JP2013168667A - Magnetoresistance effect element and mram - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a writing current for a magnetoresistance effect element of a spin injection system.SOLUTION: A magnetoresistance effect element comprises: a first magnetization fixed layer in which a magnetization direction is fixed at a first direction; a second magnetization fixed layer in which the magnetization direction is fixed at a second direction opposite to the first direction; and a magnetization free layer in which a magnetization easy axis direction is parallel to the first direction and the second direction. The first magnetization fixed layer is connected to the magnetization free layer via a non-magnetic layer in a first region. The second magnetization fixed layer is connected to the magnetization free layer via the non-magnetic layer in a second region away from the first region in the magnetization easy axis direction. A writing current flows between the first magnetization fixed layer and the second magnetization fixed layer via the magnetization free layer.

Description

  The present invention relates to a magnetoresistive effect element and a magnetic random access memory (MRAM) using the magnetoresistive effect element as a memory cell. In particular, the present invention relates to an MRAM based on a spin injection method and a magnetoresistive effect element used in the MRAM.

  MRAM is a promising nonvolatile memory from the viewpoint of high integration and high-speed operation. In the MRAM, a “magnetoresistance effect element” showing a magnetoresistance effect such as a TMR (Tunnel MagnetoResistance) effect is used as a memory cell. In the magnetoresistive effect element, for example, a magnetic tunnel junction (MTJ: Magnetic Tunnel Junction) in which a tunnel barrier layer is sandwiched between two ferromagnetic layers is formed. The two ferromagnetic layers are composed of a magnetization pinned layer (pinned layer) whose magnetization direction is fixed and a magnetization free layer (free layer) whose magnetization direction can be reversed. .

  The resistance value (R + ΔR) of the MTJ when the magnetization direction of the magnetization fixed layer and the magnetization free layer is “antiparallel” is larger than the resistance value (R) when they are “parallel” due to the magnetoresistance effect. It is known to grow. The MR ratio (= ΔR / R) at room temperature is several 10 to several 100%. The memory cell of the MRAM stores data in a nonvolatile manner by utilizing the change in resistance value. Data is read by passing a read current through the MTJ and measuring the resistance value of the MTJ. On the other hand, data is written by reversing the magnetization direction of the magnetization free layer.

  As a typical data writing method, a “current magnetic field method” is known. According to the current magnetic field method, a write current is caused to flow through the write wiring arranged in the vicinity of the magnetoresistive effect element. A write magnetic field generated by the write current is applied to the magnetization free layer, thereby changing the magnetization direction of the magnetization free layer. In the current magnetic field method, the reversal magnetic field necessary for the magnetization reversal of the magnetization free layer increases substantially in inverse proportion to the size of the magnetoresistive effect element. That is, there is a problem that the write current increases as the memory cell is miniaturized.

  As a data writing method that can suppress an increase in write current accompanying miniaturization, a “spin injection method” using spin transfer has been proposed (see Non-Patent Document 1). According to the spin injection method, a spin-polarized current is injected into the magnetization free layer, and the magnetization is reversed by a direct interaction between the spin torque of the conduction electrons that carry the current and the magnetic moment of the conductor. (Spin injection magnetization reversal).

  FIG. 1 is a diagram for explaining spin injection magnetization reversal. In FIG. 1, the magnetoresistive effect element includes a magnetization free layer 101, a magnetization fixed layer 103, and a tunnel barrier layer 102 that is a nonmagnetic layer sandwiched between the magnetization free layer 101 and the magnetization fixed layer 103. Here, the magnetization fixed layer 103 whose magnetization direction is fixed serves as a spin filter. The state where the magnetization directions of the magnetization free layer 101 and the magnetization fixed layer 103 are parallel is associated with data “0”, and the state where they are antiparallel is associated with data “1”.

  The spin injection magnetization reversal shown in FIG. 1 is realized by a CPP (Current Perpendicular to Plane) method, and a write current is passed through the MTJ. Specifically, at the time of transition from data “0” to data “1”, the write current flows from the magnetization fixed layer 103 to the magnetization free layer 101, and electrons move from the magnetization free layer 101 to the magnetization fixed layer 103. At this time, electrons having a spin in the direction opposite to the magnetization of the magnetization fixed layer 103 as a spin filter are reflected by the magnetization fixed layer 103. Electrons having a spin in the same direction as the magnetization of the magnetization fixed layer 103 move from the magnetization free layer 101 to the magnetization fixed layer 103, and the magnetization of the magnetization free layer 101 is reversed by a spin transfer (transfer of spin angular momentum) effect. On the other hand, at the time of transition from data “1” to data “0”, the write current flows from the magnetization free layer 101 to the magnetization fixed layer 103, and electrons move from the magnetization fixed layer 103 to the magnetization free layer 101. At this time, electrons having spins in the same direction as the magnetization of the magnetization fixed layer 103 are injected from the magnetization fixed layer 103 into the magnetization free layer 101. As a result, the magnetization of the magnetization free layer 101 is reversed by the spin transfer effect.

  Thus, in the spin injection method, data is written by movement of spin-polarized electrons. The direction of magnetization of the magnetization free layer 101 can be defined by the direction of the write current. Here, it is known that the threshold for writing (magnetization reversal) depends on the current density. Therefore, as the memory cell size is reduced, the write current required for magnetization reversal decreases. Since the write current decreases with the miniaturization of the memory cell, the spin injection method is important for realizing a large capacity of the MRAM.

  The MRAM based on the spin injection method is also described in Patent Document 1 and Patent Document 2.

  The magnetoresistive effect element described in Patent Document 1 has a storage layer that holds information according to the magnetization state of a magnetic material. A fixed magnetization layer is provided above and below the storage layer via an intermediate layer, and each intermediate layer is made of an insulating layer. In the magnetization fixed layers above and below the storage layer, the magnetization directions of the ferromagnetic layers closest to the storage layer are opposite to each other. By passing a current in the stacking direction, the magnetization direction of the storage layer changes, and information is recorded on the storage layer. The two intermediate layers above and below the storage layer have a significant difference in sheet resistance value, and the magnetoresistance change rate of the intermediate layer having the higher sheet resistance value is higher than the magnetoresistance change rate of the intermediate layer having the lower sheet resistance value. large.

