An isotropic magnetically sensitive material, a micro magnetic sensor and its fabrication method

Abstract

This invention discloses an isotropic magnetically sensitive material, a micro magnetic sensor, and a method for fabricating the same. The isotropic magnetically sensitive material is a thin film with a magnetoresistive effect, and its morphology is a roll with a diameter of 3-300 micrometers and a length of 20-2000 micrometers. The micro magnetic sensor is realized by using two sets of the above-mentioned flexible magnetically sensitive micro-rolls and a fixed resistor to form a Wheatstone bridge structure, a first substrate, a bottom electrode, and wires. This isotropic micro magnetic field sensor can directly measure the magnitude of a magnetic field without being sensitive to the direction of the magnetic field. The manufacturing process is relatively low, and it can detect external magnetic fields of up to 7T without damage.

Description

Technical Field

[0001] This invention belongs to the field of magnetic sensitive material device technology, and particularly relates to an isotropic magnetic sensitive material, a micro magnetic sensor and its preparation method. Background Technology

[0002] In certain areas of consumer electronics and industrial control, isotropic magnetic field detection is required, meaning the magnitude of the magnetic field needs to be obtained while its direction is ignored. However, traditional magnetic field sensors are typically only sensitive to a single axis. To achieve isotropic magnetic field detection, multi-chip combinations or triaxial chips are needed for comprehensive calculations, increasing the complexity and cost of implementation.

[0003] Magnetic sensors based on magnetic materials are inevitably affected by the direction of the magnetic field due to magnetic anisotropy, making it difficult to measure isotropic magnetic fields with a single material. Among various magnetic sensing material technologies, strongly correlated perovskite oxide materials such as La... 0.67 Sr 0.33 MnO3, La 0.67 Ba 0.33 The colossal magnetoresistance effect in MnO3 exhibits a different magnetoresistance change mechanism than giant magnetoresistance and tunneling magnetoresistance, with a near-isotropic magnetoresistance response, making it promising for isotropic testing scenarios. Furthermore, it can measure applied magnetic fields exceeding 1T without damage, far exceeding the measurement range of magnetoresistive sensors. However, La... 0.67 Sr 0.33 MnO3, La 0.67 Ba 0.33 The magnetic anisotropy of MnO3 material itself will still damage its isotropic response, and the two materials mentioned above need to be grown on specific single-crystal substrates to achieve good performance, which greatly increases the cost. Summary of the Invention

[0004] In view of the current research status quo regarding the high complexity of existing isotropic magnetic field detection processes and the fact that the performance of thin film materials based on the colossal magnetoresistance effect does not meet the standards for isotropic magnetic field sensors, this invention proposes an isotropic magnetic sensitive material, a micro magnetic sensor, and its fabrication method.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: According to one aspect of the present invention, an isotropic magnetic sensitive material is provided, which is a micron-roll magnetic sensitive material, which is a thin film with magnetoresistance effect, and its shape is a roll with a diameter of 3 to 300 micrometers and a length of 20 to 2000 micrometers.

[0006] Optionally, it exhibits a magnetoresistive effect above room temperature.

[0007] Optionally, its resistance value changes linearly with the magnitude of the external magnetic field within a certain range, but is not sensitive to the direction of the external magnetic field.

[0008] Optionally, a wet transfer method can be used to transfer the magnetically sensitive material to any substrate, and its curled state is basically restored after drying and settling.

[0009] Optionally, the thickness of the film is 1 to 100 nanometers.

[0010] According to another aspect of the present invention, a miniature magnetic sensor is also provided, comprising: The first substrate, which is any insulating substrate, provides support for materials and devices; The bottom electrode is a patterned conductive metal strip sputtered on the first substrate and disposed above the first substrate; A flexible magnetic sensitive material, which is any of the isotropic magnetic sensitive materials described above, has two metal electrodes plated at both ends, and the two metal electrodes are respectively in contact with the bottom electrode and are disposed above the bottom electrode. A fixed resistor, whose resistance is equal to that of the isotropic magnetic sensitive material under conditions without an external magnetic field, is a thin film resistor on the first substrate or an external resistor, and is disposed above the bottom electrode. A wire is a conductive thin film deposited on a first substrate that connects a flexible magnetically sensitive material to a fixed resistor.

