Vertical magneto-sensitive TMR sensor with continuously adjustable linear region

Abstract

The invention relates to a vertical magneto-sensitive TMR sensor with a continuously adjustable linear region, belongs to the technical field of magnetic sensors, and solves the problems that a vertical magnetic field is difficult to measure and the linear region of the same sensor cannot be regulated and controlled in the prior art. The sensor comprises a Si substrate, a piezoelectric film layer, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixed layer and a protective layer from bottom to top, and the vertical magnetic free layer sequentially comprises a first magnetic material layer, a first ultrathin metal layer and a second magnetic material layer from bottom to top. And the vertical magnetic fixed layer comprises a ferromagnetic layer, a second ultrathin metal layer and an antiferromagnetic coupling layer from bottom to top. According to the sensor, the vertical magnetic anisotropy of the vertical magnetic free layer of the vertical magneto-sensitive TMR sensor is regulated and controlled by utilizing the stress generated by the piezoelectric material, continuous regulation and control in a linear range can be realized, the application scene of the sensor is remarkably expanded, and the preparation process is good in compatibility, convenient to package, low in cost and suitable for large-scale mass production.

Description

Technical Field

[0001] This invention relates to the field of magnetic sensor technology, and more particularly to a vertical magnetic field (TMR) sensor with continuously adjustable linear region. Background Technology

[0002] With the development of spintronics, various magnetoresistive (MR) sensors have emerged (such as those based on AMR, GMR, and TMR effects). Their resistance changes linearly within a certain range with the external magnetic field, allowing measurement of the surrounding magnetic field by measuring the voltage across the device. These sensors are currently widely used in fields such as magnetic fields, current, position, vibration, sound, and angle. In these applications, the measurement of the corresponding physical quantity is achieved by measuring the change in sensor resistance caused by the magnetoresistive effect. Compared to AMR and GMR, TMR-based sensors have significant advantages in sensitivity, power consumption, operating temperature range, response speed, stability, and integration. Furthermore, AMR and GMR-based sensors can only measure magnetic fields within a thin-film plane and cannot measure perpendicular magnetic fields. Three-dimensional magnetic field measurement requires three-dimensional packaging, which introduces additional errors due to packaging precision.

[0003] In recent years, the emergence of perpendicular magnetic anisotropic TMR sensors has made it possible to realize single-chip three-dimensional magnetic sensing. Both the magnetic free layer and the reference layer have magnetic moment orientation perpendicular to the film surface, allowing direct sensing of the perpendicular magnetic field component, thus enabling three-dimensional magnetic field measurement without the need for three-dimensional packaging. However, perpendicular magnetization systems typically exhibit strong perpendicular magnetic anisotropy, resulting in a narrow linear response range for the sensor. For example, the linear region of a typical perpendicular TMR sensor is often limited to within several hundred Oe, making it difficult to directly use in strong magnetic field environments or applications requiring high dynamic range (such as motor magnetic field monitoring and vehicle magnetic navigation). If the linear range is preset through material selection or thickness adjustment, once fabricated, the measurement range cannot be adjusted according to the application scenario, limiting the sensor's application flexibility.

[0004] In addition, in order to achieve electrically controlled adjustment of vertical magnetic anisotropy, researchers have tried to use a coupling scheme between piezoelectric materials and magnetic heterostructures. One typical scheme is to use ferroelectric single crystals such as PMN-PT with high piezoelectric coefficients as substrates, and apply high voltage to the upper and lower surfaces to generate strain to adjust the anisotropy of the magnetic free layer deposited on it. However, (1) PMN-PT single crystal substrates are expensive, mechanically brittle, and have poor compatibility with standard semiconductor processes; (2) electrodes need to be fabricated on the back side of the substrate, which increases the complexity of photolithography, etching and wire bonding processes, which is not conducive to wafer-level manufacturing and integration; (3) most studies use a single ferromagnetic layer as the free layer, which has a limited magnetostriction coefficient, resulting in low strain-magnetic anisotropy coupling efficiency. It often requires the application of hundreds or even thousands of volts to achieve effective linear region adjustment, which consumes a lot of energy and has the risk of breakdown.

