A surface stripe pattern magnetic core micro fluxgate sensor and its preparation method

Abstract

The present invention discloses a surface stripe grid pattern magnetic core micro fluxgate sensor, comprising a substrate and a surface stripe grid pattern magnetic core; an excitation coil and an induction coil are arranged on the substrate; the surface stripe grid pattern magnetic core is arranged inside the excitation coil and the induction coil; the surface stripe grid pattern magnetic core and the excitation coil as well as the surface stripe grid pattern magnetic core and the induction coil are electrically isolated by an insulating isolation layer; the surface stripe grid pattern magnetic core comprises a smooth surface magnetic film and a plurality of stripe grid pattern magnetic films; the smooth surface magnetic film is a rectangular structure or a U-shaped runway structure; the stripe grid pattern magnetic film is a rectangular structure. The present invention weakens the demagnetization effect of the smooth surface magnetic film in the length direction, and can significantly enhance the effective magnetic permeability of the surface stripe grid pattern magnetic core in the length direction, thereby realizing high-sensitivity magnetic field detection.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic sensors, and in particular to a surface stripe-grid pattern magnetic core micro fluxgate sensor and a preparation method thereof. Background Art

[0002] Magnetic sensors are sensors that use magnetic sensitive elements to sense physical quantities related to magnetic signals and convert them into electrical signals. They are widely used in target detection, flow monitoring, navigation and positioning, and biomedicine. They have promoted the rapid development of atmospheric science, environmental monitoring, resource mining, underwater navigation, and disease diagnosis.

[0003] As we enter the era of intelligent perception, emerging industries such as artificial intelligence, new energy vehicles, robots, and smart health testing are increasingly demanding high-sensitivity miniature magnetic field sensors to achieve weak magnetic field detection.

[0004] At present, Hall sensors have low sensitivity; superconducting quantum interference effect sensors are large in size, cumbersome to operate, and expensive; anisotropic magnetoresistive sensors have problems such as offset and hysteresis. In contrast, fluxgate sensors utilize the physical properties of nonlinear magnetization of magnetic materials, and achieve high-sensitivity magnetic field detection under the dual effects of periodic magnetic saturation of the core and signal modulation. In addition, with the rapid development of micro-electromechanical systems (MEMS), it is possible to prepare high-resolution micro magnetic field sensors.

[0005] Prior art, publication number: CN 102981131 B discloses a low-noise miniature planar fluxgate sensor based on dual excitation of main and auxiliary coils, wherein four groups of main excitation coils are symmetrically wound at both ends of two parallel long axes of the magnetic core, and three groups of detection coils and two groups of auxiliary excitation coils are symmetrically wound in the middle of the long axes, which can effectively improve the excitation efficiency of the fluxgate sensor and reduce the output signal noise. However, the disclosed microsensor has multiple groups of coils, the structure is very complex, and the success rate of micromachining is very low. Publication number: CN 106772143 B discloses a miniature fluxgate sensor, which has one group of excitation coils and one group of induction coils, and adopts a three-dimensional solenoid structure, which greatly reduces the process steps and improves the success rate. However, the magnetic core adopts a planar rectangular structure, and the inevitable shape demagnetization causes the effective magnetic permeability of the magnetic core to decrease, which greatly weakens the sensitivity of the sensor. Therefore, a method is needed to compensate for shape demagnetization to improve the sensitivity of the sensor. Summary of the invention

[0006] 1. Technical problems to be solved:

[0007] In view of the above technical problems, the present invention provides a surface stripe pattern magnetic core micro fluxgate sensor and a preparation method thereof.

[0008] 2. Technical solution:

[0009] A surface stripe grid pattern magnetic core micro fluxgate sensor, comprising a substrate and a surface stripe grid pattern magnetic core; an excitation coil and an induction coil are arranged on the substrate; the surface stripe grid pattern magnetic core is arranged inside the excitation coil and the induction coil; the surface stripe grid pattern magnetic core and the induction coil, as well as the surface stripe grid pattern magnetic core and the excitation coil are electrically isolated by an insulating isolation layer;

[0010] The surface stripe-grid pattern magnetic core comprises a smooth surface magnetic film and a plurality of stripe-grid pattern magnetic films; the smooth surface magnetic film is a rectangular structure or a U-shaped racetrack structure; the stripe-grid pattern magnetic film is a rectangular structure;

[0011] When the surface smooth magnetic film is a rectangular structure, the excitation coil and the induction coil are separately arranged or alternately arranged outside the surface stripe grid pattern magnetic core with a certain distance; a plurality of stripe grid pattern magnetic films are arranged on the top of the surface smooth magnetic film at equal intervals; the long side of the stripe grid pattern magnetic film is perpendicular to the long side of the surface smooth magnetic film; the aspect ratio of a single stripe grid pattern magnetic film is not less than ten; the length of the stripe grid pattern magnetic film is the same as the width of the surface smooth magnetic film;

