A single-chip triaxial magnetic field sensor and a method for manufacturing the same

Abstract

This invention discloses a single-chip triaxial magnetic field sensor and its fabrication method. The method involves growing a magnetically sensitive thin film on a substrate; constructing a magnetically sensitive thin film array using photolithography; fabricating an insulating protective layer and a seed layer before electroplating a magnetic flux concentrator on top of the thin film array; electroplating a magnetic flux concentrator layer on the seed layer; and sequentially completing the corresponding magnetic flux controller layers from thin to thick. This means that the entire process, from start to finish, only requires thin film growth and etching on a single wafer / substrate. Furthermore, the completely wafer-based thin film process improves yield and significantly reduces process complexity. Compared to methods that measure the magnetic field magnitude of each axis separately, this method avoids interference from magnetic fields in non-sensitive axis directions on chip measurements. The formula is also simple, facilitating the use of data fusion methods such as machine learning to obtain more accurate detection data.

Description

Technical Field

[0001] This invention belongs to the field of magnetic sensor technology, and particularly relates to a single-chip triaxial magnetic field sensor and its fabrication method. Background Technology

[0002] Miniaturized integrated triaxial magnetic field sensors can accurately feed back magnetic field signals in three-dimensional space, potentially further improving the measurement accuracy and precision of magnetic sensors. They also enable functions such as scanning spatial magnetic field signals, and are widely used in power grids, energy management, new energy vehicles, industrial manufacturing, and many other fields. Currently, domestic and international manufacturers, including Jiangsu Multidimensional and Japan's TDK, have launched triaxial magnetic field sensors. However, due to limitations in manufacturing processes, existing triaxial magnetic field sensors require the assembly of multiple single-axis magnetic sensing chips with different sensitive axes. This necessitates growing three different magnetic sensing films on at least two to three wafers, etching them separately, and then assembling them, increasing costs and raising risks related to film uniformity and yield. Summary of the Invention

[0003] In view of the current situation where existing triaxial magnetic field sensors require multiple TMR chips to be spliced ​​together, resulting in high process complexity, and the cost and yield need to be improved, this invention provides a single-chip triaxial magnetic field sensor based on a single wafer growth process using the same thin film single etching process.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution: According to one aspect of an embodiment of the present invention, a single-chip triaxial magnetic field sensor is provided, comprising:

[0005] Substrate, which is used to provide support for other devices;

[0006] A magnetically sensitive thin film array, wherein at least three sets of the magnetically sensitive thin film array are disposed above the substrate, and the magnetically sensitive thin film array is sensitive to magnetic fields in a single in-plane direction, and an insulating protective layer is covered above the magnetically sensitive thin film array;

[0007] Each set of magnetically sensitive thin film arrays is connected to a corresponding fixed resistor module to form a Wheatstone bridge structure.

[0008] A magnetic flux controller is provided, wherein each group of magnetically sensitive thin film arrays is connected to a corresponding magnetic flux controller with a different thickness, and the magnetic flux controller is positioned above the magnetically sensitive thin film array.

[0009] Optionally, the magnetically sensitive thin film array includes multiple magnetically sensitive structural units of the same size, all of which are sensitive to magnetic fields in a single in-plane direction.

[0010] Optionally, the magnetically sensitive structural unit is a tunneling magnetoresistive thin film device, a giant magnetoresistive thin film device, or an anisotropic magnetoresistive thin film device, which are connected in series and parallel to form an array, with the sensitive axis of the array perpendicular to the long axis of the magnetically sensitive structural unit.

[0011] Optionally, the fixed resistor module and the magnetically sensitive thin film array are located on the same horizontal plane.

[0012] Optionally, the long end of the magnetically sensitive thin film array and the long end of the magnetic flux controller have a fixed angle of 10 to 80°.

[0013] Optionally, the magnetic flux controller is made of a material with high magnetic permeability.

[0014] Optionally, each magnetically sensitive thin film array is connected in series and parallel with a fixed resistor module to form a Wheatstone bridge structure. The voltage input terminals of each Wheatstone bridge structure are connected in parallel with each other, and the output terminals are independent of each other.

