Preparation Method of Magnetoresistive Sensor and Magnetoresistive Sensor

Abstract

The present application relates to a method for manufacturing a magnetoresistive sensor and a magnetoresistive sensor, including: providing a substrate, where an integrated circuit is provided on the substrate; depositing n silicon dioxide film layers on the surface of the substrate, wherein the density of the silicon dioxide film layer farthest from the substrate is greater than the density of the silicon dioxide film layer closest to the substrate, and n≥2; forming a magnetic material layer on the surface of the silicon dioxide film layer; forming a stacked structure on the surface of the magnetic material layer, and the stacked structure is used to jointly form a magnetoresistive sensor with the magnetic material layer, the integrated circuit and n silicon dioxide film layers. By depositing the silicon dioxide film layers in multiple steps to form a structure with gradually changing film formation parameters, the probability of micro-region component redistribution of the magnetic material at high temperatures is reduced, avoiding the performance degradation of the magnetic material, thereby improving the performance of the magnetoresistive sensor.

Description

Technical Field

[0001] This application relates to the technical field of sensors, and particularly to a method for manufacturing a magnetoresistive sensor and a magnetoresistive sensor. Background Art

[0002] Magnetoresistive sensors are made based on the magnetoresistive effect of magnetic materials. Among them, the basic structure of an anisotropic magnetoresistive (AMR) sensor is a Wheatstone bridge composed of four magnetic thin-film resistors. The magnetic thin film has anisotropic properties, and its resistance value is related to the angle between the current direction and the built-in magnetic field vector in the thin film. By measuring the change in the thin-film resistance value, the parameters of the external magnetic field can be characterized. Therefore, the performance of an AMR magnetoresistive sensor is determined by the performance of the magnetic thin film. In the manufacturing process of a typical AMR magnetoresistive sensor, due to high-temperature treatment, the structure of silicon dioxide changes, which in turn induces the redistribution of the components of the magnetic thin film, resulting in the degradation of the performance of the magnetic thin film and thus reducing the performance of the magnetoresistive sensor. Summary of the Invention

[0003] Based on this, it is necessary to provide a method for manufacturing a magnetoresistive sensor and a magnetoresistive sensor to address the problem of the degradation of the performance of the magnetic thin film caused by the high-temperature process in the prior art.

[0004] To achieve the above object, this application provides a method for manufacturing a magnetoresistive sensor, including:

[0005] Providing a substrate, on which an integrated circuit is provided;

[0006] Depositing n silicon dioxide film layers on the surface of the substrate, where the density of the silicon dioxide film layer farthest from the substrate is greater than the density of the silicon dioxide film layer closest to the substrate, and n≥2;

[0007] Forming a magnetic material layer on the surface of the silicon dioxide film layer;

[0008] Forming a stacked structure on the surface of the magnetic material layer, and the stacked structure is used to jointly form a magnetoresistive sensor with the magnetic material layer, the integrated circuit, and n silicon dioxide film layers.

[0009] In one embodiment, n≥3, and the depositing n silicon dioxide film layers on the surface of the substrate includes:

[0010] Depositing n silicon dioxide film layers with a gradually changing density and / or thickness on the surface of the substrate, where the thickness gradually changes such that the thickness of the silicon dioxide film layer decreases gradually in the direction away from the substrate.

[0011] In one embodiment, an n-layer silicon dioxide film layer with a gradually changing density is deposited on the surface of the substrate, including:

[0012] The n-layer silicon dioxide film layer is deposited on the surface of the substrate by multi-step deposition with a gradually increasing deposition temperature and / or a gradually decreasing rate in sequence.

[0013] In one embodiment, n = 4, and the n-layer silicon dioxide film layer is deposited on the surface of the substrate by multi-step deposition with a gradually increasing deposition temperature and / or a gradually decreasing rate in sequence, including:

[0014] Deposit the first film layer at a rate of 200 - 300 nm / min, and the deposition temperature is 300 °C;

[0015] Deposit the second film layer at a rate of 100 - 200 nm / min, and the deposition temperature is 350 °C;

[0016] Deposit the third film layer at a rate of 80 - 100 nm / min, and the deposition temperature is 400 °C;

[0017] Deposit the fourth film layer at a rate of 30 - 80 nm / min, and the deposition temperature is 450 °C.

