MEMS fluxgate sensor with double-layer induction coil and manufacturing method of MEMS fluxgate sensor

Abstract

The invention relates to an MEMS fluxgate sensor with double-layer induction coils and a manufacturing method thereof, the MEMS fluxgate sensor is composed of a group of symmetrically distributed single-layer excitation coils, a group of double-layer induction coils and a closed-loop magnetic core, and the core of the MEMS fluxgate sensor lies in design and implementation of a wafer-level double-layer induction coil structure. The manufacturing method comprises the following steps: patterning the magnetic core by femtosecond laser; manufacturing a coil silicon mold by a deep reactive ion etching process; and filling the silicon mold with metal to manufacture the coil. The manufacturing of the wafer-level double-layer induction coil is realized, and the sensitivity of the MEMS fluxgate sensor can be effectively improved under the same physical size. According to the method, the iron-based amorphous ribbon is selected as a magnetic core material, the magnetic core is patterned in a femtosecond laser cutting mode, it can be guaranteed that the size error is within the range of + / -5 microns, and the pattern asymmetry influence caused by machining errors is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of fluxgate sensors based on Micro-Electro-Mechanical Systems (MEMS), and more particularly, to a MEMS fluxgate sensor with a double-layer induction coil and a manufacturing method thereof. Background Art

[0002] A fluxgate sensor (simply referred to as a fluxgate) is a high-performance vector magnetic sensor, which consists of an excitation coil, an induction coil, and a magnetic core. Its working principle is mainly based on the non-linear characteristic of the magnetization curve of the magnetic core material. The high-frequency excitation magnetic field generated by the excitation coil is used to modulate the measured magnetic field, and then a second harmonic signal proportional to the measured magnetic field is induced in the induction coil. The amplitude of this signal reflects the magnitude of the measured magnetic field. Due to the advantages of high sensitivity, low power consumption, low noise, simple principle, mature technology, and strong applicability, the fluxgate has shown great application potential in many high-tech fields such as geophysics, space exploration, aerospace, and biomedical engineering. However, traditional fluxgates are mainly made by winding enameled wires on a fixed bracket. Limited by their large volume and high energy consumption, it is difficult to meet the current development trend of miniaturized, integrated, and low-power electronic devices.

[0003] The concept of a micro fluxgate can be traced back to the 1960s and 1970s. The main challenge lies in how to achieve the miniaturization of the coil and the integration of the magnetic core. In this regard, technicians in related fields have conducted research in many areas such as the microstructural design, process design, and materials of the fluxgate. The manufacturing methods of micro fluxgates have also evolved from early silicon microfabrication processes and PCB (Printed Circuit Board) processes to the current MEMS process. The MEMS process can not only significantly reduce the volume and weight of the fluxgate, lower the power consumption, but also be compatible with modern semiconductor technologies, promoting the integration of the fluxgate and electronic circuits, which is crucial for improving the portability of the sensor. However, using the MEMS process to fabricate a three-dimensional solenoid coil requires at least three electroplating steps, each of which takes dozens of hours. The manufacturing process is complex and laborious. When the number of turns of the solenoid coil increases, or when the aspect ratio of the through holes connecting the upper and lower channels of the microcoils is large, it is often difficult to ensure efficient and high-quality electrical connections between the microcoils. Most importantly, it is difficult to fabricate wafer-level multi-layer coils. These factors greatly limit the increase in the number of turns of the coil per unit volume of the device, and thus the performance of the MEMS fluxgate is difficult to reach the level of traditional fluxgates. Therefore, how to simplify the manufacturing process while improving the performance of the MEMS fluxgate, and simultaneously improve the production efficiency and product quality, remains a problem to be solved in current research. Summary of the Invention

[0004] In view of the deficiencies in performance such as sensitivity and power consumption of existing MEMS fluxgates, as well as problems such as low production efficiency, the present invention proposes a MEMS fluxgate sensor with a double-layer induction coil and a manufacturing method thereof. The MEMS fluxgate consists of a group of symmetrically distributed single-layer excitation coils, a group of double-layer induction coils, and a closed-loop magnetic core. The core lies in the design and implementation of the wafer-level double-layer induction coil structure. This manufacturing method can realize the fabrication of multi-layer coils at the wafer-level scale, broaden the design range of micro-coil structures, and improve the performance of micro-coil products in terms of uniformity and consistency. Specifically, the present invention increases the number of coil turns and improves the sensitivity of the MEMS fluxgate under the same physical size constraints by optimizing the layout and manufacturing process of the micro-coils. In addition, the manufacturing process proposed by the present invention can allow different types of coil structures to be fabricated within half an hour, simplifies the manufacturing process, shortens the overall production cycle, and improves production efficiency.

