WO2022183826A1

WO2022183826A1 - Magnetic sensor and manufacturing method therefor, and electronic device

Info

Publication number: WO2022183826A1
Application number: PCT/CN2021/143190
Authority: WO
Inventors: 赵海轮; 冷群文; 安琪; 邹泉波; 周汪洋; 丁凯文; 周良
Original assignee: 歌尔微电子股份有限公司
Priority date: 2021-03-01
Filing date: 2021-12-30
Publication date: 2022-09-09
Also published as: CN113030803A

Abstract

A magnetic sensor and a manufacturing method therefor, and an electronic device. The magnetic sensor comprises a substrate (20) and a plurality of magnetoresistive modules. The plurality of magnetoresistive modules are disposed on the substrate (20) and form a Wheatstone bridge. The side of each magnetoresistive module facing away from the substrate (20) is provided with at least one metal film sheet (400). The design of covering the sides of the magnetoresistive modules facing away from the substrate (20) with metal film sheets (400) can reduce the interference of an external magnetic field, and reduce the noise of the magnetic sensor.

Description

Magnetic sensor, preparation method of magnetic sensor, and electronic device

This application claims the priority of the Chinese patent application with application number 202110227059.4 filed on March 1, 2021, the entire contents of which are incorporated herein by reference.

technical field

The present application relates to the field of semiconductor technology, and in particular, to a magnetic sensor, a method for preparing the magnetic sensor, and an electronic device.

Background technique

Sensors are widely used in modern systems to measure or detect physical parameters such as position, motion, force, acceleration, temperature, pressure, etc. While the various types of sensors are used to measure these and other parameters, they all suffer from various limitations. For example, inexpensive low-field sensors like those used in electronic compasses and other similar magnetic sensing applications typically include anisotropic-based magnetoresistive (AMR) devices. In order to achieve the required sensitivity and suitable resistance for fusion with CMOS, the sensing element size of such a sensor is usually on the order of square millimeters. For mobile device applications, such AMR sensor configurations are expensive in terms of cost, board area, and power consumption. Other types of sensors, such as magnetic tunnel junction (MTJ) sensors and giant magnetoresistive (GMR) sensors, have been used to provide sensors in smaller configurations, but such sensors have their own shortcomings, such as less inspiration and affected by temperature changes. To address these issues, MTJ sensors and GMR sensors have been applied in a Wheatstone bridge structure to improve sensitivity and eliminate temperature-dependent resistance changes.

At present, in-plane X, Y dual-axis magnetic field sensors have been developed for electronic compasses, and the geomagnetic direction is detected by using the structure of a Wheatstone bridge. However, because this dual-axis magnetic field sensor needs to detect two different directions of X and Y, it is usually required that the two magnetic sensors have different pinning directions, and the pinning directions of the two magnetic sensors are at 90 degrees. The combination of magnetic sensors in the 90-degree pinning direction realizes in-plane X, Y dual-axis detection. The production process of the two magnetic sensors needs to be carried out on two different wafers. After the production is completed, the two wafers containing the magnetic sensor devices need to be annealed along the X and Y axes respectively, and finally separate X and Y wafers. The Y-axis magnetic sensor chip is combined together to realize the dual-axis detection of X and Y axes. Although the design of this magnetic sensor is simple, the manufacturing process is complicated and the manufacturing cost is high. For independent single-axis magnetic sensor chips, such as X-axis or Y-axis, a Wheatstone bridge structure is usually used to improve sensitivity and eliminate temperature-dependent resistance changes.

At present, the performance of the Wheatstone full-bridge magnetic sensor against external magnetic field interference is poor, and the free layer is easily damaged or fluctuated after being interfered by the external magnetic field. Thus, the final sensor output result has a large deviation.

technical problem

The main purpose of this application is to propose a magnetic sensor, a method for preparing the magnetic sensor, and an electronic device, aiming to solve the problem of poor resistance to external magnetic field interference of a Wheatstone full-bridge magnetic sensor.

technical solutions

To achieve the above purpose, the magnetic sensor proposed in this application includes:

substrate; and

a plurality of magnetoresistive modules, which are arranged on the substrate to form a Wheatstone bridge, and each of the magnetoresistive modules is provided with at least one metal on the side away from the substrate film sheet.

In an embodiment of the present application, the magnetic sensor further includes a first insulating layer, the first insulating layer is disposed on a side of the magnetoresistive module away from the substrate, and covers the metal thin film piece.

In an embodiment of the present application, the magnetoresistive module includes two first magnetoresistive module groups and two second magnetoresistive module groups, two first magnetoresistive module groups and two second magnetoresistive module groups The group forms a first Wheatstone bridge, the two first magnetoresistive module groups are respectively located at the first opposite bridge arms of the first Wheatstone bridge, and the two second magnetoresistive module groups are respectively located in the the second opposite arm of the first Wheatstone bridge;

The magnetization direction of the reference layer of the first magnetoresistive module group is the same as the positive direction of the first sensing axis of the magnetic sensor;

The second magnetoresistive module group includes two second magnetoresistive modules connected in series; the magnetization directions of the reference layers of the two second magnetoresistive modules form a first included angle, and the angle bisector of the first included angle is the same as the the first sensing axis is parallel; the first included angle is greater than 0° and less than 180°;

Wherein, the respective reference layer magnetization directions of the first magnetoresistive module group and the second magnetoresistive module are perpendicular to their respective easy magnetization axes.

