CN116106800A - A single-chip three-axis magnetic field sensor and its preparation method - 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

A single-chip three-axis magnetic field sensor and its preparation method

technical field

The invention belongs to the technical field of magnetic sensors, in particular to a single-chip three-axis magnetic field sensor and a preparation method thereof.

Background technique

The miniaturized and integrated three-axis magnetic field sensor can accurately feed back the magnetic field signal in three-dimensional space, which is expected to further improve the measurement accuracy and precision of the magnetic sensor, and at the same time realize the functions of scanning the magnetic field signal in space, and is widely used in power grids, energy management, new energy Automotive, industrial manufacturing and many other fields. At present, domestic and foreign manufacturers including Jiangsu Multidimensional and TDK of Japan have launched three-axis magnetic field sensors. However, limited by the process conditions, the existing three-axis magnetic field sensor requires the splicing combination of multiple single-axis magnetic sensitive chips with different sensitive axes, which requires the growth of three different magnetic field sensors on at least 2~3 wafers. Sensitive films are etched separately and then spliced, which increases the risk of cost and film uniformity and yield.

Contents of the invention

Aiming at the current situation that traditional three-axis magnetic field sensors in the prior art require multiple TMR chips to be spliced, the process complexity is high, and the cost and yield rate need to be upgraded, the present invention provides a single etching process for the same thin film based on single wafer growth. A single-chip three-axis magnetic field sensor.

The present invention solves the above-mentioned technical problems through the following technical solutions. According to one aspect of the embodiments of the present invention, a single-chip three-axis magnetic field sensor is provided, including:

a substrate, which is used to provide support for other devices;

A magnetically sensitive thin film array, at least three sets of the magnetically sensitive thin film arrays are arranged above the substrate, and are sensitive to a single in-plane direction magnetic field, and the upper side of the magnetically sensitive thin film array is covered with an insulating protective layer;

A fixed-value resistor module, each group of magnetically sensitive film arrays is connected to a corresponding fixed-value resistor module to form a Wheatstone bridge structure;

A magnetic flux controller, each group of the magnetically sensitive thin film arrays is connected to a corresponding magnetic flux controller with different thicknesses, and the magnetic flux controller is arranged above the magnetically sensitive thin film array.

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

Optionally, the magnetically sensitive structural unit is a tunneling magnetoresistance thin film device or a giant magnetoresistance thin film device or an anisotropic magnetoresistance thin film device, and an array is formed by connecting in series and parallel, and the direction of the sensitive axis of the array is perpendicular to the direction of the magnetically sensitive structural unit. long axis direction.

Optionally, the fixed-value resistor module and the magnetically sensitive film array are located on the same level.

Optionally, there is a fixed angle of 10-80° between the long end of the magnetically sensitive film array and the long end of the magnetic flux controller.

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

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

Optionally, measure the output voltage signals U1, U2, U3,..., Un of the Wheatstone bridge structure respectively, and the expression is Un=Nnx×Hx+Nny×Hy+Nnz×Hz; where, Nnx, Nny, Nnz is the sensitivity coefficient of the sensitive unit to the three-axis magnetic field Hx, Hy, Hz respectively.

Optionally, each group of magnetically sensitive thin film arrays has different measurement sensitivities and measurement ranges for the triaxial magnetic field, and each group of magnetically sensitive thin film arrays can be used as a single-axis sensor to respectively realize the measurement of magnetic fields in different ranges.

According to another aspect of the embodiments of the present invention, a method for preparing a single-chip three-axis magnetic field sensor is also provided, including:

growing a magnetically sensitive thin film on the substrate;

Prepare the magnetically sensitive thin film array structure and wires by photolithography;

Preparing an insulating protective layer and a seed layer before electroplating a magnetic flux concentrator above the thin film array;

The magnetic flux concentrator layer is electroplated on the seed layer, and the corresponding magnetic flux controller layers are completed sequentially from thin to thick.

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

1. The single-chip three-axis magnetic field sensor provided by the present invention only needs to perform thin film growth and etching on one wafer/substrate from the beginning to the end, and because the thin film process is completely the same as the wafer, it is beneficial to improve the yield rate. Avoid the impact of differences in the growth of films on different wafers.

2. The shapes of the magnetic flux controllers of the single-chip three-axis magnetic field sensor provided by the present invention are also exactly the same, and only the thickness is different, which greatly reduces the complexity of the process. The fixed-value resistor module has no process difficulty and will not increase the complexity of the process. Only one operation of die removal and cutting is required to avoid errors caused by changes in relative positions caused by die removal and pasting of multiple sensor arrays.

3. The single-chip three-axis magnetic field sensor provided by the present invention obtains the size of the three-axis magnetic field by solving simple equations, taking into account the influence of the magnetic field of each axis; compared to the method of separately measuring the magnetic field size of each axis , which avoids the interference of non-sensitive axial magnetic fields on chip measurement; and the formula is simple, and it is convenient to use data fusion methods such as machine learning to obtain more accurate detection data.

Description of drawings

In order to illustrate the technical solution of the present invention more clearly, the accompanying drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only an embodiment of the present invention. Ordinary technicians can also obtain other drawings based on these drawings without paying creative work.