[0005] To achieve the above technical objectives, the present invention is realized through the following technical solutions: The present invention provides a MEMS fluxgate sensor with a double-layer induction coil and a manufacturing method thereof. The MEMS fluxgate sensor consists of a group of symmetrically distributed single-layer excitation coils, a group of double-layer induction coils, and a closed-loop magnetic core. The manufacturing method includes: femtosecond laser patterning of the magnetic core; fabricating a coil silicon mold by deep reactive ion etching process; filling the silicon mold with metal to fabricate the coil. In the silicon mold fabrication stage, four 4-inch silicon wafers are used, and each of the four silicon wafers is etched to form a magnetic core cavity and a three-dimensional solenoid coil structure. The manufacturing method includes the following steps: Step 1: Process the closed-loop magnetic core strictly according to the graphic size by using femtosecond laser cutting. Step 2: Select 3 silicon wafers with a thickness of 300 μm as the first layer, the second layer, and the fourth layer of the MEMS fluxgate silicon mold respectively; select 1 silicon wafer with a thickness of 350 μm as the third layer of the MEMS fluxgate silicon mold, and reserve a magnetic core cavity with a depth of 50 μm to compensate for processing errors, ensure that the magnetic core is smoothly placed and located at the center of the excitation coil, and realize the uniform action of the excitation magnetic field on the magnetic core. Next, perform respective process treatments on the four silicon wafers. Among them, the treatment of the first-layer silicon wafer 111 includes the following steps: S1: After the silicon wafer 111 is subjected to standard cleaning, apply glue, lithography, development, DRIE (deep reactive ion etching), and deglue on the front surface of the silicon wafer 111 to obtain the upper surface channel groove of the outer-layer induction coil, the induction coil electrode groove, and the excitation coil electrode groove. S2: On the basis of S1, apply glue, perform photolithography, develop, DRIE, and remove glue on the back surface of the silicon wafer 111 to obtain the upper surface through holes of the outer induction coil, the induction coil electrode through holes, and the excitation coil electrode through holes; S3: On the basis of S2, generate a silicon dioxide protective layer on the surface of the silicon wafer 111 through LPCVD (low-pressure chemical vapor deposition); The processing of the second-layer silicon wafer 222 includes the following steps: S4: After performing standard cleaning on the silicon wafer 222, apply glue, perform photolithography, develop, DRIE, and remove glue on the front surface of the silicon wafer 222 to obtain the upper surface channel grooves of the inner induction coil and the upper surface channel grooves of the excitation coil; S5: On the basis of S4, apply glue, perform photolithography, develop, DRIE, and remove glue on the back surface of the silicon wafer 222 to obtain the upper surface through holes of the inner induction coil and the upper surface through holes of the excitation coil; S6: On the basis of S5, generate a silicon dioxide protective layer on the surface of the silicon wafer 222 through LPCVD; The processing of the third-layer silicon wafer 333 includes the following steps: S7: After performing standard cleaning on the silicon wafer 333, generate silicon dioxide by LPCVD as a mask, apply glue, perform photolithography, develop, DRIE, and remove glue on the front surface of the silicon wafer 333, and use the composite mask method to obtain the magnetic core cavity, the lower surface through hole grooves of the inner induction coil, and the lower surface through hole grooves of the excitation coil; S8: On the basis of S7, remove the remaining silicon dioxide on the surface of the silicon wafer 333 by wet etching, apply glue, perform photolithography, develop, DRIE, and remove glue on the back surface of the silicon wafer 333 to obtain the lower surface channel grooves of the inner induction coil, the lower surface channel grooves of the excitation coil, the lower surface through holes of the inner induction coil, and the lower surface through holes of the excitation coil; S9: On the basis of S8, generate a silicon dioxide protective layer on the surface of the silicon wafer 333 through LPCVD; The processing of the fourth-layer silicon wafer 444 includes the following steps: S10: After performing standard cleaning on the silicon wafer 444, apply glue, perform photolithography, develop, DRIE, and remove glue on the front surface of the silicon wafer 444 to obtain the lower surface through hole grooves of the outer induction coil; S11: On the basis of S10, apply glue, perform photolithography, develop, DRIE, and remove glue on the back surface of the silicon wafer 444 to obtain the lower surface channel grooves of the outer induction coil and the lower surface through holes of the outer induction coil; S12: On the basis of S11, generate a silicon dioxide protective layer on the surface of the silicon wafer 444 through LPCVD; Step 3: Place the magnetic core completed in Step 1 into the magnetic core cavity groove of the silicon wafer 333 in Step 2. Align and bond the silicon wafers 111, 222, 333, and 444 in sequence. Inject the zinc-aluminum alloy melt through one electrode of the coil to the other electrode, and after cooling and scribing, the manufacturing of the MEMS fluxgate sensor is completed.

