Current sensor structure based on tunnel junction magnetic resistance and manufacturing method

Abstract

The invention discloses a current sensor structure based on tunnel junction magnetoresistance and a manufacturing method, the current sensor structure comprises a first array group and a second array group, and the first array group and the second array group are composed of a first tunnel junction magnetoresistance array unit and a second tunnel junction magnetoresistance array unit which are arranged along the same sensing direction, and a first electrode unit and a second electrode unit; the sensitive axis directions of the first array group and the second array group are opposite to each other, and the second array group rotates by 180 degrees relative to the first array group in the physical space and then is in cross connection through metal electrodes. The tunnel junction magnetoresistive sensor has the beneficial effects that the tunnel junction magnetoresistive sensor comprises the first array group and the second array group, and the first tunnel junction magnetoresistive array unit and the second tunnel junction magnetoresistive array unit in the first array group and the second array group respectively comprise eight arrays, so that the tunnel junction magnetoresistive sensor has higher physical reliability and stability; the measurement error of the tunnel junction magnetoresistive sensor caused by the magnetic field gradient can be reduced; when the magnetic field and the current are measured, the magnetic field with the magnitude as low as 17 nT / Hz can be measured.

Description

Technical Field

[0001] This invention relates to the field of power equipment measurement, and in particular to a current sensor structure and manufacturing method based on tunnel junction magnetoresistance. Background Technology

[0002] Currently, the commonly used current monitoring equipment in power systems is the capacitive voltage transformer (CVT). It is large in size, has high insulation costs, narrow measurement frequency band, and requires power outage and contact installation with primary side equipment. This contradicts the fact that it is widely installed on lines and towers, making it impossible to perform big data identification based on this equipment.

[0003] In current measurement, a limited number of non-contact current sensors are not yet widely deployed at various nodes of power grid lines. Tunnel junction magnetoresistive (TJ) current sensors, as a typical type of non-contact current sensor, can convert the magnetic field signal generated by the current into an electrical signal, thereby detecting the current intensity. The working principle of this device is based on the tunneling effect of spin electrons; the magnitude of the magnetoresistive reluctance changes with the applied magnetic field. However, the inventors have discovered at least the following problems in related technologies: for the measurement of weak currents, the position of the TJ magnetoresistive reluctance leads to a deviation in the perceived magnetic field / current position, and the sensitivity of magnetoresistive sensors is relatively low. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that there is a deviation in the sensing magnetic field / current position in weak current measurement, and the sensitivity of magnetoresistive sensors is low.

[0005] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a current sensor structure based on tunnel junction magnetoresistive (TJM), which includes a first array group and a second array group. The first array group and the second array group are composed of a first TJM magnetoresistive array unit and a second TJM magnetoresistive array unit arranged along the same sensing direction, as well as a first electrode unit and a second electrode unit.

[0006] The sensitive axes of the first array group and the second array group are opposite to each other, and the second array group is physically rotated 180° relative to the first array group and then cross-connected by metal electrodes, so that the first array group and the second array group together form a Wheatstone bridge.

[0007] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistive (TJM) of the present invention: the first TJM magnetoresistive array unit and the second TJM magnetoresistive array unit undergo two-step vertical magnetic field annealing, wherein:

[0008] The first annealing step was performed at 350°C in a 6.5 kOe magnetic field along the sensing direction for 1 hour.

[0009] The second annealing step involves annealing at 220°C in an 8kOe magnetic field perpendicular to the sensing direction for 0.5 hours.

[0010] The magnetic moment of the free layer of the tunnel junction remains perpendicular to the magnetic moment of the reference layer.

[0011] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistive (TJM) of the present invention: the first TJM magnetoresistive array unit sequentially includes a first tunnel array, a second tunnel array, a third tunnel array, a fourth tunnel array, a fifth tunnel array, a sixth tunnel array, a seventh tunnel array, and an eighth tunnel array. The first tunnel array and the fourth tunnel array, the fifth tunnel array and the eighth tunnel array are connected by metal electrodes, and the second tunnel array and the third tunnel array, the sixth tunnel array and the seventh tunnel array are connected by metal electrodes.

