KR20120057545A - Magnetic memory including memory cells incorporating data recording layer with perpendicular magnetic anisotropy film - Google Patents

Abstract

PURPOSE: A magnetic memory including a memory cell with a data recording layer with perpendicular magnetic anisotropy films is provided to sufficiently reinforce magnetic coupling between the data recording layer and a magnetization fixed layer. CONSTITUTION: A magnetization fixed layer includes perpendicular magnetic anisotropy and a fixed magnetization direction thereof. An under layer(40) is formed on the upper sides of an interlayer dielectric and the magnetization fixed layer. A data recording layer(10) is formed on the upper side of the under layer and has perpendicular magnetic anisotropy. The under layer includes a first magnetic under layer and a non-magnetic under layer. The non-magnetic under layer is formed on the first magnetic under layer.

Description

MAGNETIC MEMORY INCLUDING MEMORY CELLS INCORPORATING DATA RECORDING LAYER WITH PERPENDICULAR MAGNETIC ANISOTROPY FILM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic memory, and more particularly, to a magnetic memory using a magnetic film having Perpendicular Magnetic Anisotropy (PMA) as a data recording layer in each memory cell. It is about.

Magnetic memory or magnetic random access memory (MRAM) is a nonvolatile memory that achieves high speed operation and infinite rewrite immunity. This facilitates the practical use of MRAM in certain applications and facilitates development to expand the versatility of MRAM. The magnetic memory uses a magnetic film as a memory element, and stores data as the magnetization direction of the magnetic film. When recording desired data on the magnetic film, the magnetization of the magnetic film is switched in the direction corresponding to that data. Although various methods for switching the magnetization direction have been proposed, all of the proposed methods are identical in that a current (or write current) is used. It is very important to reduce the write current in realizing the practical use of MRAM. The importance of reducing the write current is discussed, for example, in “MRAM Cell Technology for Over 500-MHz SoC” by N. Sakimura et al., IEEE Journal of Solid State Circuits, Vol. 42, No. 4, pages 830-838, 2007 It is becoming.

One approach to reducing write current is to use "current driven domain wall motion" in writing data. A. As described in Yamaguchi et al., “Real-Space Observation of Current-Driven Domain Wall Motion in Submicron Magnetic Wires,” Physical Review Letter, Vol. 92, No. 7, 077205, 2004. When current flows, the domain wall moves in the direction of the conduction electrons. Thus, by flowing a recording current through the data recording layer, the domain wall moves in the direction corresponding to that current direction, thereby recording the desired data. MRAM based on current driven domain wall movement is disclosed, for example, in Japanese Patent Application Laid-Open No. 2005-191032 A.

Furthermore, magnetic shift registers based on spin injection are disclosed in US Pat. No. 6,834,005. This magnetic shift register records data by using domain walls formed in a magnetic body. When current is injected through the domain walls of a magnetic body divided into a large number of regions (or magnetic domains), the domain walls are driven by the current. The magnetization direction of each area is defined as recording data. Such a magnetic shift register is used to write a large amount of serial data, for example.

It is known in the art that by using a magnetic film having perpendicular magnetic anisotropy as the data recording layer in a magnetic memory which achieves data recording based on current driven domain wall movement, the recording current can be further reduced. Such techniques are disclosed, for example, in "Micromagnetic analysis of current driven domain wall motion in nanostrips with perpendicular magnetic anisotropy" by S. Fukami et al., Journal of Applied Physics, Vol. 103, 07E718, (2008).

In addition, WO2009 / 001706 A1 discloses a magnetic memory in which a magnetic film having perpendicular magnetic anisotropy is used as a data recording layer and data recording is achieved by current driven domain wall movement. 1 is a schematic cross-sectional view of a magnetoresistance effect element 200 incorporated in the disclosed magnetic memory. The magnetoresistive effect element 200 includes a data recording layer 110, a spacer layer 120, and a reference layer 130. The data recording layer 110 is formed of a magnetic film having perpendicular magnetic anisotropy. The spacer layer 120 is formed of a nonmagnetic dielectric layer. The reference layer 130 is formed of a magnetic layer having fixed magnetization.

The data recording layer 110 includes a pair of magnetization fixing regions 111a and 111b and a magnetization free region 113. The magnetization fixing regions 111a and 111b are disposed at both ends of the magnetization free region 113. The magnetizations of the magnetization fixing regions 111a and 111b are fixed in the opposite directions (or antiparallel) by the magnetization fixing layers 115a and 115b, respectively. More specifically, the magnetization direction of the magnetization fixing region 111a is fixed in the + z direction by magnetic coupling with the magnetization fixing layer 115a, and the magnetization direction of the magnetization fixing region 111b is the magnetization fixing layer 115b. It is fixed in the -z direction by magnetic coupling. On the other hand, the magnetization direction of the magnetization free region 113 is invertible between the + z direction and the -z direction by the write current flowing from one of the magnetization fixing regions 111a and 111b to the other. As a result, domain walls 112a or 112b are formed in the data recording layer 110 in accordance with the magnetization direction of the magnetization free region 113. The data is stored as the magnetization direction of the magnetization free area 113. Data can be thought of as being stored as the location of the domain wall (indicated by reference numeral 112a or 112b).

The reference layer 130, the spacer layer 120, and the magnetization free layer 113 of the data recording layer 110 form a magnetic tunnel junction (MTJ). The resistance of the MTJ changes in accordance with the magnetization direction of the magnetization free region 113, that is, the data recorded in the data recording layer 110. The data is read out as the magnitude of the resistance of the MTJ.

One important problem of a magnetic memory using a data recording layer having perpendicular magnetic anisotropy is to enhance the vertical magnetic anisotropy of the data recording layer. When a Co / Ni film stack (a stack in which thin Co films and Ni films are alternately laminated) is used as the data recording layer, for example, by forming a Co / Ni film stack to show a high fcc (111) orientation, Perpendicular magnetic anisotropy can be achieved; However, forming a Co / Ni film stack with a sufficiently high fcc (111) orientation is not so easy.

Japanese Patent Application Laid-Open No. 2006-114162 A discloses a vertical magnetic recording medium including an adhesive layer, a soft magnetic underlayer, an intermediate layer, and a vertical recording layer, laminated in series on a substrate. This patent document discloses a technique for improving the surface flatness and magnetic properties of a soft magnetic underlayer, and for further enhancing adhesion to a substrate. Specifically, the pressure-sensitive adhesive layer is composed of first and second lower layers. The first lower layer is formed of an alloy of at least two elements selected from the group consisting of nickel (Ni), aluminum (Al), titanium (Ti), tantalum (Ta), chromium (Cr), and cobalt (Co), The second lower layer is formed of an amorphous alloy or metal tantalum comprising Ta doped with at least one element selected from the group consisting of Ni, Al, Ti, Cr, and Zr.

F.J.A. "Vertical Magnetic Anisotropy and Coercivity of Co / Ni Multilayers" by den Broeder et al., IEEE Transactions on Magnetics, Vol. 28, No. 5, pages 2760-2765, (1992), deposited films on glass substrates without any underlying layers. The results show strong anisotropy in the in-plane direction, and a lower layer is needed to achieve perpendicular magnetic anisotropy. This non-patent document discloses that a gold (Au) film having a (111) orientation is a good underlayer. It should be noted that the underlayer disclosed in this non-patent document is formed of a nonmagnetic material and has a thickness of 20 nm or more.