1 is a top view of a single-chip three-axis magnetic field sensor according to an embodiment of the present invention;

2 is a side view of a single-chip three-axis magnetic field sensor according to an embodiment of the present invention;

Among them, 101, substrate; 102, magnetically sensitive film array; 103, magnetic flux controller; 104, fixed-value resistor module; 105, wire; 106, insulating protective layer;

Fig. 3 shows the magnitude of the magnetic field induced on the surface of the single-chip three-axis magnetic field sensor according to an embodiment of the present invention when a magnetic field in the X direction is applied;

Fig. 4 is a flowchart of a method for manufacturing a single-chip three-axis magnetic field sensor according to an embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiment of the application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the application. Obviously, the described embodiment is only It is an embodiment of a part of the application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

In the description of the present invention, several means one or more, and multiple means more than two. Greater than, less than, exceeding, etc. are understood as not including the original number, and above, below, within, etc. are understood as including the original number. If the terms "first", "second", and "third" are described, they are only used for the purpose of describing and distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the indicated technical features The quantity or implicitly indicate the sequence relationship of the indicated technical features.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", "connection" and "setting" should be understood in a broad sense, for example, it can be a fixed connection, or It can be a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations. The embodiments of the present invention will be described below according to the overall structure of the present invention.

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

The single-chip three-axis magnetic field sensor consists of at least three sets of magnetically sensitive film arrays and corresponding magnetic flux controllers with different thicknesses, and a Wheatstone bridge structure composed of fixed-value resistance modules and arrays.

Specifically, 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 of the same size, and the magnetically sensitive structural units of the same size are connected in sequence to form a loop, and the magnetically sensitive thin film array 102 is arranged on the substrate 101, for a single surface (front or back) ) is sensitive to the magnetic field in the inner direction. In addition, the magnetically sensitive film array 102 is covered with an insulating protective layer 106 .

The magnetic flux controller 103 has a strip structure and is located on 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 with different thicknesses is disposed above each magnetic sensitive unit.

The fixed-value resistor module 104 is connected with the magnetically sensitive film array 102 to form a Wheatstone bridge structure.

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

As an optional embodiment, each magnetically sensitive film array 102 is connected with two fixed value resistors. Taking a magnetically sensitive thin film array 102 as an example, the magnetically sensitive structural unit of a magnetically sensitive thin film array 102 forms a series loop with two fixed value resistors, wherein the two fixed value resistors connect the magnetically sensitive structural unit in the series loop Divide into two parts of equal or close number.

Wherein, the resistance of each block of the fixed value resistor module is equal to the resistance value of the magnetically sensitive film array 102 when the magnetic field is 0; as shown in Figure 1, the fixed value resistor and the magnetically sensitive film array 102 are connected to form a Wheatstone bridge structure, input The voltage is Uin, the resistance value of the fixed-value resistor is R, and the resistance change of the magnetic sensitive film array 102 under the magnetic field is △R, then the voltage signal U=△R/2(R+△R)×Uin output by the Wheatstone bridge .

Specifically, the magnetically sensitive thin film array 102 is a tunneling magnetoresistive thin film device or a giant magnetoresistive thin film device or an anisotropic magnetoresistive thin film device. The array is formed by connecting in series and parallel, and the direction of the sensitive axis is perpendicular to the long axis direction of the magnetically sensitive structural unit. . In Figure 1, V+ and V- are the input of the voltage source, and Vout+ and Vout- are the positive and negative terminals of the output voltage of the sensor. Each set of magnetically sensitive film arrays 102 has an independent output terminal

Specifically, the shape of the sensitive unit in the magnetically sensitive film array 102 is a long rectangle or an ellipse, and the magnetic flux controller is a long rectangle; Fixed angle. In one of the embodiments, there is a fixed angle of 45° between the long end of the magnetically sensitive film array 102 and the long end of the magnetic flux controller 103

As shown in FIG. 2 , the single-chip three-axis magnetic field sensor further includes an insulating protection layer 106 disposed above the magnetically sensitive film array 102 . The magnetic flux controllers 103 above each group of magnetically sensitive film arrays 102 have different thicknesses. Specifically, the magnetic flux controller 103 has a thickness of 1-50 μm, and the magnetically sensitive film array 102 has a thickness of 0.5-2 μm. Due to the different thicknesses of the magnetic flux control, the degrees of changes to the magnetic flux near the magnetically sensitive thin film array 102 are also different. The expression of the voltage signal U1, U2, U3,..., Un output by each bridge is Un=Nnx×Hx+ Nny×Hy+ Nnz×Hz; where Nnx, Nny, Nnz are the three-axis magnetic field Hx, Hy, the gage factor in Hz. The magnitude of the three-axis magnetic field can be obtained by solving the simultaneous equations.

Figure 3 is a schematic diagram of the ratio of the magnetic flux density in the X direction component near the magnetic sensitive unit under the magnetic flux controller with different thicknesses to the magnetic flux density in the outside air. As shown in Figure 3, taking the X-axis magnetic field as an example, the Y-axis and Z-axis magnetic fields The results are similar; when the magnetic field direction is the in-plane X direction, the ratio of the magnetic flux density in the X direction component near the magnetic sensitive unit under the magnetic flux controller with different thicknesses to the magnetic flux density at the outside air is calculated, and it can be clearly seen that different thicknesses The magnetic flux controller controls the component of the magnetic field in the X-axis direction. There is a certain angle between the direction of the sensitive axis of the magnetic sensitive unit and the direction of the X axis. When the thickness of the upper magnetic flux controller is different, the component of the magnetic flux density above the magnetic sensitive unit in the direction of the sensitive axis changes, so its output will be different. Therefore, the sensitivity coefficient of the magnetic sensitive unit to the three-axis magnetic field is known, and the magnitude of the three-axis magnetic field can be obtained by solving equations with multiple sets of data.

Figure 4 shows the preparation method of a single-chip three-axis magnetic field sensor, including:

Step S1, growing a magnetically sensitive thin film on the substrate;

Step S2, preparing a magnetically sensitive thin film array structure and wires through a photolithography process;

Step S3, preparing an insulating protective layer and a seed layer before electroplating the magnetic flux concentrator on the thin film array;

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

Through the above preparation method, the single-chip three-axis magnetic field sensor of the present invention can be prepared.

What is disclosed above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention. Should be covered within the protection 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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