JP2013113799A - Current detection device, current detection element and current detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the measurement of a wider current range.SOLUTION: A magnetic resistance element using a magnetic resistance effect in which a resistance value changes in accordance with magnetic field intensity is used as an element for detecting current. The current value of a measurement object current is measured on the basis of the resistance of the magnetic resistance element corresponding to a magnetic field generated when the measurement object current is caused to flow to wiring arranged in the vicinity of the magnetic resistance element. In addition, the magnetic resistance element is used as a pure resistance in a linear region of an IV characteristic, the measurement object current is caused to flow directly to the magnetic resistance element to measure a current value. The current measurement using the magnetic resistance effect of the magnetic resistance element and the current measurement using the magnetic resistance element as a pure resistance are switched in accordance with the current value of the measurement object current.

Description

  The present invention relates to a current detection device, a current detection element, and a current detection method for detecting current using a magnetoresistive element.

  Conventionally, portable sensors such as current transformers and clamp meters, which are represented by current transformers for measuring instruments, are known as current sensors for measuring the current flowing in electrical wiring. These sensors mainly use iron cores in order to ensure the principle and accuracy. Therefore, magnetic saturation occurs at a large current, and the current measurement range cannot be made large. In addition, the iron core may generate heat at a large current.

  Therefore, a current sensor using a magnetoresistive element has been proposed as an alternative to the current sensor using the iron core. A magnetoresistive element is an element whose resistance value changes according to the strength of a magnetic field. For example, a wiring through which a current to be measured flows is arranged near the magnetoresistive element. Then, the resistance of the magnetoresistive element corresponding to the magnetic field generated by the current to be measured flowing through this wiring can be measured, and the current value of the current to be measured can be obtained based on the measurement result.

  As a sensor using a magnetoresistive element, for example, Patent Document 1 discloses a magnetic sensor using a tunnel magnetoresistive effect element. According to Patent Document 1, a bias magnetic field can be applied to an element with less power consumption by flowing a bias current through the lower electrode of the tunnel magnetoresistive element, and the magnitude of the bias magnetic field changes according to the external magnetic field. By doing so, it is possible to improve the magnetic field detection accuracy.

  Patent Document 2 discloses a current sensor configured by stacking a sensor unit using a giant magnetoresistive element (GMR element) that exhibits a giant magnetoresistive effect and a printed circuit board through which a current to be measured flows. Is disclosed. In Patent Document 3, the direction in which a detection current for flowing through a magnetoresistive effect element and detecting the change as a magnetic field change is alternately switched, and the detection current in each direction is supplied. In other words, a configuration is disclosed in which an average value of detected voltages is taken to suppress errors due to the influence of a magnetic field generated by a detection current, and magnetic field detection with higher sensitivity is possible.

  Such a magnetoresistive element has a problem that the detectable current range is narrow because the resistance value is saturated at a predetermined magnetic field strength. In particular, since the current is detected by measuring a resistance value corresponding to a magnetic field generated by the current, it is difficult to detect a weak current.

  The present invention has been made in view of the above, and an object thereof is to enable measurement of a wider current range.

  In order to solve the above-described problems and achieve the object, the first invention includes a free layer whose magnetization direction is reversed by an external magnetic field, a fixed layer whose magnetization direction is fixed, a free layer and a fixed layer, A current sensing device using a magnetoresistive element having a barrier layer that acts as a barrier against current flowing between the free layer and the fixed layer when the magnetization direction is antiparallel, and generates a magnetic field by the current to be measured Switching means for switching whether or not the current to be measured is supplied to the first magnetoresistive element, the second magnetoresistive element, and the second magnetoresistive element in which the wiring to be arranged is arranged at a predetermined distance Measuring means for measuring a voltage drop due to the first magnetoresistive element of the sense current and a voltage drop due to the second magnetoresistive element of the current to be measured, and a voltage due to the first magnetoresistive element at the measuring means Depending on the descent measurement result Control means for controlling the switching means, and the control means is the first measured by the measuring means in a state where the switching means is switched so that the current to be measured is not supplied to the second magnetoresistive element. When the magnitude of the voltage drop due to the magnetoresistive element is less than the threshold value, the switching means is controlled to supply the current to be measured to the second magnetoresistive element.

  In the second invention, the magnetization direction is antiparallel between the substrate, the free layer whose magnetization direction is reversed by an external magnetic field, the fixed layer whose magnetization direction is fixed, and the free layer and the fixed layer. A magnetoresistive portion in which a plurality of thin films including a barrier layer serving as a barrier against a current flowing between the free layer and the fixed layer are stacked on the substrate, an input portion to which a current to be measured is input, and a magnetic field A wiring unit provided on the substrate so as to circulate around the resistance unit, and a switching unit for switching whether to supply the current to be measured input from the input unit to the magnetic resistance unit. .

  According to a third aspect of the present invention, there is provided a free layer whose magnetization direction is reversed by an external magnetic field, a fixed layer whose magnetization direction is fixed, and a free layer when the magnetization direction is antiparallel between the free layer and the fixed layer. Current detecting method of a current detecting device using a magnetoresistive element including a barrier layer that serves as a barrier against a current flowing between a fixed layer and a measuring layer, wherein a wiring for generating a magnetic field by a current to be measured is previously provided A first measuring step for measuring a voltage drop of the sense current by the first magnetoresistive element arranged at a predetermined distance; and a measuring means for measuring a voltage drop by the second magnetoresistive element of the current to be measured. A second measuring step, a switching step in which the switching means switches whether to supply a current to be measured to the second magnetoresistive element, and a control means in which the second magnetoresistive element is switched by the switching step. When the magnitude of the voltage drop measured by the first measurement step is less than the threshold value in a state where the current to be measured is switched so as not to be supplied, the measurement target for the second magnetoresistive element And a control step for controlling the switching step so as to supply current.

  According to the present invention, it is possible to measure a wider current range.