[0012] When the smooth surface magnetic film has a U-shaped runway structure, the smooth surface magnetic film has two parallel rectangular runways; the excitation coil and the induction coil are respectively arranged or alternately arranged on the outside of the two runways, and a plurality of stripe-grid pattern magnetic films are evenly spaced on the two runways; the long side of the stripe-grid pattern magnetic film is perpendicular to the long side of the runway; the aspect ratio of a single stripe-grid pattern magnetic film is not less than ten; the length of the stripe-grid pattern magnetic film is the same as the width of the runway.

[0013] Furthermore, the excitation coil and the induction coil are both three-dimensional solenoid structures, the bottom wire and the top wire of the three-dimensional solenoid structure are connected by connecting wires, and electrodes are led out at both ends of the excitation coil and the induction coil; the electrodes of the excitation coil and the induction coil are both arranged on the bottom wire; one of the electrodes of the excitation coil is the excitation signal input end, and the other electrode is the excitation signal output end; the potential difference between the two electrodes of the induction coil is the output signal.

[0014] Furthermore, the substrate is made of insulating material, including a silicon substrate, a quartz glass substrate and an alumina substrate.

[0015] Furthermore, the excitation coil and the induction coil are made of copper.

[0016] Furthermore, the insulating isolation layer is made of silicon nitride or polyimide.

[0017] The following provides a method for preparing a surface stripe pattern magnetic core micro fluxgate sensor; the method comprises the following steps:

[0018] Step S1: preparing a semi-finished sensor in the shape of a micro fluxgate sensor with a surface stripe pattern magnetic core by a micromachining process;

[0019] Step S2: annealing the semi-finished sensor in a high temperature vacuum magnetic field, wherein the direction of the magnetic field is perpendicular to the long side of the smooth magnetic film on the surface of the semi-finished sensor, so as to induce the easy magnetization axis of the film to be parallel to the long side of the smooth magnetic film on the surface.

[0020] Specifically, the step S1 includes:

[0021] Step S11: preparing a bottom conductor with an electrode on a substrate by a first photolithography process; including pre-treating the substrate, depositing a first insulating isolation layer on the substrate, spin-coating a first photoresist on the first insulating isolation layer, drying, exposing through a first photomask having the shape of the bottom conductor, etching and removing the first insulating isolation layer in the area where the bottom conductor is located after development, and depositing a first conductive layer on the substrate in the area where the bottom conductor is located, wherein the first conductive layer is the bottom conductor;

[0022] Step S12: preparing a smooth magnetic film on the bottom conductor by a second photolithography process; stripping off the first photoresist; depositing a second insulating isolation layer on the first insulating isolation layer, spin-coating the second photoresist, and drying; exposing through a second photomask having the shape of the smooth magnetic film, etching and removing a portion of the second insulating isolation layer in the area where the smooth magnetic film is located after development, and depositing a first magnetic layer on the second insulating isolation layer in the area where the smooth magnetic film is located, wherein the first magnetic layer is the smooth magnetic film;

[0023] Step S13: preparing a stripe-grid pattern magnetic film on a smooth magnetic film through a third photolithography process; depositing a third insulating isolation layer on the surface of the smooth magnetic film so that the second insulating isolation layer and the upper surface of the third insulating isolation layer are flush; stripping and removing the second photoresist; spin-coating the third photoresist on the third insulating isolation layer and drying; exposing through a third photolithography plate having a plurality of stripe-grid pattern magnetic film shapes, and etching and removing the third insulating isolation layer in the area where the stripe-grid pattern magnetic film is located after development; depositing a second magnetic layer on the first magnetic layer in the area where the stripe-grid pattern magnetic film is located, wherein the second magnetic layer is the stripe-grid pattern magnetic film;

[0024] Step S14: preparing a connecting wire on the bottom conductor through a fourth photolithography process; depositing a fourth insulating isolation layer on the surface of the stripe pattern magnetic film so that the third insulating isolation layer and the upper surface of the fourth insulating isolation layer are flush; stripping off the third photoresist; and spin coating the fourth photoresist and drying; exposing through a fourth photoresist plate having a connecting wire shape, and etching and removing the second insulating isolation layer in the area where the connecting wire is located after development; depositing a second conductive layer on the bottom conductor in the area where the connecting wire is located, wherein the second conductive layer is the connecting wire;

