JP6465725B2 - Current detection device and magnetic field detection device using the same - Google Patents

Description

  The present invention relates to a current detection device that detects the intensity of a current flowing through a conductor, and a magnetic field detection device using the current detection device.

  In recent years, as a magnetoresistive effect element, a tunnel magnetoresistive effect (TMR) element having a larger magnetoresistive ratio (MR ratio) than a conventional anisotropic magnetoresistive effect element or the like, or a TMR (tunnel magnetoresistive effect) element or the like Giant Magneto-Resistance effect (GMR) elements have been developed and applied to sensors, magnetic heads, magnetic recording devices, and the like.

  As a sensor using a TMR element or a GMR element, a current detection device that detects the intensity of the current flowing through the conductor by detecting a magnetic field induced by the current flowing through the conductor, or this current detection device in the magnetic field. There is a magnetic field detection device that detects the strength of a magnetic field by arranging the conductor so as to generate a magnetic field that cancels the magnetic field, passing a current through the conductor, and detecting the current intensity at that time.

  Here, the magneto-resistance (MR) effect is a phenomenon in which the resistance of a substance changes according to the strength and direction of an external magnetic field. Therefore, it is used for current detection by detecting a minute magnetic field such as geomagnetism, detecting a magnetic field induced by a minute current, and reading information recorded at a high density as a magnetization direction on a magnetic recording medium. .

  The GMR element has a multilayer structure of a ferromagnetic film, a metal film, and a ferromagnetic film, and the TMR element has a multilayer structure of a ferromagnetic film, an insulating film, and a ferromagnetic film. In these magnetoresistive elements, one of the ferromagnetic films is a first magnetic layer, that is, a fixed layer, whose magnetization direction does not change with respect to an external magnetic field. On the other hand, the ferromagnetic film laminated on the opposite side across the first magnetic layer and the metal film or insulating film is the second magnetic layer whose magnetization direction rotates in the direction of the external magnetic field, that is, a free layer. .

  At this time, in the case of a GMR element, the direction of the spin between the first magnetic layer and the second magnetic layer is changed in parallel, that is, from 0 ° to antiparallel, that is, 180 ° by an external magnetic field. A resistance change is caused due to a change in the probability of electron scattering at the interface between the metal film and the ferromagnetic film. On the other hand, in the case of a TMR element, the resistance is changed by changing the tunnel current between two types of ferromagnetic films with an insulating film therebetween. Therefore, a change in the magnetic field can be detected as a change in the resistance of the element.

  The fixed layer in these magnetoresistive effect elements is exchange coupled with the ferromagnetic layer in order to fix the magnetization direction. On the other hand, it is generally used that the second magnetic layer that separates the fixed layer from the metal film or insulating film has a spin valve structure that can move freely with respect to an external magnetic field. The magnetoresistive effect element having the spin valve structure can weaken the magnetic coupling between the second magnetic layer and the first magnetic layer, and can increase the sensitivity of the free layer magnetization to the external magnetic field. Is possible.

  Further, since the resistance change of the TMR element and the GMR element with high sensitivity to the magnetic field, it is possible to detect a minute current with high accuracy by detecting the magnetic field induced by the current. At this time, in order to detect the magnetic field induced by the current flowing through the conductor using the magnetoresistive element, it is necessary to bring the element close to the conductor through which the detection target current flows. This is because the S / N ratio between the magnetic field generated by the current to be detected and the magnetic field existing as the environmental noise magnetic field must be increased.

  However, a highly sensitive magnetoresistive element has a small magnetic field range that can be detected as a trade-off, that is, a dynamic range. This is because the maximum MR ratio of the magnetoresistive effect element is determined depending on the materials of the first magnetic layer material and the second magnetic layer. Therefore, when measuring currents with greatly different intensities, prepare multiple magnetoresistive elements with different sensitivities or adjust the distance from the conductor to change the strength of the magnetic field induced by the current flowing through the conductor. Thus, it is necessary to substantially adjust the sensitivity of the resistance change of the magnetoresistive element with respect to the current.

  Here, in order to expand the current detection range, there is a current sensor in which magnetoresistive elements having the same detectable magnetic field ranges are arranged at the center and the end in the width direction of the conductor through which the detection target current flows. It has been proposed (see, for example, Patent Document 1).

  In this current sensor, among the magnetic field components induced by the current flowing through the conductor, the magnetic field component parallel to the width direction is maximized at the center portion and decreases toward the end portion. Therefore, the resistance change with respect to the current can be substantially changed by arranging the magnetoresistive effect element at the central part and the end part, and a wider dynamic can be obtained by switching the magnetoresistive effect element to be read according to the current intensity. The range is secured.

International Publication No. 2012/029439

However, the prior art has the following problems.
That is, when a current flowing through a fine element such as a semiconductor switching element or a semiconductor memory is detected using the current sensor disclosed in Patent Document 1, a plurality of magnetoresistive effect elements may be disposed in the vicinity of the wiring of these fine elements. It becomes difficult. This is because the space that can be placed is very small, and if it is placed in multiple locations, it becomes difficult to distinguish between the magnetic field induced by the current to be detected, the magnetic field induced by the current flowing through the other wiring, and the noise magnetic field. This is because the measurement accuracy deteriorates.

  Here, it is important to detect the on-current of the switching element and the write current of the memory cell in order to monitor the control current and current consumption of the element. In addition, monitoring the leakage current of the switching element is useful for detecting element deterioration. Further, in the memory cell, the increase in leakage current has become conspicuous with miniaturization, and it is necessary to monitor the current consumption.