[0006] Further, the closed-loop magnetic core is made of iron-based amorphous ribbon as the material.

[0007] Further, the coil silicon mold is fabricated by the double-sided etching method, and the etching of the magnetic core cavity and the coil through-hole with different depths on the same surface in the silicon mold is realized by the composite mask method.

[0008] Further, the manufacturing process is compatible with the integrated circuit process, enabling the integrated manufacturing of the sensor and the interface circuit; various complex-structured coils can be formed in one step.

[0009] After the above steps, the MEMS fluxgate sensor with a double-layer induction coil is processed and completed.

[0010] Compared with the existing technology, the beneficial effects of the present invention are as follows: The present invention designs a MEMS fluxgate sensor with a double-layer induction coil. The MEMS fluxgate realizes the fabrication of a wafer-level double-layer induction coil, which can effectively improve the sensitivity of the MEMS fluxgate under the same physical size; the MEMS fluxgate selects iron-based amorphous ribbon as the magnetic core material, and the magnetic core is patterned by femtosecond laser cutting, which can ensure that the dimensional error is within the range of ±5μm, effectively reducing the influence of pattern asymmetry caused by processing errors; the manufacturing process of the MEMS fluxgate uses the double-sided etching method to fabricate the coil silicon mold, and the composite mask method is used to realize the etching of the magnetic core cavity and the coil through-hole with different depths on the same surface in the silicon mold; the manufacturing process of the MEMS fluxgate is compatible with the integrated circuit process, enabling the integrated manufacturing of the sensor and the interface circuit; the manufacturing process of the MEMS fluxgate can form various complex-structured coils in one step, reducing the processing time and facilitating mass production. Description of the Drawings

[0011] Figure 1 is a schematic structural diagram of the MEMS fluxgate sensor described in the exemplary embodiment of the present invention; Figure 2 is an overall top view of the MEMS fluxgate sensor described in the exemplary embodiment of the present invention; Figure 3a is a flowchart of the processing method of the silicon wafer 111 of the MEMS fluxgate sensor of the present invention; Figure 3b is a flowchart of the processing method of the silicon wafer 222 of the MEMS fluxgate sensor of the present invention; Figure 3c It is a flow chart of the processing method of the silicon wafer 333 of the MEMS fluxgate sensor of the present invention; Figure 3d It is a flow chart of the processing method of the silicon wafer 444 of the MEMS fluxgate sensor of the present invention; Figure 3e It is a schematic assembly diagram of the silicon wafers 111, 222, 333, 444 of the MEMS fluxgate sensor of the present invention and the magnetic core. Specific embodiments

