the magnetic permeability layer opposite to the first substrate, and the leads and pads are electrically connected to the magnetoresistor and the varistor respectively through the through-holes;

[0011] The second substrate has a connecting hole that communicates with the cavity. The surface of the second substrate is bonded to the first surface of the first substrate to form a bonding thermal stress, which can be transmitted to the varistor through the cavity.

[0012] In some embodiments, the magnetoresistor is provided with a magnetoresistor electrode lead-out area at its end, and the varistor is provided with a varistor electrode lead-out area at its end.

[0013] The leads and pads are electrically connected to the magnetoresistive electrode lead-out area and the varistor electrode lead-out area, respectively.

[0014] In some embodiments, the range of the MEMS magnetoresistive magnetic sensor is increased by increasing the constant voltage source value of the varistor.

[0015] In some embodiments, the thickness of the leads and pads ranges from 50 nm to 500 nm.

[0016] In some embodiments, the thickness of the magnetic permeable layer ranges from 1 μm to 100 μm.

[0017] In some embodiments, the thickness of the passivation layer ranges from 10 μm to 200 μm.

[0018] In some embodiments, the thickness of the first substrate ranges from 400 μm to 1000 μm; and / or,

[0019] The thickness of the second substrate ranges from 400 μm to 1000 μm.

[0020] In some embodiments, the cross-sectional dimension of the connecting hole is smaller than the cross-sectional dimension of the cavity.

[0021] In some embodiments, the cavity is located in the central region of the first substrate.

[0022] Secondly, embodiments of this disclosure provide a method for fabricating a MEMS magnetoresistive magnetic sensor, comprising:

[0023] An SOI wafer is provided; wherein the SOI silicon wafer includes a device layer, an oxide layer and a first substrate stacked sequentially.

[0024] The device layer of the SOI wafer is doped to form a varistor;

[0025] The two ends of the varistor are doped to form the varistor electrode lead-out region;

[0026] Narrow grooves are formed by etching the device layer of the SOI wafer;

[0027] A magnetic sensitive material layer is formed on the surface of the SOI sheet, and the magnetic sensitive material layer is patterned to form a magnetoresistor.

[0028] A metal material layer is formed on the surface of the SOI wafer, and the metal material layer is patterned to form a magnetoresistive electrode lead-out area;

[0029] Thermal oxidation is performed on the device layer regions on the SOI chip other than the varistor, varistor electrode lead-out area, magnetoresistor, and magnetoresistor electrode lead-out area to form a passivation layer;

[0030] A magnetic permeability layer is formed on the surface of the passivation layer, and the magnetic permeability layer is patterned to form a through-hole;

[0031] Leads and pads are formed on the surface of the magnetic permeability layer;

[0032] A cavity is etched on the back side of the first substrate, and the cavity corresponds to the position of the varistor and the magnetoresistor.

[0033] Provide a second substrate;

[0034] A connecting hole is etched into the second substrate, and the connecting hole corresponds to the cavity;

[0035] The second substrate is bonded to the back side of the first substrate to obtain the MEMS magnetoresistive magnetic sensor.

[0036] The MEMS magnetoresistive magnetic sensor and its fabrication method disclosed herein can utilize bonding thermal stress in conjunction with a piezoresistive resistor to eliminate the influence of temperature variations in the magnetoresistive effect in the magnetoresistive resistor, thereby effectively suppressing temperature drift of the magnetic sensor and significantly improving its measurement accuracy. Furthermore, the use of a MEMS fabrication method enables the magnetic sensor to be integrated and mass-produced, significantly reducing its size and cost.

[0037] Furthermore, the MEMS magnetoresistive magnetic sensor and its fabrication method disclosed herein can achieve stronger magnetic field measurement by increasing the constant voltage source value on the varistor, making the range of the magnetic sensor adjustable, greatly improving the range of the magnetic sensor, and increasing the flexibility of the magnetic sensor in use. Attached Figure Description

[0038] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and elements are not necessarily drawn to scale.

[0039] Figure 1This is a cross-sectional view of a MEMS magnetoresistive magnetic sensor according to an embodiment of this disclosure;

[0040] Figure 2 for Figure 1 The top view of the MEMS magnetoresistive magnetic sensor shown;

[0041] Figure 3 for Figure 1 The top view of the MEMS magnetoresistive magnetic sensor after the magnetic permeation layer has been removed is shown.

