WO2024135038A1 - 磁気センサ、リニアエンコーダ用磁気センサ及び磁気式ロータリーエンコーダ - Google Patents

磁気センサ、リニアエンコーダ用磁気センサ及び磁気式ロータリーエンコーダ Download PDF

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WO2024135038A1
WO2024135038A1 PCT/JP2023/036238 JP2023036238W WO2024135038A1 WO 2024135038 A1 WO2024135038 A1 WO 2024135038A1 JP 2023036238 W JP2023036238 W JP 2023036238W WO 2024135038 A1 WO2024135038 A1 WO 2024135038A1
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layer
tmr element
ferromagnetic
magnetic field
free
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PCT/JP2023/036238
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English (en)
French (fr)
Japanese (ja)
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仁志 岩崎
友也 中谷
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国立研究開発法人物質・材料研究機構
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Publication of WO2024135038A1 publication Critical patent/WO2024135038A1/ja

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/10—Magnetoresistive devices

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  • This disclosure relates to a magnetic sensor, a magnetic sensor for a linear encoder, and a magnetic rotary encoder.
  • a position and rotation detection device using an artificial lattice giant magnetoresistance element has been proposed (see Patent Document 1).
  • An artificial lattice giant magnetoresistance element utilizes the antiparallel magnetic coupling that acts between ferromagnetic layers, so that the magnetization of the adjacent ferromagnetic free layer is arranged in an antiparallel arrangement when no external magnetic field is applied.
  • the magnetization of the ferromagnetic free layer rotates, changing the resistance of the artificial lattice giant magnetoresistance element. This phenomenon is called the giant magnetoresistance (GMR) effect.
  • GMR giant magnetoresistance
  • Magnetic sensors that detect position and rotation use this giant magnetoresistance (GMR) effect.
  • the resistance change rate corresponding to the output value of the sensor is at most about 50%.
  • TMR tunnel magnetoresistance
  • the resistance change rate is defined as (R max -R min )/R min , where R max and R min are the maximum and minimum resistance values of the GMR or TMR element, respectively.
  • FIG. 15 is a configuration block diagram of a bridge-type magnetic sensor according to a first comparative example.
  • the bridge-type magnetic sensor shown in FIG. 15 includes a first TMR element Ref1, a second TMR element Ref2, a third TMR element Ref3, and a fourth TMR element Ref4.
  • the bridge magnetic sensor is connected to a power source E and a ground G.
  • Each of the first TMR element Ref1, the second TMR element Ref2, the third TMR element Ref3, and the fourth TMR element Ref4 is a TMR sensor that uses two free layers.
  • the first TMR element Ref1, the second TMR element Ref2, the third TMR element Ref3, and the fourth TMR element Ref4 are configured to perform bridge operation.
  • the bridge-type magnetic sensor measures the potential difference between the first connection point p1 and the second connection point p2.
  • FIG. 16A is a diagram explaining the operation of each element that constitutes the bridge-type magnetic sensor of FIG. 15, and shows the R-H (magnetic resistance R and applied magnetic field H) characteristics of each of the first TMR element Ref1, second TMR element Ref2, third TMR element Ref3, and fourth TMR element Ref4.
  • FIG. 16A also shows the magnetization directions of the two free layers (first free layer FL1 and second free layer FL2) that constitute each TMR element.
  • FIG. 16B is a diagram explaining the operation of the bridge-type magnetic sensor of FIG. 15, and shows the differential output of a bridge circuit using a first TMR element Ref1, a second TMR element Ref2, a third TMR element Ref3, and a fourth TMR element Ref4.
  • the differential output of the bridge circuit is read by a voltmeter V (see FIG. 15).
  • a TMR element including two free layers used in a bridge-type magnetic sensor exhibits odd function R-H characteristics when a bias magnetic field Hb is applied, as is known for magnetic heads.
  • a positive applied magnetic field H is applied to the TMR element
  • the magnetization of the first free layer FL1 and the second free layer FL2 that make up the TMR element become parallel, decreasing the resistance of the TMR element
  • a negative applied magnetic field H is applied to the TMR element
  • the magnetization of the first free layer FL1 and the second free layer FL2 that make up the TMR element become anti-parallel, increasing the resistance of the TMR element.
  • the differential output ⁇ V of the bridge circuit is nearly zero regardless of the magnetic field.
  • the differential output ⁇ V of the bridge circuit is the potential difference between the first connection point p1 and the second connection point p2. If the differential output ⁇ V of the bridge circuit is zero, it is difficult to detect a magnetic field.
  • FIG 17 is a configuration block diagram of a bridge-type magnetic sensor according to the second comparative example.
  • the bridge-type magnetic sensor according to the second comparative example has a first TMR element Ref1', a second TMR element Ref2', a third TMR element Ref3', and a fourth TMR element Ref4'.
  • Each of the first TMR element Ref1', the second TMR element Ref2', the third TMR element Ref3', and the fourth TMR element Ref4' is a TMR element including a fixed layer PL1, a tunnel barrier layer, and a free layer FL1.
  • the magnetization of the fixed layer PL1 is fixed in the direction of the detection magnetic field H ( ⁇ y direction).
  • the magnetization of the fixed layer PL1 of the first TMR element Ref1' and the fourth TMR element Ref4' is fixed in the same direction (-y direction).
  • the magnetization of the fixed layer PL1 of the second TMR element Ref2' and the third TMR element Ref3' is fixed in the same direction (+y direction).
  • the magnetization of the fixed layer PL1 of the first TMR element Ref1' and the fourth TMR element Ref4' is fixed in the opposite direction to the fixed layer PL1 of the second TMR element Ref2' and the third TMR element Ref3'.
  • FIG. 18A shows the R-H characteristics of the first TMR element Ref1' and the fourth TMR element Ref4' of the bridge-type magnetic sensor of FIG. 17.
  • FIG. 18B shows the R-H characteristics of the second TMR element Ref2' and the third TMR element Ref4' of the bridge-type magnetic sensor of FIG. 17.
  • the first TMR element Ref1' and the fourth TMR element Ref4' have a decreased resistance when a detection magnetic field H in the -y direction is applied, and an increased resistance when a detection magnetic field H in the +y direction is applied.
  • the second TMR element Ref2' and the third TMR element Ref3' have an increased resistance when a detection magnetic field H in the -y direction is applied, and an decreased resistance when a detection magnetic field H in the +y direction is applied.
  • the resistance-magnetic field characteristics of the first TMR element Ref1' and the fourth TMR element Ref4' and the second TMR element Ref2' and the third TMR element Ref3' show opposite tendencies.
  • an external magnetic field H for example, if the potential of the first connection point p1 increases, the potential of the second connection point p2 decreases.
  • the potentials of the first connection point p1 and the second connection point p2 fluctuate in opposite directions, and the difference between them is output as the output voltage ⁇ V (detection voltage).
  • the magnetization direction of the fixed layer PL1 is inverted between the first TMR element Ref1' and the fourth TMR element Ref4' and the second TMR element Ref2' and the third TMR element Ref3', thereby inverting the polarity of the inclination direction of the R-H characteristics between the first TMR element Ref1' and the fourth TMR element Ref4' and the second TMR element Ref2' and the third TMR element Ref3'.
  • the bridge-type magnetic sensor shown in FIG. 17 solves the problem that the output is offset when the potential of the first connection point p1 and the potential of the second connection point p2 become the same.
  • Patent Document 2 describes the formation of a hard bias laminate.
  • a bridge-type magnetic sensor including the bridge circuit shown in FIG. 15 applies a bias magnetic field Hb in the same direction to all TMR elements.
  • Hb bias magnetic field
  • the differential output ⁇ V between the first connection point p1 and the second connection point p2 is nearly zero, regardless of the magnetic field. Therefore, a bridge-type magnetic sensor including the bridge circuit shown in FIG. 15 has the problem that it is difficult to detect a magnetic field.
  • the bridge-type magnetic sensor shown in FIG. 17 reverses the polarity of the inclination direction of the R-H characteristics by changing the pinning direction of the magnetization of the fixed layer PL1 between the first TMR element Ref1' and the fourth TMR element Ref4' and the second TMR element Ref2' and the third TMR element Ref3'. Therefore, the bridge-type magnetic sensor shown in FIG. 17 solves the problem that the differential output ⁇ V between the first connection point p1 and the second connection point p2 is canceled out and becomes zero.
  • the greater the signal output the more resistance to noise is required, so there is a demand for a further increase in the differential output ⁇ V.
  • the present disclosure aims to solve these problems by providing a magnetic sensor that can obtain a larger differential output ⁇ V by using a bridge-type magnetic sensor that uses four TMR sensors with two free layers.
  • the TMR element used in the bridge-type magnetic sensor shown in Figure 17 has one free layer FL1.
  • a TMR element using two free layers FL1, FL2 has twice the amount of resistance change (angle between the two magnetic layers) when the same magnetic field is applied to the element compared to a TMR element using one free layer FL1. Therefore, the inventors have discovered a configuration that uses a TMR element with two free layers FL1, FL2 and can obtain a high differential output.
  • a magnetic sensor includes a bridge circuit and a magnetic field applying unit.
  • the bridge circuit includes a first TMR element, a second TMR element, a third TMR element, and a fourth TMR element.