In an embodiment of the present application, each of the first magnetoresistive module groups is formed by connecting M first magnetoresistive units in series; each of the second magnetoresistive modules is formed by connecting N second magnetoresistive units in series. M=2N; the shape of the first magnetoresistive unit and the second magnetoresistive unit are the same, and both are long-strip magnetoresistive film stacks; the easy magnetization axes of the M first magnetoresistive units are mutually parallel; the easy magnetization axes of the N second magnetoresistive units are parallel to each other;

The side of each of the first magnetoresistive unit and/or each of the second magnetoresistive unit facing away from the substrate is provided with a plurality of the metal thin film sheets spaced along the length direction.

In an embodiment of the present application, the magnetoresistive module further includes two third magnetoresistive module groups and two fourth magnetoresistive module groups, two third magnetoresistive module groups and two fourth magnetoresistive module groups The module group forms a second Wheatstone bridge, the two third magnetoresistive module groups are respectively located at the first opposite bridge arms of the second Wheatstone bridge, and the two fourth magnetoresistive module groups are respectively located at the second Wheatstone bridge. the second opposite bridge arm of the second Wheatstone bridge.

The magnetization directions of the reference layers of the adjacent third magnetoresistive module group and the fourth magnetoresistive module group form a second included angle, and the angle bisector of the second included angle is the first transmission line of the magnetic sensor. The sense axis is parallel; the second included angle is greater than 0° and less than 180°;

Wherein, the respective reference layer magnetization directions of the third magnetoresistive module group and the fourth magnetoresistive module group are perpendicular to their respective easy magnetization axes.

In an embodiment of the present application, each of the third magnetoresistive module groups is formed by connecting P third magnetoresistive units in series; each of the fourth magnetoresistive module groups is formed by connecting P fourth magnetoresistive units in series The shape of the third magnetoresistive unit and the fourth magnetoresistive unit are the same, and both are elongated magnetoresistive film stacks; the easy magnetization axes of the P third magnetoresistive units are parallel to each other; P The easy magnetization axes of the fourth magnetoresistive units are parallel to each other;

The side of each of the third magnetoresistive unit and/or each of the fourth magnetoresistive unit facing away from the substrate is provided with a plurality of the metal thin film sheets spaced along the length direction.

The present application also provides an electronic device, where the electronic device includes the magnetic sensor described in the above embodiments.

The present application also proposes a preparation method of a magnetic sensor, the preparation method comprising the following steps:

providing a substrate;

sequentially depositing several layers of thin films on the substrate to obtain a magnetoresistive film stack;

image-etching the magnetoresistive film stack to form a plurality of magnetoresistive modules;

preparing wires on the substrate, and connecting the magnetoresistive modules through the wires to form a Wheatstone bridge;

A metal thin film sheet is prepared on the side of the magnetoresistive module away from the substrate to form a semi-finished product of the magnetic sensor;

The semi-finished product of the magnetic sensor is placed in an external magnetic field and annealed in the external magnetic field.

In an embodiment of the present application, the step of preparing a metal thin film sheet on the side of the magnetoresistive module away from the substrate to form a semi-finished product of the magnetic sensor further includes:

A first insulating layer is prepared on the side of the magnetoresistive module away from the substrate, and the first insulating layer covers the metal thin film.

In an embodiment of the present application, the magnetic field direction of the external magnetic field is the same as the positive direction of the first sensing axis of the magnetic sensor.

beneficial effect

The technical solution of the present application provides a preparation basis through a substrate, and a plurality of the magnetoresistive modules are arranged on the substrate to form a Wheatstone bridge, which can improve the sensitivity of the magnetic sensor and eliminate temperature-related resistance changes. The design that the side of each magnetoresistive module away from the substrate is covered with a metal thin film sheet can reduce the interference of external magnetic fields and reduce the noise of the magnetic sensor.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained according to the structures shown in these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of an embodiment of a magnetic sensor of the present application;

FIG. 2 is a schematic structural diagram of another embodiment of the magnetic sensor of the present application;

3 is a schematic structural diagram of another embodiment of the magnetic sensor of the present application;

FIG. 4 is a schematic cross-sectional view of the magnetic sensor of the present application.

Description of reference numbers:

标号 label	名称 name	标号 label	名称 name
100 100	X轴磁场传感器 X-axis magnetic field sensor	110 110	第一磁阻模块组 The first magnetoresistive module group
111 111	第一磁阻单元 first magnetoresistive unit	120 120	第二磁阻模块组 The second magnetoresistive module group
121 121	第二磁阻模块 The second magnetoresistive module	122 122	第二磁阻单元 second magnetoresistive unit
200 200	Y轴磁场传感器 Y-axis magnetic field sensor	210 210	第三磁阻模块组 The third magnetoresistive module group
211 211	第三磁阻单元 The third magnetoresistive unit	220 220	第四磁阻模块组 The fourth magnetoresistive module group
221 221	第四磁阻单元 Fourth magnetoresistive unit	300 300	双轴磁场传感器 Dual axis magnetic field sensor
400 400	金属薄膜片 Metal thin film	500 500	引线 lead
10 10	磁阻膜堆 magnetoresistive film stack	20 20	衬底 substrate
30 30	第二绝缘层 second insulating layer	40 40	第一绝缘层 first insulating layer

The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Embodiments of the present invention

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

It should be noted that if there are directional indications (such as up, down, left, right, front, back, etc.) involved in the embodiments of the present application, the directional indications are only used to explain a certain posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly.

