CN116106800A - Single-chip triaxial magnetic field sensor and preparation method thereof - Google Patents

Abstract

The invention discloses a single-chip triaxial magnetic field sensor and a preparation method thereof, wherein a magnetically sensitive film is grown on a substrate; the magnetically sensitive thin film array structure is manufactured through a photoetching process; preparing an insulating protective layer and a seed layer in front of the electroplating flux collector over the thin film array; and the magnetic flux collector layer is electroplated on the seed layer, and the corresponding magnetic flux controller layers are sequentially finished from thin to thick, namely, film growth and etching are only needed to be carried out on one wafer/substrate from beginning to end, and the yield is improved due to the film process of the same wafer, and the process complexity is greatly reduced. Compared with a method for independently measuring the magnetic field of each axis, the method avoids the interference of the magnetic field in the non-sensitive axis direction on the chip measurement; and the formula is simple, and a method of data fusion such as machine learning is conveniently adopted to obtain more accurate detection data.

Description

Single-chip triaxial magnetic field sensor and preparation method thereof

Technical Field

The invention belongs to the technical field of magnetic sensors, and particularly relates to a single-chip triaxial magnetic field sensor and a preparation method thereof.

Background

The miniaturized integrated triaxial magnetic field sensor can accurately feed back magnetic field signals in a three-dimensional space, is expected to further improve measurement accuracy and precision of a magnetic sensor, simultaneously realizes functions of scanning the space magnetic field signals and the like, and is widely applied to various fields of power grids, energy management, new energy automobiles, industrial manufacturing and the like. Currently, manufacturers at home and abroad including Jiangsu multidimensional and Japanese TDK respectively promote three-axis magnetic field sensors. However, due to the limitation of process conditions, the existing triaxial magnetic field sensor needs the splicing combination of a plurality of uniaxial magnetic sensitive chips with different sensitive axes, so that three different magnetic sensitive films are respectively grown on at least 2-3 wafers, etching is respectively carried out, and then splicing is carried out, thereby improving the cost and the risk of film uniformity and yield.

Disclosure of Invention

Aiming at the current situation that a plurality of TMR chips are needed to be spliced for the traditional triaxial magnetic field sensor in the prior art, the process complexity is high, the cost and the yield are to be upgraded, the invention provides the single-chip triaxial magnetic field sensor realized by the same film single etching process based on single wafer growth.

According to one aspect of the embodiments of the present invention, there is provided a single-chip tri-axial magnetic field sensor, including:

a substrate for providing support for other devices;

the magnetic sensitive thin film arrays are arranged above the substrate, have sensitive characteristics to magnetic fields in a single in-plane direction, and are covered with insulating protective layers;

each group of the magneto-sensitive film arrays are connected with the corresponding fixed value resistor module to form a Wheatstone bridge structure;

and each group of the magnetic sensitive film arrays is connected with corresponding magnetic flux controllers with different thicknesses, and the magnetic flux controllers are arranged above the magnetic sensitive film arrays.

Optionally, the magnetically sensitive thin film array includes a plurality of magnetically sensitive structural units with the same size, and all the magnetically sensitive structural units have sensitivity characteristics to a magnetic field in a single in-plane direction.

Optionally, the magnetically sensitive structure unit is a tunneling magneto-resistance film device, a giant magneto-resistance film device or an anisotropic magneto-resistance film device, and an array is formed by serial-parallel connection, and the sensitive axis direction of the array is perpendicular to the long axis direction of the magnetically sensitive structure unit.

Optionally, the fixed value resistor module and the magnetically sensitive thin film array are located on the same horizontal plane.

Optionally, a fixed included angle of 10-80 degrees exists between the long end of the magnetically sensitive thin film array and the long end of the magnetic flux controller.

Optionally, the magnetic flux controller is a material with high magnetic permeability.

Optionally, each group of magnetically sensitive film arrays are connected in series and parallel with the fixed-value resistor module to form a Wheatstone bridge structure, voltage input ends of each Wheatstone bridge structure are connected in parallel, and output ends of each Wheatstone bridge structure are independent.