[0025] Step S15: preparing a top-layer wire on the connecting wire by a fifth photolithography process; depositing a fifth insulating isolation layer on the surface of the second conductive layer so that the fourth insulating isolation layer and the upper surface of the fifth insulating isolation layer are flush; stripping and removing the fourth photoresist; spin-coating a fifth photoresist on the fifth insulating isolation layer and drying; exposing through a fifth photoresist plate having the shape of the top-layer wire, and etching and removing the fifth insulating isolation layer in the area where the top-layer wire is located after development; depositing a third conductive layer on the connecting wire in the area where the top-layer wire is located, wherein the third conductive layer is the top-layer wire;

[0026] Step S16: exposing the electrodes on the bottom conductor through the sixth photolithography process; depositing a sixth insulating isolation layer on the surface of the third conductive layer so that the upper surfaces of the fifth insulating isolation layer and the sixth insulating isolation layer are flush; stripping off the fifth photoresist; spin-coating a sixth photoresist on the sixth insulating isolation layer and drying it; exposing it through a sixth photolithography plate having an electrode shape, and after development, etching away the second insulating isolation layer and the sixth insulating isolation layer in the area where the electrode is located; stripping off the sixth photoresist to obtain a semi-finished sensor.

[0027] Furthermore, the substrate pretreatment includes sequentially cleaning and decontamination by ultrasonic cleaning in acetone, anhydrous ethanol and deionized water, drying by nitrogen and drying in an oven;

[0028] Further, the first photoresist, the second photoresist, the third photoresist, the fourth photoresist, the fifth photoresist and the sixth photoresist are all removed by acetone stripping;

[0029] Furthermore, the first magnetic layer, the second magnetic layer, the first conductive layer, the second conductive layer, the third conductive layer, the first insulating isolation layer, the second insulating isolation layer, the third insulating isolation layer, the fourth insulating isolation layer, the fifth insulating isolation layer and the sixth insulating isolation layer are all formed by chemical deposition or physical deposition.

[0030] Furthermore, step S2 is based on an annealing device, which includes a tray; two fixing plates are symmetrically fixed on the tray by screws; a high-temperature magnet is installed on the fixing plate; the sensor semi-finished product obtained in step S1 is fixed on the tray between the two high-temperature magnets using high-temperature tape; the surface of the sensor semi-finished product is smooth and the long side of the magnetic film is perpendicular to the long side of the high-temperature magnet; the annealing device and the sensor semi-finished product are placed as a whole in a high-temperature annealing furnace for vacuum annealing, and cooled to room temperature under a vacuum environment.

[0031] 3. Beneficial effects:

[0032] The present invention uses a surface stripe pattern magnetic film as the magnetic core of the fluxgate sensor. Processing a stripe pattern on the surface of a smooth magnetic film (a stripe pattern magnetic film) can significantly compensate for shape demagnetization and improve the effective magnetic permeability of the magnetic core and the sensitivity of the sensor. Compared with a smooth magnetic core of the same thickness, the effective magnetic permeability of the surface stripe pattern magnetic film is significantly enhanced; the physical explanation is as follows:

[0033] (i) When the thickness of a smooth surface magnetic film is much smaller than its length and width, the demagnetization factor along the length direction is approximately inversely proportional to its thickness. In a surface stripe pattern magnetic film, the film thickness of the part without the stripe pattern is reduced, and accordingly, in this area, the demagnetization factor and demagnetization field along the length direction are reduced.

[0034] (ii) When the surface stripe-grid pattern magnetic film with the stripe-grid pattern magnetic film is magnetized by an external magnetic field along the length direction, there are surface magnetic charges on both the end faces of the short sides of the surface stripe-grid pattern magnetic film and the end faces of the long sides of the stripe-grid pattern magnetic film. The magnetic polarization field is emitted from the end face of the positive magnetic charge and terminates at the end face of the negative magnetic charge. Therefore, in the area where there is no stripe-grid pattern magnetic film in the surface stripe-grid pattern magnetic film, the direction of the magnetic polarization field is the same as the direction of the external magnetic field. In addition, since the aspect ratio of a single stripe-grid pattern magnetic film is not less than ten, the interval between adjacent stripe-grid pattern magnetic films is less than the length of the surface stripe-grid pattern magnetic film, and the magnetic polarization field generated by the end face of the long side of the stripe-grid pattern magnetic film is greater than the demagnetization field generated by the end face of the short side of the surface stripe-grid pattern magnetic film, the magnetic polarization field can not only offset the demagnetization field, but also significantly enhance the effective field in the area where there is no stripe-grid pattern magnetic film. Processing a stripe pattern on the surface of a smooth magnetic film can not only compensate for the shape demagnetization field, but also use the magnetic polarization field to further enhance the effective field of the surface stripe pattern magnetic film, which will significantly improve the effective magnetic permeability of the surface stripe pattern magnetic film.