FIG. 1 is a schematic diagram showing a structure of an example of a TMR element as a magnetoresistive element applicable to each embodiment. FIG. 2 is a schematic diagram illustrating an example of magnetoresistive characteristics of the magnetoresistive element. FIG. 3 is a schematic diagram illustrating an example of IV characteristics of the magnetoresistive element. FIG. 4 is a circuit diagram illustrating a configuration of an example of the current detection device according to the first embodiment. FIG. 5 is a flowchart illustrating a measurement procedure of an example of the current detection device. FIG. 6 is a circuit diagram showing a configuration of an example of a current detection device according to the second embodiment. FIG. 7 is a circuit diagram showing a configuration of an example of a current detection device according to the third embodiment. FIG. 8 is a circuit diagram showing a configuration of an example of a current detection device according to the fourth embodiment. FIG. 9 shows a cross-sectional view of an exemplary configuration of the current detection device according to the fifth embodiment. FIG. 10 is a top view showing the configuration of an example of the current detection device according to the sixth embodiment.

  Hereinafter, embodiments of a current detection device, a current detection element, and a current detection method will be described in detail with reference to the accompanying drawings. In each embodiment, a magnetoresistive element using a magnetoresistive effect in which a resistance value changes according to the strength of a magnetic field is used as an element for detecting current. That is, the current value of the current to be measured is measured based on the resistance of the magnetic resistance element according to the magnetic field generated when the current to be measured flows through the wiring arranged in the vicinity of the magnetoresistive element. In each embodiment, a magnetoresistive element is used as a pure resistance in a linear region of IV characteristics, and a current to be measured is directly passed through the magnetoresistive element to measure a current value. By switching the current measurement using the magnetoresistive effect of the magnetoresistive element and the current measurement using the magnetoresistive element as a pure resistance according to the current value of the current to be measured, the current in a wider range Enable measurement.

  Known magnetoresistive elements that can obtain the magnetoresistive effect include GMR (Giant Magneto-Resistance effect) elements, AMR (Anisotropic Magneto Resistance) elements, TMR (Tunnel Magneto-Resistance effect) elements, and the like. In each embodiment, a TMR element is applied as the magnetoresistive element.

  FIG. 1 shows an example of a structure of a TMR element as a magnetoresistive element 10 applicable to each embodiment. In the example of FIG. 1, the magnetoresistive element 10 has a TMR layer configuration including a substrate 20, a seed layer 21, a magnetization fixed layer 22, a tunnel barrier layer 23, a free layer 24, and a cap layer 25.

  As the substrate 20, for example, Si or a thermally oxidized substrate on Si is used. For the substrate 20, a seed layer 21 such as Ta, FeMn, PtMn, IrMn, NiMn, PdPtMn, CrPtMn, CoMn, etc. using an ultra-high vacuum sputtering device, an ion beam sputtering device, an EB (electron beam) vapor deposition device, etc. And a magnetization fixed layer 22 made of alloy thereof or the like. The film thickness of the magnetization fixed layer 22 is set to about 3 nm to 400 nm or more depending on each design value, and preferably 10 nm to 100 nm.

  A tunnel barrier layer 23 is formed with respect to the magnetization fixed layer 22. The tunnel barrier layer 23 is made of, for example, Al—O or MgO, and the film thickness is designed between 0.5 nm to 6 nm, and preferably 1 nm to 4 nm. In particular, when the tunnel barrier layer 23 is made of MgO, an excellent magnetoresistance change rate characteristic can be obtained even with a relatively thick film thickness, so that a large resistance value can be realized by increasing the film thickness.

  Although not shown, when the tunnel barrier layer 23 is composed of an MgO layer, it is also preferable that an amorphous film such as CoFeSiB is formed by as depo and crystallized during annealing. As a result, the rearrangement of MgO is promoted and the crystallinity is enhanced, whereby the magnetoresistance change rate can be remarkably improved, and the detection performance can be further improved.

  The free layer 24 can exhibit sensor characteristics by being made of a material having soft magnetic characteristics such as permalloy (NiFe), supermalloy, CoFe, CoNiFe, and CoZrNb. Further, Ta or the like is deposited as the cap layer 25.

  The magnetoresistive element 10 is completed by forming a desired shape by fine processing using photolithography, EB exposure or the like, and arranging electrodes on the upper and lower sides.

  In the magnetoresistive element 10, between the free layer 24 and the magnetization fixed layer 22, each of which is a magnetic material, electrons conduct tunnel conduction using the oxide layer as the tunnel barrier layer 23, and a tunnel current flows. At that time, in the free layer 24 and the magnetization fixed layer 22, a phenomenon occurs in which the band structures in the magnetic body are symmetrically different and the tunnel probabilities are different depending on whether the magnetization is parallel or antiparallel. By utilizing this phenomenon, it is possible to detect the current flowing in the wiring arranged in the vicinity of the magnetoresistive element 10.

  FIG. 2 shows an example of the magnetoresistance characteristics of the magnetoresistive element 10. Increasing the current flowing through the electrical wiring increases the magnetic field intensity around the wiring. The magnetoresistive element 10 arranged in the vicinity of the wiring has a linear portion in which the resistance value increases at a constant ratio as the magnetic field intensity around the wiring increases as shown in FIG. And a magnetoresistive characteristic consisting of a saturated portion where the resistance value is saturated.

  Here, a critical portion of the magnetoresistive characteristic that shifts from the linear portion to the saturated portion is referred to as a saturation point of the resistance value. Since this saturation point is also a portion (bending point) where the gradient of the portion of transition from the linear portion of the magnetoresistive characteristic to the saturated portion changes rapidly, it is easy to detect. Further, the saturation point is an amount that is uniquely determined by the physical properties of the magnetic material and the exchange interaction generated at the interface between the antiferromagnetic material and the magnetic material, and thus becomes a very accurate critical point. Furthermore, the saturation point can be obtained with good reproducibility even in the manufacturing process of the ordinary magnetoresistive element 10.

  FIG. 3 shows an example of current-voltage characteristics (IV characteristics) in the vicinity of the voltage V = 0 when the voltage V is applied to the magnetoresistive element 10. In a general TMR element, when the cross-sectional area of the element is small, the IV characteristic shows a linear change, and is approximated by a model that is usually determined by the width and height of the tunnel barrier even by voltage application. That is, as illustrated in FIG. 3, in the magnetoresistive element 10, when the applied voltage is in the vicinity of the voltage V = 0, the IV characteristic is a linear region showing a linear change, and in this linear region, the magnetoresistive element 10 is The resistance value can be treated as a fixed pure resistance.

