KR20160051524A - Magnetoresistive Device - Google Patents

Abstract

Provided is a magnetoresistive device realizing low power consumption and improved stability. The magnetoresistive device comprises: a fixed layer of which a specific magnetization direction is fixed; a free layer of which a magnetization direction is varied; and an insulation layer provided between the fixed layer and the free layer, wherein the fixed layer, the free layer and the insulation layer form a magnetic tunnel junction layer. The free layer includes a first magnetic layer and a second magnetic layer having a curie temperature lower than the first magnetic layer. The curie temperature of the second magnetic layer is set to a temperature lower than the curie temperature of the first magnetic layer, thereby amount of current inverting a magnetization direction of the first magnetic layer in writing task can be reduced.

Description

[0001] Magnetoresistive Device [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element using a magnetic tunnel junction, for example, a magnetic tunnel element using a spin injection magnetization reversal effect and a magnetoresistive element used in a magnetoresistive memory (MRAM).

Magnetoresistive random access memory (MRAM) is attracting attention as a high-speed, low-power, large-capacity non-volatile memory. The magnetoresistive memory uses a magnetoresistive element in which a magnetic tunnel junction (MTJ) is formed as a memory element. Specifically, the magnetoresistive element includes a free layer whose magnetization direction is variable, a pinned layer whose magnetization direction is fixed perpendicular to the film surface, and a tunnel barrier layer which is disposed between the free layer and the pinned layer and is made of an insulator. The pinned layer, the tunnel barrier layer, and the free layer form a magnetic tunnel junction. The magnetoresistive element is also referred to as a magnetic tunnel junction (MTJ) element.

The magnetoresistive element stores information by using the magnitude of the crystalline magnetoresistance in a relative magnetization direction of a pair of magnetic layers sandwiching the tunnel barrier layer. The magnetoresistive element performs reading by such a magnetoresistive effect and performs writing by a spin transfer torque (STT) method.

As a material of the pinned layer and the free layer, a ferromagnetic material having a high perpendicular magnetic anisotropy and a high spin polarizability is preferred.

The spin injection magnetization reversal method employed in the writing method reverses the magnetization direction of the free layer by using the magnetic moment due to the spin of electrons. The spin injection method is suitable for miniaturization and low-current generation of the device compared with the conventional wiring current method. In addition, the magnetoresistive element has thermal aging resistance against refinement.

Such a magnetoresistive element is expected as a basic constituent element of a next-generation highly integrated memory such as, for example, STT-MRAM.

However, the perpendicular magnetic anisotropy of the CoFeB material, which is currently being actively developed as a material of the free layer, is small because it utilizes the interfacial magnetic anisotropy. In addition, theoretically, a material having a high spin polarizability and a high perpendicular magnetic anisotropy is only a material such as Mn-Ge or Mn-Al system, and the material selection range is very narrow.

On the other hand, as a solution, a method of bonding the perpendicular magnetic holding layer to the MTJ has been proposed. For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2005-0328878) discloses a magnetically fixed layer having a magnet having a spin moment oriented in a direction perpendicular to a film surface and a fixed direction of the spin moment, a magnetization fixed layer having a spin moment in a direction perpendicular to the film surface A nonmagnetic layer provided between the magnetization fixed layer and the magnetic recording layer, and an antiferromagnetic film provided on at least a side surface of the magnetization fixed layer.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-150303) discloses a ferromagnetic tunnel junction having a three-layered structure of a first ferromagnetic layer / a tunnel barrier layer / a second ferromagnetic layer, The tunneling conductance is changed according to the relative angle of the magnetizations of the first and second ferromagnetic layers and the magnetization of the end of the second ferromagnetic layer changes due to the magnetization of the second ferromagnetic layer A magnetoresistive element is fixed in a direction having a component perpendicular to the axial direction.

Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2011-071352) discloses a magnetic recording medium having a first magnetic layer having a magnetization easy axis in a direction perpendicular to a film surface but having a variable magnetization direction, a first magnetization layer having a magnetization easy axis in a direction perpendicular to the film surface, And a first non-magnetic layer provided between the first magnetic layer and the second magnetic layer, wherein the first magnetic layer is formed by alternately stacking Co and Pd, or Co and Pt on the atomic surface Wherein the magnetization direction of the first magnetic layer is substantially perpendicular to the magnetization direction of the first magnetic layer, the first nonmagnetic layer, and the second magnetic layer, A magnetoresistive element which changes in accordance with a bi-directional current passing through a magnetic layer is disclosed.

With this technique, the range of materials having a high spin polarizability has been extended to the half-metal series and the Hoesler series. However, since the film thickness of the device is increased, there is a problem that it is difficult to reduce the consumption power because the magnetization reversal current increases.

In response to such a problem, for example, Patent Document 4 (Japanese Patent Laid-Open Publication No. 2014-116474) provides a magnetoresistive element that achieves low power consumption by reducing magnetization reversal current. In the magnetoresistive element of Patent Document 4, the storage layer (free layer) includes a ferromagnetic layer, a perpendicular magnetization holding layer, and a magnetic coupling control layer. A magnetic coupling control layer is provided between the ferromagnetic layer and the perpendicular magnetization maintaining layer to control magnetic coupling between the ferromagnetic layer and the perpendicular magnetization maintaining layer. By appropriately changing the thickness of the magnetic coupling control layer, various parameters such as a rate of change in resistance, thermal stability, write current, and magnetization reversal rate are optimized. As a result, the magnetization reversal current can be reduced and low power consumption can be achieved.

On the other hand, in a recording medium such as a magnetoresistive memory, it is required to have low power consumption and stability to keep recorded information securely. For example, the recording medium is used in an environment where it is exposed to heat generated by itself or another device. Therefore, it is necessary for the magnetoresistive element to have magnetization thermal stability in a free layer (storage layer) for holding information. However, the magnetoresistive element of Patent Document 1 realizes low power consumption, but does not disclose a technique for realizing magnetic stability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetoresistive element which has lower power consumption and improved stability.

The present invention is based on the relationship between the Curie temperature of the magnetic layer (ferromagnetic layer) constituting the free layer and the element temperature of the magnetoresistive element during the writing operation. According to the present invention, by appropriately selecting the Curie temperature of the free layer, the power consumption during writing operation is lowered and the magnetization direction of the free layer is stably maintained. Specifically, the magnetoresistive element according to the present invention may include the following configuration.

The magnetoresistive element according to an embodiment of the present invention may include a fixed layer having a fixed magnetization direction, a free layer having a variable magnetization direction and perpendicular magnetic anisotropy, and an insulating layer formed between the fixed layer and the free layer . The pinned layer, the free layer, and the insulating layer may form a magnetic tunnel junction layer. The free layer may include at least a first magnetic layer and a second magnetic layer having a Curie temperature lower than that of the first magnetic layer and having perpendicular magnetic anisotropy.