[0012] The second tunnel junction magnetoresistive array unit sequentially includes a second tunnel first array, a second tunnel second array, a second tunnel third array, a second tunnel fourth array, a second tunnel fifth array, a second tunnel sixth array, a second tunnel seventh array, and a second tunnel eighth array. The second tunnel first array, the second tunnel fourth array, the second tunnel fifth array, and the second tunnel eighth array are connected by metal electrodes. The second tunnel second array, the second tunnel third array, the second tunnel sixth array, and the second tunnel seventh array are connected by metal electrodes.

[0013] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistive power according to the present invention: the eight tunnel junction magnetoresistive arrays included in the first array group and the second array group have the same length, width and number of series and parallel connections, and the first tunnel first array in the first array group and the second tunnel eighth array in the second array group are in a collinear position.

[0014] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistive array of the present invention: the end of the first tunnel junction magnetoresistive array unit and the second tunnel junction magnetoresistive array unit closer to the first electrode unit and the second electrode unit is A, and the end farther away from the first electrode unit and the second electrode unit is B, and the A ends of the first array group and the second array group are adjacent.

[0015] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistance described in this invention: the first tunnel first array and the first tunnel fourth array, the first tunnel fifth array and the first tunnel eighth array, the first tunnel second array and the first tunnel third array, the first tunnel sixth array and the first tunnel seventh array of the first array group are connected to the B end of the first electrode unit through metal electrodes, and the first tunnel fourth array and the first tunnel fifth array, the first tunnel third array and the first tunnel sixth array are connected to the A end of the first electrode unit through metal electrodes;

[0016] The second array group's second tunnel first array, second tunnel fourth array, second tunnel fifth array, second tunnel eighth array, second tunnel second array, second tunnel third array, second tunnel sixth array, and second tunnel seventh array are connected to the B end of the first electrode unit via metal electrodes, and the second tunnel fourth array, second tunnel fifth array, second tunnel third array, and second tunnel sixth array are connected to the A end of the second electrode unit via metal electrodes.

[0017] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistance described in this invention: the first electrode unit includes, from left to right, a first unit electrode one, a first unit electrode two, a first unit electrode three, a first unit electrode four, and a first unit electrode one;

[0018] The second electrode unit, from right to left, includes second unit electrode one, second unit electrode two, second unit electrode three, second unit electrode four, and second unit electrode one.

[0019] In a preferred embodiment of the current sensor structure based on tunnel junction magnetoresistance described in this invention: the first unit electrode 1 and the second unit electrode 1 are connected by a metal wire, the first unit electrode 2 and the second unit electrode 4 are connected by a metal wire, the first unit electrode 3 and the second unit electrode 3 are connected by a metal wire, and the first unit electrode 4 and the second unit electrode 2 are connected by a metal wire.

[0020] A method for fabricating a current sensor based on tunnel junction magnetoresistance, comprising:

[0021] S1: First, a high-vacuum magnetron sputtering equipment is used to sequentially deposit the multilayer thin films required for the tunnel junction magnetoresistive device. The multilayer thin film structure is: Ta(5) / Ru(10) / Ta(5) / Ru(10) / Ta(5) / Ru(10) / MnIr(7.5) / CoFe(2.5) / Ru(0.8) / CoFe(0.5) / CoFeB(3) / MgO(1.6) / CoFeB(3) / Ru(0.8) / Ru(10) / Ta(5) / Ru(5);

[0022] S2: Using photolithography and etching technology, the first array group and the second array group are constructed. After the tunnel junction magnetoresistive array is patterned, the top electrode is deposited and stripped to obtain the first electrode unit and the second electrode unit for connecting the first array group and the second array group.

[0023] S3: The tunnel junction magnetoresistive device is annealed in a high vacuum annealing furnace in two steps. The first annealing temperature is 350℃ and the annealing magnetic field is 6.5kOe. The second annealing temperature is 220℃ and the annealing magnetic field is 8kOe. Through annealing, the direction of the free layer magnetic moment of the tunnel junction magnetoresistive device is induced to be perpendicular to the direction of the reference layer magnetic moment.

[0024] S4: Rotate the second array group and the first array group 180° in space, and connect the corresponding first electrode unit and second electrode unit by gold wire bonding to realize the Wheatstone bridge structure connection of tunnel junction magnetoresistance, and package it into the chip.

