Magnetic field sensor, manufacturing process and magnetic field detection method thereof

Abstract

The present application discloses a magnetic field sensor, a manufacturing process and a magnetic field detection method thereof, wherein the magnetic field detection method comprises the following steps: manufacturing a sample magnetic field sensor, wherein the magnetic induction device in the sample magnetic field sensor is a Hall bar structure; calibrating the standard variation curve of the Hall resistance and each component magnetic field strength of the sample magnetic field sensor; integrating a magnetic unit with the sample magnetic field sensor to obtain a standard magnetic field sensor; detecting the measured Hall resistance of the standard magnetic field sensor, querying the standard variation curve based on the measured Hall resistance, and determining the measured component magnetic field strength of the magnetic unit. The present application solves the technical problem that the prior art has poor effect in high-precision three-dimensional magnetic field detection of micro magnetic units, and greatly improves the accuracy and precision of three-dimensional magnetic field detection of micro magnetic units in chips.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic sensors, and in particular to a magnetic field sensor, a manufacturing process and a magnetic field detection method thereof. Background Art

[0002] High-precision magnetic field detection technology plays an important role in many application fields, such as navigation systems, automation equipment, biomedicine, etc. The types of magnetic field sensors developed from this are becoming more and more abundant, and the accuracy is getting higher and higher, such as superconducting quantum interferometers, Hall sensors, magnetoresistive sensors (such as AMR (Anisotropic Magneto resistance, anisotropic magnetoresistance) elements, GMR (Giant Magneto resistance) elements and TMR (Tunnel MagnetoResistance) elements, etc.), which greatly meet the magnetic field detection needs in different working environments. Even though there are many types of magnetic field sensors at present, they are relatively limited to the detection of a larger magnetic field space range. With the continuous development of spin electronics, spin electronic devices have also emerged, such as MRAM (Magnetic Random Access Array). Memory, magnetic random access memory), spin chips, etc., and in the post-Moore era today, for some spin electronic devices integrated inside the chip with a small magnetic field space range (such as spin chips), the means of detection using traditional external magnetic field sensors has problems such as inaccurate detection points and low detection accuracy. In particular, for thousands of small-sized hard magnetic structures (such as permanent magnets) with magnetic field distribution produced by micro-nano processes at the wafer level, the error of high-precision three-dimensional magnetic field detection of a single magnetic unit is large. Summary of the invention

[0003] The main purpose of the present application is to provide a magnetic field sensor, a manufacturing process and a magnetic field detection method thereof, aiming to solve the technical problem that the prior art has poor effect of high-precision three-dimensional magnetic field detection of a single magnetic unit.

[0004] To achieve the above object, the present application provides a magnetic field detection method, which comprises the following steps:

[0005] Making a sample magnetic field sensor, wherein the magnetic induction device in the sample magnetic field sensor is a Hall bar structure;

[0006] Applying a scanning magnetic field in a preset direction to the sample magnetic field sensor, and calibrating the standard variation curves of the Hall resistance of the magnetic induction device and the magnetic field intensity of each component;

[0007] Integrating the magnetic unit with the magnetic induction device to obtain a magnetic field sensor;

[0008] The measured Hall resistance of the magnetic field sensor is detected, and the corresponding standard change curve is queried according to the measured Hall resistance to determine the magnetic field strength of each measured component of the magnetic unit.

[0009] Preferably, the component magnetic field strength includes Hx in the x direction, Hy in the y direction, and Hz in the z direction, the Hall resistance includes Rxy in the y direction and Ryx in the x direction, the standard change curve includes an Rxy-Hx curve and a Ryx-Hy curve, and an Rxy-Hz curve and / or a Ryx-Hz curve, wherein the x direction and the y direction are coplanar with the magnetic induction device, and the x direction, the y direction, and the z direction are perpendicular to each other, and the steps of applying scanning magnetic fields in different directions to the sample magnetic field sensor and respectively calibrating the standard change curves of the Hall resistance and each component magnetic field strength of the sample magnetic field sensor include:

[0010] A scanning magnetic field in a preset direction is applied to the sample magnetic field sensor to calibrate the Rxy-Hx curve and the Ryx-Hy curve of the magnetic induction device, and the Rxy-Hz curve and / or the Ryx-Hz curve.

[0011] Preferably, the preset direction includes an x ​​direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Rxy-Hx curve of the magnetic induction device includes:

[0012] A preset current is passed through the magnetic induction device along the x direction, and a first scanning magnetic field is applied along the x direction, and a first Rxy corresponding to each Hx of the first scanning magnetic field is detected to obtain an Rxy-Hx curve.

[0013] Preferably, the preset direction includes a y direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Ryx-Hy curve of the magnetic induction device includes:

[0014] A preset current is passed through the magnetic induction device along the y direction, and a second scanning magnetic field is applied along the y direction, and a first Ryx corresponding to each Hy of the second scanning magnetic field is detected to obtain a Ryx-Hy curve.

[0015] Preferably, the preset direction includes a z direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Rxy-Hz curve of the magnetic induction device includes:

[0016] A preset current is passed through the magnetic induction device along the x direction, and a third scanning magnetic field is applied along the z direction, and a second Rxy corresponding to each Hz of the third scanning magnetic field is detected to obtain an Rxy-Hz curve.

[0017] Preferably, the preset direction includes a z direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Ryx-Hz curve of the magnetic induction device includes:

[0018] A preset current is passed through the magnetic induction device along the y direction, and a fourth scanning magnetic field is applied along the z direction, and a second Ryx corresponding to each Hz of the fourth scanning magnetic field is detected to obtain a Ryx-Hz curve.

