TWI449065B - A stacked spin-valve magnetic sensor and fabrication method thereof - Google Patents

Description

Stacked spin valve magnetoresistive sensor and manufacturing method thereof

The present invention relates to the structure of a magnetoresistive sensor, and more particularly to the structure of a vertically stacked spin valve magnetoresistive sensor.

FIG. 1 is a schematic diagram of a conventional multilayer magnetoresistance sensor. Referring to FIG. 1, the multilayer film magnetoresistive sensor 100 mainly comprises a first multilayer film magnetoresistive structure 101, a second multilayer film magnetoresistive structure 102, a third multilayer film magnetoresistive structure 103 and a fourth multilayer. The membrane magnetoresistive structure 104 is electrically connected to each other and configured as a Wheatstone bridge. The first multilayer film magnetoresistive structure 101, the second multilayer film magnetoresistive structure 102, the third multilayer film magnetoresistive structure 103, and the fourth multilayer film magnetoresistive structure 104 all have at least one first magnetic layer alternately stacked. The layer 112 and the at least one second magnetic layer 114, and at least one spacer layer 113 disposed in the first magnetic layer 112 and the second magnetic layer 114, and the magnetization direction 106 of the first magnetic layer 112 and the first when the applied magnetic field is zero The magnetization directions 108 of the two magnetic layers 114 are opposite in direction. When the conventional multilayer magnetoresistive sensor measures the applied magnetic field change, the second multilayer film magnetoresistive structure 102 and the fourth multilayer film magnetoresistive structure 104 are covered with a shielding layer 110 to make the second multilayer film. The magnetization direction 106 of the first magnetic layer 112 of the magnetoresistive structure 102 and the fourth multilayer film magnetoresistive structure 104 and the magnetization direction 108 of the second magnetic layer 114 and the resistance R12 remain fixed. The applied magnetic field causes a change in the angle between the magnetization direction 106 of the first magnetic layer 112 and the magnetization direction 108 of the second magnetic layer 114 in the first multilayer film magnetoresistive structure 101 and the third multilayer film magnetoresistive structure 103, causing the A change in the resistance R11 in a multilayer film magnetoresistive structure 101 and a third multilayer film magnetoresistive structure 103. Since the process of the shielding layer 110 is relatively special, it is not a standard process of the current semiconductor, and thus the complexity of the fabrication of the multilayer film magnetoresistive sensor is greatly increased.

2 is a schematic view of another conventional spin-valve magnetoresistance sensor. Referring to FIG. 2, the spin valve magnetoresistive sensor 200 mainly includes a first spin valve magnetoresistive structure 201, a second spin valve magnetoresistive structure 202, a third spin valve magnetoresistive structure 203, and a fourth self. The rotary valve magnetoresistive structure 204 is electrically connected to each other and configured as a Wheatstone bridge. The first spin valve magnetoresistive structure 201, the second spin valve magnetoresistive structure 202, the third spin valve magnetoresistive structure 203, and the fourth spin valve magnetoresistive structure 204 each have a pinned layer 210, A free layer 212, and a spacer 211 and an exchange bias layer 214 disposed in the fixed layer 210 and the free layer 212. The first spin valve magnetoresistive structure 201 is the same as the magnetization direction 206 of the fixed layer 210 of the third spin valve magnetoresistive structure 203; the fixed layer of the second spin valve magnetoresistive structure 202 and the fourth spin valve magnetoresistive structure 204 The magnetization direction 207 is the same, and the magnetization direction 206 is opposite to the magnetization direction 207 and perpendicular to the magnetization direction 208 of the free layer 212 when the applied magnetic field is zero. The four spin valve magnetoresistive configurations have the same magnetization direction 208 of the free layer 212, and the magnetization direction 208 changes with the applied magnetic field. The conventional magnetoresistive sensor must be equipped with a magnetization direction adjusting wire around the four sets of spin valve magnetoresistive structures, and the magnetization directions 206 and 207 of the fixed layer 210 are controlled to generate a magnetic field by a current generated by a high temperature. Parallel state. The applied magnetic field changes the magnetization direction 208 of the free layer 212, and differently changes the angle between the magnetization direction 206 and the magnetization direction 207 of the fixed layer 210, thereby obtaining different resistance values of R21 and R22. However, the method of adjusting the direction of the fixed layer 210 by using the magnetization direction adjusting wire is special, and it is required to apply a current at a high temperature, which is not a standard process of the current semiconductor, thereby increasing the complexity of the fabrication of the spin valve magnetoresistive sensor.

In view of the above, it is an object of the present invention to provide a magnetoresistive sensor using a spin valve stack structure having a relatively simple process.

The invention provides a stacked spin valve magnetoresistive sensor capable of sensing a single axial magnetic field change, which is composed of a first spin valve stack structure and a second spin valve stack structure. The first spin valve stack structure comprises a first spin valve magnetoresistive element, a dielectric layer and a second spin valve magnetoresistive element. Wherein the first spin valve magnetoresistive element has an upper surface, a lower surface and a first magnetization direction fixed, and the first magnetization direction and the upper surface and the lower surface are parallel to each other, and the dielectric layer is disposed on the first self Above the upper surface of the rotary valve magnetoresistive element, the second spin valve magnetoresistive element is disposed above the dielectric layer.

In an embodiment of the invention, the first spin valve magnetoresistive element comprises a first magnetoresistive structure and a second magnetoresistive structure. Wherein, the first magnetoresistive structure has a fixed first magnetization direction, the second magnetoresistive structure is disposed on one side of the first magnetoresistive structure, and has a second magnetization direction, and the second magnetization direction corresponds to the strength of the applied magnetic field And change.

In an embodiment of the invention, the second spin valve magnetoresistive element comprises: a third magnetoresistive structure and a fourth magnetoresistive structure. Wherein, the third magnetoresistive structure has a fixed third magnetization direction, and the fourth magnetoresistive structure is disposed on one side of the third magnetoresistive structure, which has a fourth magnetization direction, and the fourth magnetization direction corresponds to the strength of the applied magnetic field And change.

In an embodiment of the invention, the first magnetization direction and the third magnetization direction are in an anti-parallel direction, and the second magnetization direction and the fourth magnetization direction are the same.

In an embodiment of the invention, the first magnetization direction and the third magnetization direction are the same, and the second magnetization direction and the fourth magnetization direction are in an anti-parallel direction.