The Curie temperature of the second magnetic layer constituting the free layer may be lower than that of the first magnetic layer. Since the Curie temperature of the second magnetic layer is small, when the device temperature rises during the writing operation, the perpendicular magnetic anisotropy of the second magnetic layer becomes small and thermal disturbance may become very large. The first magnetic layer is adjusted so that the magnetization direction of the ferromagnetic layer is fixed. In the write operation, since the effect of thermal disturbance is increased due to the decrease of the magnetic anisotropy of the second magnetic layer, the write operation is performed at the current amount controlling the magnetization direction of the first magnetic layer. Thereafter, since the effect of thermal disturbance becomes smaller as the element temperature becomes lower, the second magnetic layer changes in the same magnetization direction as the first magnetic layer. It is possible to reduce the power consumption by constituting the magnetization direction of the second magnetic layer in such a manner that the amount of current for reversing the magnetization direction of the second magnetic layer is almost unnecessary (to a value close to zero). Since the temperature at the time of the read operation is smaller than the Curie temperature, the stability of the magnetoresistive element against heat can be improved by hybridization as before.

In the magnetoresistive element according to an embodiment of the present invention, the Curie temperature of the second magnetic layer is preferably 350K to 500K. By appropriately selecting the Curie temperature of the second magnetic layer, it is possible to adjust the range of the element temperature at which the second magnetic layer exhibits a large thermal disorder. Further, regarding the increase in thermal stability during the reading operation, the perpendicular magnetic anisotropy value of the second magnetic layer is preferably 5 × 10 ⁵ J / m ³ (5 × 10 ⁶ erg / cc) or more.

With respect to the first magnetic layer, it is preferable to have any of the following. First, the magnetic anisotropy of the first magnetic layer is in-plane magnetic anisotropy. Second, the first magnetic layer is a perpendicular having a magnetic anisotropy, the perpendicular value of the magnetic anisotropy is ^{2 × 10 5 J / m 3} (2 × 10 6 erg / cc) to ^{10 6 J / m 3 (10} 7 erg / cc). In this way, since the magnetization direction of the entire free layer is controlled in accordance with the amount of current for reversing the magnetization direction of the first magnetic layer during the writing operation, the amount of reversed current in the magnetization direction can be reduced.

The magnetoresistive element according to an embodiment of the present invention includes a magnetic coupling control layer provided between the first magnetic layer and the second magnetic layer to control magnetic coupling between the first magnetic layer and the second magnetic layer . When the second magnetic layer is changed to a ferromagnetic state with a large thermal disturbance by adjusting the magnetic coupling control layer, the magnetization direction of the second magnetic layer is controlled to be the same as the magnetization direction of the first magnetic layer (for example, can do. Thus, the thermal stability of the magnetoresistive element can be improved.

The second magnetic layer may include a material whose Curie temperature can be controlled and whose perpendicular magnetic anisotropy is large. For example, the second magnetic layer preferably includes a magnetic material such as FePtCu, [Co / Pt] n, TbFeCo, Mn ₂ RuGa, or Mn ₂ RuGe or another ferromagnetic material. The resistance value of the magnetoresistive element (MTJ element) is preferably 30 Ωμm ² or less. FePtCu, [Co / Pt] n, TbFeCo, Mn RuGa _2, and Mn ₂ RuGe is an example of a material that has a high perpendicular magnetic anisotropy constant in the low Curie temperature, and the second can be suitably used in the magnetic layer.

In addition, it is preferable that the Curie temperature of the second magnetic layer is close to the element temperature in the writing operation or lower than the element temperature in the writing operation, and is higher than the element temperature of the second magnetic layer in the reading operation. This makes it possible to adjust the Curie temperature of the second magnetic layer to be close to the device temperature to increase the heat disturbance and to adjust the Curie temperature of the second magnetic layer to be nonmagnetic if the Curie temperature is lower than the device temperature.

According to the embodiments of the present invention, it is possible to provide a magnetoresistive element having lower power consumption and improved stability.

1 is a perspective view showing a main part of an MRAM employing a magnetoresistive element according to an embodiment of the present invention.
2 is a cross-sectional view showing an example of a magnetoresistive element according to an embodiment of the present invention.
3 is a cross-sectional view illustrating a configuration example of a free layer according to an embodiment of the present invention.
4 is a view showing a concept of an example of the operation of a free layer when a write operation is performed on a magnetoresistive element according to an embodiment of the present invention.
5 is a view for explaining an example of the free layer used in the LLG simulation.
FIG. 6 is a graph showing the effect of reducing the write current using the temperature of the magnetoresistive element as a parameter in the write operation according to the results of the LLG simulation test of the free layer of FIG.
7 is a view for explaining another example of the free layer used in the LLG simulation.
8 is a graph showing the relationship between Curie temperature and current density according to the LLG simulation test results of the free layer of FIG.
9 is a graph showing the relationship between the Curie temperature and the amount of current according to the LLG simulation test result of the free layer of FIG.
10 is a graph showing a relationship between a damping constant (a) and a current density according to the results of the LLG simulation test of the free layer of Fig.
11 is a graph showing the relationship between the diameter of the free layer and the perpendicular magnetic anisotropy constant according to the results of the LLG simulation test of the free layer of FIG.
12 is a view for explaining a configuration example of a free layer in which the first magnetic layer has no perpendicular magnetic anisotropy, which is used in the LLG simulation.
13 is a graph showing the relationship between Curie temperature and current density according to the LLG simulation test results of the free layer of FIG.
FIG. 14 is a graph showing the relationship between the Curie temperature and the amount of current according to the LLG simulation test result of the free layer of FIG. 12; FIG.
15 is a graph showing the relationship between the diameter of the free layer and the perpendicular magnetic anisotropy constant according to the result of the LLG simulation test of the free layer of FIG.
16 is a graph showing the relationship between the exchange stiffness constant and the current density.
17 is a graph showing the relationship between the exchange stiffness constant and the amount of current.
18 is a graph showing a variation model of parameters according to the temperature change in the LLG simulation.
19A to 19E are views showing examples of combinations of materials constituting the free layer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of clarity, the following description and drawings have been omitted for simplicity and simplicity. In the drawings, the same constitution or substantially the same function as the constitution having the same function and the corresponding parts are denoted by the same reference numerals, and the duplicated explanation is omitted.

The configuration of the MRAM is described.

1 is a perspective view showing a main part of an MRAM employing a magnetoresistive element according to an embodiment of the present invention. 2 is a cross-sectional view showing an example of a magnetoresistive element according to an embodiment of the present invention. A magnetoresistive element according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

1, a memory cell 100, a bit line 1, contact plugs 5 and 7 and a word line 8 are shown as a substantial part of an MRAM.