  The magnetoresistive effect element described in Patent Literature 2 includes a first pinned layer, a free layer, a nonmagnetic spacer layer positioned between the first pinned layer and the free layer, a second pinned layer, and a second pinned layer. And a barrier layer positioned between the free layer. The first pinned layer has a first magnetization fixed in the first direction. The free layer has a second magnetization. The second pinned layer has a third magnetization fixed in the second direction. The thickness of the barrier layer is designed to allow tunneling. The first direction is opposite to the second direction. The direction of the second magnetization of the free layer is changed by spin transfer when the write current flows through the magnetoresistive element.

  The conventional spin injection MRAM described above is designed such that not only the read current but also the write current flows through the MTJ. Therefore, the tunnel barrier layer included in the MTJ is likely to deteriorate. Furthermore, there is a possibility that data writing is erroneously performed at the time of data reading. That is, unless the value of the read current is sufficiently smaller than the data write threshold, the read current may invert the magnetization of the magnetization free layer. In order to reduce such a risk, it is conceivable to reduce the read current or increase the data write threshold. However, as the read current becomes smaller, the quality of the read signal (such as the signal-to-noise ratio) deteriorates, making it difficult to read data at high speed and accurately. Further, it is not preferable to increase the threshold value for writing from the viewpoint of power consumption and transistor size.

  Patent Document 3 describes a three-terminal magnetoresistive element based on a spin injection method.

  FIG. 2 shows an example of a three-terminal magnetoresistive element. The magnetoresistive effect element includes a first wiring layer 111, a first antiferromagnetic layer 112, a first magnetization fixed layer 113, a first tunnel barrier layer 114, a magnetization free layer 130, a second tunnel barrier layer 124, and a second magnetization. The pinned layer 123, the second antiferromagnetic layer 122, and the second wiring layer 121 are stacked in order. The magnetizations of the magnetization fixed layers 113 and 123 are fixed in the −X direction by the antiferromagnetic layers 112 and 122, respectively. The magnetization free layer 130 extends in the X direction, and its easy axis is along the X direction. The magnetization of the magnetization free layer 130 is reversible and faces the + X direction or the −X direction. Further, the magnetization free layer 130 is connected to the third wiring layer 131 in a region different from the laminated structure.

  In the configuration shown in FIG. 2, a write current flows between the second wiring layer 121 and the third wiring layer 131 when writing data. Then, the magnetization of the magnetization free layer 130 is reversed by spin transfer between the second magnetization fixed layer 123 and the magnetization free layer 130. On the other hand, when reading data, a read current flows between the first wiring layer 111 and the third wiring layer 131. Then, the resistance value of the MTJ including the first magnetization fixed layer 113 and the magnetization free layer 130 is detected. Thus, data writing and data reading are realized by separate current paths. Therefore, deterioration of the tunnel barrier layer is suppressed. In addition, by designing the write characteristics and the read characteristics separately, it is possible to prevent erroneous writing during data reading.

  FIG. 3 shows another example of a three-terminal magnetoresistive element. This magnetoresistive effect element includes a first wiring layer 111, a first antiferromagnetic layer 112, a first magnetization fixed layer 113, a first tunnel barrier layer 114, a first magnetization free layer 115, an intermediate wiring layer 150, a second magnetization. The free layer 125, the second tunnel barrier layer 124, the second magnetization fixed layer 123, the second antiferromagnetic layer 122, and the second wiring layer 121 are stacked in order. The magnetizations of the magnetization fixed layers 113 and 123 are fixed in the −X direction by the antiferromagnetic layers 112 and 122, respectively. The magnetization easy axes of the magnetization free layers 115 and 125 are along the X direction, and their magnetizations can be reversed, and are oriented in the + X direction or the −X direction. In addition, the magnetization free layers 115 and 125 are magnetostatically coupled to each other, and when one magnetization is reversed, the other magnetization is also reversed. The intermediate wiring layer 150 extends in the X direction, and is connected to the third wiring layer 131 in a region different from the stacked structure.

  In the configuration shown in FIG. 3, a write current flows between the second wiring layer 121 and the third wiring layer 131 when writing data. Then, the magnetization of the second magnetization free layer 125 is reversed by spin transfer between the second magnetization fixed layer 123 and the second magnetization free layer 125. When the magnetization of the second magnetization free layer 125 is reversed, the magnetization of the first magnetization free layer 115 is also reversed. On the other hand, when reading data, a read current flows between the first wiring layer 111 and the third wiring layer 131. Then, the resistance value of the MTJ including the first magnetization fixed layer 113 and the first magnetization free layer 115 is detected. Thus, data writing and data reading are realized by separate current paths. Therefore, deterioration of the tunnel barrier layer is suppressed. In addition, by designing the write characteristics and the read characteristics separately, it is possible to prevent erroneous writing during data reading.

JP 2006-93432 A JP 2005-535125 A JP-A-2005-116888

M. Hosomi et al., "ANovel Nonvolatile Memory with Spin Torque Transfer Magnetization Switching: Spin-RAM", International Electron Devices Meeting (IEDM), Technical Digest, pp.459-562, 2005.

  The inventor of the present application paid attention to the following points. That is, according to the technique described in Patent Document 3, the write current cannot be sufficiently reduced. For example, in the configuration shown in FIG. 2, the spin injection efficiency decreases due to the spin scattering in the portion of the magnetization free layer 130 that extends in the direction of the third wiring layer 131. This causes an increase in write current. In the configuration shown in FIG. 3, although the spin injection efficiency does not decrease, in addition to the magnetization of the second magnetization free layer 125, the magnetization of the first magnetization free layer 115 needs to be reversed although indirectly. . Therefore, the write current increases as compared with the case of a single magnetization free layer (see FIG. 1).