In an embodiment of the invention, the first magnetoresistive structure, the second magnetoresistive structure, the third magnetoresistive structure and the fourth magnetoresistive structure, wherein any of the magnetoresistive structures may be a synthetic antiferromagnetic structure (synthetic antiferromagnet) , referred to as SAF).

In an embodiment of the invention, the first synthetic antiferromagnetic structure comprises a first magnetic layer, a second magnetic layer and a coupling layer. The second magnetic layer is disposed on one side of the first magnetic layer, and the coupling layer is disposed between the first magnetic layer and the second magnetic layer.

In an embodiment of the invention, the second spin valve stack structure of the magnetoresistive sensor further includes a third spin valve magnetoresistive element, a dielectric layer and a fourth spin valve magnetoresistive element. Wherein, the third spin valve magnetoresistive element has an upper surface, a lower surface and a fixed first magnetization direction, and the first magnetization direction is parallel to the upper surface and the lower surface, and the dielectric layer is disposed on the third spin valve Above the upper surface of the magnetoresistive element, the fourth spin valve magnetoresistive element is disposed above the dielectric layer, wherein the third spin valve magnetoresistive element and the second spin valve magnetoresistive element and the fourth spin respectively The valve magnetoresistive element is electrically connected, and the first spin valve magnetoresistive element is electrically connected to the fourth spin valve magnetoresistive element and the second spin valve magnetoresistive element, respectively.

In an embodiment of the invention, the third spin valve magnetoresistive element comprises a first magnetoresistive structure and a second magnetoresistive structure. Wherein, the first magnetoresistive structure has a fixed first magnetization direction, the second magnetoresistive structure is disposed on one side of the first magnetoresistive structure, and has a second magnetization direction, and the second magnetization direction corresponds to the strength of the applied magnetic field And change.

In an embodiment of the invention, the fourth spin valve magnetoresistive element comprises a third magnetoresistive structure and a fourth magnetoresistive structure. Wherein, the third magnetoresistive structure has a fixed third magnetization direction, and the fourth magnetoresistive structure is disposed on one side of the third magnetoresistive structure, which has a fourth magnetization direction, and the fourth magnetization direction corresponds to the strength of the applied magnetic field And change.

In an embodiment of the present invention, when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are the same as the vertical first axis, and the first magnetization direction and the third magnetization direction are Anti-parallel and at right angles to the second magnetization direction.

In an embodiment of the present invention, when the external magnetic field is zero, the second magnetization direction and the fourth magnetization direction may be parallel to the first axial direction, the first magnetization direction and the third The magnetization directions are the same and are respectively at right angles to the second magnetization direction and the fourth magnetization direction.

The present invention proposes another stacked spin valve magnetoresistive sensor that senses two axial magnetic field variations and is composed of four sets of spin valve stack structures. In addition to the first spin valve stack structure and the second spin valve stack structure described above, a third spin valve stack structure and a fourth spin valve stack structure are further included. The third spin valve stack structure comprises a fifth spin valve magnetoresistive element and a sixth spin valve magnetoresistive element; a fourth spin valve stack structure comprising a seventh spin valve magnetoresistive element and an eighth spin Valve magnetoresistive element. Wherein, the fifth spin valve magnetoresistive element, the sixth spin valve magnetoresistive element, the seventh spin valve magnetoresistive element and the eighth spin valve magnetoresistive element respectively and the first spin valve magnetoresistive element, the second The spin valve magnetoresistive element, the third spin valve magnetoresistive element and the fourth spin valve magnetoresistive element are clamped at a 90 degree angle, wherein the seventh spin valve magnetoresistive element and the sixth spin valve magnetoresistive element respectively The eighth spin valve magnetoresistive element is electrically connected, and the fifth spin valve magnetoresistive element is electrically connected to the eighth spin valve magnetoresistive element and the sixth spin valve magnetoresistive element respectively, and is a second axial magnetic field Resistance sensor.

In an embodiment of the invention, the fifth spin valve magnetoresistive element and the seventh spin valve magnetoresistive element comprise a first magnetoresistive structure and a second magnetoresistive structure. Wherein, the first magnetoresistive structure has a fixed fifth magnetization direction, the fifth magnetization direction is in the same direction as the first magnetization direction, and the second magnetoresistive structure is disposed on one side of the first magnetoresistive structure, and has a sixth magnetization The direction, and the sixth magnetization direction changes according to the strength of the applied magnetic field. When the applied magnetic field is zero, the sixth magnetization direction and the second magnetization direction are at an angle of 90 degrees.

In an embodiment of the invention, the sixth spin valve magnetoresistive element and the eighth spin valve magnetoresistive element comprise a third magnetoresistive structure and a fourth magnetoresistive structure. Wherein, the third magnetoresistive structure has a fixed seventh magnetization direction, the seventh magnetization direction and the third magnetization direction are in the same direction, and the fourth magnetoresistive structure is disposed on one side of the third magnetoresistive structure, and has an eighth magnetization direction And the eighth magnetization direction changes according to the strength of the applied magnetic field. When the applied magnetic field is zero, the eighth magnetization direction and the fourth magnetization direction are at an angle of 90 degrees.

In an embodiment of the present invention, when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are the same as the vertical first axis, and the first magnetization direction and the third magnetization direction are opposite. An acute angle is formed between the parallel and the second magnetization direction, and the sixth magnetization direction and the eighth magnetization direction are the same as the vertical second axis, and the fifth magnetization direction and the seventh magnetization direction are antiparallel and between the sixth magnetization direction Sharp angle.

In an embodiment of the present invention, when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction may be antiparallel to the vertical first axis, the first magnetization direction and the third magnetization. The directions are the same and respectively form an acute angle with the second magnetization direction and the fourth magnetization direction; the sixth magnetization direction and the eighth magnetization direction may be antiparallel to the vertical second axis, and the fifth magnetization direction and the seventh magnetization direction are the same and An acute angle is formed between the sixth magnetization direction and the eighth magnetization direction, respectively.

