WO2014146570A1

WO2014146570A1 - Tmr half-bridge magnetic field gradient sensor chip for currency detector magnetic head

Info

Publication number: WO2014146570A1
Application number: PCT/CN2014/073637
Authority: WO
Inventors: 刘明峰; 白建军; 诸敏; 沈卫锋
Original assignee: 江苏多维科技有限公司
Priority date: 2013-03-18
Filing date: 2014-03-18
Publication date: 2014-09-25
Also published as: CN203133257U

Abstract

A TMR half-bridge magnetic field gradient sensor chip for a currency detector magnetic head, the sensing direction of the sensor chip being parallel to the surface thereof, and the surface thereof being perpendicular to the direction of the magnetic field generated by a back-bias magnet of the sensor chip; the TMR half-bridge magnetic field gradient sensor chip is installed above the back-bias magnet; the sensor chip comprises a magnetic bias structure, a half-bridge circuit, and input-output wiring terminals all integrated on the TMR half-bridge magnetic field gradient sensor chip; the input-output wiring terminals comprise a power source input terminal, a half-bridge output terminal and a grounding terminal respectively disposed on the half-bridge circuit comprising two bridge arms; the magnetic bias structure provides biasing for a magnetic tunnel junction (MTJ) in the half-bridge circuit, such that the half-bridge circuit operates in a linear area. The currency detector magnetic head has good manufacturability, sensitivity and anti-interference capability, and low costs.

Description

TMR half-bridge magnetic field gradient sensor chip for money detector head

Technical field

The invention relates to a sensor chip, in particular to a TMR half-bridge magnetic field gradient sensor chip with a magnetic tunneling resistance junction MTJ as an inductive component for a magnetic detector head.

Background technique

In daily life, the application of the currency detector is very extensive. For example, the vending machine head is required in equipment such as vending machines and money counters. At present, the magnetic head technology of the mainstream money detector uses a magnetic head with indium antimonide as a sensitive material, and the sensing direction is perpendicular to the detecting surface. When the banknote passes through the magnetic head, the magnetic field changes, and the change of the magnetic field is realized. Identification of the authenticity of banknotes. However, such a magnetic head has low sensitivity, low signal-to-noise ratio, large volume, poor temperature stability, and poor reliability.

The magnetic detector of the money detector with the magnetic tunneling resistance junction MTJ as the sensing element can effectively overcome the disadvantages of the above magnetic head. In the magnetic detector head with MTJ as the sensing element, components such as a magnetic field sensor chip, a signal processing circuit, a magnetic excitation element, an output pin, and a circuit board are included. The magnetic excitation element provides an excitation magnetic field that produces a magnetic field in a sensitive direction in the space under test, which is induced by the magnetic field sensor chip and converted into an electrical signal. After the electrical signal is converted by the signal processing circuit, it is transmitted to the output pin of the magnetic detector head through the circuit board.

The magnetic field sensor chip has a magnetic bias structure and a magnetoresistive element. The magnetic bias structure provides a bias magnetic field to operate the magnetoresistive element in a linear region, and the magnetoresistive element senses a change in an external magnetic field. The invention provides a TMR half-bridge magnetic field gradient sensor chip, which can be used as a magnetic field sensor chip in a magnetic head of a money detector, and has the characteristics of high sensitivity and strong manufacturability.

Summary of the invention

The magnetic detector head consists of a magnetic field sensor chip, a signal processing circuit, a magnetic back biasing component, an output pin, and a circuit board. The invention provides a half bridge magnetic field gradient sensor chip, which is a core component of a magnetic detector of a money detector, and has the advantages of high sensitivity, high signal to noise ratio, small volume, high temperature stability and high reliability, and is composed of a semiconductor base. A half bridge circuit composed of a sheet, a magnetic bias structure, a magnetoresistive element, and an electrical output terminal on the semiconductor substrate. The money detector made of the chip can replace the prior art money detector to improve the performance of the money detector.