[0035] Therefore, the present invention weakens the demagnetization effect of the surface stripe grid pattern magnetic core in the length direction, and can significantly enhance the effective magnetic permeability of the surface stripe grid pattern magnetic core in the length direction, thereby achieving high-sensitivity magnetic field detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the first structure of a micro fluxgate sensor with a surface stripe pattern magnetic core according to Example 1 of the present invention;

[0037] Figure 2 This is a schematic structural diagram of a surface stripe pattern magnetic core according to Embodiment 1 of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of the induction coil or the excitation coil of Embodiment 1 of the present invention;

[0039] Figure 4 This is a schematic structural diagram of the first semi-finished product formed by step S11 in Example 2 of the present invention;

[0040] Figure 5 This is a schematic structural diagram of a second semi-finished product formed by step S12 in Example 2 of the present invention;

[0041] Figure 6 It is a schematic structural diagram of a third semi-finished product formed by processing in step S13 in Example 2 of the present invention;

[0042] Figure 7 is a schematic structural diagram of a fourth semi-finished product formed by processing in step S14 in Example 2 of the present invention;

[0043] Figure 8 The annealing device of step S2 of embodiment 2 of the present invention;

[0044] Fig. 9 This is a schematic diagram of a second structure of a micro fluxgate sensor with a surface stripe pattern magnetic core according to Embodiment 1 of the present invention;

[0045] Fig.10 This is a third structural schematic diagram of the surface stripe grid pattern magnetic core micro fluxgate sensor according to Example 1 of the present invention;

[0046] Fig.11 This is a fourth structural schematic diagram of the surface stripe grid pattern magnetic core micro fluxgate sensor according to Example 1 of the present invention;

[0047] Fig.12 This is a graph showing the effective magnetic permeability data of a smooth surface magnetic core and a surface stripe pattern magnetic core according to Example 3 of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be described in detail below with reference to the accompanying drawings.

[0049] Example 1

[0050] like Figure 1-3 and Figure 9-11As shown, a surface stripe grid pattern magnetic core micro fluxgate sensor comprises a substrate 1 and a surface stripe grid pattern magnetic core 3; an excitation coil 4 and an induction coil 5 are arranged on the substrate; the surface stripe grid pattern magnetic core 3 is arranged inside the induction coil 5 and the excitation coil 4; the surface stripe grid pattern magnetic core 3 and the excitation coil 4 as well as the surface stripe grid pattern magnetic core 3 and the induction coil 5 are electrically isolated by an insulating isolation layer 2;

[0051] The surface stripe-grid pattern magnetic core 3 includes a surface smooth magnetic film 3-1 and a plurality of stripe-grid pattern magnetic films 3-2; the surface smooth magnetic film 3-1 is a rectangular structure or a U-shaped racetrack structure; the stripe-grid pattern magnetic film 3-2 is a rectangular structure;

[0052] When the smooth surface magnetic film 3-1 is a rectangular structure, the excitation coil 4 and the induction coil 5 are separately arranged with a certain distance ( Figure 1 ) or alternately ( Fig. 9 ) on the outside of the surface stripe-grid pattern magnetic core 3; multiple stripe-grid pattern magnetic films 3-2 are arranged at equal intervals on the top of the smooth surface magnetic film 3-1; the long side of the stripe-grid pattern magnetic film 3-2 is perpendicular to the long side of the smooth surface magnetic film 3-1; the aspect ratio of a single stripe-grid pattern magnetic film 3-2 is not less than ten; the length of the stripe-grid pattern magnetic film 3-2 is the same as the width of the smooth surface magnetic film 3-1;

[0053] When the smooth surface magnetic film 3-1 is a U-shaped track structure, the smooth surface magnetic film 3-1 has two parallel rectangular tracks; the excitation coil 4 and the induction coil 5 are respectively arranged ( Fig.10 ) or alternately ( Fig.11 ) On the outside of the two runways, a plurality of stripe-grid pattern magnetic films 3-2 are evenly spaced and arranged on the two runways; the long sides of the stripe-grid pattern magnetic films 3-2 are perpendicular to the long sides of the runways; the aspect ratio of a single stripe-grid pattern magnetic film 3-2 is not less than ten; the length of the stripe-grid pattern magnetic film 3-2 is the same as the width of the runway.

[0054] Both the excitation coil 4 and the induction coil 5 are three-dimensional solenoid structures. The bottom conductor and the top conductor of the three-dimensional solenoid structure are connected by connecting conductors, and electrodes are led out at both ends of the excitation coil 4 and the induction coil 5; the electrodes of the excitation coil 4 and the induction coil 5 are both arranged on the bottom conductor; one of the electrodes of the excitation coil is the input end of the excitation signal, and the other electrode is the output end of the excitation signal; the potential difference between the two electrodes of the induction coil 5 is the output signal.