In the spin valve stack structure of the present invention, since the two spin valve magnetoresistive elements are vertically stacked, different spin valve components can be used for stacking and reducing the magnetoresistance compared to the conventional planar configuration. The area of the sensor.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

3 is a cross-sectional view showing a spin valve stack structure in an embodiment of the present invention. Referring to FIG. 3, the spin valve stack structure 300 includes a first spin valve magnetoresistive element 301, a dielectric layer 394, and a second spin valve magnetoresistive element 302. The first spin valve magnetoresistive element 301 has an upper surface 392 and a lower surface 390, and includes a first magnetoresistive structure 310 (fixed layer), a second magnetoresistive structure 320 (free layer), and a spacer layer 350. A magnetoresistive structure 310 and a second magnetoresistive structure 320 are connected to each other, and the first magnetoresistive structure 310 has a fixed first magnetization direction D1. The first magnetization direction D1 and the upper surface 392 and the lower surface 390 are parallel to each other. . The second magnetoresistive structure 320 is disposed on one side of the first magnetoresistive structure 310 and has a second magnetization direction D2. The second magnetization direction D2 changes according to the strength of the applied magnetic field. The dielectric layer 394 is disposed above the upper surface 392 of the first spin valve magnetoresistive element 301. The second spin valve magnetoresistive element 302 is disposed above the dielectric layer 394, and includes a third magnetoresistive structure 330 (fixed layer) and a fourth magnetoresistive structure 340 (free layer), and the spacer layer 370 is disposed on the third magnetic layer The resistive structure 330 and the fourth magnetoresistive structure 340 are connected to each other, the third magnetoresistive structure 330 has a fixed third magnetization direction D3, and the fourth magnetoresistive structure 340 is disposed on one side of the third magnetoresistive structure 330. It has a fourth magnetization direction D4, and the fourth magnetization direction D4 changes in response to the strength of the applied magnetic field.

In order to configure the spin valve stack structure 300 as a magnetoresistive sensor for practical use, in the embodiment, the first magnetization direction D1 and the third magnetization direction D3 are antiparallel, and do not change with an applied magnetic field; A magnetization direction D1 and a third magnetization direction D3 may be along the hard axis direction of the spin valve, and also the direction in which the applied magnetic field is sensed. The second magnetization direction D2 and the fourth magnetization direction D4 are parallel in the same direction and may change with an applied magnetic field; when the applied magnetic field is zero, the second magnetization direction D2 and the fourth magnetization direction D4 may be along the spin valve. Easy axis direction.

In order to achieve the above object, a synthetic antiferromagnetic structure (SAF) can be used for any of the above magnetoresistive structures. The synthetic antiferromagnetic structure includes a first magnetic layer 312 disposed on one side of the first magnetic layer 312, and a coupling layer 316 disposed between the first magnetic layer 312 and the second magnetic layer 314. Therefore, in the present invention, there may be several variations in the spin valve stack structure. 3 to 5 are schematic cross-sectional views showing a stacking structure of a spin valve according to an embodiment of the present invention. Referring to FIG. 3, the first magnetoresistive structure 310 in the spin valve stack structure 300 can use a synthetic antiferromagnetic structure, and the remaining magnetoresistive structures are all single magnetic layers. The synthetic antiferromagnetic structure of the first magnetoresistive structure 310 is connected by a second magnetic layer 314 and a spacer layer 350. With the same annealing process, the magnetic field is applied to the magnetization direction D11 of the first magnetic layer 312 by the bias layer 360. Similarly, the third magnetization direction D3 of the third magnetoresistive structure 330 is also fixed by the bias layer 380, and It is in the same direction as the magnetization direction D11. The composite antiferromagnetic structure of the first magnetoresistive structure 310 can make the first magnetization direction D1 of the second magnetic layer 314 opposite to the magnetization direction D11 by the thickness of the coupling layer 316. In this embodiment, the coupling layer 316 The thickness is ruthenium (Ru), which is about 8 angstroms ( In this way, the first magnetization direction D1 and the third magnetization direction D3 can be simultaneously defined, and the third magnetization direction D3 is opposite to the first magnetization direction D1.

The above-mentioned spin valve magnetoresistive element type may be a giant magnetoresistance type (GMR) type spin valve and a tunneling magnetoresistance type (TMR) type spin valve. Among them, the giant magnetoresistive spin valve can use a non-ferromagnetic metal material as a spacer layer, such as copper, and a perforated magnetoresistive spin valve can use a tunneling oxide material as a spacer. Layers such as alumina (AlOx) and magnesium oxide (MgO). Both the fixed layer and the free layer of the two spin valves use a single layer containing a ferromagnetic material such as NiFe, CoFe, CoFeB or a composite layer of the above single layer, such as a synthetic antiferromagnetic structure. The bias layer is made of anti-ferromagnet such as FeMn, PtMn, IrMn.

In addition, referring to FIG. 4, the spin valve stack structure 400 can use a synthetic antiferromagnetic structure in addition to the first magnetoresistive structure 310 in the first spin valve magnetoresistive element 301, and fix the first magnetization direction D1. The third magnetization direction D3 of the third magnetoresistive structure 330 is opposite. In the second spin valve magnetoresistive element 302, the fourth magnetoresistive structure 340 may also use a synthetic antiferromagnetic structure whose antiferromagnetic structure is connected by a first magnetic layer 342 and a spacer layer 370. The first magnetic layer 342 has a fourth magnetization direction D4, and the fourth magnetization direction D4 and the second magnetization direction D2 are the same when no external magnetic field is applied. The synthetic antiferromagnetic structure in the fourth magnetoresistive structure 340 can reverse the magnetization direction D41 of the second magnetic layer 344 and the fourth magnetization direction D4 by controlling the thickness of the coupling layer 346. In the present embodiment, the thickness of the coupling layer 346 is ruthenium (Ru), for example, about 8 angstroms. The spin valve stack structure 400 is characterized by a simplified structure. The first spin valve magnetoresistive element 301 and the second spin valve magnetoresistive element 302 can use the same magnetic layer material and stacking order (magnetic layer 312 = magnetic layer 330). , magnetic layer 314 = magnetic layer 342, magnetic layer 320 = magnetic layer 344), so that only the position of the coupling layer and the spacer layer, the first spin valve magnetoresistive element 301 and the second spin valve magnetoresistive element 302 The same resistance value and magnetoresistance change amount can be obtained.