The memory cell 100 may include a semiconductor substrate 2, diffusion regions 3 and 4, a source line 6, a gate insulating film 9, and a magnetoresistive element 10.

The MRAM may be formed by arranging a plurality of memory cells 100 in a matrix form and connecting the memory cells 100 to each other by using a plurality of bit lines 1 and a plurality of word lines 8. In the MRAM, the writing operation of data can be performed using a spin torque injection method.

The semiconductor substrate 2 may have diffusion regions 3 and 4 on the upper surface thereof and the diffusion region 3 may be disposed at a predetermined interval in the diffusion region 4. [ The diffusion region 3 can function as a drain region and the diffusion region 4 can function as a source region. The diffusion region 3 may be connected to the magnetoresistive element 10 through the contact plug 7. [

The bit line 1 may be disposed on the semiconductor substrate 2 and may be connected to the magnetoresistive element 10. The bit line 1 may be connected to a write circuit (not shown) and a read circuit (not shown).

The diffusion region 4 may be connected to the source line 6 through the contact plug 5. The source line 6 may be connected to a write circuit (not shown) and a read circuit (not shown).

The word line 8 may be disposed on the semiconductor substrate 2 so as to vertically overlap the diffusion regions 3 and 4. A gate insulating film 9 may be interposed between the word line 8 and the semiconductor substrate 2. [ The word line 8 and the gate insulating film 9 can function as a selection transistor. The word line 8 is activated by receiving a current from a circuit (not shown) and can be turned on by the selection transistor.

The configuration of the magnetoresistive element will be described.

2, the magnetoresistive element 10 may have a structure in which the fixed layer 11, the insulating layer 12, and the free layer 13 are laminated in this order. Alternatively, they may be stacked in the opposite order. Likewise, in the following description, the constitutions of the magnetoresistive elements shown in other drawings can also be stacked in the opposite order. The magnetoresistive element 10 can form a magnetic tunnel junction (MTJ) by the pinned layer 11, the insulating layer 12, and the free layer 13. Incidentally, in this specification, "magnetoresistive element" and "magnetic tunnel junction element (MTJ element)" are used without distinction unless otherwise specified.

The magnetoresistive element 10 can be subjected to a write operation by a spin injection magnetization reversal method. That is, the magneto-resistive element 10 may be a magneto-resistive element using a spin injection write method. In detail, in the writing operation, in the fixed layer 11 to the free layer 13 or in the free layer 13 to the fixed layer 11, in a direction perpendicular to the surface of the fixed layer 11 and the free layer 13 Electrons accumulating the spin information can be injected into the free layer 13 from the fixed layer 11 by flowing a current. Then, the magnetization of the free layer 13 can be reversed by moving the electrons of the injected electrons to the electrons of the free layer 13 according to the spin conservation law. That is, depending on the direction of the spin polarization current flowing in the direction perpendicular to the film plane of each layer, the magnetoresistive element 10 is arranged so that the relative angles of the magnetizations of the pinned layer 11 and the free layer 13 are parallel or anti- The minimum or maximum value of the resistance), and information is stored by a method of giving binary information "0" or "1 ".

The fixed layer 11 may be made of a ferromagnetic metal. The ferromagnetic metal may be, for example, Fe, Ni, CoFeB, Co / Pt, Co / Pd, or a combination thereof. The magnetization of the fixed layer 11 can be fixed in a predetermined direction. The predetermined magnetization direction may be a direction perpendicular to the surface of the pinned layer 11. It is preferable to select a material in which the fixed layer 11 does not easily change its magnetization direction as compared to the free layer 13. [ That is, it is preferable to select a material having a large effective magnetic anisotropy (Kueff) and a saturation magnetization (Ms). However, the material constituting the fixed layer 11 is not particularly limited, and any material can be selected depending on various conditions. The pinned layer 11 may also be referred to as a magnetization pinned layer, a magnetically fixed layer, a reference layer, a magnetization reference layer, a pinned layer, a reference layer, or a magnetization reference layer.

The insulating layer 12 is a tunnel barrier layer and may be an oxide having a NaCl structure. The insulating layer 12 may be made of an insulating film such as MgO. Insulating layer 12 may include CaO, SrO, TiO, VO, NbO, or Al ₂ O ₃ in addition to the above-mentioned MgO. However, the present invention is not limited thereto and is not particularly limited as long as it does not hinder the function of the insulating layer 12. The thickness of the insulating layer 12 can be appropriately changed in accordance with the resistance value of the magnetoresistive element 10. The insulating layer 12 may be referred to as a tunnel barrier layer or a barrier layer.

The free layer 13 may have magnetization whose direction can be changed. The magnetization of the free layer 13 may be magnetized perpendicular to the surface of the free layer 13, for example, and its direction may be upward or downward. The free layer 13 may have an axis of easy magnetization in a direction perpendicular to its surface. The thickness of the free layer 13 can be appropriately changed according to the surface resistance value of the target magnetoresistive element 10. The free layer 13 may also be referred to as a magnetization free layer, a magnetization variable layer, or a storage layer. The free layer 13 may comprise, for example, CoFeB, Heusler material, or MnGe.

The configuration of the free layer provided with the magnetoresistive element will be described.

3 is a cross-sectional view showing a free layer 13 according to one embodiment of the present invention. The free layer 13 may have a structure in which the first magnetic layer 31, the magnetic coupling control layer 32, and the second magnetic layer 33 are laminated in this order. That is, the free layer 13 may have a structure in which the magnetic coupling control layer 32 is formed between the first magnetic layer 31 and the second magnetic layer 33. In the following description, it is assumed that the first magnetic layer 31 of the free layer 13 is disposed adjacent to the insulating layer 12.

From the viewpoint of thermal stability, it is preferable that the first magnetic layer 31 has perpendicular magnetic anisotropy. It is preferable that the first magnetic layer 31 has magnetization in the vertical direction when magnetically coupled with the second magnetic layer 33 from the viewpoint of reducing the write current. In this case, the first magnetic layer 31 itself need not have vertical magnetic anisotropy. The first magnetic layer 31 is preferably made of a ferromagnetic material and is preferably made of, for example, a half-metal or a Fosler material.

The magnetic coupling control layer 32 can control the magnetic coupling between the first magnetic layer 31 and the second magnetic layer 33. The magnetic coupling control layer 32 may include, for example, Pd, Pt, Ru, MgO, Ta, or W. [ In addition, the magnitude of the magnetic coupling can be optimized by appropriately changing the thickness of the magnetic coupling control layer 32 to be 2 nm or less, such as the rate of change in resistance, thermal stability, write current, and magnetization reversal rate.