  At this time, it is known that the IV characteristic of the magnetoresistive element 10 has a temperature characteristic of about 0.1% / ° C., which is smaller than that of the semiconductor element. When the voltage or current is measured using the linear region of the IV characteristic in the magnetoresistive element 10, it is preferable to make the temperature characteristic and the magnetic field operation uniform. Further, when the magnetoresistive element 10 is handled as a pure resistance, for example, by interrupting the current of a wiring in the vicinity of the magnetoresistive element 10 through which a current other than the detection target flows, a magnetic field due to the current is prevented from being generated. It is possible to detect a minute current.

  Conventionally, a magnetic sensor using an AMR element or winding has a low sensitivity, such as when current detection is performed using magnetic sensing, or when a magnetic field is directly measured, and a relatively large element is also used when using a semiconductor Hall element. It was necessary to prepare. On the other hand, in recent years, the characteristics of magnetoresistive elements such as GMR elements and TMR elements have been remarkably improved, reaching a few hundred percent at room temperature as of March 2011, and can be expected to be remarkably improved. It is a device. In addition, with the recent miniaturization of LSIs and the like, relatively complicated circuits associated with current detection can be realized as minute element portions of LSIs. Therefore, a new detection method can be realized by using a GMR element or a TMR element, unlike the case of using a conventional AMR element or the like.

  Both the TMR element and the GMR element have a magnetoresistive change because the sense current flows differently depending on the relative angle of magnetization with the magnetization fixed layer with reference to the change of the free layer with respect to the magnetic field. In these elements, since the free layer itself is a detection layer for detecting a magnetic field, it is possible to improve element characteristics by appropriately utilizing the characteristics of the free layer in detecting a weak magnetic field. In addition, due to the effect of magnetization reversal by current injection through a magnetic material, detection sensitivity can be improved when current is to be detected. Thereby, even a minute current can be detected, and the output voltage ratio of the detection signal can be improved even when the same current is detected.

  In the magnetoresistive element 10 that is a TMR element applicable to each embodiment, a change in magnetoresistance is obtained according to the magnetization state of the free layer 24. As described with reference to FIG. 1, the free layer 24 is formed using a material having soft magnetic properties such as permalloy, supermalloy, CoFe, CoZrNb, CoFeB, CoFeSiB, and FeAlSi, or a material having semi-hard magnetic properties. To do. Each material forming the free layer has a characteristic magnetic hysteresis loop, and shows a curve that reaches magnetization saturation when the magnetization changes with a switch-like square shape or shows a linear change. Moreover, each material which forms a free layer shows a linear characteristic, when a linear measurement is required.

  Further, in the TMR element, when the magnetization exhibits a switching characteristic, it is possible to detect the current by using a magnetoresistive curve having a square shape as necessary. Further, measurement of a very small current region can be detected using a linear region in which the TMR element is regarded as a pure resistance element.

  In each embodiment, it is possible to detect a current in a wider range by switching between the linear portion of the magnetoresistance curve of the TMR element shown in FIG. 2 and the linear region of the IV characteristic shown in FIG. Yes.

  That is, in the straight line portion of the magnetoresistive curve, the magnetic resistance element 10 detects a magnetic field caused by the measurement target current flowing in the wiring arranged in the vicinity of the magnetoresistive element 10, thereby obtaining the current value of the measurement target current. In this case, since a measurement target current does not flow to the magnetoresistive element 10, a relatively large current can be used as the measurement target current. On the other hand, in the minute current region, the current value of the current to be measured is obtained by using the linear region of the IV characteristic shown in FIG. 3 and using the magnetoresistive element 10 as a pure resistance. In this case, a current to be measured is passed through the magnetoresistive element 10 and the voltage drop across the magnetoresistive element 10 is measured to obtain the current value of the current to be measured.

(First embodiment)
FIG. 4 is a circuit diagram illustrating a configuration of an example of the current detection device according to the first embodiment. A current to be measured I _M is supplied to the wiring 60 via the switch 50. In order to measure the current to be measured I _M , a plurality of magnetoresistive elements 10 ₀ , 10 ₁ , 10 ₂ and 10 ₃ are provided.

  The switch 50 controls which one of the terminal 50 a and the terminal 50 b is selected by a switching signal 41 supplied from the detection control unit 40. The switch 50 can be configured by utilizing switching characteristics of a semiconductor element such as a transistor, for example. Not limited to this, the switch 50 may be realized by a mechanical structure.

Detection control unit 40, the magnetoresistive element 10 _0, 10 _1, 10 ₂ and 10 ₃ a voltage drop Vd ₀ to Vd ₃ are the respective detection output is supplied. The detection control unit 40 outputs the switching signal 41 described above according to the supplied voltage drops Vd _{0 to} Vd ₃ .

Among the plurality of magnetoresistive elements 10 ₀ , 10 ₁ , 10 _2, and 10 ₃ , the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ use the linear portion of the magnetoresistive curve to allow current to flow through the wiring 60. The current I _M to be measured is detected and measured based on the magnetic field generated by this. When measuring the measurement target current I _M using these magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ , the switch 50 is switched in advance so that the terminal 50a is selected.

As is well known, the magnetic field strength H caused by the current I flowing through the wiring 60 is proportional to the magnitude of the current I and inversely proportional to the distance r from the wiring 60. Further, the magnetoresistance curve of the magnetoresistive element 10 has a saturation point at a certain magnetic field strength as described with reference to FIG. Therefore, the current to be measured can be measured in a wider range by arranging the plurality of magnetoresistive elements 10 ₁ , 10 _2, and 10 _{3 such} that the distances r from the wiring 60 are different in stages.