  However, since the strength differs greatly between the leakage current and the on-current, in the magnetoresistive effect element capable of detecting the leakage current, the resistance value against the current-induced magnetic field is saturated when the on-current flows, and the on-current strength is reduced. It cannot be detected. Further, as described above, when a plurality of magnetoresistive elements having different sensitivities are arranged around the switching element and the memory cell, it is difficult to arrange the magnetoresistive elements because the space is very small. Since the arrangement location is different, there is a problem that the distribution of the magnetic field applied to the magnetoresistive effect element is different.

  The present invention has been made to solve the above-described problems, and expands the dynamic range of the detectable current and improves the measurement accuracy without changing the area when viewed from the stacking direction. An object of the present invention is to obtain a current detecting device capable of performing the same and a magnetic field detecting device using the same.

A current detection device according to the present invention includes a magnetoresistive effect element assembly in which a plurality of magnetoresistive effect elements having different sensitivity to a magnetic field are stacked via a conductive spacer, and a magnetoresistive effect element assembly A resistance reading circuit that detects a resistance value of the current detection device, and a current detection device that detects the intensity of the current flowing through the conductor, wherein each of the plurality of magnetoresistive effect elements The second magnetic layer is laminated on the first magnetic layer via one of the insulating film and the metal film, and the magnetization direction follows the direction of the magnetic field induced by the current flowing through the conductor. possess a magnetic layer, a, of the second magnetic layer in each of the plurality of magnetoresistive elements, the at least one second magnetic layer, the interface opposite to the insulating film or a metal film, the magnetic anisotropy Invite By providing a cap layer to, those made different sensitivity of the resistance change to the magnetic field of a plurality of magnetoresistive elements to each other.

According to the current detection device of the present invention, a plurality of magnetoresistive effect elements having different sensitivity to resistance change with respect to a magnetic field are provided with a magnetoresistive effect element assembly stacked via conductive spacers. Each of the resistance effect elements is laminated on the first magnetic layer via the first magnetic layer whose magnetization direction is fixed with respect to the magnetic field induced by the current flowing through the conductor, and one of the insulating film and the metal film. And a second magnetic layer whose magnetization direction follows the direction of the magnetic field induced by the current flowing through the first magnetic layer.
Therefore, the dynamic range of the detectable current can be expanded and the measurement accuracy can be improved without changing the area when viewed from the stacking direction.

It is a perspective view which shows the relationship between the TMR element aggregate | assembly and a conductor in the electric current detection apparatus which concerns on Embodiment 1, 3-6 of this invention. It is sectional drawing which shows the TMR element assembly which concerns on Embodiment 1 of this invention which cut | disconnected FIG. 1 by the II line. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the 1st TMR element which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the 2nd TMR element which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the TMR element assembly which concerns on Embodiment 1 of this invention. It is a perspective view which shows the schematic circuit structure of the electric current detection apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows the relationship between the TMR element aggregate | assembly and a conductor in the electric current detection apparatus which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the TMR element assembly which concerns on Embodiment 2 of this invention which cut | disconnected FIG. 7 by the II-II line. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the 1st TMR element which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the 2nd TMR element which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the 3rd TMR element which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the relationship between the magnetic field and resistance in the TMR element assembly which concerns on Embodiment 2 of this invention. It is a perspective view which shows schematic circuit structure of the electric current detection apparatus which concerns on Embodiment 2 of this invention. It is sectional drawing which shows simply the TMR element assembly which concerns on Embodiment 3 of this invention which cut | disconnected FIG. 1 by the II line | wire. FIG. 5 is a cross-sectional view schematically showing a TMR element assembly according to Embodiment 4 of the present invention, taken along the line I-I in FIG. 1. It is sectional drawing which shows simply the TMR element assembly which concerns on Embodiment 5 of this invention which cut | disconnected FIG. 1 by the II line | wire. It is sectional drawing which shows simply the TMR element assembly which concerns on Embodiment 6 of this invention which cut | disconnected FIG. 1 by the II line | wire. It is explanatory drawing which shows the magnetization direction of each free layer in the TMR element assembly which concerns on Embodiment 6 of this invention. It is a perspective view which shows the schematic circuit structure of the magnetic field detection apparatus concerning Embodiment 9 of this invention. It is a flowchart which shows the process of the magnetic field detection apparatus concerning Embodiment 9 of this invention.

  Hereinafter, preferred embodiments of a current detection device according to the present invention and a magnetic field detection device using the same will be described with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. explain. In the following embodiments, a TMR element will be described as an example of a magnetoresistive element, but the same effect can be obtained even when a spin valve GMR element is used. The present invention can also be applied to a superlattice GMR element or a granular TMR element having a structure that operates by applying a read current perpendicular to the stacking direction.

Embodiment 1 FIG.
1 is a perspective view showing the relationship between a TMR element assembly and a conductor in a current detection device according to Embodiment 1 of the present invention. In FIG. 1, the TMR element assembly 1 is provided between a lower electrode 100 and an upper electrode 200. A conductor 2 is disposed below the TMR element assembly 1, and a detection target current 3 flows through the conductor 2.

  The TMR element assembly 1 is configured by laminating a first TMR element 4 and a second TMR element 6 having different sensitivity to a magnetic field through a spacer 5. Here, each of the first TMR element 4 and the second TMR element 6 has a spin valve structure, and the first TMR element 4 has higher sensitivity than the second TMR element 6.

The resistance value of the TMR element when the magnetization direction of the first magnetic layer of the TMR element is parallel to the magnetic field direction of the second magnetic layer is R _min, and the resistance value when anti-parallel is R _max . . At this time, the MR ratio with respect to the magnetic field of the TMR element is defined as the following equation (1).

(R _max −R _min ) / R _min × 100 [%] (1)

In Embodiment 1 of the present invention, the magnetization direction of the first magnetic layer of the TMR element, that is, the fixed layer, is fixed in a direction perpendicular to the longitudinal direction of the TMR element. When a magnetic field is applied in this direction, the magnetic field strength when the magnetization direction of the second magnetic layer, that is, the free layer is parallel to the magnetization direction of the first magnetic layer, is a magnetic field that saturates the change in resistance to the magnetic field of the TMR element. As H _k . At this time, the sensitivity of the resistance change with respect to the magnetic field of the TMR element is defined as the following equation (2).