The second magnetic layer 33 may be composed of a material having a lower Curie temperature Tc than the first magnetic layer 31. [ The second magnetic layer 33 preferably has vertical magnetic anisotropy. The second magnetic layer 33 may be composed of a ferromagnetic or ferrimagnetic material having perpendicular magnetic anisotropy. The Curie temperature of the material constituting the second magnetic layer 33 is preferably 350K to 500K. Further, the upper limit of the Curie temperature is more preferably 450 K or less, and particularly preferably 400 K or less.

The second magnetic layer 33 is preferably made of a material having a Curie temperature lower than the expected element temperature when a write operation is performed on the magnetoresistive element. Since the expected element temperature (the temperature of the free layer or the temperature of the material constituting the free layer) is about 350K to 400K when the writing operation is performed on the magnetoresistive element, the Curie temperature of the second magnetic layer 33 is higher than 350K If it is low, the temperature of the magnetoresistive element may be influenced by the reading operation. That is, there may be a problem in the thermal stability during the reading operation. It is preferable that the Curie temperature of the second magnetic layer 33 is higher than the element temperature of the second magnetic layer 33 in the reading operation. On the other hand, if the Curie temperature of the second magnetic layer 33 is higher than 500 K, the temperature range in which the second magnetic layer 33 is greatly affected by thermal disturbance becomes small, . Therefore, the Curie temperature of the second magnetic layer 33 is preferably set to 350K to 500K. In this case, it is possible to secure the thermal stability during the reading operation and to reduce the power consumption during the writing operation.

In addition, it is preferable that the element resistance of the magnetoresistive element 10 is 30 Ωμm ² or less. When an environment such as a DRAM is applied, 30 Ωμm ² is preferable for using an element such as MRAM.

3 shows an example (three-layer structure) in which the free layer 13 is composed of three layers of a first magnetic layer 31, a magnetic coupling control layer 32 and a second magnetic layer 33 . However, in the case where the free layer 13 is composed of two layers of the first magnetic layer 31 and the second magnetic layer 33 without having the magnetic coupling control layer 32 (two-layer structure) Do. In other words, the free layer 13 may have a structure in which the first magnetic layer 31 and the second magnetic layer 33 are laminated, unlike the structure shown in Fig.

An example of operation of the free layer is described.

Next, an operation example will be described with reference to a specific configuration example of the free layer 13 based on the above-described configuration example of the free layer 13. [

4 is a diagram showing a concept of an example of the operation of the free layer 13A when writing operation is performed on the magnetoresistive element. The magnetic coupling control layer (ECC layer) 32A may be disposed between the first magnetic layer 31A and the second magnetic layer 33A. Although FIG. 4 shows a configuration example provided with the magnetic coupling control layer 32A, it is also possible to adopt a configuration without the magnetic coupling control layer 32A.

In Fig. 4, an insulating layer 12 is shown for ease of explanation of the operation of the free layer 13A. 4 shows the case where the insulating layer 12 is a MgO barrier.

In the following description, the Curie temperature of the first magnetic layer 31A is Tc1, the perpendicular magnetic anisotropy constant is Ku1, the Curie temperature of the second magnetic layer 33A is Tc2, and the perpendicular magnetic anisotropy constant is Ku2 .

4 is described on the premise that the Curie temperature Tc2 is smaller than the Curie temperature Tc1 and is 500 K or less. Ferro magnetization when the temperature of the second magnetic layer 33A (in particular, the temperature of the material of the second magnetic layer 33A) is lower than the Curie temperature Tc2, and the second magnetic layer 33A, Lt; RTI ID = 0.0 > Tc2. ≪ / RTI >

The perpendicular magnetic anisotropy constants Ku1 and Ku2 are not particularly limited, but it is preferable that the first magnetic layer 31A and the second magnetic layer 33A have perpendicular magnetic properties. The values of the perpendicular magnetic anisotropy constants Ku1 and Ku2 may be coincident or may be different from each other. The perpendicular magnetic anisotropy constant Ku1 is zero, that is, the first magnetic layer 31A may be made of a material having no perpendicular magnetic anisotropy. The first magnetic layer 31A and the second magnetic layer 33A may have perpendicular magnetic anisotropy as a whole.

Each of the perpendicular magnetic anisotropy constants is a value indicating the stability of the orientation of the easy magnetization axis. The larger the value is, the more difficult it is for the easy axis of magnetization arranged in the vertical direction to be shaken.

Referring to Fig. 4, an operation example of the free layer 13A and a reduction in magnetization inversion current of the magnetoresistive element will be described. 4 is a graph showing the state of the magnetization direction of the free layer 13A in the order of before writing in step 1, writing process in step 2, and writing after writing in step 3 Layer 31A and the second magnetic layer 33A.

Step 1 shows the magnetization direction of the free layer 13A before writing, specifically, before the write current flows in the bit line 1 and the word line 8 in Fig. The first magnetic layer (31A, High Tc layer) and the second magnetic layer (33A, Low Tc layer) have the same magnetization direction and face downward.

Step 2 shows the magnetization direction of the free layer 13 in the write operation, specifically, when the write current flows through the bit line 1 and the word line 8 in FIG. The temperature of the free layer 13A can be raised by the write current. For example, when the temperature of the second magnetic layer 33A constituting the free layer 13A rises to about 350K to 400K (or the temperature difference during the writing operation is 50K to 100K) When the Curie temperature Tc2 of the layer 33A is less than 500K, the second magnetic layer 33A is influenced by strong heat disturbance, and the magnetization direction is not determined, so that it can behave like a box. That is, when the element temperature becomes equal to or higher than the Curie temperature Tc2, the magnetic moment of the second magnetic layer 33A becomes random and can become paramagnetic. On the other hand, the magnetization direction of the first magnetic layer 31A can be reversed by the flow of the spin. In the case of Fig. 4, the magnetization direction of the first magnetic layer 31A faces upward. Thus, according to the configuration of the free layer 13A of FIG. 4, the hybrid type tunnel junction (free) structure in which the Curie temperature is composed of a combination of two magnetic layers (for example, Tc: 700K) Layer), the magnitude of the current during the writing operation can be reduced. This is because it reverses only the magnetization direction of the first magnetic layer 31A, not the entirety of the free layer 13A.

Step 3 shows the magnetization direction of the free layer 13A after the write operation, specifically when the application of the write current is stopped. The magnetization direction of the first magnetic layer 31A is directed upward in the same direction as in step 2. As the temperature of the element is lowered, the magnetic moment of the second magnetic layer 33A returns to the property of the ferromagnetic body, and the direction thereof can be directed upward by the magnetic interaction with the magnetization of the first magnetic layer 31A .

During the read operation, the device temperature drops to room temperature, so that the magnetoresistive device can be thermally stable.

