CN109471051B - TMR full-bridge magnetic sensor and preparation method thereof - Google Patents
TMR full-bridge magnetic sensor and preparation method thereof Download PDFInfo
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Abstract
A TMR full bridge magnetic sensor comprising: the TMR device comprises a substrate, 4 groups of TMR units which are prepared on the substrate at one time, and a permanent magnetic layer pair which is prepared on the substrate at one time, wherein the permanent magnetic layer pair provides a bias field for the TMR units; the bridge connection of the 4 groups of TMR units forms a full bridge structure; the coercive fields of the permanent magnetic layer pairs of adjacent TMR cells are different and the coercive fields of the permanent magnetic layer pairs of opposite TMR cells are the same. The invention adopts different permanent magnetic layers of coercive fields to provide bias fields for different TMR units, thus two permanent magnetic layers with opposite magnetization directions are obtained after magnetizing in a specific mode, the magnetic moment directions of free layers of TMR units at different positions can be different, TMR units at corresponding positions have opposite responses to the same sensitive direction, opposite magnetic resistance corresponding trend is formed for the applied fields, the dynamic range is wider, a full bridge structure can be formed on a single chip, and the difficulty and cost of the production process are greatly reduced.
Description
Technical Field
The present invention relates to a magnetic field sensor, and more particularly to a single-chip full-bridge magnetic sensor.
Background
A magnetic sensor is a sensor that can detect the direction, strength, and position of a magnetic field, and has been widely used in many fields. TMR (Tunnel Magnetoresistance, tunneling magneto resistance) sensor is one type of magnetic sensor, and has advantages of low offset, high sensitivity, and good temperature performance, and has been recently put into practical use in industrial fields. The magneto-resistance of the TMR sensor can change along with the change of the magnitude and the direction of an external magnetic field, the sensitivity of the TMR sensor is superior to that of a Hall effect sensor, an AMR (Anisotropy Magnetoresistance, anisotropic magneto-resistance) sensor and a GMR (Giant Magnetoresistance, giant magneto-resistance) sensor, and the TMR sensor has better temperature stability and lower power consumption, and the processing technology of the TMR sensor can be conveniently combined with the existing semiconductor technology, so that the TMR sensor has more application prospect.
The magnetic resistance sensor with the full-bridge structure can effectively improve the sensitivity and the temperature stability of the device. TMR sensors require that the magnetization directions of the pinned layers of TMR cells on adjacent legs be opposite for full bridge construction because their own magnetoresistance change is derived from the relative orientations of the free and pinned layers. The TMR units prepared at one time are usually on the same chip, and the magnetization directions of the pinning layers of the TMR units on the same chip are the same because the whole process is the same, so that the full-bridge structure is difficult to form on a single chip at one time. Current approaches to achieving bridging on a single chip are laser annealing and fractional deposition. The laser annealing adopts laser annealing equipment to pin the magnetization directions of the pinning layers in different areas in opposite directions, but the laser annealing equipment is high in price, so that the production cost is high. The fractional deposition is to grow pinning layers with different magnetization directions in sequence by two depositions, but the first layer is easy to be influenced when the second layer is grown by two depositions, and finally the performance of the device is influenced.
In order to solve the problems of high cost and unstable performance of the existing full-bridge magnetic sensor prepared on a single chip, the Chinese patent application with the publication number of CN102226836A proposes a single-chip bridge magnetic field sensor, which comprises four magnetoresistive elements, each magnetoresistive element is formed by connecting one or more GMR or MTJ sensing elements in series, the sensing elements comprise a magnetic free layer and a magnetic pinning layer, the directions of the magnetic pinning layers of the magnetoresistive elements are arranged in the same direction, the magnetic moment directions of the magnetic free layers of the two magnetoresistive elements at opposite positions are the same, and the magnetic moment directions of the magnetic free layers of the two magnetoresistive elements at adjacent positions are different. The magnetic moment direction of the magnetic free layer is biased by a pair of permanent magnets, the residual magnetism angles of two adjacent surfaces of the square permanent magnets or strip permanent magnets with different orientations are utilized to provide magnetic fields with different directions for the MTJ sensing element, so that the magnetic free layer of the MTJ sensing element positioned between the permanent magnets is arranged in two different directions, the magnetization directions of the pinning layers are consistent, and finally the MTJ sensing element shows different responses to the same externally applied magnetic field. Chinese patent No. 201110326725.6 also discloses a single chip bridge type magnetic field sensor of similar structure. The magnetic sensor disclosed in the above patent, although realizing the formation of a full bridge structure on a single chip by adopting a one-step process, has an insufficient dynamic range and still needs to be improved.