[0012] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0013] As Figure 1 and Figure 2 shown, the present invention relates to a MEMS fluxgate sensor with a double-layer induction coil and a manufacturing method thereof, including silicon wafers 111-444, excitation coil electrodes 2, induction coil electrodes 3, single-layer excitation coils 4, double-layer induction coils 5, and a closed-loop magnetic core 6. The magnetic core is cut by a femtosecond laser. The production of the coil is mainly divided into two parts: silicon mold etching and zinc-aluminum alloy melt filling. A multi-layer silicon wafer stacking design is adopted. The double-layer coil silicon mold is composed of four 4-inch silicon wafers. The thicknesses of the first silicon wafer 111, the second silicon wafer 222, and the fourth silicon wafer 444 are 300 μm, and the thickness of the third silicon wafer 333 is 350 μm. A magnetic core cavity with a depth of 50 μm is reserved to ensure that the magnetic core can be completely placed in the silicon mold and located in the center of the excitation coil. Both the excitation coil 4 and the induction coil 5 are three-dimensional solenoid coils. On the four silicon wafers, the DRIE process is used to etch out the corresponding coil electrode grooves, surface channel grooves, and through holes. The prepared magnetic core is accurately placed into the magnetic core cavity of the silicon wafer 333. The silicon wafers of each layer are accurately aligned and adhered according to the alignment marks to form a MEMS fluxgate silicon mold. Then, the zinc-aluminum alloy melt is injected from one electrode of the coil silicon mold and flows through the entire coil structure to the other electrode. After cooling and solidifying, the wafer is sliced to complete the production of the MEMS fluxgate.

[0014] This embodiment provides a manufacturing method of a MEMS fluxgate sensor with a double-layer induction coil. The specific processing steps include: (1) As Figure 3a shown in A1-H1 in, it is the processing of the first silicon wafer 111, and specifically includes the following steps: A1: Select a silicon wafer 111 with a thickness of 300 μm as the first layer of the silicon mold, and perform standard cleaning; B1, C1: Spin-coat a 4-μm-thick positive photoresist 100 on the front side of the silicon wafer 111, and perform the first lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching windows for the excitation coil electrode 41, the induction coil electrode 51, and the upper surface channel 52 of the outer induction coil; D1: Etch the graphic window defined in C1 through the DRIE process, with an etching depth of 150 μm, and remove the photoresist; E1, F1: Spin-coat a 4-μm-thick positive photoresist 100 on the back side of the silicon wafer 111, and perform the second lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching windows for the through-hole 42 of the excitation coil electrode, the through-hole 53 of the induction coil electrode, and the through-hole 54 of the upper surface of the outer induction coil; G1: Etch the graphic window defined in F1 through the DRIE process, with an etching depth of 150 μm, and remove the photoresist; H1: Generate a silicon dioxide protective layer 101 by LPCVD, with a thickness of 2 μm; (2) As shown in A2 - H2 in Figure 3b below, the processing of the second-layer silicon wafer 222 is as follows: A2: Select a silicon wafer 222 with a thickness of 300 μm as the second layer of the silicon mold, and perform standard cleaning; B2, C2: Spin-coat a 4-μm-thick positive photoresist 100 on the front side of the silicon wafer 222, and perform the first lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching windows for the upper surface channel 43 of the excitation coil and the upper surface channel 55 of the inner induction coil; D2: Etch the graphic window defined in C2 through the DRIE process, with an etching depth of 150 μm, and remove the photoresist; E2, F2: Spin-coat a 4-μm-thick positive photoresist 100 on the back side of the silicon wafer 222, and perform the second lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching windows for the upper surface through-hole 44 of the excitation coil and the upper surface through-hole 56 of the inner induction coil; G2: Etch the graphic window defined in F2 through the DRIE process, with an etching depth of 150 μm, and remove the photoresist; H2: Generate a silicon dioxide protective layer 101 by LPCVD, with a thickness of 2 μm; (3) As shown in A3 - J3 in Figure 3c below, the processing of the third-layer silicon wafer 333 is as follows: A3: Select a silicon wafer 333 with a thickness of 350 μm as the third layer of the silicon mold, perform standard cleaning, and generate a silicon dioxide layer 102 with a thickness of 1 μm by LPCVD, which is used as a composite mask; B3, C3: Spin-coat a 4-μm-thick positive photoresist 100 on the front side of the silicon wafer 333, and perform the first lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching windows for the through-hole grooves 45 on the lower surface of the excitation coil and the through-hole grooves 57 on the lower surface of the inner induction coil; D3: Etch the pattern window defined in C3 through the DRIE process, with an etching depth of 1 μm, to expose the silicon wafer in the areas of the through-holes 45 and 57; E3: Perform the second lithography on the front side of the silicon wafer 333, including a series of lithography steps such as exposure, development, and drying, to define the etching window for the magnetic core cavity 6; F3: Use the positive photoresist layer 100 and the silicon dioxide layer 102 as a composite mask, and etch the pattern window defined in E3 through a single DRIE process to form through-holes 45 and 57 with a depth of 200 μm and a magnetic core cavity 6 with a depth of 50 μm. Remove the photoresist and remove the remaining silicon dioxide layer on the surface of the silicon wafer 333 through wet etching; G3, H3: Spin-coat a 4-μm-thick positive photoresist 100 on the back side of the silicon wafer 333, and perform the third lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching windows for the channels 46 on the lower surface of the excitation coil and the channels 58 on the lower surface of the inner induction coil; I3: Etch the pattern window defined in H3 through the DRIE process, with an etching depth of 150 μm, and remove the photoresist; J3: Generate a silicon dioxide protection layer 101 with a thickness of 2 μm by LPCVD; (4) As shown in A4 - H4 in Figure 3d below, the processing of the fourth-layer silicon wafer 444 is as follows: A4: Select a silicon wafer 444 with a thickness of 300 μm as the fourth layer of the silicon mold and perform standard cleaning; B4, C4: Spin-coat a 4-μm-thick positive photoresist 100 on the front side of the silicon wafer 444, and perform the first lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching window for the through-hole 59 on the lower surface of the outer induction coil; D4: Etch the pattern window defined in C4 through the DRIE process, with an etching depth of 150 μm, and remove the photoresist; E4, F4: Spin-coat a 4-μm-thick positive photoresist 100 on the back side of the silicon wafer 444, and perform the second lithography, including a series of lithography steps such as exposure, development, and drying, to define the etching window for the channel 60 on the lower surface of the outer induction coil; G4: Etch the graphic window defined in F4 by DRIE process with an etching depth of 150 μm, and remove the photoresist; H2: Deposit a 2-μm-thick silicon dioxide protection layer 101 by LPCVD; (5) As Figure 3e shown, the filling process of the silicon wafer 111-444 is as follows: A: Place the prepared magnetic core into the magnetic core cavity 6 etched by J3, and bond the four fabricated silicon wafers together by high-temperature glue after aligning them according to the alignment marks; B: Inject the zinc-aluminum alloy melt 103 from one electrode into the coil silicon mold through the liquid injection hole until reaching the other electrode, cool it, and perform dicing according to the dicing marks.