[0025] In a preferred embodiment of the method for fabricating a current sensor based on tunnel junction magnetoresistive (TJM) of the present invention: a TJM magnetoresistive measurement platform is constructed to test the sensitivity and noise of the fabricated TJM magnetoresistive device. The TJM magnetoresistive measurement platform consists of a Helmholtz coil (magnetic field generator), a low-noise differential amplifier, an oscilloscope, a current source (magnetic field drive), a TJM magnetoresistive sensor, and a PC. The low-noise differential amplifier amplifies the signal from the TJM magnetoresistive sensor to reduce the measurement error of the oscilloscope. The oscilloscope acquires the output voltage level of the TJM magnetoresistive sensor under different magnetic fields and also acquires the time-domain level of the TJM magnetoresistive sensor. The voltage noise spectral density is obtained by Fourier decomposition using the PC.

[0026] The noise level is calculated from the voltage noise spectral density and sensitivity of the tunnel junction magnetoresistive sensor. The sensitivity is the linear fitting coefficient between the output voltage and the magnetic field of the tunnel junction magnetoresistive sensor within the linear range, with the unit being V / T. The voltage noise spectral density is the frequency domain signal obtained after Fourier decomposition of the time domain signal collected by the tunnel junction magnetoresistive sensor, with the unit being V / √Hz. The magnetic field detection capability is obtained by dividing the voltage noise spectral density by the sensitivity, with the unit being T / √Hz or nT / √Hz, where 1T / √Hz=109nT / √Hz.

[0027] The beneficial effects of this invention are as follows: This tunnel junction magnetoresistive sensor includes a first array group and a second array group. The first tunnel junction magnetoresistive array unit and the second tunnel junction magnetoresistive array unit in the first array group and the second array group each contain 8 arrays, which has higher physical reliability and stability and takes into account the harsh measurement environment. The first tunnel junction magnetoresistive array unit and the second tunnel junction magnetoresistive array unit belonging to different Wheatstone bridge arms are evenly distributed in space perpendicular to the sensing direction, which can reduce the measurement error of the tunnel junction magnetoresistive sensor caused by magnetic field gradient. It has good performance when measuring magnetic fields and currents and can measure magnetic fields as low as 17 nT / √Hz. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein:

[0029] Figure 1 This illustrates a current sensor structure based on tunnel junction magnetoresistance. Figure 1 ;

[0030] Figure 2 This illustrates a current sensor structure based on tunnel junction magnetoresistance. Figure 2 ;

[0031] Figure 3 A schematic diagram of a tunnel junction magnetoresistive sensor measurement platform is shown.

[0032] Figure 4 The results of the tunnel junction magnetoresistance detection capability are shown in the figure. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0034] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0035] Reference Figures 1-2This embodiment provides a current sensor structure based on tunnel junction magnetoresistive (TJM), including a first array group 1 and a second array group 2. The first array group 1 and the second array group 2 are composed of a first TJM magnetoresistive array unit 11 and a second TJM magnetoresistive array unit 21 arranged along the same sensing direction, as well as a first electrode unit 12 and a second electrode unit 22. The arrangement along the same sensing direction is the arrangement along the current magnetic field sensing direction.

[0036] The sensitive axes of the first array group 1 and the second array group 2 are opposite to each other. The second array group 2 is rotated 180° relative to the first array group 1 in physical space and then cross-connected by metal electrodes, so that the first array group 1 and the second array group 2 together form a Wheatstone bridge. By rotating 180° and cross-connecting, the magnetic field responses of the first array group 1 and the second array group 2 complement each other and cancel each other out, avoiding measurement errors caused by spatial position differences. In addition, the Wheatstone bridge structure combines the two sets of first array group 1 and second array group 2 with opposite sensitive axes, and the differential output enhances the signal.

[0037] In use, the first array group 1 and the second array group 2 form a highly symmetrical Wheatstone bridge through the reverse sensitive axis design, spatial rotation and cross connection, which solves the error problem caused by position deviation in traditional tunnel junction sensors and realizes high sensitivity and low noise non-contact current measurement.

