JP5472830B2 - Ferromagnetic random access memory - Google Patents

Description

The present invention relates to a ferromagnetic random access memory using a TMR element that reads information using a tunneling magnetoresistance effect.

Recently, as one of nonvolatile memories, a ferromagnetic random access memory (Magnetic Random Access Memory; hereinafter referred to as “MRAM”) using a ferromagnetic film that stores data as a magnetization direction has been proposed. MRAM using a ferromagnetic tunnel junction having a resistance effect has been developed extensively.

The ferromagnetic tunnel junction has a laminated structure in which a nonmagnetic insulating film (hereinafter referred to as a “tunnel barrier film”) is sandwiched between a first ferromagnetic film and a second ferromagnetic film. Is configured using an element having this laminated structure as a memory cell. The electrical resistance when a current flows in the direction of the thickness of the tunnel barrier film of the ferromagnetic tunnel junction changes depending on the relative angle of the magnetic moment of the first and second ferromagnetic films, and when the magnetic moments are parallel to each other The electric resistance becomes minimum, and the electric resistance becomes maximum when antiparallel. This change in resistance value is called a tunneling magnetoresistance effect (TMR effect), and the larger the ratio (MR ratio) of the TMR effect to the electrical resistance value, the more advantageous it is for reading recorded information. That is, in the MRAM, data is stored by associating, for example, data “1” and “0”, respectively, when the magnetic moment directions of the two ferromagnetic layers are parallel and antiparallel. . The signal difference between data “1” and “0” increases as the MR ratio of the ferromagnetic tunnel junction increases. Usually, one of the two ferromagnetic films is used as a “fixed layer” (or “pinned layer”) with a fixed magnetic moment, and the direction of the magnetic moment of the other ferromagnetic film is “fixed” Data is recorded by making it parallel or anti-parallel to the magnetic moment of the layer. A ferromagnetic film on which data is recorded is generally called a “free layer” or a “recording layer”. In this specification, a ferromagnetic film on which data is recorded is referred to as a “magnetic recording layer”.

Conventionally known methods of writing data to the MRAM include an “asteroid method” as disclosed in Patent Document 1 and a “toggle method” as disclosed in Patent Document 2 and Patent Document 3. . According to these write methods, the reversal magnetic field necessary for reversing the magnetization of the free layer increases in inverse proportion to the memory cell size. That is, the write current tends to increase as the memory cell is miniaturized.

As a write method that can suppress an increase in write current due to miniaturization, for example, a “spin injection method” as disclosed in Patent Document 4 and Non-Patent Document 1 has been proposed. According to the spin injection method, a spin-polarized current is injected into the ferromagnetic conductor, and the magnetization is reversed by a direct interaction between the spin of the conduction electron carrying the current and the magnetic moment of the conductor. (This phenomenon is hereinafter referred to as “Spin Transfer Magnetization Switching”). However, when spin injection magnetization reversal is applied to the magnetization reversal of a TMR element, a current flows in the film thickness direction of the ferromagnetic tunnel junction, and the tunnel barrier film may be destroyed by the voltage applied to the ferromagnetic tunnel junction. There is.

In contrast, a method has been proposed in which a spin-polarized current is caused to flow in the in-plane direction of the magnetic recording layer to move the domain wall, thereby reversing the magnetization of the recording layer in a direction corresponding to the direction of the write current (for example, , Patent Document 5, Patent Document 6, and Patent Document 7). This writing method by domain wall movement will be briefly described with reference to FIG.

FIG. 1 is a cross-sectional view showing a configuration of a typical magnetoresistive element 200. The magnetoresistive effect element 200 includes a magnetic recording layer 10, a pinned layer 12, and a tunnel barrier film 11 sandwiched between them. In FIG. 1, the x axis and the y axis are defined in parallel to the in-plane direction of the magnetic recording layer 10, and the z axis is defined in the film thickness direction of the magnetic recording layer 10. The magnetic recording layer 10 includes a first magnetization fixed region 101, a magnetization switching region 102, and a second magnetization fixed region 103. The first magnetization fixed region 101 is connected to the first boundary 21 of the magnetization switching region 102, and the magnetization direction is fixed in the + z direction. On the other hand, the second magnetization fixed region 103 is connected to the second boundary 22 of the magnetization switching region 102, and the magnetization direction is fixed in the −z direction (opposite to the magnetization of the first magnetization fixed region 101). The magnetizations of the first and second magnetization fixed regions 101 and 103 are antiparallel to each other.

On the other hand, the magnetization of the magnetization switching region 102 can be reversed in the film thickness direction of the magnetic recording layer 10 and is directed in either the + z direction or the −z direction in a steady state. In the magnetic recording layer 10, a domain wall (DW) is formed at one of the first boundary 21 and the second boundary 22.

The pinned layer 12 is formed so as to face the magnetization switching region 102 of the magnetic recording layer 10 with the tunnel barrier film 11 interposed therebetween. The pinned layer 12, the tunnel barrier film 11, and the magnetization switching region 102 form a ferromagnetic tunnel junction.

In addition, the magnetoresistive effect element 200 includes a first magnetization fixed layer 19 bonded to the first magnetization fixed region 101 and a second magnetization fixed layer 20 bonded to the second magnetization fixed region 103. The first magnetization fixed layer 19 is made of a magnetically hard ferromagnetic material and has a magnetization in the + z direction. Similarly, the second magnetization fixed layer 20 is made of a magnetically hard ferromagnetic material and has magnetization in the −z direction. The first magnetization fixed layer 19 plays a role of fixing the magnetization of the first magnetization fixed region 101 in the + z direction, and the second magnetization fixed layer 20 fixes the magnetization of the second magnetization fixed region 103 in the −z direction. Playing a role.

Data writing to the magnetoresistive effect element 200 is performed as follows. In the following, the state where the magnetization of the magnetization switching region 102 is oriented in the −z direction and the domain wall is located at the first boundary 21 is data “1”, the magnetization is oriented in the + z direction and the domain wall is located at the second boundary 22. The description will be made assuming that the state is associated with the data “0”. However, it will be apparent to those skilled in the art that the correspondence between the magnetization direction and the data value may be reversed.