  • Each of the first TMR element, the second TMR element, the third TMR element, and the fourth TMR element includes a magnetic junction including a first free layer including a ferromagnetic material, a second free layer including a ferromagnetic material, and an insulating layer sandwiched between the first free layer and the second free layer.
  • a first end of the first TMR element and a first end of the third TMR element are connected to a high potential terminal.
  • a second end of the second TMR element and a second end of the fourth TMR element are connected to a low potential terminal having a lower potential than the high potential terminal.
  • a second end of the first TMR element and a first end of the second TMR element are connected to each other by a first connection point.
  • a second end of the third TMR element and a first end of the fourth TMR element are connected to each other by a second connection point.
  • the bridge circuit measures a potential difference between the first connection point and the second connection point.
  • the magnetic field application unit applies a bias magnetic field in a first direction to the first TMR element and the fourth TMR element, and applies a bias magnetic field in a second direction to the second TMR element and the third TMR element.
  • the first direction and the second direction are opposite to each other.
  • the free layer means a magnetic layer whose magnetization rotates with respect to a detection magnetic field.
  • the magnetic field application unit may include a first hard bias body that applies a first bias magnetic field in the detection magnetic field flow direction of the first TMR element, a second hard bias body that applies a second bias magnetic field in the detection magnetic field flow direction of the second TMR element, a third hard bias body that applies a third bias magnetic field in the detection magnetic field flow direction of the third TMR element, and a fourth hard bias body that applies a fourth bias magnetic field in the detection magnetic field flow direction of the fourth TMR element.
  • the magnetic field application section may have a power supply and a wiring connected to the power supply.
  • the wiring has a portion overlapping with each of the first TMR element, the second TMR element, the third TMR element, and the fourth TMR element.
  • the current flow direction of the first overlapping portion where the first TMR element and the wiring overlap is the same as that of the wiring in the fourth overlapping portion where the fourth TMR element and the wiring overlap.
  • the current flow direction of the wiring in the second overlapping portion where the second TMR element and the wiring overlap is the same as that of the wiring in the third overlapping portion where the third TMR element and the wiring overlap.
  • the current flow direction in the first overlapping portion and the fourth overlapping portion is opposite to that in the second overlapping portion and the third overlapping portion.
  • the change in the total resistance of the bridge circuit between the high potential terminal and the low potential terminal when an external magnetic field is applied may be smaller than the change in resistance of each of the first TMR element, the second TMR element, the third TMR element, and the fourth TMR element.
  • the change in the overall resistance of the bridge circuit will be zero.
  • the overall resistance of the bridge circuit will change slightly. If the amount of change in the overall resistance of the bridge circuit is smaller than the amount of resistance change of each TMR element, the element variation of each TMR element is within the acceptable range. If the element variation of each TMR element is sufficiently small, the amount of change in the overall resistance of the bridge circuit will be sufficiently smaller than the amount of resistance change of each TMR element.
  • the first bias magnetic field is preferably applied to the first TMR element so that the resistance value of the first TMR element is intermediate between the maximum resistance and the minimum resistance
  • the second bias magnetic field is preferably applied to the second TMR element so that the resistance value of the second TMR element is intermediate between the maximum resistance and the minimum resistance
  • the third bias magnetic field is preferably applied to the third TMR element so that the resistance value of the third TMR element is intermediate between the maximum resistance and the minimum resistance
  • the fourth bias magnetic field is preferably applied to the fourth TMR element so that the resistance value of the fourth TMR element is intermediate between the maximum resistance and the minimum resistance.
  • the insulating layer may have at least one type selected from the group consisting of MgO, Mg-Al - O, and Al2O3 , and the first free layer and the second free layer may have at least a layer made of CoFeB.
  • At least one of the first free layer and the second free layer may be a laminate including a plurality of layers.
  • the laminate includes a layer of CoFeB, a layer of CoFe, and a central layer.
  • the layer of CoFe is located farther from the tunnel barrier layer than the layer of CoFeB, and the central layer is located between the layer of CoFeB and the layer of CoFe, and includes any one selected from the group consisting of NiFe, CoFeSiB, and CoFeBTa.
  • the layer made of CoFe is provided to improve magnetic coupling
  • the central layer is provided to improve soft magnetic properties.
  • the first TMR element, the second TMR element, the third TMR element, and the fourth TMR element may have the following stacked structure.
  • the laminated structure is: [ferromagnetic layer A i /coupling layer A i ] n /ferromagnetic layer A n+1 /intermediate layer A /the first free layer /insulating layer /the second free layer /intermediate layer B /[ferromagnetic layer B j /coupling layer B j ] n+1 /ferromagnetic layer B n+2 / Or, [ferromagnetic layer A j / coupling layer A j ] n+1 / ferromagnetic layer A n+2 / intermediate layer A / the first free layer / insulating layer / the second free layer / intermediate layer B / [ferromagnetic layer B i / coupling layer B i ] n / ferromagnetic layer B n
  • the ferromagnetic layer A i , the ferromagnetic layer A n+1 , the ferromagnetic layer B j , the ferromagnetic layer B n+2 , the ferromagnetic layer A j and the ferromagnetic layer B i may be CoFe
  • the coupling layer A i , the coupling layer B j , the coupling layer A j and the coupling layer B i may be Ru
  • the intermediate layer A and the intermediate layer B may have at least one selected from the group consisting of Cu, Ag, Cr, Ru and AgSn
  • the insulating layer may have at least one selected from the group consisting of MgO, Mg—Al—O and Al 2 O 3
  • the first free layer and the second free layer may have a layer made of at least CoFeB.
  • the first TMR element, the second TMR element, the third TMR element, and the fourth TMR element may have the following stacked structure.
  • the laminated structure is a first antiferromagnetic layer/a first ferromagnetic layer/a first exchange coupling layer/the first free layer/the insulating layer/the second free layer/a second exchange coupling layer/a second ferromagnetic layer/a second antiferromagnetic layer/ It has a laminated structure.
  • the first exchange coupling layer and the second exchange coupling layer may be Ru or Cr, and one of the magnetic coupling between the first ferromagnetic layer and the first free layer and the magnetic coupling between the second ferromagnetic layer and the second free layer may be antiferromagnetic coupling and the other may be ferromagnetic coupling.
  • the magnetic coupling between the first ferromagnetic layer and the first free layer and the magnetic coupling between the second ferromagnetic layer and the second free layer can be either antiferromagnetic coupling or ferromagnetic coupling by changing the film thickness of the first exchange coupling layer or the second exchange coupling layer.
  • the first antiferromagnetic layer and the second antiferromagnetic layer may be at least one of IrMn, PtMn, FeMn, and NiMn
  • the first ferromagnetic layer and the second ferromagnetic layer may be CoFe
  • the first exchange coupling layer and the second exchange coupling layer may be Ru
  • the insulating layer may include any one selected from the group consisting of MgO, Mg—Al—O, and Al 2 O 3
  • the first free layer and the second free layer may have a layer made of at least CoFeB.
  • the first TMR element, the second TMR element, the third TMR element, and the fourth TMR element may have the following stacked structure.
  • the laminated structure is an antiferromagnetic layer A/dust layer A/[ferromagnetic layer A i /coupling layer A i ] n /the first free layer/the insulating layer/the second free layer/[coupling layer B j /ferromagnetic layer B j ] n+1 /dust layer B/antiferromagnetic layer B/ Or, Antiferromagnetic layer A/dust layer A/[ferromagnetic layer A j /coupling layer A j ] n+1 /first free layer/insulating layer/second free layer/[coupling layer B i /ferromagnetic layer B i ] n /dust layer B/antiferromagnetic layer B/
  • the laminated structure is represented by the following formula:
  • n is an integer equal to or greater than 0
  • the antiferromagnetic layer A and the antiferromagnetic layer B may have at least one selected from the group consisting of IrMn, PtMn, FeMn and NiMn
  • the ferromagnetic layer A i , the ferromagnetic layer B j , the ferromagnetic layer A j and the ferromagnetic layer B i may be CoFe
  • the coupling layer A i , the coupling layer B j , the coupling layer A j and the coupling layer B i may be Ru
  • the dust layer A and the dust layer B may be Ru with a thickness of 1 nm or less
  • the insulating layer may have at least one selected from the group consisting of MgO, Mg—Al—O and Al 2 O 3
  • the first free layer and the second free layer may have a layer made of at least CoFeB.
  • the laminated structure may be located between a first structure consisting of a substrate/lower electrode/underlayer/antiferromagnetic layer and a second structure consisting of an antiferromagnetic layer/cap layer.
  • the laminated structure may be located between a third structure consisting of a substrate/lower electrode/underlayer and a fourth structure consisting of a cap layer.
  • the substrate is a silicon wafer or a ceramic wafer made of AlTiC or aluminum oxide
  • the underlayer is a laminated structure of Ta and Ru
  • the antiferromagnetic layer is any one selected from the group consisting of IrMn, PtMn, FeMn, and NiMn
  • the cap layer may be Ru.
  • the magnetic sensor for a linear encoder according to the second aspect has the magnetic sensor according to the above aspect.
  • the magnetic rotary encoder according to the third aspect has the magnetic sensor according to the above aspect.
  • the magnetic sensor disclosed herein can apply a bias magnetic field in a predetermined direction to each of the first to fourth TMR elements.