[0038] Reference Figures 1-2 As an optional embodiment, the first tunnel junction magnetoresistive array unit 11 is located in the first array group 1, with the sensitive axis direction denoted as +x (sensing direction), and the second tunnel junction magnetoresistive array unit 21 is located in the second array group 2, with the sensitive axis direction denoted as -x (rotation 180° direction). The first tunnel junction magnetoresistive array unit 11 and the second tunnel junction magnetoresistive array unit 21 undergo two steps of vertical magnetic field annealing, wherein:

[0039] The first annealing step is carried out at 350°C in a 6.5 kOe magnetic field along the sensing direction for 1 hour. The magnetic field strength is 6.5 kOe and the direction of the magnetic field is along the sensing direction. The purpose of this step is to lock the magnetic moment of the reference layer in the +x direction at high temperature; the free layer is temporarily polarized to +x to pre-orient it for subsequent verticalization.

[0040] The second annealing step involves annealing at 220°C in an 8kOe magnetic field perpendicular to the sensing direction for 0.5 hours. The magnetic field strength is 8kOe, and its direction is perpendicular to the sensing direction. Lowering the temperature allows the free layer to be reoriented at a smaller temperature. The 8kOe field overcomes the anisotropy of the free layer, causing its magnetic moment to align perpendicular to the sensing direction. The reference layer exhibits high thermal stability, and its magnetic moment remains unchanged at +x (sensing direction).

[0041] The magnetic moment of the free layer in the tunnel junction remains perpendicular to the magnetic moment of the reference layer. Perpendicular magnetization can improve the resolution of microcurrents.

[0042] Preferably, the first tunnel junction magnetoresistive array unit 11 sequentially includes a first tunnel first array 111, a first tunnel second array 112, a first tunnel third array 113, a first tunnel fourth array 114, a first tunnel fifth array 115, a first tunnel sixth array 116, a first tunnel seventh array 117, and a first tunnel eighth array 118. The first tunnel first array 111 and the first tunnel fourth array 114, the first tunnel fifth array 115, and the first tunnel eighth array 118 are connected by metal electrodes. The first tunnel second array 112 and the first tunnel third array 113, the first tunnel sixth array 116, and the first tunnel seventh array 117 are also connected by metal electrodes. This connection is to simultaneously satisfy the requirements of two equal-resistance half-bridges for a Wheatstone bridge; automatic cancellation of gradient magnetic fields; and differential output with the mirrored second array group.

[0043] The second tunnel junction magnetoresistive array unit 21 sequentially includes a second tunnel first array 211, a second tunnel second array 212, a second tunnel third array 213, a second tunnel fourth array 214, a second tunnel fifth array 215, a second tunnel sixth array 216, a second tunnel seventh array 217, and a second tunnel eighth array 218. The second tunnel first array 211, the second tunnel fourth array 214, the second tunnel fifth array 215, and the second tunnel eighth array 218 are connected by metal electrodes. The second tunnel second array 212, the second tunnel third array 213, the second tunnel sixth array 216, and the second tunnel seventh array 217 are also connected by metal electrodes. The purpose of these connections is the same as that of the first tunnel junction magnetoresistive array unit 11.

[0044] Preferably, the eight tunnel junction magnetoresistive arrays contained in the first array group 1 and the second array group 2 have the same length, width, and number of series and parallel connections to satisfy geometric identity. The length L, width W, and number of series turns N of a single subarray are completely identical, and the resistance value R = ρ·L / (W·t) error is <±1%, which provides a basis for subsequent Wheatstone bridge zero-point balancing. When the first array group 1 and the second array group 2 are at the same temperature and the same far-field interference, the common-mode signal is canceled by the differential amplifier because R and TCR (temperature coefficient of resistance) are exactly the same. Moreover, the first tunnel first array 111 in the first array group 1 and the second tunnel eighth array 218 in the second array group 2 are collinear. The collinearity of the first tunnel first array 111 and the second tunnel eighth array 218 in the second array group 2 is the final guarantee for gradient magnetic field cancellation and lead symmetry.

[0045] Preferably, the first tunnel junction magnetoresistive array unit 11 and the second tunnel junction magnetoresistive array unit 21 are close to each other.

[0046] One end of the first electrode unit 12 and the second electrode unit 22 is A, and the end away from the first electrode unit 12 and the second electrode unit 22 is B. The A ends of the first array group 1 and the second array group 2 are adjacent.