[0019] Preferably, the step of detecting the measured Hall resistance of the standard magnetic field sensor, querying the standard variation curve according to the measured Hall resistance, and determining the magnetic field strength of each measured component of the magnetic unit comprises:

[0020] Passing the preset current along the positive x direction to measure Rxy1 generated by the preset current, passing the preset current along the negative x direction to measure Rxy2 generated by the preset current, and determining Rxy(Hx) generated by the x-direction component magnetic field on the magnetic induction device and / or Rxy(Hz) generated by the z-direction component magnetic field on the magnetic induction device according to Rxy1 and Rxy2;

[0021] Passing the preset current along the positive direction of the y direction to measure Ryx3 generated by the preset current, passing the preset current along the negative direction of the y direction to measure Ryx4 generated by the preset current, and determining Ryx (Hy) generated by the y-direction component magnetic field on the magnetic induction device and / or Ryx (Hz) generated by the z-direction component magnetic field on the magnetic induction device according to Ryx3 and Ryx4;

[0022] According to the Rxy(Hx) and Ryx(Hy), and Rxy(Hz) and / or Ryx(Hz), the corresponding Rxy-Hx curve, the Ryx-Hy curve, the Rxy-Hz curve or the Ryx-Hz curve are queried respectively to obtain the measured magnetic field strength of the x-direction component, the measured magnetic field strength of the y-direction component and the measured magnetic field strength of the z-direction component of the magnetic unit.

[0023] The present application also provides a magnetic field sensor, which includes: a base layer, a magnetic unit and a magnetic induction device; wherein the magnetic unit is deposited on the surface of the base layer, the magnetic induction device is a Hall bar structure, and the magnetic induction device is deposited on the surface of the base layer.

[0024] The present application also provides a magnetic field sensor manufacturing process, the magnetic field sensor manufacturing process comprising the following steps:

[0025] depositing a first passivation layer on the base layer;

[0026] Depositing a magnetic thin film layer on the first passivation layer, and patterning the magnetic thin film layer to obtain a magnetic unit;

[0027] depositing a second passivation layer on the magnetic unit;

[0028] Depositing a magnetic induction film layer on the second passivation layer, and patterning the magnetic induction film layer to obtain a magnetic induction device with a Hall bar structure;

[0029] The first passivation layer and the second passivation layer are patterned to obtain a magnetic field sensor.

[0030] Preferably, the magnetic induction thin film layer is a multilayer heterostructure of Ta / CoFeB / MgO / Ta.

[0031] The present application provides a magnetic field sensor, a manufacturing process and a magnetic field detection method thereof. A sample magnetic field sensor is manufactured, wherein the magnetic induction device in the sample magnetic field sensor is a Hall bar structure, a scanning magnetic field in a preset direction is applied to the sample magnetic field sensor, and the standard change curves of the Hall resistance and the magnetic field strength of each component of the magnetic induction device are calibrated respectively, so that a standard change curve of the magnetic field strength in a preset direction with the change of the Hall resistance is established according to the scanning magnetic field in different preset directions applied autonomously. A magnetic field sensor is obtained by integrating a magnetic unit with the magnetic induction device, and the measured Hall resistance of the magnetic field sensor is detected. The standard change curve is queried according to the measured Hall resistance to determine the magnetic field strength of each measured component of the magnetic unit, so that high-precision three-dimensional magnetic field detection of a single magnetic unit is achieved through the magnetic induction device integrated with the magnetic unit in a chip, that is, by adopting a magnetic induction device integrating three-axis magnetic field detection based on the spin-orbit moment effect as a magnetic field induction unit, high-precision three-dimensional magnetic field detection of a single magnetic unit in the chip is simply and accurately performed through an electrical test method, so that the technical problem of poor effect of high-precision three-dimensional magnetic field detection of a single magnetic unit in the prior art is overcome, and the accuracy and precision of three-dimensional magnetic field detection of a single magnetic unit in the chip is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0034] Figure 1 A schematic diagram of a flow chart of an embodiment of a magnetic field detection method of the present application;

[0035] Figure 2 FIG. 1 is a flow chart of an embodiment of a manufacturing process of a magnetic field sensor of the present application.

[0036] The purpose, features and advantages of this application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0038] High-precision magnetic field detection technology plays an important role in many application fields, such as navigation systems, automation equipment, biomedicine, etc. The types of magnetic field sensors developed from this are becoming more and more abundant, and the accuracy is getting higher and higher, such as superconducting quantum interferometers, Hall sensors, magnetoresistive sensors (such as AMR (Anisotropic Magneto resistance, anisotropic magnetoresistance) elements, GMR (Giant Magneto resistance) elements and TMR (Tunnel MagnetoResistance) elements, etc.), which greatly meet the magnetic field detection needs in different working environments. Even though there are many types of magnetic field sensors at present, they are relatively limited to the detection of a larger magnetic field space range. With the continuous development of spin electronics, spin electronic devices have also emerged, such as MRAM (Magnetic Random Access Array). Memory, magnetic random access memory), spin chips, etc., and in the post-Moore era today, for some spin electronic devices integrated inside the chip with a small magnetic field space range (such as spin chips), the means of detection using traditional external magnetic field sensors have problems such as inaccurate detection points and low detection accuracy. At present, although integrated magnetic field detection in the chip has been realized, which greatly improves the detection accuracy, if only GMR bar (giant magnetoresistance bar) is used as a magnetic field sensing unit to detect the magnetic field without using a flux concentrator, it can only detect the magnetic field intensity in the xy plane, and cannot realize the x, y, and z direction component magnetic field detection in three-dimensional space. If a flux concentrator (such as nickel-iron alloy material) is used to introduce the x, y, and z direction component magnetic fields into the x and y directions, thereby realizing the uniaxial detection of the three-dimensional magnetic field, three flux concentrator units with different orientations are required. Since one flux concentrator and one GMR The bar forms a single-axis magnetic field detector. To detect the x, y, and z three-axis magnetic fields, three such single-axis magnetic field detectors are needed to be distributed near the target detection point. Therefore, there is not only the problem of inconsistent distribution points leading to large magnetic field errors, but also complex process manufacturing and large size of the magnetic field sensing unit.