Disclosure of Invention
The invention aims to provide a TMR full-bridge magnetic sensor with stable performance and wide dynamic range and a single chip.
In order to achieve the above object, the present invention adopts the following technical solutions:
a TMR full bridge magnetic sensor comprising: the TMR unit comprises a free layer, a pinning layer and a tunnel layer, wherein permanent magnetic layers for providing bias fields for the TMR unit are arranged on two sides of the TMR unit, and 4 groups of TMR units connected in a bridge mode form a full bridge structure; the magnetic moment directions of the pinning layers of the TMR units are the same, the magnetic moment directions of the free layers of the adjacent TMR units are opposite, and the magnetic moment directions of the free layers of the opposite TMR units are the same.
Further, the permanent magnetic layer comprises a first permanent magnetic layer and a second permanent magnetic layer, the coercive fields of the first permanent magnetic layer and the second permanent magnetic layer are different, and in 4 groups of TMR units, the bias fields of two groups of opposite TMR units are provided by the first permanent magnetic layer, and the bias fields of the other two groups of opposite TMR units are provided by the second permanent magnetic layer.
A TMR full bridge magnetic sensor comprising: the TMR comprises a substrate and 4 groups of TMR units arranged on the substrate, wherein the 4 groups of TMR units are connected in a bridge mode to form a full-bridge structure, the TMR units comprise a free layer, a pinning layer and a tunnel layer, the magnetic moment directions of the pinning layers of the TMR units are the same, and permanent magnetic layers for providing bias fields for the TMR units are arranged on two sides of the TMR units; the permanent magnetic layers comprise a first permanent magnetic layer and a second permanent magnetic layer with different coercive fields, the magnetization directions of the first permanent magnetic layer and the second permanent magnetic layer are opposite, the first permanent magnetic layer is arranged at two sides of two groups of TMR units which are oppositely arranged, and the second permanent magnetic layer is arranged at two sides of the other two groups of TMR units which are oppositely arranged.
Further, the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of two permanent magnetic materials with different coercive fields, or the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of the same permanent magnetic material with different thicknesses.
A TMR full bridge magnetic sensor comprising: the TMR device comprises a substrate, 4 groups of TMR units prepared on the substrate at one time, and a permanent magnetic layer pair arranged on the substrate, wherein the permanent magnetic layer pair provides a bias field for the TMR units; the bridge connection of the 4 groups of TMR units forms a full bridge structure; the coercive fields of the permanent magnetic layer pairs of adjacent TMR cells are different and the coercive fields of the permanent magnetic layer pairs of opposite TMR cells are the same.
As can be seen from the above technical solutions, in the full-bridge structure of the magnetic sensor of the present invention, the magnetic moment directions of the free layers of the TMR cells located at opposite positions are the same, and the magnetic moment directions of the free layers of the TMR cells located at adjacent positions are opposite, so that the corresponding TMR cells have opposite responses to the same sensitive direction (external magnetic field) by biasing the free layers of the adjacent TMR cells in opposite directions, thereby realizing a larger dynamic range. In a further scheme, the invention adopts the permanent magnetic layers with different coercive fields to provide bias fields for the TMR unit, and magnetic moment of the free layer can be biased in a specific direction after magnetizing in a specific mode, so that pinning layers with different magnetizing directions are not required to be grown successively in a fractional deposition mode, the problem of unstable performance caused by a fractional deposition process is solved, and the problem of high cost caused by a laser annealing process can be avoided.