[0005] Therefore, how to achieve continuous adjustment of the linear operating range in vertical magnetic field measurement scenarios through low voltage and high efficiency, while meeting the requirements of low cost and thin-film mass production, has become a key technical bottleneck for the practical application of vertical magnetic sensitive TMR sensors. Summary of the Invention

[0006] In view of the above analysis, the present invention aims to provide a vertical magnetic sensitive TMR sensor with continuously adjustable linear region to solve one of the following problems: (1) the existing in-plane magnetization control mechanism is not suitable for vertical magnetic sensitive system, the single free layer structure relies on intrinsic magnetostriction effect, the control efficiency is limited, and it is difficult to achieve wide-range linear region on-demand modulation; (2) PMN-PT piezoelectric single crystal substrate is expensive, the back electrode preparation is complicated, and it is incompatible with CMOS semiconductor thin film process, which seriously restricts the mass production and commercial application of vertical magnetic sensitive TMR sensor.

[0007] The first aspect of this invention provides a vertical magnetic sensitive TMR sensor with continuously adjustable linear region. The sensor comprises a multilayer structure, from bottom to top: a Si substrate, a piezoelectric thin film layer, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixing layer, and a protective layer. The vertical magnetic free layer comprises a three-layer structure, from bottom to top: a first magnetic material layer, a first ultrathin metal layer, and a second magnetic material layer. The first magnetic material layer and the second magnetic material layer are magnetically coupled. The vertical magnetic fixing layer comprises a three-layer structure, from bottom to top: a ferromagnetic layer, a second ultrathin metal layer, and an antiferromagnetic coupling layer. The ferromagnetic layers in the vertical magnetic free layer and the vertical magnetic fixing layer each independently possess vertical magnetic anisotropy.

[0008] Furthermore, the first magnetic material layer in the vertical magnetic free layer is a Co / Pt superlattice multilayer film structure, a Co / Ni superlattice multilayer film structure, or a Co / Pd superlattice multilayer film structure.

[0009] Furthermore, the material of the second magnetic material layer in the vertical magnetic free layer is selected from CoFeB, CoFe, NiFeB or CoFeSiB.

[0010] Furthermore, the first ultrathin metal layer in the vertical magnetic free layer is selected from Ta, Cu, Ru, or Cr.

[0011] Furthermore, the material of the piezoelectric thin film layer is selected from ZnO, AlN, or PZT.

[0012] Furthermore, the material of the electrode layer is selected from at least one of Cr, Ta, Ru, and Au;

[0013] Furthermore, the material of the seed layer is selected from at least one of Ta, Cr, Ru and Pt.

[0014] Furthermore, the tunneling barrier layer is crystalline Al2O3 or MgO.

[0015] Furthermore, the ferromagnetic layer in the vertical magnetic fixing layer is selected from one of CoFeB, CoFe, FeB, or NiFeB;

[0016] Furthermore, the second ultrathin metal layer in the vertical magnetic fixing layer is selected from one of Cr, Ru, Ta or Cu.

[0017] Furthermore, the antiferromagnetic coupling layer in the vertical magnetic fixing layer has a multilayer film structure and vertical magnetic anisotropy, and is magnetically coupled to the ferromagnetic layer.

[0018] A second aspect of the present invention provides a method for manufacturing the sensor described in the first aspect, comprising the following steps:

[0019] S1. A piezoelectric thin film layer is deposited on a Si substrate using a thin film deposition process;

[0020] S2. A vertical magnetic sensitive TMR film layer is prepared on the piezoelectric thin film layer using a thin film deposition process to obtain the thin film precursor;

[0021] S3. Vacuum annealing is performed on the thin film precursor, and a magnetic field is applied in the vertical direction to promote thin film crystallization, thereby obtaining the sensor.

[0022] The vertical magnetic sensitive TMR film layer comprises, from bottom to top, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixed layer, and a protective layer, wherein the electrode layer and the protective layer serve as electrodes of the sensing element.

[0023] A third aspect of the present invention provides a linear region modulation method for the sensor described in the first aspect, comprising: applying a vertical electric field to a piezoelectric thin film layer to induce in-plane strain in the piezoelectric thin film, wherein the strain is transmitted to a vertical magnetic free layer to change its vertical magnetic anisotropy field, thereby controlling the linear range of the sensor.

[0024] Furthermore, the applied vertical electric field strength is 10-1000 V / μm, and the direction of the electric field is parallel to the polarization direction of the piezoelectric thin film layer.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] 1. This invention utilizes the strain-preferred action of the piezoelectric thin film layer on the first magnetic layer, whose vertical magnetic anisotropy is easily affected by deformation. Through interlayer exchange coupling, the vertical magnetic anisotropy field of the second magnetic layer is efficiently controlled, overcoming the problem of low strain control efficiency of the second magnetic layer. This achieves continuous and precise control in a linear range from -1000Oe to +1000Oe and above. The control efficiency is significantly improved compared to a single free layer structure, meeting the wide range requirements of vertical magnetic field measurement.