In the example of FIG. 2, it is arranged at a distance r ₁ magnetoresistance element 10 ₁ of the magneto-resistive element 10 _1, 10 ₂ and 10 ₃ are most close to the wire 60. Hereinafter, the magnetoresistive element 10 ₃ is disposed at a distance r ₃ farthest from the wiring 60, and the magnetoresistive element 10 ₂ is disposed at an intermediate distance r ₂ . In this example, elements applicable as the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ are not limited to TMR elements, and may be GMR elements, for example.

For example, a constant current source 30 ₁ supplies a constant current value Ic ₁ to the magnetoresistive element 10 ₁ , and the voltage drop Vd ₁ at points A ₁ and B _{1 at} both ends is measured. As an example, the resistance value of the magnetoresistive element 10 ₁ is obtained from the value of the voltage drop Vd ₁ and the current value of the sense current Ic ₁ . Then, the magnetic field strength is obtained from the magnetoresistance curve of FIG. 2 based on the obtained resistance value, and the magnitude of the measurement target current I _M flowing through the wiring 60 is obtained based on the distance r ₁ .

Note that the measurement circuit for measuring the voltage drop Vd ₁ is omitted in FIG. 4 in order to avoid complexity. Measurement of the voltage drop Vd ₀ to Vd ₃ in the magnetoresistive element 10 _{0 -} 10 _3, typical voltage measurement circuit can be carried out using. As an example, it is conceivable that the voltage at both ends of each of the magnetoresistive elements 10 ₀ to 10 ₃ is converted into a digital value by an A / D conversion circuit provided with a high impedance voltage amplification circuit on the input side and output. A voltage measurement circuit may be provided for each of the magnetoresistive elements 10 ₀ to 10 ₃ , or a common voltage measurement circuit may be switched and used.

Calculation of the value of the measured current I _M based on the values of these voltage drops Vd ₁ is carried out, for example, in the detection controller 40. As an example, the detection control unit 40 stores the value of the distance r ₁ between the wiring 60 and the magnetoresistive element 10 ₁ , the value of the sense current Ic ₁ , and the magnetoresistive curve of the magnetoresistive element 10 ₁ in advance. To keep. When a voltage drop Vd ₁ across the magnetoresistive element 10 ₁ is supplied from a measurement circuit (not shown), this voltage drop Vd ₁ , the held distance r ₁ , the magnetoresistive curve of the magnetoresistive element 10 ₁ , and The value of the measurement target current I _M is calculated from the sense current Ic ₁ .

The same applies to the magnetoresistive elements 10 ₂ and 10 ₃ . A sense current Ic ₂ having a constant current value is supplied to the magnetoresistive element 10 ₂ by a constant current source 30 _2, voltage drops Vd ₂ at points A ₂ and B _{2 at} both ends are measured, and these sense current Ic ₂ and voltage drop are measured. The magnetic field strength is obtained from Vd ₂ and the magnitude of the measurement target current I _M is obtained based on the obtained magnetic field strength and the distance r ₂ . In addition, a constant current source 30 ₃ is passed through the magnetoresistive element 10 ₃ with a constant current value Ic ₃ , and voltage drops Vd ₃ at points A ₃ and B _{3 at} both ends are measured, and these sense currents Ic ₃ and The magnetic field strength is obtained from the voltage drop Vd _3, and the magnitude of the measurement target current I _M is obtained based on the obtained magnetic field strength and the distance r ₃ .

Here, it has been described that the sense currents Ic ₁ , Ic _2, and Ic ₃ are supplied from the different constant current sources 30 ₁ , 30 _2, and 30 ₃ to the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ , respectively. However, this is not limited to this example. That is, the sense current Ic having the same current value may be supplied from the common constant current source to the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ .

On the other hand, a plurality of magnetoresistive elements 10 _0, 10 _1, 10 of the _two and 10 _3, the magnetoresistive element 10 _0, the measured current I _M by utilizing the linear region of the IV characteristics described with reference to FIG. 3 Perform detection and measurement. In this case, switched to the terminal 50b is selected in the switch 50, measured by flowing the target current I _M directly to the magnetoresistive element 10 _0, the voltage between points A ₀ and B ₀ at both ends of the magnetoresistive element 10 ₀ to measure the drop Vd _0. Resistance in the linear region of the magnetoresistive element 10 ₀ R ₀ can be known in advance based on the IV characteristic of the magnetoresistive element 10 _0. Therefore, the value of the measurement target current I _M can be obtained from the resistance value R ₀ and the measured voltage drop Vd ₀ .

Calculation of the value of the measured current I _M based on the value of the voltage drop Vd _0, like the above, for example, performed by the detection controller 40. As an example, the detection control unit 40 holds the resistance value R ₀ at the linear region of the IV characteristic of the magnetic resistance element 10 such as ₀ in advance in the memory. Then, calculate the voltage drop Vd ₀ at both ends of the magnetoresistive element 10 ₀ is supplied from a not shown measurement circuit, the voltage drop Vd _0, the resistance value R ₀ Metropolitan held, the measured current I _M To do.

Magnetoresistive elements 10 ₀ used as a pure resistance, may be destroyed and flow excessive current. On the other hand, since no current flows directly through the magnetoresistive elements 10 ₁ to 10 ₃ as described above, the magnetoresistive elements 10 ₁ to 10 ₃ are not destroyed even if the value of the current to be measured I _M is large. Therefore, the detection control unit 40 controls the switching of the switch 50 based on the measurement result by the magnetic resistance elements 10 ₁ to 10 _3, to prevent excessive current flows through the magnetoresistive element 10 _0.

FIG. 5 is a flowchart showing a measurement procedure of an example of the current detection device. Each process of the flowchart of FIG. 5 is controlled by, for example, the detection control unit 40. Ahead of measurement, the detection control unit 40 controls the switch 50 so that the terminal 50a side is selected, a large current unexpected magnetoresistive element 10 ₀ is prevented from flowing directly.

The detection control unit 40 measures the voltage drops Vd ₁ , Vd _2, and Vd ₃ of the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ while the switch 50 selects the terminal 50a (step S10). Then, the detection control unit 40 includes a voltage drop Vd ₁ to Vd ₃ obtained in the measurement, the previously retained, the distance r ₁ ~r ₃ and magnetoresistance curves for lines 60 of the respective magnetoresistance elements 10 ₁ to 10 ₃ Then, the measurement target current I _M is calculated based on the sense currents Ic _{1 to} Ic ₃ .

