CN109752677A - A double bridge type thin film magnetoresistive sensor - Google Patents

Abstract

The invention discloses a double-bridge type thin-film magnetoresistive sensor. The anisotropic magnetoresistive layer is composed of four identical anisotropic magnetoresistive thin-film strips A, B, C, and D which are connected head-to-tail in sequence to form a bridge. Another group of four identical anisotropic magnetoresistive thin film strips A', B', C', D' are connected head-to-tail in sequence to form another electric bridge, and the two electric bridges are connected in parallel to form the double-bridge type thin-film magnetic strip. Resistance sensor; wherein, the phases of the magnetoresistive film strips A, B, C, and D are different by 90°, the arrangement of the magnetoresistive film strips A'B'C'D' is the same as that of the magnetoresistive film strips ABCD, and the magnetoresistive film strips A ', B', C', and D' are all applied with Barber electrodes at an angle of 45° with the long axis direction of the magnetoresistive film (as shown in the abstract figure). The structure of the thin film magnetoresistive sensor is novel, and the magnetoresistive sensor is designed in the form of a double bridge for the first time, which expands the linear working area of the magnetoresistive sensor and improves the sensitivity.

Description

A double bridge type thin film magnetoresistive sensor

technical field

The invention belongs to the technical field of magnetic sensors, and in particular relates to a double bridge type thin film magnetoresistive sensor for measuring the direction of a magnetic field.

Background technique

When some metals or semiconductors encounter an external magnetic field, their resistance value will change with the magnitude of the external magnetic field. This phenomenon is called the magnetoresistive effect. The magnetoresistive sensor is made of the magnetoresistive effect. In 1857, Thomson discovered the anisotropic magnetoresistance effect of permalloy. For ferromagnetic metals with anisotropic properties, the change of magnetoresistance is related to the angle between the magnetic field and the current. When the external magnetic field and the built-in magnetic field of the magnet form a zero-degree angle, the resistance will not change with the change of the external magnetic field; but when the external magnetic field and the built-in magnetic field of the magnet have a certain angle, the internal magnetization vector of the magnet will be offset. shift, the sheet resistance decreases, this characteristic is called the anisotropic magnetoresistance effect

The anisotropic thin-film magnetoresistive sensor is a new type of magnetic sensor that appeared in the mid-1970s. Due to its advantages of high sensitivity, small size, high reliability, good temperature characteristics, strong ability to withstand harsh environments, and easy matching with digital circuits, it has continuously expanded its application field and replaced many traditional magnetic fields such as Hall devices. market occupied by sensitive devices. However, the anisotropic magnetoresistive sensors currently on the market have a single structure and do not work in the linear region under weak magnetic fields or small-angle magnetic fields. Therefore, it is a hot topic to study a magnetoresistive sensor with a large linear region.

SUMMARY OF THE INVENTION

Technical problem: The technical problem to be solved by the present invention is to provide a double bridge type thin film magnetoresistive sensor, which can realize the measurement of the magnetic field direction, expand the linear working area, and improve the stability of the sensor.

Technical scheme: In order to solve the above technical problems, the technical scheme adopted by a double bridge type thin film magnetoresistive sensor of the present invention is:

The double bridge type thin film magnetoresistive sensor is realized by using Barber electrodes, including the substrate, insulating layer, anisotropic magnetoresistive layer, Barber electrode layer and top electrode layer stacked in sequence from bottom to top; the anisotropic magnetoresistive layer is composed of Four identical anisotropic magnetoresistive thin film strips A, B, C, D are connected in sequence to form a bridge, and another group of four identical anisotropic magnetoresistive thin film strips A', B', C' , D' head and tail are connected in sequence to form another bridge, and the two bridges are connected in parallel to form the double-bridge type thin film magnetoresistive sensor; wherein, the phase difference between the magnetoresistive thin film strip A and the magnetoresistive thin film strip B is 90° , the phase difference between magnetoresistive film strip B and magnetoresistive film strip C is 90°, and the phase difference between magnetoresistive film strip C and magnetoresistive film strip D is 90°. The thin film strips ABCD are the same, and the magnetoresistive thin film strips A', B', C', and D' are all applied with Barber electrodes that form an angle of 45° with the long axis direction of the magnetoresistive thin film.

in,

The four magnetoresistive film strips of the anisotropic magnetoresistive layer with identical anisotropic magnetoresistive effects are selected from iron-nickel alloys with anisotropic magnetoresistive effects.

The content of iron in the iron-nickel alloy is 20%.

The planar shapes of the magnetoresistive thin film strips A, B, C, and D are continuously connected S shapes.