[0027] 2. This invention uses a Si substrate to deposit ZnO, AlN, or PZT piezoelectric thin films instead of expensive PMN-PT piezoelectric single-crystal substrates, and eliminates the need for single-crystal electrostrictive substrates, significantly reducing material costs. Furthermore, by integrating the electrode layer on the front side of the Si substrate, using the Si substrate as the lower electrode and the electrode layer as the upper electrode, the back electrode fabrication and wire bonding processes are eliminated. This invention's sensor, with its unique structure, is compatible with standard CMOS production lines such as magnetron sputtering, photolithography, and etching, and boasts good compatibility with supporting fabrication processes, low cost, and suitability for large-scale mass production.

[0028] 3. In the sensor of the present invention, both the vertical magnetic fixed layer and the vertical magnetic free layer have vertical magnetic anisotropy, and the magnetic moment is intrinsically perpendicular to the film surface, directly responding to the vertical magnetic field component to be measured. The vertical magnetic field can be accurately measured without three-dimensional packaging. By voltage regulating the vertical magnetic anisotropy field of the vertical magnetic free layer, the application of the sensor in multiple scenarios such as industrial motor monitoring and medical positioning is significantly broadened.

[0029] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0030] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0031] Figure 1 This is a schematic diagram of the structure of a Si substrate, a piezoelectric thin film layer, and a vertically magnetically sensitive TMR film layer.

[0032] Figure 2 This is a schematic diagram of the film structure of a magnetic sensor;

[0033] Figure 3 This is a schematic diagram of a vertical magnetic free layer film structure.

[0034] Figure label:

[0035] 1a. Si substrate; 1b. Piezoelectric thin film layer; 1c. Vertical magnetic sensitive TMR film layer;

[0036] 21. Electrode layer; 22. Seed layer; 23. Vertical magnetic free layer; 24. Tunneling barrier layer; 25. Ferromagnetic layer; 26. Second ultrathin metal layer; 27. Antiferromagnetic coupling layer; 28. Protective layer;

[0037] 31. First magnetic material layer; 32. First ultrathin metal layer; 33. Second magnetic material layer. Detailed Implementation

[0038] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0039] The first aspect of this invention provides a vertical magnetic sensitive TMR sensor with continuously adjustable linear region, such as... Figures 1-3 As shown, the sensor comprises a multi-layer structure, which, from bottom to top, consists of: a Si substrate, a piezoelectric thin film layer, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixing layer, and a protective layer.

[0040] In order to achieve significant vertical magnetic anisotropy control of the vertical magnetic free layer, the vertical magnetic free layer comprises a three-layer structure, consisting of a first magnetic material layer, a first ultrathin metal layer, and a second magnetic material layer from bottom to top; the first magnetic material layer and the second magnetic material layer are magnetically coupled.

[0041] The vertical magnetic fixing layer comprises a three-layer structure, consisting of a ferromagnetic layer, a second ultrathin metal layer, and an antiferromagnetic coupling layer from bottom to top.

[0042] The ferromagnetic layers in the vertical magnetic free layer and the vertical magnetic fixed layer each independently possess vertical magnetic anisotropy.

[0043] The electrode layer, seed layer, vertical magnetic free layer, tunneling barrier layer, vertical magnetic fixed layer, and protective layer can be collectively referred to as the vertical magnetic sensitive TMR film layer.

[0044] In this invention, a Si substrate + piezoelectric thin film layer design replaces the expensive PMN-PT single-crystal substrate, significantly reducing material costs without sacrificing linear output range control performance. Furthermore, the strain of the piezoelectric thin film layer acts on a first magnetic layer with a high magnetostriction coefficient, indirectly controlling a second magnetic layer with a low magnetostriction coefficient through interlayer exchange coupling. This avoids the efficiency reduction caused by direct control, enabling an anisotropic field change of over 30%, and continuously extending the linear range from 20 Oe to 200 Oe. Simultaneously, the sensor's vertical magnetic anisotropy system directly responds to the vertical magnetic field, eliminating the need for three-dimensional packaging. The front-integrated electrode layer further simplifies the packaging process, reduces packaging costs, and improves reliability, achieving a low-cost, high-efficiency, and wide-range vertical magnetic sensitive TMR sensor.

[0045] It is understood that the first magnetic material layer and the second magnetic material layer are ferromagnetically coupled.

[0046] In this invention, the thickness of the first ultrathin metal layer can be 0.3-1.5 nm.

