JP2014169952A - Electric current sensor, and electric power sensor - Google Patents

Abstract

A high-performance current sensor with a simple configuration is provided.
A current sensor according to an embodiment of the present invention includes an AC power supply that supplies current to a load, a magnetoresistive element that changes its resistance value based on a magnetic field that changes in accordance with the current that flows through the load, and a magnetoresistive element And a detection output circuit that detects and outputs a maximum value and a minimum value of a potential difference between both terminals of the magnetoresistive element, and a current that flows through the load based on the maximum value and the minimum value. This problem is solved by detecting the above.
[Selection] Figure 1

Description

  The present invention relates to a current sensor and a power sensor.

  In recent years, research on spintronics that attempts to realize new physical properties, functions, devices, and the like using physical quantities called spins (magnetic properties of electrons) has become a major trend. Next-generation magnetic memory heads, such as GMR (Giant Magneto Resistive) elements that have one of the magnetoresistive elements and TMR (Tunneling Magneto Resistive) elements that have a tunnel magnetoresistive effect, magnetic heads, and magnetic sensor fields The application to etc. is examined.

  The TMR element is an element made of ferromagnetic metal / thin insulating film tunnel barrier / ferromagnetic metal. Since the insulating film is very thin, about 2 nm, a tunnel current can flow between the ferromagnetic metals on both sides. A change in tunnel resistance depending on the magnetization direction of the ferromagnetic metal can be used as a sensing element such as a magnetic sensor.

  As an application of the magnetic sensor, for example, a current sensor that can detect a current in a non-contact manner by measuring a magnetic field change is widely used.

  Patent Document 1 discloses a current sensor that stacks a GMR element, a bias magnet that applies a bias magnetic field to the GMR element, and a printed circuit board through which a current to be measured flows to detect a minute current or a large current with high accuracy. .

  In Patent Document 2, a magnetic field in which variation in operating point and sensitivity associated with the use of a permanent magnet for a bias magnetic field is reduced by detecting a differential signal including information on the magnitude and direction of a magnetic field to be measured or a current to be measured. A sensor device and a current sensor device are disclosed.

  As an index representing the performance of the current sensor, for example, it is possible to accurately detect the current flowing through the measurement target, and that the magnetoresistive element mounted on the current sensor sharply reverses magnetization with respect to the current flowing through the adjacent portion. It is done.

  In the current sensor in Patent Document 1, in addition to the magnetic field to be measured, a constant bias magnetic field is applied to the magnetoresistive means by the bias magnetic field applying means. Since the measured current is detected by the measured magnetic field and the bias magnetic field, it is easily affected by the bias magnetic field, and the detection accuracy is not sufficient. Furthermore, the magnetoresistive element is limited to the GMR element.

  Furthermore, the current sensor is desired to have a small and simple configuration.

  Since the current sensor in Patent Document 2 requires a circuit for generating or detecting a differential signal, the configuration of the current sensor is complicated.

  That is, a current sensor having a simple configuration and high performance while utilizing the characteristics of the magnetoresistive element has not been developed yet.

  The present invention has been made in view of the above problems, and an object thereof is to provide a high-performance current sensor with a simple configuration.

  In order to achieve the above object, a current sensor according to an embodiment of the present invention includes an AC power supply that supplies current to a load, a magnetoresistive element that changes its resistance value based on a magnetic field that changes in accordance with the current flowing through the load, and A current source that supplies current to the magnetoresistive element, and a detection output circuit that detects and outputs a maximum value and a minimum value of a potential difference between both terminals of the magnetoresistive element, and based on the maximum value and the minimum value, It is characterized by detecting a current flowing through a load.

  According to the embodiment of the present invention, it is possible to provide a high-performance current sensor with a simple configuration.