The half-bridge circuit in the TMR half-bridge magnetic field gradient sensor chip is composed of an elliptical magnetic tunnel resistance junction MTJ, and the short-axis direction of the magnetic tunnel resistance junction MTJ is the sensing direction of the TMR half-bridge magnetic field gradient sensor chip. The supply voltage of the TMR half-bridge magnetic field gradient sensor chip is Vcc. If the magnetic field along the sensing direction of the TMR half-bridge magnetic field gradient sensor chip above the two magnetoresistive bridge arms is the same, the output voltage of the half bridge circuit is 0.5Vcc; If there is a gradient magnetic field along the sensing direction of the TMR half-bridge magnetic field gradient sensor chip above the half-bridge circuit, the output voltage of the half-bridge circuit will deviate from 0.5Vcc. The larger the gradient of the magnetic field, the more the output voltage of the half bridge circuit deviates from 0.5 Vcc. In the present invention, a plurality of magnetic tunneling resistor junctions MTJ are used in a series or parallel manner to form a bridge arm of the half bridge circuit, which can improve the sensitivity, signal to noise ratio and reliability of the TMR half bridge magnetic field gradient sensor chip.

The present invention achieves the above objectives by the following technical solutions:

A TMR half-bridge magnetic field gradient sensor chip for a money detector head, whose sensing direction is parallel to its surface, and whose surface is perpendicular to the direction of a magnetic field generated by a back bias magnet at the sensor chip. The TMR half bridge magnetic field gradient sensor The chip is mounted above the back bias magnet

The sensor chip includes a magnetic bias structure, a half bridge circuit, and an input and output terminal integrated on the TMR half bridge magnetic field gradient sensor chip;

The input/output terminal includes a power input end, a half bridge output end and a ground end respectively disposed on the half bridge circuit, and the power input end, the half bridge output end and the ground end respectively comprise at least one lead key Pad

The half bridge circuit includes

Two bridge arms, each of which is formed by one magnetoresistive unit or by two or more magnetoresistance units connected in parallel,

Each of the magnetoresistive units is composed of a magnetoresistive string or a series of two or more magnetoresistive strings.

Each of the magnetoresistive strings includes at least one magnetic tunneling resistance junction MTJ;

The magnetic biasing structure provides a bias to the magnetic tunneling resistor junction MTJ in the half-bridge circuit to operate the half-bridge circuit in the linear region.

Preferably, the two bridge arms are arranged along the sensing direction of the TMR half-bridge magnetic field gradient sensor chip, and the sensing directions of the two bridge arms are the same as the sensing direction of the TMR half-bridge magnetic field gradient sensor chip. The center distance between the two bridge arms is 50~1000 Micron.

Preferably, the magnetoresistive unit is arranged along a sensing direction perpendicular to the TMR half-bridge magnetic field gradient sensor chip, and a center distance between two adjacent magnetoresistive units is 200 to 800. Micron.

Preferably, the magnetoresistive strings are arranged along an induction direction perpendicular to the TMR half-bridge magnetic field gradient sensor chip, and a center-to-center distance between two adjacent magnetoresistive strings is 20 to 100 micrometers.

Preferably, the magnetic tunnel resistance junction MTJ is arranged along the sensing direction of the TMR half-bridge gradient sensor chip, and the center distance between two adjacent magnetic tunnel resistance junctions MTJ is 1-20. Micron.

Preferably, the magnetic tunneling resistance junction MTJ has an elliptical shape in plan view, and the ratio of the length of the long and short axes is greater than 3, and the short axis of the magnetic tunneling resistance junction MTJ is parallel to the TMR half-bridge magnetic field gradient sensor chip. The direction of sensing.

Preferably, in the absence of an applied magnetic field, the direction of the magnetic moment of the free layer in the magnetic tunneling resistance junction MTJ is directed to the direction of the easy axis of the free layer under the action of the magnetic biasing structure.