[0047] According to some embodiments of the present invention, the first magnetic material layer in the vertical magnetic free layer is selected from Co / Pt superlattice multilayer film structure, Co / Ni superlattice multilayer film structure or Co / Pd superlattice multilayer film structure, and the second magnetic material layer in the vertical magnetic free layer is selected from CoFeB, CoFe, NiFeB or CoFeSiB.

[0048] In this invention, the first magnetic material layer is a superlattice multilayer film structure, and its strong perpendicular magnetic anisotropy serves as a control power source, overcoming the control efficiency bottleneck of single-layer structures. Simultaneously, the second magnetic material layer is selected from the aforementioned alloy material, ensuring a high-quality tunneling interface with the tunneling barrier layer. Furthermore, through interface exchange coupling of the first ultrathin metal layer, the anisotropic changes of the first magnetic layer are efficiently transferred to the second magnetic layer, achieving a significant improvement in control efficiency.

[0049] It is understood that the thickness of the first magnetic material layer is 5-30 nm, and the thickness of the second magnetic material layer is 1-10 nm.

[0050] In this invention, it should be noted that the superlattice multilayer film structure refers to a periodic artificial structure formed by alternating stacking of two or more different materials at the nanoscale.

[0051] For example, the first magnetic material layer is a Co / Pt superlattice multilayer film structure, which refers to a structure formed by alternating stacking of Co layers with a thickness of 0.5-2 nm and Pt layers with a thickness of 0.2-1 nm for 5-20 cycles, with a total thickness of 5-30 nm. The layer is deposited by magnetron sputtering at an Ar gas pressure of 0.3-0.8 Pa and room temperature, and the periodic structure is verified by X-ray reflectivity testing to ensure that the magnetic anisotropy meets the above requirements.

[0052] According to some aspects of the present invention, considering the interface exchange coupling efficiency, lattice matching and process compatibility, the first ultrathin metal layer in the vertical magnetic free layer is selected from Ta, Cu, Ru or Cr.

[0053] According to some embodiments of the present invention, the material of the piezoelectric thin film layer is selected from ZnO, AlN or PZT.

[0054] In this invention, the aforementioned material is in-plane isotropic and possesses a strong piezoelectric coefficient, which can effectively control the vertical magnetic anisotropy of the first magnetic material layer. Simultaneously, the piezoelectric thin film layer, the Si substrate, and the electrode layer constitute a vertical electric field-strain generation system. The Si substrate acts as the lower electrode, working in synergy with the upper electrode of the thin film. Electric field lines uniformly penetrate the piezoelectric layer, inducing in-plane isotropic strain and improving strain transfer efficiency. The seed layer serves as strain coupling and lattice template, both transmitting strain non-destructively to the first magnetic material layer and significantly enhancing vertical magnetic anisotropy. The first magnetic layer responds to strain by generating strong anisotropic changes, which are efficiently coupled to the second magnetic material layer through the first ultrathin metal layer, further improving electromagnetic control efficiency.

[0055] According to some aspects of the present invention, it is understood that the thickness of the piezoelectric thin film layer is 20-200 nm.

[0056] According to some aspects of the present invention, the material of the electrode layer is selected from at least one of Cr, Ta, Ru and Au, and the material of the seed layer is selected from at least one of Ta, Cr, Ru and Pt.

[0057] In this invention, the inventors discovered that the electrode layer and the seed layer are selected from the above-mentioned types, which can synergistically enhance each other and reduce the interfacial resistance of the material. Specifically, the electrode layer ensures the stability of the electric field and blocks oxygen diffusion, while the seed layer provides a lattice template and induces the vertical orientation growth of the magnetic layer. Together, they enhance magnetic anisotropy and tunneling efficiency, thereby improving the overall performance of the fabricated sensor.

[0058] In this invention, when a vertical voltage is applied between the Si substrate and the electrode layer in the sensor, the piezoelectric thin film layer generates in-plane strain. This strain is transmitted to the vertically magnetic free layer via a seed layer. The seed layer not only provides a good lattice epitaxial template to induce vertical anisotropic growth of the upper magnetic layer, but also ensures that the piezoelectric strain acts efficiently and uniformly on the first magnetic material layer. The vertical magnetic anisotropy field of the first magnetic material layer changes significantly with strain, and this change is cooperatively transmitted to the second magnetic material layer through ferromagnetic exchange coupling of the first ultrathin metal layer, thereby achieving continuous control of the magnetic anisotropy of the entire free layer.

[0059] It is understood that the thickness of the electrode layer is 50-300 nm, and the thickness of the seed layer is 5-30 nm.