It is a figure which shows an example of schematic structure of the current sensor which concerns on embodiment. It is a figure which shows an example of schematic structure of the current sensor which concerns on embodiment. It is a figure which shows an example of schematic structure of the current sensor which concerns on embodiment. It is a graph which shows an example of resistance value change with respect to the magnetic field of the TMR element concerning an embodiment. 1 is a schematic cross-sectional view of a TMR element according to an embodiment. It is a flowchart which shows an example of operation | movement of the current sensor which concerns on embodiment. It is an example of measurement data. It is an example of measurement data. It is a figure which shows an example of the semiconductor device to which the current sensor which concerns on embodiment is applied. It is a figure which shows an example of the semiconductor device to which the current sensor which concerns on embodiment is applied.

(Configuration of current sensor)
FIG. 1 is an example of a schematic configuration of a current sensor 10 according to the present embodiment.

  As shown in FIG. 1, the current sensor 10 includes an AC power supply 11, a load 12 (measurement target), a detection output circuit 13, a magnetoresistive element 14, and a current source 15 for the magnetoresistive element 14.

  The detection output circuit 13 and the magnetoresistive element 14 are connected in parallel. Further, the current source 15 and the magnetoresistive element 14 are connected in series. Also, one terminal of the load 12 is electrically connected to the AC power source 11, and the other terminal of the load 12 is electrically connected to, for example, GND.

  The current sensor 10 functions as the current sensor 10 by detecting the current flowing through the load 12 that is the measurement target.

  The AC power supply 11 supplies an AC current to the load 12.

  A current detected by the current sensor 10 flows through the load 12.

  The magnetoresistive element 14 is an element whose resistance value changes based on a magnetic field change generated in the magnetoresistive element 14. In the case of the current sensor 10 according to the present embodiment, since no magnetic field is applied from the outside, the factor causing the magnetic resistance change in the magnetoresistive element 14 is the current flowing in the vicinity of the magnetoresistive element 14 (even the current flowing through the load). Yes). With the current, the magnetic field generated in the magnetoresistive element 14 changes.

  The magnetic field of the magnetoresistive element 14 changes along a minor loop (a minute magnetization loop formed with respect to a weak alternating magnetic field) in addition to operating in the major loop of magnetization of the magnetoresistive element 14.

  Note that the resistance value of the magnetoresistive element 14 depends not only on the current flowing in the vicinity of the magnetoresistive element 14, but also on the film thickness of the element, the area of the element, the material constituting the element, and the like.

  Examples of the magnetoresistive element 14 include a TMR element, a GMR element, and an AMR (An-Isotropic Magneto Resistive) element, but are not limited to these elements. An element may be selected as appropriate according to the application.

  The detection output circuit 13 detects a potential difference between the voltage of one terminal (for example, a cap layer described later) of the magnetoresistive element 14 and the voltage of the other terminal (for example, a seed layer described later).

  The potential difference changes with the current flowing in the vicinity of the magnetoresistive element 14. That is, based on the change in the magnetic field generated in the magnetoresistive element 14, the resistance value of the magnetoresistive element 14 changes, and the potential difference between both terminals of the magnetoresistive element 14 changes.

  Further, the detection output circuit 13 takes in the maximum value (instantaneous value) and minimum value (instantaneous value) of the detected potential difference between both terminals of the magnetoresistive element 14, and outputs an output signal based on the taken in maximum value and minimum value. The data is output to an output signal processing unit 16 provided outside. The output signal is a current detected by the current sensor.

  The current source 15 supplies a constant current having a predetermined magnitude to the magnetoresistive element 14.

  The current source 15 supplies a constant current to the magnetoresistive element 14 regardless of whether or not a magnetic field change occurs in the magnetoresistive element 14.

  According to the current sensor 10 according to the present embodiment, it is possible to accurately detect the current flowing through the load 12 as the measurement target based on the maximum value and the minimum value of the potential difference generated at both terminals of the magnetoresistive element. . That is, since only peak values (maximum value and minimum value) are to be detected, a high-performance current sensor can be realized with a very simple configuration without mounting a complicated circuit or the like. Furthermore, since the current flowing through the proximity portion of the magnetoresistive element 14 is equal to the current flowing through the measurement target, the change in the magnetic field of the magnetoresistive element 14 caused by flowing the current can be used. Therefore, for example, a configuration for applying an external magnetic field can be omitted, and a current sensor can be realized with a simple configuration.