The magnitude of energy for thermal stability (i.e., perpendicular magnetic anisotropy energy) can be very stable because it relates to the perpendicular magnetic anisotropy constants Ku1 and Ku2. Since this formula is a general formula, a detailed description thereof will be omitted. More specifically, since the perpendicular magnetic anisotropy energy is 60 times or more the heat energy kT generated by heat, the stability of the magnetoresistive element against heat can be improved. This is because the perpendicular magnetic anisotropy energy is very large compared to the thermal disorder energy.

Although the magnetic coupling control layer 32A is shown in Fig. 4, the operation of the free layer 13A may be the same as that described above, even when the magnetic coupling control layer 32A is absent.

According to the configuration example of the free layer 13A shown in Fig. 4, the magnetization inversion current can be reduced while maintaining the thermal stability of magnetization. In addition, the magnitude of the magnetic coupling between the first magnetic layer 31A and the second magnetic layer 33A can be optimized by changing the thickness of the magnetic coupling control layer 32A.

The properties of the free layer and the test results are described.

Using the LLG (Landau-Liftshitz-Gilbert-Langevin equations) simulation, the free layer 13 has a first magnetic layer 31 having a high Curie temperature and a second magnetic layer 31 having a Curie temperature lower than the element temperature Layer 33 constituted by the layer 33 is applied to reduce the power consumption in the writing operation. The results of the test will be described together with a specific example of the configuration of the free layer 13 used in the simulation.

A change in magnetization inversion current (change in reversal probability due to a current) due to a temperature rise of the second magnetic layer is explained.

5 shows an example of the configuration of the free layer 13B used in the LLG simulation. The free layer 13B is composed of a first magnetic layer 31B, a magnetic coupling control layer 32B (Ecc Layer or Spacer), and a second magnetic layer 33B (Low Tc Layer). The power consumption in the writing operation is evaluated by the current density when the magnetization of the free layer 13B (the first magnetic layer 31 and the second magnetic layer 33) is reversed (switched) .

The description and setting parameters of the first magnetic layer 31 and the second magnetic layer 33 are described below.

(1) The first magnetic layer 31B

Material: MnGe series

Magnetic moment (Ms1): 150 x 10E3 A / m (150 emu / cc)

Perpendicular magnetic anisotropy constant (Ku1): 10 × 10E5 J / m 3 (10 × 10E6 erg / cc)

Attenuation constant α = 0.005

Curie temperature (Tc1, High Tc): 700K or more

Polarization rate P = 1.0

(2) The second magnetic layer 33B

Material: FePtCu

Magnetic moment (Ms2): 800 x 10E3 A / m (800 emu / cc)

Perpendicular magnetic anisotropy constant (Ku2): 10 × 10E5 J / m 3 (10 × 10E6 erg / cc), at room temperature ¹

Attenuation constant α = 0.01

Curie temperature (Tc2, Low Tc): 523.15K

In addition, the parameters indicated in CGS units in parentheses are used in the above-described LLG simulation. Parameters indicated in SI units can be obtained by using the following parameters (A) and (B) in parenthesis in CGS units.

10 erg / cc = 1 J / m 3 ... (A)

1 G = 1 emu / cc = 1 x 10 E3 A / m (B)

In the other LLG simulations described in this specification, like the above-described LLG simulation, parameters indicated in CGS units in parentheses are used. Parameters indicated in SI units can be obtained by using the above-mentioned parameters (A) and (B) in parentheses as CGS units.

The height of the first magnetic layer 31B is 2 nm (h1 = 2 nm), the height of the magnetic coupling control layer 32B is 0 nm (hsp = 0), the height of the second magnetic layer 33B is 2 nm ).

The diameter (width) D of the free layer 13B was 20 nm. Here, it is assumed that the free layer 13B is cylindrical, and the cross-sectional diameter D of the free layer 13B is used as a value representing the size of the free layer 13B. The size of the free layer 13B can be represented by using the diameter when the free layer 13B has a circular cross section and by using the long diameter (length of the long axis) when the free layer 13B is an ellipse. When the cross section of the free layer 13B is different, the diameter of the circumscribed circle circumscribing the free layer 13B can be used.

The temperature change was set at 10 to 223 ° C with the temperature rise ΔT as a parameter. The temperature change during writing was as follows.

The temperature of the first magnetic layer 31B was always 300K. The temperature rise in the writing operation occurred only in the second magnetic layer 33B, and the temperature changed as follows. Even if the temperature rise of the first magnetic layer 31B is considered, there is no difference in the results.

After the application of the write current, the temperature of the second magnetic layer 33B rises and reaches a saturated state within 1 ns.

The write current is applied to 10 ns. At this time, the device temperature is in a steady state.

After the writing operation, the temperature of the second magnetic layer 33B was lowered to 300K within 5 ns.

FIG. 6 is a graph showing the effect of reducing the write current with the rising temperature of the magnetoresistive element as a parameter in the write operation according to the result of the LLG simulation. The graph of FIG. 6 shows the current density (A / m ² ) on the horizontal axis and the inversion probability (switching probability, sw. Probe) on the vertical axis. The inversion probability indicates the probability that the magnetization direction of the free layer 13B is reversed at any current density, and Fig. 6 shows the probability in the range of 0 (zero) to 1. If the temperature of the second magnetic layer 33B in the free layer 13B of the embodiment of the present invention becomes higher than the Curie temperature Tc2, the reversal probability of the free layer 13B becomes higher than the Curie temperature Tc2 when the probability of reversing the first magnetic layer 31B Lt; / RTI > This is because the magnetization direction of the first magnetic layer 31B is reversed when the second magnetic layer 33B is in a state where the thermal disturbance is large or becomes paramagnetic in the writing operation of the free layer 13B, This is because the magnetization direction of the ground second magnetic layer 33B is determined.

In FIG. 6,? T (degree C, referred to as "deg." In FIG. 6) represents the amount of temperature elevation (temperature rise amount) during the writing operation from before the writing operation. Here, the temperature rise amount of the second magnetic layer 33B is shown.

As shown in the graph of FIG. 6, as the temperature rise amount of the second magnetic layer 33B increases, the current density at which the magnetization direction reverses becomes small. That is, the amount of current required for the inversion of the magnetization direction of the free layer 13B (hereinafter referred to as the "amount of reversed current" required for the inversion of the magnetization direction) decreases. In the example of FIG. 6, it can be seen that when the temperature of the second magnetic layer 33B rises close to the Curie temperature Tc2, the amount of the reversed current drops to a quarter or less. Specifically, when the current density at which the inversion probability is 0.5 is considered, when the current density becomes close to the Curie temperature Tc2 at 223 DEG C (496.15K) (adjacent to the Curie temperature Tc2), the current density becomes 4 minutes 1 < / RTI >

As described above, according to the magnetoresistive element according to the embodiment of the present invention, it is possible to reduce the power consumption in the writing operation. The magnitude of the energy for thermal stability when the temperature of the device returns to room temperature is the sum of the effects of the magnetic anisotropy energy Ku1 of the first magnetic layer 31B and the magnetic anisotropy energy Ku2 of the second magnetic layer 33B It is very stable.

