Tunnel magnetoresistive sensor

Abstract

This application provides a tunnel magnetoresistive sensor. The tunnel magnetoresistive sensor includes a fluxgate magnetometer and multiple magnetic tunnel junctions. The induction coil of the fluxgate magnetometer is short-circuited and connected via a current line. The current line and the multiple magnetic tunnel junctions are arranged adjacent to each other. The fluxgate magnetometer is used to convert the magnetic signal of the sensed external magnetic field into a current signal. The multiple magnetic tunnel junctions are used to convert the sensed magnetic signal generated by the current signal into a voltage signal, so that the tunnel magnetoresistive sensor has a high cutoff frequency and high resolution.

Description

Technical Field

[0001] This application relates to the semiconductor field, and more particularly to a tunnel magnetoresistive sensor. Background Technology

[0002] Magnetic sensing chips are application-specific integrated circuits used to detect the magnitude, direction, and change of magnetic fields, and are the mainstream products in the field of magnetic field detection. Depending on the detection principle, magnetic sensing chips include different types such as chips based on tunnel magnetoresistive sensors (TMR sensors) and chips based on fluxgate magnetometers.

[0003] Tunnel magnetoresistive sensors consist of multiple magnetic tunnel junctions, which have relatively high noise in the low-frequency range. Therefore, when tunnel magnetoresistive sensors are used to detect weak magnetic fields with frequencies close to quasi-static or slowly changing, their own noise will result in extremely poor low-frequency resolution.

[0004] Fluxgates utilize the nonlinear magnetization characteristics of a high-permeability soft magnetic core under alternating excitation to measure external magnetic fields. By modulating a low-frequency magnetic field onto the second harmonic of a high-frequency excitation signal for detection, the low-frequency magnetic field signal is modulated into a high-frequency electrical signal, effectively avoiding noise interference (e.g., 1 / f noise generated by the preamplifier circuit and the sensor itself). Therefore, it can achieve extremely low noise density at the pT / √Hz or even fT / √Hz level in the low-frequency range (e.g., 0.1Hz), thus achieving high resolution. However, due to the limitation of its self-resonant frequency, the cutoff frequency of fluxgates is relatively low in the traditional open-circuit voltage output mode. Summary of the Invention

[0005] This application provides a tunnel magnetoresistive sensor that has a high cutoff frequency and high resolution.

[0006] In a first aspect, embodiments of this application provide a tunnel magnetoresistive sensor, comprising: a fluxgate and a plurality of magnetic tunnel junctions, wherein the induction coil of the fluxgate is short-circuited connected via a current line, and the current line and the plurality of magnetic tunnel junctions are arranged adjacent to each other;

[0007] The fluxgate is used to convert the magnetic signal of the sensed external magnetic field into a current signal;

[0008] The plurality of magnetic tunnel junctions are used to convert the magnetic signal generated by the induced current signal into a voltage signal.

[0009] In some embodiments, the plurality of magnetic tunnel structures are configured as a full-bridge circuit or a half-bridge circuit, each arm of the full-bridge circuit or the half-bridge circuit including a magnetic tunnel junction, or including a plurality of magnetic tunnel junctions connected in series, in parallel or in a mixed manner;

[0010] The two half-bridges in the full-bridge circuit are connected in parallel between the power supply and the ground point, and the midpoint of each of the two half-bridges is the two output terminals of the voltage signal; or, the half-bridge circuit is connected between the power supply and the ground point, and the two ends of the first or second bridge arm of the half-bridge circuit are the two output terminals of the voltage signal; in the full-bridge circuit or the half-bridge circuit, the first bridge arm of each half-bridge is connected to the power supply, and the second bridge arm is connected to the ground point.

[0011] In some embodiments, when the reference layer pinning directions of the plurality of magnetic tunnel junctions are the same, the directions of the current signals corresponding to the magnetic signals sensed by the first and second arms of the same half-bridge are different.

[0012] In some embodiments, when the plurality of magnetic tunnel structures form a full-bridge circuit, the directions of the current signals corresponding to the magnetic signals sensed by the first bridge arm of each of the two half-bridges are different; the directions of the current signals corresponding to the magnetic signals sensed by the second bridge arm of each of the two half-bridges are different.

[0013] In some embodiments, when the reference layer pinning directions of the magnetic tunnel junctions of the first and second arms of the same half-bridge are different, the directions of the current signals corresponding to the magnetic signals sensed by the first and second arms of the same half-bridge are the same.

[0014] In some embodiments, when the plurality of magnetic tunnels are configured as a full-bridge circuit:

[0015] When the reference layer pinning directions of the magnetic tunnel junctions of the first arms of the two half-bridges are different, the magnetic signals induced by the two half-bridges correspond to the same current signals.

[0016] When the reference layer pinning direction of the magnetic tunnel junction of the first arm of each of the two half-bridges is the same, the directions of the current signals corresponding to the magnetic signals induced by the two half-bridges are different.

[0017] In some embodiments, the current line comprises multiple segments with different routing directions.

[0018] In some embodiments, the current lines are routed in a bow-shaped or U-shaped pattern.