Referring to FIG. 5, the spin valve stack structure 500 uses a synthetic antiferromagnetic structure in addition to the first magnetoresistive structure 310 of the first spin valve magnetoresistive element 301 to fix the first magnetization direction D1. A synthetic antiferromagnetic structure is also used in the third magnetoresistive structure 330. In the same annealing process, the first spin valve magnetoresistive element 301 can have a first magnetization direction D1, and the third magnetoresistive structure 330 has a third magnetization direction D3. In the synthetic antiferromagnetic structure of the third magnetoresistive structure 330, the first magnetic layer 332 and the second magnetic layer 334 both have a third magnetization direction D3 and a third magnetization direction D3 by the thickness of the coupling layer 336. The first magnetization direction D1 is opposite. In an embodiment of the present invention, the coupling layer 336 in the third magnetoresistive structure 330 is ruthenium (Ru), for example, and may be about 13 angstroms. The spin valve stack structure 500 uses a synthetic antiferromagnetic structure as the third magnetoresistive structure 330 as compared to FIG. 3, which has the advantages of the first spin valve magnetoresistive element 301 and the second spin valve. The magnetoresistive element 302 can be obtained in nearly the same material and configuration, thereby obtaining similar resistance values and magnetoresistance variations.

In other embodiments of the present invention, in order to configure the spin valve stack structure as a magnetoresistive sensor for practical use, the first magnetization direction D1 and the third magnetization direction D3 may be the same, parallel to the spin valve. The direction of the hard axis is also the direction in which the applied magnetic field is sensed. The second magnetization direction D2 and the fourth magnetization direction D4 are in an anti-parallel direction, parallel to the easy axis direction of the spin valve, and also the magnetization direction when the applied magnetic field is zero.

6 to 7 are schematic cross-sectional views showing a stacking structure of a spin valve according to an embodiment of the present invention. Referring to FIG. 6, the second magnetoresistive structure 320 and the fourth magnetoresistive structure 340 in the spin valve stack structure 600 respectively use a first synthetic antiferromagnetic structure and a second synthetic antiferromagnetic structure, and the remaining magnetoresistive structures are A single magnetic layer. The first magnetoresistive layer 322 of the first synthetic antiferromagnetic structure may be the same as the second magnetoresistive layer 344 of the second synthetic antiferromagnetic structure, having the same magnetization direction as the applied magnetic field; the first synthetic antiferromagnetic The second magnetoresistive layer 324 in the structure may be the same as the first magnetoresistive layer 342 in the second synthetic antiferromagnetic structure, having a magnetization direction opposite to the applied magnetic field. The coupling layer 326 of the first synthetic antiferromagnetic structure may be the same as the coupling layer 346 of the second synthetic antiferromagnetic structure, for example, ruthenium (Ru), which may be about 8 angstroms. In the first synthetic antiferromagnetic structure, the first magnetic layer 322 and the spacer layer 350 are connected, and in the second synthetic antiferromagnetic structure, the first magnetoresistive layer 342 and the spacer layer 370 are connected. As in the above principle, the first magnetization structure 310 and the third magnetization structure 330, which are the fixed layers, may have the first magnetization direction D1 and the third magnetization direction D3 in the same annealing process. The second magnetization direction D2 is the same as the magnetization direction D41 of the second magnetic layer in the second synthetic antiferromagnetic structure in the absence of the applied magnetic field, and the fourth magnetization direction D4 is opposite to the magnetization direction D41 due to the action of the coupling layer 346. The second magnetization direction D2 and the fourth magnetization direction D4 are in an anti-parallel direction.

Referring to FIG. 7, the spin valve stack structure 700 may also be the first magnetoresistive structure 310, the second magnetoresistive structure 320, the third magnetoresistive structure 330, and the fourth magnetoresistive structure 340, respectively, using the first synthetic antiferrite The magnetic structure, the second synthetic antiferromagnetic structure, the third synthetic antiferromagnetic structure, and the fourth synthetic antiferromagnetic structure. Thus, in the same annealing process, each of the coupling layers in the synthetic antiferromagnetic structure can be used to make the first magnetization direction D1 and the third magnetization direction D3 the same, and the second magnetization direction D2 is in the absence of an applied magnetic field and the fourth magnetization. Direction D4 is antiparallel. It should be noted that the first synthetic antiferromagnetic structure is connected by the second magnetic layer 314 and the spacer layer 350, and the second magnetic layer 314 can exhibit the first magnetization direction D1, the magnetization direction D11 of the first magnetic layer 312, and the first A magnetization direction D1 is opposite. The second synthetic antiferromagnetic structure is in contact with the first magnetic layer 322 and the spacer layer 350, and may exhibit a second magnetization direction D2. The magnetization direction D21 of the second magnetic layer 324 is opposite to the first magnetization direction D2. The third synthetic antiferromagnetic structure is in contact with the second magnetic layer 334 and the spacer layer 370, and may exhibit a third magnetization direction D3. The magnetization direction D31 of the first magnetic layer 332 is opposite to the third magnetization direction D3. The fourth synthetic antiferromagnetic structure is in contact with the first magnetic layer 342 and the spacer layer 370, and may exhibit a fourth magnetization direction D4. The magnetization direction D41 of the second magnetic layer 344 is opposite to the first magnetization direction D4. In the present invention, each of the synthetic antiferromagnetic structures exhibits anti-parallel coupling, and thus the thickness of the coupling layer is ruthenium (Ru), for example, about 8 angstroms. The advantage of the spin valve stack structure 700 design is that the structure is simplified, and the first spin valve magnetoresistive element 301 and the second spin valve magnetoresistive element 302 can use the same synthetic antiferromagnetic layer material but the opposite stacking order (magnetic layer 312=magnetic layer 334, magnetic layer 314=magnetic layer 332, magnetic layer 322=magnetic layer 344, magnetic layer 324=magnetic layer 342). As a result, the first spin valve magnetoresistive element 301 and the second spin valve magnetoresistive element 302 can obtain the same resistance value and magnetoresistance change amount.

It is worth mentioning that, in other embodiments of the present invention, the above-mentioned several kinds of spin valve stack structures, wherein the relative positions of the first magnetoresistive structure 310 and the second magnetoresistive structure 320 are not limited, the third magnetic The relative positions of the configuration of the resistive structure 330 and the fourth magnetoresistive structure 340 are also not limited, and the relative positions of the first spin valve magnetoresistive element 301 and the second spin valve magnetoresistive element 302 are also not limited.