The invention also provides a preparation method of the TMR full-bridge magnetic sensor, which comprises the following steps:
providing a substrate;
depositing TMR units on the substrate, wherein the magnetic moment directions of pinning layers of the TMR units are the same, and 4 groups of TMR units are connected in a bridge mode to form a full bridge structure;
the coercive fields of the permanent magnetic layers of the TMR units located at opposite positions are the same, and the coercive fields of the permanent magnetic layers of the TMR units located at adjacent positions are different;
carrying out primary magnetization on the permanent magnetic layer along the direction parallel to the magnetic moment direction of the TMR unit pinning layer by using an external magnetic field with the magnetic field strength larger than the coercive field in the permanent magnetic layer;
and then carrying out second magnetization along the direction opposite to the first magnetization direction by using an external magnetic field with the magnetic field strength between coercive fields of the two permanent magnetic layers, wherein after the external magnetic field is removed, the magnetic moment directions of the free layers of the adjacent TMR units are opposite, and the magnetic moment directions of the free layers of the opposite TMR units are the same.
Further, two different permanent magnetic materials are adopted to deposit to form permanent magnetic layers with different coercive fields, or the same permanent magnetic material with different thicknesses is adopted to deposit to form permanent magnetic layers with different coercive fields.
A preparation method of a TMR full-bridge magnetic sensor comprises the following steps:
providing a substrate;
preparing 4 groups of TMR units on the substrate at one time, wherein the TMR units are connected in a bridge mode to form a full-bridge structure;
respectively depositing a first permanent magnetic layer on two sides of a group of TMR units, respectively depositing a second permanent magnetic layer on two sides of TMR units adjacent to the TMR units, respectively depositing a second permanent magnetic layer on two sides of TMR units opposite to the TMR units, wherein the coercive fields of the first permanent magnetic layer and the second permanent magnetic layer are different;
carrying out primary magnetization on the permanent magnetic layer along the direction parallel to the magnetic moment direction of the TMR unit pinning layer by using an external magnetic field with the magnetic field strength larger than the coercive field in the permanent magnetic layer;
and then carrying out second magnetization along the direction opposite to the first magnetization direction by using an external magnetic field with the magnetic field strength between coercive fields of the first permanent magnetic layer and the second permanent magnetic layer, wherein after the external magnetic field is removed, the magnetic moment directions of the free layers of the adjacent TMR units are opposite, and the magnetic moment directions of the free layers of the opposite TMR units are the same.
Further, the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of two permanent magnetic materials with different coercive fields, or the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of the same permanent magnetic material with different thicknesses.
After TMR units are prepared on a substrate, different permanent magnetic layers with different coercive fields are adopted to provide bias fields for different TMR units, so that two permanent magnetic layers with opposite magnetization directions are obtained after the TMR units are magnetized in a specific mode, the bias fields of free layers of the TMR units are provided by the permanent magnetic layers, the permanent magnetic layers with opposite magnetization directions can enable the magnetic moment directions of the free layers of the TMR units at different positions to be different, the magnetic moment directions of the free layers of the TMR units at opposite positions are the same, the magnetic moment directions of the free layers of the TMR units at adjacent positions are opposite, the TMR units at corresponding positions have opposite responses to the same sensitive direction, opposite magnetic resistance corresponding trends are formed for an applied field, and then a full-bridge structure can be formed on a single chip in the mode.
Drawings
In order to more clearly illustrate the embodiments of the present invention, the following description will briefly explain the embodiments or the drawings required for the description of the prior art, it being obvious that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.
Fig. 1 is a schematic diagram of a TMR cell of a conventional magnetic sensor;
FIG. 2 is a schematic diagram of the magnetic moment direction of the pinned layer of the free layer of a TMR cell;
FIG. 3 is a graph showing the resistance of a TMR cell and the magnetic moment direction of the free and pinned layers as a function of applied magnetic field;
FIG. 4 is a schematic diagram of the relative relationship of the magnetic moment directions of the free layer and the pinned layer;
FIG. 5a is a schematic diagram showing the change of the magnetic moment direction of the free layer under the action of an externally applied magnetic field when the magnetic moment directions of the free layer and the pinned layer are parallel in the same direction;
FIG. 5b is a graph showing the relationship between resistance and field strength of TMR cells with parallel magnetic moment directions of the free layer and the pinned layer under the action of an applied magnetic field;
FIG. 6a is a schematic diagram showing the change in the magnetic moment direction of the free layer under the action of an externally applied magnetic field when the magnetic moment directions of the free layer and the pinned layer are antiparallel;
FIG. 6b is a graph of resistance versus applied field strength for TMR cells with antiparallel magnetic moment directions of the free and pinned layers;
FIG. 7 is a plot of the magnetization of two permanent magnet materials with different coercive fields;
FIG. 8 is a schematic diagram showing the effect of magnetizing a permanent magnetic layer by the method of the present invention;
FIG. 9 is a schematic diagram of a magnetic sensor according to an embodiment of the present invention;
FIG. 10 is a graph showing a typical voltage output of a full bridge magnetic sensor according to an embodiment of the present invention.