[0019] In some embodiments, the number of fluxgates is one or more, each fluxgate corresponds to a set of magnetic tunnel junctions, and the set of magnetic tunnel junctions is the plurality of magnetic tunnel junctions;

[0020] Each fluxgate is used to convert the magnetic signal of an external magnetic field sensed in a preset direction into a current signal, wherein the preset direction is consistent with the direction of the magnetic core of the fluxgate.

[0021] In some embodiments, the plurality of magnetic tunnel junctions and the current lines are disposed within the shielding range of a magnetic shielding structure, the magnetic shielding structure being used to shield the external magnetic field.

[0022] The tunnel magnetoresistive sensor provided in this application uses a fluxgate magnetometer and multiple magnetic tunnel junctions to jointly detect the external magnetic field. The fluxgate magnetometer acts as the input preamplifier, modulating the external magnetic field to be detected into a high-frequency signal. This high-frequency signal is output as a short-circuit current signal. The high-frequency short-circuit current signal is then converted into a voltage signal output by the multiple magnetic tunnel junctions. This scheme avoids the problem of low low-frequency resolution caused by multiple magnetic tunnel junctions directly processing low-frequency signals. At the same time, it also has the advantages of high cutoff frequency, high resolution, and miniaturization of fluxgate magnetometers in short-circuit current output mode. It solves the problems of low cutoff frequency of fluxgate magnetometers in traditional open-circuit voltage output mode, and the need for multiple turns of coil in this mode, which is not conducive to miniaturization. In addition, using voltage signal output is beneficial for practical application in actual products. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] Figure 1 This is a schematic diagram of the structure of a fluxgate in related technologies;

[0025] Figure 2 This is a schematic diagram of the structure of a tunnel magnetoresistive sensor provided in this application;

[0026] Figure 3 A schematic diagram of a full-bridge circuit provided in this application;

[0027] Figure 4 This application provides a schematic diagram of the magnetic moment of a full-bridge circuit and the direction of the current signal in the current line. Figure 1 ;

[0028] Figure 5 This application provides a schematic diagram of the magnetic moment of a full-bridge circuit and the direction of the current signal in the current line. Figure 2 ;

[0029] Figure 6 This application provides a schematic diagram of the magnetic moment of a full-bridge circuit and the direction of the current signal in the current line. Figure 3 ;

[0030] Figure 7 This application provides a schematic diagram of the magnetic moment of a half-bridge circuit and the direction of the current signal in the current line. Figure 1 ;

[0031] Figure 8This application provides a schematic diagram of the magnetic moment of a half-bridge circuit and the direction of the current signal in the current line. Figure 2 ;

[0032] Figure 9 A schematic diagram of a single-axis sensor provided in this application;

[0033] Figure 10 A schematic diagram of a dual-axis sensor provided in this application;

[0034] Figure 11 A schematic diagram of a triaxial sensor provided in this application;

[0035] Figure 12 A schematic diagram of the manufacturing process of a tunnel magnetoresistive sensor provided in this application;

[0036] Figure 13 A cross-sectional schematic diagram of a tunnel magnetoresistive sensor provided in this application;

[0037] Figure 14 A schematic flowchart illustrating a method for fabricating a tunnel magnetoresistive sensor provided in this application;

[0038] Figure 15 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 1 ;

[0039] Figure 16 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 2 ;

[0040] Figure 17 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 3 ;

[0041] Figure 18 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 4 ;

[0042] Figure 19 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 5 ;

[0043] Figure 20 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 6 ;

[0044] Figure 21 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 7 ;

[0045] Figure 22A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 8 ;

[0046] Figure 23 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 9 ;

[0047] Figure 24 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 ;

[0048] Figure 25 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 one;

[0049] Figure 26 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 two;

[0050] Figure 27 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 three;

[0051] Figure 28 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 Four;

[0052] Figure 29 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 five;

[0053] Figure 30 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 six;

[0054] Figure 31 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 seven;

[0055] Figure 32 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 eight;

[0056] Figure 33 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 10 Nine;

[0057] Figure 34 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 2 ten;

[0058] Figure 35 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 2 eleven;

[0059] Figure 36 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 2 twelve;

[0060] Figure 37 A schematic diagram of the fabrication process of a tunnel magnetoresistive sensor provided in this application. Figure 2 Thirteen.

[0061] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0062] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application.

[0063] Figure 1 This is a schematic diagram of a fluxgate magnetometer in related technologies. For example... Figure 1 As shown, when a high-frequency excitation signal is applied to the core of a fluxgate magnetometer, the induction coil wound on the core outputs an induced voltage when subjected to an external magnetic field, thus converting the low-frequency magnetic signal of the external magnetic field into a high-frequency voltage signal. Fluxgate magnetometers can effectively avoid noise interference (e.g., 1 / f noise generated by the preamplifier circuit and the sensor itself), therefore, they can achieve extremely low noise densities at the pT / √Hz or even fT / √Hz level in the low-frequency range (e.g., 0.1 Hz), solving the problem of poor resolution of tunnel magnetoresistive sensors at low frequencies. However, the cutoff frequency of the fluxgate magnetometer is limited by its self-resonant frequency. Figure 1 In the open-circuit voltage output mode shown, the fluxgate's cutoff frequency is limited to the kHz level; for example, the cutoff frequency is 1 / 5 of its self-resonant frequency, which is relatively low. For applications requiring response to high-frequency dynamic magnetic fields above the kHz level (such as switching power supply current monitoring, motor drive fault diagnosis, magnetic field detection in wireless charging systems, and fast magnetic pulse detection), fluxgate sensors are unsuitable.