When writing data “1” to the magnetic recording layer 10 in which data “0” is written, a write current flows from the first magnetization fixed region 101 to the second magnetization fixed region 103 through the magnetization switching region 102. It is. That is, spin-polarized electrons are injected from the second magnetization fixed region 103 into the magnetization switching region 102. As a result, the domain wall moves from the second boundary 22 to the first boundary 21 and the magnetization of the magnetization switching region 102 is directed in the −z direction, that is, data “1” is written.

On the other hand, when data “0” is written, the write current 2 flows from the second magnetization fixed region 103 to the first magnetization fixed region 101 through the magnetization switching region 102. That is, spin-polarized electrons are injected from the first magnetization fixed region 101 into the magnetization switching region 102. Thereby, the domain wall moves from the first boundary 21 to the second boundary 22, and the magnetization of the magnetization switching region 102 is directed in the + z direction, that is, data “0” is written. As described above, the domain wall (DW) in the magnetic recording layer 10 is formed between the first boundary 21 and the second boundary 22 of the magnetization switching region 102 by the current flowing between the first magnetization fixed region 101 and the second magnetization fixed region 103. Data is written by moving between them.

According to this method, since the current flowing at the time of writing does not penetrate the tunnel barrier film 11, deterioration of the tunnel barrier film 11 is suppressed. Further, since data writing is performed by the spin injection method, the write current is reduced as the memory cell size is reduced. Further, as the memory cell size is reduced, the moving distance of the domain wall (DW) is reduced, so that the write speed increases with the miniaturization of the memory cell.

FIG. 1 shows the case where the magnetic recording layer 10 has perpendicular magnetic anisotropy and the magnetization of the magnetic recording layer 10 is directed in the film thickness direction. Can also be oriented in the in-plane direction. A configuration in which the magnetization of the magnetic recording layer is directed in the in-plane direction is disclosed in Non-Patent Document 2, for example.

However, in order to reduce the write current, a configuration in which the magnetization of the magnetic recording layer 10 is directed in the film thickness direction is preferable to a configuration in which the magnetization of the magnetic recording layer is directed in the in-plane direction. The technique disclosed in Non-Patent Document 2 requires about 1 × 10 ⁸ [A / cm ² ] as the current density necessary for current-induced domain wall motion. In this case, for example, when the width of the magnetic recording layer 10 is 100 nm and the film thickness is 10 nm, the write current is 1 mA. On the other hand, Non-Patent Document 3 reports that the write current can be sufficiently reduced by using a material having perpendicular magnetic anisotropy as the magnetic recording layer. For this reason, when manufacturing MRAM using current-induced domain wall motion, it can be said that it is preferable to use a ferromagnetic material having perpendicular magnetic anisotropy as a layer in which domain wall motion occurs. Non-Patent Document 4 reports that current-induced domain wall motion was observed in a material having perpendicular magnetic anisotropy. By utilizing the current-induced domain wall motion phenomenon in the material having perpendicular magnetic anisotropy in this way, it is expected to provide an MRAM with a reduced write current.

One problem in manufacturing an MRAM that uses domain wall motion in the write operation is to stably introduce the domain wall into the layer where domain wall motion occurs. In Patent Document 5, as shown in FIG. 1, the magnetization directions of the first magnetization fixed region 101 and the second magnetization fixed region 103 are opposite to each other, so that the first boundary 21 or the second boundary 22 is obtained. A domain wall is formed. However, in practice, it is not easy to fix the magnetizations directed in opposite directions to each other while introducing the domain wall at a desired position.

In addition, when the first and second magnetization fixed layers 19 and 20 are used to fix the magnetization of the first and second magnetization fixed regions 101 and 103, the first and second magnetization fixed layers 19 and 20 There is also a problem that the domain wall movement may be hindered by the leakage magnetic field. It is not preferable from the viewpoint of stable operation that the domain wall movement is hindered.

In Non-Patent Document 4, as a method not using such a magnetization fixed layer, a method of forming a magnetic fine wire having a step structure by forming a magnetic fine wire and then removing a part thereof by etching is performed. In such a step-type structure, the reversal magnetic field in the thin region is smaller than the reversal magnetic field in the thick region, so that the thin region is reversed and the thick region is not reversed. Domain walls can be introduced by using a large magnetic field. Here, a magnetic field perpendicular to the substrate surface is used as the external magnetic field.

However, when such a step structure is provided, it is inevitable that the magnetic layer in the domain wall motion region is damaged by etching. By receiving the damage, the original magnetic characteristics of the magnetic layer may be deteriorated, which may hinder the domain wall movement.

US Pat. No. 5,640,343 US Pat. No. 6,545,906 JP 2005-505889 A Japanese Patent Laying-Open No. 2005-093488 JP 2005-191032 A International Publication No. WO2005 / 069368 JP 2006-73930 A

Yagami and Suzuki, Research Trends in Spin Transfer Magnetization Switching, Journal of Japan Society of Applied Magnetics, Vol. 28, No. 9, 2004. Physical Review Letters, vol. 92, number 7, p.077205, (2004). Journal of Applied Physics, vol. 103, p.07E718, (2008). Applied Physics Express, vol. 1, p.011301.

Therefore, an object of the present invention is to stably introduce a domain wall into a magnetic recording layer in an MRAM that uses domain wall motion for a write operation, and further prevent the domain wall motion from being hindered by a leakage magnetic field from the magnetization fixed layer. It is in.

In one aspect of the present invention, a magnetic memory includes an insulating layer, a magnetic recording layer formed on the insulating layer, a tunnel barrier layer, and a pinned layer. The magnetic recording layer has reversible magnetization, a magnetization reversal region facing the pinned layer across the tunnel barrier layer, and a first magnetization in which the magnetization direction is fixed in the first direction. It has a fixed region and a second magnetization fixed region that is bonded to the magnetization switching region and whose magnetization direction is fixed in the second direction. The insulating layer is provided with a step at a position corresponding to the boundary between the first magnetization fixed region and the magnetization switching region and a position corresponding to the boundary between the magnetization switching region and the second magnetization fixed region. In the layer, a first step is formed at the boundary between the first magnetization fixed region and the magnetization switching region, and a second step is formed at the boundary between the magnetization switching region and the second magnetization fixed region.