  • a large differential output ⁇ V can be obtained.
  • the magnetic sensor disclosed herein uses two free layers, so the angle change between the free layers due to the detection magnetic field is doubled, and a signal output is doubled.
  • FIG. 1 shows a circuit configuration diagram of a bridge-type magnetic sensor according to a first embodiment
  • 2 is a cross-sectional view showing an example of a laminated structure of a TMR element used in the bridge-type magnetic sensor according to the first embodiment.
  • FIG. 2 is a cross-sectional view showing an example of a laminated structure of a TMR element and a hard bias body used in the bridge-type magnetic sensor according to the first embodiment.
  • FIG. RH characteristics of the second and third TMR elements are shown.
  • RH characteristics of the first and fourth TMR elements are shown.
  • FIG. 13 is a diagram showing the difference in R-H characteristics between a TMR element used in the bridge-type magnetic sensor according to the first embodiment (wherein the ferromagnetic layers sandwiching the insulating layer are both free layers FL1 and FL2) and a TMR element used in the bridge-type magnetic sensor according to the second comparative example (wherein the ferromagnetic layers sandwiching the insulating layer are the free layer FL1 and the fixed layer PL1).
  • 1 is a diagram showing the magnetization arrangement and resistance magnetic field characteristics of the TMR element according to the first embodiment, and also shows the magnetization direction of the free layer in three typical types of magnetization modes.
  • FIG. 1 is a cross-sectional view of an example of a laminate structure (a second example of a first laminate type (n ⁇ 1)) that can be used in the TMR element according to the first embodiment.
  • 1 is a cross-sectional view of an example of a laminate structure (a first example of a second laminate type (n ⁇ 1)) that can be used in the TMR element according to the first embodiment.
  • FIG. 1 is a cross-sectional view of an example of a laminate structure (a second example (n ⁇ 1) of another type of the first laminate type) that can be used in the TMR element according to the first embodiment.
  • 1 is a cross-sectional view of an example of a laminate structure (a first example (n ⁇ 1) of another type of the second laminate type) that can be used in the TMR element according to the first embodiment.
  • 1 is a cross-sectional view of a laminate structure (third laminate type) that can be applied to the TMR element according to the first embodiment.
  • FIG. 1 is a
  • FIG. 11 is a cross-sectional view of a laminated structure (a second example of a fourth laminated type (n ⁇ 1)) that can be used in the TMR element according to the first embodiment.
  • FIG. 1 is a cross-sectional view of a stacked structure (fifth stacked type (n ⁇ 1)) that can be used in the TMR element according to the first embodiment.
  • FIG. 2 is a diagram showing an example of a laminated structure of a TMR sensor.
  • FIG. 1 is a graph showing the resistance-magnetic field curve of a first type of laminate having the laminate structure shown in Table 1, which is an embodiment of the present invention.
  • the dashed and solid lines represent combinations of different thicknesses of intermediate layer A and intermediate layer B.
  • FIG. 13 is a diagram showing the relationship between the intermediate layer thickness and the soft pinning magnetic field strength Hpin of the free layer in various stacked configurations.
  • FIG. 13 is a plan view of a bridge-type magnetic sensor in which a plurality of TMR elements connected in series form one TMR element group, and four TMR element groups are arranged in parallel.
  • FIG. 13B is a side view of the TMR element group shown in FIG. 13A.
  • 1 is a perspective view of a configuration of a magnetic linear encoder to which a magnetic sensor according to an embodiment of the present invention is applied; 1 is a configuration diagram of a magnetic rotary encoder to which a magnetic sensor according to an embodiment of the present invention is applied.
  • FIG. 11 is a configuration block diagram of a bridge-type magnetic sensor according to a first comparative example, in which a magnetic field Hb in the same direction is applied to each of a first TMR element Ref1, a second TMR element Ref2, a third TMR element Ref3, and a fourth TMR element Ref4.
  • FIG. 15 shows the RH characteristics of the TMR element of the bridge-type magnetic sensor.
  • FIG. 16 is a diagram showing a differential output of the bridge-type magnetic sensor shown in FIG. 15 .
  • FIG. 2 is a configuration block diagram of a bridge-type magnetic sensor according to a first comparative example.
  • FIG. 17 shows the R-H characteristics of the first TMR element Ref1' and the fourth TMR element Ref4'.
  • FIG. 17 shows the R-H characteristics of the second TMR element Ref2' and the third TMR element Ref3'.
  • FIG. 13 shows a circuit configuration diagram of a bridge-type magnetic sensor according to a second embodiment. 13 is a diagram showing the orientation directions of magnetization of a first free layer FL1 and a second free layer FL2 of each TMR element of a magnetic sensor according to a second embodiment.
  • FIG. 10A to 10C are schematic diagrams for explaining the operation of the bridge-type magnetic sensor according to the second embodiment.
  • FIG. 11 is a circuit configuration diagram of a modified example of the bridge-type magnetic sensor according to the second embodiment.
  • FIG. 1 is a configuration diagram of a bridge-type magnetic sensor according to the first embodiment.
  • the bridge-type magnetic sensor according to the first embodiment comprises a first TMR element 1, a second TMR element 2, a third TMR element 3, and a fourth TMR element 4. As shown in FIG. 1, the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 are bridge-connected.
  • the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 form a bridge circuit.
  • a first end of the first TMR element 1 and a first end of the third TMR element 3 are connected to a high potential terminal t1.
  • the high potential terminal t1 is connected, for example, to a power supply E.
  • a second end of the second TMR element 2 and a second end of the fourth TMR element 4 are connected to a low potential terminal t2.
  • the low potential terminal t2 is at a lower potential than the high potential terminal t1.
  • the low potential terminal t2 is connected, for example, to ground G.
  • the second end of the first TMR element 1 and the first end of the second TMR element 2 are connected to each other by a first connection point p1.
  • the second end of the third TMR element 3 and the first end of the fourth TMR element 4 are connected to each other by a second connection point p2.
  • the bridge circuit measures the potential difference between the first connection point p1 and the second connection point p2. The potential difference is measured, for example, by a voltmeter V.
  • Hard bias bodies are arranged near the side of each element in the direction of the detection magnetic field (y direction).
  • a pair of first hard bias bodies HB1 are located on the sides of the first TMR element 1.
  • a pair of second hard bias bodies HB2 are located on the sides of the second TMR element 2.
  • a pair of third hard bias bodies HB3 are located on the sides of the third TMR element 3.
  • a pair of fourth hard bias bodies HB4 are located on the sides of the fourth TMR element 4.
  • the first hard bias body HB1, the second hard bias body HB2, the third hard bias body HB3, and the fourth hard bias body HB4 correspond to the magnetic field application section.
  • the magnetization of each free layer of the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element is aligned along the ⁇ x direction when there is no bias magnetic field.
  • the first hard bias body HB1 applies a first bias magnetic field in the direction of the detection magnetic field flow ( ⁇ y direction) of the first TMR element 1.
  • the second hard bias body HB2 applies a second bias magnetic field in the direction of the detection magnetic field flow ( ⁇ y direction) of the second TMR element 2.
  • the third hard bias body HB3 applies a third bias magnetic field in the direction of the detection magnetic field flow ( ⁇ y direction) of the third TMR element 3.
  • the fourth hard bias body HB4 applies a fourth bias magnetic field in the direction of the detection magnetic field flow ( ⁇ y direction) of the fourth TMR element 4.
  • a bias magnetic field is applied to the first TMR element 1 and the fourth TMR element 4 in the first direction (-y direction).
  • a bias magnetic field is applied to the second TMR element 2 and the third TMR element 3 in the second direction (+y direction).
  • the first and second directions are 180 degrees opposite to each other and are in opposite directions.
  • the direction in which the bias magnetic field is applied varies depending on the magnetization direction of the hard bias body.
  • the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 are separated from the bridge-type sensor, and a magnetic field sufficiently larger than the coercive force of each hard bias body is applied. This magnetic field magnetizes the magnetization direction of each hard bias body in the specified direction. Then, by connecting each TMR element in a bridge as shown in Figure 1, magnetic fields in opposite directions can be applied to the first TMR element 1 and the fourth TMR element 4, and the second TMR element 2 and the third TMR element 3.
  • the hard bias body is, for example, a hard bias laminate.
  • Figure 2B shows an example of a hard bias laminate.
  • the hard bias stack can be deposited, for example, using ion beam deposition (IBD), in which an ion beam is directed at a target.
  • IBD ion beam deposition
  • the sputtered particles emitted from the target are highly directional when they reach the device substrate. By controlling the gas pressure, the directionality of the sputtered particles can be somewhat controlled.
  • the hard bias stack can be applied near each TMR element using a bulk hard material.
  • the hard bias stack includes, for example, an underlayer 121 and a magnetic layer 122.
  • the underlayer 121 is, for example, Cr or an alloy thereof.
  • the magnetic layer 122 is, for example, a CoCrPt alloy or a CoPt alloy capable of generating high coercivity and residual magnetization.
  • a high coercivity of more than 160 kA/m (2000 Oe) is required.
  • a larger bias field can be obtained when the residual magnetization of the ferromagnetic material is high.
  • the crystal orientation of the Cr underlayer is usually (110), and that of the magnetic layer is (100).