[0015] Optionally, the voltage signals U1, U2, U3, ..., Un of the output of each Wheatstone bridge structure are measured respectively, and the expression is Un=Nnx×Hx+Nny×Hy+Nnz×Hz; where Nnx, Nny, and Nnz are the sensitivity coefficients of the sensitive element to the triaxial magnetic fields Hx, Hy, and Hz respectively.

[0016] Optionally, each magnetic sensitive thin film array has different measurement sensitivity and measurement range for triaxial magnetic fields, and each magnetic sensitive thin film array can be used as a single-axis sensor to measure magnetic fields in different ranges.

[0017] According to another aspect of the present invention, a method for fabricating a single-chip triaxial magnetic field sensor is also provided, comprising:

[0018] Growing magnetically sensitive thin films on a substrate;

[0019] Magnetic sensitive thin film array structures and wires were fabricated using photolithography.

[0020] An insulating protective layer and a seed layer in front of the electroplated magnetic flux concentrator are prepared above the thin film array;

[0021] Electroplating magnetic flux concentrator layers onto the seed layer, and sequentially completing the corresponding magnetic flux controller layers from thin to thick.

[0022] Compared with existing technologies, the present invention has the following advantages:

[0023] 1. The single-chip triaxial magnetic field sensor provided by the present invention only requires thin film growth and etching on a single wafer / substrate from start to finish. Because the thin film process is completely the same as that of the wafer, it is beneficial to improve the yield and avoid the impact of differences in thin film growth on different wafers.

[0024] 2. The single-chip triaxial magnetic field sensor flux controller provided by this invention has the same shape, differing only in thickness, greatly reducing manufacturing complexity. The fixed resistor module has no manufacturing difficulty and does not increase process complexity. Only one die removal and cutting operation is required, avoiding errors caused by changes in relative positions due to die removal and pasting of multiple sensor arrays.

[0025] 3. The single-chip triaxial magnetic field sensor provided by this invention obtains the magnitude of the triaxial magnetic field by solving a simple set of equations, taking into account the influence of the magnetic field of each axis. Compared with the method of measuring the magnetic field magnitude of each axis separately, it avoids the interference of magnetic field in non-sensitive axis directions on chip measurement. Moreover, the formula is simple and convenient to use data fusion methods such as machine learning to obtain more accurate detection data. Attached Figure Description

[0026] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a top view of a single-chip triaxial magnetic field sensor according to an embodiment of the present invention;

[0028] Figure 2 This is a side view of a single-chip triaxial magnetic field sensor according to an embodiment of the present invention;

[0029] Among them, 101 is the substrate; 102 is the magnetically sensitive thin film array; 103 is the magnetic flux controller; 104 is the fixed resistor module; 105 is the wire; and 106 is the insulating protective layer.

[0030] Figure 3 This refers to the magnitude of the magnetic field induced on the surface of a single-chip triaxial magnetic field sensor according to an embodiment of the present invention when an X-direction magnetic field is applied;

[0031] Figure 4 This is a flowchart of a method for fabricating a single-chip triaxial magnetic field sensor according to an embodiment of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0033] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. Where the terms "first," "second," and "third" are used for descriptive purposes and to distinguish technical features, they should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The embodiments of this invention will now be described according to its overall structure.

[0035] like Figure 1 As shown, 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 resistor module 104, a wire 105, and an insulating protective layer 106. Figure 1 In this configuration, the entire magnetic field sensor is located in the XY plane, with the Z-axis perpendicular to it.

[0036] The single-chip triaxial magnetic field sensor consists of at least three magnetically sensitive thin film arrays and corresponding magnetic flux controllers with different thicknesses. Additionally, a fixed resistor module and the arrays form a Wheatstone bridge structure.

[0037] Specifically, substrate 101 is used to provide support for other devices.

[0038] The magnetic sensitive thin film array 102 includes multiple magnetic sensitive structural units of the same size. The magnetic sensitive structural units of the same size are connected in sequence to form a loop. The magnetic sensitive thin film array 102 is disposed on the substrate 101 and has sensitive characteristics to magnetic fields in a single direction on one side (front or back). In addition, an insulating protective layer 106 covers the magnetic sensitive thin film array 102.

