Method for preparing magnetic flux collector in vertical direction of chip and corresponding magnetic flux collector

Abstract

The invention provides a method for preparing a magnetic flux collector in the vertical direction of a chip and a corresponding magnetic flux collector, and the method comprises the steps: preparing a preparation region with a trumpet-shaped or trapezoidal front view and a truncated cone-shaped three-dimensional structure at the bottom of a silicon substrate through the photoetching and etching technology, the bottom of the preparation region is wider than the top of the preparation region, and the preparation region does not penetrate through the silicon substrate; the bottom of the silicon substrate is arranged on the chip plane; depositing a magnetic flux concentrator material in the flared region to form a first magnetic flux concentrating unit; preparing a magnetic sensitive unit at the top of the silicon substrate by micro-nano processing, wherein the magnetic sensitive unit is positioned right above the first magnetic flux gathering unit; and preparing a second magnetic flux gathering unit symmetrical to the first magnetic flux gathering unit at the top of the magnetic sensitive unit. The magnetic flux collector is integrated in the z-axis direction of the chip to gather the magnetic flux, and the sensitivity of the magnetic sensitive unit with perpendicular anisotropy and the sensitivity of the sensor with the in-plane magnetic sensitive unit can be enhanced through the design.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly to a method for fabricating a flux concentrator in the vertical direction of a chip and a corresponding flux concentrator. Background Art

[0002] In recent years, driven by the Internet of Things industry, sensors, as the cornerstone of Internet of Things technology, have witnessed rapid development. Magnetic sensors are a very important type among them. Magnetic sensors are used in various fields, from detecting the geomagnetic field for navigation, vehicle positioning to detecting extremely weak magnetic fields generated by neuron activities for medical diagnosis. And with the increasing requirements for high sensitivity, low power consumption, miniaturization and other performances of sensors, the technologies used in micro magnetic sensors in integrated circuits are also constantly updated. Currently, they mainly include the Hall effect, anisotropic magnetoresistance effect, giant magnetoresistance effect, and tunneling magnetoresistance effect, and their sensitivities for detecting magnetic fields increase in turn. With the continuous improvement of detection performance, tunnel magnetoresistance (TMR) sensors have become more and more popular in biomedical applications. It can achieve the detection of human heart magnetic fields and brain magnetic fields as low as the pT level, which places higher and higher requirements on the sensitivity of magnetic sensors. How to further improve the sensitivity through various means is an important direction.

[0003] The sensitivity of magnetic sensors can be improved by selecting thin film materials, optimizing manufacturing processes, changing layer thicknesses, device geometries, etc. And the sensitivity of magnetic sensors can be further improved by integrating the magnetic sensor chip with a flux concentrator, using soft ferromagnetic materials with low saturation fields, and modifying the sensor geometry. The flux concentrator is in a horn shape. Due to the magnetic conductivity characteristics of soft magnetic materials, the magnetic flux density on the side with a small area can be enhanced, and by placing the sensor at the gap of the flux concentrator, a stronger magnetic field intensity can be detected.

[0004] Such as Figure 1 and Figure 2 show the structural diagrams of the flux concentrator in existing chips, where Figure 2 is a diagram of multiple flux concentrators connected in series. From Figure 1 and Figure 2 it can be seen that the existing flux concentrators are arranged on the substrate in a planar manner, and the substrate is located in the plane where the chip is located. Therefore, this kind of flux concentrator design is directly integrated into the chip in a planar setting manner. Although it can achieve magnetic field enhancement, this solution still has obvious deficiencies:

[0005] For the flux concentrator, when other parameters are the same, the longer the length of the flux concentrator, the better the central magnetic field amplification effect; the larger the ratio of the outer width to the inner width, the better the central magnetic field amplification effect; the smaller the gap distance (the center of the magnetic sensitive unit), the better the central magnetic field amplification effect. Therefore, the increase in the overall flux concentrator area in the chip will be unfavorable to miniaturization and integration improvement, such as Figure 2 The series connection shown will significantly increase the planar area of ​​the chip, which is not conducive to the miniaturization of the sensor chip and the improvement of its integration. Summary of the invention

[0006] In view of this, the present invention provides a method for preparing a magnetic flux concentrator in a vertical direction of a chip and a corresponding magnetic flux concentrator to solve at least one of the above-mentioned problems.

[0007] In order to achieve the above object, the present invention adopts the following scheme:

[0008] According to a first aspect of the present invention, a method for preparing a magnetic flux concentrator in a vertical direction of a chip is provided, the method being used to enhance the sensitivity of a magnetic sensitive unit with vertical anisotropy, the method comprising: using photolithography and etching techniques to prepare a preparation area at the bottom of a silicon substrate, the preparation area having a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure, the preparation area having a bottom wider than a top and not penetrating the silicon substrate, the bottom of the silicon substrate being arranged above the chip plane; depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit; using micro-nano processing to prepare a magnetic sensitive unit on the top of the silicon substrate, the magnetic sensitive unit being located directly above the first magnetic flux concentrating unit; and preparing a second magnetic flux concentrating unit symmetrically arranged with the first magnetic flux concentrating unit on the top of the magnetic sensitive unit.