  An object of the present invention is to provide a new magnetoresistive effect element and MRAM based on a spin injection method.

  Another object of the present invention is to provide a magnetoresistive element and an MRAM that can prevent erroneous writing during data reading.

  Still another object of the present invention is to provide a magnetoresistive effect element and an MRAM that can reduce a write current and reduce power consumption.

  In one aspect of the present invention, a spin-injection magnetoresistive element is provided. The magnetoresistive element includes a first write magnetization fixed layer whose magnetization direction is fixed in the first direction, a second write magnetization fixed layer whose magnetization direction is fixed in a second direction opposite to the first direction, A magnetization free layer whose easy axis direction is parallel to the first direction and the second direction. The first write magnetization fixed layer is connected to the magnetization free layer via the first write nonmagnetic layer in the first region. The second write magnetization fixed layer is connected to the magnetization free layer via the second write nonmagnetic layer in the second region separated from the first region in the easy axis direction. At the time of data writing, a write current flows between the first write magnetization fixed layer and the second write magnetization fixed layer through the magnetization free layer.

  According to the present invention, a new magnetoresistive effect element and MRAM based on the spin injection method are provided. According to the magnetoresistive effect element and the MRAM according to the present invention, it is possible to prevent erroneous writing during data reading. Further, the write current can be reduced and the power consumption can be reduced.

FIG. 1 is a conceptual diagram for explaining data writing based on a conventional spin injection method. FIG. 2 is a side view showing an example of a conventional three-terminal magnetoresistive element based on the spin injection method. FIG. 3 is a side view showing another example of a conventional three-terminal magnetoresistive element based on the spin injection method. FIG. 4 is a perspective view showing the structure of the magnetoresistance effect element according to the first exemplary embodiment of the present invention. 5A is an XZ side view of the magnetoresistive element shown in FIG. FIG. 5B is a YZ side view of the magnetoresistive element shown in FIG. 4. FIG. 6 is a conceptual diagram for explaining data writing to the magnetoresistive effect element according to the first embodiment. FIG. 7 is a conceptual diagram for explaining data reading for the magnetoresistive effect element according to the first embodiment. FIG. 8 is an XY plan view showing the extending direction of the intermediate wiring layer included in the magnetoresistive effect element according to the first embodiment. FIG. 9 is a perspective view showing another structure of the magnetoresistance effect element according to the first exemplary embodiment. FIG. 10 is an XY plan view showing the extending direction of the intermediate wiring layer included in the magnetoresistive effect element according to the first embodiment. FIG. 11 is a YZ side view showing a modification of the magnetoresistive effect element according to the first embodiment. FIG. 12 is a YZ side view showing another modification of the magnetoresistive effect element according to the first embodiment. FIG. 13 is a circuit diagram showing a configuration example of the MRAM having the magnetoresistive effect element according to the first embodiment. FIG. 14 is a side view showing the structure of the magnetoresistive element according to the second embodiment of the invention. FIG. 15 is a side view showing a modification of the magnetoresistance effect element according to the second exemplary embodiment.

  A magnetoresistive effect element and an MRAM according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1. 1. First embodiment 1-1. Basic Structure FIG. 4 is a perspective view showing the structure of the magnetoresistive effect element (magnetic memory cell) 1 according to the first embodiment of the present invention. The magnetoresistive effect element 1 according to the present exemplary embodiment includes a first wiring layer 11, a first antiferromagnetic layer 12, a first magnetization fixed layer 13, a first tunnel barrier layer 14, a first magnetization free layer 15, and an intermediate wiring. The layer 50, the second magnetization free layer 25, the second tunnel barrier layer 24, the second magnetization fixed layer 23, the second antiferromagnetic layer 22, and the second wiring layer 21 are stacked in order. Yes. The first wiring layer 11, the first antiferromagnetic layer 12, the first magnetization fixed layer 13, the first tunnel barrier layer 14, and the first magnetization free layer 15 constitute a first stacked structure 10. On the other hand, the second magnetization free layer 25, the second tunnel barrier layer 24, the second magnetization fixed layer 23, the second antiferromagnetic layer 22, and the second wiring layer 21 constitute a second stacked structure 20. The intermediate wiring layer 50 is interposed between the first stacked structure 10 and the second stacked structure 20.

  In this specification, the stacking direction of the above-described layers is defined as the Z direction. A plane perpendicular to the Z direction is defined as an XY plane. The X direction, the Y direction, and the Z direction are orthogonal to each other. 5A and 5B are an XZ side view and a YZ side view of the magnetoresistive effect element shown in FIG.

  As shown in FIG. 5A, the first antiferromagnetic layer 12 is formed on the first wiring layer 11, and the first magnetization fixed layer 13 is formed on the first antiferromagnetic layer 12. A first magnetization free layer 15 is formed on the first magnetization fixed layer 13 via a first tunnel barrier layer 14. An intermediate wiring layer 50 is formed on the first magnetization free layer 15, and a second magnetization free layer 25 is formed on the intermediate wiring layer 50. That is, the intermediate wiring layer 50 is interposed between the first magnetization free layer 15 and the second magnetization free layer 25. A second magnetization fixed layer 23 is formed on the second magnetization free layer 25 via a second tunnel barrier layer 24. A second antiferromagnetic layer 22 is formed on the second magnetization fixed layer 23, and a second wiring layer 21 is formed on the second antiferromagnetic layer 22.

  The magnetization fixed layers (pinned layers) 13 and 23 include a ferromagnetic layer, and the magnetization direction is fixed. For example, in FIG. 5A, the magnetization (first fixed magnetization MP1) of the first magnetization fixed layer 13 is fixed in the −X direction by the adjacent first antiferromagnetic layer 12. Further, the magnetization (second fixed magnetization MP2) of the second magnetization fixed layer 23 is also fixed in the −X direction by the adjacent second antiferromagnetic layer 22. The first fixed magnetization MP1 and the second fixed magnetization MP2 may be fixed in opposite directions along the X direction. Further, instead of using the antiferromagnetic layers 12 and 22, the magnetization fixed layers 13 and 23 may be formed of a material having a sufficiently large coercive force. Each of the magnetization fixed layers 13 and 23 may have a stacked structure in which a plurality of ferromagnetic layers are magnetically coupled via a nonmagnetic layer. In that case, for example, adjacent ferromagnetic layers are antiferromagnetically coupled via a nonmagnetic layer. As a result, the leakage magnetic field is reduced, and the fixed magnetization becomes stronger.