[0064] To address the low cutoff frequency issue, fluxgate magnetometers can employ a short-circuit current output mode, where the induction coil is short-circuited. In this mode, a high-frequency excitation signal is applied to the core of the fluxgate magnetometer. When subjected to an external magnetic field, the induction coil wound around the core outputs a short-circuit current signal, thus converting the low-frequency magnetic signal from the external magnetic field into a high-frequency current signal. Compared to the open-circuit voltage output mode, the short-circuit current output mode eliminates the resonant effects of the inductance and distributed capacitance of the induction coil, raising the self-resonant frequency of the fluxgate magnetometer to at least MHz, thereby increasing the cutoff frequency. Furthermore, the number of turns in the induction coil can be significantly reduced, facilitating device miniaturization. However, in the short-circuit current output mode, the signal processing circuitry struggles to directly process the current signal.

[0065] Therefore, this application proposes a tunnel magnetoresistive sensor, referring to... Figure 2 As shown, the tunnel magnetoresistive sensor includes: a fluxgate 201 and multiple magnetic tunnel junctions 202. Figure 2 The diagram illustrates multiple magnetic tunnel junctions 202 in a modular manner. The specific structure and circuitry of the multiple magnetic tunnel junctions 202 will be described in subsequent embodiments. The induction coil 2011 of the fluxgate 201 is short-circuited via a current line 2012, which is arranged adjacent to the multiple magnetic tunnel junctions 202. Optionally, the number of turns of the induction coil 2011 is less than or equal to 3.

[0066] The fluxgate 201 is used to convert the magnetic signal of the sensed external magnetic field into a current signal.

[0067] Multiple magnetic tunnel junctions 202 are used to convert the induced magnetic signal generated by the current signal into a voltage signal.

[0068] In this embodiment, the fluxgate 201 employs a short-circuit current output mode. An excitation signal is applied to the core 2013 of the fluxgate. When subjected to an external magnetic field, a current signal is generated in the induction coil 2011 and the current line 2012, thereby converting the magnetic signal of the external magnetic field into a current signal. As described above, the short-circuit current output mode eliminates the resonance effect of the inductance and distributed capacitance of the induction coil 2011, increasing the self-resonant frequency of the fluxgate 201 and thus giving it a high cutoff frequency. To further process the current signal, multiple magnetic tunnel junctions 202 are arranged adjacent to the current line 2012. These multiple magnetic tunnel junctions 202 are used to sense the magnetic field generated by the current signal in the current line 2012, that is, to sense the magnetic signal generated by the current signal. Under the action of this magnetic signal, the resistance of the multiple magnetic tunnel junctions 202 changes, thereby outputting a corresponding voltage signal, thus converting the current signal of the fluxgate 201 into a voltage signal.

[0069] The tunnel magnetoresistive sensor in this application uses a fluxgate gate 201 and multiple magnetic tunnel junctions 202 to jointly detect the external magnetic field. The fluxgate gate 201 acts as the input preamplifier, modulating the external magnetic field to be detected into a high-frequency signal. This high-frequency signal is output as a short-circuit current signal. The high-frequency short-circuit current signal is then converted into a voltage signal by the multiple magnetic tunnel junctions 202. This scheme avoids the problem of low low-frequency resolution caused by the multiple magnetic tunnel junctions 202 directly processing the low-frequency signal. At the same time, it also has the advantages of high cutoff frequency, high resolution, and miniaturization of the fluxgate gate 201 in the short-circuit current output mode. It solves the problems of low cutoff frequency of the fluxgate gate in the traditional open-circuit voltage output mode and the need for multiple turns of coil in this mode, which is not conducive to miniaturization. In addition, using a voltage signal for output is beneficial for practical application in actual products.

[0070] Based on the above embodiments, a specific circuit composed of multiple magnetic tunnel junctions 202 will be described.

[0071] In some implementations, multiple magnetic tunnel junctions 202 constitute a full-bridge circuit. Each arm of the full-bridge circuit includes a magnetic tunnel junction 202, or multiple magnetic tunnel junctions 202 connected in series, parallel, or mixed. The two half-bridges in the full-bridge circuit are connected in parallel between the power supply and the ground point, and the midpoint of each half-bridge is the two output terminals of the voltage signal. The first arm of each half-bridge in the full-bridge circuit is connected to the power supply, and the second arm is connected to the ground point.