[0015] After the above steps, the wafer-level MEMS fluxgate sensor processing technology is all completed.

[0016] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A MEMS fluxgate sensor with a double-layer induction coil, characterized in that: The MEMS fluxgate sensor consists of a group of symmetrically distributed single-layer excitation coils, a group of double-layer induction coils and a closed-loop magnetic core.

2. The method for manufacturing a MEMS fluxgate sensor having a double-layer induction coil according to claim 1, characterized in that: The magnetic core is patterned by femtosecond laser; the coil silicon mold is made by deep reactive ion etching process; the coil is made by metal-filled silicon mold. During the silicon mold making stage, four 4-inch silicon wafers are used and etched separately to form the magnetic core cavity and the three-dimensional solenoid coil structure.

3. The method for manufacturing a MEMS fluxgate sensor having a double-layer induction coil according to claim 2, characterized in that: The manufacturing method comprises the following steps: Step 1: Use femtosecond laser cutting to process the closed-loop magnetic core in strict accordance with the graphic dimensions; Step 2: Select 3 silicon wafers with a thickness of 300 μm, which are used as the first, second and fourth layers of the MEMS fluxgate silicon mold respectively; select 1 silicon wafer with a thickness of 350 μm as the third layer of the MEMS fluxgate silicon mold, and reserve a core cavity with a depth of 50 μm to compensate for the processing error, ensure that the core is placed smoothly and located at the center of the excitation coil, and realize the excitation magnetic field uniformly acting on the core. Next, perform respective process treatments on the four silicon wafers; Step 3: Place the magnetic core completed in step 1 into the magnetic core cavity groove of silicon wafer 333 in step 2, align and bond silicon wafer 111, silicon wafer 222, silicon wafer 333 and silicon wafer 444 in sequence, inject the zinc-aluminum alloy melt through one electrode of the coil to the other electrode, cool and slice to complete the manufacture of the MEMS fluxgate sensor.