  The magnetization free layers (free layers) 15 and 25 include ferromagnetic layers, and their magnetization directions are variable. More specifically, the magnetization easy axes of the magnetization free layers 15 and 25 are along the X direction, and their magnetization can be reversed. The magnetization (first inversion magnetization MF1) of the first magnetization free layer 15 is allowed to face the + X direction or the −X direction, that is, be antiparallel or parallel to the first fixed magnetization MP1. The magnetization (second reversal magnetization MF2) of the second magnetization free layer 25 is allowed to face the + X direction or the -X direction, that is, antiparallel or parallel to the second fixed magnetization MP2. Further, the magnetization free layers 15 and 25 are magnetically coupled via the intermediate wiring layer 50. Therefore, when one of the first inversion magnetization MF1 and the second inversion magnetization MF2 is inverted, the other is also inverted. For example, the magnetization free layers 15 and 25 are magnetostatically coupled to each other, and the first inversion magnetization MF1 and the second inversion magnetization MF2 are opposite to each other. The magnetic anisotropy of the magnetization free layers 15 and 25 is any one of crystal magnetic anisotropy depending on the material, strain-induced anisotropy, shape magnetic anisotropy depending on the planar shape, or a combination thereof. Determined by. The magnetization free layers 15 and 25 may have a laminated structure in which a plurality of ferromagnetic layers are magnetically coupled via a nonmagnetic layer.

  The tunnel barrier layers 14 and 24 are nonmagnetic layers. For example, the tunnel barrier layers 14 and 24 are formed of an insulating film. The first magnetization fixed layer 13 and the first magnetization free layer 15 are connected via a tunnel barrier layer 14. As a result, one MTJ is formed in the first stacked structure 10. Further, the second magnetization fixed layer 23 and the second magnetization free layer 25 are connected via a tunnel barrier layer 24. Thereby, another MTJ is formed in the second stacked structure 20.

  As shown in FIG. 5B, the first stacked structure 10 and the second stacked structure 20 are formed in the first region R1. The intermediate wiring layer 50 overlaps the first stacked structure 10 and the second stacked structure 20 in the first region R1. Further, the intermediate wiring layer 50 extends in the + Y direction from the first region R1. That is, the intermediate wiring layer 50 has a planar shape whose longitudinal direction is the Y direction. The intermediate wiring layer 50 is connected to the third wiring layer 31 in the second region R2 located in the + Y direction from the first region R1. In FIG. 5B, the third wiring layer 31 is formed on the intermediate wiring layer 50 in the second region R2 different from the first region R1.

The material of each layer is, for example, as follows. The wiring layers 11, 21, 31 and the intermediate wiring layer 50 are formed of a metal such as Al or Cu. The antiferromagnetic layers 12 and 22 are made of FeMn, IrMn, PtMn, or the like. The ferromagnetic layers in the magnetization fixed layers 13 and 23 and the magnetization free layers 15 and 25 contain at least one element selected from Co, Fe, and Ni. For example, the ferromagnetic layers of the magnetization fixed layers 13 and 23 and the magnetization free layers 15 and 25 are made of CoFe, NiFe, NiFeCo, CoFeB, or the like. Examples of the tunnel barrier layers 14 and 24 that are nonmagnetic layers include insulating films such as Al ₂ O ₃ films, SiO ₂ films, MgO films, and AlN films. The tunnel barrier layer (24) used in data writing to be described later may be a nonmagnetic metal layer such as Cu.

  The first wiring layer 11, the second wiring layer 21, and the third wiring layer 31 are used for supplying a write current and a read current to the magnetoresistive effect element 1 as described below. That is, the magnetoresistive effect element 1 according to the present exemplary embodiment is a three-terminal type.

1-2. Operation (data writing)
FIG. 6 is a conceptual diagram for explaining data writing according to the present embodiment. The state in which the direction of the first inversion magnetization MF1 of the first magnetization free layer 15 is in the −X direction, that is, the “parallel state” in which the direction is parallel to the direction of the first fixed magnetization MP1 (−X direction) is data. Corresponding to “0”. In this parallel state, the direction of the second inversion magnetization MF2 of the second magnetization free layer 25 is the + X direction. On the other hand, the state of the first inversion magnetization MF1 of the first magnetization free layer 15 is the + X direction, that is, the “antiparallel state” in which the direction is antiparallel to the direction of the first fixed magnetization MP1 (−X direction). Is associated with data “1”. In this antiparallel state, the direction of the second inversion magnetization MF2 of the second magnetization free layer 25 is the −X direction. The MTJ resistance value in the first stacked structure 10 is relatively small in the parallel state (data “0”) and relatively large in the anti-parallel state (data “1”).

  At the time of writing data “1”, a write current IW 1 is caused to flow from the third wiring layer 31 to the second wiring layer 21. That is, the write current IW1 flows from the third wiring layer 31 to the intermediate wiring layer 50, and further flows from the intermediate wiring layer 50 to the second wiring layer 21 through the MTJ in the second stacked structure 20. In this case, electrons move from the second magnetization fixed layer 23 to the second magnetization free layer 25. Specifically, electrons having a spin in the −X direction are injected from the second magnetization fixed layer 23 to the second magnetization free layer 25. As a result of the spin transfer between the second magnetization fixed layer 23 and the second magnetization free layer 25, the second inversion magnetization MF2 of the second magnetization free layer 25 is inverted from the + X direction to the −X direction. When the second reversal magnetization MF2 is reversed, the first reversal magnetization MF1 of the first magnetization free layer 15 is also reversed from the −X direction to the + X direction. In this way, the antiparallel state (data “1”) is realized.