[0039] The present application embodiment provides a magnetic field detection method. In one embodiment of the magnetic field detection method of the present application, refer to Figure 1 , the magnetic field detection method comprises:

[0040] Step S10, manufacturing a sample magnetic field sensor, wherein the magnetic induction device in the sample magnetic field sensor is a Hall bar structure;

[0041] In this embodiment, it should be noted that the magnetic field sensor is a device that can convert various magnetic fields and their changes into electrical signals for output. The standard magnetic field sensor includes at least a substrate layer, a magnetic unit and a magnetic induction device. The sample magnetic field sensor includes at least a substrate layer and a magnetic induction device without a magnetic unit. The sample magnetic field sensor is used to determine the standard Hall resistance generated by the magnetic induction device under the action of a scanning magnetic field of a known magnetic field strength when there is no magnetic field to be measured generated by the magnetic unit, and then determine the change curve of the Hall resistance of the magnetic induction device with the change of each component magnetic field strength. The substrate layer can be a SOI silicon wafer or a POI silicon wafer, etc. The magnetic unit is deposited on the surface of the substrate layer, and the magnetic unit includes a permanent magnet, etc. The magnetic induction device is a multilayer heterostructure based on the spin-orbit moment effect. In an operative manner, the multilayer heterostructure is Ta / CoFeB / MgO / Ta, and the magnetic induction device is a Hall bar structure, which is composed of at least two mutually perpendicular Hall bars. The magnetic induction device is used to detect the three-dimensional magnetic field in the chip, and the magnetic induction device is deposited on the surface of the substrate layer.

[0042] Specifically, a magnetic induction thin film layer is deposited on a base layer, and the magnetic induction thin film layer is patterned to obtain a magnetic induction device with a Hall bar structure, wherein the base layer may be an SOI silicon wafer or a POI silicon wafer, etc., the method for depositing the magnetic induction thin film layer includes magnetron sputtering or evaporative deposition, etc., the method for patterning the magnetic induction thin film layer includes processes such as photolithography and etching, and specifically, the patterning process may also include spin coating, soft baking, exposure, post-baking, development, hard baking, etching and / or detection.

[0043] In an practicable manner, the step of manufacturing a sample magnetic field sensor includes:

[0044] depositing a passivation layer on the base layer;

[0045] Depositing a magnetic induction film layer on the passivation layer, and patterning the magnetic induction film layer to obtain a magnetic induction device with a Hall bar structure;

[0046] The passivation layer is patterned to obtain a sample magnetic field sensor.

[0047] In this embodiment, specifically, a passivation layer is deposited on a POI silicon wafer or a SOI silicon wafer by a PECVD (Plasma Enhanced Chemical Vapor Deposition) device or an ICPCVD (Inductively Coupled Plasma Chemical Vapor Deposition) device, and a magnetic induction film is deposited on a substrate deposited with the passivation layer by magnetron sputtering or evaporation deposition, and the magnetic induction film is patterned to obtain a magnetic induction device with a Hall bar structure, wherein the passivation layer includes silicon nitride and / or silicon oxide, and the patterning process includes spin coating, soft baking, exposure, post-baking, development, hard baking, etching and / or detection, and the etching includes IBE (Ion Beam Etching) or ICP (Inductively Coupled Plasma) etching.

[0048] Step S20, applying a scanning magnetic field in a preset direction to the sample magnetic field sensor, and calibrating the standard variation curves of the Hall resistance of the magnetic induction device and the magnetic field intensity of each component;

[0049] In the present embodiment, it should be noted that when and only when the direction of the input current is collinear with the direction of the in-plane magnetic field, the spin-orbit moment equivalent field perpendicular to the surface of the magnetic induction device is generated due to the spin-orbit moment effect, thereby driving the magnetic domain wall to move, the magnetic moment flips, and then directly contributes to the Hall resistance; when the direction of the input current is orthogonal to the direction of the in-plane magnetic field, the magnetic domain wall will not be displaced, that is, it will not contribute to the Hall resistance; when the current is input, there is no in-plane magnetic field, but there is an out-of-plane magnetic field perpendicular to the plane, the magnetic domain wall will also be displaced, thereby contributing to the Hall resistance, wherein the Hall resistance is the ratio of the Hall voltage to the input current, so the corresponding Hall resistance can be calculated by detecting the Hall voltage, and then in the sample magnetic field sensor without a magnetic unit, by applying a scanning magnetic field in a preset direction and detecting the Hall resistance corresponding to the scanning magnetic field of different magnetic field strengths, the standard change curve of the Hall resistance and each component magnetic field strength of the magnetic induction device can be obtained.

[0050] Among them, the scanning magnetic field is a series of magnetic fields with different magnetic field strengths, the standard change curve is a curve in which the Hall resistance generated by the magnetic induction device under the action of magnetic fields of different magnetic field strengths changes with the change of the magnetic field strength, and the component magnetic field strength is the magnetic field strength generated by a magnetic field in any direction in a preset direction. It is easy to understand that if the direction of the target magnetic field is the same as the direction of the component magnetic field, then the component magnetic field strength is equal to the magnetic field strength of the target magnetic field.

[0051] Specifically, a scanning magnetic field in a preset direction is applied to the sample magnetic field sensor. When a magnetic field of a preset magnetic field strength is applied in each preset direction, a current is passed in the preset current direction of the magnetic induction device, and then the voltage generated by the magnetic induction device is detected. The corresponding Hall resistance is calculated according to the current and the voltage, and the Hall resistance and the corresponding preset magnetic field strength are recorded. The Hall resistance generated by the magnetic field of different magnetic field strengths in the same preset direction and the magnetic field strengths of different sizes corresponding to each Hall resistance are statistically analyzed and curve-fitted, so as to obtain a standard change curve of the Hall resistance of the magnetic induction device with the component magnetic field strength of the preset direction, wherein the preset direction includes the magnetic induction device. For convenience of explanation, in the subsequent description, the two directions perpendicular to each other in the plane where the magnetic induction device is located are represented by the x direction and the y direction, and the direction perpendicular to the plane where the magnetic induction device is located is represented by the z direction. For example, a current Ix is passed along the x direction, and a scanning magnetic field is applied along the x direction in the plane. The voltage Vy in the y direction generated by the magnetic field of each magnetic field strength on the magnetic induction device is recorded, and the Hall resistance Rxy in the y direction is calculated according to the Ix and Vy. The Hx is used as the abscissa and Rxy is used as the ordinate, so as to obtain a standard change curve of Rxy with the change of Hx.