[0072] Reference Figure 3 As shown, the full-bridge circuit includes two half-bridges, namely the first half-bridge 301 and the second half-bridge 302. In this embodiment, the two arms of each half-bridge are referred to as the first arm and the second arm, respectively. The arm connected to the power supply is called the first arm. In the figure, V is used as the numeral for the first arm. DD Power supply voltage; the bridge arm connected to ground (GND) is called the second bridge arm. For example, as... Figure 3 As illustrated, the upper arm of each of the first half-bridge 301 and the second half-bridge 302 is its first arm, and the lower arm of each of the first half-bridge 301 and the second half-bridge 302 is its second arm. The midpoint between the first arm and the second arm of the first half-bridge 301 is the output terminal V. out1 In the second half-bridge 302, the midpoint between the first and second bridge arms is the output terminal V. out2 Two output terminals V out1 and V out2 The voltage between them is the voltage signal obtained by the full-bridge circuit, which is also the multiple magnetic tunnel junctions 202, converting the induced magnetic signal.

[0073] Because the current line 2012 and multiple magnetic tunnel junctions 202 in the tunnel magnetoresistive sensor are arranged adjacently, that is, the current line 2012 is adjacent to the full-bridge circuit, the current signal in the current line 2012 generates a magnetic field when it flows past the full-bridge circuit. This magnetic signal affects each arm of the full-bridge circuit, causing a change in the resistance of each arm, which in turn affects the two output terminals V. out1 and V out2 Output voltage signal between.

[0074] Reference Figure 4 As shown, when the reference layer pinning direction is the same for all magnetic tunnel junctions 202, Figure 4 The right-pointing arrows indicate the reference layer pinning direction of the magnetic tunnel junction 202 in each bridge arm. In this case, the directions of the current signals corresponding to the magnetic signals induced in the first and second bridge arms of the same half-bridge are different. The direction of the current signal corresponding to the magnetic signal induced in each bridge arm is the direction of the current signal in the current line 2012 passing through that bridge arm. It can be understood that during wiring, the current line 2012 can include multiple segments with different routing directions, so that the current line 2012 can have different current signal directions when passing through different bridge arms.

[0075] like Figure 4 As shown, in the first half-bridge 301, the reference layer pinning directions of the magnetic tunnel junctions 202 in the first and second arms are the same. However, the directions of the current signals when the current line 2012 passes through the first and second arms of the first half-bridge 301 are different, resulting in different changes in the resistance of the first and second arms of the first half-bridge 301—one increases while the other decreases. Similarly, in the second half-bridge 302, the reference layer pinning directions of the magnetic tunnel junctions 202 in the first and second arms are the same. However, the directions of the current signals when the current line 2012 passes through the first and second arms of the second half-bridge 302 are different, resulting in different changes in the resistance of the first and second arms of the second half-bridge 302—one increases while the other decreases. Figure 4 The arrows pointing up and down indicate the direction of the current signal in the current lines 2012 passing through each bridge arm.

[0076] In addition, in order to ensure that the two output terminals V out1 and V out2A differential signal is generated between them. In the full-bridge circuit, the directions of the current signals corresponding to the magnetic signals induced in the first bridge arms of the first half-bridge 301 and the second half-bridge 302 are different, resulting in different changes in the resistance values ​​of the first bridge arms of the first half-bridge 301 and the second half-bridge 302, i.e., one increases and the other decreases. Similarly, the directions of the current signals corresponding to the magnetic signals induced in the second bridge arms of the first half-bridge 301 and the second half-bridge 302 are different, resulting in different changes in the resistance values ​​of the second bridge arms of the first half-bridge 301 and the second half-bridge 302, i.e., one increases and the other decreases. For example, in the first half-bridge 301, the resistance value of the first bridge arm increases and the resistance value of the second bridge arm decreases, while in the second half-bridge 302, the resistance value of the first bridge arm decreases and the resistance value of the second bridge arm increases. In this way, a differential signal can be generated at the two output terminals V. out1 and V out2 The output is a differential voltage signal.

[0077] Reference Figure 5 and Figure 6 As shown, in a full-bridge circuit, when the reference layer pinning directions of the magnetic tunnel junctions of the first and second arms of the same half-bridge are different, the directions of the current signals corresponding to the magnetic signals induced by the first and second arms of the same half-bridge are the same.

[0078] like Figure 5 As shown, Figure 5 The left and right arrows indicate the reference layer pinning direction of the magnetic tunnel junctions 202 in each bridge arm. In the first half-bridge 301, the reference layer pinning directions of the magnetic tunnel junctions 202 in the first and second arms are different. When the current line 2012 passes through the first and second arms of the first half-bridge 301, the direction of the current signal is the same, resulting in different changes in the resistance of the first and second arms of the first half-bridge 301—one increases, and the other decreases. Similarly, in the second half-bridge 302, the reference layer pinning of the magnetic tunnel junctions 202 in the first and second arms is different. When the current line 2012 passes through the first and second arms of the second half-bridge 302, the direction of the current signal is the same, resulting in different changes in the resistance of the first and second arms of the second half-bridge 302—one increases, and the other decreases. Figure 5 The upward arrows in the middle indicate the direction of the current signal in the current lines 2012 passing through each bridge arm.