4. The method for manufacturing a MEMS fluxgate sensor having a double-layer induction coil according to claim 3, characterized in that: The processing of the first silicon wafer 111 includes the following steps: S1: After the silicon wafer 111 is subjected to standard cleaning, the front side of the silicon wafer 111 is coated with glue, photolithography, development, DRIE (deep reactive ion etching), and de-glueing is performed to obtain the upper surface channel groove of the outer induction coil, the induction coil electrode groove, and the excitation coil electrode groove; S2: Based on S1, the back side of the silicon wafer 111 is coated with glue, photolithography, development, DRIE, and de-glueing to obtain through holes on the upper surface of the outer induction coil, through holes for the induction coil electrodes, and through holes for the excitation coil electrodes; S3: Based on S2, a silicon dioxide protective layer is generated on the surface of the silicon wafer 111 by LPCVD (low pressure chemical vapor deposition).

5. The method for manufacturing a MEMS fluxgate sensor with a double-layer induction coil according to claim 3, characterized in that: Processing of the second silicon wafer 222 The following steps are involved: S4: After the silicon wafer 222 is subjected to standard cleaning, the front side of the silicon wafer 222 is coated with glue, photolithography, development, DRIE, and de-glueing are performed to obtain the grooves on the upper surface of the inner layer induction coil and the grooves on the upper surface of the excitation coil; S5: Based on S4, the back side of the silicon wafer 222 is coated with glue, photolithography, development, DRIE, and de-glueing to obtain through holes on the upper surface of the inner layer induction coil and through holes on the upper surface of the excitation coil; S6: Based on S5, a silicon dioxide protective layer is generated on the surface of the silicon wafer 222 by LPCVD.

6. The method for manufacturing a MEMS fluxgate sensor with a double-layer induction coil according to claim 3, characterized in that: The processing of the third silicon wafer 333 includes the following steps: S7: After the silicon wafer 333 is cleaned in a standard manner, silicon dioxide is generated by LPCVD and used as a mask. Glue coating, photolithography, development, DRIE, and degumming are performed on the front side of the silicon wafer 333. A magnetic core cavity, a through-hole groove on the lower surface of the inner layer induction coil, and a through-hole groove on the lower surface of the excitation coil are obtained by using a composite mask method. S8: Based on S7, the remaining silicon dioxide on the surface of the silicon wafer 333 is removed by wet etching, and the back side of the silicon wafer 333 is coated with glue, photolithography, development, DRIE, and de-glue to obtain the channel groove on the lower surface of the inner induction coil and the channel groove on the lower surface of the excitation coil, the through hole on the lower surface of the inner induction coil, and the through hole on the lower surface of the excitation coil; S9: Based on S8, a silicon dioxide protective layer is generated on the surface of the silicon wafer 333 by LPCVD.

7. The method for manufacturing a MEMS fluxgate sensor with a double-layer induction coil according to claim 3, characterized in that: The processing of the fourth silicon wafer 444 includes the following steps: S10: After the silicon wafer 444 is subjected to standard cleaning, the front side of the silicon wafer 444 is coated with glue, photolithography, development, DRIE, and de-glueing are performed to obtain a through hole groove on the lower surface of the outer induction coil; S11: on the basis of S10, the back side of the silicon wafer 444 is coated with glue, photolithography, development, DRIE, and de-glue to obtain the channel groove on the lower surface of the outer induction coil and the through hole on the lower surface of the outer induction coil; S12: Based on S11, a silicon dioxide protective layer is generated on the surface of the silicon wafer 444 by LPCVD.

8. The MEMS fluxgate sensor according to claim 1, characterized in that: The closed-loop magnetic core is made of iron-based amorphous thin strip.

9. The method for manufacturing a MEMS fluxgate sensor according to claim 2, characterized in that: The coil silicon mold is made by a double-sided etching method, and the etching of different depths of the magnetic core cavity and the coil through hole on the same surface of the silicon mold is achieved by a composite mask method.

10. The method for manufacturing a MEMS fluxgate sensor according to claims 2-7, characterized in that: The manufacturing process is compatible with the integrated circuit process, which can realize the integrated manufacturing of sensors and interface circuits; coils with various complex structures can be formed at one time.

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