[0052] Preferably, the component magnetic field strength includes Hx in the x direction, Hy in the y direction, and Hz in the z direction, the Hall resistance includes Rxy in the y direction and Ryx in the x direction, the standard change curve includes an Rxy-Hx curve and a Ryx-Hy curve, and an Rxy-Hz curve and / or a Ryx-Hz curve, wherein the x direction and the y direction are coplanar with the magnetic induction device, and the x direction, the y direction, and the z direction are perpendicular to each other, and the steps of applying scanning magnetic fields in different directions to the sample magnetic field sensor and respectively calibrating the standard change curves of the Hall resistance and each component magnetic field strength of the sample magnetic field sensor include:

[0053] A scanning magnetic field in a preset direction is applied to the sample magnetic field sensor to calibrate the Rxy-Hx curve and the Ryx-Hy curve of the magnetic induction device, and the Rxy-Hz curve and / or the Ryx-Hz curve.

[0054] In this embodiment, specifically, a scanning magnetic field in the x direction is applied to the sample magnetic field sensor to calibrate the Rxy-Hx curve of the magnetic induction device, a scanning magnetic field in the y direction is applied to the sample magnetic field sensor to calibrate the Ryx-Hy curve of the magnetic induction device, and a scanning magnetic field in the z direction is applied to the sample magnetic field sensor to calibrate the Rxy-Hz curve and / or the Ryx-Hz curve of the magnetic induction device.

[0055] It is easy to understand that if the component magnetic field strength in any one or more directions of the x-direction, y-direction or z-direction is to be detected with high precision for the magnetic unit, the standard change curve of the component magnetic field strength in the corresponding direction and the Hall resistance of the magnetic induction device must be calibrated. If the three-dimensional detection of the magnetic unit is to be achieved, the standard change curve of the Hall resistance of at least one of the magnetic induction devices and the component magnetic field strength in the x-direction, the standard change curve of the Hall resistance of at least one of the magnetic induction devices and the component magnetic field strength in the y-direction and the Hall resistance of at least one of the magnetic induction devices must be obtained. A standard variation curve of the magnetic resistance and the component magnetic field strength in the z direction is provided. For example, if the component magnetic field strength in the y direction of the magnetic unit is to be detected, the Ryx-Hy curve needs to be calibrated. If the magnetic field strength in a plane of the magnetic unit is to be detected, the Ryx-Hy curve and the Rxy-Hx curve need to be calibrated. If the three-dimensional magnetic field strength of the magnetic unit is to be detected, the Ryx-Hy curve and the Rxy-Hx curve, as well as the Rxy-Hz curve and / or the Ryx-Hz curve need to be calibrated.

[0056] Preferably, the preset direction includes an x ​​direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Rxy-Hx curve of the magnetic induction device includes:

[0057] A preset current is passed through the magnetic induction device along the x direction, and a first scanning magnetic field is applied along the x direction, and a first Rxy corresponding to each Hx of the first scanning magnetic field is detected to obtain an Rxy-Hx curve.

[0058] In this embodiment, specifically, a preset current is passed through the magnetic induction device along the x direction, and a first scanning magnetic field is applied along the x direction, and a voltage Vy generated by the magnetic induction device in the y direction under the action of each magnetic field Hx of the first scanning magnetic field is detected. The first Rxy generated by the magnetic induction device under the action of each magnetic field Hx of the first scanning magnetic field can be calculated based on the preset current and the detected Vy. The first Rxy and the Hx are used as the horizontal and vertical coordinates, respectively, and an Rxy-Hx curve of the magnetic induction device changing with the component magnetic field intensity Hx in the x direction is obtained by a curve fitting method.

[0059] Preferably, the preset direction includes a y direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Ryx-Hy curve of the magnetic induction device includes:

[0060] A preset current is passed through the magnetic induction device along the y direction, and a second scanning magnetic field is applied along the y direction, and a first Ryx corresponding to each Hy of the second scanning magnetic field is detected to obtain a Ryx-Hy curve.

[0061] In this embodiment, specifically, a preset current is passed through the magnetic induction device along the y direction, and a second scanning magnetic field is applied along the y direction, and a voltage Vx generated by the magnetic induction device in the x direction under the action of each magnetic field Hy of the first scanning magnetic field is detected. The first Ryx generated by the magnetic induction device under the action of each magnetic field Hy of the second scanning magnetic field can be calculated based on the preset current and the detected Vx. The first Ryx and the Hy are used as the horizontal and vertical coordinates, respectively, and a Ryx-Hy curve of the magnetic induction device showing a change in Ryx with the component magnetic field intensity Hy in the y direction is obtained by a curve fitting method.

[0062] Preferably, the preset direction includes a z direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Rxy-Hz curve of the magnetic induction device includes:

[0063] A preset current is passed through the magnetic induction device along the x direction, and a third scanning magnetic field is applied along the z direction, and a second Rxy corresponding to each Hz of the third scanning magnetic field is detected to obtain an Rxy-Hz curve.

[0064] In this embodiment, specifically, a preset current is passed through the magnetic induction device along the x direction, and a third scanning magnetic field is applied along the z direction, and a voltage Vy generated by the magnetic induction device in the y direction under the action of a magnetic field of each Hz of the first scanning magnetic field is detected. The second Rxy generated by the magnetic induction device under the action of a magnetic field of each Hz of the third scanning magnetic field can be calculated based on the preset current and the detected Vy. The second Rxy and the Hz are used as horizontal and vertical coordinates, respectively, and an Rxy-Hz curve of the magnetic induction device changing with the component magnetic field intensity Hz in the z direction is obtained by a curve fitting method.

[0065] The preset direction includes a z direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor and calibrating the Ryx-Hz curve of the magnetic induction device includes:

[0066] A preset current is passed through the magnetic induction device along the y direction, and a fourth scanning magnetic field is applied along the z direction, and a second Ryx corresponding to each Hz of the fourth scanning magnetic field is detected to obtain a Ryx-Hz curve.

