JP4876572B2 - Magnetic memory - Google Patents

Description

  The present invention relates to a magnetic memory.

  Currently, volatile memories such as DRAMs and SRAMs are used as general-purpose memories used in information processing apparatuses such as computers and communication devices. However, in a volatile memory such as a DRAM, it is necessary to continuously supply a current, for example, to refresh the memory, and when the power is turned off, all information is lost. For this reason, it is necessary to provide a means for storing information, that is, a non-volatile memory, and flash EEPROMs and hard disk devices are currently used. In these nonvolatile memories, speeding up access is an important issue as information processing speeds up.

  However, these nonvolatile memories are still insufficient in terms of access speed, reliability, power consumption, and the like.

  In addition, with the rapid spread of portable information devices and higher performance, information devices aiming at so-called ubiquitous computing that can perform information processing anywhere at any time are being rapidly developed. As a key device in the development of such a device, development of a reliable, high-speed, large-capacity nonvolatile memory is strongly demanded.

  As an effective technique for increasing the speed of the nonvolatile memory, there is an MRAM (Magnetic Random Access Memory) in which magnetic thin film elements that store information according to the direction of magnetization along the easy axis of the ferromagnetic layer are arranged in a matrix. Promising. In the MRAM, information is stored according to the magnetization directions of two ferromagnetic materials. The magnetization reversal speed of a minute ferromagnet is said to be 2 nsec or less, and there is a possibility as a high speed memory. In reading the stored information, a change in resistance depending on whether the magnetization direction of the magnetosensitive layer is parallel or antiparallel to the reference magnetization direction is detected as a change in current or voltage.

  Some MRAMs use a giant magnetoresistance (GMR) effect. As an MRAM using the GMR effect, the one disclosed in Patent Document 1 is known. The GMR effect is a phenomenon in which the resistance value is minimized when the magnetization directions of two magnetic layers parallel to the easy axis of magnetization are parallel and maximized when the magnetization directions are antiparallel. MRAM using the GMR effect is a pseudo spin valve type for writing / reading information by utilizing the difference in coercive force of two ferromagnets, antiferromagnetic coupling with an antiferromagnetic layer across a nonmagnetic layer There is a Spin Valve type having a free layer in which the magnetization direction is fixed by the fixed layer and the magnetization direction is changed by an external magnetic field.

  In the MRAM using the GMR effect, a change in resistance value is read by a change in current value or voltage value. In any case, in order to write information, a method of reversing the magnetization direction of the magnetic layer by an induced magnetic field (current magnetic field) due to a current flowing through the wiring is used.

  In order to further improve resistance change in GMR, an MRAM using a ferromagnetic tunnel (TMR) effect has been proposed. The TMR effect is a phenomenon in which a tunnel current flowing through an insulating layer changes depending on the relative angle of the magnetization direction between two ferromagnetic layers sandwiching a thin insulating layer. The resistance value is minimized when the magnetization directions are parallel, and is maximized when the magnetization directions are antiparallel. TMR, for example, has a large resistance change rate of 40% or more in CoFe / Al oxide / CoFe and has a high resistance value, and therefore impedance matching when combined with a semiconductor device such as a MOS-FET can be easily obtained. Therefore, it is easy to increase the output as compared with GMR, and improvement in storage capacity and access speed is expected. The MRAM using the TMR effect is described in Patent Document 2 and Patent Document 3.

  In the MRAM using the TMR effect, a method of storing information by changing the magnetization direction of the magnetic film in a predetermined direction by the current magnetic field of the wiring is employed. In order to read the stored information, a method of reading information by passing a current in a direction perpendicular to the insulating layer and detecting a change in the resistance value of the thin film magnetic element is employed.

Many MRAMs have a structure in which TMR elements are arranged at intersections between bit lines and word lines wired in a lattice pattern. A normal TMR element has a three-layer structure of a ferromagnetic layer / nonmagnetic insulating layer / ferromagnetic layer having a nonmagnetic layer between two ferromagnetic layers. The ferromagnetic layer is usually made of a transition metal magnetic element (Fe, Co, Ni) or an alloy of transition metal magnetic elements (CoFe, CoFeNi, NiFe, etc.) having a thickness of 10 nm or less, and the nonmagnetic insulating layer is made of Al ₂ O. ₃ and MgO.

  One ferromagnetic layer (fixed layer) constituting the TMR element has a fixed magnetization direction, and the other ferromagnetic layer (magnetic sensitive layer or free layer) rotates in accordance with an external magnetic field. . As the structure of the fixed layer, an exchange coupling type in which an antiferromagnetic layer (FeMn, IrMn, PtMn, NiMn, etc.) is provided to one ferromagnetic layer is often used.

  “1” and “0” of the memory information depend on the state of the magnetization directions of the two ferromagnetic materials constituting the TMR element, that is, whether the magnetization directions are parallel or antiparallel. It is prescribed as When the magnetization directions of these two ferromagnets are antiparallel, the electric resistance value in the thickness direction is larger than when the magnetization directions are parallel.

  Therefore, reading of information of “1” and “0” is performed by passing a current in the thickness direction of the TMR element and measuring the resistance value or current value of the TMR element due to the MR (magnetoresistive) effect.

  The writing of information of “1” and “0” is performed by rotating the magnetization direction of the magnetosensitive layer of the TMR element by the action of a magnetic field formed by passing a current through a wiring arranged in the vicinity of the TMR element. This has been done in the past.

  When a high-density memory is realized by high integration of the element, the demagnetizing field increases due to the reduction in the ratio of the length and thickness of the magnetic layer as the magnetoresistive element is miniaturized, thereby increasing the magnetization of the magnetic material. The strength of the magnetic field for changing the direction increases, and a large write current is required.