As another example, the power saving effect in writing operation according to the Curie temperature will be described.

Hereinafter, test results obtained by performing the LLG simulation using the free layer 13C configuration shown in FIG. 7 will be described. In this test, a free layer 13C having a two-layer structure composed of a first magnetic layer 31C having a high Curie temperature and a second magnetic layer 33C having a Curie temperature lower than the element temperature in a writing operation is used And the Curie temperature of the second magnetic layer 33C, the effect of reducing the amount of reversed current at the writing operation was confirmed.

Details of the free layer 13C will be described below.

(1) The first magnetic layer

Material: CoFeB layer

Magnetic moment (Ms1): 1 x 10E6 A / m (1000 emu / cc)

Perpendicular magnetic anisotropy constant (Ku1): 2 × 10E5 J / m 3 (2 × 10E6 erg / cc)

Attenuation constant α = 0.01

Curie temperature (Tc1): 700K

Polarization rate P = 1.0

(2) Second magnetic layer

Material: FePtCu layer

Magnetic moment (Ms2): 600 x 10E3 A / m (600 emu / cc)

Perpendicular magnetic anisotropy constant (Ku2): Ku1 × 2 J / m 3

Attenuation constant α = 0.01

Curie temperature (Tc2): 700K, 500K, 450K, 400K

(3) Other

The diameter D of the free layer 13C was 10 nm to 20 nm.

The height of the first magnetic layer 31C is 2 nm (h1 = 2 nm), the height of the magnetic coupling control layer 32C is 0 nm (hsp = 0), the height of the second magnetic layer 33C is 2 nm (h2 = 2 nm) . The thickness of the magnetic coupling control layer 32C is set to 0 and the free layer 13C is configured not to include the magnetic coupling control layer 32C.

In the LLG simulation using the configuration of the free layer 13C, the magnetic anisotropy constant Ku value was adjusted such that the amount of rise Δ of the element temperature (material) of the second magnetic layer 33C was 60.

In addition, as a comparative example, a test was also conducted on a general free layer structure not having the above-described two-layer structure.

Material: Co / Ni mulutilayer

Magnetic moment (Ms): 600 x 10E3 A / m (600 emu / cc)

Perpendicular magnetic anisotropy constant (Ku): 6 × 10E5 J / m 3 (6 × 10E6 erg / cc)

Curie temperature (Tc): greater than 700K (426.85 ° C) (> 700K)

Figs. 8 to 10 show an analysis of the results of the LLG simulation test of the free layer shown in Fig. FIG. 8 is a graph showing the relationship between Curie temperature and current density, FIG. 9 is a graph showing the relationship between Curie temperature and current amount, and FIG. 10 is a graph showing a relationship between attenuation constant? And current density. Figs. 8 to 10 are the results of a test on the premise that the element temperature of the free layer increases by 50 DEG C during the writing operation of the magnetoresistive element.

The graph shown in Fig. 8 shows the Curie temperature Tc (K) on the abscissa and the current density j _sw (x 10 ¹² A / m ² ) on the ordinate. The graph shown in Fig. 9 shows Curie temperature Tc (K) on the abscissa and current _swsw (mA) on the ordinate. 8 and 9 are graphs showing curie temperature Tc at various Curie temperatures (Examples) using various values (example) of Curie temperature Tc2 of the second magnetic layer 33C and values of curie temperature (700K) of a general free layer Fig.

The diameter D of the free layer 13C is 10 nm in the solid line and 20 nm in the dotted line.

As can be seen from the graphs shown in FIGS. 8 and 9, the free layer 13C having a Curie temperature Tc of 500K or less can reduce power consumption as compared with a general free layer having a Curie temperature of 700K (or 700K or more). For example, when the element temperature of the second magnetic layer 33C is raised by 50 DEG C, power consumption of 40 to 50% can be saved.

The graph shown in FIG. 10 is plotted on the abscissa axis with the attenuation coefficient a of the second magnetic layer as a parameter, and the current density j _sw (x 10 ¹² A / m ² ) is shown on the ordinate axis. 10, the solid line is a test result (example) in the case where the Curie temperature of the second magnetic layer 33C in the free layer 13C shown in Fig. 7 is 400K, and the dotted line indicates the general free layer ) (Comparison example). The free layer 13C of FIG. 7 is less affected by the attenuation constant alpha than a typical free layer. Therefore, the range of the material of the second magnetic layer 33C can be widened. That is, a magnetic material having a relatively large attenuation constant and a small Tc can be used.

11 is a graph showing the relationship between the diameter of the free layer 13C and the perpendicular magnetic anisotropy constant Ku used for the LLG simulation test of the free layer shown in FIG. 11 shows the diameter D (nm) of the free layer 13C on the abscissa and the perpendicular magnetic anisotropy constant Ku (Merg / cc) on the ordinate. The solid line represents the test result of the FePtCu layer constituting the second magnetic layer 33C and the dotted line represents the test result of the CoFeB layer constituting the first magnetic layer 33A. The perpendicular magnetic anisotropy constant Ku1 of the FePtCu layer is greater than the Ku1 value of the perpendicular magnetic anisotropy constant Ku1 of the CoFeB layer, and the thermal stability parameter KuV / Kt is 60 (KuV / Kt = 60) 2 times (Ku2 @ FePtCu = 2 x Ku1 @ CoFeB). During the writing operation, the temperature of the second magnetic layer 33C was raised to 300K.

As shown in FIG. 11, when the diameter D of the free layer 13C is 10 nm, the perpendicular magnetic anisotropy constant Ku is large and the perpendicular magnetic anisotropy constant Ku is small as the diameter D is increased. Therefore, when the magnitude of the magnetoresistive element (magnetic tunnel junction element) (the diameter of the free layer) is small, it is necessary to set the perpendicular magnetic anisotropy constant Ku to a large value. It has also been found that the necessity of increasing the perpendicular magnetic anisotropy constant Ku is different depending on the material constituting the free layer and / or the size of the magnetoresistive element.

The power consumption reduction when the first magnetic layer does not have vertical magnetic anisotropy will be described.

Hereinafter, test results obtained by performing the LLG simulation using the configuration of the free layer 13D shown in Fig. 12 will be described. The free layer 13D has a dual structure composed of a first magnetic layer 31D and a second magnetic layer 33D.

When the first magnetic layer 31D is constructed such that the perpendicular magnetic anisotropy constant Ku1 is zero and the first magnetic layer 31D of the free layer 13D does not have vertical magnetic anisotropy, We tested whether power could be reduced.