[0018] In one embodiment, the first film layer accounts for 40% of the total thickness, the second film layer accounts for 30% of the total thickness, the third film layer accounts for 16% of the total thickness, and the fourth film layer accounts for 14% of the total thickness. The total thickness is the sum of the thicknesses of the n-layer silicon dioxide film layer.

[0019] In one embodiment, n ≥ 4, and depositing the n-layer silicon dioxide film layer on the surface of the substrate includes:

[0020] Deposit the n-layer silicon dioxide film layer on the surface of the substrate, where the density of the m-layer silicon dioxide film layer changes alternately, and m ≤ n.

[0021] In one embodiment, n ≥ 5, and depositing the n-layer silicon dioxide film layer on the surface of the substrate, where the density of the m-layer silicon dioxide film layer changes alternately, includes:

[0022] Deposit the first film layer on the surface of the substrate;

[0023] Deposit the second film layer and the third film layer alternately on the surface of the first film layer. The density of the second film layer is greater than that of the first film layer and less than that of the third film layer.

[0024] In one embodiment, n = 5, and depositing the first film layer on the surface of the substrate includes:

[0025] Deposit the first film layer at a rate of 200 - 300 nm / min, and the deposition temperature is 300 °C;

[0026] Alternately deposit the second film layer and the third film layer on the surface of the first film layer, including:

[0027] Deposit one layer of the second film layer at a rate of 80 - 100 nm / min, and the deposition temperature is 400 °C;

[0028] Deposit one layer of the third film layer at a rate of 30 - 80 nm / min, and the deposition temperature is 450 °C;

[0029] Deposit another layer of the second film layer at a rate of 80 - 100 nm / min, and the deposition temperature is 400 °C;

[0030] Deposit another layer of the third film layer at a rate of 30 - 80 nm / min, and the deposition temperature is 450 °C.

[0031] In one embodiment, the first film layer accounts for 60% of the total thickness, one layer of the second film layer accounts for 10% of the total thickness, one layer of the third film layer accounts for 10% of the total thickness, and the total thickness is the sum of the thicknesses of n layers of silicon dioxide film layers.

[0032] In one embodiment, it is made by using the preparation method of the magnetoresistive sensor according to any one of claims 1 to 9.

[0033] The above preparation method of the magnetoresistive sensor forms a structure with gradually changing parameters of the silicon dioxide film layer through multi-step deposition, and the density of the silicon dioxide film layer closest to the magnetic material layer is high. Based on the above structure, the change in the properties of the silicon dioxide film layer at high temperature has little impact on the magnetic material, greatly reducing the probability of micro-region component redistribution of the magnetic material during the high-temperature process, thereby improving the performance of the magnetoresistive sensor. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a schematic flow chart of the preparation method of the magnetoresistive sensor provided in one embodiment;

[0036] Figure 2 It is a schematic structural diagram of the magnetoresistive sensor provided in one embodiment;

[0037] Figure 3 It is a comparison diagram of the magnetoelectric conversion characteristic curves of the embodiments and the comparative solutions provided in one embodiment. Detailed implementation manners

[0038] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application is more thorough and comprehensive.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] As used herein, the singular forms "a", "one layer" and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprise / include" or "have" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the related listed items.

[0041] Please refer to Figure 1 , Figure 1 It is a schematic flow diagram of the preparation method of the magnetoresistive sensor provided in one embodiment.

[0042] The present application provides a preparation method of a magnetoresistive sensor, including steps S100, S200, S300 and S400, which are specifically as follows.

[0043] Step S100: Provide a substrate, and an integrated circuit is provided on the substrate.

[0044] A magnetoresistive sensor usually fabricates an integrated circuit and a magnetic material on a semiconductor substrate. Generally, the active devices, passive components and wirings required in the circuit are interconnected according to a certain circuit and integrated on the substrate as a whole to form an integrated circuit with the required circuit functions. Then, a magnetic material is provided on the metal wiring layer of the integrated circuit. Optionally, local doping can be performed on the substrate to form PN junctions and ohmic contacts, etc., for the purpose of changing the electrical properties of the semiconductor.