  In order to reduce the write current, in the write operation for changing the magnetization direction of the magnetosensitive layer so as to correspond to information “1” and “0”, in addition to the magnetization reversal method by applying a magnetic field to the magnetic material, the spin polarization Spin injection magnetization reversal using spin transfer torque by pole current is known.

  As a method of reading information, generally, a read selection transistor is provided in each cell, and only the read transistor of the selected cell is made conductive to read the resistance of the magnetoresistive effect element of the selected cell.

  The spin transfer torque is a torque for changing the magnetization direction of the other ferromagnetic material when a current is passed from one ferromagnetic material to the other ferromagnetic material via the nonmagnetic layer. Therefore, by controlling the spin direction of the injection current, it is possible to change the magnetization direction of the other magnetic material.

  For example, when a current is passed in a direction perpendicular to the film surface of a laminate composed of a small ferromagnetic layer / nonmagnetic layer / ferromagnetic layer, magnetization reversal of the ferromagnetic material occurs. This phenomenon is called spin-injection magnetization reversal, and the energy state of up-spin (up spin) and down-spin (down spin) electrons is different at the interface between the ferromagnetic layer and the nonmagnetic layer. Spin transmittance and reflectivity of spin and down spin electrons are different and spin polarization current flows.

  The spin-polarized electrons of the spin-polarized current that have flowed into the ferromagnetic layer interact with the electrons in the ferromagnetic layer to generate torque between the electrons, resulting in magnetization reversal. This is different from magnetization reversal due to an open current magnetic field, because magnetization reversal occurs due to the current inside the magnetic material, so the influence on adjacent cells is small, and the write current is unlikely to increase with the miniaturization of the element, and conversely Thus, the write current can be reduced. Therefore, a high-density magnetic memory can be realized by using spin injection magnetization reversal as a method of recording information.

  Methods for changing the magnetization direction of a ferromagnetic material using spin transfer torque include (I) a relaxation switching method, (II) a precession switching method, and (III) a relaxation precession. A switch (Relaxing-Precisional Switching) method and the like are known.

  In the relaxation switch method, the magnetization direction of the magnetosensitive layer is controlled by the spin transfer torque from the fixed layer, but the magnetization direction of the fixed layer is in the film plane and parallel to the easy axis of magnetization of the magnetosensitive layer. . Therefore, when the magnetization direction of the magnetosensitive layer is reversed, in the initial stage of the reversal, the spin transfer torque competes with Spin Relaxing which attempts to direct the magnetization in the effective magnetic field direction. In addition, at the initial stage of reversal in which the magnetization direction of the fixed layer and the magnetization direction of the magnetosensitive layer are nearly parallel, the spin transfer torque is small, so that it takes time for the reversal. That is, in the relaxation switch method, since the direction of magnetization is gradually changed to an equilibrium state against these forces, a large current is required to reverse the direction of magnetization. The magnitude of the spin transfer torque necessary for the magnetization reversal is proportional to the Gilbert attenuation constant included in the LLG (Landau-Lifshitz-Gilbert) equation.

  In the precession switch method, the magnetization direction of the magnetosensitive layer is controlled by the spin transfer torque from the fixed layer, but the magnetization direction of the fixed layer is perpendicular to the film surface, and the magnetization of the magnetosensitive layer is It is perpendicular to the easy axis. Due to the spin transfer torque, the magnetization direction of the magnetosensitive layer has a component perpendicular to the film surface, and the demagnetizing field starts to rotate in the in-film direction. Since the spin transfer torque is constant even if the magnetization of the magnetosensitive layer rotates in the plane, the magnetization reversal is possible in a short time. However, since the spin transfer torque acts as long as a current flows even after the magnetization reversal of the magnetosensitive layer, the magnetization of the magnetosensitive layer is reinverted depending on the current application time. Therefore, this method requires very precise current time control.

  The relaxed precession switch method considered there is an application of an external magnetic field in the hard axis direction of the magnetosensitive layer in the precession switch method. In this case, precise time control of the current required by the precession switch method is not required, but precise control of the spin transfer torque is required.

Such a magnetic memory is described in Non-Patent Document 1 and Non-Patent Document 2, for example.
US Pat. No. 5,343,422 US Pat. No. 5,629,92 Japanese Patent Laid-Open No. 9-91949 W. C. Jeong, J.A. H. Park, J.M. H. Oh, G. T.A. Jeong, H.C. S. Jeong and Kinam Kim, "Highly scalable MRAM using filled assisted current induced switching", Symposium on VLSI Technology Digest Tech. 184-185, 2005 Hiroshi Morise and Shiho Nakamura “Abstracts of the 29th Annual Meeting of the Magnetic Society of Japan”, P183, 2005

  However, in order to increase the density of the conventional magnetic memory, it is necessary to reduce the current required for the magnetization reversal of the magnetosensitive layer in proportion to the size of the magnetoresistive element. In this case, since the magnetization reversal threshold value of the magnetoresistive effect element is lowered, there is a possibility that unintended magnetization reversal may occur due to the influence of an unnecessary external magnetic field, and an error occurs in stored data.

  The present invention has been made in view of such a problem, and an object thereof is to provide a magnetic memory capable of suppressing unintended magnetization reversal.