  Here, it should be noted that the magnetic field B1 is generated by the write current IW1 that flows through the intermediate wiring layer 50 in a plane. Since the write current IW1 flows in the −Y direction through the intermediate wiring layer 50, the magnetic field B1 includes a −X direction component on the upper side of the intermediate wiring layer 50 and a + X direction component on the lower side thereof. . At the time of data writing, the magnetic field B1 is applied to the magnetization free layers 15 and 25 simultaneously with the spin injection. In the second magnetization free layer 25, the magnetic field B1 includes a component in the −X direction, and the direction coincides with the inversion direction of the second inversion magnetization MF2. In other words, the magnetic field B1 applied to the second magnetization free layer 25 assists the reversal of the second reversal magnetization MF2. In that sense, the magnetic field B1 generated by the write current IW1 can also be called an “assist magnetic field”. On the other hand, in the first magnetization free layer 15, the assist magnetic field B1 includes a component in the + X direction, and the direction coincides with the inversion direction of the first inversion magnetization MF1. That is, the assist magnetic field B1 assists the reversal of the first reversal magnetization MF1.

  On the other hand, when data “0” is written, the write current IW 2 flows from the second wiring layer 21 to the third wiring layer 31. That is, the write current IW2 flows from the second wiring layer 21 through the MTJ in the second stacked structure 20 to the intermediate wiring layer 50, and further flows from the intermediate wiring layer 50 to the third wiring layer 31. In this case, the electrons move from the second magnetization free layer 25 to the second magnetization fixed layer 23. Specifically, electrons having a spin in the + X direction are reflected by the second magnetization fixed layer 23 as a spin filter, and electrons having a spin in the −X direction are transferred from the second magnetization free layer 25 to the second magnetization fixed layer 23. Moving. As a result of the spin transfer between the second magnetization fixed layer 23 and the second magnetization free layer 25, the second inversion magnetization MF2 of the second magnetization free layer 25 is inverted from the −X direction to the + X direction. When the second reversal magnetization MF2 is reversed, the first reversal magnetization MF1 of the first magnetization free layer 15 is also reversed from the + X direction to the −X direction. In this way, a parallel state (data “0”) is realized.

  Also in this case, the assist magnetic field B2 is generated by the write current IW2 that flows in a plane in the intermediate wiring layer 50. Since the write current IW2 flows through the intermediate wiring layer 50 in the + Y direction, the assist magnetic field B2 includes a component in the + X direction on the upper side of the intermediate wiring layer 50 and a component in the −X direction on the lower side. . At the time of data writing, the assist magnetic field B2 is applied to the magnetization free layers 15 and 25 simultaneously with the spin injection. In the magnetization free layers 15 and 25, the direction of the assist magnetic field B2 coincides with the magnetization reversal direction. That is, the assist magnetic field B2 assists the reversal of the second reversal magnetization MF2 and the first reversal magnetization MF1.

  Thus, according to the present embodiment, the assist magnetic field (B1, B2) is applied to the second magnetization free layer 25 simultaneously with the spin injection. As a result, the second reversal magnetization MF2 is easily reversed. Therefore, the magnitude of the write current (IW1, IW2) can be made smaller than before. In other words, since there is assist by the assist magnetic field, data writing is sufficiently realized even if the write current is reduced. Further, since the direction of the assist magnetic field is reversed above and below the intermediate wiring layer 50, it is preferable that the first reversal magnetization MF1 and the second reversal magnetization MF2 are also magnetically coupled so as to be opposite to each other. . As a result, the assist magnetic field assists the reversal of both the first reversal magnetization MF1 and the second reversal magnetization MF2. As a result, the write current can be further reduced.

(Data read)
FIG. 7 is a conceptual diagram for explaining data reading according to the present embodiment. At the time of data reading, the read current IR flows from the third wiring layer 31 to the first wiring layer 11 or from the first wiring layer 11 to the third wiring layer 31. In FIG. 7, the read current IR flows from the third wiring layer 31 to the intermediate wiring layer 50, and further passes through the MTJ in the first stacked structure 10 from the intermediate wiring layer 50 to the first wiring layer. 11 flows. Thereby, the resistance value of the MTJ in the first stacked structure 10 can be detected. For example, the magnitude of the MTJ resistance value can be detected by comparing a voltage corresponding to the read current IR with a predetermined reference voltage. As a result, it is possible to sense whether the data stored in the magnetoresistive element (magnetic memory cell) 1 is “0” or “1”.

  As described above, in the example shown in FIGS. 6 and 7, one first stacked structure 10 is used for data reading, and the other second stacked structure 20 is used for data writing. That is, data writing and data reading are realized by separate current paths. Therefore, deterioration of the tunnel barrier layers 14 and 24 is suppressed. In addition, erroneous writing during data reading can be prevented. Further, since the write characteristic and the read characteristic can be designed separately, the write characteristic and the read characteristic can be optimized.

1-3. Direction of Intermediate Wiring Layer The extending direction of the intermediate wiring layer 50 is not limited to the + Y direction in the above example. Generally speaking, it is only necessary that the assist magnetic field (B1, B2) generated by the write current flowing through the intermediate wiring layer 50 includes at least an X component that promotes reversal of the second reversal magnetization MF2. Therefore, the extending direction of the intermediate wiring layer 50 only needs to include a component along at least the + Y direction.

  FIG. 8 shows various examples of the extending direction of the intermediate wiring layer 50 when the second stacked structure 20 is used for data writing. FIG. 8 shows an XY planar shape when viewed from the + Z direction, that is, when the intermediate wiring layer 50 is viewed from the second stacked structure 20. As described above, in order for the assist magnetic field to assist the magnetization reversal, it is sufficient that the extending direction of the intermediate wiring layer 50 includes at least a component along the + Y direction. Accordingly, not only the intermediate wiring layer 50a extending in the Y direction but also the intermediate wiring layer 50b extending in the S direction and the intermediate wiring layer 50c extending in the T direction can provide the same effect. Generally speaking, the extension direction of the intermediate wiring layer 50 is clockwise from the direction (−X direction) of the second fixed magnetization MP2 when the intermediate wiring layer 50 is viewed from the second stacked structure 20 used for data writing. Any direction that is larger than 0 degree and smaller than 180 degrees may be used (0 degree <θ <180 degrees). However, from the viewpoint of assist efficiency, it is preferable that the extending direction of the intermediate wiring layer 50 is about 90 degrees as shown in FIGS.