[0055] The substrate is a substrate made of insulating material, including a silicon substrate, a quartz glass substrate and an alumina substrate. The substrate is a rigid material or a flexible material.

[0056] The materials of the excitation coil and the induction coil are both copper.

[0057] The insulating isolation layer is made of silicon nitride or polyimide.

[0058] Example 2

[0059] by Figure 1 Taking the surface stripe pattern magnetic core micro fluxgate sensor shown in the figure as an example, a preparation method of a surface stripe pattern magnetic core micro fluxgate sensor is provided, comprising:

[0060] S11: Preparation of bottom conductor with electrodes:

[0061] The silicon substrate was selected as the base material, and the silicon substrate was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 5 minutes each to remove the dirt on the surface of the silicon substrate. Then, dry nitrogen was used to blow dry the liquid on the surface of the silicon substrate, and the silicon substrate was placed in a vacuum drying oven and baked for 2 hours.

[0062] A first insulating isolation layer with a thickness of 400 nm is deposited on the silicon substrate, and the first insulating isolation layer is silicon nitride (Si3N4).

[0063] The first photoresist was spin-coated on the first insulating isolation layer at a rotation speed of 1500 r / min using a spin coater, the thickness of the first photoresist was 6 μm, and then baked on an electric heating plate at 90° C. for 120 seconds.

[0064] The first photoresist having the bottom conductor pattern was exposed using a photolithography machine, developed in a developer for 45 seconds, and then rinsed with deionized water for 35 seconds to obtain the bottom conductor pattern.

[0065] The first insulating isolation layer is etched 400 nm using a reactive ion etching system to prepare for the preparation of the bottom layer wires.

[0066] The first conductive layer of 400 nm is deposited by magnetron sputtering, and the first conductive layer is the bottom conductor. The first semi-finished product structure formed by step S11 is as follows Figure 4 shown.

[0067] S12: Preparation of smooth magnetic films

[0068] A second insulating isolation layer with a thickness of 2000 nm is deposited on the first conductive layer; the second insulating isolation layer is silicon nitride.

[0069] The first photoresist was stripped using acetone and ultrasonically cleaned with deionized water for 15 seconds;

[0070] Spin coating the second photoresist on the second insulating isolation layer at a speed of 1500 r / min using a spin coating machine, the thickness of the second photoresist is 6 μm, and then baking on an electric heating plate at 90° C. for 120 seconds;

[0071] A second photoresist having a rectangular pattern (consistent with the shape of the smooth magnetic film) is exposed using a photolithography machine, developed in a developer for 45 seconds, and then rinsed with deionized water for 35 seconds to obtain a rectangular pattern;

[0072] The second insulating isolation layer was etched 1500 nm using a reactive ion etching system to prepare for the preparation of a smooth magnetic film.

[0073] The first magnetic layer of 600 nm is deposited by magnetron sputtering, and the first magnetic layer is a magnetic film with a smooth surface. The second semi-finished product structure formed by step S12 is as follows Figure 5 shown.

[0074] S13: Preparation of stripe-grid pattern magnetic film:

[0075] A third insulating isolation layer with a thickness of 900 nm is deposited on the first magnetic layer; the third insulating isolation layer is silicon nitride.

[0076] The second photoresist was stripped using acetone and ultrasonically cleaned with deionized water for 15 seconds;

[0077] Spin coating the third photoresist on the third insulating isolation layer at a rotation speed of 1500 r / min using a spin coating machine, the thickness of the third photoresist is 6 μm, and then baking on an electric heating plate at 90° C. for 120 seconds;

[0078] A third photoresist having a plurality of stripe shapes is exposed using a photolithography machine, and developed in a developer for 45 seconds, and then rinsed with deionized water for 35 seconds to obtain a pattern having the same shape as the stripe pattern magnetic film, wherein the width of a single stripe is 10 μm;

[0079] The third insulating isolation layer is etched by 900 nm using a reactive ion etching system to prepare for the preparation of a stripe-gate pattern magnetic film.

[0080] The second magnetic layer of 600 nm is deposited by magnetron sputtering, and the second magnetic layer is a stripe-grid pattern magnetic film. The third semi-finished product structure formed by step S13 is as follows: Figure 6 shown.

[0081] S14: Preparation of connecting wires:

[0082] A fourth insulating isolation layer with a thickness of 300 nm is deposited on the second magnetic layer; the fourth insulating isolation layer is silicon nitride.