In order to solve the above-described problem, a magnetic memory according to the present invention is a magnetic memory in which a plurality of storage areas are arranged. Each storage area includes a first wiring, a second wiring, a first wiring, and a first wiring. A magnetoresistive element disposed on the reference plane and disposed between the two wirings and electrically connected to the first wiring and the second wiring, and a magnetosensitive layer of the magnetoresistive effect element by spin injection. The thickness direction of the magnetoresistive effect element is covered so as to cover the spin filter provided in the magnetoresistive effect element, the portion on the reference plane of the first wiring and the second wiring, and the magnetoresistive effect element so that the direction of magnetization changes. A magnetic yoke that surrounds the periphery of the magnetoresistive element , and the first wiring and the second wiring each flow through the first wiring and the second wiring when reading information. The direction of the read current is the same, Each magnetic field around the wiring and the second wiring is arranged so as to cancel out in the magnetosensitive layer of the magnetoresistive effect element, and the first wiring and the second wiring are the first wiring when information is written. And the direction of each current flowing through the second wiring is opposite, and both magnetic fields around the first wiring and the second wiring assist the force to change the magnetization direction of the magnetosensitive layer by spin injection. The first and second wirings each have a vertical wiring extending perpendicularly to the reference plane, a semiconductor substrate having a circuit element to which the vertical wiring is connected, a semiconductor substrate, And a magnetic layer interposed between the magnetoresistive effect element, and each vertical wiring is connected to the circuit element through a through hole provided in the magnetic layer.

  According to this magnetic memory, the magnetic yoke covers the portion on the reference plane of the first wiring and the second wiring and the magnetoresistive effect element, and is positioned in all directions perpendicular to the thickness direction of the magnetoresistive effect element. Therefore, the introduction of an external magnetic field to the magnetoresistive element, the first wiring and the second wiring on the reference surface is suppressed. Therefore, unintended magnetization reversal of the magnetosensitive layer in the magnetoresistive effect element can be suppressed.

  It is desirable that the first and second wirings each have a vertical wiring extending perpendicular to the reference plane. Since the first and second wirings pass through in the vertical direction and are connected to an external circuit, the magnetic yoke can be surrounded by the magnetic yoke.

  The magnetic memory of the present invention preferably includes a semiconductor substrate having a circuit element to which a vertical wiring is connected, and a magnetic layer interposed between the semiconductor substrate and the magnetoresistive element. In this case, the magnetic layer introduced into the magnetoresistive effect element from the semiconductor substrate on which the circuit element is formed can be blocked by the magnetic layer.

Such an external magnetic field shield structure is particularly effective in a high-density magnetic memory. In other words, the area of the magnetosensitive layer is preferably 0.01 μm ² or less.

  According to the present invention, a magnetic memory capable of reducing the amount of current required for magnetization reversal can be provided.

  Hereinafter, the magnetic memory according to the embodiment will be described. Note that the same reference numerals are used for the same elements, and redundant description is omitted. The magnetic memory according to the embodiment is formed by arranging a plurality of storage areas P (X, Y) in X columns and Y rows, and each storage area P (X, Y) includes a magnetoresistive element 5.

  FIG. 1 is a perspective view of one storage area P (X, Y).

  Each storage area P (X, Y) is disposed between the first wiring 6, the second wiring 7, the midway position 6 a of the first wiring 6, and the second wiring 7, and the first wiring 6. The magnetoresistive effect element 5 electrically connected to the intermediate position 6a and the second wiring 7 and the magnetoresistive effect element 5 so that the magnetization direction of the magnetosensitive layer in the magnetoresistive effect element 5 is changed by spin injection. And a provided spin filter FL.

  The first wiring 6 extends along the X axis, and the second wiring 7 also extends along the X axis. The width direction of each wiring 6 and 7 is parallel to the Y axis, and the thickness direction is parallel to the Z axis.

  When a current is passed between the middle position 6a of the first wiring 6 and the second wiring 7, magnetic fields E6 and E7 are generated so as to surround both the wirings 6 and 7, respectively. That is, the magnetic fields E6 and E7 are generated so as to surround the X axis, and the direction thereof is substantially parallel to the Y axis at the position of the magnetosensitive layer in the magnetoresistive effect element 5.

  Both ends of the first wiring 6 are connected to the terminal VW and the terminal VR, respectively, one end of the second wiring 7 is connected to the terminal VC, and the other end is connected to the lower surface of the magnetoresistive element 5. A switch (field effect transistor: circuit element) QR is interposed between one end of the second wiring 7 and the terminal VC.

  When reading information, the information writing terminal VW is opened.

When the potential of the terminal VC is made relatively high with respect to the potential of the read terminal VR while the write terminal VW is opened, and the switch QR is turned on, the magnetoresistive effect element 5 is connected from the terminal VC of the second wiring 7. Thus, an information read current _IR1 flows to the read terminal VR of the first wiring 6, and a magnetic field E6 and a magnetic field E7 in the same rotation direction are generated. The magnetic field E6 and the magnetic field E7 at the time of reading information are both clockwise in the direction of traveling in the positive direction of the X axis. Therefore, the magnetic fields E6 and E7 at the position of the magnetoresistive effect element 5 located between these wirings cancel each other. The magnetic fields E6 and E7 pass through the magnetic yoke. Such a magnetic yoke surrounds the longitudinal direction of the first and / or second wirings 6 and 7 and has an end portion located on an extension line in a direction perpendicular to the thickness direction of the magnetosensitive layer 2. When a current flows through the first and / or second wirings 6 and 7, magnetic lines generated so as to surround the wirings pass through the magnetic yoke and are guided into the magnetosensitive layer from the ends thereof.

On the other hand, when the write terminal VW is opened and the potential of the terminal VC is made relatively low with respect to the potential of the read terminal VR and the switch QR is turned on, the read terminal VR of the first wiring 6 is magnetically connected. An information read current _IR2 flows to the terminal VC of the second wiring 7 through the resistance effect element 5, and a magnetic field E6 and a magnetic field E7 in the same rotation direction are generated. The magnetic field E6 and the magnetic field E7 at the time of reading information are both clockwise in the direction of traveling in the negative direction of the X axis. Therefore, the magnetic fields E6 and E7 at the position of the magnetoresistive effect element 5 located between these wirings cancel each other.