  The extending direction of the intermediate wiring layer 50 also depends on which of the first laminated structure 10 and the second laminated structure 20 is used for data writing.

  FIG. 9 shows a structural example of the magnetoresistive effect element 1 when the first stacked structure 10 is used for data writing and the second stacked structure 20 is used for data reading. In this case, the intermediate wiring layer 50 extends in the −Y direction from the first region R1. When reading data, the read current IR flows between the second wiring layer 21 and the third wiring layer 31. At the time of data writing, a write current is passed between the first wiring layer 11 and the third wiring layer 31. Specifically, when data “1” is written, the write current IW1 flows from the first wiring layer 11 to the third wiring layer 31. On the other hand, when data “0” is written, the write current IW 2 flows from the third wiring layer 31 to the first wiring layer 11. Thereby, like the example shown in FIG. 6, the assist magnetic fields B1 and B2 assist the magnetization reversal.

  FIG. 10 shows various examples of the extending direction of the intermediate wiring layer 50 when the first stacked structure 10 is used for data writing. In this case, in order for the assist magnetic field to assist the magnetization reversal, it is sufficient that the extending direction of the intermediate wiring layer 50 includes at least a component along the −Y direction. Therefore, not only the intermediate wiring layer 50d extending in the −Y direction but also the intermediate wiring layer 50e extending in the U direction and the intermediate wiring layer 50f extending in the V direction can provide the same effect. Generally speaking, the extension direction of the intermediate wiring layer 50 is the direction of the first fixed magnetization MP1 when the intermediate wiring layer 50 is viewed from the first stacked structure 10 used for data writing (when viewed from the −Z direction). Any direction that is larger than 0 degree and smaller than 180 degrees clockwise from (−X direction) may be used (0 degree <θ <180 degrees). However, from the viewpoint of assist efficiency, it is preferable that the extending direction of the intermediate wiring layer 50 is about 90 degrees as shown in FIG.

  As described above, either the first stacked structure 10 or the second stacked structure 20 may be used for data writing. In any case, when the intermediate wiring layer 50 is viewed from the magnetization fixed layer used for data writing, the extension direction of the intermediate wiring layer 50 is greater than 0 degree and greater than 180 degrees clockwise from the magnetization direction of the magnetization fixed layer. Any smaller direction is acceptable. In addition, the extending | stretching direction here means the direction from 1st area | region R1 to 2nd area | region R2. The intermediate wiring layer 50 may pass between the first stacked structure 10 and the second stacked structure 20 and extend to the opposite side to the second region R2. The part extending in the opposite direction does not affect the operation. In addition, when the magnetization fixed layer has a laminated structure in which a plurality of ferromagnetic layers are magnetically coupled via a nonmagnetic layer, the magnetization direction serving as a reference for the stretching direction is that of the ferromagnetic layer closest to the magnetization free layer. It is the direction of magnetization.

1-4. Modification FIG. 11 is a YZ side view showing a modification of the magnetoresistive effect element according to the present embodiment. In FIG. 11, the same reference numerals are given to the same components as those already described. The magnetoresistive effect element 1a according to this modification has a third stacked structure 30 in the second region R2. The third stacked structure 30 includes a third magnetization free layer 35, a third tunnel barrier layer 34, a third magnetization fixed layer 33, a third antiferromagnetic layer 32, and a first layer formed in order on the intermediate wiring layer 50. Three wiring layers 31 are included. That is, the intermediate wiring layer 50 is connected to the third wiring layer 31 via the layers 32 to 35 in the second region R2.

  These layers 32 to 35 do not contribute to data writing and data reading. This is because the flow of electrons in the second stacked structure 20 and the third stacked structure 30 is opposite. Since the spin transfer in the third stacked structure 30 is offset by the assist magnetic field, the probability that the magnetization of the third magnetization free layer 35 is reversed is extremely low. Even if the magnetization of the third magnetization free layer 35 is reversed, it does not affect the first reversed magnetization MF1 of the first magnetization free layer 15 for reading data. This is because the third magnetization free layer 35 is separated from the first magnetization free layer 15 for reading data.

  The third stacked structure 30 is simultaneously formed in the same process as the process of forming the second stacked structure 20. That is, the thicknesses of the third magnetization free layer 35, the third tunnel barrier layer 34, the third magnetization fixed layer 33, the third antiferromagnetic layer 32, and the third wiring layer 31 are the second magnetization free layer 25, The thicknesses of the second tunnel barrier layer 24, the second magnetization fixed layer 23, the second antiferromagnetic layer 22, and the second wiring layer 21 are the same. In the case of the structure shown in FIG. 5B, the second wiring layer 21 and the third wiring layer 31 need to be formed in separate steps. In the case of this modification, the second wiring layer 21 and the third wiring layer are required. It is possible to form the layer 31 simultaneously in the same process. That is, an additional effect that the formation of the wiring becomes easy can be obtained.

  FIG. 12 is a YZ side view showing another modification. The magnetoresistive effect element 1b according to this modification has a fourth stacked structure 40 in addition to the third stacked structure 30 in the second region R2. The fourth stacked structure 40 includes a fourth wiring layer 41, a fourth antiferromagnetic layer 42, a fourth magnetization fixed layer 43, a fourth tunnel barrier layer 44, and a fourth magnetization free layer 45. The fourth stacked structure 40 is simultaneously formed in the same process as the process of forming the first stacked structure 10. The fourth stacked structure 40 does not contribute to data writing and data reading.