(R _max −R _min ) / R _min × 100 / 2H _k [% / Oe] (2)

  FIG. 2 is a cross-sectional view showing the TMR element assembly according to Embodiment 1 of the present invention, taken along line II in FIG. In FIG. 2, the first TMR element 4 includes a seed layer 41, an antiferromagnetic layer 42, a ferromagnetic layer 43, a spacer 44, a ferromagnetic layer 45 as a fixed layer, and a barrier layer 46 as an insulating film from the lower electrode 100 side. The ferromagnetic layer 47 which is a free layer is laminated.

  In addition, a conductive spacer 5 is laminated between the first TMR element 4 and the second TMR element 6, and the uppermost part of the first TMR element 4 and the lowermost part of the second TMR element 6 are electrically connected. It is connected.

  The second TMR element 6 includes, from the lower electrode 100 side, a seed layer 61, an antiferromagnetic layer 62, a ferromagnetic layer 63, a spacer 64, a ferromagnetic layer 65 that is a fixed layer, a barrier layer 66 that is an insulating film, and a free layer. A ferromagnetic layer 67 as a layer is laminated.

  The first TMR element 4 and the second TMR element 6 are successively formed and then processed by etching so as to be rectangular or elliptical when viewed from the stacking direction. Moreover, it arrange | positions so that the longitudinal direction may follow the direction where the conductor 2 is extended.

  The ferromagnetic layer 45 and the ferromagnetic layer 65 in which the magnetization directions of the first TMR element 4 and the second TMR element 6 are fixed are fixed in the same direction, and the fixed direction is the direction in which the conductor 2 extends. It is a direction orthogonal to.

FIG. 3 is an explanatory diagram showing the relationship between the magnetic field and resistance in the first TMR element according to Embodiment 1 of the present invention, and FIG. 4 shows the magnetic field and resistance in the second TMR element according to Embodiment 1 of the present invention. It is explanatory drawing which shows the relationship. 3 and 4, the saturation magnetic field of the first TMR element 4 is denoted as H _k1, and the saturation magnetic field of the second TMR element 6 is denoted as H _k2 .

In the first TMR element 4 and the second TMR element 6, the magnetization directions of the ferromagnetic layer 47 and the ferromagnetic layer 67 that freely rotate in accordance with the external magnetic field direction are the magnetization directions of the ferromagnetic layer 45 and the ferromagnetic layer 65, respectively. It is assumed that the resistances of the first TMR element 4 and the second TMR element 6 when they are parallel to each other are equal to each other and R _min , and the resistances when they are anti-parallel are equal to each other and R _max However, this is a simple example for explaining the principle, and does not limit the resistance value to this relationship.

  At this time, in the series resistance of the first TMR element 4 and the second TMR element 6, the resistance change with respect to the magnetic field is a characteristic obtained by adding the resistance change with respect to the magnetic field of the first TMR element 4 and the second TMR element 6 shown in FIGS. It becomes.

Accordingly, in the magnetic field range smaller than the saturation magnetic field H _k1 of the first TMR element 4, the first TMR element 4 changes in resistance with respect to the magnetic field, so that the resistance change with respect to the magnetic field of the TMR element assembly 1 is caused by the second TMR element 6. Greatly increases the sensitivity.

On the other hand, in the magnetic field range that is larger than the saturation magnetic field H _k1 of the first TMR element 4 and smaller than the saturation magnetic field H _k2 of the second TMR element 6, the first TMR element 4 does not substantially change in resistance, but the second TMR element 6 Since the resistance changes with respect to the magnetic field, it is possible to detect a magnetic field in a wider range than the measurable magnetic field range of the first TMR element 4.

FIG. 5 is an explanatory diagram showing the relationship between the magnetic field and the resistance in the TMR element assembly according to Embodiment 1 of the present invention. As described above, the current detection device according to the first embodiment of the present invention uses the TMR element assembly 1 so that the current detection apparatus is accurate in a very small current range in which the magnetic field induced by the current is smaller than H _k1. On the other hand, even in a current range where the magnetic field induced by the current is larger than H _k1 , the output can be detected without being saturated.

  FIG. 6 is a perspective view showing a schematic circuit configuration of the current detection device according to Embodiment 1 of the present invention. FIG. 6 shows a wiring diagram of the resistance readout circuit of the current detection device. In FIG. 6, a DC current source 250 is connected between the lower electrode 100 connected to the lower part of the first TMR element 4 and the upper electrode 200 connected to the upper part of the second TMR element 6 to apply a constant current. To do.

  Further, a potential difference between the lower electrode 100 and the upper electrode 200 is measured using a voltmeter 251. At this time, the change of the voltage generated between the lower electrode 100 and the upper electrode 200 with respect to the magnetic field corresponds to the resistance change with respect to the magnetic field of the TMR element assembly 1.

  In addition, a current load 252 that supplies a current to be detected is connected in series to the conductor 2, and a magnetic field induced by a current flowing through the conductor 2 is applied to the TMR element assembly 1. Here, since the magnetic field applied to the TMR element assembly 1 is proportional to the intensity of the current flowing through the conductor 2, the intensity of the current flowing through the conductor 2 is detected by detecting the resistance value of the TMR element assembly 1. It becomes possible to do.

  At this time, for example, by recording in advance the resistance value of the TMR element assembly 1 when a known current is supplied, the resistance value of the TMR element assembly 1 when an unknown current flows is collected in advance. The current is easily detected by comparing the resistance change of the TMR element assembly 1 with respect to the current.

