Magnetoresistive element, sensing equipment and preparation method of magnetoresistive element

Abstract

The invention discloses a magnetoresistive element, sensing equipment and a preparation method thereof, and relates to the technical field of magnetic field measurement. The magnetoresistive element comprises a magnetoresistive sub-element and a magnetic orbital transfer element, the magnetoresistive sub-element comprises a plurality of magnetic stacks, each magnetic stack at least comprises a free layer, and a magnetic sensitive axis of the magnetic stack is parallel to a plane of the free layer; the magnetic orbital transfer elements are arranged on the two sides of the free layer of each magnetic stack and used for converting an external magnetic field perpendicular to the plane of the free layer into a component parallel to the plane of the free layer. The magnetic orbital transfer element comprises ferroferric oxide nanoparticles. Through material selection of the magnetic orbital transfer element, the influence of a high-frequency environment on measurement of an external magnetic field perpendicular to a free layer plane is reduced, and the magnetic orbital transfer element has the technical effects of simple structure and easiness in implementation.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field detection technology, and in particular to a magnetoresistive element, a sensing device and a preparation method thereof. Background Art

[0002] Magnetoresistive elements such as TMR and GMR have strong single-direction magnetic sensitivity characteristics. A single magnetic sensitive body cannot achieve three-component measurement at the same time. The current mainstream method is to assemble and manufacture a three-axis magnetic sensor using multiple sensitive bodies, and its three-axis orthogonality and consistency are generally difficult to control. Therefore, magnetic track change elements are generally used to use their high magnetic permeability to guide the magnetic lines of force to direct the vertical Z-axis magnetic field to the XY plane, and then use the in-plane sensitive body for measurement, and finally complete the three-dimensional magnetic field measurement in the plane magnetic field measurement mode.

[0003] Soft magnetic materials represented by Permalloy generally have skin effect under high-frequency magnetic fields, which affects the normal function of the soft magnetic materials as magnetic switching elements, resulting in a large deviation between the measurement data of the magnetoresistive element and the actual situation. Summary of the invention

[0004] The main purpose of the present invention is to provide a magnetoresistive element, a sensing device and a preparation method thereof, aiming to solve the technical problem in the prior art that the magnetoresistive element with a magnetic track changing element cannot perform normal measurement in a high frequency environment.

[0005] To achieve the above object, a first aspect of the present invention provides a magnetoresistive element; the magnetoresistive element comprises: A magnetoresistive sub-element, comprising a plurality of magnetic stacks, each of the magnetic stacks comprising at least a free layer, and a magnetically sensitive axis of the magnetic stack being parallel to a plane of the free layer; The magnetic track-changing element is arranged on both sides of the free layer of each magnetic stack, and is used to convert the external magnetic field perpendicular to the free layer plane into a component parallel to the free layer plane; the magnetic track-changing element includes ferrosoferric oxide nanoparticles.

[0006] According to some embodiments of the present invention, the magnetic track-changing element includes a plurality of magnetic track-changing films; In a direction perpendicular to the plane of the free layer, each of the magnetic stacks is located below the magnetic track change film.

[0007] According to some embodiments of the present invention, the thickness of the magnetic track change film is greater than 2 μm.

[0008] According to some embodiments of the present invention, the magnetoresistive sub-element has a magnetoresistive effect, and preferably, the magnetoresistive sub-element is TMR, GMR or AMR; The magnetoresistive element has a Wheatstone bridge structure.

[0009] According to some embodiments of the present invention, the ferrosoferric oxide nanoparticles have superparamagnetism.

[0010] According to some embodiments of the present invention, the particle size of the ferrosoferric oxide nanoparticles is not greater than 11 nm.

[0011] To achieve the above object, a second aspect of the present invention provides a method for preparing a magnetoresistive element, the method comprising: Depositing a bottom electrode layer, a free layer, and a top electrode layer on a substrate in sequence, and obtaining at least one magnetic stack after tape-out processing; Applying high temperature magnetic field annealing to the at least one magnetic stack so that the magnetic stack has a preset magnetic sensitivity direction parallel to the free layer plane; Ferroferric oxide photoresist is deposited on both sides of each magnetic stack in the at least one magnetic stack, and a magnetoresistive element is obtained through patterning.

[0012] According to some embodiments of the present invention, before depositing ferroferric oxide photoresist on both sides of each magnetic stack in the at least one magnetic stack, the method further includes: The photoresist is mixed with ferroferric oxide particles and stirred for 5 to 15 minutes to obtain the ferroferric oxide photoresist.