  • the c-axis of the Co alloy is randomly oriented, but in most cases lies parallel to the substrate surface.
  • the layers constituting the magnetoresistive element are first deposited and then patterned to obtain the element.
  • a current tunnel magnetoresistive (TMR) element the layers constituting the TMR element are first deposited and then patterned using common lithography techniques.
  • An insulating layer such as Al 2 O 3 , SiO 2 , or Si-N is then deposited on the sidewalls 100b, 100c of the patterned TMR element and on the field region 124 exposed by patterning.
  • a photoresist structure is provided so that no deposition is performed on the top of the TMR element.
  • the insulating layer 119 can be formed on the sidewalls of the patterned TMR element by, for example, sputtering, atomic layer deposition (ALD), or chemical vapor deposition (CVD).
  • a hard bias stack is formed near the junction wall (insulating layer 119 attached to the sidewall of the TMR element) and in contact with the insulating layer 119 deposited in the field region.
  • a Cr underlayer 121 and a magnetic layer 122 are deposited at different incidence angles to achieve the desired hard bias stack shape.
  • the target sizes used in IBD techniques tend to be very large to achieve sufficient uniformity across the wafer. Deposition rates are low and optimization is complex as the incidence angle (for the magnetic layer) affects important magnetic properties such as coercivity.
  • FIG. 2A is a diagram showing an example of the stacked structure of a TMR element
  • FIG. 2B is a cross-sectional view of a TMR element with negative bias bodies provided on both sides. Note that for the sake of explanation, FIGS. 2A and 2B show the junction walls (part of insulating layer 119) as vertical for simplicity's sake, but if the TMR element has a trapezoidal inclination, the junction walls may also be inclined.
  • FIG. 2A is a diagram showing an example of a layered structure of a TMR element applied to the bridge-type magnetic sensor according to the first embodiment.
  • the magnetoresistance element 100 shown in FIG. 2A has a layered structure represented by underlayer 100a/antiferromagnetic layer 101/ferromagnetic layer 102/coupling layer 103/first free layer 104/tunnel barrier layer 105/second free layer 106/coupling layer 107/ferromagnetic layer 108/antiferromagnetic layer 109/cap layer 110.
  • “/" indicates the layered interface of each layer, and the layers are layered in this order with "/" between them.
  • the magnetoresistance element 100 is an example of a TMR element applied to a bridge-type magnetic sensor, and the first free layer 104 corresponds to the first free layer, the second free layer 106 corresponds to the second free layer, and the tunnel barrier layer 105 corresponds to the insulating layer.
  • the magnetizations of the first free layer 104 and the second free layer 106 are aligned antiparallel in the x direction.
  • the antiparallel alignment is achieved by using the antiferromagnetic layers 101 and 109 and the coupling layers 103 and 107.
  • FIGS. 2A and 2B are schematic diagrams showing a TMR element and a hard bias body used in a bridge-type magnetic sensor according to this embodiment.
  • the magnetic sensor stack 130 corresponds to the combination of a TMR element and a hard bias body in a bridge-type magnetic sensor.
  • the magnetic sensor stack 130 has a magnetoresistance element 100 at approximately the center of the bottom nonmagnetic electrode layer 125 serving as a substrate.
  • the magnetoresistance element 100 is made of multiple laminated films with different compositions, and its electrical resistance value changes when a magnetic field is applied.
  • the magnetic sensor stack 130 also has a hard bias stack 120 at the top of the field region 124 on either side of the two opposing side walls 100b, 100c of the magnetoresistance element 100.
  • the hard bias stack 120 can apply a bias magnetic field to the magnetoresistance element 100.
  • the magnetoresistance element 100 illustrated in FIG. 2A is a magnetic tunnel junction (MTJ) that includes an oxide barrier layer (MgO) as a tunnel barrier layer 105 directly below the second free layer 106.
  • MTJ magnetic tunnel junction
  • MgO oxide barrier layer
  • the magnetoresistance element 100 is layered on a non-magnetic electrode 125 made of, for example, Cu.
  • the magnetoresistance element 100 mainly includes an antiferromagnetic layer 101, a ferromagnetic layer 102, a first free layer 104, a tunnel barrier layer 105, and a second free layer 106.
  • the magnetoresistance element 100 may also have an underlayer 100a.
  • the underlayer 100a is between the nonmagnetic electrode 125 and the antiferromagnetic layer 101.
  • the underlayer 100a may have a two-layer structure, for example, a lower underlayer made of Ta or the like and an upper underlayer made of Ru or the like.
  • the antiferromagnetic layer 101 is, for example, an antiferromagnetic material such as IrMn.
  • the antiferromagnetic layer 101 is, for example, stacked on the nonmagnetic electrode 125, with an underlayer 100a interposed between them as necessary.
  • the magnetoresistance element 100 may also have an antiferromagnetic layer 109.
  • the antiferromagnetic layer 109 is formed of an antiferromagnetic material such as IrMn.
  • the antiferromagnetic layer 109 is stacked on the ferromagnetic layer 108, for example.
  • the ferromagnetic layer 102 is, for example, CoFe, and is a material whose magnetization is easily pinned by the antiferromagnetic layer 101.
  • the magnetoresistance element 100 may also have an antiferromagnetic layer 108.
  • the ferromagnetic layer 108 is, for example, CoFe, and is a material whose magnetization is easily pinned by the antiferromagnetic layer 109.
  • the magnetoresistance element 100 may also have coupling layers 103 and 107.
  • the coupling layer 103 is made of a material such as Ru, Cr, Ir, or Rh, which has a property that the interlayer coupling between the ferromagnetic layer 102 and the first free layer 104 changes between antiferromagnetic coupling and ferromagnetic coupling depending on the thickness.
  • the coupling layer 107 is made of a material such as Ru, Cr, Ir, or Rh, which has a property that the interlayer coupling between the ferromagnetic layer 108 and the second free layer 106 changes between antiferromagnetic coupling and ferromagnetic coupling depending on the thickness.
  • a thickness that results in antiferromagnetic coupling is used for the coupling layer 103
  • a thickness that results in ferromagnetic coupling is used for the coupling layer 107.
  • a thickness that results in antiferromagnetic coupling is used for the coupling layer 107.
  • the first free layer 104 includes a ferromagnetic material.
  • the first free layer 104 may be made of, for example, CoFeB, but is not limited to this.
  • the tunnel barrier layer 105 is made of a non-magnetic layer or a tunnel insulator layer, and is formed of, for example, an oxide layer such as MgO.
  • the tunnel barrier layer 105 may use at least one of Mg-Al-O and Al 2 O 3 instead of MgO.
  • the first free layer 106 may also be a laminate including multiple layers.
  • the laminate may have a CoFeB layer, a CoFe layer, and a central layer.
  • the CoFeB layer is, for example, disposed on the tunnel barrier layer 105 side.
  • the CoFe layer is disposed at a position farther away from the tunnel barrier layer 105 than the CoFeB layer.
  • the central layer is disposed between the CoFeB layer and the CoFe layer.
  • NiFe, CoFeSiB, CoFeBTa, or the like, which have excellent soft magnetic properties, is used for the central layer.
  • the second free layer 106 is formed of, for example, a ferromagnetic material such as CoFeB, and may be a layer in which a Ta layer and a NiFe layer are laminated on a ferromagnetic material layer such as CoFeB.
  • the second free layer 106 may also have a laminate similar to that of the first free layer 104.
  • the magnetization of the second free layer 106 is in an intermediate resistance state between the lowest resistance state and the highest resistance state of the magnetoresistance element 100.
  • the lowest resistance state of the magnetoresistance element 100 is a state in which the magnetization of the first free layer 104 and the magnetization of the second free layer 106 are arranged in a parallel arrangement.
  • the highest resistance state of the magnetoresistance element 100 is a state in which the magnetization of the first free layer 104 and the magnetization of the second free layer 106 are arranged in an anti-parallel arrangement.
  • the magnetization of the second free layer 106 is set to an intermediate resistance state in which the gradient of the magnetic field-resistance characteristic is the steepest.
  • the bias magnetic field is also called a "hard bias” and prevents magnetic domains from being formed in the second free layer 106.
  • the magnetoresistance change of the magnetoresistance element 100 is determined by the relative orientation of the magnetization between the first free layer 104 and the second free layer 106.
  • the magnetoresistance element 100 may have a cap layer 110.
  • the cap layer 110 is selected from, for example, Cr, Ru, Ta, Ti and alloys thereof, and C, as required.
  • the cap layer 110 covers the antiferromagnetic layer 109.
  • the hard bias stack 120 is deposited on the field region 124 of the non-magnetic electrode 125.
  • the hard bias stack 120 has an underlayer 121 and a magnetic layer 122.
  • the magnetic layer 122 is formed of an alloy (permanent magnet) having a hexagonal crystal structure (hcp) selected from a group of alloys containing Co and Pt, such as Co-Pt and Co-Cr-Pt.
  • the magnetic layer 122 is laminated on the non-magnetic electrode 125 via the underlayer 121.
  • the underlayer 121 is formed of an alloy having a body-centered cubic (bcc) structure selected from, for example, Cr, Cr-Mo, Cr-Ti, Nb, Ta, W, and alloys thereof.