As described above, when reading information, the directions of the read currents I _R1 and I _R2 flowing through the first wiring 6 and the second wiring 7 are the same, and the magnetic fields E6 and E6 around the first wiring 6 and the second wiring 7 are used. E7 is disposed so as to cancel out in the magnetosensitive layer of the magnetoresistive element 5. At the time of reading information, since both magnetic fields E6 and E7 cancel each other, the force to change the magnetization direction of the magnetosensitive layer is weakened. Therefore, even if noise is mixed or the read current increases, Magnetization reversal does not occur, and the reliability of the magnetic memory can be improved.

Conversely, when information is written, the information reading terminal VR is opened. When the read terminal VR is opened and the potential of the terminal VC is made relatively high with respect to the potential of the write terminal VW and the switch QR is turned on, the magnetoresistive effect element 5 is connected from the terminal VC of the second wiring 7. Thus, the information write current _IW0 flows to the write terminal VW of the first wiring 6 to generate a magnetic field E6 and a magnetic field E7 in the reverse rotation direction. At this time, the magnetic field E6 at the time of writing information is clockwise in the direction of traveling in the negative X-axis direction, and the magnetic field E7 is clockwise in the direction of traveling in the positive X-axis direction. Therefore, a direction magnetic field in the negative Y-axis direction acts on the magnetoresistive effect element 5 located between these wirings.

On the other hand, when the read terminal VR is opened, the potential of the terminal VC is relatively lowered with respect to the potential of the write terminal VW, and the switch QR is turned on, the magnetic force is applied from the write terminal VW of the first wiring 6 to the magnetic field. An information write current _IW1 flows to the terminal VC of the second wiring 7 through the resistance effect element 5, and a magnetic field E6 and a magnetic field E7 in the reverse rotation direction are generated. At this time, the magnetic field E6 at the time of writing information is clockwise in the direction of traveling in the positive direction of the X axis, and the magnetic field E7 is clockwise in the direction of traveling in the negative direction of the X axis. Therefore, a direction magnetic field in the positive direction of the Y-axis acts on the magnetoresistive effect element 5 located between these wirings.

Here, when writing information, the first wiring 6 and the second wiring 7 have the currents I _W0 and I _W1 flowing through the first wiring 6 and the second wiring 7 in opposite directions, and the first wiring 6 and the second wiring 7 Both of the magnetic fields E6 and E7 around the second wiring 7 are arranged to assist a force (spin transfer torque) for changing the magnetization direction of the magnetosensitive layer by spin injection. The specific polarized spin is transmitted or reflected through the spin filter FL and injected into the magnetosensitive layer to generate a spin transfer torque. Therefore, at the time of writing information, in addition to the force for changing the direction of magnetization at the time of spin injection, the magnetosensitive layer is assisted by the assisting force of the magnetic fields E6 and E7 caused by the current flowing through the first wiring 6 and the second wiring 7. The magnetization direction is easily changed.

In the magnetoresistive effect element accompanied by the spin injection magnetization reversal, the magnetization direction of the ferromagnetic material is reversed by passing a current in a direction perpendicular to the film surface of the laminated body including the ferromagnetic material. A spin-polarized current flows due to the difference in transmittance between up-spin electrons and down-spin electrons at the interface between the ferromagnetic layer and the nonmagnetic layer. The spin-polarized electrons of the spin-polarized current that have flowed into the ferromagnetic layer interact with the electrons in the ferromagnetic layer to generate torque between the electrons, resulting in magnetization reversal. The direction of magnetization reversal of the ferromagnetic layer is determined by the direction of the write currents I _W0 and I _W1 that flow through the stack. Therefore, the parallel / antiparallel magnetization direction of the ferromagnetic material can be controlled by the direction of the current, and information can be recorded.

  FIG. 2 is a longitudinal sectional view of the magnetoresistive element 5 (when the magnetization direction is parallel) (a), and a longitudinal sectional view of the magnetoresistive element 5 (when the magnetization direction is antiparallel) (b).

  The magnetoresistive element 5 has a structure in which an insulating layer 3 constituting a tunnel barrier layer is sandwiched between a magnetosensitive layer 2 and a fixed layer 4. The fixed layer 4 includes a ferromagnetic layer 4a and an antiferromagnetic layer 4b joined to the ferromagnetic layer 4a in order to fix the magnetization direction. The magnetoresistive element 5 constitutes a TMR element. Yes. That is, the magnetoresistive effect element 5 is a TMR element including the insulating layer 3 between the magnetosensitive layer 2 and the (first) fixed layer 4. The TMR element utilizes a phenomenon in which the proportion of electrons passing through the insulating layer 3 as a tunnel barrier layer during reading differs according to the difference between the stored magnetization direction of the magnetosensitive layer 2 and the magnetization direction of the fixed layer 4. It is an element and can detect stored information with high sensitivity.

  The spin filter FL shown in FIG. 1 is formed by bonding a fixed layer and a nonmagnetic layer, and this nonmagnetic layer is bonded to the magnetosensitive layer 2. Since electrons that have passed through the spin filter FL are introduced into the TMR element, information writing / reading is performed according to whether the magnetization direction of the magnetosensitive layer 2 and the magnetization direction of the fixed layer 4 are parallel or antiparallel. Can do.

“1” and “0” of the memory information correspond to the state of magnetization directions of the fixed layer 4 and the magnetosensitive layer 2 constituting the TMR element, that is, whether the magnetization directions are parallel (FIG. 2A )), Or depending on whether they are anti-parallel (FIG. 2B). When the magnetization directions of the fixed layer 4 and the magnetosensitive layer 2 are antiparallel (FIG. 2B), the value of the electric resistance R in the thickness direction is larger than when the magnetization directions are parallel (FIG. 2A). Is big. In other words, the resistance R when parallel is equal to or less than the threshold value _R0 , and the resistance R when antiparallel is larger than the threshold value _R0 . Therefore, when reading the information of “1” and “0”, the current I _R (I _R1 or I _R2 ) flows in the thickness direction of the TMR element, and the resistance value or current value of the TMR element due to the MR (magnetoresistance) effect is obtained. This is done by measuring. For example, the low resistance parallel state is “0” and the high resistance anti-parallel state is “1”.