FIG. 8 is a cross-sectional view of a stacked spin valve magnetoresistive sensor 800 in accordance with an embodiment of the present invention. Referring to FIG. 8, the magnetoresistive sensor 800 of the present invention is composed of a first spin valve stack structure and a second spin valve stack structure, both of which have the same spin valve stack structure and corresponding magnetization directions. The first spin valve stack structure includes a first spin valve magnetoresistive element 301, a second spin valve magnetoresistive element 302, and a dielectric layer 394 disposed between the two; the second spin valve stack structure includes The third spin valve magnetoresistive element 303, the fourth spin valve magnetoresistive element 304, and a dielectric layer 394 disposed between the two. The respective rotary valve magnetoresistive elements can be repeatedly arranged in series. The first spin valve magnetoresistive element 301 and the third spin valve magnetoresistive element 303 have an upper surface and a lower surface, and include a first magnetoresistive structure 310 and a second magnetoresistive structure 320, and the spacer layer 350 is disposed at A magnetoresistive structure 310 and a second magnetoresistive structure 320 are connected to each other. The first magnetoresistive structure 310 has a fixed first magnetization direction D1, and the upper surface 392, the lower surface 390, and the sensing magnetic field are axially parallel to each other. The second magnetoresistive structure 320 is disposed on one side of the first magnetoresistive structure 310, and has a second magnetization direction D2, and the second magnetization direction D2 changes according to the strength of the applied magnetic field. The dielectric layer 394 is disposed above the upper surfaces of the first spin valve magnetoresistive element 301 and the third spin valve magnetoresistive element 303. The second spin valve magnetoresistive element 302 and the fourth spin valve magnetoresistive element 304 are disposed above the dielectric layer 394, and include a third magnetoresistive structure 330 and a fourth magnetoresistive structure 340. The three magnetoresistive structure 330 and the fourth magnetoresistive structure 340 are connected to each other. The third magnetoresistive structure 330 has a fixed third magnetization direction D3 which is anti-parallel to the first magnetization direction D1. The fourth magnetoresistive structure 340 is disposed on one side of the third magnetoresistive structure 330, and has a fourth magnetization direction D4, and the fourth magnetization direction D4 is changeable according to the strength of the applied magnetic field, and is parallel to the second magnetization direction D2. The above magnetization directions (D1, D2, D3, D4) are defined as the magnetization direction of the magnetic layer connected to the spacer layer in the magnetoresistive structure (310, 320, 330, 340). It should be noted that the third spin valve magnetoresistive element 303 and the first spin valve magnetoresistive element 301 can be completed in the same process, the second spin valve magnetoresistive element 302 and the fourth spin valve magnetoresistance Element 304 can also be completed in the same process.

Next, the third spin valve magnetoresistive element 303 is electrically connected to the second spin valve magnetoresistive element 302 and the fourth spin valve magnetoresistive element 304, respectively, and the first spin valve magnetoresistive element 301 and the fourth The spin valve magnetoresistive element 304 and the second spin valve magnetoresistive element 302 are electrically connected to each other to be configured as a Wheatstone bridge, which is referred to as a first magnetoresistive sensor 800 for detecting The magnetic field strength of the first axial direction (the first magnetization direction D1 or the third magnetization direction D3), when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are perpendicular to the first axis and are parallel in the same direction, first The magnetization direction is opposite to the third magnetization direction and is respectively perpendicular to the second magnetization direction and the fourth magnetization direction. Where 810 is the input voltage endpoint, 830 is the reference voltage endpoint, 820 is the first output voltage endpoint, and 840 is the second output voltage endpoint. Spin The electrical connection of the valve magnetoresistive element can be horizontally connected (CIP, Current-in-Plane, the in/out contact is on the same side or both sides of the spacer of the spin valve magnetoresistive element) or vertical series connection (CPP, Current-Perpendicular-to-Plane, the in/out contacts are on either side of the spin-valve magnetoresistive element spacer), depending on the type of spin-valve magnetoresistive element.

When sensing the applied magnetic field strength, the conventional spin valve magnetoresistive sensor needs to cover the shielding layer or the external loading current coil on the two spin valve magnetoresistive elements on either diagonal of the Wheatstone bridge. The reference valve resistance value of the spin valve magnetoresistive element is generated or the fixed layer magnetization direction of the spin valve magnetoresistive element is set, which causes process complexity. In an embodiment of the present invention, the first magnetization direction D1 and the third magnetization direction D3 in the spin valve magnetoresistive element are in an anti-parallel direction, and the second magnetization direction D2 and the fourth magnetization direction D4 are the same, such that The first spin valve magnetoresistive element 301 and the third spin valve magnetoresistive element 303 and the second spin valve magnetoresistive element 302 and the fourth spin valve magnetoresistive element 304 respectively have the same first resistance. The value and the second resistance value not only increase the sensitivity of the spin valve magnetoresistive sensor when sensing the applied magnetic field, but also do not need to be a conventional spin valve magnetoresistive sensor, plus a shielding layer or an external loading flow. The coil can sense the strength of the applied magnetic field.

9 is a cross-sectional view of a stacked spin valve magnetoresistive sensor 900 in accordance with yet another embodiment of the present invention. Referring to FIG. 9, the magnetoresistive sensor 900 can also utilize the first magnetization direction D1 and the third magnetization direction D3 of the spin valve magnetoresistive element to be the same, parallel to the applied magnetic field axial direction (first axial direction); The magnetization direction D2 and the fourth magnetization direction D4 vary in response to the strength of the applied magnetic field, and are antiparallel to each other. The first spin valve magnetoresistive element 301 and the third spin valve magnetoresistive element 303 and the second spin valve magnetoresistive element 302 and the fourth spin valve magnetoresistive element 304 respectively have the same first resistance value and The second resistance value is used to sense the strength of the applied magnetic field.

