JP6116694B2 - Magnetic field detector with magnetoresistive effect element and current detector - Google Patents

Description

  The present invention relates to a magnetoresistive effect element utilizing a tunnel magnetoresistive effect and a product to which the magnetoresistive effect element is applied, and in particular, a magnetic field detector provided with a magnetoresistive effect element having improved performance and ease of manufacture, And a current detector.

  In recent years, as a magnetoresistive effect element, a memory to which a TMR element having a tunneling magnetoresistance (TMR) effect capable of obtaining a larger resistance change rate than a conventional giant magnetoresistance (GMR) effect is applied, Applications of TMR elements to magnetic heads and the like are underway.

  In the TMR element, a three-layer film structure comprising a ferromagnetic layer / insulating layer / ferromagnetic layer is used as the simplest structure. Then, by injecting electrons with an external magnetic field or spin polarized, the spins of the two ferromagnetic layers are set parallel or antiparallel to each other, thereby increasing the tunnel current flowing through the insulating layer in the direction perpendicular to the film surface. The phenomenon that changes is used. By utilizing such a phenomenon, the TMR element can detect the relative magnetization direction of the two ferromagnetic layers by detecting the magnitude of the tunnel current.

  In recent years, in a TMR element, an MgO (magnesium oxide) film is used as a tunnel insulating layer, and a Co—Fe—B (cobalt-iron-boron) alloy film is used as a ferromagnetic layer. It is known that a resistance change rate can be obtained. Furthermore, it is known that the magnetization of the Co—Fe—B film exhibits perpendicular magnetic anisotropy at the interface between the MgO film and the Co—Fe—B alloy film, and its application to memory is being promoted mainly. .

  In a GMR element or a TMR element, one ferromagnetic layer is exchange-coupled with an antiferromagnetic layer, and the magnetization of the ferromagnetic layer is fixed to be a fixed layer, and the magnetization of the other ferromagnetic layer is changed to an external magnetic field or spin. A so-called spin-valve structure is used, which is a free layer that can be easily inverted by polarized electrons.

  A TMR element having a spin valve structure can be used as a highly sensitive magnetic field detector. When a magnetic field is applied to the spin-valve magnetoresistive element from the outside, the magnetization of the pinned layer is ideally completely fixed, so that only the magnetization of the free layer rotates according to the externally applied magnetic field. . As a result, the relative angle of magnetization of the two ferromagnetic layers changes, and the element resistance changes due to the magnetoresistive effect.

  This change in resistance value is detected as a change in voltage with a constant current flowing through the element, for example. This voltage change is read as a signal that changes in accordance with the applied magnetic field. A TMR element having a spin valve structure has a higher rate of resistance change than other magnetoresistive elements and a small magnetic interaction between the free layer and the pinned layer, so that highly sensitive magnetic field detection is possible.

  In order to detect the magnitude of the external magnetic field with high accuracy by a magnetic field detector using a spin-valve type magnetoresistive effect element, the magnetization directions of the fixed layer and the free layer are determined in the absence of a magnetic field (when the external applied magnetic field is zero) A configuration is known in which orthogonalization is performed in the film surface direction (see, for example, Patent Document 1). The technique of Patent Document 1 detects the magnitude of a magnetic field applied in the magnetization direction of the pinned layer based on the magnetization direction of the free layer. Thus, a technique for suppressing the occurrence of hysteresis in the ferromagnetic material constituting the free layer is shown.

  The operation region is below a magnetic field that saturates in the axial direction in which the magnetization of the free layer is difficult, that is, a so-called anisotropic magnetic field. Here, a technique for orthogonalizing the magnetizations of the pinned layer and the free layer in the absence of a magnetic field is also disclosed. For example, in order to control the magnetic anisotropy of the free layer, a hard layer adjacent to the free layer is additionally provided. A technique for providing a ferromagnetic layer is shown.

  Patent Document 1 discloses a technique using a spin valve type GMR element in which current flows in the in-plane direction of the film. Since the GMR element generally has a low resistance, in order to obtain a large output signal, it is necessary to increase a supply current amount, and there is a problem that power consumption increases accordingly. On the other hand, the TMR element can realize a high resistance and a high resistance change rate, and can realize a magnetic field detector with high output and low power consumption.

  Note that the magnetoresistive effect element having the configuration shown in Patent Document 1 is suitable for detecting a magnetic field along the magnetization direction of the pinned layer. On the other hand, it is difficult to detect a magnetic field in a direction different from the magnetization direction of the pinned layer, for example, when a magnetic field in the direction of 90 ° is applied to the magnetization direction of the pinned layer. For this reason, it is particularly suitable for measurement in which the magnetic field direction is fixed, such as a current detector in which the positions of the wiring and the magnetoresistive effect element are fixed.

JP-A-4-358310

However, the prior art has the following problems.
In the structure of the conventional magnetoresistive effect element, the magnetic anisotropy of the free layer occurs, and there is a case where a domain wall exists in the free layer or a stable state occurs during magnetization rotation. As a result, there is a problem that hysteresis occurs.

  As a result, an error occurs in the output signal as the magnetic field detector depending on the history of the free layer magnetization, and as a result, a magnetic field detection error occurs. Possible countermeasures include the installation of a magnetically hard ferromagnetic layer for imparting magnetic anisotropy of the free layer, or a magnetic field application mechanism. However, in the case of these measures, the manufacturing process becomes complicated, and there is a problem that integration is difficult when, for example, a plurality of elements are mounted on an integrated circuit.

  Further, as one of the measures for imparting the magnetic anisotropy of the free layer, a Co—Fe—B at the interface between the MgO film that is the tunnel insulating film of the TMR element and the Co—Fe—B alloy film that is the free layer. It is conceivable to use the characteristic that the magnetization of the film is oriented in the direction perpendicular to the film surface. However, when this means is used, the contribution of perpendicular magnetic anisotropy at the interface changes depending on the thickness of the free layer. Therefore, there is a problem that the characteristics are sensitive to the thickness of the free layer.

  The present invention has been made in view of the above-described problems, and includes a magnetoresistive effect element that achieves both high accuracy and high sensitivity characteristics that suppress hysteresis and realization of manufacturing process and ease of integration. An object of the present invention is to obtain a magnetic field detector and a current detector.

A magnetic field detector including a magnetoresistive effect element according to the present invention is a magnetic field detector including a magnetoresistive effect element that detects a magnetic field by the resistance of the magnetoresistive effect element. A cap layer containing an oxide containing oxide, a free layer made of a ferromagnetic layer mainly composed of a Co—Fe—B alloy film in contact with the cap layer, a tunnel insulating layer made of an oxide containing Mg, and tunnel insulation The free layer is formed in a laminated structure including a pinned layer made of a ferromagnetic layer magnetized in the film surface direction opposite to the free layer via the layer. The magnetization of the free layer and the pinned layer is perpendicular to the film surface, and the projected components on the film surface are orthogonal to each other, and the magnetoresistive element resistance follows the magnetization direction of the pinned layer. For detecting magnetic fields A.

  Further, the current detector according to the present invention includes a magnetic field detector including the magnetoresistive effect element of the present invention, and a magnetic field measured by a magnetic field detector including the magnetoresistive effect element with respect to an object to be measured with a magnetic field. And an arithmetic unit for measuring the current flowing through the measured object from the relational expression between the distance between the magnetoresistive element and the measured object and the current flowing through the measured object.

  According to the present invention, hysteresis is suppressed by employing a magnetoresistive effect element including a free layer composed of a ferromagnetic layer formed so as to have a perpendicular magnetization component at the upper and lower interfaces together with an in-plane magnetization component. Thus, it is possible to obtain a magnetic field detector and a current detector provided with a magnetoresistive effect element that achieve both high accuracy and high sensitivity characteristics and easy manufacturing process and integration.

