CN108107383A - A kind of linear anisotropic magnetoresistive sensor and preparation method thereof - Google Patents

Abstract

The invention belongs to magnetic materials and component technical field, are specially a kind of linear anisotropic magnetoresistive sensor and preparation method thereof.The present invention will mutual disconnected N number of parallelogram magnetoresistive strip, mutual disconnected N 1~N+1 parallelogram conductive layers, being tiled in a manner of intermeshing is arranged at same level on substrate, and magnetoresistive strip passes through embedded conductive layer and realizes electric connection；This makes the current direction of all reluctance parts identical and clear, hence it is evident that reduces the noise of output electric signal；The conductive layer being embedded in magnetoresistive strip need not realize the effect of change current direction with thickness, reduce the thickness of entire device, improve structural stability.It is thinner less with output signal noise to realize conductive layer on the premise of current offset effect is ensured by the final present invention.

Description

A linear anisotropic magnetoresistive sensor and its preparation method

technical field

The invention belongs to the technical field of magnetic materials and components, in particular to a linear anisotropic magnetoresistance sensor and a preparation method thereof.

Background technique

Anisotropic magnetoresistance effect (AMR, Anisotropic Magnetoresistance) means that in magnetic materials (such as NiFe, CoFe, Co, etc.), when the angle between the magnetic moment of the magnetic material and the current changes, the resistance of the material also changes. The phenomenon. The size R of the anisotropic magnetoresistance satisfies: R=R ₀ +ΔRcos2θ, wherein, R ₀ is the resistance value under zero magnetic field; ΔR is the maximum change value of the anisotropic magnetoresistance; θ is the relationship between the current direction and the magnetization direction of the magnetic layer angle. The linear anisotropic magnetoresistive sensor is based on the anisotropic magnetoresistance effect. Under specific preparation conditions, the orientation of the magnetic moment of the magnetic material changes linearly with the magnitude of the external magnetic field. The linear change of the included angle realizes the measurement of the magnitude of the magnetic field. The structure of the linear anisotropic magnetoresistive sensor is simple, the preparation process is not complicated, and the cost is low. It is an important member of the current magnetic sensor family.

Linear anisotropic magnetoresistive sensors generally use strip-shaped magnetic materials. During the preparation process, the magnetic moments of the materials are arranged along the long axis direction. During the test, a current is applied in the long axis direction and an external magnetic field is applied in the short axis direction. changes in the external magnetic field. When there is no current bias, the change of reluctance with external magnetic field is nonlinear around zero. At present, the magnetoresistive strips are usually deposited in the shape of a Wheatstone bridge, and then a conductive layer is deposited on the magnetoresistive strips to guide the current on the magnetoresistive strips to a certain angle, so that the angle θ between the current direction and the magnetization direction has An initial value, usually 30° to 60°, makes the resistance change of the magnetoresistive strip output linearly near the zero magnetic field, realizing the function of a linear anisotropic magnetoresistive sensor. Its structure is shown in Figure 1 and Figure 2.

However, the conductive layer deposited on the magnetoresistive strip needs to have a sufficient thickness, generally 200nm or more, in order to have a good current bias effect. However, when the conductive layer is thicker, the adhesion between the conductive layer and the magnetoresistive strip is relatively low, and it is easy to fall off, and the internal stress of the conductive layer is relatively large. When the sensor is annealed, the thicker conductive layer is more prone to deformation and the shape is uncontrollable. On the other hand, when the sensor is working, the current flowing in the magnetoresistive strip without a conductive layer on the surface is biased in the designed direction, but the current in the magnetoresistive strip with a conductive layer on the surface is not biased in the designed direction, The directions of the currents in the two parts of the magnetoresistive strips are inconsistent, thereby reducing the linearity of the sensor output signal changing with the magnetic field and increasing the noise of the output signal.