[0079] In addition, in order to ensure that the two output terminals V out1 and V out2 A differential signal is generated between them, as referenced. Figure 5In a full-bridge circuit, when the reference layer pinning directions of the magnetic tunnel junctions of the first arms of the two half-bridges are different, the directions of the current signals corresponding to the magnetic signals induced by the two half-bridges are the same. This causes different changes in the resistance values ​​of the first arms of the first half-bridge 301 and the second half-bridge 302—one increases and the other decreases; similarly, different changes in the resistance values ​​of the second arms of the first half-bridge 301 and the second half-bridge 302—one increases and the other decreases. For example, in the first half-bridge 301, the resistance of the first arm increases and the resistance of the second arm decreases; in the second half-bridge 302, the resistance of the first arm decreases and the resistance of the second arm increases. Thus, at the two output terminals V... out1 and V out2 The output is a differential voltage signal.

[0080] like Figure 6 As shown, Figure 6 The left and right arrows indicate the reference layer pinning direction of the magnetic tunnel junctions 202 in each bridge arm. In the first half-bridge 301, the reference layer pinning directions of the magnetic tunnel junctions 202 in the first and second arms are different. When the current line 2012 passes through the first and second arms of the first half-bridge 301, the direction of the current signal is the same, resulting in different changes in the resistance of the first and second arms of the first half-bridge 301—one increases, and the other decreases. Similarly, in the second half-bridge 302, the reference layer pinning of the magnetic tunnel junctions 202 in the first and second arms is different. When the current line 2012 passes through the first and second arms of the second half-bridge 302, the direction of the current signal is the same, resulting in different changes in the resistance of the first and second arms of the second half-bridge 302—one increases, and the other decreases. Figure 6 The arrows pointing up and down indicate the direction of the current signal in the current lines 2012 passing through each bridge arm.

[0081] In addition, in order to ensure that the two output terminals V out1 and V out2 A differential signal is generated between them, as referenced. Figure 6 In a full-bridge circuit, when the reference layer pinning direction of the magnetic tunnel junction of the first arm of each of the two half-bridges is the same, the directions of the current signals corresponding to the magnetic signals induced by the two half-bridges are different. This causes different changes in the resistance of the first arm of each of the first half-bridges 301 and 302—one increases and the other decreases; similarly, different changes in the resistance of the second arm of each of the first half-bridges 301 and 302—one increases and the other decreases. For example, in the first half-bridge 301, the resistance of the first arm increases and the resistance of the second arm decreases; in the second half-bridge 302, the resistance of the first arm decreases and the resistance of the second arm increases. Thus, at the two output terminals V... out1 and V out2The output is a differential voltage signal.

[0082] In some implementations, multiple magnetic tunnel junctions 202 constitute a half-bridge circuit. Each arm of the half-bridge circuit includes a magnetic tunnel junction 202, or multiple magnetic tunnel junctions 202 connected in series, parallel, or mixed. The half-bridge circuit is connected between a power supply and a ground point. The two ends of the first or second arm of the half-bridge circuit are the two output terminals of a voltage signal. The first arm is connected to the power supply, and the second arm is connected to the ground point.

[0083] Reference Figure 7 As shown, Figure 7 In this circuit, the two ends of the second bridge arm of the half-bridge circuit are used as the two output terminals V of the voltage signal. out1 and V out2 For example, when the reference layer pinning directions of multiple magnetic tunnel junctions 202 are the same, the reference layer pinning directions of the magnetic tunnel junctions 202 in the first and second arms of the half-bridge circuit are the same, but the directions of the current signals corresponding to the magnetic signals induced in the first and second arms are different. Figure 7 The right-hand arrows indicate the reference layer pinning direction of the magnetic tunnel junctions 202 in each bridge arm, while the up-down arrows indicate the direction of the current signal in the current lines 2012 passing through each bridge arm. The reference layer pinning direction of the magnetic tunnel junctions 202 in the first and second arms of the half-bridge circuit is the same, but the direction of the current signal when the current lines 2012 pass through the first and second arms is different. This causes different changes in the resistance values ​​of the first and second arms of the half-bridge circuit—one increases and the other decreases—resulting in different values ​​at the two output terminals V. out1 and V out2 The corresponding voltage signal is output between them.

[0084] Reference Figure 8 As shown, Figure 8 In this circuit, the two ends of the second bridge arm of the half-bridge circuit are used as the two output terminals V of the voltage signal. out1 and V out2 For example, when the reference layer pinning directions of multiple magnetic tunnel junctions 202 are different, the reference layer pinning directions of each magnetic tunnel junction 202 in the first and second arms of the half-bridge circuit are different, and the directions of the current signals corresponding to the magnetic signals induced in the first and second arms are the same. Figure 8 The left and right arrows indicate the reference layer pinning direction of the magnetic tunnel junctions 202 in each bridge arm, and the upward arrow indicates the direction of the current signal in the current line 2012 passing through each bridge arm. The reference layer pinning directions of the magnetic tunnel junctions 202 in the first and second arms of the half-bridge circuit are different, while the direction of the current signal in the current line 2012 passing through the first and second arms is the same. This causes different changes in the resistance values ​​of the first and second arms of the half-bridge circuit—one increases and the other decreases—resulting in different values ​​at the two output terminals V.out1 and V out2 The corresponding voltage signal is output between them.