It is a schematic block diagram of the magnetic field detector in Embodiment 1 of this invention. It is a figure for demonstrating the magnetization direction of the magnetoresistive effect element used with the magnetic field detector in Embodiment 1 of this invention. It is the schematic which shows the cross-sectional structure along the transversal direction of the magnetoresistive effect element used with the magnetic field detector in Embodiment 1 of this invention. It is a figure for demonstrating the magnetization direction of the free layer of the magnetoresistive effect element in Embodiment 1 of this invention. It is an equivalent circuit schematic of the magnetic field detector in Embodiment 1 of this invention. It is the schematic which shows the laminated structure in the material of the magnetoresistive effect element in Embodiment 1 of this invention. It is a figure for demonstrating the magnetization direction of the magnetoresistive effect element in Embodiment 1 of this invention. It is a figure which shows the laminated structure of the conventional magnetoresistive effect element. It is a figure for demonstrating the magnetization direction of the free layer of the conventional magnetoresistive effect element. It is the comparison figure which showed the thickness dependence of the free layer in the width | variety of each hysteresis, and resistance change rate of the magnetoresistive effect element in Embodiment 1 of this invention, and the conventional magnetoresistive effect element. It is the schematic which shows the laminated structure modification 1 of the magnetoresistive effect element in Embodiment 2 of this invention. It is the schematic which shows the laminated structure modification 2 of the magnetoresistive effect element in Embodiment 2 of this invention. It is the schematic which shows the laminated structure modification 3 of the magnetoresistive effect element in Embodiment 2 of this invention. It is the schematic which shows the laminated structure modification 4 of the magnetoresistive effect element in Embodiment 2 of this invention. It is the schematic which shows the connection modification 1 of the magnetoresistive effect element in Embodiment 3 of this invention. It is the schematic which shows the connection modification 2 of the magnetoresistive effect element in Embodiment 3 of this invention. It is the schematic which shows the connection modification 3 of the magnetoresistive effect element in Embodiment 3 of this invention. It is the schematic which shows the connection modification 4 of the magnetoresistive effect element in Embodiment 3 of this invention. It is the schematic which shows the connection modification 5 of the magnetoresistive effect element in Embodiment 4 of this invention. It is a figure for demonstrating the shape dependence of the magnetic characteristic of the magnetoresistive effect element in Embodiment 5 of this invention. It is the schematic which shows the current detector in Embodiment 6 of this invention. It is the schematic which shows the connection of the magnetoresistive effect element of the current detector in Embodiment 6 of this invention. It is a schematic sectional drawing which shows a part of semiconductor integrated circuit which has a current detector in Embodiment 7 of this invention. It is a schematic sectional drawing which shows a part of another semiconductor integrated circuit which has a current detector in Embodiment 7 of this invention. It is a schematic sectional drawing which shows a part of semiconductor integrated circuit which has the current detector in Embodiment 8 of this invention.

  Hereinafter, preferred embodiments of a magnetic field detector including a magnetoresistive effect element according to the present invention and a current detector will be described with reference to the drawings. In each embodiment, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram of a magnetic field detector according to Embodiment 1 of the present invention. Moreover, FIG. 2 is a figure for demonstrating the magnetization direction of the magnetoresistive effect element used with the magnetic field detector in Embodiment 1 of this invention. Specifically, FIG. 2A is a top view of the magnetoresistive effect element 1 shown in FIG. 1, and FIGS. 2B and 2C are double arrows (b) shown in FIG. It is sectional drawing seen from the direction of (c). Furthermore, FIG. 3 is a schematic diagram showing a cross-sectional structure along the short direction of the magnetoresistive effect element used in the magnetic field detector according to Embodiment 1 of the present invention.

  Initially, with reference to FIGS. 1-3, the structure of the magnetic field detector in Embodiment 1 of this invention is demonstrated. As shown in FIG. 1, the magnetic field detector 100 according to the first embodiment includes a magnetoresistive effect element 1 that uses the TMR effect and a direct current that supplies a constant current of a predetermined magnitude to the magnetoresistive effect element 1. The power source 2 includes a voltmeter 3 that detects a voltage between the lower electrode layer 6 and the upper electrode layer 7 of the magnetoresistive effect element 1 (see FIG. 3).

  The magnetoresistive effect element 1 has an upper electrode layer 7 connected to the DC power supply 2 and the voltmeter 3 by wiring 4, and a lower electrode layer 6 connected to the DC power supply 2 and the ground node of the voltmeter 3 by wiring 5. ing. In FIG. 2, the mechanism for applying an external magnetic field (see magnetic field Hex in FIG. 3) is not shown, but for example, the magnetic field Hex is applied by passing a current through the wiring. Can do.

  The magnetic field detector 100 detects a magnetic field by causing a current to flow in the stacking direction of the ferromagnetic layer (free layer) 8, the tunnel insulating layer 9, and the pinned layer 10 as the free layer of the magnetoresistive effect element 1. It is configured.

  Although the detailed configuration of the magnetoresistive effect element 1 will be described later, the cap layer 12, the free layer 8, the tunnel insulating layer 9, the ferromagnetic layer 10a, the nonmagnetic layer 10c, the ferromagnetic layer 10b, and the antiferromagnetic layer. And a fixing layer 10 made of 10d. The cap layer 12 is in contact with the free layer 8. Further, the free layer 8 and the ferromagnetic layer 10a are opposed to each other through the tunnel insulating layer 9, and the ferromagnetic layer 10a and the ferromagnetic layer 10b are opposed to each other through the nonmagnetic layer 10c. Further, the ferromagnetic layer 10b is in contact with the antiferromagnetic layer 10d.

  The magnetoresistive effect element 1 is shown in a top view in FIG. 2 (a). The magnetoresistive effect element 1 is formed in a substantially rectangular planar shape and has a longitudinal direction and a lateral direction (a direction intersecting the longitudinal direction). In order to impart the magnetic anisotropy of the pinned layer 10 in the short direction of the magnetoresistive effect element 1, a magnetic field is applied in the short direction during the formation of the pinned layer 10 and during heat treatment. As a result, the ferromagnetic layers 10a and 10b of the pinned layer 10 have short-side magnetizations 101a and 101b in the film surface (layer surface) when the magnetic field Hex from the outside is zero and the magnetic field Hex is zero (FIG. 3). See).

  In the pinned layer 10, since the two ferromagnetic layers 10a and 10b are magnetically coupled via the nonmagnetic layer 10c, the magnetization directions 101a and 101b are opposite to each other (180 °). is there. This cancels each other's magnetizations, suppresses the influence on the free layer, and plays the role of stabilizing the magnetization fixation without being influenced by the external magnetic field Hex.

  As shown in FIG. 2, when the magnetization direction 81 of the free layer (ferromagnetic layer) 8 is viewed on the projection surface from the upper surface of the element due to the perpendicular direction of the film surface and the influence of the demagnetizing field due to the element shape, the element 1 Is magnetized in the longitudinal direction. However, the free layer 8 which is a ferromagnetic layer in the present invention has a component of magnetization in the vertical direction as well as magnetization in the in-plane direction of the film. That is, the magnetization direction 81 has an inclination from the film surface direction of the free layer 8 (see FIG. 2B).

  FIG. 4 is a diagram for explaining the magnetization direction of the free layer 8 of the magnetoresistive effect element 1 according to the first embodiment of the present invention. The double arrow of the magnetoresistive effect element 1 shown in FIG. It corresponds to a cross-sectional view seen from the direction (b). In FIG. 2, the case where the entire magnetization direction 81 is inclined has been described for the sake of simplicity. However, as shown in FIG. 4, actually, in the free layer (ferromagnetic layer) 8. The magnetization shows a local distribution and has a local magnetization gradient.

  In the distribution of magnetization in the vertical direction at the interface between the MgO film as the tunnel insulating layer 9 and the MgO film as the cap layer 12, the magnetization component in the in-plane direction is relatively relative to the portion where the influence of the interface is small. It is getting bigger.

  Returning to FIG. 2, in the state where no external magnetic field Hex is applied, the magnetization 81 and the magnetization 101a of the free layer (ferromagnetic layer) 8 and the ferromagnetic layer 10a facing each other across the tunnel insulating layer 9 are When viewed from the projection surface from one upper surface, they are orthogonal to each other.

  That the magnetization direction 81 of the free layer (ferromagnetic layer) 8 and the magnetization direction 101a of the ferromagnetic layer 10a are orthogonal to each other means that the relative angle of the magnetization direction is shifted from 90 ° within a range of ± 10 ° due to manufacturing error. Including the case. In FIG. 2, for ease of explanation, the magnetization 81 of the free layer (ferromagnetic layer) indicates the direction in the absence of a magnetic field.

  FIG. 5 is an equivalent circuit diagram of the magnetic field detector according to Embodiment 1 of the present invention. In FIG. 5, since the resistance value of the magnetoresistive effect element 1 is changed by an external magnetic field, the magnetoresistive effect element 1 is indicated by a symbol of a variable resistance element. A voltmeter 3 is connected in parallel with the magnetoresistive effect element 1, and a DC power supply 2 is connected in series with the magnetoresistive effect element 1. In FIG. 5, the DC power supply 2 is connected between the ground node and the magnetoresistive effect element 1 (high potential side thereof), but the DC power supply 2 is connected between the power supply node and the ground node. Any device that is connected and supplies a constant current to the magnetoresistive element 1 may be used.