[0013] According to some embodiments of the present invention, the preparation method comprises: Depositing a bottom electrode layer, a free layer, and a top electrode layer on a substrate in sequence, and obtaining at least one magnetic stack through tape-out; Depositing ferroferric oxide photoresist on both sides of each magnetic stack in the at least one magnetic stack, and performing patterning treatment; A high temperature magnetic field annealing is applied to the at least one magnetic stack to obtain the magnetoresistive element according to any one of claims 1 to 6; wherein, the magnetic stack has a preset magnetic sensitivity direction parallel to the free layer plane.

[0014] To achieve the above object, a third aspect of the present invention provides a sensing device, the sensing device comprising a magnetoresistive element; The magnetoresistive element is the magnetoresistive element mentioned above, or a magnetoresistive element made by the above-mentioned preparation method.

[0015] Therefore, compared with the prior art, the present invention has the following beneficial effects: The magnetoresistive element disclosed in the present invention includes a magnetoresistive sub-element and a magnetic track-changing element. The magnetoresistive sub-element includes a plurality of magnetic stacks, each magnetic stack includes at least a free layer, and the magnetic sensitive axis of the magnetic stack is parallel to the free layer plane; the magnetic track-changing element is arranged on both sides of the free layer of each magnetic stack, and is used to convert the external magnetic field perpendicular to the free layer plane into a component parallel to the free layer plane; the magnetic track-changing element includes ferroferric oxide nanoparticles. The present invention reduces the influence of the high-frequency environment on the magnetoresistive element to realize the external magnetic field measurement perpendicular to the free layer plane by replacing the material of the magnetic track-changing element, and has the technical effect of simple structure and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention 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, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0017] Figure 1 is a schematic structural diagram of a magnetoresistive element according to an embodiment of the present invention; Figure 2 This is a simulation diagram of the magnetic field strength around the iron-nickel alloy under a high-frequency magnetic field; Figure 3 A simulation diagram of the magnetic field strength around the magnetic track change element of an embodiment of the present invention under a high-frequency magnetic field; Figure 4 A schematic structural diagram of a magnetoresistive element according to another embodiment of the present invention; Figure 5 Schematic diagram of the process of manufacturing a magnetoresistive element according to an embodiment of the present invention.

[0018] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0021] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] Magnetoresistive elements such as TMR and GMR have strong single-direction magnetic sensitivity characteristics. A single magnetic sensitive body cannot achieve three-component measurement at the same time. The current mainstream method is to assemble and manufacture a three-axis magnetic sensor using multiple sensitive bodies, and its three-axis orthogonality and consistency are generally difficult to control. Therefore, magnetic track change elements are generally used to use their high magnetic permeability to guide the magnetic lines of force to direct the vertical Z-axis magnetic field to the XY plane, and then use the in-plane sensitive body for measurement, and finally complete the three-dimensional magnetic field measurement in the plane magnetic field measurement mode.

[0023] Soft magnetic materials represented by iron-nickel alloys generally have skin effect under high-frequency magnetic fields, which affects the normal use of soft magnetic materials as magnetic track-changing components.

[0024] In an external magnetic field environment with a frequency of 10kHz and a magnetic field strength of 0.9T, the magnetic field strength simulation diagram around the iron-nickel alloy is as follows Figure 2 As shown. Figure 2 The four corners of the NiFe alloy have a significantly higher magnetic field strength than the interior, and the magnetic field distribution on the NiFe alloy is uneven, which easily leads to a large deviation in the measurement results of the magnetoresistive element. Therefore, the NiFe alloy is not suitable as a magnetic track change element under high-frequency magnetic fields.

[0025] The embodiment of the present invention provides a magnetoresistive element suitable for realizing magnetic field measurement under high-frequency magnetic field. The magnetoresistive element uses ferroferric oxide nanoparticles as magnetic track changing elements.

[0026] In an external magnetic field environment with a frequency of 10 kHz and a magnetic field strength of 0.12 T, the magnetic field strength simulation diagram around the magnetic track change element of the embodiment of the present invention is as follows: Figure 3 As shown. Figure 3 The magnetic field intensity distribution range around the ferroferric oxide magnetic track change element is uniform, ranging from 0.1 to 0.11 T, and is much higher than the magnetic field intensity of the iron-nickel alloy under the high-frequency magnetic field, and does not attenuate the magnetic field intensity of the external magnetic field. Therefore, the ferroferric oxide magnetic track change element can be used as a magnetic track change element under the high-frequency magnetic field.