As described above, according to the first embodiment, a plurality of magnetoresistive effect elements having different sensitivity to resistance change with respect to a magnetic field are provided with a magnetoresistive effect element assembly stacked via conductive spacers. Each of the magnetoresistive effect elements is laminated on the first magnetic layer via a first magnetic layer whose magnetization direction is fixed with respect to a magnetic field induced by a current flowing through the conductor, and one of an insulating film and a metal film. And a second magnetic layer whose magnetization direction follows the direction of the magnetic field induced by the current flowing through the conductor.
Therefore, the dynamic range of the detectable current can be expanded and the measurement accuracy can be improved without changing the area when viewed from the stacking direction.

  That is, the current detection device according to the first embodiment of the present invention is a current detection device that includes a conductor through which a current to be detected flows and a magnetoresistive effect element arranged above or below the conductor. It has a structure in which multiple magnetoresistive effect elements with different sensitivity to resistance change with respect to the magnetic field are stacked, and the current intensity flowing through the conductor is detected by reading the resistance change of the magnetoresistive effect element due to the magnetic field induced by the current flowing through the conductor To do.

  Thereby, the range of current intensity that can be detected without lowering the current detection sensitivity of the current detection device, that is, the dynamic range can be expanded. In addition, since the area of the magnetoresistive effect element constituting the current detection device does not change when viewed from the stacking direction, the dynamic range of the current to be detected can be expanded even under conditions that were difficult with the conventional method. Can be easily realized.

  Conventionally, in order to expand the dynamic range of the detection current, it has been necessary to move the position of the magnetoresistive effect element away from the conductor through which the current flows or to arrange a plurality of elements having different sensitivities. Therefore, in the former, there is a decrease in the S / N ratio by moving the magnetoresistive effect element away from the current to be detected, and in the latter, the man-hour increases in the production of a magnetoresistive effect element having a plurality of sensitivities, resulting in an increase in cost. There was a problem of being connected.

  In addition, when detecting a current flowing through a device having a structure in which elements are integrated, such as a memory array or a power semiconductor element, a space in which magnetoresistive effect elements can be arranged is narrow, so a plurality of elements are arranged. That itself was difficult.

  On the other hand, according to the current detection device according to the first embodiment of the present invention, the area of the magnetoresistive effect element when viewed from the stacking direction, which is substantially the size of the current detection device, is not changed. The dynamic range of the detection current can be expanded.

Embodiment 2. FIG.
FIG. 7 is a perspective view showing the relationship between the TMR element assembly and the conductor in the current detection device according to Embodiment 2 of the present invention. In FIG. 7, the TMR element assembly 1a disposed on the top of the conductor 2 is composed of three TMR elements 7a to 7c having different sensitivity to resistance change with respect to a magnetic field. The number of TMR elements may be 4 or more.

  8 is a cross-sectional view showing a TMR element assembly according to Embodiment 2 of the present invention, taken along the line II-II in FIG. In FIG. 8, three TMR elements 7 a to 7 c are continuously formed with the spacer 5 interposed therebetween, and then processed by etching so as to be rectangular or elliptical when viewed from the stacking direction. Yes.

  Specifically, the TMR element assembly 1 a is configured by laminating a first TMR element 7 a, a second TMR element 7 b, and a third TMR element 7 c, which are different from each other in resistance change sensitivity with respect to a magnetic field, with a spacer 5 interposed therebetween. Here, the first TMR element 7a, the second TMR element 7b, and the third TMR element 7c have a spin valve structure, respectively, and are the first TMR element 7a, the second TMR element 7b, and the third TMR element 7c in descending order of sensitivity.

  FIG. 9 is an explanatory diagram showing the relationship between the magnetic field and resistance in the first TMR element according to Embodiment 2 of the present invention, and FIG. 10 shows the magnetic field and resistance in the second TMR element according to Embodiment 2 of the present invention. FIG. 11 is an explanatory diagram showing the relationship between the magnetic field and the resistance in the third TMR element according to Embodiment 2 of the present invention.

In 9-11, the saturation magnetic field of the 1TMR element 7a is denoted as _{H k1,} the saturation magnetic field of the 2TMR element 7b is denoted as _{H k2,} the saturation magnetic field of the 3TMR element 7c is denoted as _{H k3.} In the TMR elements 7a to 7c, the resistance value when the magnetization directions of the fixed layer and the free layer are parallel is R _min , and the resistance value when the magnetization directions are antiparallel is R _max , which are equal to each other. Have However, this is a convenient value determined for explanation, and does not limit the relationship of the resistance values of the respective TMR elements 7a to 7c constituting the TMR element assembly 1a.

  At this time, in the series resistance of the first TMR element 7a, the second TMR element 7b, and the third TMR element 7c, the resistance change with respect to the magnetic field is the first TMR element 7a, the second TMR element 7b, and the third TMR element 7c shown in FIGS. It is the characteristic which added the resistance change with respect to the magnetic field.

FIG. 12 is an explanatory diagram showing the relationship between the magnetic field and resistance in the TMR element assembly according to Embodiment 2 of the present invention. FIG. 12 shows that the sensitivity changes in the saturation magnetic fields H _k1 , H _k2 , and H _k3 of the respective TMR elements 7 a to 7 c. That is, each current intensity can be detected with high accuracy by matching the ranges having different sensitivities with the distribution of the range that the detection target current can take.

  For example, in a semiconductor switching element, there are a plurality of modes in the intensity of current flowing through the element. Here, assuming that this mode has three stages of leakage current, on-current, and eddy current, the dynamic range of the assumed current is greatly different between the modes. At this time, it is possible to realize a current detection device in which the sensitivity is automatically adjusted according to the current intensity by stacking TMR elements that can cover the dynamic range of each mode and reading them as series resistance. It is.