[0011] Optionally, two sets of flexible magnetic sensitive materials and two fixed resistors are used. The two sets of flexible magnetic sensitive materials and the fixed resistors are connected at intervals to form a Wheatstone bridge. The input and output of the isotropic miniature magnetic sensor are the input and output of the Wheatstone bridge. The output voltage of the isotropic miniature magnetic sensor changes linearly with the magnitude of the external magnetic field within the range and is not sensitive to the direction of the magnetic field.

[0012] According to another aspect of the present invention, a method for fabricating an isotropic magnetically sensitive material and a micro magnetic sensor is also provided, comprising the following steps: A sacrificial layer capable of being wet-etched is grown on a second substrate; A strain layer is grown above the sacrificial layer; A magnetically sensitive material layer with magnetoresistance properties is grown above the strained layer; Metal electrodes are fabricated on top of the magnetically sensitive material layer using photolithography or a mask; The sacrificial layer / strain layer / magnetically sensitive material layer is etched into strips using photolithography or laser engraving methods; A solution capable of etching the sacrificial layer is dripped into one side of the short side of the etched strip using a capillary tube, and the magnetic sensitive material layer slowly curls up to form a micron-sized magnetic sensitive material. In addition, a first substrate is prepared, and a bottom electrode and a fixed thin film resistor are deposited on the surface of the first substrate. Micron-sized magnetically sensitive material is transferred to a first substrate, and the electrode end is brought into contact with the bottom electrode to obtain the micro magnetic sensor described above.

[0013] Optionally, the first substrate, sacrificial layer, strain layer, and magnetically sensitive material layer all have similar cell parameters. The cell parameters of the strain layer are slightly smaller or slightly larger than those of the substrate material layer. After the sacrificial layer is etched, it causes the magnetically sensitive thin film layer to roll inward and keep the two electrodes facing outward, so that it can contact the bottom electrode in the first substrate.

[0014] Optionally, after the sacrificial layer is etched and the first substrate is ultrasonically cleaned, the first substrate can still be used for thin film growth.

[0015] Compared with existing technologies, the present invention has the following advantages: 1. The isotropic miniature magnetic field sensor provided by this invention can directly measure the magnitude of a magnetic field without being sensitive to its direction. It can detect external magnetic fields of up to 7T or more without damage, far exceeding the measurement range of conventional magnetoresistive sensors.

[0016] 2. The isotropic miniature magnetic field sensor provided by this invention uses only a single magnetic sensitive thin film material to fabricate the sensor device, eliminating the need for multiple sensor combinations for calculation, and thus has relatively low process complexity.

[0017] 3. The isotropic magnetic sensitive material provided by the present invention is prepared by wet etching process, wherein the substrate layer can be reused repeatedly to save costs. Attached Figure Description

[0018] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram and photograph of a magnetically sensitive micron-roll material according to an embodiment of the present invention; Figure 2 This is a top view schematic diagram of an isotropic magnetic field sensor according to an embodiment of the present invention; Figure 3 This is a side view of an isotropic magnetic field sensor according to an embodiment of the present invention; Figure 4 This is a comparison between the magnetic field response output results of the magnetically sensitive micron-roll material and the magnetic field response output results of the thin film according to embodiments of the present invention; Figure 5This is a process flow diagram of the fabrication of an isotropic magnetic field sensor according to an embodiment of the present invention; Among them, 101 is the first substrate; 102 is the flexible magnetic sensitive material; 103 is the bottom electrode; 104 is the fixed resistor; 105 is the metal electrode; and 106 is the metal electrode. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0021] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. Where the terms "first," "second," and "third" are used for descriptive purposes and to distinguish technical features, they should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The embodiments of this invention will now be described according to its overall structure.