  According to the structure shown in FIG. 12, the intermediate wiring layer 50 is sandwiched between the third magnetization free layer 35 and the fourth magnetization free layer 45 in the second region R2. That is, the third magnetization free layer 35 and the fourth magnetization free layer 45 are magnetically coupled via the intermediate wiring layer 50. The magnetization of the third magnetization free layer 35 and the magnetization of the fourth magnetization free layer 45 are opposite to each other. Since the magnetization of the third magnetization free layer 35 and the magnetization of the fourth magnetization free layer 45 cancel each other, the influence of these magnetizations on other regions is further reduced compared to the case of FIG.

1-5. Circuit Configuration FIG. 13 is a circuit diagram showing an example of the configuration of the MRAM according to the present embodiment. The MRAM includes a plurality of magnetic memory cells 1 arranged in an array. Each magnetic memory cell 1 includes the magnetoresistive effect element according to the present embodiment. The first wiring layer 11 is connected to the word line WL2, and the second wiring layer 21 is connected to the word line WL1. The third wiring layer 31 is connected to the bit line BL. The plurality of word lines WL1 are connected to the first word driver 2. The plurality of word lines WL2 are connected to the second word driver 3. The plurality of bit lines BL are connected to the bit driver 4.

  At the time of data writing, the first word driver 2 and the bit driver 4 select the word line WL1 and the bit line BL connected to the target cell. As a result, write currents IW1 and IW2 flow between the second wiring layer 21 and the third wiring layer 31 of the target cell. When reading data, the second word driver 3 and the bit driver 4 select the word line WL2 and the bit line BL connected to the target cell. As a result, a read current IR flows between the first wiring layer 11 and the third wiring layer 31 of the target cell.

2. Second Embodiment In the second embodiment of the present invention, another three-terminal magnetoresistive element is proposed. Each magnetic memory cell of the MRAM according to the second embodiment includes the following magnetoresistive effect element.

2-1. Structure FIG. 14 is an XZ side view showing the configuration of the magnetoresistive effect element (magnetic memory cell) according to the second embodiment. The magnetoresistive effect element according to the present embodiment includes a reading unit 60, a first writing unit 70, a second writing unit 80, and a magnetization free layer 90. The magnetization free layer 90 is formed on the reading unit 60. Each of the first writing unit 70 and the second writing unit 80 is formed on the magnetization free layer 90 in the first region R1 and the second region R2.

  The magnetization easy axis of the magnetization free layer 90 is along the X direction. The magnetization of the magnetization free layer 90 can be reversed, and is allowed to face in the + X direction or the −X direction. The magnetic anisotropy of the magnetization free layer 90 is determined by any one of a crystal magnetic anisotropy depending on a material, a strain induction anisotropy, a shape magnetic anisotropy depending on a planar shape, or a combination thereof. .

  The reading unit 60 includes a first wiring layer 61, a first antiferromagnetic layer 62, a first magnetization fixed layer 63, and a first tunnel barrier layer 64. Among these, the first tunnel barrier layer 64 is in contact with the magnetization free layer 90. The magnetization of the first magnetization fixed layer 63 is fixed in the −X direction by the first antiferromagnetic layer 62. The first magnetization fixed layer 63 is connected to the magnetization free layer 90 via the first tunnel barrier layer 64, thereby forming a “read MTJ”.

  The first writing unit 70 is provided in the first region R1. The first writing unit 70 includes a second wiring layer 71, a second antiferromagnetic layer 72, a second magnetization fixed layer 73, and a second tunnel barrier layer 74. Among these, the second tunnel barrier layer 74 is in contact with the magnetization free layer 90. The magnetization of the second magnetization fixed layer 73 is fixed in the −X direction by the second antiferromagnetic layer 72. The second magnetization fixed layer 73 is connected to the magnetization free layer 90 via the second tunnel barrier layer 74, thereby forming the “first write MTJ”.

  The second writing unit 80 is provided in the second region R2. The second writing unit 80 includes a third wiring layer 81, a third antiferromagnetic layer 82, a third magnetization fixed layer 83, and a third tunnel barrier layer 84. Among these, the third tunnel barrier layer 84 is in contact with the magnetization free layer 90. The magnetization of the third magnetization fixed layer 83 is fixed in the + X direction opposite to the second magnetization fixed layer 73 by the third antiferromagnetic layer 82. The third magnetization fixed layer 83 is connected to the magnetization free layer 90 via the third tunnel barrier layer 84, thereby forming the “second write MTJ”.

  Each of the magnetization fixed layers 63, 73, 83, and the magnetization free layer 90 may have a stacked structure in which a plurality of ferromagnetic layers are magnetically coupled via a nonmagnetic layer. Further, the arrangement of the reading unit 60 is not limited to that shown in FIG. For example, as illustrated in FIG. 15, the reading unit 60 may be formed from the first region R1 to the second region R2.

The material of each layer is, for example, as follows. The wiring layers 61, 71, 81 are formed of a metal such as Al or Cu. The antiferromagnetic layers 62, 72, and 82 are formed of FeMn, IrMn, PtMn, or the like. The ferromagnetic layers in the magnetization fixed layers 63, 73, and 83 and the magnetization free layer 90 contain at least one element selected from Co, Fe, and Ni. For example, the ferromagnetic layers of the magnetization fixed layers 63, 73, 83 and the magnetization free layer 90 are formed of CoFe, NiFe, NiFeCo, CoFeB, or the like. Examples of the tunnel barrier layers 64, 74, and 84 that are nonmagnetic layers include insulating films such as Al ₂ O ₃ films, SiO ₂ films, MgO films, and AlN films. The tunnel barrier layers (74, 84) used in data writing described later may be nonmagnetic metal layers such as Cu.

2-2. Operation (data writing)
For data writing, the first writing unit 70 and the second writing unit 80 are used. At the time of data writing, the write current IW flows between the second wiring layer 71 and the third wiring layer 81. The magnetization fixed layer 73 of the first writing unit 70 and the magnetization fixed layer 83 of the second writing unit 80 have fixed magnetizations in opposite directions, and supply sources for supplying spin-polarized electrons in opposite directions. Function.