  FIG. 13 is a perspective view showing a schematic circuit configuration of the current detection device according to Embodiment 2 of the present invention. FIG. 13 shows a wiring diagram of the resistance readout circuit of the current detection device. Also in FIG. 13, by measuring the potential difference between the lower electrode 100 and the upper electrode 200 in the same manner as in the first embodiment described above, it is possible to detect a change in resistance with respect to the current of the TMR element assembly 1a.

  For this reason, since it is possible to read out with the same circuit as in the case of one TMR element without increasing the readout circuit necessary for expanding the dynamic range or configuring a TMR element having a plurality of sensitivities, Simplification can be realized.

  As described above, according to the second embodiment, it is possible to give the current detection device three or more levels of sensitivity without increasing the area when the TMR element is viewed from the stacking direction. Therefore, when there are a plurality of deviations in the intensity of the current flowing through the conductor, it is possible to realize a current detection device with high sensitivity in each current intensity range.

Embodiment 3 FIG.
FIG. 14 is a simplified cross-sectional view of the TMR element assembly according to Embodiment 3 of the present invention, taken along line II in FIG. In FIG. 14, arrows indicate the magnetization direction 143 a of the first magnetic layer in which the magnetization direction of the first TMR element 4 is fixed, the magnetization direction 143 b of the second magnetic layer whose magnetization direction rotates, and the first magnetism of the second TMR element 6. The magnetization direction 143c of the layer and the magnetization direction 143d of the second magnetic layer are shown.

  In the third embodiment of the present invention, a method for adjusting the sensitivity of the TMR element will be described. In general, the sensitivity of the resistance change to the magnetic field of the TMR element decreases as the free layer thickness is reduced. In addition, when it only describes with a sensitivity, the sensitivity of the resistance change with respect to a magnetic field shall be shown.

  This is because in the free layer of the TMR element, the magnetization state changes in the vicinity of the interface of the barrier layer and the cap layer laminated on the interface opposite to the barrier layer of the free layer. Specifically, in the vicinity of the interface, the magnitude of magnetization of the free layer and the magnetic anisotropy that is the direction in which the magnetization is easy to change change.

  In addition, these are caused by magnetic anisotropy induced by the crystal structure of the material in contact with the interface and alteration of magnetic properties due to mixing with the laminated film material in contact with the interface. Here, the change in magnetic anisotropy decreases the MR ratio by reducing the free layer magnetization that is parallel to the fixed layer magnetization, and lowers the sensitivity. Also, the alteration of the magnetic characteristics decreases the sensitivity by decreasing the amount of magnetization per unit volume of the free layer and consequently reducing the MR ratio. Therefore, by reducing the thickness of the free layer, it is possible to increase the proportion affected by the interface and decrease the sensitivity.

  At this time, the film thicknesses of the free layers of the first TMR element 4 and the second TMR element 6 are relatively changed, and the film thickness 141 of the free layer of the first TMR element 4 is changed from the film thickness 142 of the free layer of the second TMR element 6. Can be made relatively high in sensitivity, and the second TMR element 6 can be made relatively low in sensitivity.

  As described above, according to the third embodiment, it is not necessary to use an additional material in order to adjust the sensitivity of the TMR element, and the sensitivity can be increased only by changing the film thickness of the same material. It is possible to adjust.

  In order to adjust the sensitivity, not using an additional material has an advantage that management of film forming conditions excluding the film forming time becomes unnecessary. Moreover, since it can produce by changing a film thickness, there exists an advantage that the additional process for adjusting a sensitivity and an additional expense do not generate | occur | produce.

Embodiment 4 FIG.
FIG. 15 is a simplified cross-sectional view of the TMR element assembly according to the fourth embodiment of the present invention, taken along the line II in FIG. In FIG. 15, the thicknesses of the free layers of the first TMR element 4 and the second TMR element 6 having different sensitivities are equal to each other, but the cap layer is formed on the interface opposite to the barrier layer of the second magnetic layer of the second TMR element 6. As 150, magnesium oxide MgO is laminated.

  Here, at the interface between MgO and the free layer, the magnetization direction of the free layer is oriented in the direction perpendicular to the stacking direction due to the magnetic anisotropy induced by the MgO crystal structure. Therefore, by stacking MgO as the cap layer 150, the magnetization direction of the free layer is attracted in the direction perpendicular to the film surface, and as a result, the effect that the free layer magnetization is inclined with respect to the film surface is obtained.

  Accordingly, the magnetization parallel to the magnetization direction of the fixed layer can be reduced, and the MR of the in-film component from the external magnetic field is reduced, so that the MR is reduced. The range can be expanded. In addition, by using MgO for the cap layer 150, it is possible to reduce the film thickness dependence of the free layer in the sensitivity of the TMR element.

  As described above, according to the fourth embodiment, it is possible to reduce the influence of the free layer thickness dependency on the current detection sensitivity of the current detection device. As a result, it is possible to realize a current detection device in which variations in sensitivity of the manufactured current detection device are suppressed and current detection accuracy is improved.

Embodiment 5. FIG.
FIG. 16 is a simplified cross-sectional view of the TMR element assembly according to the fifth embodiment of the present invention, taken along the line II in FIG. In FIG. 16, in the fifth embodiment of the present invention, in order to realize two TMR elements having different sensitivities, a cap layer 160a made of MgO laminated on the free layer of the first TMR element 4 and a free layer of the second TMR element 6 The thicknesses of the cap layer 160b made of MgO laminated on each other are different.

  At this time, the sensitivity of the first TMR element 4 and the second TMR element 6 changes according to the film thickness of the MgO cap layer having a relatively different film thickness. This is because the change in sensitivity due to the stacking of the MgO cap layer depends on the thickness of the MgO cap layer, and the sensitivity is lowered by increasing the thickness of the MgO cap layer.