[0009] As an embodiment of the present invention, the method described above comprises: depositing a silicon dioxide layer on the top of the silicon substrate; grinding the top of the silicon dioxide layer by chemical mechanical polishing; preparing an inverted trumpet-shaped or inverted trapezoidal preparation area with a truncated cone three-dimensional structure on the top of the silicon dioxide layer by photolithography and etching technology, wherein the preparation area on the top of the silicon dioxide layer and the preparation area at the bottom of the silicon substrate are symmetrically arranged with the magnetic sensitive unit as the center; and depositing a magnetic flux concentrator material in the preparation area on the top of the silicon dioxide layer to form a second magnetic flux concentrating unit.

[0010] As an embodiment of the present invention, the method described above includes: depositing a silicon dioxide layer on the top of the silicon substrate; grinding the top of the silicon dioxide layer by chemical mechanical polishing; preparing the second magnetic flux gathering unit in another silicon substrate by the method of preparing the first magnetic flux gathering unit; bonding the silicon substrate having the second magnetic flux gathering unit to the top of the silicon dioxide layer, so that the first magnetic flux gathering unit and the second magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center.

[0011] As an embodiment of the present invention, the bonding method in the above method includes direct bonding, thermal compression bonding or adhesive bonding.

[0012] According to a second aspect of the present invention, a method for preparing a magnetic flux concentrator in a vertical direction of a chip is provided, the method being used to enhance the sensitivity of an in-plane tunneling magnetoresistive sensor, the method comprising: using photolithography and etching techniques to prepare a preparation area at the bottom of a silicon substrate, the preparation area having a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure, the preparation area having a bottom wider than a top and not penetrating the silicon substrate, the bottom of the silicon substrate being arranged above the chip plane; depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit; using micro-nano processing to prepare a magnetic sensitive unit on the top of the silicon substrate, the first magnetic flux concentrating unit being located on one side of the magnetic sensitive unit; preparing a planar third magnetic flux concentrating unit and a fourth magnetic flux concentrating unit on both sides of the magnetic sensitive unit, respectively, the third magnetic flux concentrating unit being located directly above the first magnetic flux concentrating unit; preparing a second magnetic flux concentrating unit above the fourth magnetic flux concentrating unit, the second magnetic flux concentrating unit and the first magnetic flux concentrating unit being symmetrically arranged with the magnetic sensitive unit as the center.

[0013] As an embodiment of the present invention, the method for preparing a second magnetic flux gathering unit above the fourth magnetic flux gathering unit includes: depositing a silicon dioxide layer on the top of the silicon substrate; grinding the top of the silicon dioxide layer by chemical mechanical polishing; preparing an inverted trumpet-shaped or inverted trapezoidal preparation area with a three-dimensional structure of a truncated cone on the top of the silicon dioxide layer by photolithography and etching technology, the preparation area on the top of the silicon dioxide layer is located above the fourth magnetic flux gathering unit, and the preparation area on the top of the silicon dioxide layer and the preparation area at the bottom of the silicon substrate are symmetrically arranged with the magnetic sensitive unit as the center; depositing a magnetic flux concentrator material in the preparation area on the top of the silicon dioxide layer to form a second magnetic flux gathering unit.

[0014] As an embodiment of the present invention, the method for preparing a second magnetic flux gathering unit above the fourth magnetic flux gathering unit includes: depositing a silicon dioxide layer on the top of the silicon substrate; grinding the top of the silicon dioxide layer by chemical mechanical polishing; preparing the second magnetic flux gathering unit in another silicon substrate by the method of preparing the first magnetic flux gathering unit; bonding the silicon substrate having the second magnetic flux gathering unit to the top of the silicon dioxide layer, so that the first magnetic flux gathering unit and the second magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center, and so that the second magnetic flux gathering unit is located above the fourth magnetic flux gathering unit.

[0015] As an embodiment of the present invention, in the above method, the planar third magnetic flux gathering unit and the fourth magnetic flux gathering unit are horn-shaped, trapezoidal or T-shaped.

[0016] According to a third aspect of the present invention, there is provided a magnetic flux concentrator prepared in a vertical direction of a chip, the magnetic flux concentrator comprising: a first magnetic flux concentrator arranged in a silicon substrate, a magnetic sensitive unit arranged on top of the silicon substrate, and a second magnetic flux concentrator symmetrically arranged with the first magnetic flux concentrator centered on the magnetic sensitive unit, the magnetic flux concentrator being prepared using the method described above.

[0017] According to a fourth aspect of the present invention, there is provided a magnetic flux concentrator prepared in a vertical direction of a chip, the magnetic flux concentrator comprising: a first magnetic flux concentrator arranged in a silicon substrate, a magnetic sensitive unit arranged on the top of the silicon substrate, a third magnetic flux concentrator and a fourth magnetic flux concentrator, a second magnetic flux concentrator symmetrically arranged with the first magnetic flux concentrator as the center and the magnetic sensitive unit, and the magnetic flux concentrator is prepared using the method as described above.