The use of a thick nonmagnetic layer as a lower layer as disclosed in this non-patent document is preferable for the magnetic memory shown in Fig. 1 in which the magnetization of the magnetization pinning area of the data recording layer is fixed by a magnetization pinning layer formed below the data recording layer. Not. For example, when a lower layer is used in the magnetic memory shown in Fig. 1, the lower layer is inserted between the data recording layer 110 and the magnetization pinned layers 115a and 115b. In this case, the magnetic coupling between the data recording layer 110 and the magnetization pinning layers 115a and 115b is broken by the insertion of a thick nonmagnetic layer as a lower layer, resulting in loose magnetization of the magnetization pinning regions 111a and 111b. . This is undesirable for normal operation of the magnetic memory.

It is therefore an object of the present invention to provide a magnetic memory including a data recording layer having perpendicular magnetic anisotropy, wherein the data recording layer has a sufficiently strong perpendicular magnetic anisotropy and is disposed below the data recording layer and the data recording layer. Magnetic coupling between the magnetized pinned layers is sufficiently strengthened.

In one aspect of the present invention, a magnetic memory includes: a magnetizing pinned layer having perpendicular magnetic anisotropy and having a fixed magnetization direction of the magnetized pinned layer; Interlayer dielectrics; An underlayer formed on the upper surfaces of the magnetized pinned layer and the interlayer dielectric; And a data recording layer formed on the upper surface of the lower layer and having vertical magnetic anisotropy. The lower layer is a first magnetic lower layer; And a nonmagnetic underlayer formed on the first magnetic underlayer. The first magnetic underlayer is formed to a thickness such that the first magnetic underlayer does not exhibit in-plane magnetic anisotropy in a portion of the first magnetic underlayer formed on the interlayer dielectric.

In another aspect of the present invention, a magnetic memory includes: a magnetization pinned layer having perpendicular magnetic anisotropy; Interlayer dielectric; A lower layer formed on the upper surfaces of the magnetized pinned layer and the interlayer dielectric; And a data recording layer formed on the upper surface of the lower layer and having perpendicular magnetic anisotropy. The magnetization pinned layer has a fixed magnetization direction. The lower layer is a first magnetic lower layer; And a nonmagnetic underlayer formed on the first magnetic underlayer. The first magnetic underlayer contains NiFe as a major constitution and includes at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V. The thickness of the first magnetic underlayer is in the range of 0.5 to 3 nm.

In still another aspect of the present invention, a magnetic memory includes: a magnetizing pinned layer having perpendicular magnetic anisotropy and having a fixed magnetization direction of the magnetized pinned layer; Interlayer dielectric; A lower layer formed on the upper surfaces of the magnetized pinned layer and the interlayer dielectric; And a data recording layer formed on the upper surface of the lower layer and having perpendicular magnetic anisotropy. The lower layer is a first magnetic lower layer; And a nonmagnetic underlayer formed on the first magnetic underlayer. The first magnetic underlayer contains Co or Fe as a main component and includes at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V. The thickness of the first magnetic underlayer is in the range of 0.5 to 3 nm.

In yet another aspect of the invention, a magnetic memory includes: a ferromagnetic underlayer formed of a magnetic material; A nonmagnetic intermediate layer disposed on the lower layer; A ferromagnetic data recording layer formed on the intermediate layer and having perpendicular magnetic anisotropy; A reference layer connected to the data recording layer through a nonmagnetic layer; And first and second magnetized pinned layers disposed to contact the lower surface of the lower layer. The data recording layer includes: a magnetization free region having invertible magnetization and opposing the reference layer; A first magnetization fixing region coupled to the first boundary of the magnetization free region and having magnetization fixed in the first direction; And a second magnetization fixing region coupled to the second boundary of the magnetization free region and having magnetization fixed in a second direction opposite to the first direction. The intermediate layer is formed of a Ta film having a thickness of 0.1 to 2.0 nm.

The present invention provides a magnetic memory including a data recording layer having vertical magnetic anisotropy, wherein the data recording layer has a sufficiently strong vertical magnetic anisotropy, and a magnetic field between the data recording layer and the magnetization pinning layer disposed below the data recording layer. The bond is sufficiently strengthened.

These and other objects, advantages, and features of the present invention will become more apparent from the following description of certain preferred embodiments, taken in conjunction with the accompanying drawings, in which:
1 is a cross-sectional view showing an exemplary configuration of a conventional magnetoresistance effect element.
Fig. 2 is a sectional view schematically showing an exemplary configuration of a magnetoresistive element of the first embodiment of the present invention.
3A is a diagram schematically showing a state of a magnetoresistive element in which data "0" is recorded.
Fig. 3B is a diagram schematically showing the state of the magnetoresistive element in which data " 1 " is recorded.
4A is a graph showing the size change of magnetization of a NiFeW film with respect to film thickness.
4B is a graph showing the size change of magnetization of a NiFeZr film with respect to film thickness.
4C is a graph showing the size change of magnetization of a NiFeTa film with respect to film thickness.
FIG. 5A is a table showing the change in Pt film thickness of the bonding field acting through the Pt film corresponding to the nonmagnetic underlayer.
FIG. 5B is a table showing the change in Pd film thickness of the bonding field acting through the Pd film corresponding to the nonmagnetic underlayer.
Fig. 5C is a table showing the change in the Ir film thickness of the bonding field acting through the Ir film corresponding to the nonmagnetic underlayer.
Fig. 6A is a graph showing the magnetic field curve of the data recording layer of Embodiment 1 of the first embodiment when the second magnetic underlayer is not provided.
Fig. 6B is a graph showing the magnetic field curve of the data recording layer of Embodiment 1 of the first embodiment for the case where one Co film and one Pt film are laminated in the second magnetic underlayer.
Fig. 6C is a graph showing the magnetic field curve of the data recording layer of Embodiment 1 of the first embodiment for the case where two Co films and two Pt films are laminated in the second magnetic underlayer.
Fig. 6D is a graph showing the magnetic field curve of the data recording layer of Embodiment 1 of the first embodiment for the case where three Co films and three Pt films are laminated in the second magnetic underlayer.
FIG. 6E is a graph showing a magnetization curve of a Co / Pt film stack formed on a Pt film corresponding to a nonmagnetic underlayer.
7 is a graph showing the definition of a saturated field H _s .
FIG. 8 is a graph showing a change in saturation field H _s with respect to the number of Co and Pt films of the second magnetic underlayer of Embodiment 1 of Example 1; FIG.
9 is a graph that shows a relation between the first embodiment in the embodiment 1, the second number of magnetic Co and the Pt film in the lower layer, bubble cosmetic H _s and the recording current.
10 is a cross-sectional view showing a structure of Comparative Example 1 of the first embodiment.
FIG. 11A shows the thickness ratio and saturation field H _s of the Co and Pt films of the second magnetic underlayer in Embodiment 1 of the first embodiment, in which a NiFeW film is used as the first magnetic underlayer and the Pt film is used as the nonmagnetic underlayer. Graph showing the relationship between
FIG. 11B shows the thickness ratio and saturation field H _s of the Co and Pt films of the second magnetic underlayer in Embodiment 1 of the first embodiment, in which a NiFeV film is used as the first magnetic underlayer and the Au film is used as the nonmagnetic underlayer. Graph showing the relationship between
Fig. 12 is a sectional view schematically showing an exemplary configuration of a magnetoresistive element of the second embodiment of the present invention.
13A is a graph showing the dependence of the magnetic tunnel junction on the material of the first magnetic underlayer.
FIG. 13B is a graph showing a magnetic field curve showing a bonding state between a data recording layer and a magnetized pinned layer when the first magnetic underlayer is formed of a NiFeZr film. FIG.
FIG. 13C is a graph showing a magnetic field curve showing a bonding state between a data recording layer and a magnetized pinned layer when the first magnetic underlayer is formed of a NiFeZr film. FIG.
FIG. 13D is a graph showing a magnetic field curve indicating a bonding state between a data recording layer and a magnetized pinned layer when the first magnetic underlayer is formed of a CoTa film; FIG.
Fig. 13E is a graph showing a magnetic field curve indicating a bonding state between a data recording layer and a magnetized pinned layer when the first magnetic underlayer is formed of a CoTa film.
14A is a diagram showing a change in the magnetic field curve with respect to the thickness of the first magnetic underlayer when the first magnetic underlayer is formed of a CoTa film.
14B is a view showing a change in the magnetic field curve with respect to the thickness of the first magnetic underlayer when the first magnetic underlayer is formed of a CoTa film.
Fig. 15A is a graph showing the magnetic field curve of the data recording layer when the second magnetic underlayer is not provided in the second embodiment.
Fig. 15B is a graph showing the magnetic field curve of the data recording layer for the case where the number of Co and Pt films in the second magnetic underlayer is one in the second embodiment.
Fig. 15C is a graph showing the magnetic field curve of the data recording layer when the number of Co and Pt films in the second magnetic underlayer is two in the second embodiment.
16 is the graph showing the change in the make-up H 2 PO _s for the number of the magnetic underlayer of Co and the Pt film in the second embodiment.
17 is the graph showing the relation between the second embodiment in a second number of magnetic Co and Pt loaded on the lower layer, bubble cosmetic H _s and the recording current.
Figure 18, the first magnetic film CoTa in the second embodiment that is used as a lower layer, the second graph showing a relationship between thickness ratios and fabric makeup H _s of the lower layer of magnetic Co and Pt film.
19A and 19B are sectional views schematically showing the exemplary structure of a magnetoresistive element of the third embodiment of the present invention.
20A and 20B are cross-sectional views schematically showing an exemplary structure of the magnetoresistive element of Comparative Example 1. FIG.
21A is a graph showing an exemplary magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in FIGS. 20A and 20B.
21B is a graph showing an example magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in FIGS. 20A and 20B.
Fig. 22A is a graph showing an exemplary magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in Figs. 20A and 20B after the data recording layer is thermally annealed.
Fig. 22B is a graph showing an exemplary magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in Figs. 20A and 20B after the data recording layer is heat-treated.
23A and 23B are sectional views schematically showing the exemplary structure of the magnetoresistive effect element of Embodiment 1;
24A is a graph showing an exemplary magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in FIGS. 23A and 23B.
FIG. 24B is a graph showing an exemplary magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in FIGS. 23A and 23B.
25 is a graph showing the relationship between the thickness of an intermediate layer, the temperature of heat treatment, and the saturation field.
Fig. 26 is a graph showing an exemplary magnetization curve for the case where an external magnetic field is applied to the data recording layer of the structure shown in Figs. 23A and 23B.
Fig. 27 is a block diagram showing an exemplary configuration of a magnetic memory in one embodiment of the present invention.
Fig. 28 is a circuit diagram schematically showing an exemplary configuration of a memory cell in one embodiment of the present invention.