[0047] Furthermore, the first tunnel array 111 and the first tunnel arrays 114, 115 and 118, 112 and 113, 116 and 117 of the first array group 1 are connected to the B end of the first electrode unit 12 via metal electrodes, and the first tunnel arrays 114 and 115, 113 and 116 are connected to the first electrode unit 12 via metal electrodes. At end A, the first array 111, the fourth array 114, the fifth array 115, and the eighth array 118 of the first tunnel form a continuous long strip bridge arm one, and the second array 112, the third array 113, the sixth array 116, and the seventh array 117 of the first tunnel form another long strip bridge arm two. The fourth array 114, the fifth array 115, the third array 113, and the sixth array 116 of the first tunnel are "jumped" in the metal layer to form two "common nodes" of the bridge.

[0048] The second array group 2 has the second tunnel first array 211, the second tunnel fourth array 214, the second tunnel fifth array 215, the second tunnel eighth array 218, the second tunnel second array 212, the second tunnel third array 213, the second tunnel sixth array 216, and the second tunnel seventh array 217 connected to the B end of the first electrode unit 12 via metal electrodes. The second tunnel fourth array 214, the second tunnel fifth array 215, the second tunnel third array 213, and the second tunnel sixth array 216 connected to the A end of the second electrode unit 22 via metal electrodes. The second array group 2 has the same bridge arm as the first array group 1, except that it is physically rotated by 180°.

[0049] Preferably, the first electrode unit 12 includes, from left to right, first unit electrode 121, first unit electrode 2 122, first unit electrode 3 123, first unit electrode 4 124 and first unit electrode 121. The first unit electrode 121 is listed twice in the first electrode unit 12, forming 5 pads that actually correspond to only 4 independent nodes. The first and last names are the same for mirror symmetrical wiring to reduce parasitic resistance difference.

[0050] The second electrode unit 22 includes, from right to left, the second unit electrode 1 221, the second unit electrode 222, the second unit electrode 3 223, the second unit electrode 4 224, and the second unit electrode 1 221. The second electrode unit 22 is the same as the first electrode unit 12, except that it is physically rotated by 180° and achieves the shortest gold wire bridging.

[0051] Furthermore, the first unit electrode 121 and the second unit electrode 221 are connected by a metal wire to form the common power node of the Wheatstone bridge. The shortest path of the same node of the two arrays is directly connected to eliminate common-mode drift caused by the difference in lead resistance. The first unit electrode 122 and the second unit electrode 224 are connected by a metal wire, shorting the negative terminal of the bridge arm of the first array group 1 to the positive terminal of the bridge arm of the second array group 2, forming half of the differential output. After the second array group 2 is rotated 180°, the physical order is reversed, and a cross connection must be used. To maintain the correct polarity of the bridge, the first unit electrode 3 123 and the second unit electrode 3 223 are connected by a metal wire to form another common power supply node of the Wheatstone bridge. Symmetrical wiring ensures that the current paths of the two bridge arms are completely consistent, further reducing misalignment. The first unit electrode 4 124 and the second unit electrode 222 are connected by a metal wire to short-circuit the positive end of the first array group 1 bridge arm and the negative end of the second array group 2 bridge arm, forming the other half of the differential output. Similarly, due to the 180° rotation, cross wiring is required to maintain the differential polarity.

[0052] Reference Figures 3-4 As an optional embodiment,

[0053] S1: First, a high-vacuum magnetron sputtering apparatus is used to sequentially deposit the multilayer thin films required for the tunnel junction magnetoresistive device. The multilayer thin film structure is: Ta(5) / Ru(10) / Ta(5) / Ru(10) / Ta(5) / Ru(10) / MnIr(7.5) / CoFe(2.5) / Ru(0.8) / CoFe(0.5) / CoFeB(3) / MgO(1.6) / CoFeB(3) / Ru(0.8) / Ru(10) ) / Ta(5) / Ru(5), the thin film structure is 17 layers, the number in parentheses is in nm, Ta / Ru multilayer buffer, reduce surface roughness, improve MgO barrier tunneling rate, MnIr / CoFe / Ru / CoFeB synthesize antiferromagnetic, high pinning field, ensure that the reference layer magnetic moment does not degrade at 350℃, the double CoFeB-MgO-CoFeB structure obtains high TMR (tunneling magnetoresistance) and high electric field tolerance, supporting 17nT / √Hz noise substrate;