[0067] In this embodiment, specifically, a preset current is passed through the magnetic induction device along the y direction, and a fourth scanning magnetic field is applied along the z direction, and a voltage Vx generated by the magnetic induction device in the x direction under the action of a magnetic field of each Hz of the first scanning magnetic field is detected. The second Ryx generated by the magnetic induction device under the action of a magnetic field of each Hz of the fourth scanning magnetic field can be calculated based on the preset current and the detected Vx. The second Ryx and the Hz are used as horizontal and vertical coordinates, respectively, and a Ryx-Hz curve of the magnetic induction device changing with the component magnetic field intensity Hz in the z direction is obtained by a curve fitting method.

[0068] Step S30, integrating the magnetic unit with the sample magnetic field sensor to obtain a standard magnetic field sensor;

[0069] In this embodiment, specifically, a magnetic film layer is deposited on a substrate layer, the magnetic film layer is patterned to obtain a magnetic unit, a magnetic induction film layer is deposited on the substrate layer at a preset distance from the magnetic unit, the magnetic induction film layer is patterned to obtain a magnetic induction device with a Hall bar structure, wherein the substrate layer may be an SOI silicon wafer or a POI silicon wafer, etc., the magnetic film layer includes a rare earth permanent magnetic material or a ferrite permanent magnetic material, etc., the method for depositing the magnetic film layer includes magnetron sputtering or evaporation deposition, etc., the method for patterning the magnetic film layer includes processes such as photolithography and etching, the magnetic induction film layer is a multilayer heterostructure based on the spin-orbit moment effect, and in an practicable manner, the multilayer heterostructure is Ta / CoFeB / MgO / Ta, the method for depositing the magnetic induction film layer includes magnetron sputtering or evaporation deposition, the method for patterning the magnetic induction film layer includes processes such as photolithography and etching, the magnetic induction device is a Hall bar structure, and the Hall bar structure is composed of at least two mutually perpendicular Hall bars. The distance between the magnetic unit and the magnetic induction device can be adjusted according to the magnetic field size and chip size in actual application. This embodiment is not limited to this. In an practicable manner, in the process of depositing and patterning the magnetic film and the magnetic induction film, the base layer, the magnetic unit and the magnetic induction device can also be isolated and protected by depositing a passivation layer.

[0070] In an practicable manner, the step of integrating the magnetic unit with the sample magnetic field sensor to obtain a standard magnetic field sensor includes:

[0071] depositing a first passivation layer on the base layer;

[0072] Depositing a magnetic thin film layer on the first passivation layer, and patterning the magnetic thin film layer to obtain a magnetic unit;

[0073] depositing a second passivation layer on the magnetic unit;

[0074] Depositing a magnetic induction film layer on the second passivation layer, and patterning the magnetic induction film layer to obtain a magnetic induction device with a Hall bar structure;

[0075] The first passivation layer and the second passivation layer are patterned to obtain a standard magnetic field sensor.

[0076] In this embodiment, specifically, a first passivation layer is deposited on a POI silicon wafer or SOI silicon wafer by a PECVD (Plasma Enhanced Chemical Vapor Deposition) device or an ICPCVD (Inductively Coupled Plasma Chemical Vapor Deposition) device to ensure that the magnetic unit and the substrate layer do not diffuse with each other during the high-temperature rapid annealing process, and a magnetic film is deposited on the substrate with the passivation layer by magnetron sputtering, and then by RTP (rapid The invention relates to a method for preparing a magnetic sensor having a Hall bar structure by using a high-temperature rapid annealing process such as thermal processing (rapid thermal processing) to order the magnetic moment in the magnetic film, patterning the magnetic film layer to obtain a magnetic unit, depositing a second passivation layer on the magnetic unit to separate the magnetic unit from the subsequently deposited magnetic induction film layer to avoid the interface coupling effect affecting the performance of the magnetic unit, depositing a magnetic induction film on the base deposited with the second passivation layer by magnetron sputtering or evaporation deposition, and then obtaining a magnetic induction device with a Hall bar structure by a patterning process, patterning the first passivation layer and the second passivation layer to reduce the film stress and avoid the subsequent MEMS (Micro-Electro-Mechanical System) structure from warping due to excessive stress, and obtaining a standard magnetic field sensor capable of performing three-axis detection in the chip, wherein the passivation layer comprises silicon nitride and / or silicon oxide, and the patterning process comprises spin coating, soft baking, exposure, post-baking, development, hard baking, etching and / or detection, wherein the magnetic film comprises a permanent magnetic film, and the etching comprises IBE (Ion Beam Etching (ion beam etching) or ICP (Inductively Coupled Plasma) etching, etc., the magnetic induction film layer is a multilayer heterostructure based on the spin-orbit moment effect. In an practicable manner, the multilayer heterostructure is Ta / CoFeB / MgO / Ta.

[0077] Step S40, detecting the measured Hall resistance of the standard magnetic field sensor, querying the corresponding standard change curve according to the measured Hall resistance, and determining the magnetic field strength of each measured component of the magnetic unit.

[0078] In this embodiment, it should be noted that, for the convenience of explanation, the x direction and the y direction represent two mutually perpendicular directions in the plane where the magnetic induction device is located, and the z direction represents the direction perpendicular to the plane where the magnetic induction device is located. It is assumed that the induction device is under the action of a three-dimensional vector magnetic field H (the component magnetic field strengths in the x direction, the y direction, and the z direction are Hx, Hy, and Hz, respectively), and a current is passed along the x+ direction. Then, the Hall resistance Rxy measured along the y direction is jointly determined by Hx and Hz. If the current passing direction is changed to along the x- direction, the contribution of the current in the opposite direction to Rxy under the joint action of the same Hx is opposite, but the contribution to Rxy under the joint action of Hz remains unchanged, so If the two are added together, the contribution of Hx cancels out, leaving only the contribution of Hz, thereby detecting and separating the contribution of Hz to Rxy, i.e., Rxy(Hz)=(Rxy1+Rxy2) / 2. If the two are subtracted, the contribution of Hz cancels out, leaving only the contribution of Hx, thereby detecting and separating the contribution of Hx to Rxy, i.e., Rxy(Hx)=(Rxy1-Rxy2) / 2. Similarly, when current is passed along the y+ and y- directions, the contribution of Hz to the Hall resistance Ryx measured along the x direction and the contribution of Hy to Ryx can be detected and separated, i.e., Ryx(Hz)=(Ryx1+Ryx2) / 2, Ryx(Hy)=(Ryx1-Ryx2) / 2.