According to the present invention, there is provided a technique for stably introducing a domain wall into a magnetic recording layer and further preventing the domain wall movement from being hindered by a magnetization fixed layer in an MRAM that uses domain wall motion for a write operation. .

It is sectional drawing of the magnetoresistive effect element for demonstrating the data writing method in the conventional domain wall motion type | mold MRAM. It is sectional drawing which shows roughly the structure of MRAM of the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the magnetoresistive effect element of MRAM of 1st Embodiment. It is sectional drawing which shows the structure of the magnetoresistive effect element of MRAM of 2nd Embodiment. It is a perspective view which shows the structure of the magnetoresistive effect element of MRAM of 3rd Embodiment. It is sectional drawing which shows the structure of the magnetoresistive effect element of MRAM of 3rd Embodiment.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the accompanying drawings, the same or similar components are referred to by the same or corresponding reference numerals.

1. First embodiment

FIG. 2 is a cross-sectional view showing the structure of the main part of the MRAM according to the first embodiment of the present invention. FIG. 2 shows a portion corresponding to one memory cell of the MRAM. The memory cell generally includes a memory element portion 300 and a selection transistor portion 301. Hereinafter, the configuration of the memory element portion 300 and the selection transistor portion 301 will be described in detail. In the following description, an xyz orthogonal coordinate system is defined in the MRAM, and description will be made using the xyz orthogonal coordinate system.

First, the selection transistor portion 301 will be described. In a semiconductor substrate (for example, a p-type silicon substrate, a p-type well region) 41, an element isolation insulating layer 42 for forming an STI (Shallow Trench Isolation) structure is formed. In the region surrounded by the element isolation insulating layer 42, MOS transistors (n-channel MOS transistors) Tr1 and Tr2 used as read selection switches are formed. On the semiconductor substrate 41, a gate insulating film 43, a gate electrode 44, and a sidewall insulating layer 45 constituting the MOS transistors Tr1 and Tr2 are formed. The gate electrode 44 is provided so as to extend in the y-axis direction, and functions as a read word line for selecting a read cell during a read operation. Diffusion layers 46 and 47 are formed on both sides of the gate electrode 44. An insulating layer is laminated so as to cover the MOS transistors Tr1 and Tr2, and a via contact 48 for connecting to the diffusion layers 46 and 47 is formed so as to penetrate the insulating layer. As the via contact 48, for example, a tungsten plug can be used. Furthermore, a first metal layer is formed on the via contact 48 and the insulating layer. On the first metal layer, lands 49 and bit lines 50 for vertically stacking contacts are formed. An insulating layer is further laminated on the first metal layer, and a via contact 51 is formed so as to penetrate the insulating layer. Further, a second metal layer is formed on the via contact 51 and the insulating layer. Lands 52 for vertically stacking a plurality of contacts are formed in the second metal layer. An insulating layer is further laminated on the second metal layer, and a via contact 54 is formed so as to penetrate the insulating layer. A third metal layer is formed on the via contact 54 and the insulating layer. In the third metal layer, the first wiring 31 and the second wiring 34 that are both used as write word lines are formed. The first wiring 31 is connected to the magnetoresistive effect element 200 via the first via contact 32, and the second wiring 34 is connected to the magnetoresistive effect element 200 via the second via contact 33.

Next, the memory element portion 300 will be described. As shown in FIG. 2, the memory element portion 300 includes a magnetoresistive effect element 200. As shown in FIG. 3, the magnetoresistive effect element 200 includes a magnetic recording layer 10 that is a ferromagnetic layer, a pinned layer 12, and a tunnel barrier layer 11. The tunnel barrier layer 11 is sandwiched between the magnetic recording layer 10 and the pinned layer 12, and a magnetic tunnel junction (MTJ) is formed by the magnetic recording layer 10, the tunnel barrier layer 11, and the pinned layer 12. ing. The tunnel barrier layer 11 is a thin and nonmagnetic insulating layer, and is formed of, for example, an alumina oxide film (Al—Ox) or magnesium oxide (MgO) formed by oxidizing an Al film.

The magnetic recording layer 10 and the pinned layer 12 are ferromagnetic films having perpendicular magnetic anisotropy, and the magnetization directions of the magnetic recording layer 10 and the pinned layer 12 are directed in the film thickness direction. The magnetic recording layer 10 and the pinned layer 12 are made of, for example, iron (Fe), cobalt (Co), nickel (Ni), or an alloy containing any of these. When the magnetic recording layer 10 and the pinned layer 12 contain Pt and Pd, the perpendicular magnetic anisotropy can be stabilized. In addition to this, B, C, N, O, Al, Si, P, Ti, V, Cr, Mn, Cu, Zn, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Hf, Ta, W , Re, Os, Ir, Au, Sm, and the like can be added to the magnetic recording layer 10 and the pinned layer 12 so that desired magnetic characteristics are expressed. Specifically, materials usable as the magnetic recording layer 10 and the pinned layer 12 include Co, Co—Pt, Co—Pd, Co—Cr, Co—Pt—Cr, Co—Cr—Ta, and Co—Cr. -B, Co-Cr-Pt-B, Co-Cr-Ta-B, Co-V, Co-Mo, Co-W, Co-Ti, Co-Ru, Co-Rh, Fe-Pt, Fe-Pd Fe—Co—Pt, Fe—Co—Pd, Sm—Co and the like. In addition, perpendicular magnetic anisotropy can also be expressed by laminating a ferromagnetic film containing any one material selected from Fe, Co, and Ni and a nonmagnetic material film. Specifically, examples of the laminated body that can be used as the magnetic recording layer 10 and the pinned layer 12 include a Co / Pd laminated film, a Co / Pt laminated film, and an Fe / Au laminated film.