Preferably, the magnetic biasing structure integrated on the chip is a bulk or layered structure, and the material used may be an alloy containing Cr, Co, Pt, Pd, Ni or Fe.

Preferably, the magnetic biasing structure is composed of a permanent magnet integrated on the chip between two adjacent magnetoresistive strings, and the magnetization direction of the permanent magnet is perpendicular to the sensing of the TMR half-bridge magnetic field gradient sensor chip. direction.

Preferably, the magnetic biasing structure is composed of a magnetic thin film deposited on the magnetic tunneling resistance junction MTJ, and a magnetization direction of the magnetic thin film is perpendicular to an sensing direction of the TMR half-bridge magnetic field gradient sensor chip.

Preferably, the magnetic biasing structure is composed of an exchange layer deposited on the magnetic tunneling resistance junction MTJ, the exchange layer comprising an antiferromagnetic layer and a ferromagnetic layer weakly coupled to the antiferromagnetic layer And the magnetization direction of the ferromagnetic layer is perpendicular to the sensing direction of the TMR half-bridge magnetic field gradient sensor chip.

Preferably, each of the input and output terminals has two wire bonding pads, and the two wire bonding pads are located at two ends of the TMR half-bridge magnetic field gradient sensor chip, and a plurality of The chips are interconnected by wire bond pads to form a sensor chip combination, and the sensor chip combination has a sensing area larger than that of the single TMR half-bridge magnetic field gradient sensor chip.

Preferably, the wire bond pads have a length of 15 to 2000 microns and a width of 15 to 1000 microns.

Preferably, the components on the TMR half-bridge magnetic field gradient sensor chip are connected by electrical connection conductors, and the width of the electrical connection conductors is not less than 10 Micron.

Preferably, the TMR half-bridge magnetic field gradient sensor chip has a length of 500 to 3000 micrometers and a width of 200 to 1500 micrometers.

Compared with the prior art, the invention has the following beneficial effects: high manufacturability, high sensitivity, strong anti-interference ability and low cost.

The above description is only an overview of the technical solutions of the present invention, and the technical means of the present invention can be more clearly understood and can be implemented in accordance with the contents of the specification. Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific embodiments of the invention are given in detail by the following examples.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

1 is a schematic diagram of a TMR half bridge magnetic field gradient sensor chip 110.

2 is a schematic diagram of a connection method between two or more TMR half-bridge magnetic field gradient sensor chips 110.

3 is a schematic diagram of a magnetic biasing unit 111 composed of a first magnetic biasing method.

4 is a view showing the positional relationship between the magnetic tunnel resistance junction MTJ301 and the adjacent permanent magnet 303 in the first magnetic biasing method.

FIG. 5 is a schematic structural view of a magnetic tunnel resistance junction MTJ301 in the first magnetic bias method.

Figure 6 is a schematic illustration of a magnetic biasing unit 111 comprised of a second magnetic biasing method.

7 is a schematic diagram of a magnetic tunnel resistance junction MTJ601 in a second magnetic biasing method.

FIG. 8 is a schematic diagram of a magnetic tunnel resistance junction MTJ801 in a third magnetic biasing method.

Figure 9 is a cross-sectional view of a magnetoresistive string.

detailed description

The invention will be described in detail below with reference to the drawings in conjunction with the embodiments.