[0027] Specifically, the magnetoresistive element of an embodiment of the present invention includes a magnetoresistive sub-element and a magnetic track-changing element, wherein the magnetoresistive sub-element includes a plurality of magnetic stacks, each magnetic stack includes at least a free layer, and the magnetic sensitive axis of each magnetic stack is parallel to the free layer plane where the free layer is located; the magnetic track-changing element is arranged on both sides of the free layer, and is used to convert an external magnetic field perpendicular to the free layer plane into a component parallel to the free layer plane, and the magnetic track-changing element includes ferroferric oxide nanoparticles.

[0028] In one embodiment of the present invention, Figure 1 As shown, the magnetic stack 10 in the magnetoresistive element includes a substrate 11 and a bottom electrode layer 12, a free layer 13 and a top electrode layer 14 sequentially arranged above the substrate 11, and the magnetic track changing element includes magnetic track changing films 20 respectively arranged on both sides of the free layer 13, and the corners of each magnetic track changing film 20 are close to the magnetic stack 10; at the same time, in the direction perpendicular to the plane of the free layer, the magnetic stack 10 is located below the magnetic track changing film 20.

[0029] The magnetic stack and the magnetic track change film are generally non-contact, and there is an insulating layer 16 between the magnetic stack and the magnetic track change film. The insulating layer 16 is made of silicon dioxide or silicon nitride. The insulating layer 16 has an insulating layer plane parallel to the substrate plane for the magnetic track change film to be deposited.

[0030] It should be understood that the material of the insulating layer is an insulating material, and the insulating material is not limited to silicon dioxide and silicon nitride.

[0031] An insulating filling layer 15 is filled between the insulating layer 16 and the substrate 11, and the two magnetic stacks 10 are separated by the insulating filling layer 15. The insulating filling layer 15 can be made of silicon dioxide, silicon nitride or other insulating materials, which are not specifically limited here.

[0032] In this embodiment, each magnetic track change film 10 in the magnetic track change element senses an external magnetic field perpendicular to the free layer plane and converts the external magnetic field into a magnetic field component parallel to the free layer plane, and senses the magnetic field component parallel to the free layer plane through the free layer, thereby realizing the induction of the magnetic field perpendicular to the free layer plane.

[0033] Furthermore, the embodiment of the present invention reduces the influence of the skin effect on the external magnetic field measurement perpendicular to the free layer plane of the magnetoresistive element in a high-frequency environment by replacing the material of the magnetic track changing element, and has a technical effect of simple structure and easy implementation.

[0034] Furthermore, the magnetic stack in the magnetoresistive element of the embodiment of the present invention has a magnetoresistive effect, and the magnetoresistive element may be TMR, GMR, AMR or other elements having a magnetoresistive effect.

[0035] To facilitate magnetic field measurement, the magnetoresistive element of the embodiment of the present invention has a Wheatstone bridge structure, and the magnetic field information of the current position is obtained through the differential signal output by the Wheatstone bridge. The Wheatstone bridge structure is preferably a Wheatstone full bridge structure.

[0036] In the magnetoresistive element of the embodiment of the present invention, the magnetic track-changing film includes iron tetroxide nanoparticles, and the ferroferric oxide nanoparticles have superparamagnetism. Preferably, the particle size of the ferroferric oxide particles is not greater than 11 nm.

[0037] In order to improve the magnetic track changing effect, the thickness of the magnetic track changing film in the magnetoresistive element of the embodiment of the present invention is preferably greater than 2 μm.

[0038] In another embodiment of the present invention, Figure 4 As shown, the magnetic stack 10 in the magnetoresistive element includes a substrate 11 and a bottom electrode layer 12, a pinning layer 18, a pinned layer 17, a tunneling layer 19, a free layer 13 and a top electrode layer 14 arranged in sequence above the substrate 11, and the magnetic track change film 20 in the magnetic track change element is close to both sides of the top electrode layer 14; in a direction perpendicular to the plane of the free layer, the magnetic stack 10 is located below the magnetic track change film 20, and the magnetic stack 10 and the magnetic track change film 20 are non-contacting, and an insulating layer 16 is included between the magnetic stack 10 and the magnetic track change film 20, and the material of the insulating layer 16 is silicon dioxide, silicon nitride or other insulating materials. Further, an insulating filling layer 15 is also included between the insulating layer and the substrate, and the material of the insulating filling layer 15 can be silicon dioxide, silicon oxide or other insulating materials, and it is not limited here that it is the same or different from the material of the insulating layer 16.