[0042] Figures 4 to 21 This is a process flow diagram of the fabrication method of the MEMS magnetoresistive magnetic sensor according to an embodiment of the present disclosure. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0045] It should also be noted that, for ease of description, only the parts relevant to this disclosure are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0046] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] like Figures 1 to 3 As shown, embodiments of this disclosure relate to a MEMS magnetoresistive magnetic sensor, including leads and pads 1, a magnetic permeability layer 2, a passivation layer 3, a magnetoresistive resistor 4, a varistor 6, a first substrate 8, and a second substrate 10.

[0048] For example, such as Figure 1 As shown, a cavity 9 is formed on the first surface of the first substrate 8. In some embodiments, the material of the first substrate 8 is one of monocrystalline silicon or polycrystalline silicon, and the thickness ranges from 400 μm to 1000 μm. Figure 1 As shown, the cross-section of cavity 9 can be a regular trapezoid.

[0049] Continue to refer to Figures 1 to 3 The passivation layer 3 is disposed on the second surface of the first substrate 8 opposite to its first surface, that is, as Figure 1 As shown, a passivation layer 3 is disposed above the first substrate 8. In some embodiments, the material of the passivation layer 3 is silicon oxide or the like, and its thickness ranges from 10 μm to 200 μm. A varistor 6, a magnetoresistor 4, and another varistor 6 are sequentially embedded in the surface of the passivation layer 3 away from the first substrate 8, i.e., the varistor 6 is distributed on both sides of the magnetoresistor 4. The positions of the magnetoresistor 4 and the varistor 6 correspond to the cavity 9. It is easy to understand that the magnetoresistor 4 has a magnetoresistive effect, and its resistance changes with the magnetic field it receives; the varistor 6 has a piezoresistive effect, and its resistance changes with the stress it receives. In some embodiments, the material of the varistor 6 is N-type doped single-crystal silicon or polycrystalline silicon, and the material of the magnetoresistor 4 is indium antimonide or the like.

[0050] Continue to refer to Figure 1 The magnetic permeability layer 2 is disposed on the surface of the passivation layer 3 opposite to the first substrate 8, and the magnetic permeability layer 2 is provided with through holes (not shown in the figure). In some embodiments, the magnetic permeability layer 2 is made of a high magnetic permeability and insulating material such as ferrite, and the thickness ranges from 1um to 100um. This layer can effectively conduct the magnetic field received from the outside to the magnetoresistive 4.

[0051] Continue to refer to Figures 1 to 3 The lead wires and pads 1 are disposed on the surface of the magnetic permeable layer 2 opposite to the first substrate 8, and the lead wires and pads 1 are electrically connected to the magnetoresistive resistor 4 and the varistor 6 respectively through the through-holes. In some embodiments, the lead wires and pads 1 are made of at least one material selected from aluminum, copper, platinum, titanium, gold, etc., and the thickness ranges from 50 nm to 500 nm.

[0052] Continue to refer to Figures 1 to 3 The second substrate 10 is provided with a connecting hole 11 that communicates with the cavity 9. The connecting hole 11 connects the cavity 9 with the external environment of the magnetic sensor to eliminate the pressure difference between them. The surface of the second substrate 10 is bonded to the first surface of the first substrate 8 to form bonding thermal stress, which can be transferred to the varistor 6 through the cavity 9. In some embodiments, the material of the second substrate 10 is borosilicate glass or the like, and the thickness ranges from 400 μm to 1000 μm.

[0053] The working principle of the MEMS magnetoresistive magnetic sensor according to the embodiments of this disclosure will be described below.

[0054] Please refer to the above. Figures 1 to 3Before the magnetic field to be measured is applied to the magnetic sensor of this embodiment, the two varistors 6 generate an upward vertical internal magnetic field in the magnetoresistor 4 after a constant voltage source is applied to form a current. When the magnetic field to be measured is applied to the magnetic sensor of this embodiment, the magnetic permeability layer 2 effectively conducts the magnetic field to the magnetoresistor 4, forming a downward vertical external magnetic field. At this time, because the directions of the internal and external magnetic fields in the magnetoresistor 4 are opposite, a portion of the external magnetic field in the magnetoresistor 4 will cancel out its internal magnetic field, causing a change in the total magnetic field strength in the magnetoresistor 4, thereby changing the resistance of the magnetoresistor 4. Then, the external detection circuit outputs voltage or current to complete the detection of the magnetic field to be measured.