[0018] It can be seen from the above technical scheme that the method for preparing a magnetic flux concentrator in the vertical direction of the chip provided by the present invention and the corresponding magnetic flux concentrator, in order to solve the influence of the conventional magnetic flux concentrator being too large in area and not conducive to the design of chip miniaturization, the magnetic flux is gathered by integrating the magnetic flux concentrator in the z-axis direction of the chip (the normal direction of the plane where the chip is located), and this design can enhance the sensitivity of the magnetic sensitive unit with perpendicular anisotropy (PMA). In addition, by adding a miniaturized magnetic flux concentrator in the plane where the chip is located, the magnetic field in the space, that is, the magnetic flux gathered by the magnetic flux concentrator in the direction perpendicular to the chip, can be directed and gathered to the magnetic sensitive unit in the plane where the chip is located, thereby improving the sensitivity of the sensor with the in-plane magnetic sensitive unit, while ensuring that the area of ​​the chip is not too large, which is conducive to miniaturization and improved integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0020] Figure 1 It is a top view and a cross-sectional view of an existing single magnetic flux concentrator;

[0021] Figure 2 It is a top view and a cross-sectional view of a plurality of existing magnetic flux concentrators connected in series;

[0022] Figure 3 This is a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided in an embodiment of the present application;

[0023] Figure 4 This is a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application;

[0024] Figure 5 It is a product schematic diagram of various stages of preparing a magnetic flux concentrator provided in an embodiment of the present application;

[0025] Figure 6 This is a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application;

[0026] Figure 7 It is a product schematic diagram of various stages of preparing a magnetic flux concentrator provided in an embodiment of the present application;

[0027] Figure 8 This is a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided in an embodiment of the present application;

[0028] Figure 9 This is a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application;

[0029] Figure 10 It is a product schematic diagram of various stages of preparing a magnetic flux concentrator provided in an embodiment of the present application;

[0030] Figure 11 This is a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application;

[0031] Figure 12 It is a product schematic diagram of various stages of preparing a magnetic flux concentrator provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0033] First, some technical terms involved in this application are briefly described:

[0034] The term "Tunnel Magnetoresistance" (TMR) is a technology based on the tunnel magnetoresistance effect and is widely used in magnetic sensors. Its core principle is to use the magnetic tunnel junction (MTJ) structure to adjust the resistance value by changing the magnetization direction, thereby realizing the perception of the magnetic field.

[0035] The term "perpendicular magnetic anisotropy" (PMA) is a property of a magnetic material, which refers to the phenomenon that the magnetization direction is preferentially arranged in a direction perpendicular to the film plane. It is one of the important characteristics of magnetic sensitive units.

[0036] The term "bonding" (Neural Architecture Search, NAS) refers to the process of combining two different materials or structures through a specific process method to form a whole in the field of microelectronics manufacturing and micro-nano processing.

[0037] like Figure 3 The figure shows a schematic flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by an embodiment of the present application. The method is used to enhance the sensitivity of a magnetic sensitive unit with perpendicular anisotropy. The method comprises the following steps:

[0038] Step S301: prepare a silicon substrate.

[0039] The selected silicon substrate needs to have good flatness and uniformity to ensure the accuracy and reliability of subsequent processing steps. The thickness, size and specific shape of the silicon substrate are determined according to the chip design requirements, and this application does not limit this.

[0040] Step S302: Use photolithography and etching technology to prepare a preparation area at the bottom of the silicon substrate with a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure. The bottom of the preparation area is wider than the top and does not penetrate the silicon substrate. The bottom of the silicon substrate is set above the chip plane.

[0041] A layer of photoresist is coated on the bottom of the silicon substrate, and the pattern of the trumpet-shaped or trapezoidal preparation area is transferred to the photoresist through a photolithography process. Then, a trumpet-shaped area or a trapezoidal area is etched out at the bottom of the silicon substrate using dry etching or wet etching technology.

[0042] The trumpet-shaped area or the trapezoidal area is designed to have a wide bottom and a narrow top structure, and the etching depth does not penetrate the silicon substrate. The truncated cone design of the trumpet-shaped area or the trapezoidal area can effectively gather magnetic flux and provide a basic structure for the subsequent deposition of the magnetic flux concentrator. Since the bottom of the silicon substrate is arranged above the chip plane, the magnetic flux concentrator of this embodiment is formed in the vertical direction of the chip plane.

[0043] Step S303: depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit.

[0044] In this step, a first magnetic flux gathering unit is formed by depositing soft magnetic material in the trumpet-shaped or trapezoidal preparation area, which is used to gather magnetic flux in the vertical direction and enhance the magnetic field strength. In the trumpet-shaped or trapezoidal area after etching, soft magnetic materials (such as NiFe alloys, etc.) can be deposited by electroplating or physical vapor deposition (PVD) technology. In this step, it is necessary to ensure that the deposited soft magnetic material evenly covers the inner wall of the trumpet-shaped area to form a complete first magnetic flux gathering unit. The deposition thickness is determined according to the design requirements to ensure that the flux concentrator has good magnetic conductivity.

[0045] Step S304: fabricating a magnetic sensitive unit on the top of the silicon substrate by using micro-nano processing, wherein the magnetic sensitive unit is located directly above the first magnetic flux gathering unit.

[0046] A magnetic sensitive unit is fabricated by micro-nano processing at the top of the silicon substrate opposite to the bottom. It is necessary to ensure that the position of the magnetic sensitive unit is aligned with the top of the first magnetic flux gathering unit to achieve the best magnetic flux sensing effect. The magnetic sensitive unit senses the magnetic flux gathered by the first magnetic flux gathering unit and the subsequent second magnetic flux gathering unit, and converts the magnetic field signal into an electrical signal.

[0047] Step S305: preparing a second magnetic flux gathering unit symmetrically arranged with the first magnetic flux gathering unit on the top of the magnetic sensitive unit.