  In addition, if it supplementarily demonstrates about the magnetic fields E6 and E7 shown in FIG. 1, the magnetic fields E6 and E7 which generate | occur | produce by flowing through the 1st wiring 6 and the 2nd wiring 7 will generate | occur | produce in substantially the same plane (YZ plane). However, strictly speaking, they are displaced along the longitudinal direction (X axis) of the wiring. That is, the cancellation of the magnetic field in the magnetosensitive layer 2 is not complete.

  In this example, the storage section of each storage area P (X, Y) includes the magnetic yoke 8 surrounding the magnetoresistive effect element 5, so that each magnetic field E 6 generated by flowing through each wiring 6, 7. E7 is drawn into the magnetic yoke 8 (see FIG. 4), and concentrates on the magnetoresistive effect element 5 including the magnetosensitive layer 2 to give magnetic fields E6 and E7. That is, the magnetic fields E6 and E7 in the magnetosensitive layer 2 at the time of reading information are close to each other, and the cancellation is efficiently performed. In the spin-injection type magnetic memory using the above-mentioned magnetic field assist, the magnetic field E6 and E7 in the magnetosensitive layer 2 are brought close to each other and the combined magnetic field strength is increased by using a magnetic yoke when writing information. Thus, the write current can be significantly reduced.

The threshold of the write current required for the spin injection magnetization reversal without the magnetic field assist is 5 × 10 ⁷ A / cm ² , but when the magnetic field assist is used simultaneously with the spin injection, the write current required for the spin injection magnetization reversal is The threshold value was 2.5 × 10 ⁷ A / cm ² . When a magnetic yoke having a U-shaped cross section and having an open portion perpendicular to the longitudinal direction of the wirings 6 and 7 is used, the threshold value of the write current required for spin injection magnetization reversal is 5 × 10 ⁶ A / cm. ² That is, the magnitude of the write current of the spin injection magnetization reversal type magnetic memory using the magnetic yoke and the magnetic field assist is 1/10 of the write current without the magnetic field assist, and there is no magnetic yoke with the magnetic field assist. It was possible to reduce to 1/5 of the write current.

  FIG. 3 is a diagram showing a longitudinal cross-sectional configuration of the main part of the element including the magnetoresistive effect element 5.

  The main part of the element is composed of a TMR element composed of a ferromagnetic layer 4a, an insulating layer 3 and a magnetosensitive layer 2 laminated on an antiferromagnetic layer 4b, and a nonmagnetic conductive layer 41 and a fixed layer 40 laminated on the TMR element. The spin filter FL is provided. The magnetization directions of the fixed layers 4 and 41 are parallel to the Y axis.

  The first wiring 6 and the second wiring 7 described above are in the direction (X) perpendicular to both the magnetization direction (Y axis) and the thickness direction (Z axis) of the fixed layer 4 at the position of the magnetoresistive element 5. (Shaft). Since the direction surrounding the longitudinal direction (X-axis) of the first wiring 6 and the second wiring 7 coincides with the magnetization direction of the fixed layer 4 at the position of the magnetosensitive layer 2, the first wiring 6 and the second wiring 7 are written during information writing. When power is applied to the two wirings 7, it is possible to assist effectively in changing the magnetization direction.

  The spin filter FL includes a nonmagnetic conductive layer 41 provided on the magnetosensitive layer 2 and a (second) fixed layer 40 in contact with the nonmagnetic conductive layer 41. The magnetization of the second fixed layer 40 The direction of the easy axis (Y axis) is parallel to the direction of the easy axis of magnetization (Y axis) of the (first) pinned layer 4. Therefore, when electrons are injected into the magnetosensitive layer 2, a spin-polarized current whose spin is polarized in a specific direction is injected into the magnetosensitive layer 2, and magnetization is caused by interaction with electrons in the magnetosensitive layer 2. Invert.

  As the material of the magnetosensitive layer 2, ferromagnetic materials such as Co, CoFe, NiFe, NiFeCo, CoPt, and CoFeB can be used. The magnetosensitive layer 2 can change the magnetization direction by a current flowing perpendicularly to the film surface from the wiring layer, and the smaller the area of the magnetosensitive layer 2 is, the smaller the current (threshold of current) required for magnetization reversal is. be able to.

The external magnetic field shield structure using the magnetic yoke is particularly effective for a high-density magnetic memory. From the viewpoint of increasing the density of the magnetic memory, the area of the magnetosensitive layer 2 is preferably 0.01 μm ² or less. If the area of the magnetosensitive layer 2 exceeds 0.01 μm ² , the threshold current value necessary for magnetization reversal increases, making it difficult to record information. Further, the smaller the thickness of the magnetosensitive layer 2, the smaller the current threshold for magnetization reversal. The thickness of the magnetosensitive layer 2 is preferably 0.01 μm or less. If the thickness exceeds 0.01 μm, the current value necessary for magnetization reversal increases, making it difficult to record information.

As a material of the nonmagnetic insulating layer 3, an oxide or nitride of a metal such as Al, Zn, or Mg, for example, Al ₂ O ₃ or MgO is preferable. As the structure of the fixed layers 4 and 40, an exchange coupling type in which an antiferromagnetic layer is added to a ferromagnetic material layer can be used. As the antiferromagnetic material, IrMn, PtMn, FeMn, NiMn, PtPdMn, RuMn, NiO, or any combination of these materials can be used. As a material of the nonmagnetic layer 41, Cu or Ru can be used. As various wiring materials, Cu, AuCu, W, Al, or the like can be used. As the material of the nonmagnetic conductive layer 41, for example, Cu can be used.