[0045] Among them, a silicon wafer can be selected as the substrate in this embodiment, and the silicon wafer can be pre-treated. The pre-treatment includes fabricating corresponding circuit devices and conductive pads on the silicon wafer using CMOS process or other standard IC processes. The electrical connection between the magnetic material and the circuit devices on the substrate is achieved through the conductive pads. Specifically, in this embodiment, the CMOS process can be integrated into the silicon wafer. After fabricating the Application Specific Integrated Circuit (ASIC), a layer of insulating dielectric layer (such as silicon dioxide) will cover its surface. For this, Chemical Mechanical Polishing (CMP) technology can be used to roughly grind the insulating dielectric layer on the surface of the ASIC circuit to achieve surface planarization.

[0046] Step S200: Deposit n layers of silicon dioxide film layers on the surface of the substrate, where the density of the silicon dioxide film layer farthest from the substrate is greater than that of the silicon dioxide film layer closest to the substrate, and n≥2.

[0047] In one embodiment, plasma-enhanced chemical vapor deposition (PECVD) can be used to deposit silicon dioxide film layers in multiple steps on the surface of the substrate, and the total thickness of the film layers is about 500 nm. The PECVD process ionizes the gas containing atoms of the thin film components by means of microwave or radio frequency, etc., to form a plasma locally. The plasma has strong chemical activity and is very easy to react, and can deposit the desired thin film on the substrate. After depositing the silicon dioxide film layer, the silicon dioxide film layer is finely polished so that its Rq (root mean square roughness) ≤ 0.6 nm, and then a film layer with a higher flatness is obtained, which can have good surface contact characteristics with the adjacent upper material. In this way, it can ensure that there is a buffer material between the substrate and the magnetic material layer, making the distribution of the magnetic material more uniform.

[0048] Step S300: Form a magnetic material layer on the surface of the silicon dioxide film layer.

[0049] It can be understood that the magnetic material layer has strong magnetic anisotropy. In one embodiment, Permalloy thin film (Ni 81 Fe 19 ) is used as the magnetic material layer. Sputtering or evaporation and other processes can be used to grow the Permalloy thin film on the surface of the silicon dioxide film layer, and then photolithography and etching processes are used to pattern the Permalloy thin film, and at the same time, lead windows are etched. The pattern can be the required geometric shape, such as linear, serpentine pattern, etc. Optionally, the processed thin film can be arranged in the form of strips to form a planar linear array to increase the area for the magnetoresistance to sense the magnetic field.

[0050] Step S400: A stacked structure is formed on the surface of the magnetic material layer, and the stacked structure is used to jointly form a magnetoresistive sensor with the magnetic material layer, the integrated circuit, and the n-layer silicon dioxide film layer.

[0051] By using a film-forming process of multi-step deposition to prepare the silicon dioxide film layer, a film layer structure with gradually changing parameters can be formed. At the same time, the density of the outermost silicon dioxide film layer away from the substrate is high, which reduces the probability of micro-region component redistribution in the magnetic material layer during the subsequent heat annealing process and reduces the impact on the performance of the magnetic material.

[0052] In one embodiment, when n≥3, step S200 of depositing an n-layer silicon dioxide film layer on the substrate surface includes step S210.

[0053] Step S210: Deposit an n-layer silicon dioxide film layer with gradually changing density and / or thickness on the substrate surface, where the thickness change means that the thickness of the silicon dioxide film layer gradually decreases in the direction away from the substrate.

[0054] It can be understood that the silicon dioxide film layer structure can be such that only the density changes gradually, only the thickness changes gradually, or both the density and the thickness change gradually, that is, the silicon dioxide film layer structure has gradually changing parameters. It should be noted that for the above three structures with gradually changing parameters, the density of the silicon dioxide layer closest to the magnetic material is high, that is, it is greater than the density of the silicon dioxide layer closest to the substrate.

[0055] Among them, in one embodiment, n≥3, and an n-layer silicon dioxide film layer with gradually changing density is deposited on the substrate surface, that is, the thickness of each layer is the same, and only the density changes gradually. In other embodiments, depositing an n-layer silicon dioxide film layer with gradually changing density on the substrate surface includes: depositing an n-layer silicon dioxide film layer on the substrate surface by using multi-step deposition with gradually increasing deposition temperature and / or gradually decreasing rate in sequence. Specifically, the way to change the density of the silicon dioxide thin film can be to only gradually increase the deposition temperature or only gradually decrease the deposition rate, or to simultaneously increase the temperature gradually and decrease the rate gradually. In addition, appropriate doping materials can be added or parameters such as deposition pressure, gas flow rate, power of the power supply, and distance between the upper and lower electrodes can be changed to change the density of the thin film. This embodiment does not limit this, and it is preferred to change the density of the film layer by changing the two process parameters of temperature and rate.