In addition, if there are descriptions related to "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for the purpose of description, and should not be construed as indicating or implying Its relative importance or implicitly indicates the number of technical features indicated. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In addition, the meaning of "and/or" appearing in the whole text includes three parallel schemes, and taking "A and/or B as an example", it includes scheme A, scheme B, or scheme that A and B satisfy at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of such technical solutions does not exist. , is not within the scope of protection claimed in this application.

The present application proposes a magnetic sensor.

In the embodiment of the present application, as shown in FIG. 1 , FIG. 2 and FIG. 3 , the magnetic sensor includes a substrate 20 and a plurality of magnetoresistive modules, and a plurality of the magnetoresistive modules are arranged on the substrate 20 , A Wheatstone bridge is formed, and at least one metal thin film 400 is provided on the side of each magnetoresistive module away from the substrate 20 .

In this embodiment, a substrate 20 is used to provide a preparation basis, and a plurality of the magnetoresistive modules are arranged on the substrate 20 to form a Wheatstone bridge, which can improve the sensitivity of the magnetic sensor and eliminate temperature-related resistance changes. The design of covering the metal film sheet 400 on the side of each magnetoresistive module away from the substrate 20 can reduce the interference of external magnetic fields and reduce the noise of the magnetic sensor.

The above-mentioned substrate 20 may be an insulating substrate 20 or a semiconductor substrate 20 . When it is a semiconductor substrate 20 , a second insulating layer 30 needs to be formed on the surface of the semiconductor substrate 20 . For example, the substrate 20 is a silicon substrate 20, and the surface of the silicon substrate 20 is thermally oxidized to form a second insulating layer 30, and the second insulating layer 30 is a silicon oxide insulating layer. After that, each thin film of the magnetoresistive module is deposited on the second insulating layer 30 .

Due to the shape anisotropy, the magnetoresistive module has a long axis (ie, easy magnetization axis) and a short axis (ie, difficult magnetization axis). In the specific implementation, the magnetoresistive module can be etched into a rectangle, a long hexagon or an ellipse, which can make the free layer easy to form a stable single magnetic domain shape, so that the shape anisotropy is strong enough to make it easy to form a stable single magnetic domain in the absence of an external magnetic field. In this case, the magnetization direction of the free layer is along its long axis direction (ie, along the easy magnetization axis direction). That is to say, when there is no external magnetic field, the angle formed between the magnetization directions of the respective free layers of the magnetoresistive modules and the magnetization directions of the respective reference layers is 90°.

In an embodiment of the present application, the magnetic sensor further includes a first insulating layer 40, the first insulating layer 40 is disposed on the side of the magnetoresistive module away from the substrate 20, and covers the The metal thin film sheet 400 is described.

It can be understood that, by arranging the first insulating layer 40, the magnetic sensor can be protected from static electricity, and it is not easy to be broken down by static electricity during testing or use. At the same time, the first insulating layer 40 also has the function of preventing the oxidation of the magnetoresistive module and the oxidation of the metal thin film 400, thereby preventing the performance of the magnetic sensor from being degraded and ensuring the stable performance of the magnetic sensor. The first insulating layer 40 also has the functions of waterproof and dustproof, which can improve the service life of the magnetic sensor.

In an embodiment of the present application, the magnetic sensor is a single-axis magnetic field sensor, and the first sensing axis is the X-axis. Therefore, the single-axis magnetic field sensor is the X-axis magnetic field sensor 100 .

As shown in FIG. 1 , the magnetoresistive module includes two first magnetoresistive module groups 110 and two second magnetoresistive module groups 120 , and two first magnetoresistive module groups 110 and two second magnetoresistive modules The group 120 forms a first Wheatstone bridge, the two first magnetoresistive module groups 110 are respectively located at the first opposite bridge arms of the first Wheatstone bridge, and the two second magnetoresistive module groups 120 are respectively a second opposite bridge arm of the first Wheatstone bridge;

The magnetization direction of the reference layer of the first magnetoresistive module group 110 is both the positive direction of the first sensing axis of the magnetic sensor (the direction indicated by the arrow in FIG. 1 , and the first sensing axis is hereinafter referred to as the X axis. )same;

The second magnetoresistive module group 120 includes two second magnetoresistive modules 121 connected in series; the magnetization directions of the reference layers of the two second magnetoresistive modules 121 form a first included angle, and the angle of the first included angle The bisector is parallel to the first sensing axis; the first included angle is greater than 0° and less than 180°;

Wherein, the respective reference layer magnetization directions of the first magnetoresistive module group 110 and the second magnetoresistive module 121 are perpendicular to their respective easy magnetization axes.