The invention will now be described with reference to embodiments. Those skilled in the art will recognize that many alternative embodiments may be achieved using the teachings of the present invention and that the present invention is not limited to the embodiments illustrated for explanatory purposes.

In the following, embodiments of the present invention are described with reference to the accompanying drawings.

First Example

2 is a cross-sectional view schematically showing an exemplary configuration of the magnetoresistive element 100 in the first embodiment of the present invention. The magnetoresistive effect element 100 includes a data recording layer 10, a spacer layer 20, a reference layer 30, a lower layer 40, and magnetization pinned layers 50a and 50b.

The data recording layer 10 is formed of a ferromagnetic material having perpendicular magnetic anisotropy. The data recording layer 10 stores the data as its magnetization direction is reversible and its magnetization state. In detail, the data recording layer 10 includes a pair of magnetization fixing regions 11a and 11b and a magnetization free region 13.

The magnetization fixing regions 11a and 11b are disposed adjacent to the magnetization free region 13. The magnetizations of the magnetization fixing regions 11a and 11b are fixed in opposite directions (or antiparallel) to each other. In the example shown in Fig. 2, the magnetization direction of the magnetization fixing region 11a is fixed in the + z direction and the magnetization direction of the magnetization fixing region 11b is fixed in the -z direction.

The magnetization of the magnetization free region 13 is reversible between the + z direction and the -z direction. Thus, domain walls are formed in the data recording layer 10 in accordance with the magnetization direction of the magnetization free area 13. Specifically, as shown in FIG. 3A, when the magnetization direction of the magnetization free region 13 is directed in the + z direction, a domain wall 12 is formed between the magnetization free region 13 and the magnetization fixing region 11b. Is formed. On the other hand, when the magnetization direction of the magnetization free region 13 is directed in the -z direction, the domain wall 12 is formed between the magnetization free region 13 and the magnetization fixing region 11a. That is, the data recording layer 10 includes a domain wall 12, and the position of the domain wall 12 depends on the magnetization direction of the magnetization free area 13.

The spacer layer 20 is disposed adjacent to the data recording layer 10. The spacer layer 20 is disposed in contact with at least the upper surface of the magnetization free region 13 of the data recording layer 10. The spacer layer 20 is formed of a nonmagnetic dielectric material.

The reference layer 30 is disposed in contact with the top surface of the spacer layer 20. That is, the reference layer 30 is coupled to the data recording layer 10 (magnetization free region 13) via the spacer layer 20. As in the case of the data recording layer 10, the reference layer 30 is also formed of a ferromagnetic material having perpendicular magnetic anisotropy, and its magnetization direction is fixed in the + z or -z direction. In the example of FIG. 2, the magnetization direction of the reference layer 30 is fixed in the + z direction.

The magnetization free region 13, spacer layer 20, and reference layer 30 of the above-described data recording layer 10 form a magnetic tunnel junction MTJ. That is, the data recording layer 10 (magnetization free region 13), spacer layer 20, and reference layer 30 function as free layers, barrier layers, and pinned layers, respectively, in the MTJ.

The lower layer 40 is disposed on the lower surface of the data recording layer 10 (facing the substrate). The lower layer 40 is used to improve the crystal orientation of the data recording layer 10 to achieve strong perpendicular magnetic anisotropy in the data recording layer 10. The structure and function of the lower layer 40 will be discussed in detail later.

The magnetized pinned layers 50a and 50b are formed of a magnetically-strong ferromagnetic material having perpendicular magnetic anisotropy, and the magnetization directions of the magnetized pinned layers 50a and 50b are fixed in the + z and -z directions, respectively. The magnetization pinning layers 50a and 50b are used to fix the magnetization of the magnetization fixing regions 11a and 11b of the data recording layer 10. The magnetization of the magnetized pinned region 11a is fixed by magnetic coupling with the magnetized pinned layer 50a, and the magnetization of the magnetized pinned region 11b is fixed by magnetic coupling with the magnetized pinned layer 50b. In this embodiment, the magnetization pinned layers 50a and 50b are embedded in grooves formed on the interlayer dielectric 60. In this embodiment, CoPt alloy films or Co / Pt film stacks (film stacks in which thin Co films and Pt films are alternately laminated) are used as the magnetization pinned layers 50a and 50b. These strong magnetic materials show strong perpendicular magnetic anisotropy.