FIG. 10 is a cross-sectional view showing the actual structure of the stacked spin valve magnetoresistive sensor 1000 according to still another embodiment of the present invention, which can be composed of a vertically arranged spin valve magnetoresistive element. In the actual wafer process, the step of forming the spin valve stack structure may include: (1) continuously depositing a spin valve magnetoresistive element film layer (including the first spin valve magnetoresistive element 301, the third spin valve magnetoresistance) Element 303), dielectric layer, upper spin valve magnetoresistive element film layer (including second spin valve magnetoresistive element 302, fourth spin valve magnetoresistive element 304), and finally hard mask layer; (2 The lithography process defines the spin valve stack structure pattern; (3) sequentially etches the hard mask layer, the upper spin valve magnetoresistive element film layer, the dielectric layer, and the lower spin valve magnetoresistive element film layer to complete the spin The valve stack structure is fabricated. The step of forming another spin valve stack structure may include: (1) forming a lower spin valve magnetoresistive element; (2) depositing a dielectric layer; and (3) forming an upper spin valve magnetoresistive element. Then, the third spin valve magnetoresistive element is electrically connected to the second spin valve magnetoresistive element and the fourth spin valve magnetoresistive element respectively by using a via contact and a metal wire, the first spin valve The magnetoresistive elements are electrically connected to the fourth spin valve magnetoresistive element and the second spin valve magnetoresistive element respectively to form a Wheatstone bridge. The electrical connection method of the spin valve magnetoresistive element is exemplified by horizontal series connection (CIP). The upper electrode lead 810 can be electrically connected to the input voltage end point, the upper electrode lead 830 can be electrically connected to the reference voltage end point, the upper electrode lead 820 can be electrically connected to the first output voltage end point, and the upper electrode lead 840 can be electrically connected Electrically connected to the second output voltage endpoint.

In addition, in order to simultaneously measure the magnetic field strengths of the first axial direction and the second axial direction perpendicular to each other, FIG. 11 is a schematic cross-sectional view of the stacked spin valve magnetoresistive sensor according to still another embodiment of the present invention. Referring to FIG. 11 , the stacked spin valve magnetoresistive sensor 1100 can be configured as a set of first magnetoresistive sensors and rotate another set of first magnetoresistive sensors in a direction of ninety degrees, called A two-magnetoresistive sensor for detecting the magnetic field strength of the second axial direction. The second magnetoresistive sensor includes a fifth spin valve magnetoresistive element 305, a sixth spin valve magnetoresistive element 306, a seventh spin valve magnetoresistive element 307, and an eighth spin valve magnetoresistive element 308. Wherein, the fifth spin valve magnetoresistive element 305, the sixth spin valve magnetoresistive element 306, the seventh spin valve magnetoresistive element 307 and the eighth spin valve magnetoresistive element 308 and the first spin valve reluctance respectively Element 301, second spin valve magnetoresistive element 302, third spin valve magnetoresistive element 303, and fourth spin valve magnetoresistive element 304 are clamped at an angle of 90 degrees. The seventh spin valve magnetoresistive element 307 is electrically connected to the sixth spin valve magnetoresistive element 306 and the eighth spin valve magnetoresistive element 308, respectively, and the fifth spin valve magnetoresistive element 305 and the eighth spin respectively The valve magnetoresistive element 308 and the sixth spin valve magnetoresistive element 306 are electrically connected to complete two sets of Wheatstone bridges.

The fifth spin valve magnetoresistive element 305 and the seventh spin valve magnetoresistive element 307 include a first magnetoresistive structure 310 and a second magnetoresistive structure 320, which can be formed in the same process. The first magnetoresistive structure 310 has a fixed fifth magnetization direction D5, and the fifth magnetization direction D5 is the same as the first magnetization direction D1. The second magnetoresistive structure 320 is disposed on one side of the first magnetoresistive structure 310, and has a sixth magnetization direction D6, and the sixth magnetization direction D6 changes according to the strength of the applied magnetic field. When the applied magnetic field is zero, the sixth The magnetization direction D6 and the second magnetization direction D2 are at an angle of 90 degrees, both of which are along the easy axis direction of the spin valve magnetoresistive element. The sixth spin valve magnetoresistive element 306 and the eighth spin valve magnetoresistive element 308 include a third magnetoresistive structure 330 and a fourth magnetoresistive structure 340. The third magnetoresistive structure 330 has a fixed seventh magnetization direction D7, the seventh magnetization direction D7 and the third magnetization direction D3 are in the same direction, and the fourth magnetoresistive structure 340 is disposed on one side of the third magnetoresistive structure 330. It has an eighth magnetization direction D8, and the eighth magnetization direction D8 changes according to the strength of the applied magnetic field. When the applied magnetic field is zero, the eighth magnetization direction D8 and the fourth magnetization direction D4 are at an angle of 90 degrees, and the same Both are along the easy axis direction of the spin valve magnetoresistive element.

Referring to FIG. 11, in the first magnetoresistive sensor 1101, when no external magnetic field is applied, the second magnetization direction D2 and the fourth magnetization direction D4 are the same, and may be perpendicular to the first axial direction Dx (extending along the second axial direction Dy) ). The first magnetization direction D1 and the third magnetization direction D3 are anti-parallel, and are respectively separated from the second magnetization direction D2 and the fourth magnetization direction D4 by an acute angle θ. In the second magnetoresistive sensor, the sixth magnetization direction D6 and the eighth magnetization direction direction D8 are the same when there is no external magnetic field, and may extend perpendicular to the second axial direction Dy (along the first axial direction D+x). The fifth magnetization direction D5 and the seventh magnetization direction D7 are antiparallel, and are respectively separated from the sixth magnetization direction D6 and the eighth magnetization direction D8 by an acute angle θ. In an embodiment of the invention, the acute angle θ may be a 45 degree angle. The first axial magnetoresistive sensor 1101 is for detecting the magnetic field strength along the X-axis direction (D+x, Dx), and the second axial magnetoresistive sensor 1102 is for detecting The magnetic field strength along the Y-axis direction (D+y, Dy).

FIG. 12 is a cross-sectional view showing a stacked spin valve magnetoresistive sensor according to still another embodiment of the present invention. Referring to FIG. 12, in another embodiment of the present invention, for the same purpose, the magnetic field strengths of the first axial X-axis and the second axial Y-axis perpendicular to each other can be simultaneously sensed, when no external magnetic field is applied. In the first magnetoresistive sensor of the stacked spin valve magnetoresistive sensor 1200, the second magnetization direction D2 and the fourth magnetization direction D4 may be antiparallel, and the first axial direction Dx may be along The second axial directions Dy, Dy extend, and the first magnetization direction D1 and the third magnetization direction D3 are the same, and an acute angle θ is sandwiched between the second magnetization direction D2 and the fourth magnetization direction D4, respectively. In the second magnetoresistive sensor, the sixth magnetization direction D6 and the eighth magnetization direction D8 are perpendicular to the second axial direction Dy, extending along the first axial direction Dx, Dx, but the directions are anti-parallel, The fifth magnetization direction D5 and the seventh magnetization direction D7 are the same, and an acute angle θ is sandwiched between the sixth magnetization direction D6 and the eighth magnetization direction D8, respectively. In an embodiment of the invention, the acute angle θ may be a 45 degree angle.