  • the underlayer 121 has a thickness of, for example, 3 to 7 nm on the field region 124 and less than 3 nm on the side walls 100b and 100c.
  • a seed layer (not shown) may be further provided on the underlayer 121 to form a double underlayer. That is, a seed layer selected from, for example, CrB, CrTiB, MgO, Ru, Ta, Ti, and alloys thereof may be further formed on the field region 124 and the sidewalls 100b, 100c of the magnetoresistive element stack 100. This seed layer has, for example, a thickness of less than 1 nm on the field region 124 and a thickness of 0.5 to 2 nm on the sidewalls 100b, 100c.
  • the magnetic layer 122 may be covered with a capping layer 123.
  • the capping layer 123 may include, for example, any one selected from Cr, Mo, Nb, Ru, Ta, Ti, V, and W or alloys thereof.
  • An insulating layer 119 is disposed between the capping layer 123 and the nonmagnetic electrode 126.
  • An insulating layer 119 is disposed under the magnetic layer 122 and on the sidewalls 100b, 100c of the magnetoresistive element 100.
  • the insulating layer 119 is made of, for example, Al 2 O 3 , SiO 2 , Si—N, HfO 2 or a combination thereof.
  • the insulating layer 119 separates the magnetoresistive element 100 (TMR element) and the hard bias stack 120 (hard bias) by a distance of several microns to several hundred microns, for example, on the field region 124.
  • the magnetic sensor stack 130 includes a non-magnetic electrode 125 under the underlayer 100a and a non-magnetic electrode 126 on the capping layer 123.
  • the non-magnetic electrodes 125 and 126 are, for example, Cu.
  • the magnetoresistance element 100 is sandwiched between the two thick non-magnetic electrodes 125 and 126.
  • each layer constituting the magnetoresistance element 100 is deposited on the nonmagnetic electrode 125.
  • a photoresist (PR) mask is applied, patterned, and developed to form the magnetoresistance element 100.
  • the nonmagnetic electrode 125 is, for example, a nonmagnetic electrode made of Cu or the like.
  • the photoresist mask (not shown) is used to mask a portion of the stack that will become the magnetoresistance element 100 during the etching process.
  • the etching process may be performed by, for example, ion beam etching (IBE) or reactive ion etching (RIE).
  • IBE ion beam etching
  • RIE reactive ion etching
  • a hard mask may be formed on the stack that will become the magnetoresistance element 100.
  • the photoresist mask is first used to form the hard mask, and is removed by an oxygen ashing process before etching to form the magnetoresistance element 100.
  • the magnetoresistive element 100 and its side walls 100b, 100c are coated with an insulating layer 119.
  • the insulating layer 119 is preferably an oxide insulator (3-5 nm) such as Al2O3 or SiO2 .
  • the insulating layer 119 can be formed by any of the deposition methods such as physical vapor deposition (PVD), ion beam deposition (IBD), atomic layer deposition (ALD) and chemical vapor deposition (CVD). ALD and CVD methods allow conformal deposition.
  • the hard bias stack 120 is deposited on the insulating layer 119.
  • the underlayer 121 is deposited on the insulating layer 119, followed by the magnetic layer 122 and the capping layer 123.
  • Method for forming magnetoresistance element 100 A method for forming the magnetoresistive element 100 will now be described. First, a laminate for a magnetoresistive element is formed on a wafer, and then a photoresist is formed thereon, developed, and patterned.
  • an ion beam is used to etch the portions of the magnetoresistance element stack that are not covered by resist.
  • the angle of incidence of the beam By varying the angle of incidence of the beam, the shape of the sidewalls 100b, 100c of the magnetoresistance element 100 can be controlled. With nearly perpendicular incidence, the sidewalls 100b, 100c are skirt-like, narrow at the top and widening toward the bottom layer. By aiming the ion beam at a sharper angle, the sidewalls 100b, 100c can be made more vertical and less flared at the bottom, resulting in nearly vertical sidewalls 100b, 100c.
  • An insulating layer 119 for example selected from Al 2 O 3 , SiO 2 , Si--N, HfO 2 or combinations thereof, is then deposited to electrically insulate the sidewalls 100b, 100c.
  • the deposition of the insulating layer 119 can be done by physical vapor deposition (PVD). However, since thickness control of the insulating layer 119 on the sidewalls 100b, 100c is critical, more suitable deposition techniques such as, for example, ion beam deposition (IBD) or atomic layer deposition (ALD) are preferred.
  • PVD physical vapor deposition
  • IBD ion beam deposition
  • ALD atomic layer deposition
  • the hard bias laminate is formed.
  • a hard bias laminate formation device using ionized physical vapor deposition as disclosed in Patent Document 2, for example. This makes it possible to obtain a magnetic sensor laminate with high coercivity, a good hard bias laminate, and high sensitivity.
  • FIG. 3A shows the R-H characteristics of the second TMR element 2 and third TMR element 3 of the bridge-type magnetic sensor.
  • Figure 3B shows the R-H characteristics of the first TMR element 1 and fourth TMR element 4 of the bridge-type magnetic sensor.
  • H 0 as the reference point
  • the R-H characteristics of the second TMR element 2 and third TMR element 3 and the first TMR element 1 and fourth TMR element 4 are inverted depending on the direction of the bias magnetic field applied from the hard bias body.
  • the differential output ⁇ V from the bridge-type magnetic sensor increases.
  • FIG. 4 is a diagram showing the difference in R-H characteristics between a TMR element used in the bridge-type magnetic sensor according to the first embodiment (wherein the ferromagnetic layers sandwiching the insulating layer are both free layers FL1 and FL2) and a TMR element used in the bridge-type magnetic sensor according to the second comparative example (wherein the ferromagnetic layers sandwiching the insulating layer are the free layer FL1 and the fixed layer PL1).
  • each TMR element has two free layers FL1 and FL2 (first free layer 104 and second free layer 106).
  • the magnetization of each of the two free layers rotates due to the bias magnetic field, and the relative angle between the magnetizations of the two free layers changes significantly.
  • the TMR element used in the bridge-type magnetic sensor of the second comparative example has a free layer FL1 and a fixed layer PL1.
  • the magnetization of the free layer FL1 rotates due to a bias magnetic field, but the magnetization of the fixed layer PL1 remains fixed even when a bias magnetic field is applied. Therefore, the change in the relative angle between the magnetization of the free layer FL1 and the magnetization of the fixed layer PL1 is smaller than the change in the relative angle between the magnetizations of the two free layers.
  • the resistance of the TMR element changes depending on the relative angle between the magnetizations of the two ferromagnetic elements.
  • the bridge-type magnetic sensor according to the first embodiment has a larger amount of resistance change in each TMR element that makes up the magnetic sensor than the bridge-type magnetic sensor according to the second comparative example, and therefore produces twice the signal output.
  • the dual free type TMR element is basically a three-layer structure of a first free layer 104 (ferromagnetic metal), a tunnel barrier layer 105 (insulating oxide), and a second free layer 106 (ferromagnetic metal).
  • the tunnel barrier layer 105 magnetically separates the first free layer 104 and the second free layer 106.
  • the dual free type TMR element also exhibits a tunnel magnetoresistance effect. When a voltage is applied between the first free layer 104 and the second free layer 106, the resistance value of the dual free type TMR element changes depending on the relative angle of the magnetization of the first free layer 104 and the second free layer 106. Whether the magnetic characteristic of the TMR element shows an even function characteristic or an odd function characteristic is determined by the presence or absence of a hard bias body.
  • the dual free type TMR element has a first free layer 11, a tunnel barrier layer 12, and a second free layer 13, as shown in, for example, (A) to (C) of Figure 5.
  • the tunnel barrier layer 12 is sandwiched between the first free layer 11 and the second free layer 13.
  • the first free layer 11 corresponds to the first free layer 104 described above
  • the second free layer 13 corresponds to the second free layer 106 described above
  • the tunnel barrier layer 12 corresponds to the tunnel barrier layer 105 described above.
  • the first free layer 11 and the second free layer 13 are ferromagnetic layers, preferably, but not limited to, CoFeB.
  • the tunnel barrier layer 12 is, for example, at least one selected from the group consisting of MgO, Mg-Al-O, and Al 2 O 3.
  • the first free layer 11 or the second free layer 13 may be a stack including a plurality of layers.
  • the stack has, for example, a layer made of CoFeB, a layer made of CoFe, and a central layer.
  • CoFeB which has excellent TMR characteristics, is preferably disposed near the tunnel barrier layer 12, and CoFe may be disposed near the interface with another layer located away from the tunnel barrier layer 12.
  • the central layer is disposed between these layers, and NiFe, CoFeSiB, CoFeBTa, or the like, which has excellent soft magnetic properties, may be used.
  • the magnetizations of the first free layer 11 and the second free layer 13 sandwiching the tunnel barrier layer 12 are stabilized in an antiparallel arrangement in the absence of a hard bias or magnetic field.
  • the magnetic sensor is arranged so that the magnetic field to be detected is applied in a perpendicular direction (the hard axis direction of the free layer).
  • the magnetization of the first free layer 11 and the second free layer 13 rotates symmetrically with respect to the external magnetic field direction.
  • the angle between the magnetizations of the first free layer 11 and the second free layer 13 becomes smaller, resulting in the state shown in FIG. 5A or 5C.