Alternatively, the output voltage signals U1, U2, U3, …, un of the wheatstone bridge configuration are measured separately, expressed as un= Nnx ×hx+ Nny ×hy+ Nnz ×hz; wherein Nnx, nny, nnz are the sensitivity coefficients of the sensitive unit to triaxial magnetic fields Hx, hy, hz, respectively.

Optionally, the measurement sensitivity and measurement range of each group of the magnetically sensitive film arrays to the triaxial magnetic field are different, and each group of the magnetically sensitive film arrays can be used as a single-axis sensor to respectively realize the measurement of the magnetic field in different measurement range.

According to another aspect of the embodiment of the present invention, there is also provided a method for manufacturing a single-chip triaxial magnetic field sensor, including:

growing a magnetically sensitive film on a substrate;

preparing a magnetically sensitive film array structure and a wire through a photoetching process;

preparing an insulating protective layer and a seed layer in front of the electroplating flux collector over the thin film array;

a flux concentrator layer is electroplated over the seed layer, sequentially completing the corresponding flux controller layers from thin to thick.

Compared with the prior art, the invention has the following beneficial effects:

1. the single-chip triaxial magnetic field sensor provided by the invention only needs to perform film growth and etching on one wafer/substrate from beginning to end, and is beneficial to improving the yield and avoiding the influence caused by the difference of grown films on different wafers due to the film process of the same wafer.

2. The magnetic flux controller of the single-chip triaxial magnetic field sensor provided by the invention has the same shape and only has different thickness, so that the process complexity is greatly reduced. The fixed-value resistor module has no process difficulty and does not increase the complexity of the process. Only one die taking and cutting operation is needed, and errors caused by the fact that the relative positions change due to the fact that the die is taken and a plurality of sensor arrays are stuck are avoided.

3. According to the single-chip triaxial magnetic field sensor provided by the invention, the magnitude of the triaxial magnetic field is obtained through solving a simple equation set, and the influence of each axial magnetic field is considered; compared with a method for independently measuring the magnetic field of each axis, the method avoids the interference of the magnetic field in the non-sensitive axis direction on the chip measurement; and the formula is simple, and a method of data fusion such as machine learning is conveniently adopted to obtain more accurate detection data.

Drawings

In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawing in the description below is only one embodiment of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a top view of a single chip tri-axial magnetic field sensor according to an embodiment of the present invention;

FIG. 2 is a side view of a single chip tri-axial magnetic field sensor according to an embodiment of the present invention;

101, a substrate; 102. a magnetically sensitive thin film array; 103. a magnetic flux controller; 104. a fixed value resistor module; 105. a wire; 106. an insulating protective layer;

FIG. 3 is a graph showing the magnitude of magnetic field induced by a surface of a single-chip tri-axial magnetic field sensor when applying an X-direction magnetic field according to an embodiment of the present invention;

fig. 4 is a flowchart of a method of manufacturing a single chip tri-axial magnetic field sensor according to an embodiment of the present invention.

Detailed Description

In order to make the present application solution better understood by those skilled in the art, the following description will be made in detail and with reference to the accompanying drawings in the embodiments of the present application, it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.

In the description of the present invention, a number means one or more, a number means two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and above, below, within, etc. are understood to include the present number. The terms "first," "second," "third," and the like, if any, are used for descriptive purposes only and for distinguishing between technical features and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "configured" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art. Hereinafter, an embodiment of the present invention will be described in accordance with its entire structure.

As shown in fig. 1, the single-chip triaxial magnetic field sensor provided by the present invention includes: a substrate 101, a magnetically sensitive thin film array 102, a magnetic flux controller 103, a fixed resistance module 104, wires 105 and an insulating protective layer 106. In fig. 1, the entire magnetic field sensor is located in the XY plane, and the vertical direction is the Z axis.

The single-chip triaxial magnetic field sensor comprises at least three groups of magnetically sensitive film arrays and corresponding magnetic flux controllers with different thicknesses, and a Wheatstone bridge structure is formed by a fixed-value resistor module and the arrays.

In particular, the substrate 101 is used to provide support for other devices.

The magnetically sensitive thin film array 102 includes a plurality of magnetically sensitive structural units with the same size, the magnetically sensitive structural units with the same size are sequentially connected to form a loop, the magnetically sensitive thin film array 102 is disposed on the substrate 101 and has sensitivity to a magnetic field in a single plane (front or back), and an insulating protection layer 106 is covered above the magnetically sensitive thin film array 102.