  As shown in FIG. 3, the magnetoresistive effect element 1 according to the first embodiment includes a lower electrode layer 6, an upper electrode layer 7, a free layer (ferromagnetic layer) 8, a tunnel insulating layer 9, The fixing layer 10 is provided. A lower electrode layer 6 is formed on the substrate 11. Further, an antiferromagnetic film 10d is formed on the lower electrode layer 6, and a ferromagnetic layer 10b is formed at a position in contact with the antiferromagnetic film 10d.

  A nonmagnetic layer 10c is formed so as to be sandwiched between the ferromagnetic layer 10b and the ferromagnetic layer 10a, and a tunnel insulating layer 9 is formed so as to be sandwiched between the ferromagnetic layer 10a and the free layer (ferromagnetic layer) 8. Yes. FIG. 3 shows an example in which the magnetization 81 of the free layer (ferromagnetic layer) 8 is applied with a magnetic field in a direction along the magnetization 101 a of the ferromagnetic layer 10 a in the fixed layer 10.

  Next, with reference to FIG. 6, the specific laminated structure containing the material in the magnetoresistive effect element 1 is demonstrated. FIG. 6 is a schematic diagram showing a laminated structure related to the material of the magnetoresistive effect element according to Embodiment 1 of the present invention. The free layer (ferromagnetic layer) 8 is made of a Co—Fe—B (cobalt-iron-boron) alloy film. When the tunnel insulating layer 9 is an MgO film, the Co—Fe—B alloy film has a perpendicular magnetic anisotropy in the vicinity of the interface (negative when the anisotropy energy in the film surface is defined as positive). Show.

  The free layer 8 is not limited to a Co—Fe—B alloy film, and may be any ferromagnetic film containing Fe (iron) as a main component. An effect can be obtained.

  The thickness of the free layer 8 made of a Co—Fe—B alloy film is 1.1 nm. The thickness of the free layer 8 is not limited to this, and can be changed according to the magnetic field response of the element. The Co—Fe—B alloy film contains inevitable impurities.

The tunnel insulating layer 9 is made of an MgO (magnesium oxide) film. Note that the tunnel insulating layer 9 is not limited to this, as long as it contains Mg (magnesium) and oxygen, and may be MgAl ₂ O ₄ (spinel) or the like.

  The thickness of the tunnel insulating (film) layer 9 made of MgO film is 1.7 nm. The thickness of the tunnel insulating layer 9 is not limited to this and needs to be thicker than the cap layer 12 described later, but can be changed according to the resistance of the element and the magnetic field response. Further, the MgO film contains inevitable impurities.

  The ferromagnetic layer 10a is made of a Co—Fe—B alloy film. The ferromagnetic layer 10a is not limited to a Co—Fe—B alloy film, and includes at least one of Co (cobalt) such as Fe (iron) and Co (cobalt), Ni (nickel), and Fe (iron). Any ferromagnetic film may be used as long as it is a main component, and the same effect can be obtained even with a ferromagnetic film in which these films are laminated.

  The ferromagnetic layer 10a made of a Co—Fe—B alloy film has a thickness of 1.5 nm. The thickness of the ferromagnetic layer 10a is not limited to this, and can be changed according to the magnetic field response of the element. The Co—Fe—B alloy film contains inevitable impurities.

  The nonmagnetic layer 10c is made of a Ru (ruthenium) film. The nonmagnetic layer 10c is not limited to a Ru film, and may be any nonmagnetic film of a transition metal mainly composed of a platinum group such as Rt and Rb, and the same effect can be obtained.

  The thickness of the nonmagnetic layer 10c made of a Ru film is 0.8 nm. The thickness of the nonmagnetic layer 10c is not limited to this, and can be changed according to the magnetic field response of the element. The Ru film contains inevitable impurities.

  The ferromagnetic layer 10b is made of a Co—Fe alloy film. The ferromagnetic layer 10b is not limited to a Co—Fe alloy film, and the main component is at least one of Co (cobalt) such as Fe (iron) and Co (cobalt), Ni (nickel), and Fe (iron). The same effect can be obtained even with a ferromagnetic film in which these films are laminated.

  The thickness of the ferromagnetic layer 10b made of a Co—Fe alloy film is 1.5 nm. The thickness of the ferromagnetic layer 10b is not limited to this, and can be changed according to the resistance of the element and the magnetic field response. Further, the Co—Fe alloy film contains inevitable impurities.

  The antiferromagnetic layer 10d is made of an Ir—Mn (iridium-manganese) alloy film. The antiferromagnetic layer 10d is not limited to an Ir—Mn alloy film, and may be a Pt—Mn (platinum-manganese) alloy, an Fe—Mn (iron-manganese) alloy, a Ni—Mn (nickel-manganese) alloy, or the like. Any antiferromagnetic film may be used, and similar effects can be obtained.

  The antiferromagnetic layer 10d made of an Ir—Mn film has a thickness of 20 nm. The thickness of the antiferromagnetic layer 10d is not limited to this, and can be changed according to the resistance of the element and the magnetic field response. In addition, the Ir—Mn alloy film contains inevitable impurities.

  The lower electrode layer 6 and the upper electrode layer 7 are each made of a Ta (tantalum) film. Each of the lower electrode layer 6 and the upper electrode layer 7 may be another metal such as a Ru film, for example, but is not limited thereto. The lower electrode layer 6 is connected to the wiring 5 shown in FIG. 1, and the upper electrode layer 7 is connected to the wiring 4 shown in FIG. Cu (copper) is used for each of the wirings 4 and 5. The wirings 4 and 5 may be other metals such as Al (aluminum), for example, but are not limited thereto.

The cap layer 12 is disposed so as to have an interface with the free layer 8 and is made of an MgO (magnesium oxide) film. Note that the cap layer 12 is not limited to this, as long as it contains Mg (magnesium) and oxygen, and may be MgAl ₂ O ₄ (spinel) or the like.

  The cap layer 12 made of an MgO film has a thickness of 1.0 nm. Here, the resistance depending on the thickness of the MgO film generally changes by an order of magnitude at 0.3 nm.

  Here, since the thickness of the cap layer 12 made of the MgO film is 0.7 nm thinner than the MgO film of the tunnel insulating layer 9, the resistance caused by the MgO film of the cap layer 12 is caused by the tunnel insulating layer 9. It is two orders of magnitude smaller than the resistance, and the influence on the detected resistance change rate is sufficiently small. In addition, when the MgO film is thinner than 0.8 nm, the film may be discontinuous or sufficient crystallinity may not be obtained, but the MgO film of the cap layer 12 here is thicker than this and sufficient An effect is obtained. The thickness of the cap layer 12 is not limited to this, and it is necessary to be thinner than the tunnel insulating layer 9, but it can be changed according to the resistance of the element and the magnetic field response. Further, the MgO film contains inevitable impurities.

  As described above, in the magnetoresistive effect element 1 according to the first embodiment, the magnetization 81 of the ferromagnetic layer 8 serving as the free layer also has a component in the direction perpendicular to the film surface. Thereby, when the external magnetic field Hex is applied, magnetization rotation occurs in a state where the film also has a magnetization component in the vertical direction of the film. Here, the magnetization of the pinned layer 10 is in the in-plane direction of the film, but may include a vertical component.

  And according to arrangement | positioning of the magnetization 81 of the ferromagnetic layer 8 of the magnetoresistive effect element 1 of this Embodiment 1, as shown in FIG. 3, when the magnetic field Hex is applied from the outside, the magnetization 81 will rotate. As a result, the tunnel probability of electrons through the tunnel insulating layer 9 changes. As a result, the resistance changes depending on the external magnetic field Hex.

  Next, a method for manufacturing the magnetoresistive effect element and the magnetic field detector according to the first embodiment will be described. Each metal film (see FIG. 3) constituting the magnetoresistive element 1 is formed on the substrate 11 by DC (direct current) magnetron sputtering. The substrate 11 is made of Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), glass, or the like. The substrate 11 is not limited to this, and may be made of other materials, and an electronic circuit such as a wiring, a transistor, or a diode may be formed under the magnetoresistive effect element 1.

  A Ta film is formed as the lower electrode layer 6 using DC magnetron sputtering. After the Ta film as the lower electrode layer 6 is formed, an Ir—Mn alloy film having a thickness of 20 nm is formed as the antiferromagnetic layer 10d in the same apparatus without being exposed to the atmosphere. Subsequently, a Co—Fe alloy film having a film thickness of 1.5 nm as the ferromagnetic layer 10b, a Ru film having a film thickness of 0.8 nm as the nonmagnetic layer 10c, and a film thickness 1 as the ferromagnetic layer 10a without being exposed to the atmosphere. .5 nm Co—Fe—B alloy films are sequentially formed.