In this embodiment, the single-axis magnetic field sensor has a first sensing axis, which means that the single-axis magnetic field sensor responds to an external magnetic field that is not perpendicular to the first sensing axis, that is, when the single-axis magnetic field sensor is not perpendicular to the first sensing axis The output voltage under the external magnetic field is not equal to the output voltage without the external magnetic field. When designing each bridge arm resistance in the single-axis magnetic field sensor provided in this embodiment, those skilled in the art can set it according to the actual situation, as long as it is ensured that the output of the single-axis magnetic field sensor is not perpendicular to the first sensing axis under the external magnetic field The voltage is not equal to the output voltage when there is no external magnetic field.

The angle values of the first included angles formed by the magnetization directions of the reference layers of the two second magnetoresistive modules 121 in each second magnetoresistive module group 120 are equal.

The working principle of the X-axis magnetic field sensor 100 will be introduced below with reference to FIG. 1 :

When the direction of the external magnetic field is the positive direction of the X-axis, the respective free layer magnetization directions of the first magnetoresistive module group 110 and the second magnetoresistive module 121 will be deflected to be consistent with the direction of the external magnetic field, that is, the first magnetoresistive module group The angle between the magnetization direction of the free layer of 110 and the magnetization direction of the reference layer is reduced from 90° to 0°; the angle between the magnetization direction of the free layer and the magnetization direction of the reference layer of the second magnetoresistive module 121 is reduced from 90° to A/ 2 (where A is the angle value of the first included angle). The resistance of each bridge arm of the first relative bridge arm is decreasing, and the resistance of the second relative bridge arm is also decreasing, but the change ranges of the first relative bridge arm resistance and the second relative bridge arm resistance are inconsistent. At this time, the output voltage Vout of the first Wheatstone bridge is different from the output voltage Vout of the first Wheatstone bridge when there is no external magnetic field. Therefore, the X-axis magnetic field sensor 100 can induce an external magnetic field whose direction is the positive direction of the X-axis.

When the direction of the external magnetic field is the negative direction of the X-axis, the respective free layer magnetization directions of the first magnetoresistive module group 110 and the second magnetoresistive module 121 will be deflected to be consistent with the direction of the external magnetic field, that is, the first magnetoresistive module group The angle between the magnetization direction of the free layer of 110 and the magnetization direction of the reference layer is increased from 90° to 180°; the angle between the magnetization direction of the free layer and the magnetization direction of the reference layer of the second magnetoresistive module 121 is increased from 90° to (180° -A/2), the resistance of each bridge arm of the first relative bridge arm is increasing, and the resistance of the second relative bridge arm is also increasing, but the resistance changes of the first relative bridge arm and the second relative bridge arm are different. At this time, the output voltage Vout of the first Wheatstone bridge is different from the output voltage Vout of the first Wheatstone bridge when there is no external magnetic field. Therefore, the X-axis magnetic field sensor 100 can induce an external magnetic field whose direction is the negative direction of the X-axis.

When the direction of the external magnetic field is the Y-axis direction perpendicular to the X-axis, the magnetization direction of the free layer of the first magnetoresistive module group 110 does not deflect, that is, the resistance of each bridge arm in the first opposite bridge arm remains unchanged; The magnetization directions of the free layers of the two second magnetoresistive modules 121 on the same bridge arm are deflected to be consistent with the direction of the external magnetic field, that is: one of the two second magnetoresistive modules 121 on the same bridge arm The angle between the magnetization direction of the free layer of the module 121 and the magnetization direction of the reference layer is reduced from 90° to (90°-A/2), and the angle between the magnetization direction of the free layer and the magnetization direction of the reference layer of another second magnetoresistive module 121 is As the angle increases from 90° to (90°+A/2), it can be seen that the resistance changes of the two second magnetoresistive modules 121 on the same bridge arm are opposite, so that the resistance of each bridge arm in the second opposite bridge arm remains unchanged. At this time, the output voltage of the first Wheatstone bridge is the same as the output voltage of the first Wheatstone bridge when there is no external magnetic field. Therefore, the X-axis magnetic field sensor 100 does not induce an external magnetic field whose direction is the Y-axis direction.

In the technical solution provided in this embodiment, under the action of an external magnetic field perpendicular to the first sensing axis, the resistances of the two second magnetoresistive modules 121 on the same bridge arm of the second opposite bridge arms will produce opposite responses. Thereby keeping the bridge arm resistance unchanged. It can be seen that the uniaxial magnetic field sensor provided in this embodiment can keep the resistance of each bridge arm unchanged under the external magnetic field perpendicular to the first sensing axis, without the need to prepare a fixed resistance, which can reduce the complexity of the preparation process of the uniaxial magnetic field sensor .

In one embodiment, the magnetization direction of the reference layer of the second magnetoresistive module 121 forms an obtuse angle with the positive direction of the first sensing axis.

In another embodiment, the magnetization direction of the reference layer of the second magnetoresistive module 121 forms an acute angle with the positive direction of the first sensing axis.

In an embodiment of the present application, as shown in FIG. 1 , each of the first magnetoresistive module groups 110 is formed by connecting M first magnetoresistive units 111 in series; each of the second magnetoresistive modules 121 is composed of N second magnetoresistive units 122 are connected in series; M=2N; the first magnetoresistive unit 111 and the second magnetoresistive unit 122 have the same shape, and both are elongated magnetoresistive film stacks 10 ; M The easy magnetization axes of the first magnetoresistive units 111 are parallel to each other; the easy magnetization axes of the N second magnetoresistive units 122 are parallel to each other;

Each of the first magnetoresistive units 111 and/or each of the second magnetoresistive units 122 is provided with a plurality of the metal thin film sheets 400 spaced apart along the length direction on the side away from the substrate 20 .