The material used for the substrate is Si.

The insulating layer is made of SiO ₂ , which has non-magnetic properties, good insulating properties, stable chemical properties, high strength and hardness, and good tensile properties.

The material used for the Barber electrode layer is aluminum.

The material used for the top electrode layer is copper.

Barbers are arranged on the magnetoresistive material at an angle of 45° with the long axis (as shown in FIG. 2 ). applied magnetic field It is parallel to the plane of the film, and the included angle with the current direction of the film strip B is θ (as shown in FIG. 2 ). Its equivalent circuit is shown in Figure 3, wherein a, b, c, d, e, f are electrodes made of copper conductive material. A bias voltage V _b is applied to a and f, and the direction of the magnetic field can be converted by measuring the voltage difference between b, c and d, e respectively.

Beneficial effects: The present invention designs a magnetoresistive sensor with a double bridge structure. The two bridges work together to double the linear region, and the sensitivity under weak magnetic field or small-angle magnetic field is greatly improved. .

The double bridge type thin film magnetoresistive sensor for measuring the direction of the magnetic field has the advantages of low power consumption, reliable performance, convenient implementation, etc., and has the benefit of temperature compensation, which makes the measurement more accurate, and also expands the linearity of the magnetoresistive thin film. The working area improves the sensitivity under weak magnetic fields.

Description of drawings

FIG. 1 is a front view of the present invention.

Figure 2 is a plan view of the present invention.

FIG. 3 is an equivalent circuit diagram of the present invention.

There are: substrate 1, insulating layer 2, anisotropic magnetoresistive layer 3, Barber electrode layer 4, top electrode layer 5, anisotropic magnetoresistive film A, B, C, D, A', B', C', D', copper electrodes a, b, c, d, e, f and magnetic field H.

Detailed ways

The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1 to FIG. 3 , a double bridge type thin film magnetoresistive sensor for measuring the direction of the magnetic field of the present invention is shown. It includes a substrate 1 , an oxide layer 2 , an anisotropic magnetoresistive layer 3 , a Barber electrode layer 4 and a top electrode layer 5 that are sequentially stacked from bottom to top. The substrate 1 is Si, the insulating layer 2 is SiO ₂ , the anisotropic magnetoresistive layer 3 is an anisotropic magnetoresistive film NiFe, the Barber electrode 4 is aluminum, and the top electrode 5 is a Cu electrode. The magnetoresistive film strips with the same anisotropic magnetoresistance effect are connected according to the method shown in Figure 2. The phase difference between the magnetoresistive film strips A and B is 90°, and the phase difference between the magnetoresistive film strips B and C is 90°. The phase difference between strips C and D is 90°, and the arrangement of magnetoresistive film strips A'B'C'D' is the same as ABCD, with Barber electrodes added on them. Barber forms an included angle of 45° with the direction of the long axis of the magnetoresistive material (as shown in FIG. 2 ). That is to say, the substrate and the base body are both frame-shaped, and the metal layer is formed by photolithography according to a certain pattern as shown in FIG. 2 . Barber electrode is obtained by sputtering Al material and photolithography according to a certain pattern, Cu electrode is formed by sputtering technology to form a layer of copper metal layer, and patterning and photolithography to obtain the required six electrodes.

As shown in Figure 2, it includes eight identical anisotropic magnetoresistive thin film strips, the Barber electrodes used on the right magnetoresistive material and six identical a, b, c, d, e, and f are made of conductive materials. formed electrode part. applied magnetic field It is parallel to the film plane, and the included angle with the current direction of the magnetoresistive film strip B is θ (as shown in FIG. 2 ).

For the left region, the resistivity of the magnetoresistive thin film strip B is:

p _B (θ)=p _B⊥ sin ² θ+p _B|| cos ² θ (1)

The resistivity of the magnetoresistive film strip A is:

p _A (θ)=p _A⊥ cos ² θ+p _A|| sin ² θ (2)

Since the magnetoresistive film strip A and the magnetoresistive thin film strip B have a 90° phase angle difference in space, after they form a series circuit, under the same magnetic field Under the action, when the direction of the magnetic field changes, the voltage U ₁₊ (θ) between b and f can be expressed as:

Substituting the expressions of ρ _A (θ) and ρ _B (θ) into Equation (3), we get:

Similarly:

so

For the four magnetoresistive film strips in the right area A', B', C, and 'D', due to the addition of Barber electrodes, the current flow direction is inclined. At this time, for B', the resistivity is:

The resistivity of the magnetoresistive thin film strip A' is:

At this time, the voltage U ₂₊ (θ) between df can be expressed as:

Substituting ρ _A' (θ) and p _B' (θ) into equation (9), we get:

so

In formula (10)(11)(12), Δρ=ρ _|| -ρ _⊥ , ρ _|| represents the resistivity when the magnetization and the current are in the same direction, and ρ _⊥ represents the resistivity when they are perpendicular to each other. It can be seen from the expressions of U _out1 and U _out2 that when the magnetic field angle changes, U _out1 and U _out2 also change with the change of θ, but one of them has a sine relationship and the other has a cosine relationship. There is a larger output voltage. The larger output voltage is used as the actual measurement voltage to achieve the purpose of extending the linear region, making the magnetoresistive thin film sensor more sensitive. The use of a bridge structure has the benefit of temperature compensation, making the sensor more stable.

A preparation process of a double bridge type thin film magnetoresistive sensor for measuring the magnetic field direction of the present invention is:

1) Prepare the silicon substrate, clean and dry it;

2) Oxidation on the silicon substrate to form a layer of silicon oxide film;

3) Sputtering the NiFe layer, after annealing, forming magnetoresistive strips by photolithography according to a certain pattern mask;

4) Sputtering Al electrodes, photolithography forms Barber electrode patterns (barber electrodes are formed by photolithography lift-off method);

5) Sputtering Cu electrodes, and photolithography forms six test electrodes;

6) Subsequent packaging.

The difference of the present invention is:

In the present invention, the double-bridge type thin film magnetoresistive sensor for measuring the direction of the magnetic field adopts a double-bridge structure, and one of the bridges also applies a Barber electrode. Since the Barber electrode can deflect the current direction and the angle of the easy magnetization axis, one of the two bridges always works in the linear working area, thereby expanding the linear working area and making the device more stable.

The structure satisfying the above conditions is regarded as the double bridge type thin film magnetoresistive sensor for measuring the magnetic field direction of the present invention.

Claims (8)

1. a double bridge type thin film magnetoresistive sensor, it is characterized in that, this double bridge type thin film magnetoresistive sensor is realized by applying Barber electrode, including the substrate (1), insulating layer (2) that are stacked sequentially from bottom to top , anisotropic magnetoresistive layer (3), Barber electrode layer (4) and top electrode layer (5); the anisotropic magnetoresistive layer (3) consists of four identical anisotropic magnetoresistive thin film strips A, B, The head and tail of C and D are connected in sequence to form a bridge, and another set of four identical anisotropic magnetoresistive thin film strips A', B', C', D' are connected in sequence to form another bridge. The bridges are connected in parallel to form the double-bridge type thin film magnetoresistive sensor; wherein, the phase difference between the magnetoresistive thin film strip A and the magnetoresistive thin film strip B is 90°, and the phase difference between the magnetoresistive thin film strip B and the magnetoresistive thin film strip C is 90°. °, the phase difference between the magnetoresistive film strips C and the magnetoresistive film strips D is 90°, the arrangement of the magnetoresistive film strips A'B'C'D' is the same as that of the magnetoresistive film strips ABCD, and the magnetoresistive film strips A', B' , C', and D' are all applied with Barber electrodes that form an angle of 45° with the long axis of the magnetoresistive film. 2 . The double-bridge type thin film magnetoresistive sensor according to claim 1 , wherein the four magnetoresistive thin film strips of the anisotropic magnetoresistive layer (3) have identical anisotropic magnetoresistive effects. 3 . The iron-nickel alloy with anisotropic magnetoresistance effect is selected. 3 . The double bridge type thin film magnetoresistive sensor according to claim 2 , wherein the content of iron in the iron-nickel alloy is 20%. 4 . 4. A kind of double bridge type thin film magnetoresistive sensor according to claim 1, wherein the magnetoresistive thin film strip A, the magnetoresistive thin film strip B, the magnetoresistive thin film strip C, the The planar shape is a continuously connected S shape. 5 . The double bridge type thin film magnetoresistive sensor according to claim 1 , wherein the material used for the substrate 1 is Si. 6 . 6 . The double bridge type thin film magnetoresistive sensor according to claim 1 , wherein the insulating layer ( 2 ) is made of SiO ₂ , which has non-magnetic properties, good insulating properties, and stable chemical properties. 7 . , High strength and hardness, good stretchability. 7 . The double bridge type thin film magnetoresistive sensor according to claim 1 , wherein the material used for the Barber electrode layer ( 4 ) is aluminum. 8 . 8. A double bridge type thin film magnetoresistive sensor according to claim 1, characterized in that the material used in the top electrode layer (5) is copper.