The magnetic flux controller 103 is a strip-shaped structure located above the magnetically sensitive thin film array 102, and the magnetic flux controller 103 is a material with high magnetic permeability. In this embodiment, a magnetic flux controller 103 having a different thickness is provided above each magnetically sensitive element.

The fixed value resistor module 104, the fixed value resistor module 104 and the magnetically sensitive film array 102 are connected to form a Wheatstone bridge structure.

The black thin lines in fig. 1 are conductive films or wires. In this embodiment, the conductive wires 105 are used to connect the magnetically sensitive thin film array 102, and connect the magnetically sensitive thin film array 102 with the fixed resistor module 104 to form a bridge structure.

As an alternative embodiment, two fixed resistors are connected to each magnetically sensitive thin film array 102. Taking a magnetically sensitive thin film array 102 as an example, a magnetically sensitive structural unit of the magnetically sensitive thin film array 102 and two fixed resistors form a series circuit, wherein the two fixed resistors divide the magnetically sensitive structural unit in the series circuit into two parts with equal or close numbers.

Wherein, the resistance of each block of the fixed value resistance module is equal to the resistance of the magnetic sensitive film array 102 when the magnetic field is 0; as shown in fig. 1, a fixed resistor is connected with the magnetically sensitive thin film array 102 to form a wheatstone bridge structure, the input voltage is Uin, the resistance value of the fixed resistor is R, and when the resistance change of the magnetically sensitive thin film array 102 under a magnetic field is Δr, the voltage signal u= Δr/2 (r+ [ Δr ]) x Uin output by the wheatstone bridge.

Specifically, the magnetically sensitive thin film array 102 is a tunneling magneto-resistive thin film device, a giant magneto-resistive thin film device, or an anisotropic magneto-resistive thin film device, and is formed by series-parallel connection, and the sensitive axis direction of the array is perpendicular to the long axis direction of the magnetically sensitive structural unit. V+ and V-are inputs to the voltage source in FIG. 1, and Vout+ and Vout-are the positive and negative terminals of the output voltage of the sensor. Each set of magnetically sensitive thin film arrays 102 has independent outputs

Specifically, the shape of the sensitive unit in the magnetic sensitive film array 102 is a rectangular strip or ellipse, and the magnetic flux controller is a rectangular strip; the long end of the magnetically sensitive thin film array 102 and the long end of the magnetic flux controller 103 have a fixed included angle of 10-80 degrees. In one embodiment, the long end of the array of magnetically sensitive films 102 is at a fixed angle of 45 ° to the long end of the magnetic flux controller 103

As shown in fig. 2, the single-chip tri-axial magnetic field sensor further includes an insulating protective layer 106 disposed over the magnetically sensitive thin film array 102. The magnetic flux controller 103 above each set of magnetically sensitive thin film arrays 102 has a different thickness. Specifically, the thickness of the magnetic flux controller 103 is 1-50 μm, and the thickness of the magnetically sensitive thin film array 102 is 0.5-2 μm. The degree of change to the magnetic flux in the vicinity of the magnetically sensitive thin film array 102 is also different due to the different thickness of the magnetic flux control. The expression of the voltage signals U1, U2, U3, un output by each bridge is un= Nnx ×hx+ Nny ×hy+ Nnz ×hz; nnx, nny and Nnz are the sensitivity coefficients of the sensitive unit to the triaxial magnetic fields Hx, hy and Hz, respectively. And solving through simultaneous equations to obtain the magnitude of the triaxial magnetic field.

FIG. 3 is a graph showing the ratio of the component of the magnetic flux density in the X direction to the magnetic flux density in the outside air in the vicinity of the magnetic sensitive unit under the magnetic flux controller with different thickness, and the result of the Y-axis and Z-axis magnetic fields is similar to that shown in FIG. 3 by taking the X-axis magnetic field as an example; when the magnetic field direction is in-plane X direction, the ratio of the magnetic flux density in the X direction component to the magnetic flux density in the outside air near the magnetic sensitive unit under the magnetic flux controllers with different thicknesses is calculated, and the control effect of the magnetic flux controllers with different thicknesses on the magnetic field component in the X axis direction can be obviously seen. When the thickness of the magnetic flux controller above the magnetic sensitive unit is different, the component of the magnetic flux density above the magnetic sensitive unit in the sensitive axis direction changes, so that the output of the magnetic flux controller is different. Therefore, the sensitivity coefficient of the known magnetic sensitive unit to the triaxial magnetic field can be solved through a plurality of groups of data solution equations to obtain the triaxial magnetic field.