An antiferromagnetic layer 15 is stacked on the pinned layer 12 in order to increase the coercive force of the pinned layer 12 and pin the magnetization. That is, by laminating the antiferromagnetic layer 15 on the pinned layer 12, the pinned layer 12 exhibits unidirectional anisotropy due to the exchange interaction that acts between the pinned layer 12 and the antiferromagnetic layer 15. Can be fixed in one direction. As the antiferromagnetic layer 15, a manganese alloy antiferromagnetic film such as iron / manganese (FeMn), platinum / manganese (PtMn), nickel / manganese (NiMn), cobalt oxide (CoO), nickel oxide, etc. An oxide antiferromagnetic film such as a material (NiO) can be used.

In the present embodiment, the magnetic recording layer 10 has three regions: a first magnetization fixed region 101, a second magnetization fixed region 103, and a magnetization switching region 102. The first magnetization fixed region 101 and the second magnetization fixed region 103 have magnetizations whose directions are antiparallel to each other. On the other hand, the magnetization switching region 102 has magnetization that can be switched between the + z direction and the −z direction. That is, the magnetization of the magnetization switching region 102 is allowed to be parallel or antiparallel to the magnetization of the pinned layer 12. The magnetization switching region 102 is formed in a portion sandwiched between the first and second magnetization fixed regions 101 and 103. The pinned layer 12 is formed so as to overlap with the magnetization switching region 102. In other words, a part of the magnetization switching region 102 of the magnetic recording layer 10 faces the pinned layer 12 with the tunnel barrier layer 11 interposed therebetween, and the pinned layer 12, the tunnel barrier layer 11, and the magnetization switching region 102 are ferromagnetic. A tunnel junction is formed. In this embodiment, it is assumed that the magnetization of the pinned layer 12 is fixed in the + z direction. Further, it is assumed that the magnetization of the first magnetization fixed region 101 is fixed in the + z direction, and the magnetization of the second magnetization fixed region 103 is fixed in the −z direction.

As shown in FIG. 3, two steps: a first step 17 and a second step 18 are formed on the magnetic recording layer 10. In the present embodiment, the first step 17 becomes a boundary between the first magnetization fixed region 101 and the magnetization switching region 102, and the second step 18 becomes a boundary between the magnetization switching region 102 and the second magnetization fixed region 103. The first step 17 and the second step 18 are formed by forming a step in the insulating layer 56 and forming the magnetic recording layer 10 so as to cover the step. The height of the two steps 18 is substantially equal to or smaller than the film thickness of the magnetic recording layer 10. In FIG. 3, the step is formed so that the first magnetization fixed region 101 and the second magnetization fixed region 103 are located below the magnetization switching region 102 (that is, close to the substrate 41). A step may be formed so that the magnetization switching region 102 is positioned below the first magnetization fixed region 101 and the second magnetization fixed region 103. As will be described later, the formation of the first step 17 and the second step 18 in the magnetic recording layer 10 is important for stably introducing the domain wall into the magnetic recording layer.

The magnetoresistive effect element 200 further includes a first magnetization fixed layer 19 joined to the first magnetization fixed region 101 and a second magnetization fixed layer 20 joined to the second magnetization fixed region 103. The first magnetization fixed layer 19 has a function of fixing the magnetization of the first magnetization fixed region 101, and the second magnetization fixed layer 20 has a function of fixing the magnetization of the second magnetization fixed region 103. Yes. Both the first magnetization fixed layer 19 and the second magnetization fixed layer 20 are formed of a magnetically hard ferromagnetic material. In the first embodiment, the first magnetization fixed layer 19 and the second magnetization fixed layer 20 are configured so that the magnetization of the first magnetization fixed layer 19 is less likely to be reversed than the magnetization of the second magnetization fixed layer 20. . For example, the first magnetization fixed layer 19 is made of a magnetically harder material than the second magnetization fixed layer 20.

The magnetization direction of the first magnetization fixed layer 19 is directed to the + z direction similarly to the magnetization of the first magnetization fixed region 101, and the magnetization direction of the second magnetization fixed layer 20 is the same as that of the second magnetization fixed region 103. Similar to the magnetization, it is oriented in the -z direction. In FIG. 3, the first magnetization fixed layer 19 is directly bonded to the lower surface of the first magnetization fixed region 101, but may be bonded to the upper surface. Further, if the first magnetization fixed layer 19 is magnetically coupled to the first magnetization fixed region 101, it is not necessary to be directly joined. Similarly, in FIG. 3, the second magnetization fixed layer 20 may be directly bonded to the upper surface in FIG. 3, and the second magnetization fixed layer 20 is magnetically coupled to the first magnetization fixed region 101. If so, it is not necessary to be joined directly.

In the present embodiment, the end 19 a closest to the first step 17 of the first magnetization fixed layer 19 is formed away from the first step 17 that is the boundary between the first magnetization fixed region 101 and the magnetization switching region 102. As will be described later, the fact that the end 19a of the first magnetization fixed layer 19 is formed away from the first step 17 prevents the domain wall movement from being hindered by the leakage magnetic field from the first magnetization fixed layer 19. It is valid. The ends of the first magnetization fixed layer 20 other than the end 19a are formed so as to coincide with the ends of the first magnetization fixed region 101 or to be located outside thereof.

Similarly, the end 20 a closest to the second step 18 of the second magnetization fixed layer 20 is formed away from the second step 18 that is the boundary between the magnetization switching region 102 and the second magnetization fixed region 103. As will be described later, the fact that the end 20a of the second magnetization fixed layer 20 is formed away from the second step 18 prevents the domain wall movement from being hindered by the leakage magnetic field from the second magnetization fixed layer 20. It is valid. The ends of the second magnetization fixed layer 20 other than the end 20a are formed so as to coincide with the ends of the second magnetization fixed region 103 or to be located outside thereof.