[0079] Specifically, under the action of the magnetic field generated by the magnetic unit, a first current is passed in the positive direction of a preset current, and a first voltage correspondingly generated by the magnetic induction device is detected, and a corresponding first Hall resistance is calculated according to the first current and the first voltage. A second current is passed in the negative direction of the preset current, and a second voltage correspondingly generated by the magnetic induction device is detected, and a corresponding second Hall resistance is calculated according to the second current and the second voltage. The measured Hall resistance in the target resistance direction is calculated according to the first Hall resistance and the second Hall resistance, and the corresponding standard change curve is queried according to the measured Hall resistance, so as to obtain the measured component magnetic field direction of the magnetic unit corresponding to the target resistance direction. Field strength, for example, a current +Ix is passed along the x+ direction of the magnetic field sensing unit, Vy1 is measured, Rxy1 is calculated based on the +Ix and the Vy1, and then a current -Ix is passed along the x- direction, Vy2 is measured, Rxy2 is calculated based on the -Ix and the Vy2, Rxy(Hx)=(Rxy1-Rxy2) / 2 is calculated, and a calibrated standard variation curve of Rxy with Hx is queried based on Rxy(Hx), and the Hx value is read, which is the magnetic field component of the x-direction component of the permanent magnet, and Rxy(Hz)=(Rxy1+Rxy2) / 2 is calculated, and a calibrated Rxy-Hz curve is queried based on Rxy(Hz), and the Hz value is read, which is the magnetic field component of the z-direction component of the permanent magnet.

[0080] Preferably, the step of detecting the measured Hall resistance of the standard magnetic field sensor, querying the standard variation curve according to the measured Hall resistance, and determining the magnetic field strength of each measured component of the magnetic unit comprises:

[0081] Step A10, passing the preset current along the positive direction of the x direction to measure Rxy1 generated by the preset current, passing the preset current along the negative direction of the x direction to measure Rxy2 generated by the preset current, and determining Rxy (Hx) generated by the x-direction component magnetic field on the magnetic induction device and / or Rxy (Hz) generated by the z-direction component magnetic field on the magnetic induction device according to Rxy1 and Rxy2;

[0082] In this embodiment, specifically, the preset current is passed along the positive direction of the x direction, and the voltage Vy1 generated by the preset current in the y direction is measured. The Hall resistance Rxy1 generated by the magnetic induction device under the magnetic field of the magnetic unit is calculated based on the preset current and the Vy1. The preset current is passed along the negative direction of the x direction, and the voltage Vy2 generated by the preset current in the y direction is measured. The Hall resistance Rxy2 generated by the magnetic induction device under the magnetic field of the magnetic unit is calculated based on the preset current and the Vy2. Further, Rxy(Hx)=(Rxy1-Rxy2) / 2 is calculated to obtain Rxy(Hx), and Rxy(Hz)=(Rxy1+Rxy2) / 2 is calculated to obtain Rxy(Hz).

[0083] Step A20, passing the preset current along the positive direction of the y direction to measure Ryx3 generated by the preset current, passing the preset current along the negative direction of the y direction to measure Ryx4 generated by the preset current, and determining Ryx (Hy) generated by the y-direction component magnetic field on the magnetic induction device and / or Ryx (Hz) generated by the z-direction component magnetic field on the magnetic induction device based on Ryx3 and Ryx4;

[0084] In this embodiment, specifically, the preset current is passed along the positive direction of the y direction, and the voltage Vx1 generated by the preset current in the x direction is measured. The Hall resistance Ryx1 generated by the magnetic induction device under the magnetic field of the magnetic unit is calculated based on the preset current and the Vx1. The preset current is passed along the negative direction of the y direction, and the voltage Vx2 generated by the preset current in the x direction is measured. The Hall resistance Ryx2 generated by the magnetic induction device under the magnetic field of the magnetic unit is calculated based on the preset current and the Vx2. Further, Ryx(Hz) can be calculated based on Ryx(Hz)=(Ryx1+Ryx2) / 2, and Ryx(Hy) can be calculated based on Ryx(Hy)=(Ryx1-Ryx2) / 2.

[0085] Step A30, query the corresponding Rxy-Hx curve, the Ryx-Hy curve, the Rxy-Hz curve or the Ryx-Hz curve according to the Rxy(Hx) and Ryx(Hy), as well as Rxy(Hz) and / or Ryx(Hz) to obtain the measured magnetic field strength of the x-direction component, the measured magnetic field strength of the y-direction component and the measured magnetic field strength of the z-direction component of the magnetic unit.

[0086] In this embodiment, specifically, the corresponding Rxy-Hx curve is queried according to the Rxy(Hx) to obtain the measured magnetic field strength of the x-direction component of the magnetic unit, the corresponding Ryx-Hy curve is queried according to the Ryx(Hy) to obtain the measured magnetic field strength of the y-direction component of the magnetic unit, the corresponding Rxy-Hz curve is queried according to the Rxy(Hz) to obtain the measured magnetic field strength of the z-direction component of the magnetic unit, and the corresponding Ryx-Hz curve is queried according to the Ryx(Hz) to obtain the measured magnetic field strength of the z-direction component of the magnetic unit. It is easy to understand that the measured magnetic field strength of the z-direction component can be obtained by detecting Rxy(Hz) and / or Ryx(Hz) and then querying the corresponding standard change curve, which can be selected according to actual needs and presets. This embodiment is not limited to this.