[0056] In one embodiment, n≥3, and an n-layer silicon dioxide film layer with gradually changing density and thickness is deposited on the substrate surface, that is, the density and thickness of each layer change gradually. In other embodiments, the n-layer silicon dioxide film layer is deposited on the substrate surface by multi-step deposition with gradually increasing deposition temperature and gradually decreasing rate. The n = 4, including: depositing the first film layer at a rate of 200 - 300 nm / min, with a deposition temperature of 300 °C; depositing the second film layer at a rate of 100 - 200 nm / min, with a deposition temperature of 350 °C; depositing the third film layer at a rate of 80 - 100 nm / min, with a deposition temperature of 400 °C; depositing the fourth film layer at a rate of 30 - 80 nm / min, with a deposition temperature of 450 °C; wherein, the first film layer accounts for 40% of the total thickness, the second film layer accounts for 30% of the total thickness, the third film layer accounts for 16% of the total thickness, and the fourth film layer accounts for 14% of the total thickness. The total thickness is the sum of the thicknesses of the n-layer silicon dioxide film layer. By controlling the deposition temperature and rate, the change in the density of each film layer is realized. In this embodiment, the relationship of the density of each film layer is: the first film layer < the second film layer < the third film layer < the fourth film layer, and the thickness of each film layer decreases in sequence along the direction away from the substrate, which can reduce the residual stress of the film layer.

[0057] In one embodiment, n≥3, and an n-layer silicon dioxide film layer with gradually changing thickness is deposited on the substrate surface. That is, the density of each film layer is the same, and the density can be greater than the density of the first film layer in the previous embodiment, while the thickness gradually decreases along the direction away from the substrate. Such a film layer structure is arranged so that the property change during the high-temperature process will not affect the magnetic material layer.

[0058] In one of the embodiments, when n≥4, step S200 of depositing the n-layer silicon dioxide film layer on the substrate surface includes step S220.

[0059] Step S220: Depositing an n-layer silicon dioxide film layer on the substrate surface, wherein the density of the m-layer silicon dioxide film layer changes alternately, and m≤n. Specifically, the thickness of each layer is not limited.

[0060] Wherein, when n≥5, step S220 includes step S221 and step S222.

[0061] Step S221: Depositing the first film layer on the substrate surface.

[0062] Step S222: Alternately depositing the second film layer and the third film layer on the surface of the first film layer. The density of the second film layer is greater than the density of the first film layer and less than the density of the third film layer.

[0063] In one embodiment, when n = 5, step S221 includes: depositing the first film layer at a rate of 200 - 300 nm / min, with a deposition temperature of 300 °C; step S222 includes: depositing a second film layer at a rate of 80 - 100 nm / min, with a deposition temperature of 400 °C; depositing a third film layer at a rate of 30 - 80 nm / min, with a deposition temperature of 450 °C; depositing another second film layer at a rate of 80 - 100 nm / min, with a deposition temperature of 400 °C; depositing another third film layer at a rate of 30 - 80 nm / min, with a deposition temperature of 450 °C.

[0064] A method of gradually increasing the deposition temperature and gradually decreasing the rate is adopted to enhance the density of the film layer. Among them, the density of the second film layer is less than that of the third film layer, and the second film layer and the third film layer are alternately formed into a film. Specifically, the first film layer accounts for 60% of the total thickness, one second film layer accounts for 10% of the total thickness, one third film layer accounts for 10% of the total thickness, and the total thickness is the sum of the thicknesses of n silicon dioxide film layers. The density distribution from the first film layer to another third film layer is: the loosest / slightly denser / the densest / slightly denser / the densest.

[0065] In one of the embodiments, step S400 forms a stacked structure on the surface of the magnetic material layer, and the stacked structure is used to jointly form a magnetoresistive sensor with the magnetic material layer, the integrated circuit, and the n silicon dioxide film layers, including step S410 and step S420.

[0066] Step S410: sequentially form a sacrificial layer, a metal layer, and an insulating layer on the magnetic material layer.