[0083] The third photoresist was stripped using acetone and ultrasonically cleaned with deionized water for 15 seconds;

[0084] Spin coating the fourth photoresist on the second insulating isolation layer and the fourth insulating isolation layer with a spin coating machine at a rotation speed of 1500 r / min, the thickness of the fourth photoresist is 6 μm, and then baking on an electric heating plate at 90° C. for 120 seconds;

[0085] Using a photolithography machine to expose a fourth photoresist having a plurality of connection wire shapes, and developing in a developer for 45 seconds, and then rinsing with deionized water for 35 seconds, to obtain a pattern of a plurality of connection wire shapes;

[0086] The second insulating isolation layer is etched by 2000 nm using a reactive ion etching system to prepare for the preparation of multiple connecting wires.

[0087] The second conductive layer of 2000 nm is deposited by magnetron sputtering, and the second conductive layer is the connecting wire. The fourth semi-finished product structure formed by step S14 is as follows Figure 7 shown.

[0088] S15: Prepare the top conductor:

[0089] A fifth insulating isolation layer with a thickness of 400 nm is deposited on the second conductive layer; the fifth insulating isolation layer is silicon nitride.

[0090] The fourth photoresist was stripped using acetone and ultrasonically cleaned with deionized water for 15 seconds;

[0091] Spin-coat the fifth photoresist on the fifth insulating isolation layer at a rotation speed of 1500 r / min using a spinner, the thickness of the fifth photoresist is 6 μm, and then bake on an electric heating plate at 90° C. for 120 seconds;

[0092] Using a photolithography machine to expose the fifth photoresist having the top conductor shape, and developing in a developer for 45 seconds, and then rinsing with deionized water for 35 seconds to obtain a pattern of the top conductor;

[0093] The fifth insulating isolation layer is etched 400 nm using a reactive ion etching system to prepare for the preparation of top-layer wires.

[0094] The third conductive layer of 300 nm is deposited by magnetron sputtering, and the third conductive layer is the top conductive line. The fourth semi-finished product structure formed by step S14 is as follows: Figure 1 shown.

[0095] S16: Preparation of electrodes:

[0096] A sixth insulating isolation layer with a thickness of 100 nm is deposited on the third conductive layer; the sixth insulating isolation layer is silicon nitride.

[0097] The fifth photoresist was stripped using acetone and ultrasonically cleaned with deionized water for 15 seconds;

[0098] Spin coating the sixth photoresist on the sixth insulating isolation layer with a spin coating machine at a rotation speed of 1500 r / min, the thickness of the sixth photoresist is 6 μm, and then baking on an electric heating plate at 90° C. for 120 seconds;

[0099] Using a photolithography machine to expose the sixth photoresist plate having the electrode shape, and developing it in a developer for 45 seconds, and then rinsing it with deionized water for 35 seconds to obtain an electrode pattern;

[0100] The sixth insulating isolation layer and the second insulating isolation layer were etched by 2400 nm using a reactive ion etching system to expose the first conductive layer, the sixth photoresist was removed by acetone, and ultrasonic cleaning was performed with deionized water for 15 seconds to obtain a semi-finished sensor.

[0101] S2: The semi-finished sensor is annealed in a high-temperature vacuum magnetic field, and the direction of the magnetic field is perpendicular to the length direction of the smooth magnetic film.

[0102] High temperature vacuum magnetic field annealing is based on annealing equipment; such as Figure 8 As shown, the annealing device includes a tray 6; two fixing plates 8 are symmetrically fixed on the tray 6 by screws 7; a high-temperature magnet 9 is installed on the fixing plate 8; the semi-finished sensor obtained in step S16 is fixed on the tray between the two high-temperature magnets 9 by using a high-temperature tape; the length direction of the smooth magnetic film is perpendicular to the length direction of the high-temperature magnet 9; the annealing device and the semi-finished sensor are placed in a high-temperature annealing furnace as a whole, vacuum annealing is performed, and then cooled to room temperature in a vacuum environment.

[0103] After annealing, a wire bonding machine is used to connect the gold wires to the electrodes of the sensor and the pins of the circuit board to complete the final packaging.

[0104] Example 3

[0105] Fig.12 The effective permeability data of the existing smooth surface magnetic core and the surface stripe pattern magnetic core of the present invention are shown in the figure. The length, width and thickness of the smooth surface magnetic core are 6 mm, 2 mm and 20 mm respectively. μ m, and the total length, width, and thickness of the surface stripe pattern core are also 6 mm, 2 mm, and 20 mm, respectively. μ m, and the width of the magnetic film with a grating pattern is 40 μ m, thickness is 10 μ m, and the spacing between adjacent stripe-patterned magnetic films is 0.46 mm. The experimental data show that the maximum effective magnetic permeability of the surface stripe-patterned magnetic core is increased by 99.84% compared with the smooth surface magnetic core of the same thickness, which is caused by the weakening of the demagnetization effect along the length direction of the surface stripe-patterned magnetic core. This proves that machining a stripe-patterned magnetic core on the surface of a smooth surface can significantly increase the effective magnetic permeability of the magnetic core, thereby improving the sensitivity of the sensor and achieving high-sensitivity magnetic field detection.