  Here, the strength of perpendicular magnetic anisotropy generated at the interface between MgO and the free layer depends on the film thickness of MgO, and the perpendicular magnetic anisotropy increases as the film thickness is increased. Therefore, the sensitivity of the TMR element can be changed by changing the thickness of the MgO cap layer.

  Therefore, in the TMR element in which the MgO cap layer is laminated on the free layer, the TMR element having a relatively small thickness of the MgO cap layer has lower magnetic anisotropy strength in the vertical direction, so that the sensitivity is increased and dynamic. The range becomes smaller.

  As described above, according to the fifth embodiment, although the film formation time is increased, the MgO cap layer is applied to both of the TMR elements constituting the current detection device. The film thickness dependency can be further reduced as compared with the configuration shown in the fourth embodiment, and the variation in accuracy of the current detection device can be suppressed.

  Further, in each of the second magnetic layers of the plurality of TMR elements, the magnetic property of the second magnetic layer is changed by changing the film type or film thickness to be laminated on the interface opposite to the insulating film. Adjust the sensitivity. As a result, the sensitivity of the TMR element can be adjusted using not only the film thickness of the second magnetic layer but also the interaction at the interface with the material laminated on the opposite side of the insulating film. It is possible to design a sensitivity with a higher degree of freedom than sensitivity adjustment depending on the film thickness.

Embodiment 6 FIG.
FIG. 17 is a simplified cross-sectional view of the TMR element assembly according to Embodiment 6 of the present invention, taken along the line II in FIG. In FIG. 17, in the sixth embodiment of the present invention, in the free layer of the second TMR element 6 among the TMR elements constituting the TMR element assembly 1, in order to reduce the sensitivity of the TMR element and expand the dynamic range, An easy axis of magnetization, which is a direction in which magnetization is spontaneously directed when no external magnetic field is present, is defined as a direction 181e perpendicular to the film surface.

  Specifically, in the free layer of the second TMR element 6, when the magnetization direction has an elevation angle with respect to the laminated film surface and there is no external magnetic field, the elevation angle is made larger than 45 degrees. The sensitivity of the resistance change with respect to the magnetic field of the first TMR element 4 and the second TMR element 6 is made different from each other.

  FIG. 18 is an explanatory diagram showing the magnetization direction of each free layer in the TMR element assembly according to Embodiment 6 of the present invention. FIG. 18 shows the magnetization directions of the free layer and the pinned layer that each of the first TMR element 4 and the second TMR element 6 has.

  In FIG. 18, the magnetization direction of the free layer 181a of the first TMR element 4 is in the direction 181e perpendicular to the film surface as described above, and with respect to the film surface against the magnetic field induced by the detection target current. Then, it rotates from a vertical direction to a direction 181d parallel to the film surface. In addition, the magnetization direction of the free layer 182a of the second TMR element 6 moves in a direction 182d that rotates in the plane of the film with respect to the magnetic field induced by the detection target current.

  Further, in order to make the easy axis of the free layer 181a of the second TMR element 6 perpendicular to the film surface, MgO is used for the barrier layer 181b, and the thickness of the free layer 181a is 0.8 nm or less. This is possible.

  Here, in order to saturate the resistance magnetic characteristics of the TMR element, a magnetic field having a magnitude in which the magnetization of the free layer is parallel to the magnetization of the fixed layer must be applied. The magnetic field required at this time mainly depends on the element shape if the material is the same. When no magnetic field is applied, the magnetization direction of the free layer spontaneously faces the longitudinal direction of the element. This is due to the shape magnetic anisotropy, and the energy due to the demagnetizing field is lower in the longitudinal direction than in the lateral direction of the element.

  However, at the interface between the MgO and the free layer, the energy is lower when the magnetization is oriented in the direction perpendicular to the interface due to the interface perpendicular magnetic anisotropy due to the crystal matching with the crystal structure of MgO. There is a feature.

  Therefore, at the interface, the magnetic field required to make the magnetization stable in the direction perpendicular to the film surface parallel to the fixed layer is larger than the shape magnetic anisotropy, and therefore rotates in the film surface. A larger saturation magnetic field can be obtained as compared with the magnetization.

  As described above, according to the sixth embodiment, the dynamic range can be further expanded, and a current detection characteristic that does not saturate even when a larger current is applied can be obtained.

  Further, in Embodiment 6 of the present invention, in the TMR element that is desired to have the highest sensitivity among the plurality of TMR elements, when the magnetic field does not exist, the magnetization direction of the second magnetic layer is the magnetization of the first magnetic layer. It is assumed that it is orthogonal to the direction. Therefore, when there is no magnetic field, the magnetization direction of the second magnetic layer is perpendicular to the laminated film surface.

  Whereas the TMR element in which the magnetization of the second magnetic layer is oriented in the in-plane direction is perpendicular to the laminated film, the TMR element has a large saturation magnetic field, and the method of the sixth embodiment of the present invention is applied. Thus, it is possible to effectively realize a TMR element having a large dynamic range.

  In addition, as a method for adjusting the sensitivity of the TMR element, the methods of the above-described third to sixth embodiments can be arbitrarily combined. As a result, even when a high-sensitivity TMR element and a TMR element with low sensitivity and a large dynamic range are combined, the current detection device according to the present invention can be obtained by simply forming each TMR element continuously. Can be realized.

Embodiment 7 FIG.
In the seventh embodiment of the present invention, the necessary conditions of the spacer 5 that connects the TMR elements constituting the TMR element assembly included in the current detection device will be described. Here, the second TMR element 6 shown in FIG. 2 will be described as an example.

  First, it is desirable to use Ta or Ru for the spacer 5. The antiferromagnetic layer 62 is preferably formed by stacking a seed layer 61 on the seed layer 61, and the seed layer 61 is preferably made of Ru. This is because the exchange coupling strength between the antiferromagnetic layer 62 and the ferromagnetic layer 63 laminated further thereon is increased.