In this embodiment, each of the first magnetoresistive units 111 and each of the second magnetoresistive units 122 is provided with a plurality of the metal thin films spaced along the length direction on the side away from the substrate 20 . slice 400.

In this embodiment, the first magnetoresistive units 111 are connected in series through the leads 500 , and the second magnetoresistive units 122 are connected in series through the leads 500 , and the leads 500 are metal leads.

It can be understood that, the Wheatstone full bridge of the X-axis magnetic field sensor 100 has two bridge arms using the structure of the long giant magnetoresistive film stack 10 with a certain included angle, which can realize resistance matching with other bridge arms to ensure When the external magnetic field of the magnetic sensor is 0, the output of the Wheatstone full bridge is 0, and the influence of the temperature change on the Wheatstone full bridge can be offset, so that the output will not drift with temperature.

At the same time, the design of M=2N can ensure that the low resistance state resistance value of the first magnetoresistive module group 110 is equal to the low resistance state resistance value of the second magnetoresistive module group 120; the first magnetoresistive module group The high resistance state resistance value of 110 is equal to the high resistance state resistance value of the second magnetoresistive module group 120 , that is, the resistance matching of each bridge arm can be realized, and the measurement accuracy can be improved. In this way, when there is no external magnetic field, the first Wheatstone bridge reaches equilibrium and the output voltage is zero. In this way, the calculation difficulty of subsequently calculating the direction of the external magnetic field can be reduced, and the measurement accuracy of the magnetic sensor can also be improved. In addition, the greater the number of magnetoresistive units on each bridge arm, the corresponding reduction in bridge noise, because the uncorrelated random behavior of each magnetoresistive unit is averaged out.

In an embodiment of the present application, the range of the first included angle A is greater than 0° and less than 100°. In this embodiment, the first included angle A is 90°.

In an embodiment of the present application, the magnetic sensor is a single-axis magnetic field sensor, the sensing axis of the single-axis magnetic field sensor is a second sensing axis, and the second sensing axis is perpendicular to the first sensing axis, that is, the first sensing axis The two sensing axes are the Y-axis, so the single-axis magnetic field sensor is the Y-axis magnetic field sensor 200 .

As shown in FIG. 2 , the magnetoresistive modules of the Y-axis magnetic field sensor 200 include two third magnetoresistive module groups 210 and two fourth magnetoresistive module groups 220 , two third magnetoresistive module groups 210 and two third magnetoresistive module groups 210 . The four magnetoresistive module groups 220 form a second Wheatstone bridge, the two third magnetoresistive module groups 210 are respectively located on the first opposite bridge arms of the second Wheatstone bridge, and the two fourth magnetoresistive The module groups 220 are respectively located at the second opposite bridge arms of the second Wheatstone bridge.

The magnetization directions of the reference layers of the adjacent third magnetoresistive module group 210 and the fourth magnetoresistive module group 220 form a second included angle, and the angle bisector of the second included angle is the same as the second angle of the magnetic sensor. A sensing axis is parallel, that is, perpendicular to the second sensing axis; the second included angle is greater than 0° and less than 180°;

Wherein, the magnetization directions of the reference layers of the third magnetoresistive module group 210 and the fourth magnetoresistive module group 220 are perpendicular to their respective easy magnetization axes.

In this embodiment, the single-axis magnetic field sensor has a second sensing axis, which means that the single-axis magnetic field sensor responds to an external magnetic field that is not perpendicular to the second sensing axis, that is, when the single-axis magnetic field sensor is not perpendicular to the second sensing axis The output voltage under the external magnetic field is not equal to the output voltage without the external magnetic field. When designing each bridge arm resistance in the single-axis magnetic field sensor provided in this embodiment, those skilled in the art can set it according to the actual situation, as long as it is ensured that the output of the single-axis magnetic field sensor is not perpendicular to the external magnetic field of the second sensing axis. The voltage is not equal to the output voltage when there is no external magnetic field.

The working principle of the Y-axis magnetic field sensor 200 will be introduced below with reference to FIG. 2 :

When the direction of the external magnetic field is the X-axis, the magnetization directions of the free layers of the first magnetoresistive module group 110 and the second magnetoresistive module group 120 are both deflected to be consistent with the direction of the external magnetic field, and the resistance of each bridge arm of the first opposite bridge arm When the resistance becomes smaller or larger, the resistance of the second opposite bridge arm also becomes larger or smaller. It can be seen that the resistance changes of the magnetoresistive modules on the two bridge arms are opposite, and the output voltage Vout of the second Wheatstone bridge is different from the output voltage Vout of the second Wheatstone bridge when there is no external magnetic field. Therefore, the Y-axis magnetic field sensor 200 can induce an external magnetic field whose direction is the Y-axis direction.

When the direction of the external magnetic field is the X-axis direction perpendicular to the Y-axis, the respective free layer magnetization directions of the first magnetoresistive module group 110 and the second magnetoresistive module group 120 are deflected to be consistent with the direction of the external magnetic field, and the first opposite bridge The resistance of each bridge arm of the arms is decreasing or increasing, and the resistance of the second opposite bridge arm is also decreasing or increasing. It can be seen that the resistance changes of the magnetoresistive modules on the two bridge arms are the same. At this time, the output voltage of the second Wheatstone bridge is the same as the output voltage of the second Wheatstone bridge when there is no external magnetic field. Therefore, the Y-axis magnetic field sensor 200 does not induce an external magnetic field whose direction is the X-axis direction.