[0085] Based on the above embodiments, the fluxgate 201 and multiple magnetic tunnel junctions 202 in the tunnel magnetoresistive sensor of this application embodiment can be configured as follows: Figure 9 The circuit shown, Figure 9 The diagram illustrates a full-bridge circuit composed of multiple magnetic tunnel junctions 202 as an example. (Refer to...) Figure 9 As shown, in this tunnel magnetoresistive sensor, the magnetic core 2013 of the fluxgate is oriented along the y-axis, which can be used to detect the component of the external magnetic field along the y-axis. Therefore, this tunnel magnetoresistive sensor is a single-axis sensor. It should be noted that if the magnetic core 2013 of the fluxgate is oriented along the x-axis, it can be used to detect the component of the external magnetic field along the x-axis; if the magnetic core 2013 of the fluxgate is oriented along the z-axis, it can be used to detect the component of the external magnetic field along the z-axis.

[0086] In the tunnel magnetoresistive sensor of this application embodiment, there are one or more fluxgates, each fluxgate corresponds to a set of magnetic tunnel junctions, and a set of magnetic tunnel junctions consists of multiple magnetic tunnel junctions; each fluxgate is used to convert the magnetic signal of the external magnetic field sensed in a preset direction into a current signal, wherein the preset direction is consistent with the magnetic core direction of the fluxgate.

[0087] In the case where there is only one fluxgate, for example... Figure 9 As shown, the tunnel magnetoresistive sensor is a single-axis sensor.

[0088] When there are two fluxgates, such as Figure 10 As shown, each of the two fluxgates corresponds to a set of magnetic tunnel junctions, and the circuit is illustrated using a set of magnetic tunnel junctions to form a full-bridge circuit. The working principle of the two fluxgates and their corresponding sets of magnetic tunnel junctions is explained in the aforementioned embodiment. The magnetic core 2013 of one fluxgate is oriented along the y-axis and is used to detect the y-axis component of the external magnetic field; the magnetic core 2013 of the other fluxgate is oriented along the x-axis and is used to detect the x-axis component of the external magnetic field, thus forming a dual-axis sensor.

[0089] When there are three fluxgates, such as Figure 11 As shown, each of the three fluxgates corresponds to a set of magnetic tunnel junctions, and the circuit is illustrated using a set of magnetic tunnel junctions to form a full-bridge circuit. The working principle of the three fluxgates and their corresponding sets of magnetic tunnel junctions is explained in the aforementioned embodiment. The magnetic core 2013 of one fluxgate is oriented along the y-axis to detect the y-axis component of the external magnetic field; the magnetic core 2013 of another fluxgate is oriented along the x-axis to detect the x-axis component of the external magnetic field; and the magnetic core 2013 of yet another fluxgate is oriented along the z-axis to detect the z-axis component of the external magnetic field, thus forming a triaxial sensor.

[0090] In practical applications, the number of fluxgates in the tunnel magnetoresistive sensor can be set according to the application scenario to meet the magnetic field detection requirements in different scenarios.

[0091] Figure 12 This is a schematic diagram of the manufacturing process of the tunnel magnetoresistive sensor according to an embodiment of this application. Figure 12 The example still uses a full-bridge circuit composed of multiple magnetic tunnel junctions 202. Figure 12 As can be seen, the current line 2012 comprises multiple segments with different routing directions. When passing through the bridge arm of the full-bridge circuit, the current line 2012 is a bow-shaped routing line. Optionally, the current line 2012 can also be a U-shaped routing line or other forms of routing, as long as the current direction passing through the bridge arm can be guaranteed to meet the description of the aforementioned embodiment. The induction coil 2011 includes a top coil 1101 and a bottom coil 1102, which are connected through a via 1103. Each of the multiple magnetic tunnel junctions 202 is connected through a top electrode 1201 and a bottom electrode 1202.

[0092] Figure 13 yes Figure 12 The diagram shows a cross-sectional view of the tunnel magnetoresistive sensor along the dashed line. Besides... Figure 12 In addition to the structural parts shown, Figure 13 The diagram also illustrates the substrate 1203, the dielectric 1200, and the magnetic shielding structure 1205.

[0093] Reference Figure 12 and Figure 13 Multiple magnetic tunnel junctions 202 and current lines 2012 are disposed within the shielding area of ​​a magnetic shielding structure 1205, which is used to shield external magnetic fields. In this embodiment, a fluxgate 201 is used to sense external magnetic fields, and multiple magnetic tunnel junctions 202 are used to sense current signals in the current lines 2012. Therefore, multiple magnetic tunnel junctions 202 and current lines 2012 need to be disposed within the shielding area of ​​the magnetic shielding structure 1205 to avoid inaccurate detection results caused by interference from external magnetic fields.

[0094] The following describes the fabrication method of the tunneling magnetoresistive sensor provided in the embodiments of this application. This fabrication method is used for... Figure 13 The preparation process of the cross-section shown will be explained. (Refer to...) Figure 14 As shown, the preparation method includes:

[0095] S141. A film layer is deposited on the substrate, and photolithography and etching are performed to form a magnetic tunnel junction.