  In the antiferromagnetic layer 62, the larger the crystal grain, the greater the unidirectionality of the magnetization direction of the antiferromagnetic layer 62. As a result, the strength of exchange coupling with the ferromagnetic layer 63 laminated thereon is increased. Increase. Further, the stronger the exchange coupling strength of the ferromagnetic layer 63 is, the smaller the fluctuation of the magnetization direction of the ferromagnetic layer 63 with respect to the magnetic field from the outside is, and it is possible to reduce the fluctuation of the MR ratio resulting therefrom. The size of the crystal grains of the antiferromagnetic layer 62 depends on the size of the crystal grains of the substrate material. Therefore, it is desirable to select a material having a large crystal grain size such as Ru for the seed layer 61.

  Here, for the sake of explanation, the second TMR element 6 is taken as an example, but the present invention is not limited to this, and in the current detection device according to the present invention, the second TMR element 6 is applied to the spacer 5 used when a plurality of TMR elements are stacked. Is possible.

Embodiment 8 FIG.
In the eighth embodiment of the present invention, a film forming method necessary for producing a TMR element constituting a current detecting device will be described.

  First, the magnetic material and nonmagnetic material to be formed are laminated by DC magnetron sputtering, RF magnetron sputtering, vacuum deposition, or the like. The barrier layer needs to be a non-conductor, but a metal oxide such as MgO or Al 2 O 3 can be used. At this time, using MgO makes it possible to obtain an MR ratio larger than that of Al2O3, thereby increasing sensitivity.

  In addition, in order to stack MgO and Al2O3, a sintered body of these metal oxides is used as a target, a film is stacked using RF sputtering, or metal Mg or Al is stacked and then oxygen is injected. Alternatively, oxygen plasma can be generated by injecting oxygen and further discharging to oxidize metal Mg or Al to cause a chemical change in the metal oxide.

  As described above, according to the eighth embodiment, since it is possible to reduce dust caused by the sintered body target generated in the chamber, the insulating film having a highly reproducible and stable insulating performance is laminated. It becomes possible to do.

Embodiment 9 FIG.
In a ninth embodiment of the present invention, a parallel type magnetic field detection device using the current detection devices of the first to eighth embodiments will be described.

  FIG. 19 is a perspective view showing a schematic circuit configuration of a magnetic field detection apparatus according to Embodiment 9 of the present invention. FIG. 19 shows the configuration of the magnetic field detection device configured using the current detection devices of Embodiments 1 to 8 described above, and the connection of additional circuits.

  In FIG. 19, here, the magnetic field H210 to be detected must be applied in parallel with the short direction of the TMR element, or the current detection device is arranged so that the magnetic field to be detected and the conductor 2 are orthogonal to each other. Must.

  A DC constant current source 190 c is connected between the lower electrode 100 and the upper electrode 200 of the TMR element assembly 1, and a voltage generated between the lower electrode 100 and the upper electrode 200 is measured and controlled by the measurement / control device 214. Measure with At this time, a value obtained by dividing the obtained voltage V1 by the constant current I1 applied from the DC constant current source is obtained as the resistance of the TMR element assembly 1 here.

  First, the resistance R0 of the TMR element assembly 1 is measured without applying a magnetic field. Next, a magnetic field to be detected is applied, and the resistance of the TMR element assembly 1 is measured again. A difference between the resistance R1 and the resistance R0 of the TMR element assembly 1 obtained at this time, that is, R1-R0 is set as ΔR.

  Subsequently, a direct current 212 is applied to the conductor 2. The magnetic field 211 induced by this current is combined with the detection target magnetic field 210 and is strengthened when the directions are the same, and is weakened and canceled when the directions are opposite. Here, with the constant current I applied, the resistance of the TMR element assembly 1 is measured, and the difference between the resistance R2 and the resistance R0 at that time, that is, R2-R0 is ΔR ′.

  At this time, if ΔR ′> ΔR, the current is decreased or the reverse current is increased, and if ΔR ′ <ΔR, the current is increased or the reverse current is decreased. .

  Thereafter, the same operation is repeated for the magnetic field intensity at that time, and the external magnetic field can be obtained by measuring the current when ΔR ′ is minimized. At this time, since the magnetic field induced by the current just cancels the detection target magnetic field, the current intensity at this time is proportional to the detection target magnetic field. Therefore, the external magnetic field strength can be easily obtained by multiplying by a constant.

  Next, the processing of the magnetic field detection device according to the ninth embodiment of the present invention will be described with reference to the flowchart of FIG. Each process shown in this flowchart is executed by the measurement / control device 214 shown in FIG.

  First, the resistance R0 of the TMR element assembly 1 is measured without applying the external magnetic field H210, and then the resistance R1 of the TMR element assembly 1 is measured with the external magnetic field H210 applied. An absolute value ΔR of a difference from R1 is obtained (step S1).

Subsequently, for example, the current in the A → B direction of the conductor 2 in FIG. 19 is increased or the current in the B → A direction is decreased (step S2).
Next, the resistance R2 of the TMR element assembly 1 is measured in a state where a direct current is supplied to the conductor 2, and the absolute value ΔR ′ of the difference between R2 and R0 is obtained (step S3).

  Subsequently, when ΔR> ΔR ′ (Yes in step S4), that is, when the resistance of the TMR element assembly 1 approaches R0, the above steps S1 to S4 are repeated to increase the direct current in the same direction, When ΔR ′ <α (α: predetermined value) is satisfied (Yes in step S5), the supply current I212 is converted into a magnetic field and output (step S11), and the process of FIG. 20 is terminated.

  On the other hand, if ΔR <ΔR ′ in step S4 (No in step S4), that is, if the resistance of the TMR element assembly 1 moves away from R0, the absolute value ΔR of the difference between R0 and R1 is obtained (step S6). ).