  FIG. 4 is a perspective view of the storage unit including the sealed magnetic yoke 8.

  The second wiring 7, the magnetoresistive effect element 5, and the first wiring 6 are sequentially stacked on the lower insulating layer 200, and then an insulating coating is formed to cover it, and the magnetic yoke 8 is formed thereon. The magnetic yoke is separated from the magnetoresistive element 5. The side wall of the magnetic yoke 8 is continuous all around the Z axis of the magnetoresistive effect element 5, and the top wall of the magnetic yoke 8 is provided on the top surface of the side wall to seal the magnetoresistive effect element 5. Yes.

  The lower insulating layer 200 and the magnetic layer 80 formed thereon are provided with through holes H1, H2, and H3 that reach the semiconductor substrate 100 (see FIG. 7). One end of the second wiring 7 extending in the horizontal direction (in the XY plane) is connected to the vertical wiring A1, and the vertical wiring A1 is connected to an element (transistor QR) in the semiconductor substrate 100 through a through hole H1. One end of the first wiring 6 extending in the horizontal direction is connected to the vertical wiring A2, and the vertical wiring A2 is connected to an element (terminal VW) in the semiconductor substrate 100 through a through hole H2. The other end of the first wiring 6 extending in the horizontal direction is connected to a vertical wiring A3, and the vertical wiring A3 is connected to an element (terminal VR) in the semiconductor substrate 100 through a through hole H3.

  When the above-described sealed magnetic yoke 8 is used, the leakage magnetic flux and noise from the outside of the magnetoresistive effect element 5 are all shielded by the magnetic yoke 8 even if they propagate from any side. There is an effect that it is excellent in reliability.

  More specifically, the magnetic yoke 8 covers the portion of the first wiring 6 and the second wiring 7 on the reference plane SS and the magnetoresistive element 5, and is perpendicular to the thickness direction of the magnetoresistive element 5. Located in the direction. Therefore, the introduction of an external magnetic field to the portion of the magnetoresistive effect element 5, the first wiring 6, and the second wiring 7 on the reference surface SS is suppressed. With this structure, unintended magnetization reversal of the magnetosensitive layer in the magnetoresistive element 5 can be suppressed.

  The first wiring 6 and the second wiring 7 have vertical wirings (A2, A3) and A1 extending perpendicularly to the reference plane SS, respectively. The first wiring 6 and the second wiring 7 are in the vertical direction. Since the magnetic yoke 8 is connected to an external circuit, the periphery of the magnetoresistive element 5 can be surrounded by the magnetic yoke 8.

  This magnetic memory includes a semiconductor substrate 100 (see FIG. 7) having circuit elements to which vertical wirings (A2, A3) and A1 are connected, and a magnetic layer 80 interposed between the semiconductor substrate 100 and the magnetoresistive effect element 5. And. In this case, the magnetic layer 80 can block the magnetic field introduced into the magnetoresistive element 5 from the semiconductor substrate 100 on which circuit elements such as transistors are formed. The material of the magnetic layer 80 is the same as that of the magnetic yoke 8.

  The above-described magnetic memory can suppress an increase in write current even if the magnetoresistive effect element is increased in density, does not affect the adjacent magnetoresistive effect element, and uses an assist magnetic field together with spin injection. Therefore, a high access speed can be obtained.

  FIG. 5 is a perspective view of the vicinity of the storage unit showing another arrangement of the first wiring 6 and the second wiring 7.

The first wiring 6 and the second wiring 7 are orthogonal to each other, the vertical wirings A2 and A3 extend from both ends of the portion of the first wiring 6 on the reference surface SS, and on the reference surface SS of the second wiring 7 A vertical wiring A1 extends from the end of the wiring.

FIG. 6 is a circuit diagram of a magnetic memory having a plurality of the storage areas P.

  This magnetic memory includes a word line WL connected to a gate that controls conduction of the switch QR, and the potential of the word line WL is determined by the switching circuit SWC. The read terminal VR is connected to the first bit line BL1, the write terminal VW is connected to the second bit line BL2, and the terminal VC is connected to the third bit line BL3. The potentials of these bit lines BL1, BL2, and BL3 are controlled by a control circuit. Controlled by CONT.

  When information is written into the storage area P (X, Y) at a specific address (eg, “1”), the read terminal VR of the corresponding Y-th storage area is opened, and the potential of the write terminal VW is set to be the same. The switching circuit SWC controls the potential of the word line WL to turn on the switch QR in the X-th row. As a result, the magnetization direction of the magnetosensitive layer of the magnetoresistive element 5 is, for example, “anti-parallel” with respect to the magnetization direction of the fixed layer, and “1” is written.

  In the case of writing “0”, the direction of the magnetization is, for example, “parallel”. That is, when information is written to the storage area P (X, Y) at a specific address (for example, “0”), the read terminal VR of the corresponding Y-th storage area is opened, and the potential of the write terminal VW is set. The switching circuit SWC controls the potential of the word line WL to turn on the switch QR in the X-th row. Thereby, for example, “0” is written.

  When reading the information in the storage area P (X, Y) of a specific address, the write terminal VW of the corresponding Y-th storage area is opened, and the potential of the read terminal VR is relative to the common terminal VC. The switching circuit SWC controls the potential of the word line WL to turn on the switch QR in the Xth row. Thereby, a current corresponding to the information “1” and “0” written in the magnetoresistive effect element 5 located in the storage area P (X, Y) flows between the read terminal VR and the common terminal VC. Based on this, the stored information can be determined. Note that the direction of the current at the time of reading may be opposite to this, and may be set as appropriate according to the design.

  Note that the switching circuit SWC and the control circuit CONT are formed in the semiconductor substrate.