In the next step S11, the detection control unit 40 determines whether or not the measurement result of the measurement unit having the lowest measurement range is less than the threshold value. In the case of the example in FIG. 4, the measurement unit having the lowest measurement range is the magnetoresistive element 10 ₁ disposed at the closest distance d ₁ from the wiring 60. Accordingly, the detection control unit 40 determines whether the voltage drop Vd ₁ of the magnetoresistive element 10 ₁ is less than the threshold. Here, the threshold value is a voltage value in the linear region of the IV characteristic of the magnetoresistive element 10 _0.

If it is determined that the voltage drop Vd ₁ is less than the threshold value, the detection control unit 40 shifts the process to step S12. In step S12, the detection control unit 40, a switch 50, and controls so that the terminal 50b i.e. magnetoresistive element 10 ₀ side is selected to measure the voltage drop Vd ₀ of the magnetoresistive element 10 _0.

The detection control unit 40 obtains the measurement target current I _M based on the voltage drop Vd ₀ obtained by the measurement and the resistance value R ₀ in the linear region of the IV characteristic in the magnetoresistive element 10 ₀ held in advance. Then, the process proceeds to step S13, and the obtained measurement target current I _M is output as a measurement result.

On the other hand, when the value of the voltage drop Vd ₁ of the magnetoresistive element 101 is equal to or more than the threshold value in step S11, the process control proceeds to step S13, the output as the measurement result measured current I _M obtained in Step S10 To do.

Thus, in accordance with the measured current I _M, measured current I _M by the select whether flow to any of the wiring 60 side and the magnetoresistive element 10 ₀ side, a current can be measured in a wider range Become. That is, in a region where the measurement target current I _M is large, current measurement is performed by using a magnetoresistive characteristic of the magnetoresistive element 10 and a method in which no current flows directly through the element. Since the measurement target current I _M does not flow directly to the element, a large current can be handled. On the other hand, in a region where the measurement target current I _M is very small, a minute current can be measured with high accuracy by performing current measurement using a linear region of the IV characteristic in the magnetoresistive element 10.

(Second Embodiment)
In this second embodiment, the current sensing device according to the first embodiment described with reference to FIG. 4, the magnetoresistive element 10 ₀ performing current measurement using the linear region of the IV characteristic, a magnetic resistance characteristic a magnetoresistive element 10 ₁ measurement range of the magnetoresistive elements 10 ₁ to 10 ₃ is the most low current to perform current measurements using, configured using a magnetoresistive element 10 of 1 in common.

  FIG. 6 is a circuit diagram showing a configuration of an example of a current detection device according to the second embodiment. In FIG. 6, the same reference numerals are given to the portions common to FIGS. 1 and 4 described above, and detailed description thereof is omitted. The current detection device of FIG. 6 includes a magnetoresistive element 10, a constant current source 30, a detection control unit 40, switches 51 and 52, and a wiring 60. The magnetoresistive element 10 is arranged at a distance r with respect to the wiring 60.

In the configuration of FIG. 6, the measurement unit that measures the voltage drop Vd between the points A and B at both ends of the magnetoresistive element 10 is omitted in order to avoid complexity. In addition to the configuration shown in FIG. 6, a larger number of magnetoresistive elements arranged at a predetermined distance from the wiring 60 may be arranged like the magnetoresistive elements 10 ₂ and 10 ₃ shown in FIG. Good.

The switch 51 switches whether the measurement target current I _M flows through the wiring 60 (ON) or not (OFF) according to the switching signal 42 output from the detection control unit 40. The switch 52 switches which of the measurement target current I _M and the sense current Ic is supplied to the magnetoresistive element 10 according to the switching signal 42. The switch 51 and the switch 52 are controlled in conjunction with a switching signal 42 from the detection control unit 40.

That is, the switch 51 and switch 52, when the measured current I _M flowing on the wiring 60, as the sense current Ic flows to the magnetic resistance element 10, are switched, respectively. On the other hand, when the measurement target current I _M is supplied to the magnetoresistive element 10, switching is performed so that the measurement target current I _M is not supplied to the wiring 60.

More specifically, when the magnetoresistive element 10 measures the measurement target current I _M using the magnetoresistive characteristic, the detection control unit 40 turns on the switch 51 and the terminal 52b of the switch 52 is Control to be selected. Also, the detection control unit 40, when the magnetic resistance element 10 performs measurement of the measurement target current I _M by utilizing the linear region of the IV characteristic, the switch 52 is OFF, and the terminal 52a is selected in the switch 52 To control.

The measurement procedure of the measurement target current I _M is substantially the same as the procedure described using the flowchart of FIG. 5 in the first embodiment. That is, the detection control unit 40 controls the switch 51 to be turned ON and the switch 52 to select the terminal 52b prior to measurement. As a result, the measurement target current I _M flows through the wiring 60.

In this state, the detection control unit 40 measures the voltage drop Vd of the sense current Ic caused by the magnetoresistive element 10 (step S10). The detection control unit 40 performs threshold determination on the measured voltage drop Vd (step S11), and outputs the measurement target current I _M obtained based on the voltage drop Vd if the voltage drop Vd is equal to or greater than the threshold. (Step S13). On the other hand, if the voltage drop Vd is less than the threshold value, the detection control unit 40 controls the switch 51 to be turned OFF and the switch 52 to select the terminal 52a, so that the current to be measured with respect to the magnetoresistive element 10 is measured. flow of I _M. Then, the voltage drop Vd ′ of the measurement target current I _M by the magnetoresistive element 10 is measured, and the measurement target current I _M obtained based on the measurement result is output (step S13).

In the above description, the switch 51 for selecting whether or not to pass the measurement target current I _M to the wiring 60 is provided, but this is not limited to this example. That is, the switch 51 may be omitted if the change in resistance due to the magnetoresistance characteristic of the magnetoresistive element 10 when the current in the linear region of the IV characteristic in the magnetoresistive element 10 flows through the wiring 60 is extremely small.