[0048] Here, the shape and size of the second magnetic flux gathering unit are symmetrical to the first magnetic flux gathering unit, so as to ensure the effective gathering and guiding of the magnetic flux.

[0049] It can be seen from the above technical solution that the method for preparing a magnetic flux concentrator in the vertical direction of the chip provided by the present invention gathers the magnetic flux by integrating the magnetic flux concentrator in the z-axis direction of the chip (the normal to the plane where the chip is located). This design can enhance the sensitivity of the magnetic sensitive unit with perpendicular anisotropy (PMA), and since the magnetic flux concentrator is prepared in the vertical direction of the chip, the planar area of ​​the chip will not be increased.

[0050] like Figure 4 FIG. 1 is a flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application. The method is used to enhance the sensitivity of a magnetic sensitive unit with perpendicular anisotropy. The method comprises the following steps:

[0051] Step S401: prepare a silicon substrate.

[0052] Step S402: Use photolithography and etching technology to prepare a preparation area at the bottom of the silicon substrate, which has a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure. The bottom of the preparation area is wider than the top and does not penetrate the silicon substrate. The bottom of the silicon substrate is set above the chip plane.

[0053] Step S403: depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit.

[0054] Step S404: fabricating a magnetic sensitive unit on the top of the silicon substrate by using micro-nano processing, wherein the magnetic sensitive unit is located directly above the first magnetic flux gathering unit.

[0055] The above steps S401-S404 can be found in Figure 3 The corresponding steps S301-S304 are not further described here.

[0056] Step S405: depositing a silicon dioxide layer on the top of the silicon substrate.

[0057] On top of the silicon substrate, a silicon dioxide layer is deposited by chemical vapor deposition or thermal oxidation process. The thickness of the silicon dioxide layer needs to be at least greater than the height of the trumpet-shaped area or the trapezoidal area in the first magnetic flux gathering unit to ensure the operability of subsequent etching and deposition processes.

[0058] In this step, the role of the silicon dioxide layer is to provide a processable medium for forming a second magnetic flux gathering unit on the top, while protecting the magnetic sensitive unit from the influence of subsequent processes.

[0059] Step S406: Grind the top of the silicon dioxide layer flat by chemical mechanical polishing.

[0060] During the polishing process, chemical corrosion and mechanical grinding are combined to remove the uneven parts of the silicon dioxide layer surface to ensure that its surface is smooth and the thickness is uniform. The surface of the silicon dioxide layer after polishing needs to reach the specified flatness to facilitate the precise implementation of subsequent lithography and etching processes.

[0061] Step S407: using photolithography and etching technology to prepare an inverted trumpet-shaped or inverted trapezoidal preparation area on the top of the silicon dioxide layer and a truncated cone three-dimensional structure, wherein the preparation area on the top of the silicon dioxide layer and the preparation area on the bottom of the silicon substrate are symmetrically arranged with the magnetic sensitive unit as the center.

[0062] A layer of photoresist is coated on the top of the silicon dioxide layer, and the pattern of the area to be etched is transferred to the photoresist through a photolithography process. Then, a dry etching or wet etching technique is used to etch an inverted trumpet-shaped area or an inverted trapezoidal area in the silicon dioxide layer. The inverted trumpet-shaped area or the inverted trapezoidal area here is designed as a truncated cone structure with a wide top and a narrow bottom (contrary to the trumpet-shaped area in the silicon substrate), and it is symmetrically arranged with the trumpet-shaped area or the trapezoidal area at the bottom of the silicon substrate with the magnetic sensitive unit as the center. The symmetrical arrangement here includes that the position and shape are symmetrically related with the magnetic sensitive unit as the center.

[0063] Step S408: depositing a magnetic flux concentrator material in the preparation area on top of the silicon dioxide layer to form a second magnetic flux concentrating unit.

[0064] In the inverted trumpet-shaped area or inverted trapezoidal area of ​​the etched silicon dioxide layer, a soft magnetic material (such as NiFe alloy, etc.) is deposited by electroplating or physical vapor deposition (PVD) technology. Ensure that the deposited soft magnetic material evenly covers the inner wall of the trumpet-shaped area to form a complete second magnetic flux gathering unit. The second magnetic flux gathering unit works together with the first magnetic flux gathering unit to enhance the perception ability of the magnetic sensitive unit to the vertical magnetic field.

[0065] The various product images obtained in the above steps S401-S408 can be found in Figure 5 shown.

[0066] It can be seen from the above technical solution that the method for preparing a magnetic flux concentrator in the vertical direction of the chip provided by the present invention gathers magnetic flux by integrating the magnetic flux concentrator in the z-axis direction of the chip (the normal to the plane where the chip is located). This design of being wide at the top and narrow at the bottom (the part close to the magnetic sensitive unit is narrow) can enhance the sensitivity of the magnetic sensitive unit with perpendicular anisotropy (PMA), and since the magnetic flux concentrator is prepared in the vertical direction of the chip, the planar area of ​​the chip will not be increased.

[0067] like Figure 6FIG. 1 is a flow chart of a method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application. The method is used to enhance the sensitivity of a magnetic sensitive unit with perpendicular anisotropy. The method comprises the following steps:

[0068] Step S601: prepare a silicon substrate.