1 is a schematic diagram of a TMR half-bridge magnetic field gradient sensor chip 110. All components in the chip are located on a substrate 108. The substrate 108 may be made of a material such as silicon, ceramics, resin, or the like, which is an integrated circuit. In the present invention, a silicon substrate is used. . Two bridge arms 112 which are identical and arranged along the sensing direction of the TMR half-bridge magnetic field gradient sensor chip, serve as two bridge arms of the TMR half-bridge magnetic field gradient sensor chip 110, and have a certain center distance 107 between the two bridge arms. The center distance 107 can be adjusted between 50 microns and 1000 microns depending on the application environment. The bridge arm 112 is composed of five magnetoresistive units 111 connected in parallel. The TMR half-bridge magnetic field gradient sensor chip has three input and output terminals: power supply input Vcc, half-bridge output Vout and ground GND, and each terminal has two pads: power supply input Vcc includes pad 101 and pad 102, half bridge output Vout A pad 103 and a pad 104 are included, and the ground GND includes a pad 105 and a pad 106 as shown in FIG. In addition, the power input terminal Vcc may also include a pad 105 and a pad 106, and a half bridge output terminal Vout To include pad 103 and pad 104, ground GND is comprised of pad 101 and pad 102, which is not shown in FIG. Between the pad and the pad, between the pad and the bridge arm are connected by an electrical connection conductor 109 which is made of a material having a high electrical conductivity.

2 is a schematic diagram of a connection method of two or more TMR half-bridge magnetic field gradient sensor chips 110. Since each of the input and output terminals has two pads, the plurality of TMR half-bridge magnetic field gradient sensor chips 110 can be electrically interconnected by wire bonding, and 201 in the figure is an interconnection for wire bonding. line. By connecting a plurality of chips, the area of the sensing area can be increased.

3 is a first magnetic biasing method comprising a magnetoresistive unit 111, that is, a magnetic biasing structure composed of permanent magnets integrated on a chip between two adjacent magnetoresistive strings. A magnetic tunneling resistor junction MTJ301 can form a magnetoresistive string 302, or a plurality of magnetic tunneling resistor junctions MTJ301 can be connected in series or in parallel to form a magnetoresistive string 302. In this embodiment, the number of magnetic tunneling resistor junctions MTJ301 is twelve. The tunnel resistance junction MTJ301 is arranged along the sensing direction of the half bridge gradient sensor chip, wherein the center distance between the adjacent magnetic tunnel resistance junctions MTJ301 is 1-20 micrometers, which is 6 micrometers in this embodiment. A magnetoresistive string 302 may constitute a magnetoresistive unit 111, or a plurality of magnetoresistive strings 302 may be connected in series to form a magnetoresistive unit 111. In this embodiment, the number of magnetoresistive strings 302 is seven, and the magnetoresistive string 302 is vertical. Arranged in the direction of the sensing direction of the half bridge gradient sensor chip, wherein the center distance 305 between adjacent magnetoresistive strings is 20 to 100 micrometers, which is 54 micrometers in this embodiment. One magneto-resistance unit 111 may constitute one bridge arm 112, or a plurality of magneto-resistance units 111 may be connected in parallel to form one bridge arm 112. In this embodiment, the number of magnetoresistive units 111 is five, and the magnetoresistive unit 111 is perpendicular to the half. The direction of the sensing direction of the bridge gradient sensor chip is aligned. Between adjacent two magnetoresistive strings 302, there is a permanent magnet 303 integrated on the chip; an electrical connection 304 conductor made of a conductive material realizes an electrical connection between two adjacent magnetoresistive strings 302. The permanent magnet material may be an alloy containing Cr, Co, Pt, Pd, Ni or Fe.

Fig. 4 shows the positional relationship between the permanent magnet 303 and the magnetic tunnel resistance junction MTJ301 in the first magnetic biasing method. In the present design, the permanent magnet 303 and the magnetic tunneling resistance junction MTJ301 are alternately placed in a direction perpendicular to the sensing direction of the half-bridge gradient sensor chip, so that the magnetic tunneling resistance junction MTJ301 has permanent magnets 303 on both sides. The magnetic tunnel resistance junction MTJ301 has an elliptical top view shape. According to the shape anisotropy, the long axis 401 is the easy magnetization axis of the magnetic tunnel resistance junction MTJ301, and the short axis 402 is the hard magnetization axis of the magnetic tunnel resistance junction MTJ301. The magnetization direction of the permanent magnet 303 is as shown by a one-way arrow 403 in the figure, and the direction of the magnetic field generated by the permanent magnet 303 at the MTJ 301 is parallel to the long axis 401 of the MTJ 301 to reduce the hysteresis of the magnetic tunnel resistance junction MTJ301.