In summary, in the spin valve stack structure of the present invention, since the two spin valve magnetoresistive elements are vertically stacked, different spin valve components can be used as a stack combination compared to the conventional planar configuration. And reduce the area of the magnetoresistive sensor. And the spin valve magnetoresistive element in the spin valve stack structure can define the opposite fixed layer or free layer magnetization direction in the same annealing process. In the subsequent magnetoresistive sensor of the process, since there are two sets of different magnetization directions, no additional shielding layer or current-carrying coil is needed, which reduces the complexity in the process.

While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

100. . . Multilayer film magnetoresistive sensor

101. . . First multilayer film magnetoresistive structure

102. . . Second multilayer film magnetoresistive structure

103. . . Third multilayer film magnetoresistive structure

104. . . Fourth multilayer film magnetoresistive structure

106, 108, 206, 207, 208, D11, D21, D31, D41. . . Magnetization direction

110. . . Masking layer

112. . . First magnetic layer

113, 211. . . Spacer

114. . . Second magnetic layer

200. . . Spin valve magnetoresistive sensor

201. . . First spin valve magnetoresistive structure

202. . . Second spin valve magnetoresistive structure

203. . . Third spin valve magnetoresistive structure

204. . . Fourth spin valve magnetoresistive structure

210. . . Fixed layer

212. . . Free layer

214. . . Bias layer

R11, R12, R21, R22. . . resistance

300, 400, 500, 600, 700. . . Spin valve stack structure

800, 900, 1000, 1100, 1200. . . Stacked spin valve magnetoresistive sensor

301. . . First spin valve magnetoresistive element

302. . . Second spin valve magnetoresistive element

303. . . Third spin valve magnetoresistive element

304. . . Fourth spin valve magnetoresistive element

305. . . Fifth spin valve magnetoresistive element

306. . . Sixth spin valve magnetoresistive element

307. . . Seventh spin valve magnetoresistive element

308. . . Eighth spin valve magnetoresistive element

310. . . First magnetoresistive structure

312, 322, 332, 342. . . First magnetic layer

314, 324, 334, 344. . . Second magnetic layer

316, 326, 336, 346‧‧‧ coupling layer

320‧‧‧Second magnetoresistive structure

330‧‧‧ Third magnetoresistive structure

340‧‧‧4th magnetoresistive structure

350, 370‧‧‧ spacer

360, 380‧‧‧ bias layer

810‧‧‧Input voltage endpoint

820‧‧‧First output voltage endpoint

830‧‧‧reference voltage endpoint

840‧‧‧second output voltage endpoint

1101‧‧‧First Magnetoresistive Sensor

1102‧‧‧Second Magnetoresistive Sensor

D1‧‧‧first magnetization direction

D2‧‧‧second magnetization direction

D3‧‧‧ Third magnetization direction

D4‧‧‧fourth magnetization direction

D5‧‧‧ fifth magnetization direction

D6‧‧‧ sixth magnetization direction

D7‧‧‧ seventh magnetization direction

D8‧‧‧8th magnetization direction

Dx‧‧‧first axial direction

Dy‧‧‧second axial

Θ‧‧‧ acute angle

FIG. 1 is a schematic diagram of a conventional multilayer film magnetoresistive sensor.

2 is a schematic diagram of another conventional spin valve magnetoresistive sensor.

3 to 7 are schematic cross-sectional views showing a stacking structure of a spin valve according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a stacked spin valve magnetoresistive sensor according to another embodiment of the present invention.

9 is a cross-sectional view showing a stacked spin valve magnetoresistive sensor in still another embodiment of the present invention.

10 to 12 are schematic cross-sectional views showing a stacked spin valve magnetoresistive sensor according to still another embodiment of the present invention.

800. . . Stacked spin valve magnetoresistive sensor

301. . . First spin valve magnetoresistive element

302. . . Second spin valve magnetoresistive element

303. . . Third spin valve magnetoresistive element

304. . . Fourth spin valve magnetoresistive element

310. . . First magnetoresistive structure

320. . . Second magnetoresistive structure

330. . . Third magnetoresistive structure

340. . . Fourth magnetoresistive structure

350, 370. . . Spacer

360, 380. . . Bias layer

390. . . Lower surface of the first magnetoresistive structure

392. . . Upper surface of the first magnetoresistive structure

394. . . Dielectric layer

810. . . Input voltage endpoint

820. . . First output voltage endpoint

830. . . Reference voltage endpoint

840. . . Second output voltage endpoint

D1. . . First magnetization direction

D2. . . Second magnetization direction

D3. . . Third magnetization direction

D4. . . Fourth magnetization direction

Claims (17)