[0054] S2: Using photolithography etching technology, a first array group 1 and a second array group 2 are constructed. After the tunnel junction magnetoresistive array is patterned, a top electrode is deposited and stripped to obtain a first electrode unit 12 and a second electrode unit 22 for connecting the first array group 1 and the second array group 2. The tunnel junction magnetoresistive array pattern involves two key points: the eight tunnel junction magnetoresistive arrays contained in the first array group 1 and the second array group 2 have the same length, width, and number of series and parallel connections. The first electrode unit 12 includes, from left to right, a first unit electrode 121, a first unit electrode 222, a first unit electrode 3123, a first unit electrode 4124, and a first unit electrode 121. The second electrode unit 22 includes, from right to left, a second unit electrode 121, a second unit electrode 222, a second unit electrode 323, a second unit electrode 424, and a second unit electrode 121.

[0055] S3: The tunnel junction magnetoresistive device is annealed in a high-vacuum annealing furnace in two steps. The first annealing temperature is 350℃ and the annealing magnetic field is 6.5kOe. The second annealing temperature is 220℃ and the annealing magnetic field is 8kOe. Through annealing, the direction of the free layer magnetic moment of the tunnel junction magnetoresistive device is induced to be perpendicular to the direction of the reference layer magnetic moment. The order of temperature gradient and magnetic field cannot be changed, otherwise it is impossible to obtain both high pinning field and high sensitivity linear region at the same time.

[0056] S4: Rotate the second array group 2 and the first array group 1 by 180° in space, and connect the corresponding first electrode unit 12 and second electrode unit 22 by gold wire bonding to realize the Wheatstone bridge structure connection of tunnel junction magnetoresistance, and package it into the chip. Each step and each parameter of S1 to S4, its sequence, value, direction and connection method together constitute the process closed loop of "high symmetry Wheatstone bridge + gradient cancellation + common mode suppression", which directly determines the final device's magnetic field resolution capability of 17nT / √Hz and sub-milliampere non-contact current detection performance.

[0057] Preferably, a tunnel junction magnetoresistive (TJ) measurement platform is constructed to test the sensitivity and noise of the fabricated TJ magnetoresistive device. The TJ magnetoresistive measurement platform consists of a Helmholtz coil (magnetic field generator), a low-noise differential amplifier, an oscilloscope, a current source for the magnetic field drive, a TJ magnetoresistive sensor, and a PC. The Helmholtz coil provides a programmable uniform magnetic field of 0-±20mT with <0.1% non-uniformity. The current source for the magnetic field drive is programmable from 0-2A. The low-noise differential amplifier amplifies the signal from the TJ magnetoresistive sensor. The low-noise differential amplifier has a gain of 100-1000 times and input noise <1nV / √Hz@1kHz. The μV-level bridge output is amplified to the full scale of the oscilloscope to reduce measurement errors. The oscilloscope acquires the output voltage level of the TJ magnetoresistive sensor under different magnetic fields and also acquires the time-domain level of the sensor. The voltage noise spectral density is obtained by Fourier decomposition on the PC. The PC controls the magnetic field drive and completes data processing.

[0058] The noise level is calculated from the voltage noise spectral density and sensitivity of the tunnel junction magnetoresistive sensor. The sensitivity is the linear fitting coefficient between the output voltage and the magnetic field of the tunnel junction magnetoresistive sensor within the linear range, with the unit being V / T. The voltage noise spectral density is the frequency domain signal obtained after Fourier decomposition of the time domain signal collected by the tunnel junction magnetoresistive sensor, with the unit being V / √Hz. The magnetic field detection capability is obtained by dividing the voltage noise spectral density by the sensitivity, with the unit being T / √Hz or nT / √Hz, where 1T / √Hz=109nT / √Hz.

[0059] According to the appendix Figure 4 The experimental results show that the horizontal axis represents frequency f (Hz), and the vertical axis represents equivalent magnetic field noise B_noise, in nT / √Hz. This demonstrates that the measured magnetic fields are on the order of 17 nT / √Hz. Figure 4 The data is completely consistent with the "17nT / √Hz" indicator, and the spectrum shape conforms to the characteristics of a high-performance magnetoresistive sensor, verifying the effectiveness of the invented process.