The thickness of the magnetic coupling control layer 32D is set to 0 (hsp = 0 nm) so that the free layer 13D does not have the magnetic coupling control layer 32D.

The details of the free layer 13D are described below.

(1) The first magnetic layer

Material: CoFeB layer having in-plane magnetic anisotropy or CFMS layer

Magnetic moment (Ms): 1 x 10E6 A / m (1000 emu / cc)

Perpendicular magnetic anisotropy constant (Ku1): 0 J / m 3 (0 erg / cc)

Attenuation constant α = 0.01

Curie temperature (Tc1): 700K (426.85 DEG C)

Polarization rate P = 1.0

(2) The second magnetic layer

Material: FePtCu layer

Magnetic moment (Ms): 600 x 10E3 A / m (600 emu / cc)

Vertical magnetic anisotropy constant (Ku2): When the diameter D of the free layer is in the range of 10-20 nm,

So that the thermal stability constant Δ value of the free layer is 60

Adjusts the value of the vertical deformation anisotropy constant Ku2

Damping constant α = 0.01

Curie temperature (Tc): 360K, 400K, 450K, 500K, 700K

(86.85 ° C, 126.85 ° C, 176.85 ° C, 226.85 ° C, 426.85 ° C)

(3) Other

The diameter D of the free layer 13D was 10-20 nm.

The height of the first magnetic layer 31D is 2 nm (h1 = 2 nm), the height of the magnetic coupling control layer 32D is 0 nm (hsp = 0), and the height of the second magnetic layer 33D is 2 nm = 2 nm).

The various Curie temperatures Tc of the second magnetic layer 33D are parameters, and the Curie temperature Tc is set to be a general free layer when the temperature Tc is 700K.

13 to 15 are graphs showing results of LLG simulation test of the free layer shown in FIG. FIG. 13 is a graph showing the relationship between Curie temperature and current density, FIG. 14 is a graph showing the relationship between Curie temperature and current amount, and FIG. 15 is a graph showing the relationship between the diameter of the free layer and the perpendicular magnetic anisotropy constant.

The graph shown in Fig. 13 shows the Curie temperature Tc (K) on the abscissa and the current density j _sw (x 10 ¹² A / m ² ) on the ordinate. The graph shown in Fig. 14 shows Curie temperature Tc (K) on the abscissa and current _swsw (mA) on the ordinate. 13 and 14 show the current density or the amount of current when the magnetic direction of the first magnetic layer 31D is reversed at each Curie temperature set as a parameter.

The value of the diameter D of the free layer 13D is 10 nm for the solid line and 20 nm for the dotted line.

As can be seen in Figures 13 and 14, the free layer 13D can significantly reduce power consumption when the Curie temperatures are 360K, 400K and 450K. For example, when the Curie temperature Tc of the second magnetic layer 33D is 400K or less, the power consumption of 50-70% can be saved when the element temperature rises by 50 deg. It was confirmed from the test results of FIGS. 13 and 14 that even when the first magnetic layer does not have perpendicular magnetic anisotropy, the effect of saving power is generated.

The graph shown in Fig. 15 shows the diameter D of the free layer 13D on the abscissa and the perpendicular magnetic anisotropy constant Ku2 (Merg / cc) of the second magnetic layer 33D on the ordinate. The thermal stability parameter (KuV / Kt) was set to 60 (KuV / Kt = 60) for the perpendicular magnetic anisotropy constant Ku and the Ku1 value of the CoFeB layer or CFMS layer was adjusted to be zero. During the write operation, the temperature of the second magnetic layer 33C was raised to 300K.

As shown in FIG. 15, when the diameter D of the free layer 13D is 10 nm, the perpendicular magnetic anisotropy constant Ku2 is large and the perpendicular magnetic anisotropy constant Ku2 becomes small as the diameter D increases. Therefore, when the magnitude of the magnetoresistive element (magnetic tunnel junction element) (diameter of the free layer) is small, it is necessary to set the vertical magnetic anisotropy constant Ku2 of the second magnetic layer 33D to a large value. That is, when the first magnetic layer 31D does not have vertical magnetic anisotropy, the second magnetic layer 33D preferably has perpendicular magnetic anisotropy. Particularly when the diameter of the free layer 13D is small The necessity of increasing the perpendicular magnetic anisotropy constant Ku2 is higher than when the diameter is large.

A review of the exchange stiffness constant of the first and second magnetic layers is described.

Hereinafter, test results obtained by examining the self-exchange stiffness constant after the LLG simulation is performed using the configuration of the free layer 13D shown in FIG. 12 will be described. This test changed the parameters of the second magnetic layer 33D in the free layer 13D described with reference to Fig. 12 as follows.

Curie temperature (Tc): 400K, 700K (126.85C, 426.85C)

Exchange coupling constant A: 0.1 - 2.0 × 10 ^-13 J / cm (0.1 - 2.0 × 10 ^-6 erg / cm)

This test assumes that the device temperature increases by 50 ° C during writing.

When Curie temperature Tc is 400K, it is a free layer according to an embodiment of the present invention, and when it is 700K, it is a general free layer. Tests were conducted for the cases where the diameter D of the free layer was 10 nm and 20 nm, respectively.

Figures 16 and 17 show the test results of exchange coupling constants. Figure 16 is a magnetic exchange stiffness constant (× 10 ^-6 erg / cm) and current density ^{_{j sw (× 10 12 A /}} m 2) is a graph showing a relationship, Figure 17 is the magnetic exchange stiffness constant A (× 10 ^-6 erg / cm) and the current amount i _sw (mA). The magnetic exchange stiffness constant A can be adjusted through the thickness of the magnetic coupling control layer 32C. It can be confirmed that the optimum value of the magnetically exchangeable stiffness constant A at which the inversion current becomes smaller is smaller when the diameter D of the free layer is 10 nm than when it is 20 nm. In addition, when the diameter D of the free layer is the same, it can be seen that the inverse current value of the free layer according to an embodiment of the present invention is smaller than that of a general free layer. Therefore, the magnetoresistive element according to the embodiment of the present invention can reduce the magnetization reversal current without impairing the thermal stability. And the thermal stability of the magnetoresistive element can be improved.

18 shows a variation model of the parameter according to the temperature change in the LLG simulation.

The graph shown in FIG. 18 corresponds to the Curie temperature Tc of the transverse axis and the magnetic moment Ms of the longitudinal axis, the perpendicular magnetic anisotropy constant Ku, or the conversion parameter A. FIG. That is, the ratio (T / Tc) of the Curie temperature Tc to the temperature T of the material when the current flows is made to correspond to the value of each parameter. Each parameter is expressed as a ratio of the value of each element (Ms0, Ku0, A0) and the value of each element (Ms, Ku, A) when the temperature of the material is zero.

