CN111312891A - A kind of flexible GMR magnetic field sensor and preparation method thereof - Google Patents

Abstract

A flexible GMR magnetic field sensor and a preparation method thereof, comprising a flexible substrate, a giant magnetoresistance structure and a conductive layer; the giant magnetoresistance structure and the conductive layer are both arranged on the upper surface of the flexible substrate, and the conductive layer is arranged around the giant magnetoresistance structure; The giant magnetoresistance structure includes a first buffer layer, a second buffer layer, a pinned layer, an isolation layer and two ferromagnetic layers, the two ferromagnetic layers are respectively a pinned layer and a free layer; the first buffer layer is arranged on the flexible On the upper surface of the substrate, a pinning layer, a pinned layer, an isolation layer, a free layer and a second buffer layer are sequentially arranged on the first buffer layer from bottom to top to form a giant magnetoresistance structure. The invention realizes that the multi-layer magnetic sensor film with the giant magnetoresistance structure using the ultra-thin flexible substrate can be bent for tens of thousands of times with a radius of curvature of a micrometer without fatigue, and at the same time, the device area can be reduced to realize a high-density chip Integrated, has the advantages of high sensitivity, small size, low power consumption, high reliability, good temperature characteristics, and can be integrated.

Description

A kind of flexible GMR magnetic field sensor and preparation method thereof

technical field

The invention belongs to the technical field of sensor design, in particular to a flexible GMR magnetic field sensor and a preparation method thereof.

Background technique

Sensors have the functions of perception, acquisition, conversion, transmission and processing of magnetic field information, and have become an indispensable and important electronic component in automatic detection and automatic control systems. At present, GMR materials have been commercialized in the fields of magnetic sensors, computer read heads, magnetic random access memories, etc. Due to their high sensitivity to low fields, they are very suitable for the measurement of angles, positions, and rotational speeds in the field of industrial control. , and for the manufacture of high-density storage media, which are widely used in non-contact position measurement, traffic speed detection, biological detection, power systems and other fields. Compared with traditional sensors, GMR sensors have the advantages of high sensitivity, small size, low power consumption, high reliability, good temperature characteristics, and can be integrated, making them more and more market share in magnetic sensors. The giant magnetoresistance effect refers to the phenomenon that the resistivity of magnetic materials changes greatly when there is an external magnetic field compared to when there is no external magnetic field. Giant magnetoresistance is a quantum mechanical effect that arises from a layered magnetic thin film structure, which is formed by alternating thin layers of ferromagnetic and non-ferromagnetic materials. When the magnetic moments of the two adjacent ferromagnetic layers are parallel to each other, the spin-related scattering of carriers is the smallest, and the material has the smallest resistance; when the magnetic moments of the two adjacent ferromagnetic layers are antiparallel, The spin-dependent scattering is strongest and the material has the greatest resistance. The direction of the magnetic moment of a ferromagnetic material is controlled by an external magnetic field applied to the material. Generally, the exchange bias effect of antiferromagnetic materials is used to pin the magnetization direction of one ferromagnetic layer so that it cannot be freely turned; while the other ferromagnetic layer can be freely turned with an external magnetic field, which is called the free layer. When the external magnetic field exceeds the coercive field of the free layer, two states of parallel and anti-parallel magnetization directions can be realized, resulting in the minimum and maximum values of the magnetoresistance. There is a linear relationship between the extrema of magnetoresistance and the external magnetic field, so it can be used to measure the magnitude of the external magnetic field.

The current magnetic field sensor has the following defects and shortcomings: (1) The traditional magnetic field sensor is a current device based on the Hall effect, which has problems such as large volume, high power consumption, low sensitivity and small measurement range. The defects limit the application range of magnetic field sensors. (2) Although the new GMR sensor is a multi-layer thin film structure, which alleviates the shortcomings of high energy consumption of traditional magnetic field sensors, it still cannot get rid of the low device integration and insufficient space utilization, and the measurement range of the traditional sensor is further reduced. (3) The existing GMR magnetic field sensor is an inflexible structure, cannot be bent, folded and cut, cannot make full use of the volume shape, and the use density is not high enough. (4) Most of the existing GMR magnetic field sensors are silicon-based devices, which cannot solve the problems of weight, breakdown and leakage conductance in terms of integration. (5) The processing cost of the existing GMR device is high, and the commercial value is limited. (6) The existing GMR sensor is difficult to break through in solving the problems of heat dissipation and the influence of external temperature.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a flexible GMR magnetic field sensor and a preparation method thereof to solve the above problems.