  Subsequently, after the MgO film having a thickness of 1.7 nm is formed as the tunnel insulating layer 9 using RF (radio frequency) magnetron sputtering without being exposed to the atmosphere, the free layer (ferromagnetic film) 8 is formed using DC magnetron sputtering. As a result, a Co—Fe—B alloy film having a thickness of 1.1 nm is formed. Thereafter, an MgO film of the cap layer 12 having a thickness of 1.0 nm is formed, and a Ta film is formed as the upper electrode layer 7.

  When these films are formed, a magnetic field of 100 Oe is applied in the film surface direction. Thereby, magnetic anisotropy is imparted to the Ir—Mn film, the Co—Fe film, and the Co—Fe—B film constituting the pinned layer 10. The films from the lower electrode layer 6 to the upper electrode layer 7 constituting the magnetoresistive effect element 1 are all formed in the same device. The MgO film that is the tunnel insulating layer 9 and the cap layer 12 may be formed by forming an Mg (magnesium) film by DC magnetron sputtering and then exposing it to an oxidizing atmosphere containing oxygen.

  Thereafter, heat treatment is performed. The purpose is to promote crystallization of the MgO film and the two Co-Fe-B films sandwiching it, and to impart magnetic anisotropy to the pinned layer 10 film. Here, 15 kOe which is a magnetic field for saturating the magnetization of the Co—Fe—B film and the Co—Fe film of the pinned layer 10 is applied. The direction in which the magnetic field is applied is the same as when the magnetoresistive effect element 1 is formed, and is the short direction of the magnetoresistive effect element 1 described later.

  The heat treatment temperature of the magnetoresistive effect element 1 is such that the Co—Fe—B film can be crystallized, and exchange coupling between the Ir—Mn film and the Co—Fe film of the pinned layer is substantially eliminated. ℃. This temperature was maintained for 1 hour.

  After the above heat treatment, the magnetizations of the ferromagnetic films 10a and 10b of the pinned layer 10 are oriented in the direction of 180 °. That is, the magnetization 101b of the Co—Fe alloy film and the magnetization 101a of the Co—Fe—B alloy film facing each other across the Ru film that is the nonmagnetic layer 10c are in opposite directions. Note that the magnetization 81 of the ferromagnetic layer (free layer) 8 includes the magnetic anisotropy in the vertical direction of the film depending on the crystal structure of the material. small.

  Thereafter, a desired pattern is formed by photolithography. After the film constituting the laminated magnetoresistive effect element 1 is formed, a desired pattern is formed by a photoresist. Then, the shape of the magnetoresistive effect element 1 is obtained by electrically and magnetically separating the magnetoresistive effect element 1 by reactive ion etching using a desired pattern formed of a photoresist as a mask.

  The magnetoresistive effect element 1 according to the first exemplary embodiment is rectangular as described above, and is formed in, for example, a rectangular shape having a short side × long side of 200 nm × 600 nm. The longitudinal direction of the magnetoresistive effect element 1 is a direction orthogonal to the magnetic field application direction when forming the pinned layer 10 in the laminated film.

  Due to the above pattern formation, the magnetization 81 of the Co—Fe—B film, which is the ferromagnetic layer 8 serving as the free layer, is affected by the demagnetizing field depending on the shape, and the magnetization 81 has a longitudinal component of the shape. It becomes. That is, the magnetization 81 of the ferromagnetic layer 8 has a vertical component of the film surface due to magnetic anisotropy depending on the crystal structure and a longitudinal component of the shape due to shape magnetic anisotropy.

  As shown in FIG. 1, the magnetoresistive effect element 1, the DC power source 2, and the voltmeter 3 are connected to each other by connecting the wirings 4 and 5 to the lower electrode layer 6 and the upper electrode layer 7, respectively. Connected. Although a detailed description of the connection method is omitted here, the magnetic field detector 100 using the magnetoresistive effect element 1 of the first embodiment is formed by performing such connection.

  Next, the magnetic field detection operation of the magnetic field detector according to the first embodiment will be described. As shown in FIG. 1 above, at the time of magnetic field detection, a constant current I is supplied from the DC power source 2 to the magnetoresistive effect element 1 through the wires 4 and 5. When the magnetic field Hex is applied to the magnetoresistive effect element 1 from the outside, the resistance value of the magnetoresistive effect element 1 changes according to the application direction of the magnetic field Hex from the outside.

  The lower electrode layer of the magnetoresistive effect element 1 with respect to the constant current I supplied from the direct current (current) power source 2 due to the change of the resistance value of the magnetoresistive effect element 1 according to the application direction of the magnetic field Hex from the outside. The voltage between 6 and the upper electrode layer 7 changes. This voltage change is detected by the voltmeter 3, and the external magnetic field Hex is detected.

  Although not shown here, since the external magnetic field Hex is detected by detecting the resistance change of the magnetoresistive effect element 1, a constant voltage is applied to the magnetoresistive effect element 1 by the direct current (voltage) power source 2. The current value at that time can also be detected by detecting with an ammeter.

  In addition, the magnetic detector has a calculation unit (not shown) that converts the voltage value detected by the voltmeter 3 or the current value detected by the ammeter into a magnetic field intensity based on a preset conversion equation. It may be provided.

  Next, the operation of the magnetoresistive effect element 1 when the magnetic field Hex is applied from the outside in the short direction (direction intersecting the longitudinal direction) of the magnetoresistive effect element 1 as shown in FIG. To do.

  FIG. 7 is a diagram for explaining the magnetization direction of the magnetoresistive effect element according to the first embodiment of the present invention. More specifically, FIG. 7A is a top view of the magnetoresistive effect element 1 of FIG. 1, and FIGS. 7B and 7C are double arrows (b) of FIG. It is sectional drawing seen from the direction of (c).

  When a magnetic field Hex is applied from the outside in the direction of the arrow in FIG. 7, the magnetization 81 of the ferromagnetic layer 8 in the absence of a magnetic field rotates in the direction of the magnetic field Hex. As a result, the relative angle between the pinned layer 10 and the magnetization 101a of the ferromagnetic layer 10a changes.

Here, with reference to FIG. 3, the detection method of the magnetic field direction using the TMR element will be described. When the directions of the magnetizations 81 and 101a of the two ferromagnetic layers 8 and 10a facing each other through the tunnel insulating layer 9 constituting the TMR element are θ1 and θ2, respectively, the element resistance R is approximately expressed by the following equation: It is represented by (1).
R = R0−ΔR / 2 · cos (θ2−θ1) (1)

  In the above formula (1), R0 is the center value of the element resistance, and ΔR is the resistance change amount of the element. The direction of magnetization of the ferromagnetic layer 8 of the free layer of the TMR element changes depending on the magnitude and direction of the external magnetic field. As a result, in the above formula (1), θ1-θ2 changes depending on the external magnetic field. Therefore, the magnetic field is detected by measuring the element resistance R.

  Again referring to FIG. 7, in magnetoresistive effect element 1 of the first exemplary embodiment, magnetization of ferromagnetic layer (free layer) 8 is performed by applying a magnetic field Hex from the outside in the direction of the arrow in FIG. 81 rotates in the direction of the external magnetic field Hex. That is, the magnetization 81 of the ferromagnetic layer 8 rotates in the direction of the magnetic field Hex and changes to the magnetization 82. Therefore, the relative magnetization directions of the ferromagnetic layer 8 and the ferromagnetic layer 10a change. Therefore, the tunnel probability of electrons through the tunnel insulating layer 9 shown in FIG. 3 also changes. Thereby, a change in the element resistance R depending on the external magnetic field Hex is obtained.

  If the external magnetic field Hex is further increased, the magnetization 82 is saturated in the direction in which the external magnetic field Hex is applied, so that the element resistance R is saturated at the maximum value. Using the relationship between the external magnetic field Hex and the element resistance R, a constant current I is passed in the stacking direction of the magnetoresistive effect element 1 (perpendicular to the film surface), and the voltmeter 3 shown in FIG. By measuring the voltage V applied to the resistance effect element 1, the strength of the magnetic field Hex from the outside is detected.

  Next, the effect of the magnetoresistive effect element in this Embodiment 1 is demonstrated. As described in [Problems to be Solved by the Invention], in the structure of a conventional spin-valve magnetoresistive element, a free layer that is magnetized in the film surface direction is used as the free layer. In particular, the magnetic anisotropy of the pinned layer and the free layer of the ferromagnetic film becomes substantially the same in the heat treatment after forming the laminated film on the magnetoresistive element. From this, due to insufficient magnetic anisotropy of the free layer, there may be a domain wall in the free layer or a stable state may occur during magnetization rotation, resulting in hysteresis. There was a problem to do. Even when the magnetic anisotropy of the ferromagnetic films of the pinned layer and the free layer is substantially in the same direction, it is possible to detect the magnetic field strength in the direction perpendicular to the pinned layer. However, detection of the magnetic field direction is not possible. This is because θ2−θ1 changes by ± 90 ° with reference to 0 ° (the element indicates the minimum resistance) or 180 ° (the element indicates the maximum resistance). In this case, the change is only ½ with respect to the maximum resistance change indicated by the magnetoresistive effect element.