[0106] Although the present invention has been disclosed as above in terms of preferred embodiments, they are not intended to limit the present invention. Anyone skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims of this application.

Claims

1. A surface stripe pattern magnetic core micro fluxgate sensor, characterized in that: It comprises a substrate and a surface stripe grid pattern magnetic core; an excitation coil and an induction coil are arranged on the substrate; the surface stripe grid pattern magnetic core is arranged inside the excitation coil and the induction coil; the surface stripe grid pattern magnetic core and the excitation coil, as well as the surface stripe grid pattern magnetic core and the induction coil are electrically isolated by an insulating isolation layer; The surface stripe-grid pattern magnetic core comprises a smooth surface magnetic film and a plurality of stripe-grid pattern magnetic films; the smooth surface magnetic film is a rectangular structure or a U-shaped racetrack structure; the stripe-grid pattern magnetic film is a rectangular structure; When the surface smooth magnetic film is a rectangular structure, the excitation coil and the induction coil are separately arranged or alternately arranged outside the surface stripe grid pattern magnetic core with a certain distance; a plurality of stripe grid pattern magnetic films are arranged on the top of the surface smooth magnetic film at equal intervals; the long side of the stripe grid pattern magnetic film is perpendicular to the long side of the surface smooth magnetic film; the aspect ratio of a single stripe grid pattern magnetic film is not less than ten; the length of the stripe grid pattern magnetic film is the same as the width of the surface smooth magnetic film; When the smooth surface magnetic film has a U-shaped runway structure, the smooth surface magnetic film has two parallel rectangular runways; the excitation coil and the induction coil are respectively arranged or alternately arranged on the outside of the two runways, and a plurality of stripe-grid pattern magnetic films are evenly spaced on the two runways; the long side of the stripe-grid pattern magnetic film is perpendicular to the long side of the runway; the aspect ratio of a single stripe-grid pattern magnetic film is not less than ten; the length of the stripe-grid pattern magnetic film is the same as the width of the runway.

2. A surface stripe pattern magnetic core micro fluxgate sensor according to claim 1, characterized in that: The excitation coil and the induction coil are both three-dimensional solenoid structures. The bottom wire and the top wire of the three-dimensional solenoid structure are connected by connecting wires, and electrodes are led out at both ends of the excitation coil and the induction coil; the electrodes of the excitation coil and the induction coil are both arranged on the bottom wire; one of the electrodes of the excitation coil is the excitation signal input end, and the other electrode is the excitation signal output end; the potential difference between the two electrodes of the induction coil is the output signal.

3. A surface stripe pattern magnetic core micro fluxgate sensor according to claim 1, characterized in that: The substrate is made of insulating material, including a silicon substrate, a quartz glass substrate and an alumina substrate.

4. A surface stripe pattern magnetic core micro fluxgate sensor according to claim 2, characterized in that: The excitation coil and the induction coil are made of copper.

5. A surface stripe pattern magnetic core micro fluxgate sensor according to claim 3 or 4, characterized in that: The insulating isolation layer is made of silicon nitride or polyimide.

6. A method for preparing a surface stripe pattern magnetic core micro fluxgate sensor as claimed in claim 1, characterized in that: The following steps are involved: Step S1: preparing a semi-finished sensor in the shape of a micro fluxgate sensor with a surface stripe pattern magnetic core by a micromachining process; Step S2: annealing the semi-finished sensor in a high temperature vacuum magnetic field, wherein the direction of the magnetic field is perpendicular to the long side of the smooth magnetic film on the surface of the semi-finished sensor, so as to induce the easy magnetization axis of the film to be parallel to the long side of the smooth magnetic film on the surface.