In order to pass a write current, the memory element portion 300 is provided with a first wiring 31, a first via contact 32, a second via contact 33 and a second wiring 34. The first wiring 31 is connected to the first magnetization fixed layer 19 via the first via contact 32, and the second wiring 34 is connected to the second magnetization fixed layer 20 via the second via contact 33. Yes. The first wiring 31 and the second wiring 34 are formed of a material having a low electrical resistance such as aluminum (Al), copper (Cu), tungsten (W), or the like. In the present embodiment, the first wiring 31, the first via contact 32, the second via contact 33, and the second wiring 34 are disposed below the magnetic recording layer 10, but may be disposed above. It is.

The magnetoresistive effect element 200 of FIG. 3 is manufactured by the following processes, for example. After the first wiring 31 and the second wiring 34 are formed, an insulating layer 55 that covers the first wiring 31 and the second wiring 34 is formed. Further, after opening an opening in the insulating layer 55 by reactive etching (RIE) or the like, the opening is filled with a conductive material such as copper (Cu) or tungsten (W), whereby the first via contact 32 and the second via are formed. A contact 33 is formed. Further, after forming a ferromagnetic film to be the magnetization fixed layers 19 and 20 by sputtering or the like, unnecessary portions are removed by etching by ion milling or the like to form the first and second magnetization fixed layers 19 and 20. . Thereafter, an insulating film such as silicon oxide (SiO ₂ ) to be the insulating layer 56 is laminated, and then the insulating film is flattened by CMP (Chemical Mechanical Polishing) or the like to be formed on the first and second magnetization fixed layers 19 and 20. The insulating film is completely removed. Subsequently, an insulating film for forming a step is formed again, and this insulating film is processed by ion milling or reactive etching, so that it is positioned at a position corresponding to the first step 17 and the second step 18 of the magnetic recording layer 10. A step structure is formed. Thereby, the insulating layer 56 having a step is formed. Next, the first ferromagnetic film, the insulating film, the second ferromagnetic film, and the antiferromagnetic film that become the magnetic recording layer 10, the tunnel barrier layer 11, the pinned layer 12, and the antiferromagnetic layer 15 are continuously formed by sputtering or the like. Thus, the antiferromagnetic layer 15, the pinned layer 12, the tunnel barrier layer 11, and the magnetic recording layer 10 are formed in desired shapes by forming a film and processing it by ion milling or the like. Accordingly, the first and second magnetization fixed layers 19 and 20 and the first and second magnetization fixed regions 101 and 103 of the magnetic recording layer 10 are electrically and magnetically connected, and the pinned layer 12 and the tunnel barrier are also connected. The surface roughness of the portion where the layer 11 is formed is also suppressed by planarization. Thus, a desired magnetoresistance effect element 200 can be formed.

The introduction of the domain wall into the magnetic recording layer 10 is performed by the following procedure:

First, the first magnetization fixed region 101, the magnetization switching region 102, the second magnetization fixed region 103, the first magnetization fixed layer 19, and the second magnetization fixed layer are performed by performing a heat treatment while applying an external magnetic field in the + z direction. Twenty magnetizations are oriented in the + z direction.

Subsequently, in order to form a domain wall (DW) in the magnetic recording layer 10, an external magnetic field is applied in the −z direction. The magnitude of the magnetic field applied at this time depends on the magnetization of the magnetic recording layer 10 other than the portion magnetically coupled to the first magnetization fixed layer 19 of the first magnetic fixed region 101 and the magnetization of the second magnetization fixed layer 20. The magnetization of the first magnetization fixed layer 19 and the portion that is reversed and magnetically coupled to the first magnetization fixed layer 19 of the first magnetic fixed region 101 is set so as not to be reversed. Here, in the first embodiment, the first magnetization fixed layer 19 and the second magnetization fixed layer 20 are configured such that the magnetization of the first magnetization fixed layer 19 is less likely to be reversed than the magnetization of the second magnetization fixed layer 20. Note that it is composed. By applying this external magnetic field, a portion of the magnetic recording layer 10 that is magnetically coupled to the first magnetization fixed layer 19 of the first magnetic fixed region 101 forms one magnetic domain. The other part forms another magnetic domain. That is, a domain wall is generated at the position 21 corresponding to the end 19 a of the first magnetization fixed layer 19. Subsequently, in order to move the domain wall formed at the position 21 to the position of the first step 17, the external magnetic field is gradually increased. The magnitude of the magnetic field at this time is large enough to reverse the magnetization of the portion of the first magnetic pinned region 101 that is not magnetically coupled to the first magnetization pinned layer 19 and the second pinned magnetization is fixed. The magnetization of the region 103 is large enough not to reverse. In this way, the domain wall can be formed in the first step 17. Here, it should be noted that when the domain wall at the first step 17 moves toward the second step 18, the domain wall cannot move before the second step 18 because the second step 18 acts as a pin site. . Therefore, the domain wall can move only between the first step 17 and the second step 18.

In the introduction of the domain wall, it is important that the first step 17 and the second step 18 are provided in the magnetic recording layer 10 by forming a step in the insulating layer 56. In the structure in which the first step 17 and the second step 18 are provided in the magnetic recording layer 10 by forming a step in the insulating layer 56, etching for partially reducing the thickness of the magnetic recording layer 10 is not performed. Pinsite can be generated stably. Therefore, the domain wall can be stably introduced into the magnetic recording layer 10.

Next, the write operation in the first embodiment will be specifically described.

In the following, the state where the magnetization of the magnetization switching region 102 is oriented in the −z direction and the domain wall is located at the first step 17 is data “1”, and the magnetization is oriented in the + z direction and the domain wall is located at the second step 18. The description will be made assuming that the state is associated with the data “0”. However, it will be apparent to those skilled in the art that the correspondence between the magnetization direction and the data value may be reversed.