5 is a schematic structural view of the magnetic tunnel resistance junction MTJ301 of FIG. 4. The magnetic tunnel resistance junction MTJ301 is composed of a magnetic free layer 501, a tunnel barrier layer 502, a pinned layer 503, and an antiferromagnetic layer 504. The ratio of the lengths of the major axis and the minor axis of the magnetic tunneling resistance junction MTJ301 is greater than three, and the dimensions of the major axis 505 and the minor axis 506 in this embodiment are 10 micrometers and 1.5 micrometers, respectively. The tunnel barrier layer 502 is typically composed of MgO or Al2O3 and constitutes the majority of the resistance of the magnetic tunneling resistor junction MTJ301. The exchange coupling action of the antiferromagnetic layer 504 and the pinned layer 503 determines the magnetization direction of the pinned layer 503. In the present embodiment, the magnetization direction of the pinned layer 503 is parallel to the direction of the short axis 506. The magnetization direction of the magnetic free layer 501 is affected by the external magnetic field. When there is no external magnetic field, the magnetization direction of the magnetic free layer 501 is parallel to the magnetization direction 403 of the permanent magnet 303; when the banknote is close to the chip, in the banknote and the money detector head Under the action of the back magnet, the magnetization direction of the magnetic free layer 501 will change. According to the tunneling effect, the resistance of the magnetic tunneling resistance junction MTJ301 also changes, and after the signal conversion, the detection of the banknote can be realized.

6 is a second magnetic biasing method comprising a magnetic resistance unit 111, that is, a magnetic biasing structure is formed by a magnetic thin film deposited on a magnetic tunneling resistance junction MTJ, and a magnetic tunneling resistance junction MTJ601 can constitute a magnetic resistance string 602. Or a plurality of magnetic tunneling resistor junctions MTJ601 are connected in series or in parallel to form a magnetoresistive string 602. In this embodiment, the number of magnetic tunneling resistor junctions MTJ601 is twelve, and the magnetic tunneling resistor junction MTJ601 is along the sensing direction of the half bridge gradient sensor chip. Arrangement wherein the center distance between adjacent magnetic tunneling resistor junctions MTJ601 is 1-20 microns, which is 6 microns in this embodiment. A magnetoresistive string 602 constitutes a magnetoresistive unit 111, or a plurality of magnetoresistive strings 602 are connected in series to form a magnetoresistive unit 111. In this embodiment, the number of magnetoresistive strings 602 is seven, and the magnetoresistive string 602 is perpendicular to The direction of the sensing direction of the half bridge gradient sensor chip is such that the center distance 604 between adjacent magnetoresistive strings is 20 to 100 micrometers, which is 54 micrometers in this embodiment. A magnetoresistive unit 111 constitutes a bridge arm 112, or a plurality of magnetoresistive units 111 are connected in parallel to form a bridge arm 112. In this embodiment, there are five magnetoresistive units 111, and the magnetoresistive unit 111 is perpendicular to the half bridge gradient sensor chip. The directions of the sensing directions are arranged. An electrical connection conductor 603 composed of a conductive material realizes an electrical connection between two adjacent magnetoresistive strings 602.