  In the current sensor 10 shown in FIG. 1, the current path of the current flowing from the AC power supply 11 to the load 12 (the current path of the current flowing in the vicinity of the magnetoresistive element 14) has a shape surrounding the magnetoresistive element 14 ( The shape of the current path is not particularly limited.

For example, like the current sensor 20 shown in FIG. 2, it may have a shape having a current branch point and a current junction point (for example, a branch point A and a junction point B). As shown in FIG. 2, the current I _A is shunted, passes through the branch point A, becomes current I _A1 and current I _A2 , passes through the junction B, and joins again to become current I _A. The shape of a current path through which a current flows may be used.

By making the shape of the current path into a shape having a current branch point and a current junction, the current detected by the magnetoresistive element 14 can be kept low. That is, even though a large current (current I _A ) flows through the load 12, a small current (current I _A2 ) obtained by subtracting the current I _A1 from the current I _A flows through the magnetoresistive element 14. Therefore, the current sensor 20 can detect the current I _a on the basis of the current I _A2.

  Thus, according to the current sensor 20, it is possible to reduce the magnetic saturation phenomenon of the magnetoresistive element 14 that occurs when the current flowing through the magnetoresistive element 14 is too large. Therefore, the current detection range that can be detected by the current sensor can be expanded. That is, even when a wide range of current from small current to large current is passed through the load, the current can be detected relatively easily.

  The shape of the current path is not particularly limited. In addition, for example, the shape of the current path may be a linear shape or a half-loop shape. In any case, the current path is close to the magnetoresistive element 14, and the shape is such that sufficient sensitivity (current that can cause the magnetoresistive element 14 to change the magnetic field and the resistance value flows) is obtained. It is preferable to form a current path. It is also possible to form the current path in such a shape that the detection output circuit 13 can output a desired signal output.

  The current sensor shown in FIGS. 1 and 2 is configured to have one magnetoresistive element 14, but the number of magnetoresistive elements 14 is not particularly limited.

For example, a magnetoresistive element may be provided for each of the branched currents I _A1 and I _A2 shown in FIG.

  Further, for example, a configuration having four magnetoresistive elements as in the current sensor 30 shown in FIG. When four magnetoresistive elements are provided, all of these magnetoresistive elements may be used, or some of the magnetoresistive elements may be used.

  The current sensor 30 includes magnetoresistive elements 14A, 14B, 14C, and 14D. The magnetoresistive elements 14A and 14B are connected in series, the magnetoresistive elements 14C and 14D are connected in series, and the magnetoresistive elements 14A and 14B connected in series and the magnetoresistive elements 14C and 14D connected in series are Connected in parallel.

  The detection output circuit 13 is connected between the voltage at the terminal X (terminal between the magnetoresistive element 14C and the magnetoresistive element 14D) and the voltage at the terminal Y (terminal between the magnetoresistive element 14A and the magnetoresistive element 14B). The potential difference is detected. Note that the potential difference between the terminal X and the terminal Y changes with a change in the resistance value of the magnetoresistive elements 14A, 14B, 14C, and 14D. The direction in which the change in resistance value of these magnetoresistive elements increases or decreases can be set as appropriate.

  The greater the number of magnetoresistive elements, the more precisely the change in resistance value of the magnetoresistive elements necessary for detecting the current can be detected. Therefore, the performance as a current sensor can be further improved.

(Magnetic resistance element)
Next, a TMR element will be described as an example of the magnetoresistive element 14 used in the current sensor according to the present embodiment with reference to FIGS. The magnetoresistive element 14 is not limited to a TMR element. It is particularly preferable if the magnetoresistive element exhibits a sharp magnetic field change with respect to a change in the current flowing in the vicinity of the magnetoresistive element 14 (current flowing through the measurement target).

  FIG. 4 is a graph showing an example of a change in resistance value with respect to the magnetic field of the TMR element when the TMR element 100 is used as the magnetoresistive element. FIG. 5 is a schematic sectional view of the TMR element 100. The horizontal axis represents a magnetic field (relative value), and the vertical axis represents a resistance value (relative value).