[0023] like Figure 1 As shown, the present invention provides a schematic diagram of the structure of an isotropic magnetic sensitive material and an actual scanning electron microscope image. The isotropic magnetic sensitive material is a micron-roll magnetic sensitive material with a diameter of 3~300 micrometers and a length of 20~2000 micrometers. It is a thin film with a thickness of 1~100 nanometers and a magnetoresistance effect.

[0024] Isotropic magnetic sensitive materials exhibit magnetoresistance above room temperature. Preferably, the isotropic magnetic sensitive material can be La. 0.67 Sr 0.33 MnO3, La 0.67 Ba 0.33 MnO3, etc.

[0025] The resistance of isotropic magnetic sensitive materials changes linearly with the magnitude of the external magnetic field within a certain range, but is not sensitive to the direction of the external magnetic field.

[0026] This method involves using a wet etching process to detach the strained layer from the substrate and allow it to naturally curl. Specifically, a wet transfer method can be used to transfer the magnetically sensitive material to any substrate, and after drying and settling, its curled state is essentially restored. In other words, the isotropic magnetically sensitive material is a micron-roll with a diameter of 3–300 micrometers and a length of 20–2000 micrometers, obtained by peeling a thin film with a magnetoresistance effect from the substrate using a wet etching process and allowing it to naturally curl.

[0027] like Figure 2 The diagram shown is a top view of an isotropic miniature magnetic sensor. The miniature magnetic sensor comprises: a first substrate 101, a bottom electrode 103, two sets of flexible magnetically sensitive materials 102, two fixed resistors 104, and wires. From bottom to top: The first substrate 101 can be any insulating substrate, providing support for materials and devices; The bottom electrode 103 is a patterned conductive metal strip sputtered on the first substrate 101 and disposed above the first substrate 101; The flexible magnetic sensitive material 102 is the isotropic magnetic sensitive material mentioned above, with two metal electrodes plated at both ends. The two metal electrodes are in contact with the bottom electrode 103 and are disposed above the bottom electrode 103. The fixed resistor 104 is a resistor whose resistance is equal to that of the isotropic magnetic sensitive material under the condition of no external magnetic field. It is a thin film resistor or an external resistor on the first substrate 101 and is disposed above the bottom electrode 103. The wire is a conductive thin film deposited on the first substrate 101 that connects the flexible magnetic sensitive material 102 and the fixed resistor 104.

[0028] The system employs two sets of flexible magnetic sensitive materials 102 and two fixed resistors 104. The two sets of flexible magnetic sensitive materials 102 and fixed resistors 104 are connected at intervals to form a Wheatstone bridge. The input and output of the isotropic micro magnetic sensor are the input and output of the Wheatstone bridge. The output voltage of the isotropic micro magnetic sensor changes linearly with the magnitude of the external magnetic field within its range and is insensitive to the direction of the magnetic field.

[0029] Specifically, the flexible magnetically sensitive material 102, the bottom electrode 103, and the custom electrode form a Wheatstone bridge structure. The input terminals are V+ and V-, and the output terminals are Vout+ and Vout-. The input voltage is Uin. When the resistance of the fixed resistor 104 is R, the resistance change of the thin film under the magnetic field is ΔR, and the output voltage signal U = ΔR / 2(R + ΔR) × Uin. Since R is much larger than ΔR, its output voltage signal is approximately U = ΔR / 2R × Uin.

[0030] like Figure 3 As shown, this is a side view of the micro magnetic sensor. Metal electrodes 105 and 106 are plated at both ends of the flexible magnetically sensitive material 102. After being rolled up, the flexible magnetically sensitive material 102 is exposed on the surface, forming an ohmic contact with the bottom electrode 103. The shape of the micro-roll significantly reduces its magnetic anisotropy, resulting in the sensor being insensitive to the direction of external magnetic fields.