[0096] Reference Figures 15-18As shown, for example, a magnetic tunnel junction can be prepared using the following method:

[0097] First, a bottom electrode layer 1401, a magnetic tunnel junction layer 1402, a hard mask layer 1403, and photoresist are sequentially deposited on a substrate 1203. The magnetic tunnel junction layer 1402 includes, but is not limited to, a free layer, a tunneling layer, and a reference layer. Then, a patterned first photoresist 1207 is formed by photolithography to obtain the desired result. Figure 15 The film structure shown is then used as a mask, and the hard mask layer 1403 is etched to form the first hard mask structure 1206, resulting in the film structure shown. Figure 16 The film structure shown is then used as a mask, and the magnetic tunnel junction layer 1402 is etched to form the magnetic tunnel junction 202, resulting in the structure shown. Figure 17 The film structure shown is then used to deposit a protective dielectric layer 1405 on the magnetic tunnel junction 202 using chemical vapor deposition (CVD) and physical vapor deposition (PVD) methods to protect the sidewalls of the magnetic tunnel junction 202, resulting in the structure shown. Figure 18 The membrane structure shown.

[0098] S142, Perform photolithography and etching to form the bottom electrode.

[0099] Reference Figures 19-22 As shown, for example, the bottom electrode can be prepared using the following method:

[0100] Photoresist is deposited over the dielectric protective layer 1405, and a patterned second photoresist 1208 is formed by photolithography to obtain the following... Figure 19 The film structure shown; using a patterned second photoresist 1208 as a mask, the dielectric protective layer 1405 is etched to form a second hard mask structure 1209, resulting in the film structure shown. Figure 20 The film structure shown is then used; subsequently, using the second hard mask structure 1209 as a mask, the bottom electrode layer 1401 is etched to form the bottom electrode 1202, resulting in the film structure shown. Figure 21 The film structure shown is as follows: a first interlayer dielectric layer 1210 is deposited, and then the surface is planarized using chemical mechanical polishing (CMP). The second hard mask structure 1209 and the first interlayer dielectric layer 1210 are polished until the magnetic tunnel junction 202 is exposed, resulting in the film structure shown. Figure 22 The membrane structure shown.

[0101] S143. Perform photolithography and etching to form the top electrode.

[0102] Reference Figures 23-25 As shown, for example, the top electrode can be prepared using the following method:

[0103] A top electrode layer 1406 and photoresist are deposited above the first interlayer dielectric layer 1210 and the magnetic tunnel junction 202. A patterned third photoresist 1211 is then formed by photolithography to obtain the desired result. Figure 23 The film structure shown; using a patterned third photoresist 1211 as a mask, the top electrode layer 1406 is etched to form the top electrode 1201, resulting in the film structure shown. Figure 24 The film structure shown is as follows: a second interlayer dielectric layer 1212 is deposited, and then CMP is used for surface planarization to obtain the film structure shown. Figure 25 The membrane structure shown.

[0104] S144. Deposit the bottom coil and current lines, and perform photolithography and etching to form the bottom coil and current lines.

[0105] Reference Figures 26-29 As shown, for example, the bottom coil and current line can be prepared using the following method:

[0106] A first metallic material layer 1407, such as aluminum (Al), is deposited over the second interlayer dielectric layer 1212 to obtain, as shown below. Figure 26 The film structure shown; photoresist is deposited on top of the first metal material layer 1407, and a patterned fourth photoresist 1213 is formed by photolithography, resulting in the film structure shown. Figure 27 The film structure shown; using a patterned fourth photoresist 1213 as a mask, the first metal material layer 1407 is etched to form current lines 2012 and bottom coils 1102, resulting in the film structure shown. Figure 28 The film structure shown; a third interlayer dielectric layer 1214 was deposited, and then CMP was used for surface planarization to obtain the film structure shown. Figure 29 The membrane structure shown.

[0107] S145. Seed layer deposition and electroplating are performed, followed by photolithography and etching to form the seed layer, current lines, and magnetic core.

[0108] Reference Figures 30-33 As shown, for example, the seed layer, current lines, and magnetic core can be prepared using the following method:

[0109] A seed layer 1210 was deposited above the third interlayer dielectric layer 1214 using deposition methods such as CVD and PVD to obtain the following... Figure 30 The film structure shown is as follows: photoresist is deposited above the seed layer 1210, and a patterned fifth photoresist 1215 is formed by photolithography. Then, an electroplating process is used to form a magnetic shielding structure 1205 and a magnetic core 2013. The electroplating material can be a nickel-iron alloy (NiFe), resulting in the desired film structure. Figure 31 The film structure shown is obtained by removing the fifth photoresist 1215 and then wet etching away the excess portion of the seed layer 1210 to obtain the film structure shown. Figure 32The film structure shown; a fourth interlayer dielectric layer 1216 was deposited, and then CMP was used for surface planarization to obtain the following result. Figure 33 The membrane structure shown.

[0110] S146. Perform through-hole etching, and perform photolithography and etching to form through-holes and top coils. Bottom coils, top coils, and through-holes constitute induction coils.

[0111] Reference Figures 34-37 As shown, for example, the induction coil can be prepared by the following method:

[0112] Through-hole positions are etched on both sides above the bottom coil 1102 to obtain the following: Figure 34 The film structure shown; a second metal material layer 1408 and photoresist are deposited, the second metal material layer 1408 being, for example, aluminum (Al), and a patterned sixth photoresist 1217 is formed by photolithography to obtain the film structure shown. Figure 35 The film structure shown; using a patterned sixth photoresist 1217 as a mask, the second metal material layer 1408 is etched to form the top coil 1101 and the through hole 1103, resulting in the film structure shown. Figure 36 The film structure shown; a passivation protective layer 1217 is deposited to obtain the following... Figure 37 The membrane structure shown.