7 is a schematic structural view of the magnetic tunnel resistance junction MTJ601 of FIG. 6. The magnetic tunnel resistance junction MTJ601 is composed of a magnetic thin film 701 constituting a magnetic bias structure, a magnetic free layer 702, a tunnel barrier layer 703, a pinned layer 704, and a reverse The ferromagnetic layer 705 is constructed. The ratio of the lengths of the major axis and the minor axis of the magnetic tunneling resistance junction MTJ601 is greater than three, and the dimensions of the major axis 707 and the minor axis 708 in this embodiment are 30 micrometers and 1.5 micrometers, respectively. The magnetization direction of the magnetic film 701 is perpendicular to the sensing direction of the TMR half-bridge magnetic field gradient sensor chip, parallel to the long axis direction of the magnetic tunnel resistance junction MTJ601. The magnetic field generated by the magnetic film 701 is parallel to the long axis direction of the magnetic tunnel resistance junction MTJ601, that is, its easy magnetization axis direction, for reducing the hysteresis thereof. The tunnel barrier layer 703 is usually composed of MgO or Al2O3 and constitutes most of the resistance of the magnetic tunnel resistance junction MTJ601. The exchange coupling of the antiferromagnetic layer 705 and the pinned layer 704 determines the magnetization direction of the pinned layer 704. In this embodiment, the magnetization direction of the pinned layer 704 is parallel to the direction of the minor axis 708. The magnetization direction of the magnetic free layer 702 is affected by the external magnetic field. When no external magnetic field is applied, the magnetization direction of the magnetic free layer 702 is parallel to the magnetization direction 706 of the magnetic film 701; when there are banknotes close to the chip, in the banknote and the money detector head Under the action of the back magnet, the magnetization direction of the magnetic free layer 702 will change. According to the tunneling effect, the resistance of the magnetic tunnel resistance junction MTJ601 also changes, and then the signal conversion can realize the detection of the banknote.

The magnetic thin film 701 in Fig. 7 can be replaced by an exchange working layer, and the MTJ element thus constructed is as shown in Fig. 8. The structure of the magnetoresistive unit composed of the method is the same as that of the magnetoresistive unit 111 in Fig. 6. The magnetic tunnel resistance junction MTJ810 is composed of an exchange active layer 800, a magnetic free layer 803, a tunnel barrier layer 804, a pinned layer 805, and an antiferromagnetic layer 806, wherein the exchange active layer 800 is composed of an antiferromagnetic layer 801 and an antiferromagnetic layer. The magnetic layer 801 is composed of a weakly coupled ferromagnetic layer 802, and the ferromagnetic layer 802 is located between the magnetic free layer 803 and the antiferromagnetic layer 801. The ratio of the lengths of the major axis and the minor axis of the magnetic tunneling resistance junction MTJ810 is greater than 3. In the present embodiment, the dimensions of the major axis 807 and the minor axis 808 are 30 micrometers and 1.5 micrometers, respectively. In the exchange coupling with the antiferromagnetic layer 801, the magnetization direction of the ferromagnetic layer 802 is perpendicular to the sensing direction of the TMR half-bridge magnetic field gradient sensor chip, parallel to the long axis direction of the magnetic tunneling resistance junction MTJ810, to reduce the hysteresis . The magnetization direction of the magnetic free layer 803 is affected by the external magnetic field. When there is no external magnetic field, the magnetization direction of the magnetic free layer 803 is parallel to the magnetization direction 809 of the ferromagnetic layer 802; when the banknote is close to the chip, the banknote and the money detector head are Under the action of the back magnet, the magnetization direction of the magnetic free layer 803 will change. According to the tunneling effect, the resistance of the magnetic tunnel resistance junction MTJ810 also changes, and then the signal conversion can realize the detection of the banknote.

Figure 9 is a cross-sectional view of a magnetoresistive string showing the connection between the magnetic tunneling resistor junctions MTJ901. The lower electrode 902 is located above the substrate 904 and is electrically connected to the bottom of the magnetic tunneling resistor junction MTJ901. The upper electrode 903 is electrically connected to the top of the magnetic tunneling resistor junction MTJ901. The upper and lower electrodes are alternately arranged in the direction of the sensing direction of the half-bridge gradient sensor chip, and thereby electrical interconnection between the magnetic tunnel resistance junctions MTJ901 in the magnetoresistive string is achieved.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

1. A TMR half-bridge magnetic field gradient sensor chip for a money detector head, whose sensing direction is parallel to its surface, and the surface is perpendicular to a magnetic field generated by a back bias magnet at the sensor chip. The TMR half bridge magnetic field gradient sensor A chip is mounted over the back biasing magnet and is characterized by:

The half bridge circuit includes two bridge arms, each of which is formed by one magnetoresistive unit or by two or more magnetoresistance units connected in parallel.