  • the element resistance is lower than in the state shown in FIG. 5C.
  • the magnetic anisotropy of the magnetization of the first free layer 11 and the second free layer 13 in one direction is set to a strength appropriate to the magnitude of the magnetic field to be detected, as described later.
  • the magnitude of the saturation magnetic field and the magnetic permeability of the free layer are determined by the strength of the magnetic anisotropy (soft pin magnetic field strength).
  • the relationship between the magnetic field and resistance in a dual free type TMR element is such that the magnetic resistance is maximized in the absence of a magnetic field.
  • an external magnetic field is applied in the hard axis direction of the first free layer 11 and the second free layer 13
  • the magnetization of the first free layer 11 and the second free layer 13 rotates symmetrically with respect to the external magnetic field.
  • the angle between the magnetizations of the first free layer 11 and the second free layer 13 becomes smaller, and the element resistance of the dual free type TMR element decreases.
  • a dual free type TMR element that does not have a hard bias body exhibits even-function resistance magnetic field characteristics that are symmetric with respect to the positive and negative signs of the external magnetic field.
  • TMR elements that can be used in the magnetic sensor according to this embodiment.
  • the TMR element that can be used in the magnetic sensor according to this embodiment may be referred to as a "dual soft pin TMR sensor.”
  • a laminate of Ta and Ru can be used as the underlayer.
  • One or more types selected from the group consisting of IrMn, PtMn, FeMn, and NiMn can be used as the antiferromagnetic material.
  • CoFe can be used as the ferromagnetic layer.
  • Ru can be used as the coupling layer.
  • a non-magnetic material such as Cu, Ag, Cr, or Ru, preferably AgSn, can be used as the intermediate layer.
  • Ru can be used as the cap layer.
  • the bottom and top ferromagnetic layers of the stacking structure may be replaced with hard magnetic films such as CoPt without using an antiferromagnetic layer.
  • the free layer may be a single layer structure of a layer made of CoFeB, but may also be a laminated structure to further improve magnetic properties.
  • the laminated structure of the free layer may have, for example, a layer made of CoFeB, a layer made of CoFe, and a central layer.
  • the layer made of CoFeB, which has excellent TMR, is provided on the tunnel barrier layer side of the layer made of CoFe.
  • the central layer between the layer made of CoFeB and the layer made of CoFe uses NiFe, CoFeSiB, CoFeBTa, or the like, which has excellent soft magnetic properties.
  • This stack structure can be replaced with the magnetoresistance element 100 shown in FIGS. 2A and 2B.
  • the intermediate layers 23 and 27 are, for example, AgSn. Ferromagnetic interlayer coupling acts between the ferromagnetic layer 22 and the first free layer 24, which sandwich the intermediate layer 23. Ferromagnetic interlayer coupling acts between the ferromagnetic layer 28 and the second free layer 26, which sandwich the intermediate layer 27.
  • the coupling layer 28a is, for example, Ru, and strongly antiparallel couples the ferromagnetic layers 28 and 28b on both sides of the coupling layer 28a.
  • FIG. 6C is a diagram showing a first example (n ⁇ 1) of a TMR element of the second stacking type according to this embodiment.
  • the stacking order of [ferromagnetic layer 22a/coupling layer 22b]n and [coupling layer 28a/ferromagnetic layer 28b]n+1 of the first stacking type shown in FIG. 6B is reversed.
  • This stack structure can be replaced with the magnetoresistance element 100 shown in FIGS. 2A and 2B.
  • the TMR element of the first stack type (n ⁇ 1) shown in FIG. 6B can also be expressed as a general formula as follows: First stacking type: underlayer/antiferromagnetic layer A/[ferromagnetic layer A i /coupling layer A i ] n /ferromagnetic layer A n+1 /intermediate layer A/first free layer/tunnel barrier layer/second free layer/intermediate layer B/[ferromagnetic layer B j /coupling layer B j ] n+1 /ferromagnetic layer B n+2 /antiferromagnetic layer B/cap layer
  • the TMR element of the second stack type (n ⁇ 1) shown in FIG. 6C can also be expressed as a general formula as follows: Second stacking type: underlayer/antiferromagnetic layer A/[ferromagnetic layer A j /coupling layer A j ] n+1 /ferromagnetic layer A n+2 /intermediate layer A/first free layer/tunnel barrier layer/second free layer/intermediate layer B/[ferromagnetic layer B i /coupling layer B i ] n /ferromagnetic layer B n+1 /antiferromagnetic layer B/cap layer
  • the magnetization of the first free layer and the magnetization of the second free layer are oriented in a direction in which the gradient of the R-H characteristic becomes large under the influence of the bias magnetic field under no magnetic field.
  • the relationship between the magnetic field and the resistance in the even-function dual free type TMR element as shown in (A) to (D) of FIG. 5 is as follows.
  • the ferromagnetic layer A is laminated on the antiferromagnetic layer A.
  • the antiferromagnetic layer B is laminated on the ferromagnetic layer B.
  • one of the number of stacking of the ferromagnetic layer/coupling layer of the laminate including the magnetic layer A and the number of stacking of the ferromagnetic layer/coupling layer of the laminate including the magnetic layer B is an even number, and the other is an odd number.
  • the magnetizations of the ferromagnetic layers on both sides of the coupling layer are magnetically coupled to each other in antiparallel. After forming these laminated structures, they are heat-treated (at about 300° C.) under a magnetic field and returned to room temperature, and the magnetizations of the ferromagnetic layer A and the ferromagnetic layer B are fixed in the same direction by unidirectional magnetic anisotropy.
  • the magnetization of the first free layer and the magnetization of the second free layer have unidirectional magnetic anisotropy in opposite directions to each other, and the magnetization of the first free layer and the magnetization of the second free layer are oriented anti-parallel in the absence of a magnetic field.
  • the first stack type TMR element (n ⁇ 1) has an odd function relationship between the magnetic field and the resistance. This is because, as shown in FIG. 5(E), the even function R-H curve shifts when a bias magnetic field is applied to an even function dual free type TMR element.
  • an even-function dual free type TMR element As shown in (A) to (D) of FIG. 5, in an even-function dual free type TMR element, as the strength of the external magnetic field increases, the angle between the magnetizations of the first and second free layers decreases, and the element resistance decreases.
  • the external magnetic field is applied in the hard axis direction of the first and second free layers (perpendicular to the magnetization direction of the first and second free layers in the absence of a magnetic field).
  • the magnetizations of the first and second free layers rotate symmetrically with respect to the direction of the external magnetic field.
  • an even-function dual free type TMR element exhibits even-function resistance magnetic field characteristics that are symmetric with respect to the positive and negative directions in which the external magnetic field is applied.
  • the magnitude of the saturation magnetic field and the magnetic permeability of the free layers are determined by the soft pin strength of the first and second free layers, but this can be adjusted to the desired magnitude by the thickness and material (AgSn, etc.) of the intermediate layer.
  • a first example of another type of the first stacking type has a stacking structure represented by electrode 30/underlayer 30a/antiferromagnetic layer 31/ferromagnetic layer 32/intermediate layer 33/first free layer 34/tunnel barrier layer 35/second free layer 36/intermediate layer 37/ferromagnetic layer 38/coupling layer 28a/ferromagnetic layer 38b/antiferromagnetic layer 39/cap layer (not shown).
  • This stacking structure can be replaced with the magnetoresistance element 100 shown in Figures 2A and 2B.
  • FIG. 7B is a cross-sectional view of an example of a laminate structure (a second example (n ⁇ 1) of another type of the first laminate type) that can be used in the TMR element according to the first embodiment.
  • FIG. 7A is a modified example of the second example (n ⁇ 1) of the first laminate type shown in FIG. 6B.
  • This stacking structure can be replaced with the magnetoresistance element 100 shown in Figures 2A and 2B.
  • FIG. 7C is a modified example of the first example (n ⁇ 1) of the second laminate type in FIG. 6C.
  • This stacking structure can be replaced with the magnetoresistance element 100 shown in FIGS. 2A and 2B.
  • the names of the layers shown in Figures 6A to 6C are the same, and the same configuration as in Figures 6A to 6C can be used.
  • the stack shown in Figures 7A to 7C differs from the stack shown in Figures 6A to 6C in that the magnetization directions of the ferromagnetic layers 32, 38 are antiparallel to the first free layer 34, tunnel barrier layer 35, and second free layer 36, in that the magnetization directions of the ferromagnetic layers 22, 28 are parallel to the first free layer 24, tunnel barrier layer 25, and second free layer 26.
  • FIG. 8 is a diagram showing a stack structure of the third stack type.
  • the third type of stacked layer structure has a stacked layer structure represented by the following: electrode 40/underlayer 40a/antiferromagnetic layer 41/ferromagnetic layer 42/exchange coupling layer 43/first free layer 44/tunnel barrier layer 45/second free layer 46/exchange coupling layer 47/ferromagnetic layer 48/antiferromagnetic layer 49/cap layer (not shown).
  • This stacked layer structure can be replaced with the magnetoresistance element 100 shown in FIGS. 2A and 2B.