Interlayer dielectric 60 is generally a dielectric film for interlayer separation used in semiconductor integrated circuits. SiO _x film, SiN film, or a film stack of these films is used as the interlayer dielectric 60.

It should be noted that the electrode layers (not shown) are electrically connected to the magnetization fixing regions 11a and 11b of the data recording layer 10, respectively. These electrode layers are used to introduce a recording current into the data recording layer 10. In one embodiment, the electrode layers may be connected to the magnetization pinning regions 11a and 11b of the data recording layer 10 through the magnetization pinning layers 50a and 50b described above. Further, another electrode layer (not shown) is electrically connected to the reference layer 30.

In the magnetoresistive effect element 100, two magnetization states of the data recording layer 10, that is, two memory states corresponding to two allowed positions of the domain wall of the data recording layer 10 are allowed. When the magnetization direction of the magnetization free area 13 of the data recording layer 10 is directed in the + z direction as shown in Fig. 3A, the domain wall at the boundary between the magnetization free area 13 and the magnetization fixed area 11b. (12) is formed. In this case, the magnetization directions of the magnetization free region 13 and the reference layer 30 are parallel to each other. Thus, the resistance of the MTJ is relatively reduced. This magnetization state is correlated with, for example, the memory state of data "0".

When the magnetization direction of the magnetization free area 13 of the data recording layer 10 is directed in the -z direction as shown in Fig. 3B, the domain wall at the boundary between the magnetization free area 13 and the magnetization fixed area 11a Is formed. In this case, the magnetization directions of the magnetization free region 13 and the reference layer 30 are anti-parallel. Thus, the resistance of the MTJ is relatively increased. This magnetization state is correlated with, for example, the memory state of data "1".

It should be noted that the correlation between the magnetization state of the data recording layer 10 and the two memory states is not limited to the one described above. The data recording layer 10 includes a domain wall 12, and the position of the domain wall 12 corresponds to the magnetization direction of the magnetization free area 13. As a result, the data recording layer 10 stores data as the position of the domain wall 12.

In the magnetoresistive effect element 100 of this embodiment, data writing is achieved by using current driven domain wall movement. When the magnetoresistive element 100 previously stores data "0" (in this case, the magnetization direction of the magnetization free region 13 and the reference layer 30 are parallel), the data is provided to the magnetoresistive element 100. In order to write " 1 ", a write current flows from the magnetization fixed region 11a to the magnetization fixed region 11b through the magnetization free region 13. In this case, conduction electrons move from the magnetization fixing region 11b to the magnetization fixing region 11a through the magnetization free region 13. As a result, a spin transfer torque (STT) is applied on the domain wall 12 located at the boundary between the magnetization fixing region 11b and the magnetization free region 13, and the domain wall 12 is the magnetization fixing region. Go to (11a). That is, current driven domain wall movement occurs. When the write current passes through the boundary between the magnetized fixed region 11a and the magnetized free region 13, the current density of the write current in the magnetized fixed region 11a decreases. Thus, the movement of the domain wall 12 stops near the boundary. In this way, the domain wall 12 moves to the vicinity of the boundary between the magnetized fixed area 11a and the magnetized free area 13 to achieve data recording of data "1".

On the other hand, when the magnetoresistive element 100 previously stores the data " 1 " (in this case, the magnetization directions of the magnetization free region 13 and the reference layer 30 are antiparallel). In order to write data " 0 " in < RTI ID = 0.0 > In this case, the conduction electrons move from the magnetization fixing region 11a to the magnetization fixing region 11b through the magnetization free region 13. As a result, a spin transfer torque is applied on the domain wall 12 located at the boundary between the magnetization fixing region 11a and the magnetization free region 13, and the domain wall 12 moves toward the magnetization fixing region 11b. That is, current driven domain wall movement occurs. When the write current passes through the boundary between the magnetized fixed region 11b and the magnetized free region 13, the current density of the write current in the magnetized fixed region 11b decreases. Thus, the movement of the domain wall 12 stops near the boundary. In this way, the domain wall 12 moves near the boundary between the magnetically fixed region 11b and the magnetization free region 13 to achieve a data write of data " 0 ".

When data "0" is recorded with data "0" previously stored, or when data "1" is recorded with data "1" previously stored, no change occurs in the magnetization state. It should be noted. This means that the magnetoresistive effect element 100 is adapted for overwriting.

Data reading is achieved by using the Tunneling MagnetoResistive (TMR) effect. Specifically, in reading data, a read current flows through the MTJ (composed of the magnetization free region 13, the spacer layer 20, and the reference layer 30) of the data recording layer 10. The direction of the read current can be reversed. When data " 0 " is stored in the magnetoresistive effect element 100, the resistance of the MTJ is relatively reduced. On the other hand, when data " 1 " is stored in the magnetoresistive effect element 100, the resistance of the MTJ is relatively increased. Thus, data can be identified by detecting the resistance of the MTJ.

Next, a preferable structure of the data recording layer 10 will be described. Desired characteristics of the data recording layer 10 include small saturation magnetization and large spin polarizability. As disclosed in A. Thiaville et al., “Domain wall motion by spin-polarized current: a micromagnetic study,” Journal of Applied Physics, Vol. 95, No. 11, pages 7049-7051, 2004, the current driven domain wall movement is The larger the parameter gμ _B P / 2eM _s , the easier it is to occur, where g is the Lande g coefficient; μ _B is Bohr magnetone; P is the spin polarization rate; e is the base charge; M _s is saturated magnetization. g, and μ _B e is because the physical constants, it is effective to reduce the saturation magnetization M _s of the data recording layer 10 in order to reduce the write current and increase the spin polarization rate P.

First, alternating film stacks of transition metals, such as Co / Ni, Co / Pt, Co / Pd, CoFe / Ni, CoFe / Pt, and CoFe / Pd, form the data recording layer 10 in terms of saturation magnetization. It is promising as a magnetic film having perpendicular magnetic anisotropy used for). It is known that the saturation magnetization of these materials is relatively small. More generally, the data recording layer 10 may be configured as a film stack in which the first and second layers are laminated. The first layer includes any of an Fe film, a Co film, a Ni film, or an alloy film formed of a plurality of materials selected from the group consisting of Fe, Co, and Ni. The second layer is any of an alloy film formed of a Pt film, a Pd film, an Au film, an Ag film, a Ni film, and a Cu film or a plurality of materials selected from the group consisting of Pt, Pd, Au, Ag, Ni, and Cu. It includes thing of.

Among the film stacks described above, Co / Ni film stacks have particularly high spin polarization rates. Therefore, a Co / Ni film stack is particularly preferable as the data recording layer 10. Indeed, the inventors have confirmed by experiment that the use of Co / Ni film stacks enables domain wall movement with high control.

Alternating film stacks (e.g. Co / Ni film stacks) of transition metals are structured in an fcc (111) -oriented crystal structure in which the film stack has an fcc structure and the (111) plane is stacked in the vertical direction of the substrate. When it looks perpendicular magnetic anisotropy. According to GHO Daalderop et al., “Prediction and Confirmation of Perpendicular Magnetic Anisotropy in Co / Ni Multilayers”, PHYSICAL REVIEW LETTERS, Vol. 68, No. 5, pages 682-685, 1992, the perpendicular magnetic anisotropy of the film stack described above, It arises from the interface magnetic anisotropy at the interface. In order to provide improved perpendicular magnetic anisotropy to the data recording layer 10, it is desirable to dispose an "underlayer" which enables the growth of an alternating film stack of transition metals with improved fcc (111) orientation.