In the above description, the distance between the magnetoresistive element 10 and the wiring 60 is one kind of distance r, but this is not limited to this example. For example, wiring a plurality of distances are different with respect to the magnetic resistance elements 10 60, 60, arranged ..., depending on the magnitude of the measured current I _M, the plurality of wires by a switch 60, 60, ... switch the You may do it. By doing so, it is possible to perform current measurement in a very wide range with one magnetoresistive element 10.

  As described above, in the second embodiment, the current detection using the magnetoresistive characteristics of the magnetoresistive element 10 and the current detection using the linear region of the IV characteristics are performed by using one magnetoresistive element 10. It is done by switching. Therefore, it is possible to perform current detection in a wider range using one magnetoresistive element 10.

(Third embodiment)
In the second embodiment described above, when the current detection using the magnetoresistive characteristic and the current detection using the linear region of the IV characteristic are performed by using one magnetoresistive element 10 in common, the magnetoresistance Which of the sense current Ic and the measurement target current I _M is supplied to the element 10 is completely switched. In contrast, in the third embodiment, when using the linear region of the IV characteristic perform current detection of the measurement target current I _M in the magnetoresistive element 10, measured current to the sense current Ic I _M is connected, and the voltage drop Vd due to the magnetoresistive element 10 is measured including the voltage increase at that time.

  FIG. 7 is a circuit diagram showing a configuration of an example of the current detection device according to the third embodiment. In FIG. 7, the same reference numerals are given to the portions common to FIG. 6 described above, and detailed description thereof is omitted. The current detection device of FIG. 7 includes a magnetoresistive element 10, a constant current source 30, a detection control unit 40, a switch 53, and a wiring 60. The magnetoresistive element 10 is arranged at a distance r with respect to the wiring 60.

The switch 53 selects which of the wiring 60 and the magnetoresistive element 10 the measurement target current I _{M is} to flow according to the switching signal 43 output from the detection control unit 40. That is, the switch 53 causes the measurement target current I _M to flow through the wiring 60 when the terminal 53 a is selected by the switching signal 43, and causes the measurement target current I _M to flow through the magnetoresistive element 10 when the terminal 53 b is selected.

  Further, a sense current Ic is supplied from the constant current source 30 to the magnetoresistive element 10 regardless of which of the terminals 53a and 53b is selected in the switch 53. Therefore, when the terminal 53 a is selected in the switch 53, only the sense current Ic flows through the magnetoresistive element 10, the distance r from the wiring 60, the sense current Ic, and the magnetic resistance of the magnetoresistive element 10. The voltage drop Vd is measured based on the resistance characteristics.

On the other hand, when the terminal 53 b is selected in the switch 53, the current to be measured I _M is supplied to the magnetoresistive element 10 while the sense current Ic is supplied to the magnetoresistive element 10. Will be. In this case, it is assumed that the measurement target current I _M does not flow into the constant current source 30 by adjusting the impedance of the output stage of the constant current source 30 or using a diode.

That is, the current flowing through the magnetoresistive element 10 is (measurement target current I _M + sense current Ic), and the voltage drop Vd in the magnetoresistive element 10 resists the resistance in the linear region of the IV characteristic of the magnetoresistive element 10. _Assuming R ₀ , Vd = (I _M + Ic) R ₀ . By transforming this equation, the measurement target current I _M is calculated as I _M = Vd / R ₀ −Ic.

The measurement procedure of the measurement target current I _M is substantially the same as the procedure described using the flowchart of FIG. 5 in the first embodiment. That is, the detection control unit 40 controls the switch 53 so that the terminal 53 a is selected prior to measurement, and causes the measurement target current I _M to flow through the wiring 60. In this state, the detection control unit 40 measures the voltage drop Vd of the sense current Ic due to the magnetoresistive element 10 (step S10), and performs threshold determination on the measured voltage drop Vd (step S11). If the voltage drop Vd is equal to or greater than the threshold value, the detection control unit 40 outputs the measurement target current I _M obtained based on the voltage drop Vd (step S13). If the voltage drop Vd is less than the threshold value, the switch 53 is controlled so that the terminal 53b is selected, and the measurement target current I _M is supplied to the magnetoresistive element 10. Then, the voltage drop Vd of the magnetoresistive element 10 of (measurement target current I _M + sensor current Ic) is measured, and the measurement target current I _M obtained as described above based on the measurement result is output (step S13).

  As described above, in the third embodiment, current detection using the magnetoresistive characteristic of the magnetoresistive element 10 and current detection using the linear region of the IV characteristic are performed by using one magnetoresistive element 10. It is done by switching. Therefore, it is possible to perform current detection in a wider range using one magnetoresistive element 10. At this time, only one switch is required to switch the usage pattern of the magnetoresistive element 10.

(Fourth embodiment)
Next, a fourth embodiment will be described. FIG. 8 is a circuit diagram showing a configuration of an example of the current detection device according to the fourth embodiment. The circuit diagram shown in FIG. 8 corresponds to the configuration example of the current detection device according to the first embodiment shown in FIG. In FIG. 8, the same reference numerals are given to portions common to FIG. 4, and detailed description thereof is omitted.

The fourth embodiment is different from the measured current magnetoresistance element 10 ₁ for measuring the I _M, 10 ₂ and 10 ₃ each use a magnetoresistive characteristics, flows measured current I _M wirings 61 Rotate and arrange. At this time, the wiring 61 is, for example in a plane with respect to the magnetoresistive element 10 _1, in other words, on a plane parallel to the layers constituting the magnetoresistive element 10 _1, orbiting in the magnetoresistive element 10 ₁ Then, the wiring 61 is arranged.

In FIG. 8, similarly to FIG. 4 described above, the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ perform current detection using magnetoresistive characteristics. In this case, for example, in the measurement unit 11 ₁ , the wiring 61 is arranged around the magnetoresistive element 10 _{1 at} a distance r ₁ . Similarly, the measurement unit 11 _2, line 61 away farther distance r ₂ from the distance r ₁ with respect to the magnetoresistive element 10 ₂ is disposed orbiting, the measuring unit 11 _3, with respect to the magnetoresistive element 10 ₃ Thus, the wiring 61 is arranged around the distance r ₃ which is far from the distance r ₂ .