  • the exchange coupling layers 43 and 47 are made of Ru, Cr, Ir, Rh, etc. Depending on the thickness of the exchange coupling layer 43, the interlayer coupling between the ferromagnetic layer 42 and the first free layer 44 can be either antiferromagnetic or ferromagnetic. Depending on the thickness of the exchange coupling layer 47, the interlayer coupling between the ferromagnetic layer 48 and the second free layer 46 can be either antiferromagnetic or ferromagnetic. When the exchange coupling layer 43 has a thickness that provides antiferromagnetic coupling between the ferromagnetic layer 42 and the first free layer 44, the exchange coupling layer 47 has a thickness that provides ferromagnetic coupling between the ferromagnetic layer 48 and the second free layer 46. When the exchange coupling layer 43 has a thickness that provides ferromagnetic coupling between the layers sandwiching the exchange coupling layer 43, the exchange coupling layer 47 has a thickness that provides antiferromagnetic coupling between the layers sandwiching the exchange coupling layer 47.
  • the stack structure of the fourth stack type has a stack structure represented by the following: electrode 50/underlayer 50a/antiferromagnetic layer 51/dust layer 53/first free layer 54/tunnel barrier layer 55/second free layer 56/coupling layer 57/ferromagnetic layer 58/dust layer 58a/antiferromagnetic layer 59/cap layer (not shown).
  • This stack structure can be replaced with the magnetoresistance element 100 shown in Figures 2A and 2B.
  • the dust layers 53 and 58a are non-magnetic layers made of Ru or the like and have a thickness of 1 nm or less, and act to weaken the exchange bias of the antiferromagnetic material.
  • FIG. 9B is a diagram showing a stack structure of a fourth stack type (n ⁇ 1).
  • This stacking structure can be replaced with the magnetoresistance element 100 shown in FIGS. 2A and 2B.
  • FIG. 9C is a diagram showing a stack structure of a fifth stack type (n ⁇ 1).
  • This stack structure can be replaced with the magnetoresistance element 100 shown in FIGS. 2A and 2B.
  • the stacked structure of the fourth stacked type (n ⁇ 1) shown in FIG. 9B can also be expressed as the following general formula.
  • Fourth stack type 4 underlayer/antiferromagnetic layer A/dust layer A/[ferromagnetic layer A i /coupling layer A i ] n /first free layer/tunnel barrier layer/second free layer/[coupling layer B j /ferromagnetic layer B j ] n+1 /dust layer B/antiferromagnetic layer B/cap layer
  • the stack structure of the fifth stack type (n ⁇ 1) shown in Figure 9C can also be expressed as a general formula as follows.
  • FIG. 10 shows the configuration of a TMR element using stacks of the first to fifth stack types.
  • the TMR element has a laminated structure of a substrate 600/lower electrode 602/laminate layer 604C/upper electrode 606.
  • the laminate layer 604C is any one of the laminated structures of the first to fifth laminate types.
  • the laminate layer 604C is obtained by laminating each layer and then patterning it into a predetermined shape by photolithography or the like.
  • the substrate 600 is a silicon wafer or a ceramic wafer of AlTiC or alumina, and the lower electrode 602 and upper electrode 606 are made of Cu, Au, Ru, or the like. Insulating layers 604L and 604R are provided in adjacent regions on the left and right of the laminate layer 604C.
  • Figure 11 shows the R-H characteristics.
  • the resistance value is normalized to the resistance change rate.
  • Figure 11 shows the characteristics of two types of samples with different thicknesses of intermediate layer A (AgSn) and intermediate layer B. Both show even-function R-H characteristics and a resistance change rate of about 160%, but the value of the saturation magnetic field and the slope of the resistance change rate relative to magnetic field change (i.e., sensitivity) are adjusted by changing the thickness of intermediate layer A and intermediate layer B.
  • This resistance change rate is equivalent to the resistance change rate of a spin-valve TMR sensor fabricated under the same heat treatment conditions.
  • Magnetic property evaluation example 2 soft pin magnetic field control of the free layer 12A and 12B show that the saturation magnetic field and magnetic permeability of the first free layer and the second free layer of the first and second stacking type stacked structures can be controlled by the film thickness of the intermediate layer A and the intermediate layer B.
  • the material and film thickness of each layer are the same as those in Table 1.
  • FIG. 12B shows the plot of the soft pin magnetic field Hpin against the film thickness of the intermediate layer made of AgSn for various stacked structures. In either case, Hpin decreases with increasing thickness of the intermediate layer. From these data, it is possible to know the appropriate thickness of the intermediate layer to obtain the desired Hpin. It is also easy to infer that an even larger Hpin can be obtained by making the AgSn intermediate layer thinner than the thickness of 2.2 nm or 2.3 nm shown here.
  • Fig. 13A is a plan view of an example in which a TMR element array is used in a bridge-type magnetic sensor.
  • Fig. 13A is a side view of one TMR array in the example in which a TMR element array is used in a bridge-type magnetic sensor.
  • Each of the TMR arrays A1 to A4 replaces the first TMR element 1 to the fourth TMR element 4 in Fig. 1, respectively.
  • a hard bias body 120 is disposed on the side of the TMR arrays A1 to A4.
  • Each of the hard bias bodies 120 corresponds to each of the first hard bias body HB1 to the fourth hard bias body HB4, respectively.
  • each of the TMR element arrays A1 to A4 has a plurality of magnetoresistance elements 100.
  • On both sides of the magnetoresistance elements 100 there are hard bias bodies 120.
  • the distance between each of the magnetoresistance elements 100 and the hard bias body 120 is preferably in the range of 1 ⁇ m to 1000 ⁇ m, for example, and more preferably in the range of 5 ⁇ m to 200 ⁇ m. Note that the connecting lines between the TMR element arrays A1 to A4 have been omitted in FIG. 13A.
  • magnetoresistance elements 100 are connected in series by upper electrodes 125 and lower electrodes 126.
  • the present disclosure is not limited to this, and magnetoresistance elements 100 may be connected in parallel or in a combination of series and parallel.
  • the bias voltage applied to each magnetoresistance element 100 is distributed, and the problem of the resistance change rate of the magnetoresistance element 100 decreasing due to a high bias voltage can be alleviated.
  • FIG. 1 is a circuit diagram of an encoder using a bridge configuration according to the first embodiment.
  • the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element may be the dual soft pin TMR elements shown in FIGS. 6A to 6C, 7A to 7C, 8, 9A, and 9B.
  • these TMR elements are connected in parallel so that a current flows from the power source E to the ground G in a line connecting the first TMR element 1 and the second TMR element 2 and a line connecting the third TMR element 3 and the fourth TMR element 4.
  • the potential of the first connection point p1 located in the middle between the first TMR element 1 and the second TMR element 2 and the potential of the second connection point p2 located in the middle between the third TMR element 3 and the fourth TMR element 4 are detected as sensor outputs.
  • FIG. 14A is a perspective view of the configuration of a magnetic linear encoder to which the magnetic sensor 200 according to this embodiment is applied.
  • the magnetic linear encoder has a permanent magnet sheet on which N poles and S poles are alternately magnetized as a magnetic scale 201. The position on the surface of this magnetic scale 201 (permanent magnet sheet) is detected by the magnetic sensor 200.
  • FIG. 14B is a perspective view of the configuration of a magnetic rotary encoder to which the magnetic sensor 300 according to this embodiment is applied.
  • the magnetic rotary encoder has a permanent magnet region 301 on the circumferential surface of a rotor 302, where north and south poles are alternately magnetized.
  • the magnetic rotary encoder detects the rotation angle of this permanent magnet region 301 with the magnetic sensor 300.
  • a hard bias laminate is used as the hard bias body, but the present invention is not limited to this, and the hard bias body may be made in a bulk form and bonded together, so as to be far away from the TMR.
  • a bridge circuit using four TMR elements to which a bias magnetic field is applied and a connection to a current source and grounding as a current source for the bridge circuit is shown, but the present invention is not limited to this, and the bridge circuit does not need to be grounded.
  • a bridge-type magnetic sensor only needs to have two terminals on the high potential side and low potential side (high potential terminal t1 and low potential terminal t2). One end of the first TMR element 1 and the third TMR element 3 may be connected to the high potential terminal t1, and one end of the second TMR element 2 and the fourth TMR element 4 may be connected to the low potential terminal t2.
  • FIG. 1 an example is shown in which the magnetic field application section that applies a bias magnetic field to each of the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 is made up of a hard bias body, but the magnetic field application section that applies a bias magnetic field to each TMR element is not limited to this example.
  • the direction of the detected magnetic field of the bridge-type magnetic sensor is not limited to the y direction.
  • FIG. 19 is a circuit diagram of a bridge-type magnetic sensor according to the second embodiment.
  • the bridge-type magnetic sensor shown in FIG. 19 has a magnetic field application section that includes a power supply E' and wiring W.
  • the bridge-type magnetic sensor shown in FIG. 19 differs from the bridge-type magnetic sensor shown in FIG. 1 in that the power supply E' and wiring W are installed as the magnetic field application section instead of the first hard bias body HB1 to the fourth hard bias body HB4.
  • the bridge-type magnetic sensor shown in FIG. 19 also differs from the bridge-type magnetic sensor shown in FIG. 1 in that the direction of the detected magnetic field is the x-direction.
  • the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 form a bridge circuit and are connected to the power supply E and ground G.
  • the configuration of the bridge circuit in FIG. 19 is the same as the bridge circuit in FIG. 1.