[0067] In one embodiment, a sacrificial layer and a metal layer can be deposited on the surface of the permalloy thin film (Ni 81 Fe 19 ) by processes such as evaporation or sputtering. The sacrificial layer can be titanium or titanium tungsten, etc., and the metal layer can be aluminum or silicon-aluminum alloy, etc. In this embodiment, titanium tungsten and aluminum are preferably used as the sacrificial layer and the metal layer respectively, and then photolithography and chemical etching processes are used to pattern the titanium tungsten and aluminum to open a lead window to expose the permalloy thin film. Among them, because an acid is needed to etch aluminum, and the acid will damage the permalloy thin film, titanium tungsten can separate the aluminum from the permalloy thin film, and the aluminum layer can be used to provide an electrical connection between the substrate and the permalloy thin film. The insulating layer (such as silicon nitride) is used as a protective layer for the entire magnetoresistive sensor, and holes are opened in the insulating layer to expose only the part in contact with the outside to protect each layer from damage and contamination.

[0068] Step S420: anneal the magnetoresistive sensor.

[0069] It should be noted that the annealing process can occur after the formation of the magnetic material layer, or after the etching of the magnetic material layer, or after the deposition of the insulating layer. There is no difference among the above three cases, so this embodiment does not limit this. Optionally, annealing is performed after the deposition of the insulating layer, and the annealing temperature is 400-450 °C. Annealing can eliminate lattice defects and restore lattice order. This embodiment provides the micro-region component ratio of the permalloy thin film (Ni 81 Fe 19 ) before and after annealing. Among them, taking the one-step deposition of the silicon dioxide film layer as a comparative scheme, please refer to Table 1 for details. From the data in the table, it can be seen that in this embodiment, by multi-step depositing the silicon dioxide film layer, the iron-nickel ratio does not change before and after annealing, while the iron-nickel ratio in the comparative scheme changes. It can be seen from this that the structure of the silicon dioxide film layer obtained by multi-step deposition has less influence on the permalloy thin film during the annealing process.

[0070] Table 1 Comparison table of iron-nickel ratios for one-step and multi-step deposition of silicon dioxide film layers

[0071]

[0072] The preparation method of the magnetoresistive sensor provided in the above embodiment grows n layers of silicon dioxide film layers through a multi-step deposition process to form a structure with gradually changing parameters. At the same time, the density of the silicon dioxide layer closest to the magnetic material is high. As a result, the influence of the property changes (such as refractive index and H content, etc.) of the silicon dioxide during the subsequent annealing process on the magnetic material layer is greatly reduced. Therefore, the probability of micro-region component redistribution of the magnetic material at high temperature is reduced, avoiding the performance degradation of the magnetic material, thereby improving the performance of the magnetoresistive sensor.

[0073] This application also provides a magnetoresistive sensor, which can be made by using the preparation method of the magnetoresistive sensor provided in the above embodiment. It can reduce the probability of micro-region component redistribution of the magnetic material layer during the annealing process, and can well sense weak magnetic fields within the range of the geomagnetic field for measurement. It can be made into various proximity switches or various displacement, angle, and rotational speed sensors, etc., and can be applied to compasses, rotational position sensing, and linear position measurement in various navigation systems. In one embodiment, please refer to Figure 2 and Figure 3 , Figure 2 which is a structural diagram of a position magnetoresistive sensor. The position sensor can detect the movement of an object or determine its relative position measured from a given reference point. The magnetic material therein has the property of magnetostriction. When an external magnetic field is applied, the magnetic material will change its size or shape. Therefore, the position of the object can be determined based on this principle.

[0074] In addition, the technology of one-step depositing the silicon dioxide film layer is used as a comparative scheme to compare with this embodiment. Figure 3The figure shows the comparison of the magnetoelectric conversion characteristic curves of the position magnetoresistive sensors made for this embodiment and the comparative scheme. The magnetoelectric conversion characteristic is the most basic characteristic of the magnetoresistive sensor. Specifically, with the magnetic induction intensity as the horizontal axis and the output voltage as the vertical axis, data plotting is performed. As can be seen from the figure, the slope of this embodiment is higher than that of the comparative scheme, so it can be obtained that the magnetoresistive sensor of this embodiment has higher sensitivity and better performance.