  As a result, an error occurs in the output signal as the magnetic field detector depending on the history of the free layer magnetization, and as a result, a magnetic field detection error occurs. Possible countermeasures include the installation of a magnetically hard ferromagnetic layer for imparting magnetic anisotropy of the free layer, or a magnetic field application mechanism. However, in the case of these measures, the manufacturing process becomes complicated, and there is a problem that integration is difficult when, for example, a plurality of elements are mounted on an integrated circuit.

  On the other hand, in the magnetoresistive effect element 1 of the first embodiment, the magnetization of the free layer 8 has magnetic anisotropy in the vertical direction at the interface between the free layer 8 and the tunnel insulating layer 9. As a result, it is possible to suppress the occurrence of the hysteresis described above with a single element, and high accuracy can be achieved.

  Here, in order to explain the effect of the present invention, a comparison with a conventional laminated structure is performed. FIG. 8 is a diagram showing a laminated structure of a conventional magnetoresistive effect element. In the laminated structure of the conventional magnetoresistive element shown in FIG. 8, unlike the laminated structure of the magnetoresistive element 1 of the present invention shown in FIG. 6, there is no MgO film as the cap layer 12, and the upper electrode layer 7 is It also serves as the cap layer 12.

  FIG. 9 is a diagram for explaining the magnetization direction of the free layer 8 of the conventional magnetoresistive effect element, and shows the same cross section as FIG. 4 showing the magnetization direction in the first embodiment.

  In the conventional structure shown in FIG. 8, the interface that the free layer 8 has with the MgO film is only the interface with the tunnel insulating layer 9. For this reason, the perpendicular magnetic anisotropy at the interface of the free layer 8 is expressed only at one interface.

  FIG. 10 is a comparison diagram showing the dependence of the hysteresis width and resistance change rate of the magnetoresistive effect element 1 according to Embodiment 1 of the present invention and the conventional magnetoresistive effect element on the thickness of the free layer. is there. In FIG. 10, the hysteresis width is indicated by ▲, and the resistance change rate is indicated by ●.

  As shown in FIG. 10, the width of the hysteresis depending on the thickness of the free layer 8 is approximately 0 at 1.4 nm or less in the conventional element, whereas the element of the first embodiment Then, it can be seen that it becomes almost 0 at 1.2 nm or less. Further, the resistance change rate also changes with the same tendency as the hysteresis width.

  Here, in the conventional device, the width of the hysteresis increases rapidly at 1.4 nm or more. Therefore, in order to operate with the hysteresis suppressed, the free layer has a thickness of 1.4 nm or less. There is a need. However, the rate of change in resistance decreases sharply below 1.4 nm. Here, the sensitivity in magnetic field detection depends on the resistance change rate.

  For this reason, in the conventional element, the sensitivity of the magnetic field detection greatly depends on the thickness of the free layer. When the rate of change in resistance when the thickness of the free layer 8 is 1.4 nm is 100%, the rate of change in resistance is reduced by 10% due to a change in thickness of 0.015 nm (1% with respect to the thickness). . As a result, in the manufacturing process, when a distribution occurs in the thickness of the free layer within the substrate surface, or when a similar distribution occurs between the substrates, the sensitivity of the magnetoresistive effect element greatly changes. . Based on the case where the thickness of the free layer 8 is 1.4 nm, in order to keep the variation in resistance change within 10%, the range within 1% with respect to the thickness set by the free layer 8 It is necessary to control with. This control is substantially difficult.

  On the other hand, in the magnetoresistive effect element 1 according to the first embodiment, the hysteresis width is almost 0 at 1.2 nm or less, but the resistance change rate is abrupt and discontinuous even in a free layer thinner than that. There is no significant change. That is, it can be seen that the sensitivity is stable with respect to the thickness of the free layer as compared with the conventional device. In order to keep the variation of the resistance change rate within 10%, an error with respect to the thickness set by the free layer 8 is allowed up to 3%.

  This is because the free layer 8 of the magnetoresistive effect element 1 of the present invention has perpendicular magnetic anisotropy at the interface with the tunnel insulating layer 9 and is also perpendicular at the interface opposite to the tunnel insulating layer 9. This is because the perpendicular magnetic anisotropy component is more stable than the conventional structure shown in FIG. 8 due to the magnetic anisotropy.

  In FIG. 10, the reason why the thickness at which the hysteresis width becomes 0 is different from that in the conventional element is due to the difference in magnetization loss at the interface on the free layer 8.

  As described above, according to the first embodiment, the ferromagnetic layer serving as the free layer has a magnetization component in the vertical direction, and from the upper surface of the element due to the influence of the demagnetizing field depending on the shape of the free layer. When viewed on the projection plane, the magnet is magnetized in the longitudinal direction of the element. In the free layer magnetized in the normal film plane, in order to relax the magnetization at the end portion in the longitudinal direction, the local magnetization is arranged in the plane of the free layer, which causes a hysteresis.

  On the other hand, the free layer in the present invention is easily magnetized in the vertical direction, and can relax the magnetization at the end in the longitudinal direction. As a result, when an external magnetic field is applied, it is possible to suppress the occurrence of hysteresis especially when the magnetization rotates in a low magnetic field. That is, it is possible to alleviate the change in characteristics depending on the thickness of the free layer at that time, and to realize a magnetic field detector capable of high accuracy and high integration without increasing the number of additional structures. it can.

  In summary, the free layer in the present invention has a magnetization component in the vertical direction at the upper and lower interfaces along with the in-plane magnetization component, thereby realizing a magnetic field response with high sensitivity and suppressed hysteresis. Furthermore, in addition to the MgO film which is a tunnel insulating film, the cap layer is also an MgO film, so that it is possible to suppress rapid fluctuations in characteristics depending on the thickness of the free layer. As a result, the controllability of the magnetic field responsiveness is improved, and it is possible to suppress fluctuations in characteristics due to the manufacturing process.

  Furthermore, the thickness of the oxide containing Mg constituting the cap layer is thinner than the thickness of the tunnel insulating layer made of the oxide containing Mg. As a result, it is possible to suppress an increase in resistance and a decrease in the resistance change rate due to the addition of the MgO film (addition of series resistance to the element).

Embodiment 2. FIG.
In the second embodiment, a modified example of the laminated structure of the magnetoresistive effect element 1 will be described. FIGS. 11-14 is schematic which shows the laminated structure modification examples 1-4 of the magnetoresistive effect element in Embodiment 2 of this invention.

  The magnetoresistive effect element 1 shown in FIG. 11 corresponding to the laminated structure modification 1 has a laminated structure in which the free layer 8 includes two ferromagnetic layers 8a and 8b. Specifically, the ferromagnetic film 8a is a Co—Fe—B alloy film, and the ferromagnetic film 8b is an Fe—B alloy. The free layer 8 is not limited to two layers, and can be a ferromagnetic film having two or more layers having different compositions.

  Here, the Co—Fe—B alloy applied as the free layer 8 in the structure of FIG. 6 in the first embodiment is known as a material that can obtain a large resistance change rate in the TMR element. From this, also in the magnetoresistive effect element of FIG. 11, the resistance change rate similar to FIG. 6 is obtained.

  The structure shown in FIG. 11 further includes an Fe—B film on the Co—Fe—B alloy film. It is considered that the perpendicular magnetic anisotropy at the interface between the Co—Fe—B alloy film and the MgO film is obtained by the interaction of Fe (iron) and O (oxygen). In the Fe—B film, the Fe content is higher than that in the Co—Fe—B alloy film, and the vertical axis is stronger at the interface between the Fe—B film 8 b and the MgO film 12 of the cap layer than the Co—Fe—B film. Anisotropy is obtained.

  Accordingly, the resistance change rate equivalent to the structure described in FIG. 6 and more stable perpendicular magnetic anisotropy can be obtained by the structure of FIG. Although the Fe—B film is shown here as the ferromagnetic film 8b, the same effect can be obtained if the Fe content is larger than the Co—Fe—B alloy film of the ferromagnetic film 8a. It is not limited to the B film.

  Thus, in the multilayer structure modification 1, the free layer is composed of two or more ferromagnetic films having different compositions, and the Fe content of the ferromagnetic film in contact with the tunnel insulating layer is the same as that of the ferromagnetic film in contact with the cap layer. The structure is smaller than the Fe content. As a result, a material having a large Fe composition ratio and a large perpendicular magnetic anisotropy can be separated from the tunnel insulating layer, and a material having a large resistance change rate can be provided on the tunnel insulating layer side, which impairs the resistance change rate. Therefore, it becomes possible to adjust the magnetic field response.