Detailed Description
To make the above and other objects, features and advantages of the present invention more apparent, the following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a TMR cell of a magnetic sensor of the related art, and the TMR cell of the magnetic sensor shown in fig. 1 includes a free layer 1, a tunnel layer 3, and a pinned layer 4 in this order from top to bottom, an arrow 5 indicates a magnetic moment direction of the pinned layer 4, and an arrow 2 indicates a magnetic moment direction of the free layer 1. In the detection magnetic field range of the magnetic sensor, the magnetic moment direction 5 of the pinning layer 4 is not responsive to an externally applied magnetic field, and the size and the direction of the magnetic moment direction are not changed along with the change of the externally applied magnetic field. The magnetic moment direction 2 of the free layer 1 is sensitive to an applied magnetic field and its magnitude and direction will change with the change of the applied magnetic field.
When no external magnetic field is applied, the magnetic moment direction 2 of the free layer of the TMR unit and the magnetic moment direction 5 of the pinned layer 4 are perpendicular to each other (FIG. 2), if an external magnetic field 6 is applied, the magnetic moment direction 5 of the pinned layer 4 will not change, and the magnetic moment direction 2 of the free layer 1 will change with the magnitude and direction of the external magnetic field 6. Furthermore, the resistance of the TMR cell and the magnetic moment direction 2 of the free layer 1 are related to the relative magnetization state of the magnetic moment direction 5 of the pinned layer 4. As shown in fig. 3 (R in fig. 3 represents the resistance value of the TMR cell, H represents the field strength of the applied magnetic field), the resistance of the TMR cell is smallest when the magnetic moment direction 2 of the free layer 1 and the magnetic moment direction 5 of the pinned layer 4 are parallel and largest when the magnetic moment direction 2 of the free layer 1 and the magnetic moment direction 5 of the pinned layer 4 are antiparallel.
The resistance of the TMR cell is smallest when the magnetic moment direction 2 of the free layer is biased in parallel with the magnetic moment direction 5 of the pinned layer and largest when the magnetic moment direction 2' of the free layer is biased in parallel with the magnetic moment direction of the pinned layer. Referring to fig. 4, when an externally applied magnetic field is applied in the direction indicated by arrow 6 in fig. 4, the magnetic moment direction 2 of the free layer, which is parallel to the magnetic moment direction 5 of the pinned layer, is flipped as shown in fig. 5a, and the resistance of the corresponding TMR cell changes as shown in fig. 5 b; whereas the magnetic moment direction 2' of the free layer, which is antiparallel to the magnetic moment direction 5 of the pinned layer, is flipped as shown in fig. 6a, the corresponding TMR cell has a resistance change as shown in fig. 6 b. That is, when the relative relationship between the magnetic moment direction of the free layer and the magnetic moment direction of the pinned layer is different, the same external magnetic field is applied, and the resistance of the TMR unit will generate different variation trends, when the magnetic moment direction 2 of the free layer is biased in parallel with the magnetic moment direction 5 of the pinned layer and in anti-parallel with the magnetic moment direction 5 of the pinned layer, the same external magnetic field is applied, and the two will show opposite resistance variation trends.