[0060] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A current sensor structure based on tunnel junction magnetoresistance, characterized in that: include, The first array group (1) and the second array group (2) are composed of a first tunnel junction magnetoresistive array unit (11) and a second tunnel junction magnetoresistive array unit (21) arranged along the same sensing direction, as well as a first electrode unit (12) and a second electrode unit (22). The sensitive axes of the first array group (1) and the second array group (2) are opposite to each other, and the second array group (2) is rotated 180° relative to the first array group (1) in physical space and then cross-connected by metal electrodes, so that the first array group (1) and the second array group (2) together constitute a Wheatstone bridge.

2. The current sensor structure based on tunnel junction magnetoresistance according to claim 1, characterized in that: The first tunnel junction magnetoresistive array unit (11) and the second tunnel junction magnetoresistive array unit (21) undergo two steps of vertical magnetic field annealing, wherein: The first annealing step was performed at 350°C in a 6.5 kOe magnetic field along the sensing direction for 1 hour. The second annealing step involves annealing at 220°C in an 8kOe magnetic field perpendicular to the sensing direction for 0.5 hours. The magnetic moment of the free layer of the tunnel junction remains perpendicular to the magnetic moment of the reference layer.

3. The current sensor structure based on tunnel junction magnetoresistance according to claim 1, characterized in that: The first tunnel junction magnetoresistive array unit (11) sequentially includes a first tunnel first array (111), a first tunnel second array (112), a first tunnel third array (113), a first tunnel fourth array (114), a first tunnel fifth array (115), a first tunnel sixth array (116), a first tunnel seventh array (117), and a first tunnel eighth array (118). The first tunnel first array (111) and the first tunnel fourth array (114), the first tunnel fifth array (115) and the first tunnel eighth array (118) are connected by metal electrodes. The first tunnel second array (112) and the first tunnel third array (113), the first tunnel sixth array (116) and the first tunnel seventh array (117) are also connected by metal electrodes. The second tunnel junction magnetoresistive array unit (21) sequentially includes a second tunnel first array (211), a second tunnel second array (212), a second tunnel third array (213), a second tunnel fourth array (214), a second tunnel fifth array (215), a second tunnel sixth array (216), a second tunnel seventh array (217), and a second tunnel eighth array (218). The second tunnel first array (211), the second tunnel fourth array (214), the second tunnel fifth array (215), and the second tunnel eighth array (218) are connected by metal electrodes. The second tunnel second array (212), the second tunnel third array (213), the second tunnel sixth array (216), and the second tunnel seventh array (217) are connected by metal electrodes.

4. The current sensor structure based on tunnel junction magnetoresistance according to claim 3, characterized in that: The eight tunnel junction magnetoresistive arrays contained in the first array group (1) and the second array group (2) have the same length, width and number of series and parallel connections, and the first tunnel first array (111) in the first array group (1) and the second tunnel eighth array (218) in the second array group (2) are in a collinear position.

5. The current sensor structure based on tunnel junction magnetoresistance according to claim 3, characterized in that: The first tunnel junction magnetoresistive array unit (11) and the second tunnel junction magnetoresistive array unit (21) are located at the end closest to the first electrode unit (12) and the second electrode unit (22) as A, and at the end furthest from the first electrode unit (12) and the second electrode unit (22) as B. The A ends of the first array group (1) and the second array group (2) are adjacent.

6. The current sensor structure based on tunnel junction magnetoresistance according to claim 5, characterized in that: The first tunnel array 1 (111), the first tunnel array 4 (114), the first tunnel array 5 (115), the first tunnel array 8 (118), the first tunnel array 2 (112), the first tunnel array 3 (113), the first tunnel array 6 (116), and the first tunnel array 7 (117) of the first array group (1) are connected to the B end of the first electrode unit (12) through metal electrodes, and the first tunnel array 4 (114), the first tunnel array 5 (115), the first tunnel array 3 (113), and the first tunnel array 6 (116) are connected to the A end of the first electrode unit (12) through metal electrodes; The second tunnel first array (211), the second tunnel fourth array (214), the second tunnel fifth array (215), the second tunnel eighth array (218), the second tunnel second array (212), the second tunnel third array (213), the second tunnel sixth array (216), and the second tunnel seventh array (217) of the second array group (2) are connected to the B end of the first electrode unit (12) through metal electrodes, and the second tunnel fourth array (214), the second tunnel fifth array (215), the second tunnel third array (213), and the second tunnel sixth array (216) are connected to the A end of the second electrode unit (22) through metal electrodes.