[0060] According to some aspects of the present invention, the second magnetic material layer in the vertical magnetic free layer is selected from CoFeB, CoFe, NiFeB or CoFeSiB.

[0061] In this invention, it is necessary to ensure that the strain energy generated by the piezoelectric thin film effectively changes the vertical magnetic anisotropy field of the ferromagnetic material. Combined with the three-layer coupled vertical magnetic free layer structure of this invention, even if the magnetic anisotropy of the second magnetic material layer in contact with the tunneling barrier layer is difficult to control, it can be efficiently controlled through direct coupling with the easily controllable first magnetic material layer. Thus, while ensuring high tunneling magnetoresistance performance, a wide-range, sensitive and reversible voltage control of the sensor's linear range can be achieved.

[0062] In this invention, the ferromagnetic layer in the vertical magnetic fixing layer is magnetically coupled, so that the ferromagnetic layer is not disturbed by the external magnetic field.

[0063] According to an embodiment of the present invention, the tunneling barrier layer is Al2O3 or MgO.

[0064] In this invention, the tunneling barrier layer, located between the vertically magnetic free layer and the vertically magnetic fixed layer, is the core of the tunnel junction magnetoresistance effect. The inventors discovered that the tunneling barrier layer is selected from Al₂O₃ or MgO because they can form high-quality heterojunction interfaces with the ferromagnetic material (such as CoFeB) of the vertically magnetic free layer. Among them, the MgO barrier layer, due to its unique lattice matching relationship, can achieve a higher tunneling magnetoresistance ratio, thereby significantly improving the sensor's output signal sensitivity. Al₂O₃, as a mature barrier material, has good process stability, achieves continuous tunability over a wide linear range, and improves compatibility with the Si substrate.

[0065] It is understood that the thickness of the tunneling barrier layer is 0.8-1.5 nm.

[0066] According to an embodiment of the present invention, considering the stability of the magnetic moment, the ferromagnetic layer in the vertical magnetic fixing layer is selected from one of CoFeB, CoFe, FeB or NiFeB.

[0067] According to an embodiment of the present invention, considering the need to achieve interfacial magnetic coupling, the second ultrathin metal layer in the vertical magnetic fixing layer is selected from one of Ta, Cu, Ru or Cr.

[0068] According to an embodiment of the present invention, the antiferromagnetic coupling layer in the vertical magnetic fixing layer has a multilayer film structure and vertical magnetic anisotropy, and is magnetically coupled to the ferromagnetic layer.

[0069] In this invention, the antiferromagnetic coupling layer is selected from Co / Pt superlattice multilayer film structure, Co / Ni superlattice multilayer film structure, or Co / Pd superlattice multilayer film structure.

[0070] In this invention, the thickness of the second ultrathin metal layer can be 0.3-1.5 nm.

[0071] According to some embodiments of the present invention, the material of the protective layer is one of Cr, Ru, Pt, SiO2, and it is understood that the thickness of the protective layer is 5-20 nm.

[0072] A second aspect of the present invention provides a method for manufacturing the sensor described in the first aspect, comprising the following steps:

[0073] S1. A piezoelectric thin film layer is deposited on a Si substrate using a thin film deposition process, with the Si substrate serving as the lower electrode of the piezoelectric thin film;

[0074] S2. A vertical magnetic sensitive TMR film layer is prepared on the piezoelectric thin film layer using a thin film deposition process to obtain the thin film precursor;

[0075] S3. Vacuum annealing is performed on the thin film precursor, and a magnetic field is applied in the vertical direction to promote thin film crystallization, thereby obtaining the sensor.

[0076] The vertical magnetic sensitive TMR film layer comprises, from bottom to top, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixed layer, and a protective layer, wherein the electrode layer and the protective layer serve as electrodes of the sensing element.

[0077] In this invention, it is understood that the thin film deposition process can employ existing methods and parameters.

[0078] In this invention, the vacuum annealing process is carried out at a temperature of 200-400℃ for 0.5-3 hours, and the magnetic field strength of the magnetic field applied in the vertical direction is 0.5-3 Tesla.

[0079] In this invention, vacuum annealing under the above conditions and subsequent application of a magnetic field along the vertical direction enable the three-layer coupled structure of the vertical magnetic free layer to achieve a net magnetic moment of zero under zero field. Furthermore, in conjunction with the structure of the vertical magnetic fixed layer, the magnetic moment of the free layer can be reversibly flipped when the external magnetic field changes, thereby obtaining a linear response.