  • the wiring W is connected to a power source E', and a current i' flows through it.
  • the wiring W branches into wiring W1 and wiring W2 along the way, and then recombines.
  • the wiring W1 is arranged in the vicinity of the first TMR element 1 and the second TMR element 2.
  • “in the vicinity” means that the distance between the wiring and the TMR element is narrow, as long as the insulation between the wiring and the TMR element can be ensured. For example, this distance is in the range of 10 nm to 1000 nm.
  • the position of the wiring W1 does not matter as long as it can apply bias magnetic fields in different directions to the first TMR element 1 and the second TMR element 2.
  • At least a part of the wiring W1 has a first overlapping portion that overlaps with the first TMR element 1 when viewed from one direction, and a second overlapping portion that overlaps with the second TMR element 2.
  • the wiring W2 is arranged in the vicinity of the third TMR element 3 and the fourth TMR element 4.
  • the position of the wiring W2 does not matter as long as it can apply bias magnetic fields in different directions to the third TMR element 3 and the fourth TMR element 4.
  • At least a portion of the wiring W2 has a third overlapping portion that overlaps with the third TMR element 3 and a fourth overlapping portion that overlaps with the fourth TMR element 4 when viewed from one direction. In the first overlapping portion and the fourth overlapping portion, a current flows in the wiring W in the same direction.
  • a current flows in the same direction.
  • the direction of current flow in the first overlapping portion and the fourth overlapping portion is opposite to the direction of current flow in the second overlapping portion and the third overlapping portion.
  • the bridge-type magnetic sensor shown in FIG. 19 detects a magnetic field in the x direction.
  • a bias magnetic field generated by a current flowing through the wiring W1 is applied to the first TMR element 1 and the second TMR element 2.
  • a bias magnetic field in a first direction is applied to the first TMR element 1, and a bias magnetic field in a second direction is applied to the second TMR element 2.
  • the first and second directions are 180 degrees opposite.
  • a bias magnetic field generated by a current flowing through the wiring W2 is applied to the third TMR element 3 and the fourth TMR element 4.
  • a bias magnetic field in the second direction is applied to the third TMR element 3, and a bias magnetic field in the first direction is applied to the fourth TMR element 4.
  • Figure 20 is a diagram showing the orientation direction of magnetization of the first free layer FL1 and the second free layer FL2 of each TMR element of the magnetic sensor according to the second embodiment.
  • the magnetization of the first free layer FL1 and the magnetization of the second free layer FL2 of each TMR element are arranged anti-parallel when no current flows through the wiring W (initial state).
  • the magnetization of the first free layer FL1 and the magnetization of the second free layer FL2 rotate from their initial states due to the bias magnetic field generated from the wiring W1 and W2.
  • the magnetization of the first free layer FL1 and the magnetization of the second free layer FL2 rotate in different directions from their initial states in the first TMR element 1 and the second TMR element 2.
  • the directions of the bias magnetic field Hb applied to each TMR element by the wiring W1 are opposite.
  • the magnetization of the first free layer FL1 and the magnetization of the second free layer FL2 rotate in different directions from the initial state. This is because the directions of the bias magnetic field Hb applied to each TMR element by the wiring W2 are opposite.
  • FIG. 21 is a schematic diagram for explaining the operation of the bridge-type magnetic sensor according to the second embodiment.
  • each of the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element shows an even-function R-H characteristic.
  • the direction of the magnetic field H is the x-direction, unlike FIG. 1, and the magnetization of the free layer is in the ⁇ y-direction in the absence of the bias magnetic field Hb.
  • a bias magnetic field Hb is applied to each TMR element.
  • the even-function R-H curve shifts.
  • each of the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element shows an odd-function R-H characteristic.
  • a bias magnetic field Hb in the opposite direction is applied to the first TMR element 1 and the fourth TMR element 4, and the second TMR element 2 and the third TMR element 3. Therefore, the direction in which the R-H curve shifts is opposite.
  • the slope direction of the R-H characteristics is opposite for the first TMR element 1 and the fourth TMR element 4 and the second TMR element 2 and the third TMR element 3.
  • the first TMR element 1 and the fourth TMR element 4, and the second TMR element 2 and the third TMR element 3 have opposite R-H characteristic slopes, so there is no problem in that the differential output ⁇ V between the first connection point p1 and the second connection point p2 is cancelled out and becomes zero.
  • the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element each have a first free layer and a second free layer, so the output ⁇ V can be increased.
  • FIG. 22 is a circuit diagram of a modified example of the bridge-type magnetic sensor according to the second embodiment.
  • the magnetization of the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 are oriented in the ⁇ x direction, and the wiring W has a different routing pattern from the example shown in FIG. 19.
  • the specific configuration of the magnetic field application section and the direction of the magnetic field detected by the bridge-type magnetic sensor can each be changed.
  • the bridge-type magnetic sensor shown in FIG. 22 detects a magnetic field in the y direction, similar to the bridge-type magnetic sensor shown in FIG. 1.
  • the magnetization of the first TMR element 1 and the fourth TMR element 4 is oriented in the +x direction
  • the magnetization of the second TMR element 2 and the third TMR element 3 is oriented in the -x direction.
  • the wiring W branches into wiring W3 and wiring W4 along the way and then recombines.
  • Wiring W3 is disposed near the first TMR element 1 and the third TMR element 3.
  • at least a portion of wiring W3 has a first overlapping portion that overlaps with the first TMR element 1 and a third overlapping portion that overlaps with the third TMR element 3.
  • a bias magnetic field in the +y direction is applied to the first TMR element 1 by the current i' flowing through wiring W3.
  • a bias magnetic field in the -y direction is applied to the third TMR element 3 by the current i' flowing through wiring W3.
  • the wiring W4 is disposed near the second TMR element 2 and the fourth TMR element 4.
  • at least a portion of the wiring W4 has a second overlapping portion that overlaps with the second TMR element 2 and a fourth overlapping portion that overlaps with the fourth TMR element 4.
  • a bias magnetic field in the -y direction is applied to the second TMR element 2 by the current i' flowing through the wiring W4.
  • a bias magnetic field in the +y direction is applied to the fourth TMR element 4 by the current i' flowing through the wiring W4.
  • the wiring W is laminated on the first TMR element 1, the second TMR element 2, the third TMR element 3, and the fourth TMR element 4 via an insulating layer.
  • the thickness of the insulating layer is, for example, 10 nm or more and 1000 nm or less. If the insulating layer is too thin, the risk of short-circuiting between the TMR elements and the wiring W increases. If the insulating layer is too thick, the current magnetic field applied to each TMR element becomes smaller. As a result, it becomes impossible to apply a sufficient bias magnetic field required for a highly sensitive bias point where the resistance changes sharply.
  • the present disclosure is not limited to these examples.
  • the width of the wiring W, the distance between the wiring W and the free layer, etc. can also be freely designed.
  • the magnetic sensor disclosed herein has a large maximum resistance change rate of 210% when the stacked structure is optimized, and approximately 160% when manufactured within a typical range, making it possible to suppress asymmetry in the R-H characteristics caused by deviations in the direction of the magnetic field to be detected. This makes the magnetic sensor suitable for use in position and rotation detection devices.

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PCT/JP2023/036238 2022-12-21 2023-10-04 磁気センサ、リニアエンコーダ用磁気センサ及び磁気式ロータリーエンコーダ WO2024135038A1 (ja)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009250931A (ja) * 2008-04-10 2009-10-29 Rohm Co Ltd 磁気センサおよびその動作方法、および磁気センサシステム
EP2330432A1 (en) * 2009-11-19 2011-06-08 Nxp B.V. Magnetic field sensor
JP2012049213A (ja) * 2010-08-25 2012-03-08 Mitsubishi Electric Corp 磁気抵抗効果素子、それを用いた磁界検出器、位置検出器、回転検出器および電流検出器
US20130164549A1 (en) * 2011-12-21 2013-06-27 Hitach Golbal Storage Technologies Netherlands B.V Half Metal Trilayer TMR Reader with Negative Interlayer Coupling
US20210063508A1 (en) * 2019-08-28 2021-03-04 Western Digital Technologies, Inc. Dual Free Layer TMR Magnetic Field Sensor
JP2022047887A (ja) * 2020-09-14 2022-03-25 株式会社東芝 磁気センサ及び検査装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009250931A (ja) * 2008-04-10 2009-10-29 Rohm Co Ltd 磁気センサおよびその動作方法、および磁気センサシステム
EP2330432A1 (en) * 2009-11-19 2011-06-08 Nxp B.V. Magnetic field sensor
JP2012049213A (ja) * 2010-08-25 2012-03-08 Mitsubishi Electric Corp 磁気抵抗効果素子、それを用いた磁界検出器、位置検出器、回転検出器および電流検出器
US20130164549A1 (en) * 2011-12-21 2013-06-27 Hitach Golbal Storage Technologies Netherlands B.V Half Metal Trilayer TMR Reader with Negative Interlayer Coupling
US20210063508A1 (en) * 2019-08-28 2021-03-04 Western Digital Technologies, Inc. Dual Free Layer TMR Magnetic Field Sensor
JP2022047887A (ja) * 2020-09-14 2022-03-25 株式会社東芝 磁気センサ及び検査装置

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