[0087] In this embodiment, a sample magnetic field sensor is manufactured, wherein the magnetic induction device in the sample magnetic field sensor is a Hall bar structure, a scanning magnetic field in a preset direction is applied to the sample magnetic field sensor, and the standard change curves of the Hall resistance of the magnetic induction device and the magnetic field strength of each component are calibrated respectively, so that a standard change curve of the magnetic field strength in a preset direction changing with the Hall resistance is established according to the autonomous application of scanning magnetic fields in different preset directions. A magnetic field sensor is obtained by integrating a magnetic unit with the magnetic induction device, and the measured Hall resistance of the magnetic field sensor is detected. The standard change curve is queried according to the measured Hall resistance to determine the magnetic field strength of each measured component of the magnetic unit, so that high-precision three-dimensional magnetic field detection of a single magnetic unit is achieved through the magnetic induction device integrated with the magnetic unit in the chip, that is, by adopting a magnetic induction device integrating three-axis magnetic field detection based on the spin-orbit moment effect as the magnetic field induction unit, high-precision three-dimensional magnetic field detection of a single magnetic unit in the chip is simply and accurately performed through an electrical test method, so that the technical problem of poor effect of high-precision three-dimensional magnetic field detection of a single magnetic unit in the prior art is overcome, and the accuracy and precision of three-dimensional magnetic field detection of a single magnetic unit in the chip is greatly improved.

[0088] Furthermore, the present invention also provides a magnetic field sensor, which includes: a base layer, a magnetic unit and a magnetic induction device; wherein the magnetic unit is deposited on the surface of the base layer, the magnetic induction device is a Hall bar structure, and the magnetic induction device is deposited on the surface of the base layer.

[0089] In this embodiment, it should be noted that the base layer can be a SOI silicon wafer or a POI silicon wafer, etc., the magnetic unit is deposited on the surface of the base layer, the magnetic unit includes a permanent magnet, etc., the magnetic induction device is a multilayer heterostructure based on the spin-orbit moment effect, and in an implementable manner, the multilayer heterostructure is Ta / CoFeB / MgO / Ta, the magnetic induction device is a Hall bar structure, and the Hall bar structure is composed of at least two mutually perpendicular Hall bars. The magnetic induction device is used to detect the three-dimensional magnetic field in the chip, and the magnetic induction device is deposited on the surface of the base layer.

[0090] Specifically, the magnetic field sensor manufacturing process includes the following steps:

[0091] depositing a first passivation layer on the base layer;

[0092] Depositing a magnetic thin film layer on the first passivation layer, and patterning the magnetic thin film layer to obtain a magnetic unit;

[0093] depositing a second passivation layer on the magnetic unit;

[0094] Depositing a magnetic induction film layer on the second passivation layer, and patterning the magnetic induction film layer to obtain a magnetic induction device with a Hall bar structure;

[0095] The first passivation layer and the second passivation layer are patterned to obtain a magnetic field sensor.

[0096] Preferably, the magnetic induction thin film layer is a multilayer heterostructure of Ta / CoFeB / MgO / Ta.

[0097] In this embodiment, by integrating the magnetic induction device with the spin-orbit moment effect with the magnetic unit, the technical problem of poor high-precision three-dimensional magnetic field detection effect of the micro-magnetic unit in the prior art is solved. Compared with the prior art, the beneficial effects of the magnetic field sensor provided in the embodiment of the present invention are the same as the beneficial effects of the magnetic field detection method in the above embodiment, which will not be described in detail here.

[0098] Further, refer to Figure 2 The present invention also provides a magnetic field sensor manufacturing process, the magnetic field sensor manufacturing process comprising the following steps:

[0099] Step B10, depositing a first passivation layer on the base layer;

[0100] Step B20, depositing a magnetic thin film layer on the first passivation layer, and patterning the magnetic thin film layer to obtain a magnetic unit;

[0101] Step B30, depositing a second passivation layer on the magnetic unit;

[0102] Step B40, depositing a magnetic induction thin film layer on the second passivation layer, and patterning the magnetic induction thin film layer to obtain a magnetic induction device with a Hall bar structure;

[0103] Step B50: patterning the first passivation layer and the second passivation layer to obtain a magnetic field sensor.

[0104] In this embodiment, specifically, a first passivation layer is deposited on a POI silicon wafer or SOI silicon wafer by a PECVD (Plasma Enhanced Chemical Vapor Deposition) device or an ICPCVD (Inductively Coupled Plasma Chemical Vapor Deposition) device to ensure that the magnetic unit and the substrate layer do not diffuse with each other during the high-temperature rapid annealing process, and a magnetic film is deposited on the substrate with the passivation layer by magnetron sputtering, and then by RTP (rapid The invention relates to a method for preparing a magnetic sensor having a Hall bar structure by using a high-temperature rapid annealing process such as thermal processing (rapid thermal processing) to order the magnetic moment in the magnetic film, patterning the magnetic film layer to obtain a magnetic unit, depositing a second passivation layer on the magnetic unit to separate the magnetic unit from the subsequently deposited magnetic induction film layer to avoid the interface coupling effect affecting the performance of the magnetic unit, depositing a magnetic induction film on the base deposited with the second passivation layer by magnetron sputtering or evaporation deposition, and then obtaining a magnetic induction device with a Hall bar structure by a patterning process, patterning the first passivation layer and the second passivation layer to reduce the film stress and avoid the subsequent MEMS (Micro-Electro-Mechanical System) structure from warping due to excessive stress, and obtaining a standard magnetic field sensor capable of performing three-axis detection in the chip, wherein the passivation layer comprises silicon nitride and / or silicon oxide, and the patterning process comprises spin coating, soft baking, exposure, post-baking, development, hard baking, etching and / or detection, wherein the magnetic film comprises a permanent magnetic film, and the etching comprises IBE (Ion Beam Etching, ion beam etching) or ICP (Inductively Coupled Plasma) etching, etc., the magnetic induction film layer is a multilayer heterostructure based on the spin-orbit moment effect, and preferably, the magnetic induction film layer is Ta / CoFeB / MgO / Ta.

[0105] In this embodiment, by integrating the magnetic induction device with the spin-orbit moment effect with the magnetic unit, the technical problem of the prior art that the micro-magnetic unit has poor high-precision three-dimensional magnetic field detection effect is solved. Compared with the prior art, the beneficial effects of the magnetic field sensor provided in the embodiment of the present invention are the same as the beneficial effects of the magnetic field detection method in the above embodiment, which will not be described in detail here.