  Consider a case where the magnetization direction of the magnetization free layer 90 is the + X direction. When it is desired to reverse the magnetization direction in the −X direction, the write current IW is passed from the third wiring layer 81 to the second wiring layer 71. At this time, the electrons move from the second magnetization fixed layer 73 to the magnetization free layer 90 and also move from the magnetization free layer 90 to the third magnetization fixed layer 83. Specifically, in the first region R1, electrons having a spin in the −X direction are injected from the second magnetization fixed layer 73 into the magnetization free layer 90. On the other hand, in the second region R2, electrons having a spin in the −X direction are reflected by the third magnetization fixed layer 83 as a spin filter, and electrons having a spin in the + X direction are reflected from the magnetization free layer 90 to the third magnetization fixed layer 83. Move to. As a result of the spin transfer between the magnetization free layer 90 and the magnetization fixed layers 73 and 83, the magnetization of the magnetization free layer 90 is reversed from the + X direction to the −X direction.

  Next, consider a case where the magnetization direction of the magnetization free layer 90 is the −X direction. When it is desired to reverse the magnetization direction in the + X direction, the write current IW is passed from the second wiring layer 71 to the third wiring layer 81. At this time, electrons move from the third magnetization fixed layer 83 to the magnetization free layer 90 and also move from the magnetization free layer 90 to the second magnetization fixed layer 73. Specifically, in the second region R2, electrons having a spin in the + X direction are injected from the third magnetization fixed layer 83 into the magnetization free layer 90. On the other hand, in the first region R1, electrons having a spin in the + X direction are reflected by the second magnetization fixed layer 73 as a spin filter, and electrons having a spin in the −X direction are reflected from the magnetization free layer 90 to the second magnetization fixed layer 73. Move to. As a result of the spin transfer between the magnetization free layer 90 and the magnetization fixed layers 73 and 83, the magnetization of the magnetization free layer 90 is reversed from the −X direction to the + X direction.

  Thus, according to the present embodiment, spin transfer that promotes magnetization reversal occurs in both the first region R1 and the second region R2. This is because the magnetization of the second magnetization fixed layer 73 and the magnetization of the third magnetization fixed layer 83 are fixed in opposite directions. Since spin transfer that promotes magnetization reversal occurs in both the first region R1 and the second region R2, the magnetization of the magnetization free layer 90 is easily reversed as a whole. That is, the write current IW can be made smaller than before.

(Data read)
A reading unit 60 is used for reading data. At the time of data reading, the read current IR flows from the second and third wiring layers 71 and 81 to the first wiring layer 61 or from the first wiring layer 61 to the second and third wiring layers 71 and 81. . Thereby, the resistance value of the read MTJ can be detected. For example, the magnitude of the resistance value of the read MTJ can be detected by comparing a voltage corresponding to the read current IR with a predetermined reference voltage. As a result, it is possible to sense whether the data stored in the magnetoresistive element (magnetic memory cell) is “0” or “1”.

  As described above, according to the present embodiment, the read MTJ formed by the read unit 60 is used for data read, and the write MTJ formed by the write units 70 and 80 is used for data write. That is, data writing and data reading are realized by separate current paths. Therefore, deterioration of the tunnel barrier layers 64, 74, 84 is suppressed. In addition, erroneous writing during data reading can be prevented. Further, since the write characteristic and the read characteristic can be designed separately, the write characteristic and the read characteristic can be optimized.

1 Magnetoresistive element (magnetic memory cell)
2 1st word driver 3 2nd word driver 4 Bit driver 10 1st laminated structure 11 1st wiring layer 12 1st antiferromagnetic layer 13 1st magnetization fixed layer 14 1st tunnel barrier layer 15 1st magnetization free layer 20 1st 2 laminated structure 21 2nd wiring layer 22 2nd antiferromagnetic layer 23 2nd magnetization fixed layer 24 2nd tunnel barrier layer 25 2nd magnetization free layer 30 3rd laminated structure 31 3rd wiring layer 32 3rd antiferromagnetic layer 33 3rd magnetization fixed layer 34 3rd tunnel barrier layer 35 3rd magnetization free layer 40 4th laminated structure 41 4th wiring layer 42 4th antiferromagnetic layer 43 4th magnetization fixed layer 44 4th tunnel barrier layer 45 4th Magnetization free layer 50 Intermediate wiring layer 60 Reading unit 61 First wiring layer 62 First antiferromagnetic layer 63 First magnetization fixed layer 64 First tunnel barrier layer 70 First writing unit 71 Second wiring 72 Second antiferromagnetic layer 73 Second magnetization fixed layer 74 Second tunnel barrier layer 80 Second writing unit 81 Third wiring layer 82 Third antiferromagnetic layer 83 Third magnetization fixed layer 84 Third tunnel barrier layer 90 Magnetization Free layer MF1 First inversion magnetization MF2 Second inversion magnetization MP1 First fixed magnetization MP2 Second fixed magnetization

Claims (3)

A spin-injection magnetoresistive element,
A first write magnetization fixed layer whose magnetization direction is fixed in the first direction;
A second write magnetization fixed layer whose magnetization direction is fixed in a second direction opposite to the first direction;
A magnetization free layer whose easy axis direction is parallel to the first direction and the second direction,
The first write magnetization fixed layer is connected to the magnetization free layer via a first write nonmagnetic layer in the first region,
The second write magnetization fixed layer is connected to the magnetization free layer via a second write nonmagnetic layer in a second region away from the first region in the easy axis direction,
When writing data, a write current is passed between the first write magnetization fixed layer and the second write magnetization fixed layer through the magnetization free layer. The magnetoresistive element according to claim 1,
A read magnetization pinned layer having a magnetization direction fixed in the first direction and connected to the magnetization free layer via a read nonmagnetic layer;
When reading data, a read current is passed between the magnetization free layer and the read magnetization fixed layer. Comprising a plurality of magnetic memory cells arranged in an array;
Each of the plurality of magnetic memory cells is an MRAM having the magnetoresistive effect element according to claim 1.

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