To sum up, the linear anisotropic magnetoresistive sensor realizes the current bias through the way that the conductive layer is above the magnetoresistive strip, but there are problems such as thick conductive layer film and noise in the output signal. Therefore, if we can start with the process and structure of the conductive layer for preparing the linear anisotropic magnetoresistive sensor, we can provide a method with a thinner conductive layer, a more stable structure, a clearer current bias effect, and less noise in the output signal. It will be beneficial to the development and application field of the linear anisotropic magnetoresistive sensor.

Contents of the invention

In view of the above existing problems or deficiencies, in order to realize the technical problems of the linear anisotropic magnetoresistive sensor under the premise of ensuring the current bias effect, the conductive layer is thinner and the output signal noise is less; the present invention provides a linear anisotropic magnetoresistive sensor. Magnetoresistive sensor and its preparation method. The present invention adopts the method of embedding the conductive layer into the magnetoresistive strips to realize the current bias; the design of the magnetoresistance part is as shown in Figure 3, and the conductive layer is arranged between the intermittent magnetoresistive strips (the schematic diagram of the structure is shown in Figure 4), to achieve The purpose of reducing the thickness of the conductive layer, improving the current bias efficiency, and reducing the noise of the sensor output signal.

The linear anisotropic magnetoresistance sensor includes: a substrate, a conductive layer and a magnetoresistance strip.

The substrate is used to carry the conductive layer and the magnetoresistive strips, and is non-conductive.

The magnetic resistance strips are N parallelograms that are not connected to each other, the conductive layer is N-1 to N+1 parallelograms that are not connected to each other, and the magnetic resistance strips and the conductive layer are arranged on the same horizontal plane on the substrate in an interlaced manner. The magnetoresistive strips are electrically connected through the embedded conductive layer, N≥3.

Further, N+1 conductive layers are selected, that is, the conductive layers arranged in a staggered and tiled manner and both ends of the magnetoresistance are conductive layers.

Further, it also includes a protective layer covering the surfaces of the conductive layer and the magnetoresistive strips.

Its preparation method comprises the following steps:

Step 1: Exposing N discontinuous parallelogram magnetoresistive strip patterns on the insulating substrate by using a photolithography process.

Step 2: Depositing magnetoresistive strips on the substrate treated in step 1 by using a magnetron sputtering process.

Step 3: Filling N-1 to N+1 parallelogram conductive layers at the positions of the non-magnetoresistive strips of the substrate after the treatment in step 2, and electrically connecting adjacent magnetoresistive strips through the conductive layers.

Further, after the treatment in step 3, the upper surface of the substrate is plated with a protective layer for protecting the magnetoresistive layer and the conductive layer.

In the present invention, the conductive layer of the bias current is made between the magnetoresistive strips in an embedded manner, so that the current directions of all the magnetoresistance parts are the same and clear, and the noise of the output electrical signal is obviously reduced; the direction of the current moving in the magnetoresistance part is perpendicular to The interface between the conductive layer and the magnetoresistive part realizes the current biasing effect. The conductive layer embedded in the magneto-resistive strips does not need a large thickness to achieve the function of changing the direction of the current. It only needs to maintain the electrical connection between the magneto-resistive strips to clearly and accurately change the direction of the current. Therefore, the thickness of the conductive layer has no requirements, thereby greatly reducing the thickness of the entire device and improving structural stability. When the sensor is working, all the current passes through the magnetoresistive part in a preset direction, and passes through the conductive layer in a preset direction. The current direction is clear and independent of each other, reducing signal noise and improving sensor test performance.

In summary, the present invention achieves a thinner conductive layer and less noise in the output signal under the premise of ensuring the current bias effect.