Fig. 4 shows a method for preparing a single-chip triaxial magnetic field sensor, including:

step S1, growing a magnetically sensitive film on a substrate;

s2, preparing a magnetically sensitive film array structure and a wire through a photoetching process;

s3, preparing an insulating protective layer and a seed layer in front of a plating magnetic flux collector above the thin film array;

and S4, electroplating a magnetic flux collector layer on the seed layer, and sequentially completing thinner and thicker magnetic flux controller layers.

Through the preparation method, the single-chip triaxial magnetic field sensor can be prepared.

The foregoing disclosure is merely illustrative of specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art will readily recognize that changes and modifications are possible within the scope of the present invention.

Claims (10)

1. A single chip tri-axial magnetic field sensor, comprising:

a substrate for providing support for other devices;

the magnetic sensitive thin film arrays are arranged above the substrate, have sensitive characteristics to magnetic fields in a single in-plane direction, and are covered with insulating protective layers;

each group of the magneto-sensitive film arrays are connected with the corresponding fixed value resistor module to form a Wheatstone bridge structure;

and each group of the magnetic sensitive film arrays is connected with corresponding magnetic flux controllers with different thicknesses, and the magnetic flux controllers are arranged above the magnetic sensitive film arrays.

2. The single chip tri-axial magnetic field sensor of claim 1 wherein said magnetically sensitive thin film array includes a plurality of equally sized magnetically sensitive structural elements, all having sensitive characteristics to a single in-plane directional magnetic field.

3. The single chip triaxial magnetic field sensor according to claim 2, wherein the magnetically sensitive structure unit is a tunneling magneto-resistive thin film device or a giant magneto-resistive thin film device or an anisotropic magneto-resistive thin film device, and an array is formed by series-parallel connection, and a sensitive axis direction of the array is perpendicular to a long axis direction of the magnetically sensitive structure unit.

4. The single chip tri-axial magnetic field sensor of claim 1 wherein said fixed value resistive module is in the same horizontal plane as the array of magnetically sensitive films.

5. The single chip tri-axial magnetic field sensor of claim 1, wherein the long end of the magnetically sensitive thin film array has a fixed angle of 10 ° to 80 ° with the long end of the magnetic flux controller.

6. The single chip tri-axial magnetic field sensor of claim 1, wherein the magnetic flux controller is a material having a high magnetic permeability.

7. The single-chip triaxial magnetic field sensor according to claim 1, wherein each group of magnetically sensitive thin film arrays are connected in series and parallel with a fixed value resistor module to form a wheatstone bridge structure, voltage input ends of each wheatstone bridge structure are connected in parallel, and output ends of each wheatstone bridge structure are independent.

8. The single chip tri-axial magnetic field sensor of claim 7, wherein each of the output voltage signals U1, U2, U3, …, un of the wheatstone bridge configuration is measured with the expression Un = Nnx xhx + Nny xhy + Nnz Hz; wherein Nnx, nny, nnz are the sensitivity coefficients of the sensitive unit to triaxial magnetic fields Hx, hy, hz, respectively.

9. The single-chip triaxial magnetic field sensor according to claim 1, characterized in that each group of magnetically sensitive thin film arrays has different measurement sensitivity and measurement range for triaxial magnetic fields, and each group of magnetically sensitive thin film arrays can be used as a single-axis sensor to respectively realize measurement for magnetic fields in different measurement range.

10. The preparation method of the single-chip triaxial magnetic field sensor is characterized by comprising the following steps of:

growing a magnetically sensitive film on a substrate;

preparing a magnetically sensitive film array structure and a wire through a photoetching process;

preparing an insulating protective layer and a seed layer in front of the electroplating flux collector over the thin film array;

a flux concentrator layer is electroplated over the seed layer, sequentially completing the corresponding flux controller layers from thin to thick.

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