[0055] During the aforementioned detection process, the magnetoresistive effect of the magnetoresistive 4 weakens (strengthens) as the external temperature rises (falls), causing the change in resistance of the magnetoresistive 4 to decrease (increase) with increasing (decreasing) temperature, resulting in temperature drift in the output of the magnetic sensor. To address this issue, the magnetic sensor of this embodiment has a cavity 9 in the first substrate 8, and a bonding interface is formed on its back side to generate bonding thermal stress. Within the operating temperature range of the magnetic sensor, this bonding thermal stress decreases (increases) with increasing (decreasing) temperature and, under the action of the cavity 9 structure, can be effectively conducted to the two varistors 6, causing the resistance of the two varistors 6 to increase (decrease) with increasing (decreasing) temperature, and the current of the two varistors 6 to decrease (increase) with increasing (decreasing) temperature, thereby causing the internal magnetic field strength formed by the two varistors 6 in the magnetoresistive 4 to decrease (increase) with increasing (decreasing) temperature. At this point, when the strength of the magnetic field to be measured (external magnetic field strength) remains constant, the total magnetic field strength in the magnetoresistive 4 will increase (decrease) with increasing (decreasing) temperature, and the change in the resistance of the magnetoresistive 4 will increase (decrease) with increasing (decreasing) temperature. In this way, the effect of the magnetoresistive effect of the magnetoresistive 4 changing with temperature is canceled out by the effect of the internal magnetic field changing with temperature, ultimately making the change in the resistance of the magnetoresistive 4 unaffected by temperature. This effectively suppresses the temperature drift of the magnetic sensor and significantly improves the measurement accuracy of the magnetic sensor.

[0056] The MEMS magnetoresistive magnetic sensor of this disclosure utilizes bonding thermal stress in conjunction with a piezoresistive resistor to eliminate the influence of temperature variations in the magnetoresistive effect in the magnetoresistive resistor, thereby effectively suppressing temperature drift and significantly improving the measurement accuracy of the magnetic sensor. Furthermore, this disclosure employs a MEMS fabrication method, enabling the magnetic sensor to be integrated and mass-produced, significantly reducing its size and cost.

[0057] For example, such as Figures 1 to 3As shown, the magnetoresistive 4 has a magnetoresistive electrode lead-out area 5 at its end, and the varistor 6 has a varistor electrode lead-out area 7 at its end. The lead wire and pad 1 are electrically connected to the magnetoresistive electrode lead-out area 5 and the varistor electrode lead-out area 7, respectively.

[0058] For example, such as Figures 1 to 3 As shown, the range of the MEMS magnetoresistive magnetic sensor is increased by increasing the constant voltage source value of the varistor 6.

[0059] Specifically, increasing the constant voltage source value across the two varistor 6 increases the initial current across them, which in turn increases the strength of the internal magnetic field generated in the magnetoresistor 4. Only by increasing the change in the strength of the measured magnetic field (external magnetic field) can the change in the magnetic sensor's resistance remain the same. This ensures that the change in the resistance of the magnetoresistor 4 maintains an approximately linear relationship with its square after the change in the measured magnetic field strength increases, thus significantly improving the range of the magnetic sensor and increasing its flexibility of use.

[0060] For example, such as Figure 1 As shown, the cross-sectional dimension of the connecting hole 11 is smaller than the cross-sectional dimension of the cavity 9.

[0061] like Figures 4 to 21 As shown, embodiments of this disclosure also provide a method for fabricating a MEMS magnetoresistive magnetic sensor. The MEMS magnetoresistive magnetic sensor has the structure described above, which can be referred to in the relevant previous descriptions and will not be repeated here. The method specifically includes the following steps:

[0062] Step 1: Provide an SOI wafer; wherein the SOI silicon wafer includes a device layer, an oxide layer and a first substrate stacked sequentially.

[0063] Specifically, in this step, please refer to Figure 4 The SOI silicon wafer has a device layer (not labeled in the figure), an oxide layer (not labeled in the figure) and a first substrate 8 stacked from top to bottom.