Subsequently, for example, the current in the B → A direction of the conductor 2 in FIG. 19 is increased, or the current in the A → B direction is decreased (step S7).
Next, the resistance R2 of the TMR element assembly 1 is measured in a state where a direct current is supplied to the conductor 2, and the absolute value ΔR ′ of the difference between R2 and R0 is obtained (step S8).

  Subsequently, when ΔR> ΔR ′ (Yes in step S9), that is, when the resistance of the TMR element assembly 1 approaches R0, the above steps S6 to S9 are repeated to increase the direct current in the same direction, When ΔR ′ <α is satisfied (Yes in step S10), the supply current I212 is converted into a magnetic field and output (step S11), and the process of FIG.

  On the other hand, if ΔR <ΔR ′ in step S9 (No in step S9), that is, if the resistance of the TMR element assembly 1 moves away from R0, the process returns to step S1 and the operation is repeated.

  In the flowchart of FIG. 20, the current I212 supplied to the conductor 2 first flows in the direction from the end A to the end B of the conductor 2, but this order may be reversed.

  As described above, according to the ninth embodiment, the range of the detectable magnetic field of the magnetic field detection device depends on the dynamic range of the resistance change with respect to the magnetic field of the TMR element assembly constituting the magnetic field detection device. It is possible to expand the detectable magnetic field range. In addition, since the resistance change of the TMR element assembly with respect to the magnetic field becomes large in the vicinity where the magnetic field becomes zero, the accuracy of the detection magnetic field can be improved.

  1, 1a Element assembly, 2 conductors, 3 current to be detected, 4th TMR element, 5 spacer, 6 2nd TMR element, 7a to 7c TMR element, 41 seed layer, 42 antiferromagnetic layer, 43 ferromagnetic layer, 44 Spacer, 45 Ferromagnetic layer, 46 Barrier layer, 47 Ferromagnetic layer, 61 Seed layer, 62 Antiferromagnetic layer, 63 Ferromagnetic layer, 64 Spacer, 65 Ferromagnetic layer, 66 Barrier layer, 67 Ferromagnetic layer, 100 Lower Electrode, 141 film thickness of second magnetic layer, 142 film thickness of second magnetic layer, 143a magnetization direction of first magnetic layer, 143b magnetization rotation direction of second magnetic layer, 143c magnetization direction of first magnetic layer, 143d first Magnetization direction of two magnetic layers, 150 cap layer, 160a cap layer, 160b cap layer, 181a second magnetic layer, 181b barrier layer, 181c first magnetic layer 181d Rotation direction of magnetization of second magnetic layer, 181e Magnetization direction of second magnetic layer, 181f Magnetization direction of first magnetic layer, 182a Second magnetic layer, 182b Barrier layer, 182c First magnetic layer, 182e First magnetic layer Magnetization direction of 182f, magnetization rotation direction of the second magnetic layer, 200 upper electrode, 190a control signal, 190b canceling current applying device (current source), 211 magnetic field induced by current, 210 detection target magnetic field, 212 detection target magnetic field Current applied in the direction in which the magnetic field is generated so as to cancel, 214 measurement / control device, 250 current source, 251 voltmeter, 252 current load.

Claims (4)

A magnetoresistive effect element assembly in which a plurality of magnetoresistive effect elements having different sensitivity to resistance change with respect to a magnetic field are stacked via a conductive spacer;
A resistance readout circuit for detecting a resistance value of the magnetoresistive effect element assembly,
A current detection device for detecting the intensity of current flowing through a conductor,
Each of the plurality of magnetoresistive elements is
A first magnetic layer having a fixed magnetization direction with respect to a magnetic field induced by a current flowing through the conductor;
A second magnetic layer stacked on the first magnetic layer via one of an insulating film and a metal film, the magnetization direction following the direction of the magnetic field induced by the current flowing through the conductor,
A cap layer for inducing magnetic anisotropy is provided at the interface opposite to the insulating film or the metal film for at least one second magnetic layer among the second magnetic layers in each of the plurality of magnetoresistive elements. This makes the sensitivity of the resistance change to the magnetic field of the plurality of magnetoresistive elements different from each other.
Current detecting device. A magnetoresistive effect element assembly in which a plurality of magnetoresistive effect elements having different sensitivity to resistance change with respect to a magnetic field are stacked via a conductive spacer;
A resistance readout circuit for detecting a resistance value of the magnetoresistive effect element assembly,
A current detection device for detecting the intensity of current flowing through a conductor,
Each of the plurality of magnetoresistive elements is
A first magnetic layer having a fixed magnetization direction with respect to a magnetic field induced by a current flowing through the conductor;
A second magnetic layer stacked on the first magnetic layer via one of an insulating film and a metal film, the magnetization direction following the direction of the magnetic field induced by the current flowing through the conductor,
For the second magnetic layer in each of the plurality of magnetoresistive elements, the cap layers for inducing magnetic anisotropy are provided at different thicknesses at the interface opposite to the insulating film or the metal film, thereby Make the sensitivity of resistance change to the magnetic field of different magnetoresistive elements different from each other
Current detecting device. When at least one second magnetic layer among the second magnetic layers in each of the plurality of magnetoresistive elements has an elevation angle with respect to the film surface in which the magnetization directions are stacked, and there is no external magnetic field , the to be greater than 45 degrees elevation, current detecting apparatus according to claim 1 or claim 2 made different sensitivity of the resistance change each other with respect to the magnetic field of said plurality of magnetoresistive elements. A magnetic field detection device using the current detection device according to any one of claims 1 to 3 ,
A magnetic field detection device which is disposed at a position where an external magnetic field is canceled by a magnetic field induced by a current flowing through the conductor, and detects the strength of the current by detecting the current strength.

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