Description of drawings

FIG. 1 is a schematic cross-sectional view of an existing linear anisotropic magnetoresistive sensor;

2 is a schematic top view of an existing linear anisotropic magnetoresistive sensor;

Fig. 3 is the schematic structural diagram of the discontinuous magnetoresistive strip of the embodiment;

Fig. 4 is a schematic diagram of the structure of the magnetoresistive strip after the conductive layer is embedded in the embodiment;

Fig. 5 is the schematic cross-sectional view of the linear anisotropic magnetoresistive sensor prepared by the embodiment;

Fig. 6 is a schematic diagram of the movement of current on the magnetoresistive strip and the conductive layer in the embodiment;

Fig. 7 is a diagram showing the variation of the output voltage of the sensor with the magnetic field in the embodiment.

Detailed ways

The technical scheme of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Step 1: On the silicon substrate, a pattern of elongated magnetoresistive strips with a total length of 7.2um and discontinuous strips is exposed by a photolithography process, each magnetoresistive strip has a width of 5nm and a gap of 5nm.

Step 2: Deposit 5nmTa, 12nmNiFe and 2nmTa in sequence on the substrate treated in step 1 by magnetron sputtering process. Then it is soaked in the glue removing solution, and after the photoresist is removed, the sample is taken out to obtain discontinuous elongated magnetoresistive strips.

Step 3: On the substrate processed in step 2, a 20nm Al conductive layer is filled at the position of the non-magnetoresistive strips by using a photolithography process and an electron beam evaporation process, and the magnetoresistive strips are electrically connected through the conductive layer. The Al conductive layer deposited in this step can also be used for the electrode part in the linear anisotropic magnetoresistive sensor unit.

Step 4: coat the upper surface of the substrate after step ₃ with a protective layer of SiO to protect the mechanical stability and oxidation resistance of the magnetoresistive layer and the conductive layer, etc., to obtain the linear anisotropic magnetoresistive sensor, and its cross-section is schematic As shown in Figure 5.

Use the software COMSOL to simulate the movement of the current on the magnetoresistive strip and the conductive layer in this embodiment. The direction of the arrow indicates the current direction at this point. It can be seen that the current direction on the magnetoresistive strip is perpendicular to the interface between the conductive layer and the magnetoresistive strip, and the bias effect is well realized, as shown in Figure 6;

The test results of the linear anisotropic magnetoresistive sensor prepared in this embodiment are shown in FIG. 7 . It can be seen that within the magnetic field range of ±10Oe, the output signal of the sensor has a good linear relationship, and the function of the linear anisotropic magnetoresistive sensor is well realized.

Claims (5)

1. A linear anisotropic magnetoresistive sensor comprises substrate, conductive layer and magnetoresistive strip, is characterized in that: The substrate is used to carry the conductive layer and the magnetoresistive strip, and is not conductive; The magnetic resistance strips are N parallelograms that are not connected to each other, the conductive layer is N-1 to N+1 parallelograms that are not connected to each other, and the magnetic resistance strips and the conductive layer are arranged on the same horizontal plane on the substrate in an interlaced manner. The magnetoresistive strips are electrically connected through the embedded conductive layer, N≥3. 2. The linear anisotropic magnetoresistive sensor as claimed in claim 1, characterized in that: the conductive layer is selected from N+1, that is, the conductive layer and the two ends of the magnetoresistance that are arranged in a staggered manner are all conductive layers. . 3. The linear anisotropic magnetoresistive sensor according to claim 1, further comprising a protective layer covering the surface of the conductive layer and the magnetoresistive strip. 4. the preparation method of linear anisotropic magnetoresistive sensor as claimed in claim 1, comprises the following steps: Step 1, exposing intermittent N parallelogram magnetoresistive strip patterns on the insulating substrate by photolithography; Step 2. Depositing magnetoresistive strips by magnetron sputtering on the substrate treated in step 1; Step 3, filling N-1 to N+1 parallelogram conductive layers at the position of the non-magnetoresistive strips of the substrate after the treatment in step 2, and electrically connecting adjacent magnetoresistive strips through the conductive layers. 5. The preparation method of the linear anisotropic magnetoresistive sensor according to claim 4, characterized in that: after the treatment in step 3, the upper surface of the substrate is coated with a protective layer for protecting the magnetoresistance layer and the conductive layer.