Other embodiments will be described.

19A shows an example of the configuration of the STT-MRAM. FL denotes a free layer, MgO denotes an insulating layer, PEL denotes a reference layer, and Ru denotes a layer which helps crystal orientation of the reference layer.

[Co / Pt] ML is a perpendicular magnetic holding layer, and seed indicates a layer controlling crystal orientation.

19B to 19E show structural examples of the free layer FL of FIG. 19A.

19B and 19C, a CoFeB layer may be used for the first magnetic layer of the free layer and an FePtCu layer or the Fe / Pt / Cu multilayer may be used for the second magnetic layer. Referring to FIG. 19D, a MnGe layer may be used for the first magnetic layer and an FePtCu layer may be used for the second magnetic layer. Referring to Figure 19 (e), a Feis / Pt / Cu multilayer may be used for the first magnetic layer and the second magnetic layer.

For example, FePtCu has a high perpendicular magnetic anisotropy constant Ku and is a material having a low Curie temperature Tc, which is preferable for use as the second magnetic layer. A material having a high Curie temperature Tc and a high perpendicular magnetic anisotropy can be used as the second magnetic layer. For example, a magnetic material such as FePtCu [Co / Pt] n, TbFeCo, Mn ₂ RuGa, or Mn ₂ RuGe Can be used.

For example, the LLG simulation was performed using a CoFeB layer as the first magnetic layer and an FePtCu layer or Fe / Pt / Cu multilayer as the second magnetic layer, and the following test results were obtained.

FePtCu layer

Magnetic moment (Ms): 600 x 10E3 A / m (600 emu / cc)

Perpendicular magnetic anisotropy constant (Ku2): 10 × 10E5 J / m 3 (10 × 10E6 erg / cc), at room temperature ¹

Curie temperature (Tc): 250 DEG C (523.15K)

Attenuation constant α = 0.01

CoFeB layer

Magnetic moment (Ms): 1 x 10E6 A / m (1000 emu / cc)

Perpendicular magnetic anisotropy constant (Ku1): 2 × 10E5 J / m 3 (2 × 10E6 erg / cc), at room temperature ¹

Curie temperature (Tc): temperature above 250 ° C (523.15K) (>>> 250 ° C)

Attenuation constant α = 0.01

In the above-described four kinds of free layer structure examples, the magnetic coupling control layer (ECC layer) may include, for example, Pd, Pt, Ru, MgO, Ta, and /

The second magnetic layer of the free layer may comprise, for example, MnGeX, [Co / Pt] n, TbFeCo, FePtCu, and / or Mn2RuGa.

As described above, a magnetoresistive element having a vertical magnetization and performing a read operation by the magnetoresistive effect is expected to be a next generation memory because of its high resistance to thermal disturbance due to miniaturization. On the other hand, it is difficult to form a ferromagnetic thin film having high vertical magnetic anisotropy, which is a main component of the magnetoresistive element. To solve this problem, when the vertical magnetization holding layer is bonded to the MTJ, magnetization reversal current increases, There is a problem that it is difficult to implement the device. With respect to these problems, in a magnetoresistive element according to an embodiment of the present invention, in a magnetoresistive element in which an insulating thin film is sandwiched between two ferromagnetic thin films and formed by magnetic tunnel junction, a perpendicular magnetic film having a low Curie temperature Tc is vertically magnetized The magnetization thermal stability of the free layer (recording layer) is maintained and the magnetization reversal current is reduced. This technology contributes to the practical use of STT-MRAM.

More specifically, the free layer included in the magnetoresistive element according to an embodiment of the present invention has at least a first magnetic layer and a second magnetic layer. By adjusting the Curie temperature of the second magnetic layer to be lower than the Curie temperature of the first magnetic layer, the recording current can be reduced by the temperature raising effect during the recording operation. For example, the power consumption during recording can be reduced by 50% or more as compared with a general technique.

The present invention relates to an MTJ element for a highly integrated STT-MRAM using a spin injection magnetization reversal effect, such as a STT-MRAM (Spin Transfer Torque Magnetic Random Access Memory) or a Racetrack-memory (magnetic non-volatile memory) Can be used.

1: bit line
2: semiconductor substrate
3, 4: diffusion regions
5, 7: contact plugs
6: Source line
8: Word line
9: Gate insulating film
10: Magnetoresistive element
11, 21: Fixed layer
12: Insulation layer
13, 13A, 13B, 13C: free layer
100: memory cell
31, 31A, 31B, 31C: a first magnetic layer
32, 32A, 32B, 32C: magnetic coupling control layer
33, 33A, 33B and 33C: a second magnetic layer

Claims (9)

A fixed layer having a fixed magnetization direction;
A free layer having a first magnetic anisotropy, the magnetization direction of which is variable; And
And an insulating layer provided between the fixed layer and the free layer,
Wherein the fixed layer, the free layer, and the insulating layer form a magnetic tunnel junction,
Said free layer comprising:
A first magnetic layer; And
And a second magnetic layer having a Curie temperature lower than that of the first magnetic layer and having a second perpendicular magnetic anisotropy.
The method according to claim 1,
And the Curie temperature of the second magnetic layer is 350K or more and 500K or less.
The method according to claim 1,
The magnetoresistive element is greater than or equal to the second vertical size of the magnetic anisotropy is ^{5 × 10E5 J / m 3 (} 5 × 10E6 erg / cc).
4. The method according to any one of claims 1 to 3,
Wherein the first magnetic anisotropy is in-plane.
4. The method according to any one of claims 1 to 3,
The direction of the first magnetic anisotropy being perpendicular to the surface of the free layer,
It said first magnitude of magnetic anisotropy is ^{2 × 10E5 J / m 3 (} 2 × 10E6 erg / cc) or less than the magnetoresistive element, and ^{10E6 J / m 3 (10E7 erg} / cc).
4. The method according to any one of claims 1 to 3,
Wherein the free layer is provided between the first magnetic layer and the second magnetic layer and further includes a magnetic coupling control layer for controlling magnetic coupling between the first magnetic layer and the second magnetic layer.
4. The method according to any one of claims 1 to 3,
Said second magnetic layer is made of a magneto-resistive element FePtCu, [Co / Pt] n , TbFeCo, Mn 2 RuGa, Mn 2 RuGe, or a ferromagnetic material other than the.
4. The method according to any one of claims 1 to 3,
And the resistance value of the magnetoresistive element is 30 Ωμm ² or less.
4. The method according to any one of claims 1 to 3,
Wherein a Curie temperature of the second magnetic layer is lower than a temperature of the second magnetic layer in a writing operation and is higher than a temperature of the second magnetic layer in a reading operation.

Images