7. The method for preparing a surface stripe pattern magnetic core micro fluxgate sensor according to claim 6, characterized in that: The step S1 comprises: Step S11: preparing a bottom conductor with an electrode on a substrate by a first photolithography process; including pre-treating the substrate, depositing a first insulating isolation layer on the substrate, spin-coating a first photoresist on the first insulating isolation layer, drying, exposing through a first photomask having the shape of the bottom conductor, etching and removing the first insulating isolation layer in the area where the bottom conductor is located after development, and depositing a first conductive layer on the substrate in the area where the bottom conductor is located, wherein the first conductive layer is the bottom conductor; Step S12: preparing a smooth magnetic film on the bottom conductor by a second photolithography process; stripping off the first photoresist; depositing a second insulating isolation layer on the first insulating isolation layer, spin-coating the second photoresist, and drying; exposing through a second photomask having the shape of the smooth magnetic film, etching and removing a portion of the second insulating isolation layer in the area where the smooth magnetic film is located after development, and depositing a first magnetic layer on the second insulating isolation layer in the area where the smooth magnetic film is located, wherein the first magnetic layer is the smooth magnetic film; Step S13: preparing a stripe-grid pattern magnetic film on a smooth magnetic film through a third photolithography process; depositing a third insulating isolation layer on the surface of the smooth magnetic film so that the second insulating isolation layer and the upper surface of the third insulating isolation layer are flush; stripping and removing the second photoresist; spin-coating the third photoresist on the third insulating isolation layer and drying; exposing through a third photolithography plate having a plurality of stripe-grid pattern magnetic film shapes, and etching and removing the third insulating isolation layer in the area where the stripe-grid pattern magnetic film is located after development; depositing a second magnetic layer on the first magnetic layer in the area where the stripe-grid pattern magnetic film is located, wherein the second magnetic layer is the stripe-grid pattern magnetic film; Step S14: preparing a connecting wire on the bottom conductor through a fourth photolithography process; depositing a fourth insulating isolation layer on the surface of the stripe pattern magnetic film so that the third insulating isolation layer and the upper surface of the fourth insulating isolation layer are flush; stripping off the third photoresist; and spin coating the fourth photoresist and drying; exposing through a fourth photoresist plate having a connecting wire shape, and etching and removing the second insulating isolation layer in the area where the connecting wire is located after development; depositing a second conductive layer on the bottom conductor in the area where the connecting wire is located, wherein the second conductive layer is the connecting wire; Step S15: preparing a top-layer wire on the connecting wire by a fifth photolithography process; depositing a fifth insulating isolation layer on the surface of the second conductive layer so that the fourth insulating isolation layer and the upper surface of the fifth insulating isolation layer are flush; stripping and removing the fourth photoresist; spin-coating a fifth photoresist on the fifth insulating isolation layer and drying; exposing through a fifth photoresist plate having the shape of the top-layer wire, and etching and removing the fifth insulating isolation layer in the area where the top-layer wire is located after development; depositing a third conductive layer on the connecting wire in the area where the top-layer wire is located, wherein the third conductive layer is the top-layer wire; Step S16: exposing the electrodes on the bottom conductor through the sixth photolithography process; depositing a sixth insulating isolation layer on the surface of the third conductive layer so that the upper surfaces of the fifth insulating isolation layer and the sixth insulating isolation layer are flush; stripping off the fifth photoresist; spin-coating a sixth photoresist on the sixth insulating isolation layer and drying it; exposing it through a sixth photolithography plate having an electrode shape, and after development, etching away the second insulating isolation layer and the sixth insulating isolation layer in the area where the electrode is located; stripping off the sixth photoresist to obtain a semi-finished sensor.

8. The method for preparing a surface stripe pattern magnetic core micro fluxgate sensor according to claim 7, characterized in that: At least one of the following technical features: a1: The pretreatment of the substrate includes sequentially cleaning and decontamination by ultrasonic cleaning with acetone, anhydrous ethanol and deionized water, blowing dry with nitrogen and drying in an oven; a2: the first photoresist, the second photoresist, the third photoresist, the fourth photoresist, the fifth photoresist and the sixth photoresist are all removed by stripping with acetone; a3: The first magnetic layer, the second magnetic layer, the first conductive layer, the second conductive layer, the third conductive layer, the first insulating isolation layer, the second insulating isolation layer, the third insulating isolation layer, the fourth insulating isolation layer, the fifth insulating isolation layer and the sixth insulating isolation layer are all formed by chemical deposition or physical deposition.

9. The method for preparing a surface stripe pattern magnetic core micro fluxgate sensor according to claim 7, characterized in that: The step S2 is based on an annealing device, which includes a tray; two fixing plates are symmetrically fixed on the tray by screws; a high-temperature magnet is installed on the fixing plate; the semi-finished sensor obtained in step S1 is fixed on the tray between the two high-temperature magnets by using a high-temperature tape; the surface of the semi-finished sensor is smooth and the long side of the magnetic film is perpendicular to the long side of the high-temperature magnet; the annealing device and the semi-finished sensor are placed in a high-temperature annealing furnace as a whole, vacuum annealing is performed, and the semi-finished sensor is cooled to room temperature under a vacuum environment.

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