When writing data “1” to the magnetic recording layer 10 in which data “0” is written, a write current flows from the first magnetization fixed region 101 to the second magnetization fixed region 103 through the magnetization switching region 102. It is. The first wiring 31, the first via contact 32, the second via contact 33, and the second wiring 34 are used for supplying the write current. When a write current is passed, spin-polarized electrons are injected from the second magnetization fixed region 103 into the magnetization switching region 102. When spin-polarized electrons are injected, the domain wall at the second step 18 tends to move toward the first step 17 due to the spin transfer effect. That is, the magnetization direction of the magnetization switching region 102 tends to change from the + z direction to the −z direction. In this movement of the domain wall, the first step 17 acts as a pin site, so that the domain wall can move only to the first step 17. Therefore, when the domain wall moves to the first step 17 due to the spin transfer effect, the magnetization reversal stops, and as a result, the domain wall remains at the first step 17.

The same applies when data “0” is written to the magnetic recording layer 10 in which data “1” is written. When writing data “0”, a write current is passed from the second magnetization fixed region 103 to the first magnetization fixed region 101 through the magnetization switching region 102. That is, spin-polarized electrons are injected from the first magnetization fixed region 101 into the magnetization switching region 102. When spin-polarized electrons are injected, the domain wall at the first step 17 tends to move toward the second step 18 due to the spin transfer effect. That is, the magnetization direction of the magnetization switching region 102 tends to change from the −z direction to the + z direction. In this movement of the domain wall, the second step 18 acts as a pin site, so that the domain wall can move only up to the second step 18. Therefore, when the domain wall moves to the second step 18 due to the spin transfer effect, the magnetization reversal stops, and as a result, the domain wall remains at the second step 18.

As described above, the domain wall cannot move beyond the first step 17 and the second step 18 when writing either data “1” or “0”. On the other hand, in the MRAM of this embodiment, the first and second magnetization fixed layers 19 and 20 are located away from the first step 17 and the second step 18. Therefore, in the MRAM of this embodiment, the distance between the domain wall and the first and second magnetization fixed layers 19 and 20 can be increased. This is effective in reducing the influence of the leakage magnetic field from the magnetization fixed layers 19 and 20 and stabilizing the operation.

On the other hand, the TMR effect is used to read data recorded on the magnetic recording layer 10. At the time of data reading, a read current is supplied so as to flow between the pinned layer 12 and the magnetization switching region 102. In one embodiment, the read current is caused to flow from one of the first magnetization fixed region 101 and the second magnetization fixed region 103 to the pinned layer 12 via the magnetization switching region 102 and the tunnel barrier layer 11, and further to the pinned layer. The current flows through the readout wiring 35 formed on the layer 12. Instead, the read current flows from the read wiring 35 through the pinned layer 12 to the first magnetization fixed region 101 or the second magnetization fixed region 103 via the tunnel barrier layer 11 and the magnetization switching region 102. May be. The resistance value of the magnetoresistive effect element 200 is detected based on the read current or the potential difference generated by the read current, and the magnetization direction of the magnetization switching region 102, that is, the data recorded in the magnetic recording layer 10 is identified.

2. Second embodiment

FIG. 4 is a cross-sectional view showing the structure of the magnetoresistive effect element 200 according to the second embodiment. The magnetoresistive effect element 200 in the second embodiment generally has the same configuration as the magnetoresistive effect element 200 in the first embodiment. Also in the second embodiment, the magnetic recording layer 10 is provided with two steps: the first step 17 and the second step 18, and the domain wall movement is performed between the first step 17 and the second step 18.

The difference between the first embodiment and the second embodiment is that in the second embodiment, the magnetoresistive effect element 200 is provided with only one magnetization fixed layer. That is, while the first magnetization fixed layer 19 that is magnetically coupled to the first magnetization fixed region 101 is provided, no magnetization fixed layer is prepared for the second magnetization fixed region 103. In the present embodiment, the third contact via 36 is joined to the second magnetization fixed region 103 instead of the second magnetization fixed layer 20.

The magnetoresistive effect element 200 having the structure of FIG. 4 is manufactured, for example, by the following process. After the first wiring 31 and the second wiring 34 are formed, an insulating layer 55 that covers the first wiring 31 and the second wiring 34 is formed. Further, after opening an opening in the insulating layer 55 by reactive etching (RIE) or the like, the opening is filled with a conductive material such as copper (Cu) or tungsten (W), whereby the first via contact 32 and the second via are formed. A contact 33 is formed. Further, after forming a ferromagnetic film to be the first magnetization fixed layer 19 by sputtering or the like, unnecessary portions are removed by etching by ion milling or the like to form the first magnetization fixed layer 19. Thereafter, an insulating film such as silicon oxide (SiO ₂ ) to be the insulating layer 56 is laminated, and then the insulating film is planarized by CMP (Chemical Mechanical Polishing) or the like, and the insulating film on the first magnetization fixed layer 19 is completely formed. To remove. Subsequently, a third via contact 36 penetrating the insulating film is formed in the same manner as the first via contact 32 and the second via contact 33. Further, an insulating film for forming a step is formed again, and this insulating film is processed by ion milling or reactive etching, thereby forming a step at a position corresponding to the first step 17 and the second step 18 of the magnetic recording layer 10. A structure is formed. Thereby, the insulating layer 56 having a step is formed. Next, the first ferromagnetic film, the insulating film, the second ferromagnetic film, and the antiferromagnetic film that become the magnetic recording layer 10, the tunnel barrier layer 11, the pinned layer 12, and the antiferromagnetic layer 15 are continuously formed by sputtering or the like. Thus, the antiferromagnetic layer 15, the pinned layer 12, the tunnel barrier layer 11, and the magnetic recording layer 10 are formed in desired shapes by forming a film and processing it by ion milling or the like.

In the present embodiment, the introduction of the domain wall (DW) into the magnetic recording layer 10 is performed as follows:

First, initialization for fixing the magnetization of the first magnetization fixed layer 19 in a desired direction (in the + z direction in the present embodiment) is performed. Specifically, heat treatment is performed with an external magnetic field applied in the + z direction, and the magnetization of the first magnetization fixed layer 19 and the magnetization of the magnetic recording layer 10 are directed in the + z direction. As a result, the magnetization of the first magnetization fixed layer 19 and the magnetization of the first magnetization fixed region 101 magnetically coupled to the first magnetization fixed layer 19 are fixed in the + z direction.