The magnetoresistive effect element 100 of this embodiment includes an underlayer 40 that enables the growth of the data recording layer 10 with improved fcc (111) orientation to achieve improved vertical magnetic anisotropy.

In this embodiment, the lower layer 40 includes three layers: a first magnetic lower layer 41, a nonmagnetic lower layer 42, and a second magnetic lower layer 43. The first magnetic lower layer 41 is formed to cover the upper surfaces of the magnetized pinned layers 50a and 50b and the upper surface of the portion of the interlayer dielectric 60 located between the magnetized pinned layers 50a and 50b. The nonmagnetic lower layer 42 is formed to cover the upper surface of the first magnetic lower layer 41, and the second magnetic lower layer 43 is formed to cover the upper surface of the nonmagnetic lower layer 42.

The magnetic underlayer 41 is formed of a material that exhibits essentially ferromagnetic properties, but with a reduced thickness that does not show ferromagneticity when the magnetic underlayer 41 is formed on an amorphous film such as the interlayer dielectric 60. In this embodiment, the magnetic underlayer 41 contains NiFe as a main component and is doped with at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf, and V, wherein the magnetic underlayer 41 The concentration of the nonmagnetic element (s) is 10-25 atomic% and the thickness of the magnetic underlayer 41 is in the range of 0.5-3 nm. The nonmagnetic lower layer 42 is formed of a nonmagnetic film having an fcc structure and exhibiting a strong (111) orientation. In this embodiment, the nonmagnetic underlayer 42 is formed of any of Pt, Au, Pd, and Ir with a thickness of 0.3 to 4.0 nm. The second magnetic underlayer 43 is formed of a magnetic film stack in which the first and second layers are alternately stacked at least once, where the first layer is formed of Pt or Pd and the second layer is Fe, Co, or Ni Is formed.

This combination of the first magnetic lower layer 41 and the nonmagnetic lower layer 42 causes the data recording layer 10 to exhibit strong perpendicular magnetic anisotropy, while the data recording layer 10 and the magnetized pinned layers 50a and 50b. Strengthen magnetic coupling between Schematically, the properties of the first magnetic underlayer 41 and the nonmagnetic underlayer 42 differ between the portion located on the interlayer dielectric 60 and the portion located on the magnetization pinned layers 50a and 50b. In general, films formed on amorphous films exhibit poor orientation. Thus, the main problem is improved perpendicular magnetic anisotropy for portions of the first magnetic underlayer 41 and the nonmagnetic underlayer 42 located over the interlayer dielectric film 60 formed of amorphous films such as SiO _x and SiN films. The data recording layer 10 is formed in a fcc (111) -oriented structure so as to be shown. For the portions overlying the magnetized pinned layers 50a and 50b, the main problem is to strengthen the magnetic coupling between the data recording layer 10 and the magnetized pinned layers 50a and 50b; When the structure of the lower layer 40 is inadequate (e.g., when a thick nonmagnetic film is used as the lower layer 40 as in the case of the prior art described above), this is undesirably with the data recording layer 10. The magnetic coupling between the magnetized pinned layers 50a and 50b is weakened. In this embodiment the combination of the first magnetic lower layer 41 and the nonmagnetic lower layer 42 simultaneously meets these two requirements.

First, portions of the first magnetic underlayer 41 and the nonmagnetic underlayer 42 overlying the interlayer dielectric film 60 are discussed. When formed on the interlayer dielectric 60, which is an amorphous film, the first magnetic underlayer 41 is grown as amorphous due to the thin film thickness of 0.5 to 3.0 nm, thereby expanding its surface energy. The portion of the first magnetic underlayer 41 in contact with the interlayer dielectric 60 is formed in a substantially free magnetization state due to the amorphous growth process. The first magnetic underlayer 41 thus configured promotes a closest packed orientation (orientation with a minimum surface energy surface) of the crystals formed on the surface thereof. In addition, the nonmagnetic underlayer 42 formed on the first magnetic underlayer 41 is oriented so that its closest face faces the fcc (111) plane, which means that the nonmagnetic underlayer 42 has Pt, Au, Pd, And a film formed of any of Ir, and formed of any of these materials has an essentially fcc structure. The data recording layer 10 is formed with strong perpendicular magnetic anisotropy by forming a magnetic film on the nonmagnetic lower layer 42, where the magnetic film has an fcc structure and exhibits strong perpendicular magnetic anisotropy with respect to the (111) orientation. . It should be noted that the data recording layer 10 is formed with strong perpendicular magnetic anisotropy due to the provision of the first magnetic underlayer 41 even when the nonmagnetic underlayer 42 has a thin film thickness.

On the other hand, the portions of the first magnetic lower layer 41 and the nonmagnetic lower layer 42 on the magnetized pinned layers 50a and 50b efficiently maintain the magnetic coupling between the data recording layer 10 and the magnetized pinned layers 50a and 50b. To strengthen. As in the case of the generally-used magneto-fixed layer, the first magnetic underlayer 41 for the case where the magnetized-fixed layers 50a and 50b are formed of a strong magnetic material such as a Co / Pt film stack and a Co-Pt alloy film. The magnetization of the portions of Nm) is due to the magnetic interaction from the magnetized pinned layers 50a and 50b when the first lower layer 41 and the nonmagnetic lower layer 42 are subsequently stacked on the magnetized pinned layers 50a and 50b. It faces in the vertical direction which is the same direction as the direction of the magnetization pinned layer 50a and 50b, respectively. This magnetic interaction fixes the magnetization of the portions of the data recording layer 10 through the nonmagnetic lower layer 42, and as a result, the magnetization fixing regions 11a and 11b are formed in the data recording layer 10. . It should be noted that due to the thin film thickness (0.5 to 4.0 nm) of the nonmagnetic underlayer 42, strong magnetic coupling is achieved between the data recording layer 10 and the magnetized pinned layers 50a and 50b.

It is contemplated that the direct deposition of the first magnetic underlayer 41 on the interlayer dielectric 60 may potentially cause undesirable magnetic effects that degrade vertical magnetic anisotropy. That is, formation of the first magnetic underlayer 41 on the amorphous interlayer dielectric 60 causes the first magnetic underlayer 41 to exhibit in-plane magnetic anisotropy, thereby degrading the perpendicular magnetic anisotropy of the data recording layer 10. You can think of it; However, the first magnetic lower layer 41 does not actually cause an undesirable magnetic effect of degrading the perpendicular magnetic anisotropy of the data recording layer 10, which means that the first magnetic lower layer 41 is formed of an interlayer dielectric ( This is because the first magnetic lower layer 41 is formed so as not to be substantially magnetized in the portion disposed on the portion 60). Thus, improved perpendicular magnetic anisotropy in the data recording layer 10 is also achieved.

The second magnetic lower layer 43 functions as a template for the crystal orientation of the data recording layer 10, which improves the fcc (111) orientation of the data recording layer 10 to enhance vertical magnetic anisotropy. In this embodiment, the second magnetic underlayer 43 is formed from a film stack in which the first and second layers are laminated at least once, where the first layer is formed of Pt or Pd and the second layer is formed of Fe, Co, Or Ni. The second magnetic underlayer 43 thus constructed effectively improves the fcc orientation 111 of the data recording layer 10 formed of the Co / Ni film stack, thereby enhancing its vertical magnetic anisotropy. In addition, the second magnetic underlayer 43 thus configured allows adjustment of the vertical magnetic anisotropy of the data recording layer 10 by adjusting the number of the first and second layers stacked in the second magnetic underlayer 43. . The vertical magnetic anisotropy of the data recording layer 10 is preferably adjusted within an appropriate range because the recording current increases if the vertical magnetic anisotropy of the data recording layer 10 is excessively strong.