FIG. 7 is a graph of the magnetization of a permanent magnet material, the dashed line in FIG. 7 being the magnetization of a CoPt monolayer film, the solid line being CoPt/SiO 2 Magnetization curve of the CoPt multilayer film, the abscissa in FIG. 7 is the magnetic field strength of the applied magnetic field, and the ordinate is the magnetization strength of the permanent magnet material. The coercive fields of the two permanent magnetic materials are different, and the coercive field of the CoPt monolayer film has the magnetic field intensity value corresponding to the point 13, and the CoPt/SiO 2 The coercive field of the/CoPt multilayer film has a magnitude of the magnetic field strength corresponding to point 11. The coercive field is the minimum magnetic field that causes the magnetic moment of the permanent magnetic material to be inverted. The inventors have found that when two permanent magnet materials with different coercive fields are subjected to the following magnetization processes, the magnetic moment directions of the two permanent magnet materials are opposite: magnetizing the permanent magnetic materials in the positive or reverse direction by using an external magnetic field with the magnetic field strength larger than the coercive field of the two permanent magnetic materials to magnetize the two permanent magnetic materials along the direction of the external magnetic field, wherein the magnetic moment directions of the two magnetized materials are the same,for example, a CoPt monolayer film has a coercive field greater than CoPt/SiO 2 The coercive field of the CoPt multilayer film is used for magnetizing two materials by using an external magnetic field with the magnetic field strength larger than that of the coercive field of the CoPt monolayer film, the magnetic moment directions of the two materials are reversed, and the magnetic moment directions of the two materials are the same after magnetization; magnetizing the two permanent magnet materials with an external magnetic field (12 in FIG. 7) with a magnetic field strength between that of the two permanent magnet materials in a direction opposite to that of the first magnetizing, wherein the permanent magnet material with a large coercive field has no change in magnetic moment direction after the second magnetizing due to the fact that the magnetic field strength of the external magnetic field applied for the second time is smaller than that of the coercive field of the two permanent magnet materials, and the magnetic moment direction of the permanent magnet material with a small coercive field is reversed, for example, the strength of the external magnetic field is smaller than that of the coercive field of the CoPt monolayer film but larger than that of the CoPt/SiO 2 Coercive field of the CoPt multilayer film, after the second reverse magnetization, the magnetic moment direction of the CoPt monolayer film is unchanged, and the CoPt/SiO 2 The magnetic moment direction of the/CoPt multilayer film will be reversed so that the magnetization directions of the two materials are opposite. For the same pattern, the permanent magnetic layers of different materials will have opposite magnetization directions after being magnetized in the above manner (fig. 9).
The basic idea of the invention is as follows: in a single-chip TMR full-bridge magnetic sensor, two permanent magnetic materials with different coercive fields are adopted as permanent magnetic layers of TMR units, and bias magnetic fields are respectively provided for adjacent TMR units in the full-bridge magnetic sensor. As shown in fig. 9, a first permanent magnetic layer 9 is provided on each side of the TMR cell 18, and a second permanent magnetic layer 10 made of another permanent magnetic material is provided on each side of another TMR cell 18' adjacent to the TMR cell 18, the coercive field of the first permanent magnetic layer 9 being different from that of the second permanent magnetic layer 10. When the first permanent magnetic layer 9 and the second permanent magnetic layer 10 are magnetized twice in this order, the first permanent magnetic layer 9 and the second permanent magnetic layer 10 have opposite magnetic moment directions (magnetization directions), the first permanent magnetic layer 9 provides a bias field in the direction indicated by the dashed arrow 15 in fig. 9, the magnetic moment of the free layer in the TMR cell 18 is biased in the direction indicated by the arrow 2, the second permanent magnetic layer 10 provides a bias field in the direction indicated by the solid arrow 17 in fig. 9, the magnetic moment of the free layer in the TMR cell 18' is biased in the direction indicated by the arrow 2', and the magnetic moment directions of the pinned layers of the two TMR cells (18, 18 ') are both in the direction indicated by the black solid arrow 5. When an applied magnetic field 6 is applied, the resistance values of the two TMR cells (18, 18') are opposite in direction with respect to the applied magnetic field due to the opposite direction of the magnetic moment of the free layer.