[0069] Step S602: Use photolithography and etching technology to prepare a preparation area at the bottom of the silicon substrate, which has a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure. The bottom of the preparation area is wider than the top and does not penetrate the silicon substrate. The bottom of the silicon substrate is set above the chip plane.

[0070] Step S603: depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit.

[0071] Step S604: fabricating a magnetic sensitive unit on the top of the silicon substrate by using micro-nano processing, wherein the magnetic sensitive unit is located directly above the first magnetic flux gathering unit.

[0072] The above steps S601-S604 can be found in Figure 3 The corresponding steps S301-S304 are not further described here.

[0073] Step S605: depositing a silicon dioxide layer on the top of the silicon substrate.

[0074] In this embodiment, different from step S405, the silicon dioxide layer here is relatively thin and only needs to cover the magnetic sensitive unit.

[0075] Step S606: Grind the top of the silicon dioxide layer flat by chemical mechanical polishing.

[0076] Step S607: preparing a second magnetic flux gathering unit in another silicon substrate using the method for preparing the first magnetic flux gathering unit.

[0077] That is, a silicon substrate including the same magnetic flux gathering unit is prepared again by using steps S601-S604.

[0078] Step S608: bonding the silicon substrate having the second magnetic flux gathering unit to the top of the silicon dioxide layer, so that the first magnetic flux gathering unit and the second magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center.

[0079] The various product images obtained in the above steps S601-S608 can be found in Figure 7 As shown, Figure 4The difference from the corresponding embodiment is that the present embodiment prepares the magnetic flux concentrator by bonding, where the bonding method may include direct bonding, thermal compression bonding or adhesive bonding. Figure 4 In addition to the beneficial effects corresponding to the embodiments, the preparation process can be further simplified.

[0080] like Figure 8 The method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by an embodiment of the present application is shown. The method is used to enhance the sensitivity of a sensor having an in-plane magnetic sensitive unit. The sensor having an in-plane magnetic sensitive unit (such as a TMR sensor) can sense the change of the magnetic field component in the plane (xy plane), and is mainly sensitive to the magnetic field direction parallel to the sensor plane. The method comprises the following steps:

[0081] Step S801: prepare a silicon substrate.

[0082] Step S802: Use photolithography and etching technology to prepare a preparation area at the bottom of the silicon substrate, which has a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure. The bottom of the preparation area is wider than the top and does not penetrate the silicon substrate. The bottom of the silicon substrate is set above the chip plane.

[0083] Step S803: depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit.

[0084] Step S804: a magnetic sensitive unit is fabricated on the top of the silicon substrate by using micro-nano processing, wherein the first magnetic flux gathering unit is located at one side of the magnetic sensitive unit.

[0085] In this step, Figure 3 - Figure 5 The difference between the embodiments is that the magnetic sensitive unit is not arranged directly above the first magnetic flux gathering unit, but is located on one side (left side or right side) directly above the first magnetic flux gathering unit.

[0086] Step S805: preparing a planar third magnetic flux gathering unit and a fourth magnetic flux gathering unit on both sides of the magnetic sensitive unit, respectively, wherein the third magnetic flux gathering unit is located directly above the first magnetic flux gathering unit.

[0087] Step S806: preparing a second magnetic flux gathering unit above the fourth magnetic flux gathering unit, wherein the second magnetic flux gathering unit and the first magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center.

[0088] The third magnetic flux gathering unit and the fourth magnetic flux gathering unit are introduced here to realize the directional guidance and convergence of the magnetic flux of the magnetic flux gathering unit (the first magnetic flux gathering unit and the second magnetic flux gathering unit) in the magnetic field in the space, that is, in the direction perpendicular to the chip, to the magnetic sensitive unit on the plane where the chip is located. Specifically, the third magnetic flux gathering unit is mainly used to guide the magnetic flux of the first magnetic flux gathering unit, and the fourth magnetic flux gathering unit is used to guide the magnetic flux of the second magnetic flux gathering unit. Therefore, the size of the third magnetic flux gathering unit and the fourth magnetic flux gathering unit here does not need to be too large, only a smaller size is required.

[0089] Preferably, the third magnetic flux gathering unit and the fourth magnetic flux gathering unit are horn-shaped, trapezoidal or T-shaped.

[0090] It can be seen from the above technical scheme that the method for preparing a magnetic flux concentrator in the vertical direction of the chip provided by the present invention and the addition of a miniaturized magnetic flux concentrator in the plane where the chip is located can achieve the directional guidance and convergence of the magnetic field in the space, that is, the magnetic flux gathered by the magnetic flux concentrator in the direction perpendicular to the chip to the magnetic sensitive unit in the plane where the chip is located, thereby improving the sensitivity of the sensor with in-plane magnetic sensitive units, while ensuring that the area of ​​the chip will not be too large, which is conducive to miniaturization and improved integration.

[0091] like Figure 9 A method for preparing a magnetic flux concentrator in a vertical direction of a chip provided by another embodiment of the present application is shown. The method is used to enhance the sensitivity of an in-plane tunneling magnetoresistive sensor. The method comprises the following steps:

[0092] Step S901: prepare a silicon substrate.

[0093] Step S902: Use photolithography and etching technology to prepare a preparation area at the bottom of the silicon substrate, which has a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure. The bottom of the preparation area is wider than the top and does not penetrate the silicon substrate. The bottom of the silicon substrate is set above the chip plane.