[0064] Step 2: Doping the device layer of the SOI wafer to form a varistor.

[0065] Specifically, in this step, please refer to Figure 5 and Figure 6 The varistor 6 is formed by N-type doping of the device layer of the SOI wafer.

[0066] Step 3: Doping is performed on both ends of the varistor to form the varistor electrode lead-out region.

[0067] Specifically, in this step, please refer to 7, the varistor electrode lead-out region 7 is formed by N-type heavy doping of both ends of the varistor 6.

[0068] Step 4: Etch the device layer of the SOI wafer to form narrow grooves.

[0069] Specifically, in this step, please refer to Figure 8 The device layer of the SOI wafer is etched to form narrow grooves (not marked in the figure) in preparation for the fabrication of magnetoresistive devices.

[0070] Step 5: Form a magnetic sensitive material layer on the surface of the SOI sheet, and pattern the magnetic sensitive material layer to form a magnetoresistor.

[0071] Specifically, in this step, please refer to Figure 9 and Figure 10 A magnetic sensitive material layer is formed on the surface of the SOI wafer. This magnetic sensitive material layer can be indium antimonide. The magnetic sensitive material layer is patterned to form a magnetoresistive resistor 4. The specific process for this patterning can be photolithography.

[0072] Step 6: Form a metal material layer on the surface of the SOI wafer, and pattern the metal material layer to form the magnetoresistive electrode lead-out area.

[0073] Specifically, in this step, please refer to Figure 11 and Figure 12 A metal material layer, such as gold, is formed on the surface of the SOI wafer. The metal material layer is patterned to form the magnetoresistive electrode lead-out area 5. The specific patterning process can be photolithography.

[0074] Step 7: Perform thermal oxidation on the device layer areas other than the varistor, varistor electrode lead-out area, magnetoresistor, and magnetoresistor electrode lead-out area on the SOI chip to form a passivation layer.

[0075] Specifically, in this step, please refer to Figure 13 Thermal oxidation is performed on the device layer regions other than the varistor 6, varistor electrode lead-out area 7, magnetoresistor 4, and magnetoresistor electrode lead-out area 5 on the SOI chip to form a passivation layer 3.

[0076] Step 8: Form a magnetic permeability layer on the surface of the passivation layer, and pattern the magnetic permeability layer to form a through hole.

[0077] Specifically, in this step, please refer to Figure 14 and Figure 15 A magnetic permeability layer 2 is formed on the surface of the passivation layer 3, and the magnetic permeability layer 2 is patterned to form through holes. The magnetic permeability layer 2 can be made of materials such as ferrite, and the patterning process can be such as photolithography.

[0078] Step 9: Form leads and pads on the surface of the magnetic permeability layer.

[0079] Specifically, in this step, please refer to Figure 16 A layer of aluminum (or other metal material) is sputtered onto the surface of the magnetic permeability layer 2, and then photolithography is performed on the aluminum layer to form top leads and pads 1.

[0080] Step 10: Etch a cavity on the back side of the first substrate, the cavity corresponding to the positions of the varistor and the magnetoresistor.

[0081] Specifically, in this step, please refer to Figure 17 and Figure 18 The cavity 9 is formed by wet etching on the back side of the first substrate 8.

[0082] Step 11: Provide a second substrate.

[0083] Specifically, in this step, please refer to Figure 19 The second substrate 10 can be borosilicate glass, etc.

[0084] Step 12: Etch a connecting hole in the second substrate, the connecting hole corresponding to the cavity.

[0085] Specifically, in this step, please refer to Figure 20 A through hole 11 is etched in the central region of the second substrate 10.

[0086] Step 13: Bond the second substrate to the back side of the first substrate to obtain the MEMS magnetoresistive magnetic sensor.

[0087] Specifically, in this step, please refer to Figure 21 The second substrate 10 is bonded to the back side of the first substrate 8 by an anodic bonding process to obtain the MEMS magnetoresistive magnetic sensor.

[0088] The method for fabricating a MEMS magnetoresistive magnetic sensor disclosed in this embodiment utilizes bonding thermal stress in conjunction with a piezoresistive resistor to eliminate the influence of temperature variations in the magnetoresistive effect in the magnetoresistive resistor, thereby effectively suppressing temperature drift of the magnetic sensor and significantly improving its measurement accuracy. Furthermore, the MEMS fabrication method employed in this embodiment enables the magnetic sensor to be integrated and mass-produced, significantly reducing its size and cost.