[0080] A third aspect of the present invention provides a linear region modulation method for the sensor described in the first aspect, comprising: applying a vertical electric field to a piezoelectric thin film layer to induce in-plane strain in the piezoelectric thin film, wherein the strain is transmitted to a vertical magnetic free layer to change its vertical magnetic anisotropy field, thereby controlling the linear range of the sensor.

[0081] According to some embodiments of the present invention, the applied vertical electric field strength is 10-1000 V / μm, and the electric field direction is parallel to the polarization direction of the piezoelectric thin film layer.

[0082] Specifically, a voltage is applied between the Si substrate and the electrode layer. At this time, the piezoelectric thin film layer generates in-plane isotropic strain. The strain is transmitted to the vertical magnetic free layer. Under the inverse magnetostriction effect of the magnetic material and the interfacial exchange coupling caused by the strain, the vertical magnetic anisotropy of the first magnetic material layer changes. The vertical magnetic anisotropy of the second magnetic material layer is also controlled by magnetic coupling, thereby changing the linear range of the sensor. At the same time, due to the strong ferromagnetic coupling between the ferromagnetic layer and the antiferromagnetic coupling layer in the vertical magnetic fixed layer, the vertical magnetic anisotropy of the vertical magnetic fixed layer is not affected by the strain of the piezoelectric thin film layer and the Si substrate.

[0083] Furthermore, when the magnetostriction coefficient of the second magnetic material layer is positive and the piezoelectric coefficient of the piezoelectric thin film layer is positive, applying a vertical electric field causes tensile strain, which reduces the vertical magnetic anisotropy field of the vertical magnetic free layer and increases the linear range of the sensor.

[0084] When the magnetostriction coefficient of the second magnetic material layer is positive and the piezoelectric coefficient of the piezoelectric thin film layer is negative, the application of a vertical electric field causes contraction strain, which enhances the vertical magnetic anisotropy field of the vertical magnetic free layer and reduces the linear range of the sensor.

[0085] Furthermore, when the magnetostriction coefficient of the second magnetic material layer is negative and the piezoelectric coefficient of the piezoelectric thin film layer is positive, applying a vertical electric field causes contraction strain, which enhances the vertical magnetic anisotropy field of the vertical magnetic free layer and reduces the linear range of the sensor; when the magnetostriction coefficient of the second magnetic material layer is negative and the piezoelectric coefficient of the piezoelectric thin film layer is negative, applying a vertical electric field causes tensile strain, which reduces the vertical magnetic anisotropy field of the vertical magnetic free layer and increases the linear range of the sensor.

[0086] For example, the preparation and control method of the sensor can be carried out according to the following process steps:

[0087] S1. Piezoelectric thin films such as ZnO, AlN, and PZT are deposited on a Si substrate using a thin film deposition process. The Si substrate also serves as the lower electrode of the piezoelectric thin film. The piezoelectric thin film layer will generate electro-induced strain under the action of a vertical voltage.

[0088] S2. A vertical magnetic sensitive TMR film layer is prepared on the piezoelectric thin film using a thin film deposition process, wherein the Si substrate and the electrode layer serve as the upper and lower electrodes of the piezoelectric thin film, and the electrode layer and the protective layer serve as the electrodes of the TMR sensing element. The vertical magnetic sensitive TMR film layer includes, from bottom to top, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixing layer, and a protective layer.

[0089] Among them, the protective layer protects the entire structure from oxidation, the vertical magnetic free layer is a vertical magnetic free layer with vertical magnetic anisotropy, the ferromagnetic layer is a magnetic reference layer with vertical magnetic anisotropy, the antiferromagnetic coupling layer is a multi-layer antiferromagnetic coupling structure with vertical magnetic anisotropy, and there is magnetic coupling between the ferromagnetic layer and the antiferromagnetic coupling layer.

[0090] S3. After the thin film preparation is completed, a thin film precursor is obtained. The thin film precursor is vacuum annealed and a magnetic field is applied in the vertical direction to promote thin film crystallization and improve the TMR resistance.

[0091] S4. By applying a voltage between the Si substrate and the electrode layer, an in-plane stress of a corresponding magnitude is generated. This stress is transmitted to the vertical magnetic free layer, and the magnetostriction effect of the magnetic material causes a change in the interface exchange coupling, which in turn causes a change in the vertical magnetic anisotropy of the vertical magnetic free layer. The stress generated by the piezoelectric thin film layer changes the magnetic anisotropy of the vertical magnetic free layer, thereby modulating the linear region of the TMR sensor.

[0092] The fabrication of the vertical magnetic sensitive TMR sensor with continuously adjustable linear region according to the present invention will be described in detail below through examples and comparative examples.