[0039] The magnetic flux controller 103 is a long strip structure located above the magnetically sensitive thin film array 102. The magnetic flux controller 103 is made of a material with high magnetic permeability. In this embodiment, a magnetic flux controller 103 with a different thickness is provided above each magnetically sensitive unit.

[0040] The fixed resistor module 104 is connected to the magnetically sensitive thin film array 102 to form a Wheatstone bridge structure.

[0041] Figure 1 The thin black lines in the middle are conductive films or wires. In this embodiment, wire 105 is used to connect the magnetic sensitive thin film array 102, and the magnetic sensitive thin film array 102 is connected to the fixed resistor module 104 to form a bridge structure.

[0042] As an optional embodiment, each magnetically sensitive thin film array 102 is connected to two fixed resistors. Taking one magnetically sensitive thin film array 102 as an example, the magnetically sensitive structural unit of one magnetically sensitive thin film array 102 and the 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 of equal or similar number.

[0043] In this module, the resistance of each fixed resistor is equal to the resistance of the magnetically sensitive thin-film array 102 when the magnetic field is zero; for example... Figure 1 As shown, a fixed resistor and a magnetically sensitive thin film array 102 are connected to form a Wheatstone bridge structure. The input voltage is Uin, the resistance of the fixed resistor is R, and the resistance change of the magnetically sensitive thin film array 102 under the magnetic field is ΔR. Then the voltage signal output by the Wheatstone bridge is U = ΔR / 2(R+ΔR)×Uin.

[0044] Specifically, the magnetically sensitive thin film array 102 is a tunneling magnetoresistive thin film device, a giant magnetoresistive thin film device, or an anisotropic magnetoresistive thin film device, which is connected in series and parallel to form an array, and its sensitive axis direction is perpendicular to the long axis direction of the magnetically sensitive structural unit. Figure 1 V+ and V- are the inputs of the voltage source, and Vout+ and Vout- are the positive and negative terminals of the sensor's output voltage. Each magnetically sensitive thin-film array 102 has an independent output terminal.

[0045] Specifically, the sensitive unit in the magnetically sensitive thin film array 102 is shaped like a long rectangle or an ellipse, and the magnetic flux controller is a long rectangle; the long end of the magnetically sensitive thin film array 102 and the long end of the magnetic flux controller 103 have a fixed angle of 10° to 80°. In one embodiment, the long end of the magnetically sensitive thin film array 102 and the long end of the magnetic flux controller 103 have a fixed angle of 45°.

[0046] like Figure 2 As shown, the single-chip triaxial magnetic field sensor also includes an insulating protective layer 106 disposed above the magnetically sensitive thin film array 102. The magnetic flux controller 103 above each magnetically sensitive thin film array 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. Due to the different thicknesses of the magnetic flux controllers, the degree of change in magnetic flux near the magnetically sensitive thin film array 102 also varies. The expression for the voltage signals U1, U2, U3, ..., Un output by each bridge is Un = Nnx × Hx + Nny × Hy + Nnz × Hz; where Nnx, Nny, and Nnz are the sensitivity coefficients of the sensitive unit to the triaxial magnetic fields Hx, Hy, and Hz, respectively. The magnitude of the triaxial magnetic field can be obtained by solving the system of simultaneous equations.

[0047] Figure 3 This diagram illustrates the ratio of the magnetic flux density in the X-direction near the magnetic sensing unit below magnetic flux controllers of different thicknesses to the magnetic flux density in the surrounding air. Figure 3 As shown, taking the X-axis magnetic field as an example, the results for the Y-axis and Z-axis magnetic fields are similar. When the magnetic field direction is in-plane X-direction, the ratio of the X-direction component of the magnetic flux density near the magnetic sensing unit below the magnetic flux controller of different thicknesses to the magnetic flux density in the surrounding air was calculated. It can be clearly seen that the magnetic flux controller of different thicknesses controls the X-direction component of the magnetic field magnitude. The sensing axis of the magnetic sensing unit has a certain angle with the X-axis direction. When the thickness of the magnetic flux controller above it is different, the component of the magnetic flux density above the magnetic sensing unit in the sensing axis direction changes, thus its output will be different. Therefore, given the sensitivity coefficient of the magnetic sensing unit to the triaxial magnetic field, the magnitude of the triaxial magnetic field can be obtained by solving the equations using multiple sets of data.