Each of the magnetoresistive units is composed of a magnetoresistive string or a series of two or more magnetoresistive strings, each of the magnetoresistive strings comprising at least one magnetic tunneling resistor junction MTJ;

2. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the two bridge arms are arranged along the sensing direction of the TMR half-bridge magnetic field gradient sensor chip, and the sensing directions of the two bridge arms The sensing direction is the same as that of the TMR half-bridge magnetic field gradient sensor chip, and the center distance between the two bridge arms is 50-1000 Micron.

3. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetoresistive unit is arranged along an induction direction perpendicular to the TMR half-bridge magnetic field gradient sensor chip, and two adjacent magnetoresistance units are The center distance between the two is 200-800 microns.

4. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetoresistive strings are arranged along an induction direction perpendicular to the TMR half-bridge magnetic field gradient sensor chip, and two adjacent magnetic resistance strings are arranged. The center distance between the two is 20-100 Micron.

5. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetic tunnel resistance junction MTJ is arranged along the sensing direction of the TMR half-bridge gradient sensor chip, and two adjacent magnetic tunnel resistance junctions MTJ. The center distance between them is 1-20 Micron.

6. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetic tunnel resistance junction MTJ has an elliptical shape in plan view, and a ratio of length to length of the minor axis is greater than 3, and the magnetic tunnel resistance is The short axis of the junction MTJ is parallel to the sensing direction of the TMR half-bridge magnetic field gradient sensor chip.

7. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetic moment direction of the free layer in the magnetic tunnel resistance junction MTJ is under the action of the magnetic bias structure when no external magnetic field is applied. Pointing to the easy axis of the free layer.

8. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetic bias structure integrated on the chip is a block or layer structure, and the material used is Cr, Co, Pt, Pd. , an alloy of Ni or Fe.

9. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetic bias structure is composed of a permanent magnet integrated on a chip between two adjacent magnetoresistive strings, and the permanent magnet The magnetization direction is perpendicular to the sensing direction of the TMR half-bridge magnetic field gradient sensor chip.

10. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein the magnetic bias structure is composed of a magnetic thin film deposited on the magnetic tunnel resistance junction MTJ, and a magnetization direction of the magnetic thin film is vertical The sensing direction of the TMR half-bridge magnetic field gradient sensor chip.

11. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein said magnetic bias structure is constituted by an exchange layer deposited on said magnetic tunnel resistance junction MTJ, said exchange layer comprising anti-iron a magnetic layer and a ferromagnetic layer weakly coupled to the antiferromagnetic layer, and a magnetization direction of the ferromagnetic layer is perpendicular to an induction direction of the TMR half bridge magnetic field gradient sensor chip.

12. The TMR half-bridge magnetic field gradient sensor chip of claim 1 wherein each of said input and output terminals has two wire bond pads, said two wire bond pads Located at two ends of the TMR half-bridge magnetic field gradient sensor chip, a plurality of chips are interconnected by wire bonding pads to form a sensor chip combination, and the sensor chip combination has a sensing area larger than that of a single TMR half-bridge magnetic field gradient sensor chip. Sensing area area.

13. The TMR half-bridge magnetic field gradient sensor chip of claim 1 wherein said wire bond pads have a length of 15-2000 microns and a width of 15-1000. Micron.

14. The TMR half-bridge magnetic field gradient sensor chip according to claim 1, wherein each element on the TMR half-bridge magnetic field gradient sensor chip is connected by an electrical connection conductor, and the width of the electrical connection conductor is not less than 10 Micron.

15. The TMR half-bridge magnetic field gradient sensor chip of claim 1 wherein said TMR half-bridge magnetic field gradient sensor chip has a length of 500-3000 microns and a width of 200-1500 microns.