[0113] The method for fabricating the tunnel magnetoresistive sensor in this application is used to fabricate the tunnel magnetoresistive sensor described in the aforementioned embodiments. This tunnel magnetoresistive sensor uses a fluxgate gate 201 and multiple magnetic tunnel junctions 202 to jointly detect an external magnetic field. The fluxgate gate 201 acts as the input preamp, modulating the external magnetic field to be detected into a high-frequency signal. This high-frequency signal is output as a short-circuit current signal. The high-frequency short-circuit current signal is then converted into a voltage signal by the multiple magnetic tunnel junctions 202. This approach avoids the direct processing of low-frequency signals by the multiple magnetic tunnel junctions 202, thus avoiding the problem of low low-frequency resolution. It also possesses the advantages of the fluxgate gate 201 in short-circuit current output mode, such as high cutoff frequency, high resolution, and miniaturization. This solves the problems of low cutoff frequency in the traditional open-circuit voltage output mode and the need for multiple turns of coil in this mode, which is detrimental to miniaturization. Furthermore, using a voltage signal for output facilitates practical application in real-world products.

[0114] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0115] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A tunnel magnetoresistive sensor, characterized in that, include: A fluxgate and multiple magnetic tunnel junctions are provided, wherein the induction coil of the fluxgate is short-circuited and connected via a current line, and the current line and the multiple magnetic tunnel junctions are arranged adjacent to each other. The fluxgate is used to convert the magnetic signal of the sensed external magnetic field into a current signal; The plurality of magnetic tunnel junctions are used to convert the magnetic signal generated by the induced current signal into a voltage signal.

2. The tunnel magnetoresistive sensor according to claim 1, characterized in that, The plurality of magnetic tunnel structures are configured as a full-bridge circuit or a half-bridge circuit, and each arm of the full-bridge circuit or the half-bridge circuit includes a magnetic tunnel junction, or includes a plurality of magnetic tunnel junctions connected in series, in parallel or in a mixed manner. The two half-bridges in the full-bridge circuit are connected in parallel between the power supply and the ground point, and the midpoint of each of the two half-bridges is the two output terminals of the voltage signal; or, the half-bridge circuit is connected between the power supply and the ground point, and the two ends of the first or second bridge arm of the half-bridge circuit are the two output terminals of the voltage signal; in the full-bridge circuit or the half-bridge circuit, the first bridge arm of each half-bridge is connected to the power supply, and the second bridge arm is connected to the ground point.

3. The tunnel magnetoresistive sensor according to claim 2, characterized in that, When the reference layer pinning directions of the multiple magnetic tunnel junctions are the same, the directions of the current signals corresponding to the magnetic signals sensed by the first and second arms of the same half-bridge are different.

4. The tunnel magnetoresistive sensor according to claim 3, characterized in that, When the multiple magnetic tunnel structures form a full-bridge circuit, the directions of the current signals corresponding to the magnetic signals sensed by the first bridge arm of each of the two half-bridges are different; the directions of the current signals corresponding to the magnetic signals sensed by the second bridge arm of each of the two half-bridges are different.

5. The tunnel magnetoresistive sensor according to claim 2, characterized in that, When the reference layer pinning directions of the magnetic tunnel junctions of the first and second arms of the same half-bridge are different, the directions of the current signals corresponding to the magnetic signals induced in the first and second arms of the same half-bridge are the same.

6. The tunnel magnetoresistive sensor according to claim 5, characterized in that, When the multiple magnetic tunnel structures are configured as a full-bridge circuit: When the reference layer pinning directions of the magnetic tunnel junctions of the first arms of the two half-bridges are different, the magnetic signals induced by the two half-bridges correspond to the same current signals. When the reference layer pinning direction of the magnetic tunnel junction of the first arm of each of the two half-bridges is the same, the directions of the current signals corresponding to the magnetic signals induced by the two half-bridges are different.

7. The tunneling magnetoresistive sensor according to any one of claims 3, 4, or 6, characterized in that, The current lines consist of multiple segments with different routing directions.

8. The tunnel magnetoresistive sensor according to claim 7, characterized in that, The current lines are routed in a bow-shaped or U-shaped pattern.

9. The tunnel magnetoresistive sensor according to any one of claims 1-6, characterized in that, The number of fluxgates is one or more, and each fluxgate corresponds to a set of magnetic tunnel junctions, wherein the set of magnetic tunnel junctions is the plurality of magnetic tunnel junctions; Each fluxgate is used to convert the magnetic signal of an external magnetic field sensed in a preset direction into a current signal, wherein the preset direction is consistent with the direction of the magnetic core of the fluxgate.

10. The tunnel magnetoresistive sensor according to any one of claims 1-6, characterized in that, The plurality of magnetic tunnel junctions and the current lines are arranged within the shielding range of the magnetic shielding structure, which is used to shield the external magnetic field.

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