In an embodiment of the present application, as shown in FIG. 2 , each of the third magnetoresistive module groups 210 is formed by connecting P third magnetoresistive units 211 in series; each of the fourth magnetoresistive module groups 220 It is formed by connecting P fourth magnetoresistive units 221 in series; the third magnetoresistive unit 211 and the fourth magnetoresistive unit 221 have the same shape, and both are long magnetoresistive film stacks 10 ; The easy magnetization axes of the third magnetoresistive units 211 are parallel to each other; the easy magnetization axes of the P fourth magnetoresistive units 221 are parallel to each other;

Each of the third magnetoresistive units 211 and/or each of the fourth magnetoresistive units 221 is provided with a plurality of the metal thin film sheets 400 spaced along the length direction on the side away from the substrate 20 .

It can be understood that, the above design can ensure that the low resistance state resistance value of the third magnetoresistive module group 210 is equal to the low resistance state resistance value of the fourth magnetoresistive module group 220; the third magnetoresistive module group The high-resistance state resistance value of 210 is equal to the high-resistance state resistance value of the fourth magnetoresistive module group 220 , that is, the resistance matching of each bridge arm can be realized, and the measurement accuracy can be improved. In this way, in the absence of an external magnetic field, the second Wheatstone bridge reaches equilibrium and the output voltage is zero. In this way, the calculation difficulty of subsequently calculating the direction of the external magnetic field can be reduced, and the measurement accuracy of the magnetic sensor can also be improved. In addition, the greater the number of magnetoresistive units on each bridge arm, the corresponding reduction in bridge noise, because the uncorrelated random behavior of each magnetoresistive unit is averaged out.

The design of the long magnetic film stack covering the metal thin film 400 at a certain distance can improve the shape anisotropy of the magnetic film stack while reducing the interference of external magnetic fields and the noise of the sensor.

In an embodiment of the present application, as shown in FIG. 3 , the magnetic sensor is a dual-axis magnetic field sensor 300, and the sensing axis of the dual-axis magnetic field sensor 300 includes a first sensing axis and a second sensing axis, The first sensing axis is the X axis, the second sensing axis is the Y axis, and the first sensing axis and the second sensing axis are perpendicular to each other. Therefore, the dual-axis magnetic field sensor 300 is the XY-axis magnetic field sensor 200 . The dual-axis magnetic field sensor 300 includes the above-mentioned X-axis magnetic field sensor 100 and Y-axis magnetic field sensor 200 .

The working principle of the dual-axis magnetic field sensor 300 will be described below with reference to FIG. 3 :

When the direction of the external magnetic field is parallel to the first sensing axis, the second Wheatstone bridge does not respond to the external magnetic field oriented parallel to the first sensing axis. The first Wheatstone bridge is responsive to an external magnetic field oriented in the positive direction of the first sensing axis.

When the direction of the external magnetic field is parallel to the second sensing axis, the second Wheatstone bridge can respond to the external magnetic field oriented parallel to the second sensing axis. The first Wheatstone bridge does not respond to external magnetic fields oriented parallel to the second sensing axis.

Therefore, in the dual-axis magnetic field sensor 300, under the action of the external magnetic field parallel to the second sensing axis, the second Wheatstone bridge responds, and the resistance of each bridge arm of the first opposite bridge arm of the first Wheatstone bridge remains unchanged. The resistance of the two second magnetoresistive modules 121 on the same bridge arm in the second opposite bridge arm of the first Wheatstone bridge will produce opposite responses, so that the resistance of each bridge arm of the second opposite bridge arm is kept unchanged. , that is, the first Wheatstone bridge has no response; under the action of an external magnetic field parallel to the first sensing axis, the second Wheatstone bridge has no response, and the first Wheatstone bridge has a response. It can be seen that the biaxial magnetic field sensor 300 can sense external magnetic fields in all directions in the plane, and does not need to prepare a fixed resistor, which can reduce the manufacturing process complexity of the biaxial magnetic field sensor 300 .

The present application also provides an electronic device, which includes the magnetic sensor described in the above embodiments. The specific structure of the magnetic sensor refers to the above-mentioned embodiments. Since the electronic device adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the functions brought by the technical solutions of the above-mentioned embodiments, and will not be repeated here. The electronic devices include but are not limited to mobile phones, smart watches, MP4 devices, head-mounted display devices, game controllers, and the like.

As shown in FIG. 4 , the present application also proposes a preparation method of a magnetic sensor, and the preparation method includes the following steps:

S100: providing a substrate 20;

S200: sequentially depositing several layers of thin films on the substrate 20 to obtain the magnetoresistive film stack 10;

In an embodiment of the present application, the step S200: sequentially depositing several layers of thin films on the substrate 20 to obtain the magnetoresistive film stack 10, including:

S210 : preparing the second insulating layer 30 on the surface of the substrate 20 through a rapid thermal oxidation process;

S220: sequentially depositing several layers of thin films on the second insulating layer 30 to obtain the magnetoresistive film stack 10;

In one embodiment, the film is a giant magnetoresistive film, and the giant magnetoresistive film is sequentially deposited on the upper surface of the silicon oxide insulating layer by a magnetron sputtering process to form a giant magnetoresistive film stack 10, and the giant magnetoresistive film stack 10 may be a GMR film The stack or TMR film stack, the thickness of the giant magnetoresistive film stack 10 is 30nm~40nm.