[0093] The linear range was tested according to the method in GB / T 28868-2012.

[0094] Example 1

[0095] S1. A 4-inch, heavily doped Si (100) wafer with a resistivity of 0.01 Ω·cm is selected as the substrate and the lower electrode. A 200 nm thick c-axis oriented ZnO piezoelectric film is deposited on the Si substrate using radio frequency magnetron sputtering. Subsequently, a Cr (5 nm) / Au (100 nm) stack is deposited on the ZnO film by electron beam evaporation as the upper electrode of the piezoelectric layer and the bottom electrode of the subsequent TMR device.

[0096] S2. On the substrate obtained in step S1, the following film structure (thickness unit: nm) is deposited sequentially from bottom to top using an ultra-high vacuum magnetron sputtering system: Ta (5nm) / [Co (0.6nm) / Pt (0.8nm)]⁵ / Ta (0.5nm) / Co 40 Fe 40 B 20 (1.2nm) / MgO(1.0nm) / Co 40 Fe 40 B 20 (1.5nm) / Ru(0.8nm) / [Co(0.6nm) / Pt(0.8nm)]5 / Ta(5nm).

[0097] The bottom layer, Ta (5nm), serves as the seed layer, [Co (0.6nm) / Pt (0.8nm)]⁵ / Ta (0.5nm) / Co 40 Fe 40 B 20 (1.2nm) together constitute a vertical magnetic free layer, in which the first magnetic material layer is a [Co / Pt] superlattice, the second magnetic material layer is CoFeB, and the two are ferromagnetically coupled through a first ultrathin metal layer (Ta layer). MgO (1.0nm) is a tunneling barrier layer, and Co 40 Fe 40 B 20 (1.5nm) / Ru(0.8nm) / [Co(0.6nm) / Pt(0.8nm)]5 constitutes a vertical magnetic fixing layer, in which CoFeB is a ferromagnetic layer, and [Co / Pt] superlattice is an antiferromagnetic coupling layer. The two are antiferromagnetically coupled through a second ultrathin metal layer (Ru layer), and the top layer Ta (5nm) is a protective layer (top electrode).

[0098] S3. Place the deposited thin film precursor in a vacuum annealing furnace and anneal at 300°C for 1 hour. At the same time, apply a magnetic field of 30000 Oe in the vertical direction to promote the crystallization of the CoFeB layer and obtain the functional film layer.

[0099] Example 2

[0100] The method described in Example 1 differs in that:

[0101] Piezoelectric thin film layer: An AlN thin film with a thickness of 500 nm was deposited on a Si substrate by reactive magnetron sputtering;

[0102] The first magnetic material layer of the vertical magnetic free layer is changed to [Co(0.5nm) / Ni(0.6nm)]. 10 Superlattice;

[0103] The tunneling barrier layer is Al2O3 (1.2 nm), formed by natural oxidation.

[0104] Comparative Example 1

[0105] The method of Example 1 is the same, except that the ZnO piezoelectric thin film layer is not deposited. The other film structure, materials and preparation process are exactly the same as those of Example 1.

[0106] Comparative Example 2

[0107] Following the method of Example 1 in CN115623857A, a PMN-PT(011) single-layer wafer was used as the substrate. Au electrodes were deposited on its upper and lower surfaces as piezoelectric electrodes. Subsequently, a multilayer film structure identical to that in Example 1 (starting from the seed layer) was deposited on it.

[0108] Comparative Example 3

[0109] The method is the same as in Example 1, except that the vertical magnetic free layer is replaced with a single layer of CoFeB (1.8 nm).

[0110] Test case

[0111] The functional films prepared in the examples and comparative examples were fabricated into independent units using photolithography, and electrodes and interconnects were then fabricated to obtain a sensor chip. Voltages were applied to the upper and lower surfaces of the piezoelectric thin film layer to modulate the magnetic anisotropy of the free layer. Under different voltages, the linear output range could be controlled. The sensor uses a Si substrate as the lower electrode of the piezoelectric thin film layer; and an electrode layer deposited above the piezoelectric thin film layer serves as the upper electrode of the piezoelectric layer and the bottom electrode of the TMR structure.

[0112] After the device is fabricated, the output of an external adjustable voltage source is connected to the electrode layer by standard wire bonding or probe contact, and the ground terminal of the voltage source is connected to the Si substrate, thereby forming a controllable vertical electric field path at both ends of the piezoelectric thin film layer. An adjustable voltage is applied between the Si substrate and the electrode layer, and then the linear range is tested according to the method of GB / T 28868-2012.