It should be noted that the second magnetic underlayer 43 may be unnecessary when the magnetic film in which the fcc 111-oriented structure is easily formed is used as the data recording layer 10. For example, when a Co / Ni film stack is used as the data recording layer 10, the direct deposition of the data recording layer 10 on the nonmagnetic lower layer 42 formed of Pt, Au, Pd, or Ir is strongly vertical. It does not lead to magnetic anisotropy. In order to solve this problem, when a Co / Ni film stack in which an fcc (111) -oriented structure is not easily formed is used as the data recording layer 10, the use of the second magnetic underlayer 43 is a strong vertical magnetic field. Effectively achieves anisotropy. On the other hand, a magnetic film (e.g., at least one first layer composed of Pt or Pd and at least one second layer composed of Fe, Co, or Ni) is easily formed with an fcc (111) -oriented structure. When the containing magnetic film stack) is used as the data recording layer 10, the data recording layer 10 can be formed directly on the nonmagnetic underlayer 42.

As discussed above, the use of the underlayer 40 formed as a film stack composed of a film stack composed of the first magnetic underlayer 41, the nonmagnetic underlayer 42, and the second magnetic underlayer 43 is a data recording layer ( 10 shows strong perpendicular magnetic anisotropy, while enhancing magnetic coupling between the data recording layer 10 and the magnetized pinned layers 50a and 50b. The inventors have confirmed the above facts through experiments. The experimental results are described below.

(Experiment 1: magnetic property of the first magnetic lower layer 41)

First, the magnetic properties and the good thickness range of the first magnetic underlayer 41 will be described. In general, the properties of the first magnetic underlayer 41 are, as described above, in contact with the interlayer dielectric 60 (formed of SiN or SiO _x film) and in contact with the magnetization pinned layers 50a and 50b. It is different between.

To study the portion of the first magnetic underlayer 41 in contact with the interlayer dielectric 60 (formed of SiN or SiO ₂ film), on substrates comprising SiN film or SiO _x film, respectively, formed on a Si substrate. NiFeW films were deposited and the magnetization of NiFeW was measured. The thickness of the deposited NiFeW film was in the range of 1 to 10 nm. The NiFeW film contained 12.5 atomic% tungsten (W), with the remainder being a NiFe base metal. The ratio of Ni to Fe in the NiFe base metal is Ni: Fe = 77.5: 22.5. All samples were heat treated at 350 ° C. for 2 hours in vacuo. In measuring the magnetization of each sample, a magnetic field was applied in the direction perpendicular to the film surface. For thicknesses in the range of 1 to 10 nm, the NiFeW film does not show a rectangular shaped MH hysteresis loop, confirming that such NiFeW film is a non-ferromagnetic film or an in-plane magnetization film.

4A is a graph showing the size change of magnetization of a NiFeW film versus film thickness. As shown in FIG. 4A, magnetization tends to monotonically increase as the film thickness increases for film thickness 4 nm or more, regardless of which of the SiN and SiO _x films is disposed directly below the NiFeW film. On the other hand, for film thicknesses of 0.5 nm to 3 nm, in particular for film thicknesses smaller than 2 nm, in the case of both SiN film SiO _x films, significantly reduced compared to the case of NiFeW films having a film thickness of 4 nm or more. Magnetization was observed. This result indicates that when the NiFeW film is deposited on the interlayer dielectric 60, the NiFeW film does not show magnetization at a thin film thickness.

As discussed above, the use of a NiFeW film with a thickness of 0.5 to 3 nm as the first magnetic underlayer 41 is achieved by removing the magnetic influence on the second magnetic underlayer 43 through the nonmagnetic underlayer 42. This avoids disturbance in the perpendicular magnetic anisotropy of the second magnetic lower layer 34 and does not have any influence on the perpendicular magnetic anisotropy of the data recording layer 10 formed as a Co / Ni film stack. This allows to provide an improved fcc (111) orientation to the data recording layer 10 formed as a Co / Ni film stack.

On the other hand, the use of NiFeW having a film thickness greater than 3 nm as the first magnetic underlayer 41 is undesirable, which is not preferred, although the use of such a NiFeW film is not preferred. This is because the magnetic influence on the lower magnetic layer 43 and the data recording layer 10 weakens the perpendicular magnetic anisotropy of the data recording layer 10.

In addition, the use of a NiFeW film having a film thickness smaller than 0.5 nm as the first magnetic underlayer 41 undesirably degrades the fcc (111) orientation of the data recording layer 10, which is an interlayer dielectric (60). This is because the surface non-uniformity of c) affects the nonmagnetic lower layer 42 through the first magnetic lower layer 41. As can be appreciated from the discussion above, the preferred thickness range of the NiFeW film for the first magnetic underlayer 41 is 0.5 to 3 nm.

The same applies to the case where at least one nonmagnetic element selected from the group consisting of Zr, Ta, Hf and V is doped in place of W to the NiFe base metal. For example, FIG. 4B is a graph showing the size change of the magnetization of the NiFeZr film with respect to the film thickness, and FIG. 4C is a graph showing the size change of the magnetization of the NiFeTa film with respect to the film thickness. It should be noted that FIGS. 4B and 4C were obtained by depositing a NiFeZr film and a NiFeTa film on substrates including a SiN film formed on a Si substrate and measuring the magnetization of the NiFeZr film and the NiFeTa film. Even for NiFeZr and NiFeTa films, significantly reduced magnetization was observed at film thicknesses of 0.5 nm to 3 nm, especially at film thicknesses less than 2 nm. This result indicates that when the NiFeZr and NiFeTa films are deposited on the interlayer dielectric 60, the NiFeZr and NiFeTa films do not show magnetization at a thin film thickness.

As can be appreciated from the foregoing discussion, the first magnetic underlayer 41 preferably has a film thickness of 0.5 nm to 3 nm, more preferably a film thickness of less than 2 nm.

(Experiment 2: Crystal structure of the first magnetic lower layer 41)

Next, between the crystal structure and the nonmagnetic dopant concentration of the first magnetic underlayer 41 containing NiFe as a main component and at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V We will explain the results of the experiment on the relationship. In this experiment, films consisting of NiFe base metals doped with any of Zr, Ta, W, Hf and V were formed. The crystal structure of the formed films was analyzed using an X-ray diffractometer. The composition of the NiFe base metal which is a main component is Ni: Fe = 77.5: 22.5. The thickness of the formed film was 15 nm.

The result is that a NiFeX film (X: Zr, Ta, W, Hf or V) doped with at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V has a ratio of 10-25 atomic% Showed a diffraction profile with broad peaks for the sexual dopant concentration; This indicates that the NiFeX film has an amorphous structure. For nonmagnetic dopant concentrations lower than 10 atomic%, a crystal structure resulting from NiFe was observed. For nonmagnetic dopant concentrations higher than 25 atomic%, diffraction peaks of compounds and mixtures of NiFe and nonmagnetic elements were observed. This is because when NiFeX (X: Zr, Ta, W, Hf and V) doped with at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V is used as the first magnetic underlayer 41, , Suggests that a good concentration of nonmagnetic element is 10 to 25 atomic%.

As described above, the first magnetic underlayer 41 including at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V and NiFe as a main component is a film of the first magnetic underlayer 41. When the thickness is adjusted to 0.5 to 3 nm, substantially no magnetization is seen. The dopant concentration of the nonmagnetic element (Zr, Ta, W, Hf or V) is preferably in the range of 10 to 25 atomic%.