[0089] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A MEMS magnetoresistive magnetic sensor, characterized in that, include: A first substrate, wherein a cavity is provided on a first surface of the first substrate; A passivation layer is disposed on a second surface of the first substrate opposite to its first surface; A magnetoresistor and varistors distributed on both sides of the magnetoresistor, wherein the magnetoresistor and the varistor are both embedded in the passivation layer on the surface away from the first substrate, and the positions of the magnetoresistor and the varistor correspond to the cavity; A magnetic permeability layer is disposed on the surface of the passivation layer opposite to the first substrate, and the magnetic permeability layer is provided with through holes; Leads and pads are disposed on the surface of the magnetic permeability layer opposite to the first substrate, and the leads and pads are electrically connected to the magnetoresistor and the varistor respectively through the through-holes; The second substrate has a connecting hole that communicates with the cavity. The surface of the second substrate is bonded to the first surface of the first substrate to form a bonding thermal stress, which can be transmitted to the varistor through the cavity.

2. The MEMS magnetoresistive magnetic sensor according to claim 1, characterized in that, The magnetoresistor has a magnetoresistor electrode lead-out area at its end, and the varistor has a varistor electrode lead-out area at its end. The leads and pads are electrically connected to the magnetoresistive electrode lead-out area and the varistor electrode lead-out area, respectively.

3. The MEMS magnetoresistive magnetic sensor according to claim 1, characterized in that, The range of the MEMS magnetoresistive magnetic sensor is increased by increasing the constant voltage source value of the varistor.

4. The MEMS magnetoresistive magnetic sensor according to any one of claims 1 to 3, characterized in that, The thickness of the leads and pads ranges from 50nm to 500nm.

5. The MEMS magnetoresistive magnetic sensor according to any one of claims 1 to 3, characterized in that, The thickness of the magnetic permeable layer ranges from 1 μm to 100 μm.

6. The MEMS magnetoresistive magnetic sensor according to any one of claims 1 to 3, characterized in that, The thickness of the passivation layer ranges from 10 μm to 200 μm.

7. The MEMS magnetoresistive magnetic sensor according to any one of claims 1 to 3, characterized in that, The thickness of the first substrate ranges from 400 μm to 1000 μm; and / or, The thickness of the second substrate ranges from 400 μm to 1000 μm.

8. The MEMS magnetoresistive magnetic sensor according to any one of claims 1 to 3, characterized in that, The cross-sectional dimension of the connecting hole is smaller than the cross-sectional dimension of the cavity.

9. The MEMS magnetoresistive magnetic sensor according to any one of claims 1 to 3, characterized in that, The cavity is located in the central region of the first substrate.

10. A method for fabricating a MEMS magnetoresistive magnetic sensor, characterized in that, include: An SOI wafer is provided; wherein the SOI silicon wafer includes a device layer, an oxide layer and a first substrate stacked sequentially. The device layer of the SOI wafer is doped to form a varistor; The two ends of the varistor are doped to form the varistor electrode lead-out region; Narrow grooves are formed by etching the device layer of the SOI wafer; A magnetic sensitive material layer is formed on the surface of the SOI sheet, and the magnetic sensitive material layer is patterned to form a magnetoresistor. A metal material layer is formed on the surface of the SOI wafer, and the metal material layer is patterned to form a magnetoresistive electrode lead-out area; Thermal oxidation is performed on the device layer regions on the SOI chip other than the varistor, varistor electrode lead-out area, magnetoresistor, and magnetoresistor electrode lead-out area to form a passivation layer; A magnetic permeability layer is formed on the surface of the passivation layer, and the magnetic permeability layer is patterned to form a through-hole; Leads and pads are formed on the surface of the magnetic permeability layer; A cavity is etched on the back side of the first substrate, and the cavity corresponds to the position of the varistor and the magnetoresistor. Provide a second substrate; A connecting hole is etched into the second substrate, and the connecting hole corresponds to the cavity; The second substrate is bonded to the back side of the first substrate to obtain the MEMS magnetoresistive magnetic sensor.

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