  As shown in FIG. 4, in the region C1, the resistance value of the TMR element has a linear increase characteristic with respect to the magnetic field. Up to a certain magnetic field (for example, the boundary between region C1 and region C2), the resistance value of the TMR element has a linear increase characteristic with respect to the magnetic field (the inclination of the minor loop of magnetization is constant as the magnetic field increases) Value). However, when a certain magnetic field is passed, magnetic saturation begins, and the resistance value of the TMR element saturates at a constant value. (The inclination of the minor loop of magnetization decreases with increasing magnetic field). In the region C2, the resistance value of the TMR element has a saturation characteristic with respect to the magnetic field. That is, with the transition from the region C1 to the region C2, the resistance value of the TMR element gradually shifts from a linear increase characteristic to a saturation characteristic.

  Next, a specific configuration of the TMR element will be described.

  As shown in FIG. 5, the TMR element 100 includes a cap layer 101, a free layer 102, a tunnel barrier layer 103, a magnetization fixed layer 104, a seed layer 105, and a substrate 106.

  In the TMR element 100, the direction of the magnetic field of the two magnetic layers (the free layer 102 and the magnetization fixed layer 104) sandwiching the tunnel barrier layer 103 determines the resistance value of the TMR element 100.

  The direction of the magnetic field of the magnetization fixed layer 104 is fixed. The direction of the magnetic field of the free layer 102 changes. Therefore, the resistance value of the TMR element 100 is determined by the degree of change in the magnetic field direction of the free layer 102 relative to the magnetic field direction of the magnetization fixed layer 104.

  For example, if the direction of the magnetic field of the fixed magnetization layer 104 and the direction of the magnetic field of the free layer 102 are parallel, the resistance value of the TMR element 100 becomes small. Further, for example, if the anti-parallel, the resistance value of the TMR element 100 increases.

  Since the performance of the TMR element 100 is so high that the direction of the magnetic field of the free layer 102 is easily reversed with respect to the current flowing in the proximity portion (the more sensitive the magnetization is reversed), it can be used as a highly sensitive current sensor. Is possible. The ease of reversing the direction of the magnetic field of the free layer 102 (magnetization reversal) can also be changed by the film thickness of the magnetization fixed layer 104 and the free layer 102.

  Note that the resistance value of the TMR element 100 can be controlled by the film thickness of the tunnel barrier layer 103 in addition to the current. As the thickness of the tunnel barrier layer 103 is decreased, the resistance value is decreased.

  Further, the resistance value of the TMR element 100 can be controlled by the element areas of the free layer 102, the magnetization fixed layer 104, and the like. The larger the element area, the smaller the resistance value.

  It is also known that the resistance value of the magnetoresistive element 14 can be controlled by the material constituting the magnetoresistive element 14. Differences in electron mobility, etc. that vary depending on the material cause the resistance value to change.

  As described above, the resistance value of the TMR element 100 is relatively easily controlled by the film thickness of the element, the area of the element, the material constituting the element, and the like, and is easily applied to the current sensor according to the present embodiment.

  As the substrate 106, a Si substrate, a SiO2 substrate, or the like can be used.

  The seed layer 105 serves as a buffer layer between the substrate 106 and the magnetization fixed layer 104. The seed layer 105 is formed with a film thickness of about 0.5 nm to 10 nm using an ultra-high vacuum sputtering apparatus, an ion beam sputtering apparatus, an EB deposition apparatus, or the like. The seed layer 105 may have a stacked structure. For example, the characteristics of the seed layer 105 can be improved by using a stacked structure of a Ta layer and FeNi.

  As the magnetization fixed layer 104, an FeMn layer, PtMn layer, IrMn layer, NiMn layer, PdPt layer, Mn layer, CrPtMn layer, CoMn layer, or an alloy layer thereof can be used. Further, a material having a large holding force or a hard magnetic material (for example, AlNiCo, PtCo, etc.) may be used. The thickness of the magnetization fixed layer 104 is preferably about 3 nm to 400 nm, more preferably about 10 nm to 100 nm.