[0094] Step S903: depositing a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit.

[0095] Step S904: a magnetic sensitive unit is fabricated on the top of the silicon substrate by using micro-nano processing, wherein the first magnetic flux gathering unit is located at one side of the magnetic sensitive unit.

[0096] Step S905: preparing a planar third magnetic flux gathering unit and a fourth magnetic flux gathering unit on both sides of the magnetic sensitive unit, respectively, wherein the third magnetic flux gathering unit is located directly above the first magnetic flux gathering unit.

[0097] Step S906: depositing a silicon dioxide layer on the top of the silicon substrate.

[0098] Step S907: Use chemical mechanical polishing to flatten the top of the silicon dioxide layer.

[0099] Step S908: Use lithography and etching techniques to prepare a preparation area on the top of the silicon dioxide with an inverted trumpet shape or an inverted trapezoid shape and a three-dimensional structure of a truncated cone. The inverted trumpet-shaped area or the inverted trapezoid-shaped area on the top of the silicon dioxide layer is located above the fourth magnetic flux concentrating unit, and the inverted trumpet-shaped area or the inverted trapezoid-shaped area on the top of the silicon dioxide layer and the trumpet-shaped area or the trapezoid-shaped area at the bottom of the silicon substrate are symmetrically arranged with the magnetic sensitive unit as the center.

[0100] Step S909: Deposit a magnetic flux concentrator material in the preparation area on the top of the silicon dioxide layer to form a second magnetic flux concentrating unit.

[0101] The preparation steps of the above steps S901 - S909 are similar to Figure 4 the embodiment, the difference is that there are more preparation steps for the third magnetic flux concentrating unit and the fourth magnetic flux concentrating unit, and the relative positions of the first magnetic flux concentrating unit and the second magnetic flux concentrating unit are different. The products corresponding to each step of this preparation method can be seen Figure 10 as shown.

[0102] It can be seen from the above technical solutions that the method for preparing a magnetic flux concentrator in the vertical direction of the chip provided by the present invention can realize the directional guiding and converging of the magnetic field in space, that is, the magnetic flux concentrated by the magnetic flux concentrator in the vertical direction of the chip, to the magnetic sensitive unit on the chip plane by adding a miniaturized magnetic flux concentrator on the chip plane, thereby improving the sensitivity of the TMR sensor, and at the same time ensuring that the area of the chip is not too large, which is beneficial to miniaturization and integration improvement.

[0103] As Figure 11 shown is a method for preparing a magnetic flux concentrator in the vertical direction of a chip provided by another embodiment of the present application. This method is used to enhance the sensitivity of an in-plane tunneling magnetoresistance sensor. This method includes the following steps:

[0104] Step S1101: Prepare a silicon substrate.

[0105] Step S1102: Use lithography and etching techniques to prepare a preparation area on the bottom of the silicon substrate with a trumpet shape or a trapezoid shape in a front view and a three-dimensional structure of a truncated cone. The bottom of the preparation area is wider than the top and does not penetrate the silicon substrate. The bottom of the silicon substrate is arranged above the chip plane.

[0106] Step S1103: Deposit a magnetic flux concentrator material in the preparation area to form a first magnetic flux concentrating unit.

[0107] Step S1104: Fabricate a magnetic sensing unit on the top of the silicon substrate by means of micro-nano processing, and the first magnetic flux concentrating unit is located on one side of the magnetic sensing unit.

[0108] Step S1105: Fabricate a planar third magnetic flux concentrating unit and a fourth magnetic flux concentrating unit on both sides of the magnetic sensing unit respectively, and the third magnetic flux concentrating unit is located directly above the first magnetic flux concentrating unit.

[0109] Step S1106: Deposit a layer of silicon dioxide on the top of the silicon substrate.

[0110] Step S1107: Polish the top of the silicon dioxide layer flat by means of chemical mechanical polishing.

[0111] Step S1108: Fabricate a second magnetic flux concentrating unit in another silicon substrate by using the method for fabricating the first magnetic flux concentrating unit.

[0112] Step S1109: Bond the silicon substrate with the second magnetic flux concentrating unit on the top of the silicon dioxide layer, such that the first magnetic flux concentrating unit and the second magnetic flux concentrating unit are symmetrically arranged with the magnetic sensing unit as the center, and such that the second magnetic flux concentrating unit is located above the fourth magnetic flux concentrating unit.

[0113] Similarly, the fabrication steps of the above steps S1101 - S1109 are also similar to Figure 6 the corresponding embodiments, the difference being that there are additional fabrication steps for the third magnetic flux concentrating unit and the fourth magnetic flux concentrating unit, and the relative positions of the first magnetic flux concentrating unit and the second magnetic flux concentrating unit are different. For the products corresponding to each step of this fabrication method, reference can be made to Figure 12 as shown.