7. The current sensor structure based on tunnel junction magnetoresistance according to claim 1, characterized in that: The first electrode unit (12) includes, from left to right, a first unit electrode one (121), a first unit electrode two (122), a first unit electrode three (123), a first unit electrode four (124), and a first unit electrode one (121); The second electrode unit (22) includes, from right to left, the second unit electrode one (221), the second unit electrode two (222), the second unit electrode three (223), the second unit electrode four (224), and the second unit electrode one (221).

8. The current sensor structure based on tunnel junction magnetoresistance according to claim 7, characterized in that: The first unit electrode (121) and the second unit electrode (221) are connected by a metal wire, the first unit electrode (122) and the second unit electrode (224) are connected by a metal wire, the first unit electrode (123) and the second unit electrode (223) are connected by a metal wire, and the first unit electrode (124) and the second unit electrode (222) are connected by a metal wire.

9. A method for fabricating a current sensor based on tunnel junction magnetoresistance, characterized in that: Based on the current sensor structure based on tunnel junction magnetoresistance according to any one of claims 1 to 8, the method includes: S1: First, a high-vacuum magnetron sputtering equipment is used to sequentially deposit the multilayer thin films required for the tunnel junction magnetoresistive device. The multilayer thin film structure is: Ta(5) / Ru(10) / Ta(5) / Ru(10) / Ta(5) / Ru(10) / MnIr(7.5) / CoFe(2.5) / Ru(0.8) / CoFe(0.5) / CoFeB(3) / MgO(1.6) / CoFeB(3) / Ru(0.8) / Ru(10) / Ta(5) / Ru(5); S2: Using photolithography etching technology, the first array group (1) and the second array group (2) are constructed. After the tunnel junction magnetoresistive array is patterned, the top electrode is deposited and stripped to obtain the first electrode unit (12) and the second electrode unit (22) for connecting the first array group (1) and the second array group (2). S3: The tunnel junction magnetoresistive device is annealed in a high vacuum annealing furnace in two steps. The first annealing temperature is 350℃ and the annealing magnetic field is 6.5kOe. The second annealing temperature is 220℃ and the annealing magnetic field is 8kOe. Through annealing, the direction of the free layer magnetic moment of the tunnel junction magnetoresistive device is induced to be perpendicular to the direction of the reference layer magnetic moment. S4: Rotate the second array group (2) and the first array group (1) 180° in space, and connect the corresponding first electrode unit (12) and second electrode unit (22) by gold wire bonding to realize the Wheatstone bridge structure connection of tunnel junction magnetoresistance, and package it into the chip.

10. The method for fabricating a current sensor based on tunnel junction magnetoresistance according to claim 9, characterized in that: A tunnel junction magnetoresistive (TJ) measurement platform was constructed to test the sensitivity and noise of the fabricated TJ magnetoresistive device. The platform consists of a Helmholtz coil (magnetic field generator), a low-noise differential amplifier, an oscilloscope, a current source (magnetic field drive), a TJ magnetoresistive sensor, and a PC. The low-noise differential amplifier amplifies the signal from the TJ magnetoresistive sensor to reduce the measurement error of the oscilloscope. The oscilloscope acquires both the output voltage level of the TJ magnetoresistive sensor under different magnetic fields and the time-domain level of the sensor. The PC then uses Fourier transform data to measure the signal. The voltage noise spectral density is obtained by decomposition. The noise level is calculated from the voltage noise spectral density and sensitivity of the tunnel junction magnetoresistive sensor. The sensitivity is the linear fitting coefficient between the output voltage and magnetic field of the tunnel junction magnetoresistive sensor within the linear range, with the unit being V / T. The voltage noise spectral density is the frequency domain signal obtained after Fourier decomposition of the time domain signal collected by the tunnel junction magnetoresistive sensor, with the unit being V / √Hz. The magnetic field detection capability is obtained by dividing the voltage noise spectral density by the sensitivity, with the unit being T / √Hz or nT / √Hz, where 1T / √Hz=109nT / √Hz.

Images