As for the magnetoresistive element 10 ₀ for sensing the linear region of the measured current I _M with the IV characteristics, because there is no place where any change the configuration of FIG. 4, description thereof will be omitted here. Further, the detection procedure of the measurement target current I _M with the configuration of FIG. 8 is the same as the procedure described with reference to the flowchart of FIG. 5 in the first embodiment, and thus detailed description thereof is omitted here.

In this way, by arranging the wiring 61 so as to circulate in a plane with respect to the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ , the vector direction of the magnetic field generated by the measurement target current I _M flowing through the wiring 61 is changed to the substrate surface. It becomes perpendicular to (film surface). As a result, the design of the magnetoresistive elements 10 ₁ , 10 _2, and 10 ₃ in consideration of the influence of the demagnetizing field and the distribution error of the magnetic field strength generated in the wiring 61 can be reduced. Therefore, the current detection accuracy is improved, and more accurate measurement in a wide range of the measurement target current I _M flowing through the wiring 61 is possible.

  Note that the configuration in which the wiring through which the current to be measured flows is circulated with respect to the magnetoresistive element that performs current measurement using magnetoresistive characteristics according to the fourth embodiment is the same as in the second and third embodiments described above. It is also applicable to.

(Fifth embodiment)
Next, a fifth embodiment will be described. In the above-described fourth embodiment, the wiring through which the measurement target current I _M flows is arranged around the substrate surface (film surface) of the magnetoresistive element 10 in parallel. On the other hand, in the fifth embodiment, the wiring through which the measurement target current I _M flows is arranged around the lamination direction of the thin films of the magnetoresistive element 10.

  FIG. 9 shows a cross-sectional view of an example of the configuration of the current detection device according to the fifth embodiment. The current detection device according to the fifth embodiment has a magnetoresistive element 10 ′ and a thin film with respect to the magnetoresistive element 10 ′ with respect to a substrate 120 which is a MOS LSI (Metal-Oxide Semiconductor Large-Scale Integration) region. And a loop-shaped wiring portion that circulates in the stacking direction.

  In FIG. 9, buried metal portions 106 and 115 for wiring are formed in the MOS LSI region 120, and wiring metal layers A 105 and 114 are formed in the buried metal portions 106 and 115, respectively. The substrate 20 of the magnetoresistive element 10 ′ is formed on the wiring metal layer A 104 via the lower conductor portion 104. A seed layer 21, an AFM (antiferromagnetic) layer 26, a pinned layer 27, a tunnel barrier layer 23, a free layer 24 and a cap layer 25 are sequentially formed on the substrate 20 to form a magnetoresistive element 10 ′. .

  A wiring metal layer B102 is formed on the cap layer 25 of the magnetoresistive element 10 ′ via the upper conductor portion 103, and further, a buried metal portion 101 for wiring is formed, and a wiring metal layer C100 is formed thereon. The

  On the other hand, a wiring member 113 is formed on the wiring metal layer A 114, and a wiring metal layer B 112 is formed on the wiring member 113. The wiring metal layer A114, the wiring member 113, and the wiring metal layer B112 are looped around the magnetoresistive element 10 ′ at a predetermined distance along the thin film lamination direction of the magnetoresistive element 10 ′. A wiring part is configured. A buried metal portion 111 for wiring is formed on the wiring metal layer B, and a wiring metal layer C110 is formed thereon.

By adopting a configuration in which the loop wiring portion circulates along the thin film stacking direction of the magnetoresistive element 10 ′, the vector direction of the magnetic field generated by the current to be measured I _M is parallel to the substrate surface (film surface). It becomes. This improves the design of the magnetoresistive element 10 ′ in consideration of the influence of the demagnetizing field and the accuracy with respect to the magnetic field intensity generated in the loop-shaped wiring portion, and makes the measurement target current I _M flowing through the loop-shaped wiring portion more accurate. Measurement is possible.

  Further, according to the fifth embodiment, the magnetoresistive element 10 ′ and the loop-shaped wiring portion can be configured in the manufacturing process of the integrated circuit made of a semiconductor such as the MOS LSI region 120. Therefore, cost reduction and size reduction can be achieved. In addition, in a multilayer wiring such as a semiconductor integrated circuit, a configuration arranged perpendicular to the element plane of the magnetoresistive element 10 ′ can be taken relatively easily, so that a closer three-dimensional loop structure has a relatively small area. It can be realized with a small size and high sensitivity.

  Furthermore, the MOS LSI region 120 can incorporate other circuits connected to the magnetoresistive element 10 '. In the example of FIG. 8, a switch circuit that switches an input end of a measurement target current and whether to supply the measurement target current input from the input end to the loop wiring portion or the magnetoresistive element 10 ′ is provided as a MOS. The LSI area 120 can be incorporated. The input end of the current to be measured may be one that inputs the current to be measured from the outside of the MOS LSI area 120 or may be internal to the MOS LSI area 120.

Furthermore, in the example of FIG. 8, it can be considered that a circuit for causing the sense current Ic to flow to the magnetoresistive element 10 ′ is incorporated in the MOS LSI region 120. In this case, for example, a portion included in the measurement unit 11 ₁ of the wiring 61 corresponds to a loop-shaped wire portion. Also, the detection control unit 40 can be incorporated in the MOS LSI region 120.

Moreover, the structure of FIG. 9 can be combined with the above-mentioned 2nd Embodiment or 3rd Embodiment. As an example, when the configuration of FIG. 9 is applied to the third embodiment shown in FIG. 7, the output terminal of the constant current source 30 is connected to the wiring metal layer C100 and the wiring metal layer A105, respectively, and the voltage drop The measurement ends of Vd are connected to each other. Further, a path through which the current to be measured I _M flows is connected to the wiring metal layer C110 and the wiring metal layer A114.