[0113] Table 1

[0114]

[0115] The above results show that the present invention (Examples 1 and 2) requires only a low voltage of 20V to extend the linear range of the sensor from ±500Oe to ±1000Oe and ±1300Oe, respectively, with a significant adjustment range. In contrast, Comparative Example 2, which uses a PMN-PT single-crystal substrate, requires a voltage as high as 1000V to achieve a similar effect, while Comparative Example 3, which uses a single-layer free layer, still has a lower adjustment effect (±800Oe) at 500V than the present invention. For example, ±1000Oe refers to a linear range from -1000Oe to +1000Oe.

[0116] As can be seen from Example 1 and Comparative Example 2, the front electrode integration of the present invention eliminates the need for back-side photolithography and bonding, significantly simplifying the packaging process. In Comparative Example 2, the PMN-PT single-crystal substrate is expensive, and voltage regulation based on PMN-PT requires electrode deposition on the back side of the substrate, which increases the difficulty of the process and packaging, hindering large-scale mass production.

[0117] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A vertical magnetic field-sensitive TMR sensor with continuously adjustable linear region, characterized in that, The sensor comprises a multi-layer structure, which, from bottom to top, consists of: a Si substrate, a piezoelectric thin film layer, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixing layer, and a protective layer. The vertical magnetic free layer comprises a three-layer structure, consisting of a first magnetic material layer, a first ultrathin metal layer, and a second magnetic material layer from bottom to top; the first magnetic material layer and the second magnetic material layer are magnetically coupled. The vertical magnetic fixing layer comprises a three-layer structure, consisting of a ferromagnetic layer, a second ultrathin metal layer, and an antiferromagnetic coupling layer from bottom to top. The ferromagnetic layers in the vertical magnetic free layer and the vertical magnetic fixed layer each independently possess vertical magnetic anisotropy.

2. The sensor according to claim 1, characterized in that, The first magnetic material layer in the vertical magnetic free layer is a Co / Pt superlattice multilayer film structure, a Co / Ni superlattice multilayer film structure, or a Co / Pd superlattice multilayer film structure.

3. The sensor according to claim 1, characterized in that, The material of the second magnetic material layer in the vertical magnetic free layer is selected from CoFeB, CoFe, NiFeB or CoFeSiB; And / or, the first ultrathin metal layer in the vertical magnetic free layer is selected from Ta, Cu, Ru or Cr.

4. The sensor according to claim 1, characterized in that, The material of the piezoelectric thin film layer is selected from ZnO, AlN or PZT.

5. The sensor according to claim 1, characterized in that, The material of the electrode layer is selected from at least one of Cr, Ta, Ru and Au; And / or, the material of the seed layer is selected from at least one of Ta, Cr, Ru and Pt.

6. The sensor according to claim 1, characterized in that, The tunneling barrier layer is crystalline Al2O3 or MgO.

7. The sensor according to claim 1, characterized in that, The ferromagnetic layer in the vertical magnetic fixing layer is selected from one of CoFeB, CoFe, FeB or NiFeB; And / or, the second ultrathin metal layer in the vertical magnetic fixing layer is selected from one of Cr, Ru, Ta or Cu; And / or, the antiferromagnetic coupling layer in the vertical magnetic fixing layer has a multilayer film structure and vertical magnetic anisotropy, and is magnetically coupled to the ferromagnetic layer.

8. A method for manufacturing a sensor according to any one of claims 1-7, characterized in that, Includes the following steps: S1. A piezoelectric thin film layer is deposited on a Si substrate using a thin film deposition process; S2. A vertical magnetic sensitive TMR film layer is prepared on the piezoelectric thin film layer using a thin film deposition process to obtain the thin film precursor; S3. Vacuum annealing is performed on the thin film precursor, and a magnetic field is applied in the vertical direction to promote thin film crystallization, thereby obtaining the sensor. The vertical magnetic sensitive TMR film layer comprises, from bottom to top, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixed layer, and a protective layer, wherein the electrode layer and the protective layer serve as electrodes of the sensing element.

9. A linear region modulation method for a sensor according to any one of claims 1-7, characterized in that, include: A vertical electric field is applied to the piezoelectric thin film layer, causing in-plane strain in the piezoelectric thin film. The strain is transmitted to the vertical magnetic free layer, changing its vertical magnetic anisotropy field, thereby controlling the linear range of the sensor.

10. The linear region modulation method according to claim 9, characterized in that, The applied vertical electric field strength is 10-1000 V / μm, and the direction of the electric field is parallel to the polarization direction of the piezoelectric thin film layer.

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