[0048] Figure 4 The diagram illustrates a method for fabricating a single-chip triaxial magnetic field sensor, including:

[0049] Step S1: Grow a magnetically sensitive thin film on the substrate;

[0050] Step S2: Fabricate the magnetically sensitive thin film array structure and wires using photolithography.

[0051] Step S3: Prepare an insulating protective layer and a seed layer in front of the electroplated magnetic flux concentrator above the thin film array;

[0052] Step S4: Electroplating a magnetic flux concentrator layer on the seed layer, and then sequentially completing the thinner and thicker magnetic flux controller layers.

[0053] The single-chip triaxial magnetic field sensor of the present invention can be prepared by the above preparation method.

[0054] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A single-chip triaxial magnetic field sensor, characterized in that, include: Substrate, which is used to provide support for other devices; A magnetically sensitive thin film array, wherein at least three sets of the magnetically sensitive thin film array are disposed above the substrate, and the magnetically sensitive thin film array is sensitive to magnetic fields in a single in-plane direction, and an insulating protective layer is covered above the magnetically sensitive thin film array; Each set of magnetically sensitive thin film arrays is connected to a corresponding fixed resistor module to form a Wheatstone bridge structure. A magnetic flux controller is provided, wherein each group of magnetically sensitive thin film arrays is connected to a corresponding magnetic flux controller with a different thickness, and the magnetic flux controller is positioned above the magnetically sensitive thin film array.

2. The single-chip triaxial magnetic field sensor according to claim 1, characterized in that, The magnetically sensitive thin film array includes multiple magnetically sensitive structural units of the same size, and all magnetically sensitive structural units are sensitive to magnetic fields in a single in-plane direction.

3. The single-chip triaxial magnetic field sensor according to claim 2, characterized in that, The magnetically sensitive structural unit is a tunneling magnetoresistive thin film device, a giant magnetoresistive thin film device, or an anisotropic magnetoresistive thin film device, which is connected in series and parallel to form an array. The sensitive axis of the array is perpendicular to the long axis of the magnetically sensitive structural unit.

4. The single-chip triaxial magnetic field sensor according to claim 1, characterized in that, The fixed resistor module and the magnetically sensitive thin film array are located on the same horizontal plane.

5. The single-chip triaxial magnetic field sensor according to claim 1, characterized in that, 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 triaxial magnetic field sensor according to claim 1, characterized in that, The magnetic flux controller is made of a material with high magnetic permeability.

7. The single-chip triaxial magnetic field sensor according to claim 1, characterized in that, Each magnetically sensitive thin-film array forms a Wheatstone bridge structure by being connected in series and parallel with a fixed resistor module. The voltage input terminals of each Wheatstone bridge structure are connected in parallel with each other, while the output terminals are independent of each other.

8. The single-chip triaxial magnetic field sensor according to claim 7, characterized in that, The voltage signals U1, U2, U3, ..., Un of the output of each Wheatstone bridge structure are measured respectively, and the expression is Un = Nnx × Hx + Nny × Hy + Nnz × Hz; where Nnx, Nny, and Nnz are the sensitivity coefficients of the sensitive element to the triaxial magnetic fields Hx, Hy, and Hz respectively.

9. The single-chip triaxial magnetic field sensor according to claim 1, characterized in that, Each magnetic sensitive thin film array has different measurement sensitivity and measurement range for triaxial magnetic fields. Each magnetic sensitive thin film array can be used as a single-axis sensor to measure magnetic fields in different ranges.

10. A method for fabricating a single-chip triaxial magnetic field sensor, characterized in that, include: Growing magnetically sensitive thin films on a substrate; Magnetic sensitive thin film array structures and wires were fabricated using photolithography. An insulating protective layer and a seed layer in front of the electroplated magnetic flux concentrator are prepared above the thin film array; Electroplating magnetic flux concentrator layers onto the seed layer, and sequentially completing the corresponding magnetic flux controller layers from thin to thick.

Images