[0039] The embodiment of the present invention also provides a method for preparing a magnetoresistive element. The magnetoresistive element is the magnetoresistive element mentioned above.

[0040] like Figure 5 As shown, a method for preparing a magnetoresistive element provided by an embodiment of the present invention comprises the following steps: S100: depositing a bottom electrode layer, a free layer, and a top electrode layer on a substrate in sequence, and obtaining at least one magnetic stack after tape-out processing; Specifically, it includes: processing a substrate, depositing a multilayer film on the surface of the processed substrate by magnetron sputtering, and obtaining a plurality of magnetic stacks after wafer processing. The multilayer film includes at least a bottom electrode layer, a free layer and a top electrode layer.

[0041] It should be understood that the multilayer film may also include a pinning layer, a pinned layer, and a non-magnetic layer or a tunneling layer disposed between the pinned layer and the free layer, which is not specifically limited herein.

[0042] The method further comprises filling insulating material between each magnetic stack to obtain an insulating filling layer, wherein the insulating material may be silicon dioxide or silicon nitride; The method also includes: depositing insulating material on the insulating filling layer and the magnetic stack layer to obtain an insulating layer, which may be silicon dioxide or silicon nitride, for covering the surface of the magnetic stack.

[0043] S200: applying high temperature magnetic field annealing to at least one magnetic stack, so that the magnetic stack has a preset magnetic sensitivity direction parallel to the free layer plane; wherein the magnetic field direction of the magnetic field applied to at least one magnetic stack is parallel to the free layer plane where the free layer is located; Specifically, it includes: placing the wafer with at least one magnetic stack obtained in step S100 in an annealing furnace for high-temperature magnetic field annealing for a certain period of time, so that the free layer in the magnetic stack has a magnetic sensitivity axis parallel to the free layer plane. After the annealing is completed, the magnetic sensitivity direction of the magnetic stack is a preset direction parallel to the free layer plane.

[0044] S300: depositing ferroferric oxide photoresist on both sides of each magnetic stack in at least one magnetic stack, and patterning the magnetoresistive element.

[0045] Specifically, it includes: depositing ferroferric oxide photoresist on the wafer obtained by S200 high temperature magnetic field annealing, and defining the position of the ferroferric oxide magnetic switching element to be located on both sides of the magnetic stack by graphical means, thereby obtaining a magnetoresistive element.

[0046] Viewed from a direction perpendicular to the free layer plane, the ferroferrite track change element is located above the magnetic stack. Preferably, the bottom corner of the ferroferrite track change element is close to the edge of the top electrode layer in the magnetic stack.

[0047] Before depositing the ferroferric oxide photoresist, the method further includes: mixing the photoresist with ferroferric oxide nanoparticles and stirring for a certain time to obtain the ferroferric oxide photoresist; the stirring time may be 5 to 15 minutes, which is used to fully mix the ferroferric oxide nanoparticles and the photoresist, and the time is not specifically limited.

[0048] In a method for preparing a magnetoresistive element according to another embodiment of the present invention, the method can also be implemented by the following steps: Step S110: depositing a bottom electrode layer, a free layer, and a top electrode layer on the substrate in sequence, and obtaining at least one magnetic stack through tape-out; Specifically, it includes: processing a substrate; depositing a multilayer film on the processed substrate surface by magnetron sputtering; and obtaining a plurality of magnetic stacks and an insulating filling layer located between the magnetic stacks, and an insulating layer located above the insulating filling layer and covering the top layer of the magnetic stack through wafer processing.

[0049] Step S120: depositing ferroferric oxide photoresist on both sides of each magnetic stack in at least one magnetic stack, and performing patterning treatment; Specifically, the method includes: mixing ferroferric oxide nanoparticles with photoresist to obtain ferroferric oxide photoresist; depositing ferroferric oxide photoresist on the insulating layer in the wafer obtained in step S110; hardening the ferroferric oxide photoresist by graphic processing, and limiting its position on both sides above the magnetic stack.