Next, an external magnetic field in the −z direction is applied. The external magnetic field at this time is adjusted to be sufficiently smaller than the magnitude of reversing the magnetization of the first magnetization fixed layer 19 while reversing the magnetization of the magnetization reversal region 102 and the second magnetization fixed region 103 of the magnetic recording layer 10. . In the application of the external magnetic field, heat treatment is not necessarily required. As a result, the magnetization of the magnetic recording layer 10 other than the region magnetically bonded to the first magnetization fixed layer 19 is reversed, so that a domain wall is generated at the position 21 corresponding to the end 19 a of the first magnetization fixed layer 19. Subsequently, in order to move the domain wall formed at the position 21 to the position of the first step 17, the external magnetic field is gradually increased. The direction of the external magnetic field at this time is the + z direction, which is the same as the magnetization direction of the first magnetization fixed layer 19. By applying this external magnetic field, the region in the magnetic recording layer 10 where the magnetization is directed in the + z direction gradually expands. Therefore, the domain wall moves in the direction in which the magnetization increases the region in the + z direction, and as a result, moves toward the first step 17. The magnitude of the external magnetic field at this time is set such that the domain wall moves beyond the first step 17 and moves between the first step 17 and the second step 18, that is, into the magnetization switching region 102. The Thereafter, by applying an initialization current to the magnetization switching region 102, the domain wall that has moved to the middle of the magnetization switching region 102 is moved to the first step 17 or the second step 18.

The technical significance of applying the initialization current after moving the domain wall to the middle of the magnetization switching region 102 is as follows. If the application of the external magnetic field is stopped when the domain wall moves to the position of the first step 17, the domain wall stops at the position of the first step 17. In this case, as described above, the domain wall does not move beyond the step due to the formation of the pin site due to the step, and therefore, the domain wall may not move even when the write current is applied. The procedure of moving the domain wall to the first step 17 or the second step 18 by moving the domain wall to the middle of the magnetization switching region 102 and then applying the initialization current avoids such a problem. Is effective for generating the first step 17 or the second step 18.

In the introduction of the domain wall, it is important that the first step 17 and the second step 18 are provided in the magnetic recording layer 10 by forming a step in the insulating layer 56. In the structure in which the first step 17 and the second step 18 are provided in the magnetic recording layer 10 by forming a step in the insulating layer 56, etching for partially reducing the thickness of the magnetic recording layer 10 is not performed. Pinsite can be generated stably. Therefore, the domain wall can be stably introduced into the magnetic recording layer 10.

The write operation and read operation in the MRAM of the second embodiment are the same as those of the first embodiment. As in the first embodiment, a write current is passed between the first magnetization fixed region 101 and the second magnetization fixed region 103, and the domain wall is moved between the first step 17 and the second step 18. At this time, also in the second embodiment, the first magnetization pinned layer 19 is located away from the first step 17, and no magnetization pinned layer is provided around the second step 18, The influence of the leakage magnetic field from the single magnetization fixed layer 19 can be reduced, and the operation can be stabilized.

3. Third embodiment

FIG. 5 is a perspective view showing the structure of the magnetoresistive effect element 200 in the third embodiment, and FIG. 6 is a cross-sectional view. The magnetoresistive effect element 200 in the third embodiment has generally the same configuration as the magnetoresistive effect element 200 in the first and second embodiments. Also in the third embodiment, the magnetic recording layer 10 is provided with two steps: the first step 17 and the second step 18, and the domain wall movement is performed between the first step 17 and the second step 18.

The difference between the MRAM of the third embodiment and the first and second embodiments is that in the third embodiment, a magnetization fixed layer is used to fix the magnetization of the first magnetization fixed region 101 and the second magnetization fixed region 103. It is a point not to use. In the third embodiment, the first via contact 32 is directly bonded to the first magnetization fixed region 101, and the second via contact 33 is directly bonded to the second magnetization fixed region 103.

In addition, in the third embodiment, the pattern width of a part of the second magnetization fixed region 103 is larger than that of other parts. That is, as illustrated in FIG. 5, in the third embodiment, the second magnetization fixed region 103 includes the first portion 103a and the second portion 103b, and the width of the second portion 103b is the first portion. It is wider than the width of 103a. Here, the first portion 103a is a portion connected to the magnetization switching region 102 in the second magnetization fixed region 103, and the second portion 103b is a portion connected to the first portion 103a.

The magnetoresistive effect element 200 of FIGS. 5 and 6 is manufactured, for example, by the following process. After the first wiring 31 and the second wiring 34 are formed, an insulating layer 55 that covers the first wiring 31 and the second wiring 34 is formed. Further, after opening an opening in the insulating layer 55 by reactive etching (RIE) or the like, the opening is filled with a conductive material such as copper (Cu) or tungsten (W), whereby the first via contact 32 and the second via are formed. A contact 33 is formed. Subsequently, an insulating film for forming a step is formed again, and this insulating film is processed by ion milling or reactive etching, so that it is positioned at a position corresponding to the first step 17 and the second step 18 of the magnetic recording layer 10. A step structure is formed. Thereby, the insulating layer 55 having a step is formed. Next, the first ferromagnetic film, the insulating film, the second ferromagnetic film, and the antiferromagnetic film that become the magnetic recording layer 10, the tunnel barrier layer 11, the pinned layer 12, and the antiferromagnetic layer 15 are continuously formed by sputtering or the like. Thus, the antiferromagnetic layer 15, the pinned layer 12, the tunnel barrier layer 11, and the magnetic recording layer 10 are formed in desired shapes by forming a film and processing it by ion milling or the like. As described above, the magnetic recording layer 10 is processed so that the pattern width of a part of the second magnetization fixed region 103 is larger than that of the other part. Accordingly, the first and second magnetization fixed layers 19 and 20 and the first and second magnetization fixed regions 101 and 103 of the magnetic recording layer 10 are electrically and magnetically connected, and the pinned layer 12 and the tunnel barrier are also connected. The surface roughness of the portion where the layer 11 is formed is also suppressed by planarization. Thus, a desired magnetoresistance effect element 200 can be formed.