[0075] It should be understood that although Figure 1 the steps in the flowchart of Figure 1 are shown in sequence according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover,

[0076] In the description of this specification, the descriptions referring to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. mean that the specific features, structures, materials or features described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0077] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0078] The above-described embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a magnetoresistive sensor, characterized in that, Including: Providing a substrate provided with an integrated circuit; Depositing n silicon dioxide film layers on the surface of the substrate, wherein the density of the silicon dioxide film layer farthest from the substrate is greater than the density of the silicon dioxide film layer closest to the substrate, and n≥3; Forming a magnetic material layer on the surface of the silicon dioxide film layer; Forming a stacked structure on the surface of the magnetic material layer, and the stacked structure is used to jointly form a magnetoresistive sensor with the magnetic material layer, the integrated circuit and n silicon dioxide film layers; The depositing n silicon dioxide film layers on the surface of the substrate includes: Depositing n silicon dioxide film layers with gradually changing density and / or gradually changing thickness on the surface of the substrate, wherein the thickness gradually changes such that the thickness of the silicon dioxide film layer gradually decreases in the direction away from the substrate.

2. The manufacturing method of the magnetoresistive sensor according to claim 1, characterized in that, Depositing n silicon dioxide film layers with gradually changing density on the surface of the substrate includes: Successively depositing n silicon dioxide film layers on the surface of the substrate by multi-step deposition with gradually increasing deposition temperature and / or gradually decreasing rate.

3. The manufacturing method of the magnetoresistive sensor according to claim 2, characterized in that, When n = 4, the successively depositing n silicon dioxide film layers on the surface of the substrate by multi-step deposition with gradually increasing deposition temperature and / or gradually decreasing rate includes: Depositing the first film layer at a rate of 200 - 300 nm / min, and the deposition temperature is 300 °C; Depositing the second film layer at a rate of 100 - 200 nm / min, and the deposition temperature is 350 °C; Depositing the third film layer at a rate of 80 - 100 nm / min, and the deposition temperature is 400 °C; Depositing the fourth film layer at a rate of 30 - 80 nm / min, and the deposition temperature is 450 °C.

4. The manufacturing method of the magnetoresistive sensor according to claim 3, characterized in that The first film layer accounts for 40% of the total thickness, the second film layer accounts for 30% of the total thickness, the third film layer accounts for 16% of the total thickness, and the fourth film layer accounts for 14% of the total thickness, and the total thickness is the sum of the thicknesses of the n silicon dioxide film layers.

5. The manufacturing method of the magnetoresistive sensor according to claim 1, wherein When n≥4, the depositing n silicon dioxide film layers on the surface of the substrate includes: Depositing n silicon dioxide film layers on the surface of the substrate, wherein the density of m silicon dioxide film layers changes alternately, and m≤n.

6. The preparation method of the magnetoresistive sensor according to claim 5, characterized in that, When n≥5, the depositing n silicon dioxide film layers on the surface of the substrate, wherein the density of m silicon dioxide film layers changes alternately, includes: Depositing a first film layer on the surface of the substrate; Alternately depositing a second film layer and a third film layer on the surface of the first film layer, and the density of the second film layer is greater than the density of the first film layer and less than the density of the third film layer.

7. The manufacturing method of the magnetoresistive sensor according to claim 6, characterized in that, When n = 5, the depositing a first film layer on the surface of the substrate includes: Depositing the first film layer at a rate of 200 - 300 nm / min, and the deposition temperature is 300 °C; The alternately depositing a second film layer and a third film layer on the surface of the first film layer includes: Depositing one layer of the second film layer at a rate of 80 - 100 nm / min, and the deposition temperature is 400 °C; Depositing one layer of the third film layer at a rate of 30 - 80 nm / min, and the deposition temperature is 450 °C; Depositing another layer of the second film layer at a rate of 80 - 100 nm / min, and the deposition temperature is 400 °C; Deposit another layer of the third film layer at a rate of 30 to 80 nm / min, and the deposition temperature is 450 °C.

8. The manufacturing method of the magnetoresistive sensor according to claim 7, characterized in that, The first film layer accounts for 60% of the total thickness, one layer of the second film layer accounts for 10% of the total thickness, one layer of the third film layer accounts for 10% of the total thickness, and the total thickness is the sum of the thicknesses of n layers of silicon dioxide film layers.

9. A magnetoresistive sensor, characterized in that, It is fabricated by using the method for preparing a magnetoresistive sensor according to any one of claims 1 to 8.

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