To achieve the above object, the present invention adopts the following technical solutions:

A flexible GMR magnetic field sensor, comprising a flexible substrate, a giant magnetoresistance structure and a conductive layer; the giant magnetoresistance structure and the conductive layer are both arranged on the upper surface of the flexible substrate, and the conductive layer is arranged around the giant magnetoresistance structure; the giant magnetoresistance structure It includes a first buffer layer, a second buffer layer, a pinned layer, an isolation layer and two ferromagnetic layers, the two ferromagnetic layers are a pinned layer and a free layer respectively; the first buffer layer is arranged on the upper surface of the flexible substrate, A pinned layer, a pinned layer, an isolation layer, a free layer and a second buffer layer are sequentially arranged on the first buffer layer from bottom to top to form a giant magnetoresistance structure.

Further, the flexible substrate is PET, PEN, PMMA or Kapton.

Further, the conductive layer is one of Ta, Au, Ag, Al, Cu, Pt, W, Ti, Mo, TaN or TiN.

Further, the isolation layer is one of Ta, Au, Ag, Al, Cu, Pt, W, Ti or Mo.

Further, the free layer is one of CoFe, CoFe/Ru/CoFe, NiFe, CoFeB, FeGaB, Co, Fe, NiFeCo or CoNbZr.

Further, the pinned layer is an antiferromagnetic material in IrMn, PtMn or FeMn; the pinned layer is one of CoFe, CoFe/Ru/CoFe, NiFe, CoFeB, FeGaB, Co, Fe, NiFeCo or CoNbZr. ferromagnetic material; the buffer layer is Ta.

Further, the conductive layer is divided into four parts, and conductive layers are provided on both sides of the two ends of the giant magnetoresistance structure.

Further, a preparation method of a flexible GMR magnetic field sensor, comprising the following steps:

Step 1, surface cleaning of a flexible substrate with isopropanol and deionized water, and drying with _N2 ;

Step 2: Coat a layer of photoresist on the above-mentioned flexible substrate, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required magnetoresistive units and array patterns on the photoresist, and then develop and Drying to complete the first lithography;

Step 3, growing the giant magnetoresistance film, using the magnetron sputtering technology, depositing the required targets in sequence, and growing the multi-layer giant magnetoresistance film in the entire reserved area;

Step 4, peeling off, soaking in acetone solution, removing the remaining adhesive layer and the unnecessary giant magnetoresistive film on the adhesive layer by a peeling process, forming a reserved giant magnetoresistive unit and an array;

Step 5: Coat a layer of photoresist on the above-mentioned film, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required conductive layer pattern on the photoresist, then develop and dry to complete second lithography;

Step 6, the conductive layer is grown, and after the second photolithography is completed, a layer of conductive material is sputtered as the conductive layer;

Step 7, peeling off, after the sputtering is completed, the photoresist and the metal layer on it are removed by a peeling process to form a conductive layer.

Further, step 2 specifically includes the following operation process:

Glue coating: spray a layer of photoresist on the piezoelectric substrate, and place it in an oven at 115℃ for 20min after coating;

Exposure: UV exposure is used to engrave the desired shape pattern on the photoresist; first, the reticle is attached to the film to be exposed, then irradiated under UV laser for 9s, and then placed in an oven at 115°C for 1min;

Development: Soak the exposed piezoelectric substrate in the developer solution for 1 min. After the pattern appears, wash it with deionized water and dry it.

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

The invention utilizes the growth of the GMR magnetic material structure on the flexible substrate to realize the environmental application of the bending and stretching of the GMR magnetic field sensor. It can achieve tens of thousands of bends with a radius of curvature of micron level without fatigue, and can reduce the device area to achieve high-density chip integration. It has high sensitivity, small size, low power consumption, high reliability, and high temperature. Features are good, can be integrated and so on. Flexible GMR magnetic field sensors can be used in the fabrication of miniature magnetic sensor chips and their arrays in automotive electronics, IoT, and wearable devices.

Description of drawings

FIG. 1 is a cross-sectional view of the present invention.

Figure 2 is a top view of the present invention.

Fig. 3 is the production flow chart of the present invention.