The introduction of the domain wall into the magnetic recording layer 10 in the third embodiment is performed as follows.

First, the magnetization direction of the magnetic recording layer 10 is aligned in one direction. In the present embodiment, an external magnetic field is applied in the −z direction, and the magnetizations of the first magnetization fixed region 101, the magnetization switching region 102, and the second magnetization fixed region 103 are directed in the −z direction. Next, an external magnetic field is applied in a direction opposite to the direction applied earlier (that is, the + z direction). The magnitude of the external magnetic field at this time is such a magnitude that the magnetization of the portion 103b where the pattern width of the second magnetization fixed region 103 is wide is not reversed. As shown in FIG. 5, the portion 103b of the second magnetization fixed region 103 has a pattern width larger than that of the other portion of the magnetic recording layer 10, and accordingly, a magnetic field (coercive force) necessary for magnetization reversal. Is larger than other parts. Therefore, it is possible not to reverse only the magnetization of the portion 103 b of the second magnetization fixed region 103. At this time, heat treatment is not necessarily required. Thereby, the magnetization of the portion 103a of the first magnetization fixed region 101, the magnetization switching region 102, and the second magnetization fixed region 103 of the magnetic recording layer 10 is reversed, and a domain wall is generated at the position 103c of the boundary between the portions 103a and 103b. The In order to move the domain wall to the second step 18, an external magnetic field is applied again in the -z direction. As a result, the region in which the magnetization is in the −z direction gradually expands, that is, the domain wall at the position 103 c moves in the direction of the second step 18 and finally reaches the second step 18. . At this time, as in the second embodiment, the external magnetic field moves so that the domain wall moves beyond the first step 17 and between the first step 17 and the second step 18, that is, in the middle of the magnetization switching region 102. It may be set to a large size. In this case, by subsequently applying an initialization current to the magnetization switching region 102, the domain wall that has moved to the middle of the magnetization switching region 102 is moved to the first step 17 or the second step 18.

Similar to the first and second embodiments, in introducing the domain wall, it is important that the first step 17 and the second step 18 are provided in the magnetic recording layer 10 by forming a step in the insulating layer 56. Plays. In the structure in which the first step 17 and the second step 18 are provided in the magnetic recording layer 10 by forming a step in the insulating layer 56, etching for partially reducing the thickness of the magnetic recording layer 10 is not performed. Pinsite can be generated stably. Therefore, the domain wall can be stably introduced into the magnetic recording layer 10.

The write operation and read operation in the MRAM of the third embodiment are the same as those in the first and second embodiments. As in the first embodiment, a write current is passed between the first magnetization fixed region 101 and the second magnetization fixed region 103, and the domain wall is moved between the first step 17 and the second step 18. At this time, in the third embodiment, since the magnetization fixed layer is not used, the problem that the domain wall movement due to the leakage magnetic field from the magnetization fixed layer is prevented in principle cannot occur. Therefore, in the third embodiment, the operation can be stabilized.

This application claims the priority on the basis of Japanese Patent Application No. 2009-86048 for which it applied on March 31, 2009, and takes in those the indications of all here.

Claims (7)

An insulating layer;
A magnetic recording layer formed on the upper surface of the insulating layer,
A tunnel barrier layer formed on the top surface of the magnetic recording layer ;
The pinned layer ,
A first magnetization fixed layer ,
The magnetic recording layer is
A magnetization reversal region having reversible magnetization and facing the pinned layer across the tunnel barrier layer;
A first magnetization fixed region bonded to the magnetization switching region and having a magnetization direction fixed in a first direction;
A second magnetization fixed region bonded to the magnetization switching region and having a magnetization direction fixed in a second direction;
The first magnetization fixed layer is bonded to the lower surface of the first magnetization fixed region of the magnetic recording layer to fix the magnetization of the first magnetization fixed region,
Wherein the insulating layer, the first magnetization fixed region and the position corresponding to the boundary between the magnetization inversion region, and a step is provided at a position corresponding to the boundary between said magnetization reversal region and the second magnetization fixed region Thereby, in the magnetic recording layer, a first step is formed at the boundary between the first magnetization fixed region and the magnetization switching region, and a second step is formed at the boundary between the magnetization switching region and the second magnetization fixed region. A step is formed ,
A magnetic memory in which an end of the first magnetization fixed layer is located away from the first step . The magnetic memory according to claim 1 ,
Furthermore,
A second magnetization fixed layer that is bonded to the lower surface of the second magnetization fixed region of the magnetic recording layer and fixes the magnetization of the second magnetization fixed region;
The magnetic memory, wherein an end of the second magnetization fixed layer is located away from the second step. The magnetic memory according to claim 1 or 2,
An end of the first magnetization fixed layer is located away from the step at a position corresponding to a boundary between the first magnetization fixed region and the magnetization switching region of the insulating layer.
Magnetic memory. The magnetic memory according to claim 2,
An end of the first magnetization fixed layer is located away from the step located at a position corresponding to a boundary between the first magnetization fixed region and the magnetization switching region of the insulating layer;
An end of the second magnetization fixed layer is located away from the step at a position corresponding to a boundary between the second magnetization fixed region and the magnetization switching region of the insulating layer.
Magnetic memory. The magnetic memory according to claim 3, wherein
A portion of the upper surface of the insulating layer that is in contact with the magnetization switching region is located higher than a portion of the upper surface of the insulating layer that is in contact with the first magnetization fixed region and the second magnetization fixed region.
Magnetic memory. The magnetic memory according to any one of claims 1 to 5,
A magnetic memory in which a height of the first step and the second step is substantially equal to or smaller than a film thickness of the magnetic recording layer. The magnetic memory according to any one of claims 1 to 6,
The magnetic memory in which the first magnetization fixed region, the second magnetization fixed region, and the magnetization switching region have the same film thickness.

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