Generally, the magnetoresistive film stack 10 may include a seed layer, an antiferromagnetic pinning layer, a reference layer, a non-magnetic interlayer, an induced (ie, free layer), and a capping layer sequentially stacked from bottom to top. The specific structures and specific materials of each layer can be designed according to actual needs, which are not specifically limited in this application. For example: the antiferromagnetic pinning layer, the main material is IrMn, PtMn, FeMn; the reference layer, the main material is CoFe; the nonmagnetic spacer layer, the main material is Cu; the free layer, the main material is CoFe.

S300: performing image etching on the magnetoresistive film stack 10 to form a plurality of magnetoresistive modules;

In an embodiment of the present application, the step S300: performing image etching on the magnetoresistive film stack 10 to form a plurality of magnetoresistive modules, including:

S310: Coating photoresist on the side of the magnetoresistive film stack 10 away from the substrate 20, and transferring the pattern to the photoresist to form a pattern of the magnetoresistive film stack 10;

In this embodiment, a photoresist is spin-coated on the substrate on which the giant magnetoresistive film stack 10 is deposited, and the photoresist is pre-bake, exposed, post-bake, and developed, and the electrode pattern on the mask is transferred to the photolithography glue to form a pattern of giant magnetoresistive film stack 10 .

S320: Perform image etching according to the pattern of the magnetoresistive film stack 10 to form a plurality of magnetoresistive modules.

In this embodiment, the pattern of the giant magnetoresistive film stack 10 is etched by an ion beam etching process, and the etching thickness is 30-40 nm, and the first insulating layer 40 is over-etched.

S400: Prepare wires on the substrate 20, and connect the magnetoresistive modules through the wires to form a Wheatstone bridge;

Wires can be prepared by thermal evaporation, magnetron sputtering and other processes. In a specific implementation, a mask plate containing a wire pattern can be prepared in advance, and through the mask plate, a metal material is deposited by thermal evaporation or magnetron sputtering to prepare the wire.

S500: preparing a metal thin film sheet 400 on the side of the magnetoresistive module away from the substrate 20 to form a semi-finished product of a magnetic sensor;

In an embodiment of the present application, the step S500: preparing a metal thin film sheet 400 on the side of the magnetoresistive module away from the substrate 20 to form a semi-finished product of the magnetic sensor, which specifically includes:

S510 : making electrodes, which are connected to the Wheatstone bridge to output the Wheatstone bridge voltage.

S520: Prepare a metal thin film sheet 400 on the side of the magnetoresistive module away from the substrate 20 to form a semi-finished product of the magnetic sensor.

In this embodiment, after S320, a positive photoresist is coated, and the photoresist is pre-bake, exposed, post-bake, and developed, and a metal film is evaporated on the surface of the substrate by a coating process. The coating process can use a magnetron Sputtering process, electron beam evaporation process, etc., the film thickness is 200~300nm, and the metal film 400 can be Al, Cr, Ti, Au; then immersed in acetone and isopropanol successively, and can be combined with ultrasonic cleaning to carry out metal By stripping and removing the photoresist, electrodes and metal thin films 400 are fabricated.

S600: Place the semi-finished product of the magnetic sensor in an external magnetic field, and perform annealing treatment in the external magnetic field.

In an embodiment of the present application, step S600 specifically includes: annealing the finished semi-finished product in an annealing furnace, applying an external magnetic field during the annealing process, and the external magnetic field strength may be 0.1T~1T.

In an embodiment of the present application, the step of preparing a metal thin film sheet 400 on the side of the magnetoresistive module away from the substrate 20 to form a semi-finished product of the magnetic sensor further includes:

S700 : preparing the first insulating layer 40 on the side of the magnetoresistive module away from the substrate 20 , and covering the metal thin film 400 with the first insulating layer 40 .

In this embodiment, the inductively coupled plasma-chemical vapor deposition process is used to deposit the first insulating layer 40 . The first insulating layer 40 may be silicon nitride or silicon oxide, and the thickness of the first insulating layer 40 is 200-300 nm.

In an embodiment of the present application, after the step S700 and before the step S600, the method further includes: coating a positive photoresist, pre-baking, exposing, post-baking, and developing the photoresist, using reactive ion etching (RIE) ) process etching exposed first insulating layer 40, the reaction temperature is 20 ~ 35 ° C, etched to the electrode where the layer stops, and then soaked in acetone, isopropanol solvent to remove the photoresist, exposing the electrode test area.

The manufacturing method has a simple manufacturing process, and can manufacture a dual-axis magnetic sensor on the same wafer. Through one film stack deposition, a simple manufacturing process, and a single annealing process, the manufacturing cost is low, and two sensor chips with different sensing directions can be realized. The production of X, Y axis dual-axis detection.