[0106] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent processing scope of the present application.

Claims

1. A magnetic field detection method, characterized in that: The magnetic field detection method comprises the following steps: Making a sample magnetic field sensor, wherein the magnetic induction device in the sample magnetic field sensor is a Hall bar structure; Applying a scanning magnetic field in a preset direction to the sample magnetic field sensor, and calibrating the standard variation curves of the Hall resistance of the magnetic induction device and the magnetic field intensity of each component; A standard magnetic field sensor is obtained by integrating a magnetic unit with the magnetic induction device, wherein the magnetic unit and the magnetic induction device are integrated in a chip, and the magnetic induction device is located at a preset distance from the magnetic unit, and the preset distance is adjusted according to the magnitude of the magnetic field and the size of the chip; The measured Hall resistance of the standard magnetic field sensor is detected, and the corresponding standard change curve is queried according to the measured Hall resistance to determine the magnetic field strength of each measured component of the magnetic unit.

2. The magnetic field detection method according to claim 1, characterized in that: The component magnetic field strength includes Hx in the x direction, Hy in the y direction, and Hz in the z direction, the Hall resistance includes Rxy in the y direction and Ryx in the x direction, the standard change curve includes an Rxy-Hx curve and a Ryx-Hy curve, and an Rxy-Hz curve and / or a Ryx-Hz curve, wherein the x direction and the y direction are coplanar with the magnetic induction device, and the x direction, the y direction, and the z direction are perpendicular to each other, and the steps of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor and respectively calibrating the standard change curves of the Hall resistance and each component magnetic field strength of the sample magnetic field sensor include: A scanning magnetic field in a preset direction is applied to the sample magnetic field sensor to calibrate the Rxy-Hx curve and the Ryx-Hy curve of the magnetic induction device, and the Rxy-Hz curve and / or the Ryx-Hz curve.

3. The magnetic field detection method according to claim 2, characterized in that: The preset direction includes an x ​​direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Rxy-Hx curve of the magnetic induction device includes: A preset current is passed through the magnetic induction device along the x direction, and a first scanning magnetic field is applied along the x direction, and a first Rxy corresponding to each Hx of the first scanning magnetic field is detected to obtain an Rxy-Hx curve.

4. The magnetic field detection method according to claim 2, characterized in that: The preset direction includes a y direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Ryx-Hy curve of the magnetic induction device includes: A preset current is passed through the magnetic induction device along the y direction, and a second scanning magnetic field is applied along the y direction, and a first Ryx corresponding to each Hy of the second scanning magnetic field is detected to obtain a Ryx-Hy curve.

5. The magnetic field detection method according to claim 2, characterized in that: The preset direction includes a z direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor to calibrate the Rxy-Hz curve of the magnetic induction device includes: A preset current is passed through the magnetic induction device along the x direction, and a third scanning magnetic field is applied along the z direction, and a second Rxy corresponding to each Hz of the third scanning magnetic field is detected to obtain an Rxy-Hz curve.

6. The magnetic field detection method according to claim 2, characterized in that: The preset direction includes a z direction, and the step of applying a scanning magnetic field in a preset direction to the sample magnetic field sensor and calibrating the Ryx-Hz curve of the magnetic induction device includes: A preset current is passed through the magnetic induction device along the y direction, and a fourth scanning magnetic field is applied along the z direction, and a second Ryx corresponding to each Hz of the fourth scanning magnetic field is detected to obtain a Ryx-Hz curve.

7. The magnetic field detection method according to any one of claims 3 to 6, characterized in that: The step of detecting the measured Hall resistance of the standard magnetic field sensor, querying the standard change curve according to the measured Hall resistance, and determining the magnetic field strength of each measured component of the magnetic unit includes: Passing the preset current along the positive x direction, measuring Rxy1 generated by the preset current, passing the preset current along the negative x direction, measuring Rxy2 generated by the preset current, and determining Rxy(Hx) generated by the x-direction component magnetic field on the magnetic induction device and / or Rxy(Hz) generated by the z-direction component magnetic field on the magnetic induction device according to Rxy1 and Rxy2; Passing the preset current along the positive y direction to measure Ryx3 generated by the preset current, passing the preset current along the negative y direction to measure Ryx4 generated by the preset current, and determining Ryx (Hy) generated by the y-direction component magnetic field on the magnetic induction device and / or Ryx (Hz) generated by the z-direction component magnetic field on the magnetic induction device according to Ryx3 and Ryx4; According to the Rxy(Hx) and Ryx(Hy), and Rxy(Hz) and / or Ryx(Hz), the corresponding Rxy-Hx curve, the Ryx-Hy curve, the Rxy-Hz curve or the Ryx-Hz curve are queried respectively to obtain the measured magnetic field strength of the x-direction component, the measured magnetic field strength of the y-direction component and the measured magnetic field strength of the z-direction component of the magnetic unit.

8. A magnetic field sensor, characterized in that: The magnetic field sensor includes: a base layer, a magnetic unit and a magnetic induction device; wherein the magnetic unit is deposited on the surface of the base layer, the magnetic induction device is a Hall bar structure, the magnetic induction device is deposited on the surface of the base layer, and the magnetic unit is the magnetic unit as described in any one of claims 1 to 7.

9. A magnetic field sensor manufacturing process, characterized in that: For manufacturing the magnetic field sensor as claimed in claim 8, the magnetic field sensor manufacturing process comprises the following steps: depositing a first passivation layer on the base layer; Depositing a magnetic thin film layer on the first passivation layer, and patterning the magnetic thin film layer to obtain a magnetic unit; depositing a second passivation layer on the magnetic unit; Depositing a magnetic induction film layer on the second passivation layer, and patterning the magnetic induction film layer to obtain a magnetic induction device with a Hall bar structure; The first passivation layer and the second passivation layer are patterned to obtain a magnetic field sensor.

10. The process for manufacturing a magnetic field sensor according to claim 9, characterized in that: The magnetic induction film layer is a multilayer heterogeneous structure of Ta / CoFeB / MgO / Ta.

Images