(Experiment 3: magnetic coupling between the data recording layer 10 and the magnetization pinned layers 50a and 50b)

Next, an experimental result regarding the relationship between the magnitude of the magnetic coupling between the data recording layer 10 and the magnetized pinned layers 50a and 50b and the thickness of the nonmagnetic lower layer 42 will be described. In this experiment, the films corresponding to the magnetized pinned layers 50a and 50b, the first magnetic lower layer 41, the nonmagnetic lower layer 42, the second magnetic lower layer 43, and the data recording layer 10 are respectively included. Film stacks were formed. Co / Pt film stacks in which Co and Pt films are alternately laminated were used as magnetic films corresponding to the magnetization pinned layers 50a and 50b. A NiFeZr film with a thickness of 1.5 nm was used as the film corresponding to the first magnetic underlayer 41, and a Pt film was used as the film corresponding to the nonmagnetic underlayer 42. A Co / Pt film stack in which a plurality of 0.4 nm thick Co films and a plurality of 0.8 nm thick Pt films were alternately laminated was used as the film corresponding to the second magnetic underlayer 43. Finally, a Co / Ni film stack in which five Co films 0.3 nm thick and five Ni films 0.6 nm thick were alternately stacked was used as the film corresponding to the data recording layer 10. Samples of the above-described structure were prepared in which the Pt films corresponding to the nonmagnetic underlayer 42 had different thicknesses in the range of 0.3 to 5 nm, and their magnetic properties were measured. All prepared samples were previously heat treated at 350 ° C. for 2 hours in vacuum.

FIG. 5A is a table showing the combined magnetic field change exerted through the Pt film (corresponding to the nonmagnetic underlayer 42) relative to the film thickness of the Pt film. As shown in FIG. 5A, a combined magnetic field of 1900 to 1975 (Oe) was observed across the Pt film corresponding to the nonmagnetic underlayer 42 in the film thickness range of 0.5 to 4.0 nm. The inventors believe that this result occurred for the following reason: Since the Co / Pt film stack corresponding to the magnetized pinned layers 50a and 50b functions as a lower layer of NiFeZr corresponding to the first magnetic underlayer 41, it is thin. NiFeZr films exhibit perpendicular magnetic anisotropy due to the influence of magnetization of the Co / Pt film stacks. In addition, the vertical magnetization of the Co / Pt film stack and the NiFeZr film affects the Co / Pt film stack corresponding to the second magnetic underlayer 43 through the Pt film corresponding to the nonmagnetic underlayer 42, and consequently the Pt This results in magnetic bonding for the reduced thickness of the film. In addition, the Co / Pt film stack corresponding to the second magnetic underlayer 43 is magnetically coupled to the Co / Ni film stack corresponding to the data recording layer 10. As a result, a combined magnetic field of about 1900 to 1975 (Oe) is generated through the Pt film corresponding to the nonmagnetic underlayer 42. This implies that the magnetization of the magnetization fixing regions 11a and 11b of the data recording layer 10 can be fixed by magnetic coupling between the magnetization fixing layers 50a and 50b and the data recording layer 10.

On the other hand, for a film thickness of 4.5 nm or more, the combined magnetic field applied through the Pt film corresponding to the nonmagnetic underlayer 42 was zero. This results in the use of a Pt film having a thickness of 4.5 nm or more as the nonmagnetic underlayer 42, and as a result, the magnetization of the magnetization pinned layers 50a and 50b and the data recording layer 10 is not magnetically coupled, that is, the data recording layer ( It suggests that the magnetization of the magnetization fixing regions 11a and 11b of 10) is not fixed.

Although the Co / Pt film stacks corresponding to the magnetization pinned layers 50a and 50b are magnetically coupled to the Co / Ni film stacks corresponding to the data recording layer 10, the thickness of the Pt film corresponding to the nonmagnetic underlayer 42 It should be noted that the coupling magnetic field is relatively small when is as thin as 0.3 nm. This is because the Pt film does not exhibit sufficient fcc (111) orientation, and therefore the Co / Ni film stack deposited thereon exhibits poor fcc (111) orientation. As can be appreciated from the foregoing discussion, when a Pt film is used as the nonmagnetic underlayer 42, the Pt film preferably has a thickness of 0.5 to 4.0 nm.

Similar results were obtained for the case where any of Au films, Pd films, and Ir films were used in place of Pt films. For example, FIG. 5B shows a film of a Pd film when a NiFeTa film having a thickness of 1.5 nm is used as the film corresponding to the first magnetic lower layer 41 and a Pd film is used as the film corresponding to the nonmagnetic lower layer 42. Table showing the combined magnetic field change exerted through the Pd film relative to the thickness. As shown in FIG. 5B, a binding magnetic field of 1910 to 1975 (Oe) was observed through the Pd film corresponding to the nonmagnetic underlayer 42 for a film thickness of 0.5 to 4.0 nm. When the film thickness of the Pd film corresponding to the nonmagnetic underlayer 42 was 4.5 nm or more, the combined magnetic field was zero or near zero. In addition, when the film thickness of the Pd film corresponding to the nonmagnetic underlayer 42 was as thin as 0.3 nm, a relatively reduced combined magnetic field of 1630 (Oe) was observed.

5C shows the film thickness of the Ir film when a NiFeTa film having a thickness of 1.5 nm is used as the film corresponding to the first magnetic lower layer 41 and an Ir film is used as the film corresponding to the nonmagnetic lower layer 42. Table 1 shows the coupling magnetic field change applied through the Ir film. As shown in FIG. 5C, a combined magnetic field of 1930 to 1965 (Oe) was observed through the Ir film corresponding to the nonmagnetic underlayer 42 for a film thickness of 0.5 to 4.0 nm. When the film thickness of the Ir film corresponding to the nonmagnetic lower layer 42 was 4.5 nm or more, the combined magnetic field was zero. In addition, when the film thickness of the Ir film corresponding to the nonmagnetic underlayer 42 was as thin as 0.3 nm, a relatively reduced combined magnetic field of 1700 (Oe) was observed.

The above-described results indicate that the nonmagnetic underlayer 42 preferably has a thickness of 0.5 to 4.0 nm.

(Experiment 4: magnetic property of magnetoresistive effect element 100)

Hereinafter, the experimental results regarding the magnetic properties of the magnetoresistive effect element 100 to which the above-described lower layer 40 is applied will be described. In this experiment, the magnetoresistive effect element 100 to which the lower layer 40 described above was applied was actually manufactured, and the magnetic properties of the data recording layer 10 were measured.

A magnetoresistive effect element 100 having the following structure was prepared as Embodiment 1. The first magnetic lower layer 41, the nonmagnetic lower layer 42, and the second magnetic lower layer 43 were sequentially stacked as the lower layer 40 of each magnetoresistive element 100 in this order. A 1.5 nm thick NiFeZr film was used as the first magnetic underlayer 41, and a 2 nm thick Pt film was used as the nonmagnetic underlayer 42. A magnetic film stack in which a plurality of 0.4 nm thick Co films and a plurality of 0.8 nm thick Pt films were alternately laminated was used as the second magnetic underlayer 43. A Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm are alternately stacked is used as the data recording layer 10. A magnetoresistive element 100 having the above-described structure has been prepared, wherein the number of Co and Pt films in the second magnetic underlayer 43 varies from 0 to 4. The magnetoresistive effect element 100 had a width of 100 nm. These magnetoresistive effect elements 100 were heat-treated at 350 ° C. for 2 hours in vacuum after the lower layer 40 and the data recording layer 10 were formed.