The above descriptions are only optional embodiments of the present application, and are not intended to limit the scope of the patent of the present application. Under the inventive concept of the present application, any equivalent structural transformation made by using the contents of the description and drawings of the present application, or direct/indirect Applications in other related technical fields are included in the scope of patent protection of this application.

Claims

A magnetic sensor, wherein the magnetic sensor comprises:

substrate; and

a plurality of magnetoresistive modules, which are arranged on the substrate to form a Wheatstone bridge, and each of the magnetoresistive modules is provided with at least one metal on the side away from the substrate film sheet.
The magnetic sensor according to claim 1, wherein the magnetic sensor further comprises a first insulating layer, the first insulating layer is provided on a side of the magnetoresistive module away from the substrate, and covers the The metal film sheet.
The magnetic sensor of claim 1, wherein the magnetoresistive module comprises two first and two second magnetoresistive module groups, two first and two second magnetoresistive module groups The magnetoresistive module group forms a first Wheatstone bridge, the two first magnetoresistive module groups are respectively located at the first opposite bridge arms of the first Wheatstone bridge, and the two second magnetoresistive module groups are respectively a second opposite bridge arm of the first Wheatstone bridge;

The magnetization direction of the reference layer of the first magnetoresistive module group is the same as the positive direction of the first sensing axis of the magnetic sensor;

The second magnetoresistive module group includes two second magnetoresistive modules connected in series; the magnetization directions of the reference layers of the two second magnetoresistive modules form a first included angle, and the angle bisector of the first included angle is the same as the the first sensing axis is parallel; the first included angle is greater than 0° and less than 180°;

Wherein, the respective reference layer magnetization directions of the first magnetoresistive module group and the second magnetoresistive module are perpendicular to their respective easy magnetization axes.
The magnetic sensor according to claim 3, wherein each of the first magnetoresistive module groups is formed of M first magnetoresistive units in series; each of the second magnetoresistive modules is formed of N second magnetoresistive units The units are connected in series; M=2N; the first magnetoresistive unit and the second magnetoresistive unit have the same shape, and both are long-strip magnetoresistive film stacks; The magnetization axes are parallel to each other; the easy magnetization axes of the N second magnetoresistive units are parallel to each other;

Each of the first magnetoresistive units is provided with a plurality of the metal thin film sheets spaced apart along the length direction on one side away from the substrate;

And/or, the side of each of the second magnetoresistive units facing away from the substrate is provided with a plurality of the metal thin film sheets spaced along the length direction.
The magnetic sensor of claim 1, wherein the magnetoresistive module further comprises two third magnetoresistive module groups and two fourth magnetoresistive module groups, two third magnetoresistive module groups and two third magnetoresistive module groups Four magnetoresistive module groups form a second Wheatstone bridge, two of the third magnetoresistive module groups are respectively located on the first opposite bridge arms of the second Wheatstone bridge, and two of the fourth magnetoresistive module groups are respectively located at the second opposite bridge arms of the second Wheatstone bridge;

The magnetization directions of the reference layers of the adjacent third magnetoresistive module group and the fourth magnetoresistive module group form a second included angle, and the angle bisector of the second included angle is the first transmission line of the magnetic sensor. The sense axis is parallel; the second included angle is greater than 0° and less than 180°;

Wherein, the respective reference layer magnetization directions of the third magnetoresistive module group and the fourth magnetoresistive module group are perpendicular to their respective easy magnetization axes.
The magnetic sensor according to claim 5, wherein each of the third magnetoresistive module groups is formed by connecting P third magnetoresistive units in series; and each of the fourth magnetoresistive module groups is formed by P fourth magnetoresistive units. The third magnetoresistive unit and the fourth magnetoresistive unit have the same shape and are both long-strip magnetoresistive film stacks; the easy magnetization axes of the P third magnetoresistive units are mutually parallel; the easy magnetization axes of the P fourth magnetoresistive units are parallel to each other;

Each of the third magnetoresistive units is provided with a plurality of the metal thin film sheets spaced apart along the length direction on one side away from the substrate;

And/or, each of the fourth magnetoresistive units is provided with a plurality of the metal thin film sheets spaced apart along the length direction on one side away from the substrate.
An electronic device, wherein the electronic device includes a magnetic sensor as claimed in any one of claims 1 to 6.
A preparation method of a magnetic sensor, wherein the preparation method comprises the following steps:

providing a substrate;

sequentially depositing several layers of thin films on the substrate to obtain a magnetoresistive film stack;

image-etching the magnetoresistive film stack to form a plurality of magnetoresistive modules;

preparing wires on the substrate, and connecting the magnetoresistive modules through the wires to form a Wheatstone bridge;

A metal thin film sheet is prepared on the side of the magnetoresistive module away from the substrate to form a semi-finished product of the magnetic sensor;

The semi-finished product of the magnetic sensor is placed in an external magnetic field and annealed in the external magnetic field.
The method for manufacturing a magnetic sensor according to claim 8, wherein the step of preparing a metal thin film sheet on the side of the magnetoresistive module away from the substrate to form a semi-finished product of the magnetic sensor further comprises:

A first insulating layer is prepared on the side of the magnetoresistive module away from the substrate, and the first insulating layer covers the metal thin film.
The method for manufacturing a magnetic sensor according to claim 8, wherein the magnetic field direction of the external magnetic field is the same as the positive direction of the first sensing axis of the magnetic sensor.