[0031] like Figure 4 The figure shows a comparison between the magnetic field response output of the magnetically sensitive micron-roll material and the magnetic field response output of the thin film in an embodiment of the present invention. It can be seen that under the action of the X, Y, and Z-axis magnetic fields, the magnetoresistance response of the micron-roll material does not change significantly, while the change in the thin film material is more pronounced.

[0032] Figure 5 This is a method for fabricating an isotropic magnetically sensitive material and a miniature magnetic sensor, comprising the following steps: A sacrificial layer capable of being wet-etched is grown on a second substrate; A strain layer is grown above the sacrificial layer; A magnetically sensitive material layer with magnetoresistance properties is grown above the strained layer; Metal electrodes are fabricated on top of the magnetically sensitive material layer using photolithography or a mask; The sacrificial layer / strain layer / magnetically sensitive material layer is etched into strips using methods such as photolithography or laser engraving. By manipulating a capillary tube, a solution capable of etching the sacrificial layer is dropped onto one side of the etched strip, causing the magnetically sensitive material layer to slowly curl up to form a micron-sized magnetically sensitive material. In addition, a first substrate is prepared, and a bottom electrode and a fixed thin film resistor are deposited on the surface of the first substrate. The micron-sized magnetically sensitive material is transferred to a first substrate, and the electrode ends are in contact with the bottom electrode to form the aforementioned flexible micro magnetic sensor.

[0033] Among them, the first substrate, sacrificial layer, strain layer and magnetic sensitive material layer all have similar unit cell parameters. The unit cell parameters of the strain layer are slightly smaller or slightly larger than those of the substrate material layer. After the sacrificial layer is etched, it causes the magnetic sensitive thin film layer to roll inward and keep the two electrodes facing outward, so that it can contact the bottom electrode in the first substrate.

[0034] Furthermore, after the sacrificial layer is etched and the first substrate is ultrasonically cleaned, the first substrate continues to be used for thin film growth, thereby saving costs.

[0035] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications 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 method for fabricating an isotropic magnetically sensitive material and a micro magnetic sensor, characterized in that, Includes the following steps: A sacrificial layer capable of being wet-etched is grown on a second substrate; A strain layer is grown above the sacrificial layer; A magnetically sensitive material layer with magnetoresistance properties is grown above the strained layer; Metal electrodes are fabricated on top of the magnetically sensitive material layer using photolithography or a mask; The sacrificial layer / strain layer / magnetically sensitive material layer is etched into a strip shape using photolithography or laser engraving methods, with metal electrodes located on both sides of the short side of the strip. The solution capable of etching the sacrificial layer is dripped into one side of the short side of the etched strip through the capillary tube, and the magnetic sensitive material layer slowly rolls up to form a micron-sized isotropic magnetic sensitive material. In addition, a first substrate is prepared, and a bottom electrode and a fixed thin film resistor as a fixed resistor are deposited on the surface of the first substrate. The fixed thin film resistor is located above the bottom electrode. A micro-roll of isotropic magnetic sensitive material is transferred to a first substrate, and the metal electrodes at both ends are in contact with the bottom electrode to obtain a micro magnetic sensor.

2. The method for preparing the isotropic magnetically sensitive material and the micro magnetic sensor according to claim 1, characterized in that, The first substrate, sacrificial layer, strain layer, and magnetically sensitive material layer all have similar cell parameters. The cell parameters of the strain layer are slightly smaller or slightly larger than those of the substrate material layer. After the sacrificial layer is etched, it causes the magnetically sensitive thin film layer to roll inward and keep the two electrodes facing outward, so that it can contact the bottom electrode in the first substrate.

3. The method for preparing the isotropic magnetically sensitive material and the micro magnetic sensor according to claim 1, characterized in that, After the sacrificial layer is etched and the first substrate is ultrasonically cleaned, the first substrate continues to be used for thin film growth.

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