  7 is a vertical cross-sectional view of the magnetic memory shown in FIG. 6 taken along the line VII-VII.

  The lower electrode constituting the readout wiring 7 is connected to the source or drain electrode 34a of the readout transistor QR via a vertical wiring A1 that penetrates the insulating layer 200 formed on the semiconductor substrate 100 in the thickness direction. Here, the drain electrode 34a is used. The gate electrode 34g of the read transistor QR constitutes the word line WL itself or is connected to the word line WL. The read transistor QR includes a drain electrode 34a, a source electrode 34b, a gate electrode 34g, a drain region 34a ′ and a source region 34b ′ formed immediately below the drain electrode 34a and the source electrode 34b, and corresponds to the potential of the gate electrode 34g. Thus, the drain electrode 34a and the source electrode 34b are connected. The source electrode 34b is connected to the bit line BL3 through the internal connection wiring 15.

  8 is a vertical cross-sectional view of the magnetic memory shown in FIG. 6 taken along line VIII-VIII.

An oxide film (SiO ₂ ) F made of LOCOS (local oxidation of silicon) is formed around the read transistor QR.

The bit lines BL 1, BL 2, BL 3 and the word line WL are embedded in a lower insulating layer 200 formed on the semiconductor substrate 100, and an upper insulating layer 24 is formed on the lower insulating layer 200. . A plurality of wirings are provided in the lower insulating layer 200 as necessary. The vertical wiring A1 is a wiring that penetrates the lower insulating layer 200 from the surface of the semiconductor substrate 100. The semiconductor substrate 100 is made of, for example, Si, and impurities of a conductivity type different from that of the semiconductor substrate 100 are added to the source region and the drain region. The lower insulating layer 200 is made of SiO ₂ or the like.

Figure 9 is a graph showing the relationship between the resistance value of the read current I _R and a write current I _W0, the value and the magnetoresistive element 5 I _W1 in the magnetic memory shown in FIG.

The absolute value of the information recording time of the write current _{I W1, I W0} is around 1 mA, the absolute value of the read current _{I R} at information reading is around 0.4 mA. When the absolute value of the positive write current I _W1 exceeds 0.8 mA, magnetization reversal of the magnetosensitive layer occurs and the antiparallel state “1” is recorded, and the absolute value of the negative write current I _W0 becomes 0.8 mA. If exceeded, magnetization reversal of the magnetosensitive layer occurs and a parallel state “0” is recorded.

  That is, in a ferromagnetic layer (magnetization pinned layer) / nonmagnetic layer / ferromagnetic layer laminate, when the current is increased in the positive direction of the laminate, the magnetization direction of the ferromagnetic layer is changed at a predetermined threshold (critical current). The magnetization direction of the magnetization fixed layer and the ferromagnetic layer becomes antiparallel (= “1”) and the resistance value of the magnetoresistive effect element increases. Thereafter, when the current value is decreased in the negative direction, the magnetization of the ferromagnetic layer is reversed at a predetermined negative threshold (critical current), and the magnetization directions of the magnetization fixed layer and the ferromagnetic layer are parallel (= “ 0 ") and the resistance value of the magnetoresistive element 5 decreases. Note that the current value at which such information can be recorded is set to 1.5 mA or less in consideration of the power consumption and the influence of external noise.

  In a recording element with spin injection magnetization reversal, when a current that does not exceed the critical current value is passed, the magnetization direction of the ferromagnet does not change, so the current for reading is less than the critical current value. By doing so, it is possible to perform non-destructive reading without rewriting the recorded information.

In spin injection recording in which data is recorded by performing magnetization reversal of the magnetosensitive layer by current flowing perpendicularly to the film surface, the current for reversal is 1 × 10 ⁸ to 1 × 10 ⁶ A / cm. ² and the resistance of the TMR element is relatively high. Therefore, when a write current is passed, heat generation in the TMR element portion tends to increase. However, in the above-described magnetic memory, since the magnetic yoke 8 is provided in the wiring, a current magnetic field generated by the current flowing in the wiring is efficiently generated. Then, the spin injection magnetization reversal is performed by applying a smaller current to the magnetosensitive layer. Furthermore, the magnetic yoke 8 can reduce the influence of the external magnetic field on the magnetosensitive layer in which data is recorded by the external magnetic field, and can improve the external magnetic field resistance of the memory device.

  Next, a method for manufacturing the above magnetic memory will be described.

  Although the magnetic layer 80 (see FIG. 7) is formed on the lower insulating layer 200 in advance, the description on the drawing is omitted.

First, as shown in FIG. 10A, a photoresist PR1 having an opening at the center is patterned on the lower insulating layer 200. Next, as shown in FIG. 10B, an electrode layer 7 is deposited on the photoresist PR1 by sputtering or the like. Further, as shown in FIG. 10C, lift-off is performed to remove the electrode material on the photoresist PR1. Thereafter, as shown in FIG. 10D, an underlayer 201 made of tantalum, an antiferromagnetic layer 4b made of IrMn, a ferromagnetic layer 4a made of CoFe, and an insulation made of Al ₂ O ₃ are formed on the lower insulating layer 200. The layer 3, the magnetosensitive layer 2 made of CoFe, the nonmagnetic conductive layer 41 made of Ru, the ferromagnetic layer 40 made of CoFe, and the cap layer 202 made of tantalum are sequentially deposited. The insulating layer 3 can also be formed by oxidizing it after depositing Al. A sputtering method can be used for the deposition. Next, as shown in FIG. 10E, a photoresist PR2 is patterned on the central portion of the cap layer 202. Next, as shown in FIG. That is, the photoresist PR2 is located above the lower wiring 7.