A magnetoresistive stack structure comprising: a first spin valve magnetoresistive element having an upper surface and a lower surface, and comprising a first magnetoresistive structure, wherein the first magnetoresistive structure has one of constant a first magnetization direction, and the first magnetization direction and the upper surface and the lower surface are parallel to each other; a dielectric layer disposed above the upper surface of the first spin valve magnetoresistive element; and a second self a rotary valve magnetoresistive element disposed above the dielectric layer, comprising a third magnetoresistive structure, wherein the third magnetoresistive structure has a fixed third magnetization direction, and the first magnetoresistive structure and the Any of the third magnetoresistive structures is a synthetic antiferromagnetic structure. The magnetoresistive stack structure of claim 1, wherein the first spin valve magnetoresistive element further comprises: a second magnetoresistive structure disposed on one side of the first magnetoresistive structure, having a a second magnetization direction, wherein the second magnetization direction changes according to an intensity of an applied magnetic field and an angle between the first magnetization direction, thereby changing a resistance value of the first spin valve magnetoresistive structure. The magnetoresistive stack structure of claim 2, wherein the second spin valve magnetoresistive element further comprises: a fourth magnetoresistive structure disposed on one side of the third magnetoresistive structure, a fourth magnetization direction, wherein the fourth magnetization direction changes due to an applied magnetic field and an angle between the third magnetization direction, thereby changing a resistance value of the second spin valve magnetoresistive structure. The magnetoresistive stack structure of claim 3, wherein the third magnetization direction and the first magnetization direction are in an anti-parallel direction, and the fourth magnetization direction and the second magnetization direction are the same. The magnetoresistive stack structure of claim 3, wherein the third magnetization direction is the same as the first magnetization direction, and the fourth magnetization direction and the second magnetization direction are in an anti-parallel direction. The magnetoresistive stack structure of claim 3, wherein the second magnetoresistive structure and the fourth magnetoresistive structure are any synthetic antiferromagnetic structures. The magnetoresistive stack structure of claim 6, wherein the synthetic antiferromagnetic structure comprises: a first magnetic layer; a second magnetic layer disposed on one side of the first magnetic layer; A coupling layer is disposed between the first magnetic layer and the second magnetic layer. The magnetoresistive stack structure of claim 1, further comprising: a third spin valve magnetoresistive element having an upper surface, a lower surface, and the first magnetization direction fixed, and the first a magnetization direction and the upper surface and the lower surface are parallel to each other; a dielectric layer disposed above the upper surface of the third spin valve magnetoresistive element; and a fourth spin valve magnetoresistive element disposed above the dielectric layer, wherein the third spin The valve magnetoresistive element is electrically connected to the second spin valve magnetoresistive element and the fourth spin valve magnetoresistive element, respectively, and the first spin valve magnetoresistive element and the fourth spin valve magnetoresistive element respectively The second spin valve magnetoresistive element is electrically connected to form a first axial magnetoresistive sensor. The magnetoresistive stack structure of claim 8, wherein the third spin valve magnetoresistive element comprises: the first magnetoresistive structure having the first magnetization direction fixed; a second magnetoresistive structure disposed on one side of the first magnetoresistive structure, having the second magnetization direction, and the second magnetization direction is caused by an applied magnetic field strength and an angle variation between the first magnetization direction And thereby changing a resistance value of the third spin valve magnetoresistive structure. The magnetoresistive stack structure of claim 8, wherein the fourth spin valve magnetoresistive element comprises: the third magnetoresistive structure having a fixed third magnetization direction; and the a fourth magnetoresistive structure disposed on one side of the third magnetoresistive structure, having the fourth magnetization direction, and the fourth magnetization direction is caused by a change in the angle between the third magnetization direction due to the strength of the applied magnetic field, Further, one of the resistance values of the fourth spin valve magnetoresistive structure is changed. The magnetoresistive stack structure according to claim 10, wherein the When the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are the same as the first axial direction, and the first magnetization direction and the third magnetization direction are antiparallel and between the second magnetization direction Clip the corner. The magnetoresistive stack structure of claim 10, wherein when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are perpendicular to the first axis, and the first The magnetization direction is the same as the third magnetization direction and is respectively at a right angle with the second magnetization direction and the fourth magnetization direction. The magnetoresistive stack structure of claim 8, further comprising a fifth spin valve magnetoresistive element, a sixth spin valve magnetoresistive element, a seventh spin valve magnetoresistive element, and an eighth a spin valve magnetoresistive element, wherein the fifth spin valve magnetoresistive element, the sixth spin valve magnetoresistive element, the seventh spin valve magnetoresistive element, and the eighth spin valve magnetoresistive element respectively a first spin valve magnetoresistive element, the second spin valve magnetoresistive element, the third spin valve magnetoresistive element, and the fourth spin valve magnetoresistive element clip at a 90 degree angle, wherein the seventh self The rotary valve magnetoresistive element is electrically connected to the sixth spin valve magnetoresistive element and the eighth spin valve magnetoresistive element, respectively, and the fifth spin valve magnetoresistive element and the eighth spin valve magnetoresistive element respectively The sixth spin valve magnetoresistive element is electrically connected to the second axial magnetoresistive sensor. The magnetoresistive stack structure of claim 13, wherein the fifth spin valve magnetoresistive element and the seventh spin valve magnetoresistive element comprise: the first magnetoresistive structure, which has a fixed And a fifth magnetization direction, wherein the fifth magnetization direction is in the same direction as the first magnetization direction; and the second magnetoresistive structure is disposed on one side of the first magnetoresistive structure, and has a sixth magnetization direction, And the sixth magnetization direction is due to the strength of the applied magnetic field. Generating a change, when the applied magnetic field is zero, the sixth magnetization direction and the second magnetization direction are at a 90 degree angle, and the sixth magnetization direction is caused by an increase in the angle between the fifth magnetization direction due to the strength of the applied magnetic field. And changing a resistance value of the fifth spin valve magnetoresistance and the seventh spin valve magnetoresistive element structure. The magnetoresistive stack structure of claim 13, wherein the sixth spin valve magnetoresistive element and the eighth spin valve magnetoresistive element comprise: the third magnetoresistive structure, which has a fixed And a seventh magnetization direction, wherein the seventh magnetization direction is in the same direction as the third magnetization direction; and the fourth magnetoresistive structure is disposed on one side of the third magnetoresistive structure, and has an eighth magnetization direction, And the eighth magnetization direction changes due to the strength of the applied magnetic field. When the applied magnetic field is zero, the eighth magnetization direction and the fourth magnetization direction are at a 90 degree angle, and the eighth magnetization direction is added. The strength of the magnetic field changes to an angle with the seventh magnetization direction, thereby changing the resistance value of the sixth spin valve magnetoresistance and the eighth spin valve magnetoresistive element structure. The magnetoresistive stack structure of claim 15, wherein when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are the same as the first axial direction, the first magnetization direction and The third magnetization direction is anti-parallel and has an acute angle with the second magnetization direction, and the sixth magnetization direction and the eighth magnetization direction are the same as the second axial direction, the fifth magnetization direction and the first The seven magnetization directions are antiparallel and have an acute angle with the sixth magnetization direction. The magnetoresistive stack structure of claim 15, wherein when the applied magnetic field is zero, the second magnetization direction and the fourth magnetization direction are perpendicular to the first axis, and the first Magnetization direction and the third magnetization direction And an acute angle between the second magnetization direction and the fourth magnetization direction, wherein the sixth magnetization direction and the eighth magnetization direction are perpendicular to the second axis, and the fifth magnetization direction is The seventh magnetization directions are the same and are respectively separated from the sixth magnetization direction and the eighth magnetization direction by an acute angle.