  Note that a synthetic ferrimagnetic medium or the like may be formed on the magnetization fixed layer 104 as a pinned layer.

  As the tunnel barrier layer 103, an AlO layer, an MgO layer, or the like can be used. The thickness of the tunnel barrier layer 103 is preferably about 0.5 nm to 6 nm, more preferably about 1 nm to 4 nm. For example, when an MgO layer is used, an excellent magnetoresistance change rate characteristic can be obtained even if the film thickness is relatively large. Furthermore, the MgO layer can be annealed to increase the crystallinity of the MgO layer and improve the magnetoresistance change rate characteristics.

  As the free layer 102, a permalloy (NiFe) layer, a supermalloy layer, a CoFe layer, a CoNiFe layer, a CoZrNb layer, a CoFeB layer, a CoFeSiB layer, a FeAlSi layer, or the like can be used. Further, a material having soft magnetic characteristics, a material having hard magnetic characteristics, or the like can be used.

  In the TMR element 100, detection of a weak magnetic field mainly depends on the characteristics of the free layer 102. By improving the characteristics of the free layer 102, the current detection sensitivity can be increased in the case of a current sensor.

  The cap layer 101 is formed to protect the free layer 102. As the cap layer 101, a Ta layer, an Au layer, or the like can be used.

  As described above, by applying the TMR element 100 that takes advantage of the characteristics of the spintronic element to the current sensor according to the present embodiment, it is easy to provide a high-performance current sensor with a simple configuration.

(Operation of current sensor)
Next, the operation at the time of current detection of the current sensor 10 according to the present embodiment will be described.

  FIG. 6 is a flowchart showing an example of the operation of the current sensor 10 when the current is detected.

  When a current is supplied from the AC power supply 11 to the load 12 (S201), a change occurs in the magnetic field of the magnetoresistive element 14 with a change in the current flowing through the load 12 (S202).

  Based on the magnetic field change of the magnetoresistive element 14, the resistance value of the magnetoresistive element 14 changes. As the resistance value of the magnetoresistive element 14 changes, the potential difference between both terminals of the magnetoresistive element 14 changes (S203).

  Based on the change in the potential difference of the magnetoresistive element 14, the current sensor 10 detects the current flowing through the measurement target (load 12). Specifically, the detection output circuit 13 takes in the maximum value (instantaneous value) and minimum value (instantaneous value) of the potential difference (S204), and outputs an output signal based on the maximum value and the minimum value (S205).

  After the detection output circuit 13 outputs the output signal, the process returns to S201 again. The flow from S201 to S205 is repeated to detect the current flowing through the measurement target.

  It should be noted that a detection control unit, a program, or the like may be provided outside or inside the current sensor 10 and operated as appropriate.

  Note that the maximum value and the minimum value can be captured by measuring the instantaneous value in each cycle unit. For example, the maximum value and the minimum value for one period can be taken in, and the number of periods can be arbitrarily selected as necessary. By selecting the optimal number of cycles according to the situation, the immediacy of the current sensor can be improved and the performance can be maintained.

  Next, FIG. 7 shows an example of measurement data when the current flowing through the measurement target (load 12) is detected by the current sensor 10 according to the present embodiment.

  As shown in FIG. 7, it can be seen that the current sensor 10 can accurately detect the current flowing through the load 12 that changes over time.

  Note that it is also possible to calculate the power from the product of the measurement data shown in FIG. 7 and the voltage of the AC power supply 11. Therefore, it is also possible to configure a power sensor using a current sensor by providing the current sensor 10 with a power calculation means.

  Further, as shown in FIG. 8A, after the measurement data shown in FIG. 7 is detected and detected, it can be integrated in each cycle. Further, as shown in FIG. 8B, the measurement data shown in FIG. 7 can be detected, detected, integrated in each cycle, integrated in each cycle, and further rectified.

  As shown in FIG. 8, in this case as well, it can be seen that the current flowing through the load 12 that changes over time can be accurately detected by the current sensor 10.