Thereafter, as shown in FIG. 11F, the stacked body is dry-etched using the photoresist PR2 as a mask. This etching is performed until the surface of the lower wiring 7 is exposed. Next, as shown in FIG. 11 (g), after removing the photoresist PR2, the cap layer 202 is formed on the lower insulating layer 200 by using a sputtering method, a CVD method or the like to form an intermediate insulating layer 200 ′ made of SiO ₂ on the lower insulating layer 200. Deposit until embedded in 200 '. Then, as shown in FIG. 11H, the intermediate insulating layer 200 ′ is polished using a CMP (Chemical Mechanical Polish) apparatus until the surface of the cap layer 202 is exposed, and the surface of the intermediate insulating layer 200 ′ is smoothed. Turn into.

  Next, as shown in FIG. 12I, a photoresist PR3 having an opening at the center is patterned on the surface of the intermediate insulating layer 200 '. Thereafter, a wiring material 6 is deposited on the photoresist PR3 by sputtering or the like (FIG. 12 (j)), the photoresist PR3 is lifted off, and an upper wiring 6 is formed on the cap layer 202 (FIG. 12 (k)). . As the wiring structure, a single layer structure composed of one kind of material such as Ti, Cu, Ta, or a multilayer structure composed of a plurality of kinds can be used.

  Thereafter, as shown in FIG. 13, the surrounding insulating layer 200 ′ is dry-etched using the upper wiring 6 as a mask until the surface of the lower insulating layer 200 (or the magnetic layer 80: see FIG. 7) is exposed, thereby exposing the exposed element. Then, the surface of the substrate is covered with a protective insulating film 200i (FIG. 13L). Thereafter, a photoresist PR having a region including an element formation region opened on the lower insulating layer 200 is patterned (FIG. 13 (m)). Subsequently, a magnetic material such as NiFe is deposited thereon and lift-off is performed. The sealed magnetic yoke 8 is completed (FIG. 13 (n)).

  The present invention can be used for a magnetic memory.

It is a perspective view of storage area P (X, Y). FIG. 3 is a longitudinal sectional view (when the magnetization direction is parallel) (a) of the magnetoresistive effect element 5, and a longitudinal sectional view (when the magnetization direction is antiparallel) (b) of the magnetoresistive effect element 5. 4 is a diagram showing a longitudinal cross-sectional configuration of a main part of an element including a magnetoresistive effect element 5. FIG. 3 is a perspective view of a storage unit including a sealed magnetic yoke 8. FIG. FIG. 6 is a perspective view of the vicinity of a storage unit showing another arrangement of the first wiring 6 and the second wiring 7. 3 is a circuit diagram of a magnetic memory including a plurality of storage areas P. FIG. It is a VII-VII arrow longitudinal cross-sectional view of the magnetic memory shown in FIG. It is a VIII-VIII arrow longitudinal cross-sectional view of the magnetic memory shown in FIG. Is a graph showing the relationship between the resistance value of the read current I _R and a write current I _W0, the value of I _W1 and the magnetoresistive element 5 in the magnetic memory shown in FIG. It is a figure for demonstrating the manufacturing method of a magnetic memory. It is a figure for demonstrating the manufacturing method of a magnetic memory. It is a figure for demonstrating the manufacturing method of a magnetic memory. It is a figure for demonstrating the manufacturing method of a magnetic memory.

Explanation of symbols

2 ... magnetic sensitive layer, 3 ... nonmagnetic insulating layer, 4 ... fixed layer, 5 ... magnetoresistive element, 6 ... upper wiring, 6a ... halfway position, 7 Lower wiring, 8 ... magnetic yoke, 24 ... upper insulating layer, 41 ... nonmagnetic conductive layer, 100 ... semiconductor substrate, 200 ... lower insulating layer, 201 ... underlayer, 202 ... cap layer, A1 ... vertical wiring, A2 ... vertical wiring, BL1, BL2, BL3 ... bit line, CONT ... control circuit, FL ... spin filter, H1, H2, H3 ... through hole, P ... memory area, QR ... transistor, SWC ... switching circuit, VC ... common terminal, VR ... terminal, WL ... word line, 80 .. -Magnetic layer.

Claims (2)

In a magnetic memory formed by arranging a plurality of storage areas,
Each said storage area is
A first wiring;
A second wiring;
A magnetoresistive element disposed between the first wiring and the second wiring and electrically connected to the first wiring and the second wiring and formed on a reference plane;
A spin filter provided in the magnetoresistive element so that the magnetization direction of the magnetosensitive layer in the magnetoresistive element is changed by spin injection;
A portion on the reference surface of the first wiring and the second wiring, the covers and the magnetoresistive element, positioned perpendicular omnidirectional in the thickness direction of the magnetoresistive element, the magnetoresistive element A magnetic yoke that surrounds
Equipped with a,
When the information is read, the first wiring and the second wiring have the same direction of each read current flowing through the first wiring and the second wiring, and the first wiring and the second wiring are arranged around the first wiring and the second wiring. Each magnetic field is disposed so as to cancel out in the magnetosensitive layer of the magnetoresistive element,
In the first wiring and the second wiring, the direction of each current flowing through the first wiring and the second wiring is opposite when writing information, and the first wiring and the second wiring are arranged around the first wiring and the second wiring. Both magnetic fields are arranged to assist the force that changes the magnetization direction of the magnetosensitive layer by spin injection,
The first and second wirings each have a vertical wiring extending perpendicular to the reference plane ,
A semiconductor substrate having a circuit element to which the vertical wiring is connected;
A magnetic layer interposed between the semiconductor substrate and the magnetoresistive element;
Equipped with a,
Each of the vertical interconnection lines via through holes provided in the magnetic layer, magnetic memory characterized in that it is connected to the circuit element. The magnetic memory according to claim 1, wherein the area of the magnetosensitive layer is 0.01 μm ² or less.

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