[0114] Corresponding to Figure 3 、 Figure 4 and Figure 6 For the fabrication method, an embodiment of the present application also provides a magnetic flux concentrator fabricated in the vertical direction of a chip. The magnetic flux concentrator includes: a first magnetic flux concentrating unit disposed in a silicon substrate, a magnetic sensing unit disposed on the top of the silicon substrate, and a second magnetic flux concentrating unit symmetrically disposed with the first magnetic flux concentrating unit with the magnetic sensing unit as the center. For its specific structure, reference can be made to Figure 5 and Figure 7 the schematic diagram obtained in the last step in. That is, the bottom of this magnetic flux concentrator is a silicon substrate, the first magnetic flux concentrating unit is disposed in the silicon substrate, and the wider bottom surface of the first magnetic flux concentrating unit is in the same plane as the bottom surface of the silicon substrate. A magnetic sensing unit is disposed on the top surface of the silicon substrate, and the magnetic sensing unit is covered by a silicon dioxide layer. Figure 5 Differing from Figure 7 is that Figure 5The second magnetic flux concentrating unit in [the reference] is formed within the silicon dioxide layer, while Figure 7 a silicon substrate with a second magnetic flux concentrating unit is prepared separately by using the method for preparing the first magnetic flux concentrating unit, and two silicon substrates are bonded to form a complete magnetic flux concentrator. In the final magnetic flux concentrator, the first magnetic flux concentrating unit and the second magnetic flux unit are symmetrically arranged with the magnetic sensing unit as the center.

[0115] Meanwhile, corresponding to Figure 8 、 Figure 9 and Figure 11 the preparation method, the embodiment of the present application also provides a magnetic flux concentrator prepared in the vertical direction of the chip. The magnetic flux concentrator includes: a first magnetic flux concentrating unit disposed in a silicon substrate, a magnetic sensing unit, a third magnetic flux concentrating unit, and a fourth magnetic flux concentrating unit disposed on the top of the silicon substrate. A second magnetic flux concentrating unit symmetrically arranged with the first magnetic flux concentrating unit with the magnetic sensing unit as the center. The specific structure can be referred to the schematic diagram obtained in the last step of Figure 10 and Figure 12 That is, the bottom of the magnetic flux concentrator is a silicon substrate, the first magnetic flux concentrating unit is disposed in the silicon substrate, and the wider bottom surface of the first magnetic flux concentrating unit is on the same plane as the bottom surface of the silicon substrate. A magnetic sensing unit, a third magnetic flux concentrating unit, and a fourth magnetic flux concentrating unit are disposed on the top surface of the silicon substrate. The third magnetic flux concentrating unit is disposed directly above the first magnetic flux concentrating unit, and the third magnetic flux concentrating unit and the fourth magnetic flux concentrating unit are disposed on opposite sides of the magnetic sensing unit. The magnetic sensing unit, the third magnetic flux concentrating unit, and the fourth magnetic flux concentrating unit are covered by a silicon dioxide layer. Figure 10 Different from Figure 12 in [the reference], Figure 10 the second magnetic flux concentrating unit in [the reference] is formed within the silicon dioxide layer, while Figure 12 a silicon substrate with a second magnetic flux concentrating unit is prepared separately by using the method for preparing the first magnetic flux concentrating unit, and two silicon substrates are bonded to form a complete magnetic flux concentrator. In the final magnetic flux concentrator, the second magnetic flux concentrating unit is disposed directly above the fourth magnetic flux concentrating unit, and the first magnetic flux concentrating unit and the second magnetic flux unit are symmetrically arranged with the magnetic sensing unit as the center.

[0116] As can be seen from the above technical solution, the flux concentrator prepared in the vertical direction of the chip provided by the present invention is to solve the problem that the large area of the conventional flux concentrator is not conducive to the chip miniaturization design. By integrating the flux concentrator in the z-axis direction (the normal direction of the plane where the chip is located) of the chip to converge the magnetic flux, this design can enhance the sensitivity of the magnetic sensitive unit with perpendicular magnetic anisotropy (PMA). In addition, by adding a miniaturized flux concentrator in the plane where the chip is located, it is possible to direct and converge the magnetic field in space, that is, the magnetic flux concentrated by the flux concentrator in the direction perpendicular to the chip, to the magnetic sensitive unit in the plane where the chip is located, thereby improving the sensitivity of the sensor with in-plane magnetic sensitive units, while ensuring that the area of the chip will not be too large, which is conducive to miniaturization and increased integration.

[0117] Specific embodiments are applied in the present invention to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a magnetic flux concentrator in the vertical direction of a chip, characterized in that: The method is used to enhance the sensitivity of a magnetic sensitive unit having perpendicular anisotropy, and the method comprises: Using photolithography and etching technology, a preparation area with a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure is prepared at the bottom of the silicon substrate, wherein the bottom of the preparation area is wider than the top and does not penetrate the silicon substrate, and the bottom of the silicon substrate is arranged above the chip plane; depositing a magnetic flux concentrator material in the preparation region to form a first magnetic flux concentrating unit; A magnetic sensitive unit is fabricated on the top of the silicon substrate by using micro-nano processing, and the magnetic sensitive unit is located directly above the first magnetic flux gathering unit; A second magnetic flux gathering unit symmetrically arranged with respect to the first magnetic flux gathering unit is prepared on the top of the magnetic sensitive unit.

2. The method for preparing a magnetic flux concentrator in a vertical direction of a chip as claimed in claim 1, characterized in that: The second magnetic flux gathering unit prepared on the top of the magnetic sensitive unit and symmetrically arranged with the first magnetic flux gathering unit comprises: depositing a silicon dioxide layer on top of the silicon substrate; Grinding the top of the silicon dioxide layer flat by chemical mechanical polishing; Using photolithography and etching technology, a preparation area with an inverted trumpet shape or an inverted trapezoidal shape and a truncated cone three-dimensional structure is prepared on the top of the silicon dioxide layer, and the preparation area on the top of the silicon dioxide layer and the preparation area on the bottom of the silicon substrate are symmetrically arranged with the magnetic sensitive unit as the center; A magnetic flux concentrator material is deposited in the preparation area on top of the silicon dioxide layer to form a second magnetic flux concentrating unit.