  As described above, by integrating or rectifying the current flowing through the load, noise components and the like can be easily removed, and the performance as a current sensor can be further improved.

  According to the current sensor 10 of the present invention, since the current sensor can be realized with a simple configuration in which the current is passed through the proximity portion of the magnetoresistive element and the current is detected by utilizing the characteristics of the magnetoresistive element, the current sensor 10 is practical. Rich. In addition, by focusing only on the maximum and minimum values of the potential difference and using the maximum and minimum values as current detection targets, the current flowing through the measurement target can be accurately measured despite the simple configuration. Can be detected.

(Application example 1)
FIG. 9 is a schematic cross-sectional view showing an example of a semiconductor device manufactured by incorporating the current sensor of this embodiment into a semiconductor LSI process.

  In the TMR element 100, one terminal (cap layer side) is electrically connected to the detection output circuit 13 via the wiring metal layer B and the wiring metal layer C. The other terminal (seed layer side) is electrically connected to the MOSLSI region via the wiring metal A.

  The electric wiring wr is formed in a loop shape along the thin film stacking direction (vertical direction in the drawing) of the TMR element 100.

  According to this configuration, the direction of the magnetic field generated in the TMR element 100 is parallel to the film surface of the TMR element 100 (the left-right direction in the figure), so that the influence of the demagnetizing field of the TMR element 100 can be taken into consideration. Therefore, the detection performance as a current sensor can be improved.

  In addition, since multilayer wiring can be formed in a direction perpendicular to the TMR element 100, it is possible to fabricate a MOSLSI with a relatively small area, and to achieve both miniaturization of the current sensor and high sensitivity. be able to.

(Application example 2)
FIG. 10 is a schematic top view showing an example of a semiconductor device manufactured by incorporating the current sensor of this embodiment into a semiconductor LSI process.

  A pair of loop-shaped electric wires wr1 and wr2 are formed in the vicinity of the sensing element made of the TMR element, and the electric wires wr1 and wr2 are formed in a loop shape along the thin film stacking direction of the TMR element 100. According to such a Helmholtz configuration (a configuration in which the electrical wiring wr1 and the electrical wiring wr2 face each other and are formed in parallel), the influence of the demagnetizing field of the TMR element 100 can be taken into account as in the case of FIG. In addition, since the uniformity of the intensity of the generated magnetic field can be improved, the performance as a current sensor can be further improved. Furthermore, since it becomes easy to select the position of the electrical wiring relatively freely, more accurate current detection becomes possible.

  Note that the current sensor according to the present embodiment can be applied to, for example, a magnetic field sensor, a geomagnetic sensor, a current monitor (upper / lower limit value check, etc.), a system equipped with these, an LSI, and the like. Moreover, application to each element, such as MRAM, is also possible.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and within the scope of the gist of the embodiment of the present invention described in the claims, Various modifications and changes are possible.

10 Current sensor
11 AC power supply
12 Load
13 Detection output circuit
14 Magnetoresistive element
15 Current source

JP 2002-82136 A JP 2000-55998 A

Claims (6)

An AC power supply for supplying current to the load;
A magnetoresistive element whose resistance value changes based on a magnetic field that changes with a current flowing through the load;
A current source for supplying current to the magnetoresistive element;
A detection output circuit that detects and outputs a maximum value and a minimum value of a potential difference between both terminals of the magnetoresistive element, and
A current sensor that detects a current flowing through the load based on the maximum value and the minimum value. The current sensor according to claim 1, wherein the magnetoresistive element is a TMR element, an AMR element, or a GMR element. 3. The current sensor according to claim 1, wherein a current flowing through the load by the AC power source flows so as to surround the magnetoresistive element. 4. The current sensor according to claim 1, wherein the current is shunted. The current sensor according to any one of claims 1 and 4, wherein the current is rectified. An electric power sensor characterized by calculating electric power based on the voltage of said AC power supply, and the electric current which flows into the load detected by the electric current sensor according to any one of claims 1 to 5.

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