The full-bridge magnetic sensor includes a substrate on which TMR units are provided, the TMR units including a pinned layer, a tunnel layer, and a free layer, the TMR units constituting magnetoresistive elements. As shown in fig. 9, 4 sets of bridge-connected magnetoresistive elements (R1, R2, R3, R4) form a full-bridge structure. Each magnetoresistive element has the same structure and the magnetization direction of the pinned layer is the same (direction indicated by arrow 5). The permanent magnetic layers for providing bias fields for the TMR units are respectively arranged on two sides of each TMR unit, the coercive fields of the permanent magnetic layers of adjacent TMR units are different, and the coercive fields of the permanent magnetic layers of opposite TMR units are the same. That is, in fig. 9, the bias field of the TMR cell 18 of the magnetoresistive element R1 is provided by the pair of first permanent magnetic layers 9, the bias field of the TMR cell 18 'of the magnetoresistive element R2 adjacent to the magnetoresistive element R1 is provided by the pair of second permanent magnetic layers 10, the coercive field of the first permanent magnetic layer 9 is different from the coercive field of the second permanent magnetic layer 10, the bias field of the TMR cell 18 of the magnetoresistive element R4 opposite to the magnetoresistive element R1 is provided by the pair of first permanent magnetic layers 9, and the bias field of the TMR cell 18' of the magnetoresistive element R3 opposite to the magnetoresistive element R2 is provided by the pair of second permanent magnetic layers 10. The first permanent magnetic layer 9 biases the magnetic moment direction (magnetization direction) of the TMR cell free layer in the magnetoresistive elements R1, R4 in the direction indicated by the arrow 2, and the second permanent magnetic layer 10 biases the magnetic moment direction (magnetization direction) of the TMR cell free layer in the magnetoresistive elements R2, R3 in the direction indicated by the arrow 2'. The first permanent magnetic layer 9 of this embodiment is a CoPt monolayer film and the second permanent magnetic layer 10 is a CoPt/SiO film 2 A CoPt multilayer film. Since in the magnetic sensor, the magnetic moment directions of free layers of adjacent magnetoresistive elements (TMR units) are opposite, when the free layers are in the same applied magnetic field, the free layers and the magnetic moment exhibit opposite resistance change trends, so that a wider detection range can be realized.
The preparation method of the full-bridge magnetic sensor comprises the following steps:
providing a substrate;
depositing TMR cells on a substrate;
respectively depositing permanent magnetic layers on two sides of each TMR unit, wherein the permanent magnetic layers provide bias fields for the TMR units, and the TMR units and the permanent magnetic layers are connected in a bridge mode to form a push-pull full-bridge structure, wherein the coercive fields of the permanent magnetic layers of adjacent TMR units are different, and the coercive fields of the permanent magnetic layers of opposite TMR units are the same; i.e. depositing a first permanent magnetic layer 9 on both sides of one TMR cell 18 and a second permanent magnetic layer 10 on both sides of the adjacent TMR cell 18', the coercive fields of the first and second permanent magnetic layers 9, 10 being different, assuming that the coercive field of the first permanent magnetic layer 9 is larger than the coercive field of the second permanent magnetic layer 10; before magnetizing, the magnetic moment directions of the pinning layers of the TMR units are the same, and the magnetic moment directions of the free layers are the same;
carrying out primary magnetization on the permanent magnetic layer along the direction parallel to the magnetic moment direction of the pinned layer of the TMR unit by using an external magnetic field with the magnetic field strength larger than the coercive field in the permanent magnetic layer, so that the two permanent magnetic layers with different coercive fields are magnetized; the first magnetization is performed by using an external magnetic field with a magnetic field strength larger than the coercive field of the first permanent magnetic layer 9 in the direction indicated by an arrow 19 in fig. 9, so that the first permanent magnetic layer 9 and the second permanent magnetic layer 10 are in a magnetized state, and after the external magnetic field is removed, the magnetic moment (magnetization) directions of the first permanent magnetic layer 9 and the second permanent magnetic layer 10 are the same;