  Next, in addition to the structure shown in FIG. 6, the magnetoresistive effect element 1 shown in FIG. 12 corresponding to the laminated structure modification 2 has a ferromagnetic film 13 made of a Co—Fe—B alloy film on the cap layer 12. Is further provided. The free layer 8 and the ferromagnetic film 13 are opposed to each other with the MgO film of the cap layer 12 interposed therebetween. In this structure, perpendicular magnetic anisotropy is also obtained at the interface between the ferromagnetic film 13 and the cap layer 12.

  Since the ferromagnetic film 13 is magnetostatically coupled through the free layer 8 and the cap layer 12, it acts to stabilize the perpendicular magnetic anisotropy at the interface between the free layer 8 and the cap layer 12. That is, by having the ferromagnetic film 13, the perpendicular magnetic anisotropy component in the free layer 8 can be stabilized.

  Next, FIG. 13 corresponding to the multilayer structure modification 3 shows the magnetoresistive element 1 in which the ferromagnetic film 13 shown in FIG. 12 is a Co—Pt laminated film. The Co—Pt laminated film has a structure in which a Co film and a Pt film are repeatedly laminated, and exhibits perpendicular magnetic anisotropy at other than the interface with the MgO film. Also in this structure, the ferromagnetic film 13 is magnetostatically coupled via the free layer 8 and the cap layer 12 as described in FIG. As a result, it acts to stabilize the perpendicular magnetic anisotropy at the interface between the free layer 8 and the cap layer 12. That is, it is possible to stabilize the perpendicular magnetic anisotropy component in the free layer 8 also by having the ferromagnetic film 13 of the Co—Pt laminated film.

  The ferromagnetic layer 13 is formed of a ferromagnetic film mainly containing at least one of a lanthanoid element such as Co (cobalt), Fe (iron), Ni (nickel), and Tb (terbium), or Pt (platinum). ) And Pd (palladium), or a ferromagnetic film having an interface therewith, and a material having magnetic anisotropy in the direction perpendicular to the film surface.

  Next, FIG. 14 corresponding to the laminated structure modification 4 is the structure shown in FIG. 13, in which a Ta film 12b is applied to the cap layer under the ferromagnetic film 13, and as a result, two cap layers 12a and 12b are formed. I have. In this way, by inserting the film 12b of another material on the MgO film 12a of the cap film, it is possible to arbitrarily select a base for growing the ferromagnetic film 13.

  As described above, in the laminated structure modification examples 2 to 4, the cap layer 12 is further provided with the ferromagnetic film 13 in contact with the free layer 8 on the opposite side and having a component magnetized in the vertical direction. As a result, the ferromagnetic film 13 is magnetostatically coupled to the cap layer 12 from the side opposite to the tunnel insulating layer 9, thereby assisting the free layer 8 to be magnetized in the vertical direction. As a result, the magnetization in the vertical direction of the free layer 8 is stabilized.

  As described above, according to the second embodiment, by using a modified example of the laminated structure in the first embodiment, it is possible to stabilize the perpendicular magnetic anisotropy component or to provide a base for growing a ferromagnetic film. The degree of freedom of selection can be expanded.

Embodiment 3 FIG.
In the third embodiment, a specific example in which a plurality of magnetoresistance effect elements 1 are connected in series or in parallel using wirings 4 and 5 will be described. 15 to 18 are schematic diagrams showing connection modification examples 1 to 4 of the magnetoresistive effect element according to the third embodiment of the present invention.

  The operation principle is the same as described above. When using a configuration in which a plurality of magnetoresistive effect elements 1 are connected in series or in parallel as in the third embodiment, the output signal is averaged by a plurality of elements. It is possible to average characteristic variations such as magnetic field responsiveness.

  The number of magnetoresistive effect elements 1 to be connected can be adjusted by averaging resistance and variation. However, in the case of series connection, the voltage dependency symmetry of each element resistance, and a read current described later. In consideration of the symmetry of magnetic field generation due to, it is preferable that the number is even.

  In FIG. 15 corresponding to the connection modification example 1, the arrangement along the longitudinal direction of the magnetoresistive effect element 1 (in the direction in which the longitudinal ends of the magnetoresistive effect elements 1 adjacent to each other are adjacent to each other). The plurality of magnetoresistive elements 1 are connected in series. In this case, it becomes easy to detect a local magnetic field generated along a straight line such as a current detector and wiring described later.

  Further, the arrangement of FIG. 16 corresponding to the connection modification example 2 is arranged along the short direction of the magnetoresistive effect element 1 (the end portions in the short direction of the magnetoresistive effect elements adjacent to each other by the plurality of magnetoresistive effect elements 1). A plurality of magnetoresistive effect elements 1 are connected in series in such a manner that they are arranged so as to face each other. In this arrangement, when a magnetic field is generated by the read current flowing through the wirings 4 and 5, a magnetic field in the longitudinal direction of the magnetoresistive effect element 1 having a direction different from that of the magnetic field to be detected is applied. As a result, it is possible to suppress detection errors caused by the read current.

  In both the arrangements of FIGS. 15 and 16, the wiring 4 is located at the upper part of the magnetoresistive effect element 1 and the wiring 5 is located at the lower part. For this reason, the magnetic fields generated by the current at the position of the magnetoresistive effect element 1 are opposite to each other. As a result, it is possible to suppress a detection error caused by the read current.

  The connection of FIG. 17 corresponding to the connection modification 3 and the connection of FIG. 18 corresponding to the connection modification 4 are connected in parallel with each other along the longitudinal direction and the short direction of the magnetoresistive effect element 1. The effect in this case is the same as the arrangement in series connection. In addition, when connected in series, it is possible to suppress the voltage applied to one magnetoresistive effect element 1, and as a result, it is possible to suppress a decrease in resistance change rate depending on the voltage, It is also possible to prevent the breakdown of the tunnel insulating layer due to the voltage.

  On the other hand, when connected in parallel, the resistance can be reduced in inverse proportion to the number of magnetoresistive effect elements 1, and the resistance can be adjusted according to the application and the peripheral circuit, such as when combined with the series connection. .

  As described above, according to the third embodiment, by using a configuration in which a plurality of magnetoresistive effect elements 1 are connected in series or in parallel, it is possible to average the influence of variation in characteristics between elements. In addition, the asymmetry of the element characteristics with respect to the current direction can be reduced, and the voltage applied to the element can be reduced. As a result, it is possible to suppress magnetic field detection errors by employing a plurality of magnetoresistive elements 1.

Embodiment 4 FIG.
In the previous third embodiment, connection modifications 1 to 4 in which a plurality of magnetoresistance effect elements 1 are connected in series or in parallel have been described. On the other hand, in the fourth embodiment, a connection modification example 5 in which a bridge circuit is configured by using a plurality of magnetoresistive effect elements 1 will be described.

  FIG. 19 is a schematic diagram showing connection modification 5 of the magnetoresistive effect element according to the fourth embodiment of the present invention, and corresponds to an equivalent circuit diagram of the magnetic field detector according to the fourth embodiment.

  A magnetic field detector 100 in FIG. 19 includes a bridge circuit 30 to which a current from the DC power supply 2 is supplied, a differential amplifier 32 that differentially amplifies voltages at nodes N2 and N4 of the bridge circuit 30, and the differential amplifier. And a voltmeter 3 for detecting the voltage level of the 32 output signals. In the magnetic field detector 100, a signal corresponding to the detected magnetic field is output from the bridge circuit 30.

  The bridge circuit 30 is connected between the node N1 and the node N4, the magnetoresistive effect element 1a connected between the node N1 and the node N2, the constant resistance element 31b connected between the node N2 and the ground node N3, and the node N1 and the node N4. Constant resistance element 31a, and magnetoresistive effect element 1b connected between node N4 and ground node N3. The node N1 is connected to the DC power source 2. Nodes N2 and N4 are connected to complementary inputs of the differential amplifier 32, respectively. The ground node N3 is connected to the ground.

  The two magnetoresistive effect elements 1a and 1b have the configuration shown in FIG. 3 described in the first embodiment. The influence of the external magnetic field on the magnetoresistive effect elements 1a and 1b is the same as that described in the first embodiment. Moreover, the resistance values of the constant resistance elements 31a and 31b are the same. A constant current is supplied from the DC power supply 2 to the node N1. In the magnetoresistive effect elements 1a and 1b, the resistance values change with substantially the same characteristics. As a result, the magnitude of the current flowing through the two current paths in the bridge circuit 30, that is, the path of the nodes N1 → N2 → N3, and the current flowing through the nodes N1 → N4 → N3 are the same.