[0050] Step S130: applying a high temperature magnetic field annealing to at least one magnetic stack to obtain a magnetoresistive element; Specifically, it includes: placing the wafer obtained in step S120 in an annealing furnace, and subjecting it to high-temperature magnetic field annealing for a period of time, so that the free layer in the magnetic stack has a magnetic sensitivity axis parallel to the free layer plane.

[0051] The magnetic field direction of the magnetic field applied to the annealing furnace may be parallel to the free layer plane.

[0052] It should be noted that the magnetic field applied to the annealing furnace can also be transmitted to the magnetic stack through the magnetic track change element. When the magnetic field applied to the annealing furnace is transmitted to the magnetic stack through the magnetic track change element, the direction of the magnetic field during high temperature annealing can also be perpendicular to the free layer plane. This is not specifically limited here.

[0053] The embodiment of the present invention further provides a sensing device, which includes a magnetoresistive element. The magnetoresistive element may be the aforementioned magnetoresistive element, or a magnetoresistive element manufactured by the aforementioned manufacturing method.

[0054] The sensor device can at least realize magnetic field measurement.

[0055] In some embodiments of the present invention, the sensing device can also realize current measurement, position detection, switch state detection, angle detection and other functions related to magnetic field measurement through magnetic field measurement.

[0056] Since the sensing device includes all implementations of all embodiments of the above-mentioned magnetoresistive element or the method for preparing the above-mentioned magnetoresistive element, it at least has all the beneficial effects brought by all the above-mentioned implementations, which will not be described one by one here.

[0057] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A magnetoresistive element, characterized in that: include: A magnetoresistive sub-element, comprising a plurality of magnetic stacks, each of the magnetic stacks comprising at least a free layer, and a magnetically sensitive axis of the magnetic stack being parallel to a plane of the free layer; The magnetic track-changing element is arranged on both sides of the free layer of each magnetic stack, and is used to convert the external magnetic field perpendicular to the free layer plane into a component parallel to the free layer plane; the magnetic track-changing element includes ferrosoferric oxide nanoparticles.

2. The magnetoresistive element according to claim 1, wherein: The magnetic track-changing element includes a plurality of magnetic track-changing films; In a direction perpendicular to the plane of the free layer, each of the magnetic stacks is located below the magnetic track change film.

3. The magnetoresistive element according to claim 2, characterized in that The thickness of the magnetic track-changing film is greater than 2 μm.

4. The magnetoresistive element according to claim 1, wherein: The magnetoresistive element has a magnetoresistive effect; the magnetoresistive element has a Wheatstone bridge structure; Preferably, the magnetoresistive element is TMR, GMR or AMR.

5. The magnetoresistive element according to claim 1, wherein: The ferrosoferric oxide nanoparticles have superparamagnetism.

6. The magnetoresistive element according to claim 5, characterized in that The particle size of the ferrosoferric oxide nanoparticles is not greater than 11 nm.

7. A method for preparing a magnetoresistive element, characterized in that: include: Depositing a bottom electrode layer, a free layer, and a top electrode layer on a substrate in sequence, and obtaining at least one magnetic stack after tape-out processing; Applying high temperature magnetic field annealing to the at least one magnetic stack so that the magnetic stack has a preset magnetic sensitivity direction parallel to the free layer plane; Ferroferric oxide photoresist is deposited on both sides of each magnetic stack in the at least one magnetic stack, and patterned to obtain the magnetoresistive element according to any one of claims 1 to 6.

8. The preparation method according to claim 7, characterized in that: Before depositing ferroferric oxide photoresist on both sides of each magnetic stack in the at least one magnetic stack, the method further includes: The photoresist is mixed with ferroferric oxide particles and stirred for 5 to 15 minutes to obtain the ferroferric oxide photoresist.

9. The preparation method according to claim 7, characterized in that: include: Depositing a bottom electrode layer, a free layer, and a top electrode layer on a substrate in sequence, and obtaining at least one magnetic stack through tape-out; Depositing ferroferric oxide photoresist on both sides of each magnetic stack in the at least one magnetic stack, and performing patterning treatment; A high temperature magnetic field annealing is applied to the at least one magnetic stack to obtain the magnetoresistive element according to any one of claims 1 to 6; wherein the magnetic stack has a preset magnetic sensitivity direction parallel to the free layer plane.

10. A sensing device, characterized in that: including a magnetoresistive element; The magnetoresistive element is the magnetoresistive element described in any one of claims 1 to 6, or a magnetoresistive element manufactured by the manufacturing method described in any one of claims 7 to 9.

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