Further, the switch 53 in the configuration of FIG. 7 is incorporated in the MOS LSI region 120. In this case, in the switch 53, the terminal 53 a is connected to the metal wiring part A 114 via the buried metal part 115, and the terminal 53 b is connected to the wiring metal layer A 105 via the buried metal part 106. In contrast to this configuration, a detection unit 40, a constant current source 30, and a measurement unit for measuring the voltage drop Vd of the magnetoresistive element 1 ′ can be further incorporated in the MOS LSI region 120. With such a configuration, a measurement element capable of measuring the measurement target current I _M in a wider range can be formed as one current detection element.

(Sixth embodiment)
Next, a sixth embodiment will be described. In the sixth embodiment, similarly to the above-described fifth embodiment, the loop-shaped wiring portion arranged so as to circulate along the lamination direction of the magnetoresistive element 10 ′ and the thin film of the magnetoresistive element 10 ′. Are created in the manufacturing process of the semiconductor integrated circuit. At that time, two loop-shaped wiring portions are formed so as to sandwich the magnetoresistive element 10 ′ at a predetermined distance from the magnetoresistive element 10 ′. That is, a Helmholtz coil structure is formed by two loop-shaped wiring portions sandwiching the magnetoresistive element 10 ′.

  FIG. 10 is a top view showing the configuration of an example of the current detection device according to the sixth embodiment. A magnetoresistive element 10 'is formed in the MOS LSI region 120 as described with reference to FIG. Then, two loop wiring portions 130A and 130B are formed so as to be spaced apart from the magnetoresistive element 10 'by a predetermined distance and sandwich the magnetoresistive element 10'.

According to this configuration, the design of the magnetoresistive element 10 ′ in consideration of the influence of the demagnetizing field and the uniformity of the accuracy with respect to the magnetic field strength generated in the loop wiring portions 130A and 130B are improved, and the loop wiring portion is more accurate measurement of the measurement target current I _M flowing through is possible. In particular, the two loop wiring portions 130A and 130B are arranged so as to sandwich the magnetoresistive element 10 ′ to form a Helmholtz coil structure, the positioning rules are relaxed, and more accurate current detection is possible.

10, 10 ₀ , 10 ₁ , 10 ₂ , 10 ₃ , 10 ′ Magnetoresistive element 30, 30 ₁ , 30 ₂ , 30 ₃ Constant current source 40 Detection control unit 41, 42, 43 Switching signal 50, 51, 52, 53 Switch 60, 61 wiring

JP 2010-145241 A Japanese Patent Laid-Open No. 2002-082136 JP 2004-184150 A

Claims (11)

A free layer in which the direction of magnetization is reversed by an external magnetic field, a fixed layer in which the direction of magnetization is fixed, and the free layer and the fixed layer when the direction of magnetization is antiparallel between the free layer and the fixed layer. A current detection device using a magnetoresistive element including a barrier layer that serves as a barrier against a current flowing between
A first magnetoresistive element in which a wiring for generating a magnetic field by a current to be measured is disposed at a predetermined distance;
A second magnetoresistive element;
Switching means for switching whether to supply a current to be measured to the second magnetoresistive element;
Measuring means for measuring a voltage drop of the sense current by the first magnetoresistive element and a voltage drop of the current to be measured by the second magnetoresistive element;
Control means for controlling the switching means according to the measurement result of the voltage drop by the first magnetoresistive element in the measuring means,
The control means includes
The magnitude of the voltage drop due to the first magnetoresistive element measured by the measuring means when the switching means is switched so that the current to be measured is not supplied to the second magnetoresistive element. A current detection device that controls the switching means to supply the current to be measured to the second magnetoresistive element when it is less than a threshold value. 2. The current detection device according to claim 1, wherein the threshold value is a value in a linear region in an IV characteristic of the second magnetoresistive element. 3. The current detection device according to claim 1, wherein the first magnetoresistive element and the second magnetoresistive element use one magnetoresistive element in common. The switching means is
4. The current detection device according to claim 1, wherein the current detection target is switched to which of the wiring and the second magnetoresistive element is supplied. 5. 5. The current detection device according to claim 1, wherein the wiring is provided around the first magnetoresistive element. 6. The magnetoresistive element is formed by laminating a plurality of thin films including the free layer, the barrier layer, and the fixed layer on a substrate,
6. The current detection device according to claim 1, wherein the wiring is provided around the first magnetoresistive element along a thin film stacking direction. . The current detection device according to claim 6, wherein at least the switching unit among the measurement unit, the switching unit, and the control unit is configured on the substrate. 8. The current detection device according to claim 1, wherein the wiring has a Helmholtz coil structure including two parallel loops sandwiching the first magnetoresistive element. 9. 9. The current detection device according to claim 1, wherein the first magnetoresistive element and the second magnetoresistive element are tunnel type magnetoresistive elements. 10. A substrate,
A free layer in which the direction of magnetization is reversed by an external magnetic field, a fixed layer in which the direction of magnetization is fixed, and the free layer and the fixed layer when the direction of magnetization is antiparallel between the free layer and the fixed layer. A magnetoresistive portion in which a plurality of thin films including a barrier layer serving as a barrier against a current flowing between are stacked on the substrate;
An input unit to which a current to be measured is input;
A wiring portion that circulates around the magnetoresistive portion and is provided on the substrate;
A current detection element, comprising: a switching unit that switches whether to supply the current to be measured input from the input unit to the magnetoresistive unit. A free layer in which the direction of magnetization is reversed by an external magnetic field, a fixed layer in which the direction of magnetization is fixed, and the free layer and the fixed layer when the direction of magnetization is antiparallel between the free layer and the fixed layer. A current detection method of a current detection device using a magnetoresistive element including a barrier layer that serves as a barrier against a current flowing between
A first measuring step in which the measuring means measures a voltage drop of the sense current caused by the first magnetoresistive element in which the wiring for generating a magnetic field by the current to be measured is disposed at a predetermined distance;
A second measuring step in which the measuring means measures a voltage drop of the current to be measured by the second magnetoresistive element;
A switching step of switching whether or not the switching means supplies a measurement target current to the second magnetoresistive element;
The magnitude of the voltage drop measured by the first measurement step in a state where the control means is switched so that the current to be measured is not supplied to the second magnetoresistive element by the switching step. And a control step for controlling the switching step so as to supply the current to be measured to the second magnetoresistive element when it is less than a threshold value.

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