  When the resistance values of the magnetoresistive effect elements 1a and 1b increase due to the influence of the external magnetic field, the voltage at the node N2 decreases, while the voltage level at the node N4 increases. Conversely, when the resistance values of the magnetoresistive effect elements 1a and 1b are reduced by the external magnetic field, the voltage level of the node N2 increases and the voltage level of the node N4 decreases.

  Therefore, the voltage levels of the node N2 and the node N4 change complementarily to the resistance value change of the magnetoresistive effect elements 1a and 1b, and the difference value is amplified by the differential amplifier 32. Thereby, compared with the voltage change by one magnetoresistive effect element, the difference signal change amount of the node N2 and the node N4 becomes large, and the voltmeter 3 can detect the voltage change caused by the external magnetic field with high accuracy. it can.

  With such a configuration, a large output signal can be obtained. Further, the output becomes 0 in the absence of a magnetic field. Furthermore, since the temperature dependence of the magnetoresistive effect elements 1a and 1b can be offset, it is possible to alleviate the change in resistance of the magnetoresistive effect elements 1a and 1b depending on the temperature.

  As described above, according to the fourth embodiment, by configuring a bridge circuit using a plurality of magnetoresistive elements, differential reading is possible, and it is easy to secure 0 point. As a result, the magnetic field can be detected with high accuracy and the change in resistance of the magnetoresistive effect element depending on the temperature can be reduced.

Embodiment 5. FIG.
In the previous third embodiment, connection modifications 1 to 4 in which a plurality of magnetoresistance effect elements 1 are connected in series or in parallel have been described. In the fourth embodiment, connection modification example 5 has been described in which a plurality of magnetoresistive effect elements 1 are used to form a bridge circuit. On the other hand, in the fifth embodiment, a case will be described in which a plurality of magnetoresistive elements having different shapes are formed on the same substrate.

  FIG. 20 is a diagram for explaining the shape dependence of the magnetic characteristics of the magnetoresistive effect element according to the fifth embodiment of the present invention. With reference to FIG. 20, the magnetic characteristics when the element shape is changed using the laminated structure of the magnetoresistive effect element 1 according to the fifth embodiment will be described.

  FIG. 20A shows a case where the ratio of the length in the longitudinal direction to the length in the short direction (shape aspect ratio) is constant for the anisotropic magnetic field in which the magnetization of the ferromagnetic film 8 as the free layer is almost saturated. The dependence on the length in the short direction is shown. FIG. 20B shows the dependency of the shape aspect ratio when the length in the short direction is constant.

  When the rate of change in resistance is constant, the anisotropic magnetic field is inversely proportional to the sensitivity of the magnetoresistive element 1 to the magnetic field. As is clear from this result, the sensitivity of the magnetoresistive effect element 1 changes depending on these shapes. By utilizing this, it is possible to form elements having the same film structure and different sensitivities on the same plane. All elements can be formed at once, and there is no increase in manufacturing process.

  The resistance depending on the element area can be adjusted by combining with the connection modification examples 1 to 4 of the third embodiment.

  As described above, according to the fifth embodiment, it is possible to collectively form magnetoresistive elements whose sensitivity changes depending on the shape as the same film structure on the same plane. That is, a plurality of elements having different sensitivities and operating magnetic fields can be simultaneously formed on the same plane.

Embodiment 6 FIG.
In the sixth embodiment, the magnetoresistive effect element described in the first embodiment is suitable for detecting a magnetic field whose direction is determined (direction along the magnetization 101a in the ferromagnetic layer 10a of the fixed layer), It will be described in detail with reference to the drawings that it is suitable for a current detector used with its position fixed relative to the wiring.

  FIG. 21 is a schematic diagram showing a current detector according to the sixth embodiment of the present invention. As the current detector 102 in FIG. 21, the magnetic field detector 100 having the laminated structure of FIG. 3 described in the first embodiment is used. The current detector 102 is arranged at a certain distance from the wiring that is the device under test 40. A current i to be measured flows through the wiring 40 that is the object to be measured.

  In FIG. 21, only the magnetoresistive effect element 1 is shown, but the current detector 102 has all the configurations shown in the first embodiment. The current detector 102 also includes an output signal detection circuit (not shown).

  The magnetoresistive effect element 1 is arranged so that the direction of the external magnetic field Hex generated from the wiring through which the current i to be measured flows coincides with the detection direction.

Next, the current detection operation in the current detector of the sixth embodiment will be described. When the current i to be measured flows through the wiring 40, an annular magnetic field is generated in a direction perpendicular to the wiring 40 due to the action of the current i. The magnitude of the magnetic field Hex is expressed by the following equation (2).
Hex = k · i / r (2)

  In the above equation (2), k is a proportional constant, and r is the distance from the wiring 40 to the magnetoresistive element 1. If the distance r between the magnetoresistive effect element 1 and the wiring 40 is measured, the proportionality constant k is known, so that the current i can be measured by measuring the magnetic field Hex. The wiring that is the device under test 40 may be disposed on the same substrate as the current detector 102.

  The current detector 102 according to the sixth embodiment measures the current i flowing through the device under test 40 by measuring the magnetic field Hex of the device under test 40 having a magnetic field with the magnetoresistive effect element 1.

  The output signal detection circuit, that is, the calculation unit, converts the current value or voltage value detected by the magnetic detector described in the first embodiment, or the magnetic field strength obtained by converting these values using a conversion formula, into a preset conversion. A function of obtaining the current value i of the DUT 40 based on the equation is included.

  The current i flowing through the device under test 40 is measured by measuring the magnetic field Hex of the device under test 40 with the magnetic field Hex by the magnetoresistive effect element 1. For this reason, in current detection, a stable output signal with few errors can be obtained, and highly accurate current detection can be performed. In addition, the current detector 102 can be easily formed.

  In addition, in FIG. 21, the current detector 102 including one magnetoresistive effect element 1 has been described. However, a modification using a plurality of magnetoresistive effect elements 1 as described in the previous third to fifth embodiments. An example can also be applied. FIG. 22 is a schematic diagram showing connection of magnetoresistive elements of the current detector in the sixth embodiment of the present invention. Specifically, the case where the connection modification example 1 shown in FIG. 15 in the third embodiment is used is shown.

  The magnetic field generated by the current flowing through the wiring 40 is explained by the distribution of concentric circles when viewed in the wiring cross-sectional direction. For this reason, a non-uniform magnetic field is applied to the magnetoresistive effect element 1 especially when the distance between the wiring 40 and the magnetoresistive effect element 1 is short. In order to suppress this, it is preferable to reduce the length occupied by the magnetoresistive effect element 1 in the wiring cross-sectional direction. For this purpose, as shown in FIG. Arrangement of connecting along is preferred.

  The current detector 102 may include a number of magnetoresistive elements 1 other than that shown in FIG. 22, and these magnetoresistive elements 1 are, for example, the bridge circuit shown in FIG. 19 of the fourth embodiment. 30 may be formed. Further, as described in the fifth embodiment, magnetoresistive elements having different sensitivities can be simultaneously formed on the same surface. These Embodiments 3 to 5 can be combined in a timely manner.

  As described above, according to the sixth embodiment, a magnetic field whose direction is determined can be detected with high accuracy using the current detector of the present invention. In particular, when measuring the current flowing through the wiring that is the object to be measured, it is suitable for an application in which the position is fixed with respect to the wiring.

Embodiment 7 FIG.
In the seventh embodiment, a case where a current detector including the magnetoresistive effect element of the present invention is configured as a semiconductor integrated circuit will be described. The semiconductor integrated circuit described in the seventh embodiment of the present invention has the magnetoresistive effect element in the first to fifth embodiments, and includes a current detector that operates in the same manner as in the sixth embodiment. Have. The operation principle of the current detector is the same as that of the sixth embodiment.

  FIG. 23 is a schematic cross-sectional view showing a part of a semiconductor integrated circuit having a current detector according to Embodiment 7 of the present invention. The current detector 102 shown in FIG. 23 uses the magnetoresistive effect element 1 shown in FIG. 3 of the first embodiment. The current detector 102 is installed immediately above the Cu wiring that is the device under test 40. The wiring 40 and the magnetoresistive effect element 1 at this time are insulated by the interlayer insulating film 53, and the distance is determined by the thickness of the interlayer insulating film 53 and the lower electrode 50 disposed under the magnetoresistive effect element 1. Determined by the thickness. A current i for measurement flows through the wiring that is the device under test 40.

  Although only the magnetoresistive effect element 1 is shown in FIG. 23, the current detector 102 has all the configurations shown in the previous sixth embodiment. The current detector 102 also includes an output signal detection circuit (not shown) and is formed in advance in the semiconductor integrated circuit.