Wherein: 1 flexible substrate; 2 first buffer layer; 3 pinned layer; 4 pinned layer; 5 isolation layer; 6 free layer; 7 conductive layer; 8 second buffer layer.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is further described:

Please refer to FIGS. 1 to 3, a flexible GMR magnetic field sensor, comprising a flexible substrate 1, a giant magnetoresistance structure and a conductive layer 7; the giant magnetoresistance structure and the conductive layer 7 are both arranged on the upper surface of the flexible substrate, and the conductive layer 7 is arranged Around the giant magnetoresistance structure; the giant magnetoresistance structure includes a first buffer layer 2, a second buffer layer 8, a pinning layer 3, an isolation layer 5 and two ferromagnetic layers, and the two ferromagnetic layers are respectively pinned Layer 4 and free layer 6; the first buffer layer 2 is arranged on the upper surface of the flexible substrate, and the first buffer layer 2 is sequentially arranged from bottom to top with a pinning layer 3, a pinned layer 4, an isolation layer 5, a free layer 6 and The second buffer layer 8 forms a giant magnetoresistance structure.

The flexible substrate 1 is PET, PEN, PMMA or Kapton.

The conductive layer is one of Ta, Au, Ag, Al, Cu, Pt, W, Ti, Mo, TaN or TiN.

The isolation layer is one of Ta, Au, Ag, Al, Cu, Pt, W, Ti or Mo.

The free layer is one of CoFe, CoFe/Ru/CoFe, NiFe, CoFeB, FeGaB, Co, Fe, NiFeCo or CoNbZr.

The pinned layer is an antiferromagnetic material in IrMn, PtMn or FeMn; the pinned layer is a ferromagnetic material in CoFe, CoFe/Ru/CoFe, NiFe, CoFeB, FeGaB, Co, Fe, NiFeCo or CoNbZr material; the buffer layer is Ta.

The conductive layer 7 is divided into four parts, and the conductive layers 7 are provided on both sides of the two ends of the giant magnetoresistance structure.

A preparation method of a flexible GMR magnetic field sensor, comprising the following steps:

Step 1, surface cleaning of a flexible substrate with isopropanol and deionized water, and drying with _N2 ;

Step 2: Coat a layer of photoresist on the above-mentioned flexible substrate, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required magnetoresistive units and array patterns on the photoresist, and then develop and Drying to complete the first lithography;

Step 3, growing the giant magnetoresistance film, using the magnetron sputtering technology, depositing the required targets in sequence, and growing the multi-layer giant magnetoresistance film in the entire reserved area;

Step 4, peeling off, soaking in acetone solution, removing the remaining adhesive layer and the unnecessary giant magnetoresistive film on the adhesive layer by a peeling process, forming a reserved giant magnetoresistive unit and an array;

Step 5: Coat a layer of photoresist on the above-mentioned film, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required conductive layer pattern on the photoresist, then develop and dry to complete second lithography;

Step 6, the conductive layer is grown, and after the second photolithography is completed, a layer of conductive material is sputtered as the conductive layer;

Step 7, peeling off, after the sputtering is completed, the photoresist and the metal layer on it are removed by a peeling process to form a conductive layer.

Step 2 specifically includes the following operations:

Glue coating: spray a layer of photoresist on the piezoelectric substrate, and place it in an oven at 115℃ for 20min after coating;

Exposure: UV exposure is used to engrave the desired shape pattern on the photoresist; first, the reticle is attached to the film to be exposed, then irradiated under UV laser for 9s, and then placed in an oven at 115°C for 1min;

Development: Soak the exposed piezoelectric substrate in the developer solution for 1 min. After the pattern appears, wash it with deionized water and dry it.

Step 1: Use isopropanol and deionized water for surface cleaning of a substrate, and dry it with N2; as shown in Figure 3a. Step 2: apply a layer of photoresist on the above-mentioned piezoelectric substrate, and remove the photoresist layer outside the pattern with ultraviolet light exposure,

That is, the required magnetoresistive units and array patterns are engraved on the photoresist, and then developed and dried to complete the first lithography; as shown in Figure 3b.

Step 3: grow the giant magnetoresistance film, adopt the magnetron sputtering technology, deposit the required target material in sequence, and grow the multi-layer giant magnetoresistance film in the entire reserved area; as shown in Figure 3c.

Step 4: peel off, soak in acetone solution, remove the remaining adhesive layer and the magnetoresistive film on the adhesive layer by a peeling process, and form a reserved giant magnetoresistive unit and array; as shown in Figure 3d.

Step 5: apply a layer of photoresist on the above-mentioned film, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required conductive layer pattern on the photoresist, then develop and dry to complete Second lithography; Figure 3e.