then magnetizing the permanent magnetic layer for the second time along the direction opposite to the first magnetizing direction by using an external magnetic field with the magnetic field strength between the coercive field of the first permanent magnetic layer and the coercive field of the second permanent magnetic layer; namely, in the direction indicated by an arrow 20 in fig. 9, the first permanent magnetic layer 9 and the second permanent magnetic layer 10 are magnetized for the second time by using an external magnetic field with the magnetic field strength between the coercive field of the second permanent magnetic layer 10 and the coercive field of the first permanent magnetic layer 9, and the magnetic moment of the first permanent magnetic layer 9 is unchanged because the magnetic field strength of the external magnetic field is smaller than that of the first permanent magnetic layer 9 in the second magnetization, and the magnetic moment of the external magnetic layer is stronger than that of the second permanent magnetic layer 10, the second permanent magnetic layer 10 can turn over, and the directions (magnetization directions) of the residual fields of the first permanent magnetic layer 9 and the second permanent magnetic layer 10 are opposite after the external magnetic field of the second magnetization is removed; after two magnetizing, the first permanent magnetic layer pair (9) makes TMR single of the magneto-resistance elements R1, R4The magnetization direction of the free layer of the element is in the direction of arrow 2, the second pair of permanent magnetic layers (10) causes the magnetization direction of the free layer of the TMR cell of the magnetoresistive element R2, R3 to be in the direction of arrow 2', the directions of arrow 2 and arrow 2' being opposite, i.e. the first and second permanent magnetic layers bias the magnetic moment of the free layer of the corresponding TMR cell in two opposite directions; when measured, such as when an external magnetic field is applied in the measuring range (arrow 6 in fig. 9), the magnetization direction 2 of the free layers of the magnetoresistive elements R1, R4 is close to the magnetic moment direction 5 of the pinned layer, and the resistance thereof is reduced; the magnetization direction 2' of the free layers of the magnetoresistive elements R2, R3 is away from the magnetization direction 5 of the pinned layer, and its resistance increases; at a constant operating voltage V in When downwards V + And V - The voltage between the two electrodes is correspondingly changed, and thus a full bridge structure is formed. Fig. 10 is a typical voltage output curve of the full-bridge magnetic sensor, and compared with the design of a single-material permanent magnetic layer in the prior art, the invention adopts two materials to manufacture the permanent magnetic layer, provides different bias fields for different TMR units, and can realize a wider detection range.
Furthermore, the length of the permanent magnetic layer is far longer than the distance between the permanent magnetic layer pairs, and TMR structure units are arranged in parallel. The permanent magnetic layers made of different materials provide bias fields for different TMR units, so that magnetic moments of free layers of the different TMR units are biased in different directions, and when an external magnetic field acts, the magnetic resistance of the sensor can be changed due to the change of the relative orientations of the free layers and the pinning layers, thereby realizing detection of the magnetic field. The TMR magnetic sensor can form a full-bridge structure on a single chip at one time after magnetizing processes with different intensities and directions for two times, has simple and convenient preparation process and low process difficulty, does not need laser annealing and secondary deposition, can greatly reduce the production cost compared with the prior laser annealing technology, and can improve the production stability of devices compared with the prior secondary deposition technology.
Of course, the technical concept of the present invention is not limited to the above embodiments, and many different embodiments can be obtained according to the concept of the present invention, for example, the permanent magnetic material can also be SmCo, coCrPt, or other materials or composite structures thereof; the difference of coercive fields can be realized by adopting different permanent magnetic materials, and for the same material, the different coercive fields can be obtained by changing the thickness of the material; the magnetoresistive element may be a TMR cell or a TMR array; such modifications and equivalents are intended to be included within the scope of the present invention.
Claims (6)
1. A TMR full bridge magnetic sensor comprising: the TMR unit comprises a free layer, a pinning layer and a tunnel layer, wherein permanent magnetic layers for providing bias fields for the TMR unit are arranged on two sides of the TMR unit, and 4 groups of TMR units connected in a bridge mode form a full bridge structure;
the method is characterized in that:
the magnetic moment directions of the pinning layers of the TMR units are the same, the magnetic moment directions of the free layers of the adjacent TMR units are opposite, and the magnetic moment directions of the free layers of the opposite TMR units are the same;
the permanent magnetic layer comprises a first permanent magnetic layer and a second permanent magnetic layer, the coercive fields of the first permanent magnetic layer and the second permanent magnetic layer are different, and in 4 groups of TMR units, the bias fields of two groups of opposite TMR units are provided by the first permanent magnetic layer, and the bias fields of the other two groups of opposite TMR units are provided by the second permanent magnetic layer;
the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of two permanent magnetic materials with different coercive fields, or the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of the same permanent magnetic material with different thicknesses.