  23, as other configurations, a plurality of magnetoresistive effect elements 1 (see FIG. 15 and the like), a direct current (current and voltage) power source 2 (see FIG. 1 and the like), a voltmeter 3 (see FIG. 1 and the like), a current Total wiring (not shown), constant resistance elements 31a and 31b (see FIG. 19 etc.), wiring 4 and 5 for connecting between the differential amplifier 32 (see FIG. 19 etc.), plug 51, interlayer insulating films 52, 53 and 54, 55, 56 are shown. Since the operation method is the same as that of the sixth embodiment, description thereof is omitted here.

  The magnetoresistive effect element 1 included in the semiconductor integrated circuit having the configuration shown in FIG. 23 measures the magnetic field Hex of the device under test 40 (the device under test generating the magnetic field Hex) having the magnetic field Hex. The current i flowing through the device under test 40 is measured. Therefore, a stable output signal with few errors in current detection can be obtained, and highly accurate current detection can be performed. In addition, the current detector 102 can be easily formed.

  Here, when configuring the semiconductor integrated circuit, the bridge circuit described in FIG. 19 in the fourth embodiment is formed, and the constant resistance elements 31a and 31b are also provided with the same elements as the magnetoresistance effect elements 1a and 1b. You may arrange. FIG. 24 is a schematic cross-sectional view showing a part of another semiconductor integrated circuit having a current detector according to Embodiment 7 of the present invention. In FIG. 24, only the magnetoresistive effect elements 1 a and 1 b are installed immediately above the wiring 40, and the magnetoresistive effect elements 1 c and 1 d instead of the constant resistance elements 31 a and 31 b are installed other than just above the wiring 40. Thus, by obtaining the difference between the respective output signals, it is possible to subtract the background signal due to the temperature and the magnetic field of the surrounding environment.

  The magnetoresistive effect elements 1c and 1d may be left as the constant resistance elements 31a and 31b. Thereby, for example, the influence of the magnetic field generated by the peripheral device can be subtracted, and a magnetic shield for suppressing the influence of the magnetic field in the surrounding environment becomes unnecessary.

  As described above, according to the seventh embodiment, it is possible to detect the current using the wiring of the semiconductor integrated circuit using the effects described in the first to sixth embodiments. When the magnetic field detector and current detector of the present invention are configured as a semiconductor integrated circuit, the distance between the magnetoresistive effect element and the device under test is determined by the interlayer insulating film. For this reason, the distance between the magnetoresistive element and the object to be measured can be reduced, and as a result, highly sensitive detection is possible. Furthermore, the influence of the background magnetic field can be suppressed by using an element away from the object to be measured.

Embodiment 8 FIG.
In the eighth embodiment, a case where the magnetic field detector and the current detector of the present invention are configured as a semiconductor integrated circuit different from that of the previous seventh embodiment will be described. FIG. 25 is a schematic cross-sectional view showing a part of a semiconductor integrated circuit having a current detector according to Embodiment 8 of the present invention. In FIG. 25, the current of the power supply line PL from the power supply unit PS to the memory M and the arithmetic circuit OP is always detected by the current detector 102 composed of a magnetoresistive effect element. The detected current value is fed back to the power supply control unit PSC for controlling the power supply unit PS.

  In addition, based on the preset conversion formula from the current value or voltage value detected by the magnetic detector, or the magnetic field intensity obtained by converting these with the conversion formula in the above-described arithmetic unit (output signal detection circuit, etc.). The function of obtaining the current value of the object to be measured may be provided in the power supply control unit PSC.

  As described above, according to the eighth embodiment, it is possible to detect the current supplied to the memory and the arithmetic circuit with high accuracy and high sensitivity without affecting the integrated circuit. As a result, the power consumption of the integrated circuit can be reduced by performing monitoring and feedback of the operation state of the integrated circuit depending on the environment.

  In addition, since the operation | movement here detects the electric current with a magnetic field, the modification demonstrated in FIGS. 11-14 is applicable.

  In the configuration of FIG. 25, various modifications shown in FIGS. 15 to 19 can be applied, and elements having different sensitivities described in FIG. 20 can be formed simultaneously.

  It goes without saying that the present invention is not limited to the above embodiments, and includes all possible combinations of these embodiments.

Claims (12)

A magnetic field detector including a magnetoresistive effect element that detects a magnetic field by the resistance of the magnetoresistive effect element,
The magnetoresistive effect element is
A cap layer comprising an oxide containing Mg;
A free layer composed of a ferromagnetic layer mainly composed of a Co-Fe-B alloy film in contact with the cap layer;
A tunnel insulating layer made of an oxide containing Mg;
And a pinned layer made of a ferromagnetic layer magnetized in the film surface direction facing the free layer through the tunnel insulating layer,
In a state where no magnetic field is applied from the outside,
The free layer has a magnetization in the film plane direction and a magnetization perpendicular to the film plane,
The magnetizations of the free layer and the pinned layer are perpendicular to each other in projection components onto the film surface,
The magnetic field detector provided with the magnetoresistive effect element which detects the magnetic field along the magnetization direction of the said pinned layer with the resistance of the said magnetoresistive effect element. A magnetic field detector comprising the magnetoresistive element according to claim 1.
The magnetoresistive effect element includes a magnetoresistive effect element in which a thickness of the Mg-containing oxide constituting the cap layer is smaller than a thickness of the tunnel insulating layer made of the Mg-containing oxide. Magnetic field detector. A magnetic field detector comprising the magnetoresistive element according to claim 1.
The free layer in the magnetoresistive element is composed of two or more ferromagnetic films having different compositions, and the Fe content of the ferromagnetic film in contact with the tunnel insulating layer is Fe of the ferromagnetic film in contact with the cap layer. Magnetic field detector having a magnetoresistive effect element smaller than the content rate. The magnetoresistive element according to claim 1,
The magnetoresistive effect element further includes a ferromagnetic film in contact with the cap layer on the opposite side of the free layer and having a component magnetized in the vertical direction in the laminated structure. . A magnetic field detector provided with a plurality of magnetoresistive effect elements according to claim 1 that are electrically connected on the same plane. A magnetic field detector comprising the magnetoresistive effect element according to claim 5,
A magnetic field detector comprising a magnetoresistive effect element, wherein a bridge circuit is constituted by a plurality of the magnetoresistive effect elements and a signal corresponding to a detected magnetic field is read from the bridge circuit. A magnetic field detector comprising the magnetoresistive effect element according to claim 5,
The magnetic field detector provided with the magnetoresistive effect element from which the shape of several said magnetoresistive effect element differs, respectively. A magnetic field detector comprising the magnetoresistive element according to claim 1.
The magnetoresistive effect element is formed as a rectangle having a planar element shape having a longitudinal direction and a short direction that is a direction intersecting the longitudinal direction,
In a state where no magnetic field is applied from the outside,
The magnetization direction of the pinned layer is directed in the short direction by film formation and heat treatment,
The magnetization direction of the free layer is directed in the longitudinal direction by the element shape,
A magnetic field detector comprising a magnetoresistive effect element, wherein the magnetization direction of the pinned layer and the magnetization direction of the free layer are orthogonal to each other when viewed from the projection surface from the upper surface of the magnetoresistive effect element. A magnetic field detector comprising the magnetoresistive effect element according to any one of claims 1 to 8,
A magnetic field measured by a magnetic field detector provided with the magnetoresistive effect element with respect to a measured object having a magnetic field, a distance between the magnetoresistive effect element and the measured object, and a current flowing through the measured object. A current detector comprising: an arithmetic unit that measures a current flowing through the device under test from a relational expression. A magnetic field detector comprising the magnetoresistive element according to claim 5;
A magnetic field measured by a magnetic field detector provided with a plurality of magnetoresistive elements with respect to a measured object having a magnetic field, a distance between the magnetoresistive elements and the measured object, and a current flowing through the measured object An arithmetic unit that measures the current flowing through the object to be measured from the relational expression
Current detectors having different distances from each of the plurality of magnetoresistive elements to the object to be measured. A magnetic field detector comprising the magnetoresistive element according to claim 5;
A magnetic field measured by a magnetic field detector provided with a plurality of magnetoresistive elements with respect to a measured object having a magnetic field, a distance between the magnetoresistive elements and the measured object, and a current flowing through the measured object An arithmetic unit that measures the current flowing through the object to be measured from the relational expression
A current detector in which the plurality of magnetoresistive elements have different shapes. The current detector according to claim 9.
A current detector in which a wiring portion of the device under test, the magnetoresistive effect element, and the magnetoresistive effect element is integrally formed by a semiconductor integrated circuit.

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