Step 6: The conductive layer is grown, and after the second lithography is completed, a layer of conductive material is sputtered as the conductive layer; as shown in Figure 3f.

Step 7: stripping, after the sputtering is completed, the photoresist and the metal layer on it are removed by a stripping process to form a conductive layer. Figure 3g.

Claims (9)

1. a flexible GMR magnetic field sensor, is characterized in that, comprises flexible substrate (1), giant magnetoresistance structure and conductive layer (7); Giant magnetoresistance structure and conductive layer (7) are all arranged on flexible substrate upper surface, and The conductive layer (7) is arranged around the giant magnetoresistance structure; the giant magnetoresistance structure comprises a first buffer layer (2), a second buffer layer (8), a pinning layer (3), an isolation layer (5) and two A ferromagnetic layer, the two ferromagnetic layers are a pinned layer (4) and a free layer (6) respectively; the first buffer layer (2) is arranged on the upper surface of the flexible substrate, and the first buffer layer (2) is from bottom to top A pinning layer (3), a pinned layer (4), an isolation layer (5), a free layer (6) and a second buffer layer (8) are sequentially arranged on the top to form a giant magnetoresistance structure. 2 . The flexible GMR magnetic field sensor according to claim 1 , wherein the flexible substrate is PET, PEN, PMMA or Kapton. 3 . 3 . The flexible GMR magnetic field sensor according to claim 1 , wherein the conductive layer is one of Ta, Au, Ag, Al, Cu, Pt, W, Ti, Mo, TaN or TiN. 4 . 4 . The flexible GMR magnetic field sensor according to claim 1 , wherein the isolation layer is one of Ta, Au, Ag, Al, Cu, Pt, W, Ti or Mo. 5 . 5 . The flexible GMR magnetic field sensor according to claim 1 , wherein the free layer is one of CoFe, CoFe/Ru/CoFe, NiFe, CoFeB, FeGaB, Co, Fe, NiFeCo or CoNbZr. 6 . 6. A flexible GMR magnetic field sensor according to claim 1, wherein the pinned layer is an antiferromagnetic material in IrMn, PtMn or FeMn; the pinned layer is CoFe, CoFe/Ru/CoFe , a ferromagnetic material in NiFe, CoFeB, FeGaB, Co, Fe, NiFeCo or CoNbZr; the buffer layer is Ta. 7 . The flexible GMR magnetic field sensor according to claim 1 , wherein the conductive layer is divided into four parts, and the conductive layers are provided on both sides of the two ends of the giant magnetoresistance structure. 8 . 8. A preparation method of a flexible GMR magnetic field sensor, characterized in that, based on the flexible GMR magnetic field sensor described in any one of claims 1 to 7, comprising the following steps: Step 1, surface cleaning of a flexible substrate with isopropanol and deionized water, and drying with _N2 ; Step 2: Coat a layer of photoresist on the above-mentioned flexible substrate, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required magnetoresistive units and array patterns on the photoresist, and then develop and Drying to complete the first lithography; Step 3, growing the giant magnetoresistance film, using the magnetron sputtering technology, depositing the required targets in sequence, and growing the multi-layer giant magnetoresistance film in the entire reserved area; Step 4, peeling off, soaking in acetone solution, removing the remaining adhesive layer and the unnecessary giant magnetoresistive film on the adhesive layer by a peeling process, forming a reserved giant magnetoresistive unit and an array; Step 5: Coat a layer of photoresist on the above-mentioned film, remove the photoresist layer outside the pattern with ultraviolet light exposure, that is, engrave the required conductive layer pattern on the photoresist, then develop and dry to complete second lithography; Step 6, the conductive layer is grown, and after the second photolithography is completed, a layer of conductive material is sputtered as the conductive layer; Step 7, peeling off, after the sputtering is completed, the photoresist and the metal layer on it are removed by a peeling process to form a conductive layer. 9. The preparation method of a flexible GMR magnetic field sensor according to claim 8, wherein step 2 specifically comprises the following operations: Glue coating: spray a layer of photoresist on the piezoelectric substrate, and place it in an oven at 115℃ for 20min after coating; Exposure: UV exposure is used to engrave the desired shape pattern on the photoresist; first, the reticle is attached to the film to be exposed, then irradiated under UV laser for 9s, and then placed in an oven at 115°C for 1min; Development: Soak the exposed piezoelectric substrate in the developer solution for 1 min. After the pattern appears, wash it with deionized water and dry it.

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