3. The method for preparing a magnetic flux concentrator in a vertical direction of a chip as claimed in claim 1, characterized in that: The second magnetic flux gathering unit prepared on the top of the magnetic sensitive unit and symmetrically arranged with the first magnetic flux gathering unit comprises: depositing a silicon dioxide layer on top of the silicon substrate; Grinding the top of the silicon dioxide layer flat by chemical mechanical polishing; Using the method for preparing the first magnetic flux gathering unit, a second magnetic flux gathering unit is prepared in another silicon substrate; The silicon substrate having the second magnetic flux gathering unit is bonded to the top of the silicon dioxide layer, so that the first magnetic flux gathering unit and the second magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center.

4. The method for preparing a magnetic flux concentrator in a vertical direction of a chip as claimed in claim 3, characterized in that: The bonding method includes direct bonding, thermal compression bonding or adhesive bonding.

5. A method for preparing a magnetic flux concentrator in the vertical direction of a chip, characterized in that: The method is used to enhance the sensitivity of a sensor having an in-plane magnetic sensitive unit, and the method comprises: Using photolithography and etching technology, a preparation area with a trumpet-shaped or trapezoidal front view and a truncated cone three-dimensional structure is prepared at the bottom of the silicon substrate, wherein the bottom of the preparation area is wider than the top and does not penetrate the silicon substrate, and the bottom of the silicon substrate is arranged above the chip plane; depositing a magnetic flux concentrator material in the preparation region to form a first magnetic flux concentrating unit; A magnetic sensitive unit is fabricated on the top of the silicon substrate by using micro-nano processing, wherein the first magnetic flux gathering unit is located on one side of the magnetic sensitive unit; A planar third magnetic flux gathering unit and a fourth magnetic flux gathering unit are respectively prepared on both sides of the magnetic sensitive unit, and the third magnetic flux gathering unit is located directly above the first magnetic flux gathering unit; A second magnetic flux gathering unit is prepared above the fourth magnetic flux gathering unit, and the second magnetic flux gathering unit and the first magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center.

6. The method for preparing a magnetic flux concentrator in a vertical direction of a chip as claimed in claim 5, characterized in that: The preparing a second magnetic flux gathering unit above the fourth magnetic flux gathering unit comprises: depositing a silicon dioxide layer on top of the silicon substrate; Grinding the top of the silicon dioxide layer flat by chemical mechanical polishing; A preparation area with an inverted trumpet shape or an inverted trapezoidal shape and a truncated cone three-dimensional structure is prepared on the top of the silicon dioxide layer by using photolithography and etching technology, wherein the preparation area on the top of the silicon dioxide layer is located above the fourth magnetic flux gathering unit, and the preparation area on the top of the silicon dioxide layer and the preparation area on the bottom of the silicon substrate are symmetrically arranged with the magnetic sensitive unit as the center; A magnetic flux concentrator material is deposited in the preparation area on top of the silicon dioxide layer to form a second magnetic flux concentrating unit.

7. The method for preparing a magnetic flux concentrator in a vertical direction of a chip as claimed in claim 5, characterized in that: The preparing a second magnetic flux gathering unit above the fourth magnetic flux gathering unit comprises: depositing a silicon dioxide layer on top of the silicon substrate; Grinding the top of the silicon dioxide layer flat by chemical mechanical polishing; Using the method for preparing the first magnetic flux gathering unit, a second magnetic flux gathering unit is prepared in another silicon substrate; The silicon substrate having the second magnetic flux gathering unit is bonded to the top of the silicon dioxide layer, so that the first magnetic flux gathering unit and the second magnetic flux gathering unit are symmetrically arranged with the magnetic sensitive unit as the center, and the second magnetic flux gathering unit is located above the fourth magnetic flux gathering unit.

8. The method for preparing a magnetic flux concentrator in a vertical direction of a chip as claimed in claim 5, characterized in that: The planar third magnetic flux gathering unit and the fourth magnetic flux gathering unit are horn-shaped, trapezoidal or T-shaped.

9. A magnetic flux concentrator prepared in the vertical direction of a chip, characterized in that: The magnetic flux concentrator includes: a first magnetic flux concentrator arranged in a silicon substrate, a magnetic sensitive unit arranged on the top of the silicon substrate, and a second magnetic flux concentrator symmetrically arranged with the first magnetic flux concentrator centered on the magnetic sensitive unit. The magnetic flux concentrator is prepared using the method described in any one of claims 1 to 4.

10. A magnetic flux concentrator prepared in the vertical direction of a chip, characterized in that: The magnetic flux concentrator includes: a first magnetic flux concentrating unit arranged in a silicon substrate, a magnetic sensitive unit, a third magnetic flux concentrating unit and a fourth magnetic flux concentrating unit arranged on the top of the silicon substrate, and a second magnetic flux concentrating unit symmetrically arranged with the first magnetic flux concentrating unit as the center. The magnetic flux concentrator is prepared using the method described in any one of claims 5-8.

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