2. A TMR full bridge magnetic sensor comprising: the TMR comprises a substrate and 4 groups of TMR units arranged on the substrate, wherein the 4 groups of TMR units are connected in a bridge mode to form a full-bridge structure, the TMR units comprise a free layer, a pinning layer and a tunnel layer, the magnetic moment directions of the pinning layers of the TMR units are the same, and permanent magnetic layers for providing bias fields for the TMR units are arranged on two sides of the TMR units;
the method is characterized in that:
the permanent magnetic layer comprises a first permanent magnetic layer and a second permanent magnetic layer with different coercive fields, the magnetization directions of the first permanent magnetic layer and the second permanent magnetic layer are opposite, the first permanent magnetic layer is arranged at two sides of two groups of TMR units which are oppositely arranged, and the second permanent magnetic layer is arranged at two sides of the other two groups of TMR units which are oppositely arranged;
the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of two permanent magnetic materials with different coercive fields, or the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of the same permanent magnetic material with different thicknesses.
3. The preparation method of the TMR full-bridge magnetic sensor is characterized by comprising the following steps of:
providing a substrate;
depositing TMR units on the substrate, wherein the magnetic moment directions of pinning layers of the TMR units are the same, and 4 groups of TMR units are connected in a bridge mode to form a full bridge structure;
the coercive fields of the permanent magnetic layers of the TMR units located at opposite positions are the same, and the coercive fields of the permanent magnetic layers of the TMR units located at adjacent positions are different;
carrying out primary magnetization on the permanent magnetic layer along the direction parallel to the magnetic moment direction of the TMR unit pinning layer by using an external magnetic field with the magnetic field strength larger than the coercive field in the permanent magnetic layer;
and then carrying out second magnetization along the direction opposite to the first magnetization direction by using an external magnetic field with the magnetic field strength between coercive fields of the two permanent magnetic layers, wherein after the external magnetic field is removed, the magnetic moment directions of the free layers of the adjacent TMR units are opposite, and the magnetic moment directions of the free layers of the opposite TMR units are the same.
4. A method of manufacturing a TMR full-bridge magnetic sensor as claimed in claim 3, characterized in that: and adopting two different permanent magnetic materials to deposit to form permanent magnetic layers with different coercive fields, or adopting the same permanent magnetic material with different thicknesses to deposit to form permanent magnetic layers with different coercive fields.
5. The preparation method of the TMR full-bridge magnetic sensor is characterized by comprising the following steps of:
providing a substrate;
preparing 4 groups of TMR units on the substrate at one time, wherein the TMR units are connected in a bridge mode to form a full-bridge structure;
respectively depositing a first permanent magnetic layer on two sides of a group of TMR units, respectively depositing a second permanent magnetic layer on two sides of TMR units adjacent to the TMR units, respectively depositing a second permanent magnetic layer on two sides of TMR units opposite to the TMR units, wherein the coercive fields of the first permanent magnetic layer and the second permanent magnetic layer are different;
carrying out primary magnetization on the permanent magnetic layer along the direction parallel to the magnetic moment direction of the TMR unit pinning layer by using an external magnetic field with the magnetic field strength larger than the coercive field in the permanent magnetic layer;
and then carrying out second magnetization along the direction opposite to the first magnetization direction by using an external magnetic field with the magnetic field strength between coercive fields of the first permanent magnetic layer and the second permanent magnetic layer, wherein after the external magnetic field is removed, the magnetic moment directions of the free layers of the adjacent TMR units are opposite, and the magnetic moment directions of the free layers of the opposite TMR units are the same.
6. The method for manufacturing a TMR full-bridge magnetic sensor according to claim 5, wherein: the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of two permanent magnetic materials with different coercive fields, or the first permanent magnetic layer and the second permanent magnetic layer are respectively formed by deposition of the same permanent magnetic material with different thicknesses.
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| CN110320482A (en) * | 2019-07-23 | 2019-10-11 | 珠海多创科技有限公司 | A kind of TMR full-bridge Magnetic Sensor and preparation method thereof |
| US11169227B2 (en) * | 2019-08-28 | 2021-11-09 | Western Digital Technologies, Inc. | Dual free layer TMR magnetic field sensor |
| CN111505544B (en) * | 2020-04-22 | 2021-07-13 | 西安交通大学 | TMR magnetic field sensor capable of reconstructing sensitive direction and preparation method |
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