6A to 6D are diagrams showing magnetic field curves of the data recording layer 10 when the number of Co and Pt films in the second magnetic lower layer 43 is 0 to 3. FIG. For the case where the number of Co and Pt films is zero (ie, when the second magnetic underlayer 43 is not provided), as shown in FIG. 6A, the data recording layer 10 exhibited relatively weak perpendicular magnetic anisotropy. And in-plane magnetization. As shown in FIGS. 6B-6D, the M-H loops became more rectangular, and the vertical magnetic anisotropy tended to be enhanced as the number of laminated Co and Pt films increased. This means that the use of the second magnetic underlayer 43 is relatively difficult to achieve fcc (111) orientation even after heat treatment at 350 ° C. for 2 hours, in which a Co / Ni film stack is used as the data recording layer 10. It suggests that it allows for the achievement of strong perpendicular magnetic anisotropy for the case.

As the first magnetic underlayer 41 and the nonmagnetic underlayer 42, 1.5 nm thick NiFeZr films and 2 nm thick Pt films were used, and 0.4 nm thick Co films and 0.8 nm thick Pt films were laminated. For the case where the Pt magnetic film stack was deposited on the nonmagnetic underlayer 42, similar measurements were made. The number of Co films and Pt films in the Co / Pt magnetic film stack was one. FIG. 6E is a diagram showing a magnetization curve for a case where a Co / Pt magnetic film stack is used. As shown in FIG. 6E, for a Co / Pt magnetic film stack in which an fcc (111) orientation is formed relatively easily, a magnetic field curve with improved rectangular shape was obtained.

This fact has two technical meanings. First, the use of the Co / Pt magnetic film stack as the data recording layer 10 effectively achieves strong perpendicular magnetic anisotropy with respect to the data recording layer 10. Second, the use of a Co / Pt magnetic film stack as the second magnetic underlayer 43 enables the formation of a second magnetic underlayer 43 having an improved fcc (111) orientation and, for example, Co / Ni It effectively improves the perpendicular magnetic anisotropy of the data recording layer 10 formed on its surface (formed from the magnetic film stack).

In addition, the second magnetic underlayer 43, as a make-up port for the H _s when the Co / Pt as a magnetic film stack is used and the data recording layer (10), Co / Ni magnetic film stack used was measured. 7 shows the definition of the saturation field H _s in the present application. In the present application, the saturation field H _s is defined as the magnitude of the external magnetic field in which the magnetization of the data recording layer 10 is completely directed in the direction of the external magnetic field when the external magnetic field is applied in the in-plane direction of the data recording layer 10. do. In FIG. 7, for example, H _s1 represents the _{saturation field} of the sample 1, and H _s2 represents the _{saturation field} of the sample 2. Large saturation fields imply large vertical magnetic anisotropy. In FIG. 7, for example, the saturation field H _s of the sample 1 (ie, the magnetic field indicating complete magnetization in its own direction) is greater than the saturation field of the sample 2, which is the It suggests that the perpendicular magnetic anisotropy is greater than the perpendicular magnetic anisotropy of the sample 2.

Figure 8 shows a second port change makeup H _s of the data storage layer 10 with respect to the magnetic underlayer 43, a number of Co and Pt film, wherein the number of Co and Pt is variable from 0 to 4. As can be appreciated from FIG. 8, the saturation field H _s increased with the number of Co and Pt films in the second magnetic underlayer 43; This suggests that the perpendicular magnetic anisotropy is enhanced as the number of Co and Pt films increases.

9 shows a variation in the second magnetic from the lower layer (43) of the number of Co and Pt film, bubble cosmetic H _s and the recording current. The magnitude of the write current is defined as the minimum write current required to cause domain wall movement in the data recording layer 10. Details of the experimental procedure are described in T. Suzuki et al., "Evaluation of Scalability for Current-Driven Domain Wall Motion in a Co / Ni Multilayer Strip for Memory Applications," IEEE Transactions on Magnetics, 45. Vol. 10, pp. 3776-3779, (2009).

For samples where the number of Co and Pt films in the second magnetic underlayer 43 was zero (which means that the second magnetic underlayer 43 was not deposited), domain wall movement by current was not clearly observed, As a result, the measurement of the recording current was not successful. This may be considered to arise from the fact that the data recording layer 10 exhibited relatively weak perpendicular magnetic anisotropy and contained an in-plane magnetization component as shown in Fig. 6A.

For the case where the number of Co and Pt films in the second magnetic underlayer 43 is not zero, the recording current gradually increased as the number of Co and Pt films increased. For the case where the number of Co and Pt films was 4, the saturation field H _s increased to about 10000 (Oe) and the recording current increased steeply to exceed 0.5 mA. According to N. Sakimura et al., “MRAM Cell Technology for Over 500-MHz SoC,” IEEE Journal of Solid-State Circuits, Vol. 42, No. 4, pages 830-838, 2007, by reducing the write current below 0.5 mA, It is possible to reduce the cell area to the level of the embedded SRAM of.

As described above, the use of the Co / Pt film stack as the second magnetic underlayer 43 is characterized by the perpendicular magnetic anisotropy of the data recording layer 10 when the Co / Ni film stack is used as the data recording layer 10. Strengthens effectively. In addition, adjustment of the number of Co and Pt films in the second magnetic underlayer 43 enabled the control of the perpendicular magnetic anisotropy of the data recording layer 10, and the write current (or domain wall movement required to induce domain wall movement). Current) is sufficiently reduced. In order to adjust the perpendicular magnetic anisotropy to an appropriate value, the preferred range of saturation field H _s was 3000 (Oe) ≤ H _S ≤ 10000 (Oe), in which the second magnetic lower layer 43 for achieving the saturation field H _s ), The number of Co and Pt films was 1-3.

As Comparative Example 1, a magnetoresistive effect element 300 was further prepared as shown in FIG. 10, where the lower layer 70 was composed of the first magnetic lower layer 71 and the nonmagnetic lower layer 72, and the thickness thereof. A 2 nm NiFeB film was used as the first magnetic underlayer 71, and a 2 nm thick Pt film was used as the nonmagnetic underlayer 72. The data recording layer 10 was formed on the lower layer 70 as a Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm were alternately stacked. The magnetoresistive effect element 300 was heat treated at 350 ° C. for 2 hours in vacuum after the lower layer 70 and the data recording layer 10 were formed, as in the case of Embodiment 1.

Four magnetic makeup H _s of the resistive elements 300 of the data storage layer 10 was measured as about 1050 (Oe). In addition, it was determined from the magnetic field loop measured by applying the magnetic field in the vertical direction of the film surface that the data recording layer 10 of the magnetoresistive effect element 300 contained an in-plane magnetization component and exhibits very weak vertical magnetic anisotropy. . NiFeB films exhibit in-plane magnetic anisotropy regardless of film thickness, and their magnetization is increased by heat treatment. This is because the first magnetic lower layer 71 caused the effect of instructing the magnetization of the data recording layer 10 (Co / Ni film stack) in the in-plane direction through the nonmagnetic lower layer 72, and as a result, the data recording. Layer 10 was formed as an in-plane magnetization film that exhibited weak perpendicular magnetic anisotropy.

In addition, as Embodiment 2, a magnetoresistive effect element 100 was further prepared in which a NiFeW film having a thickness of 1.5 nm was used as the first magnetic underlayer 41. Except for this aspect, the configuration of the magnetoresistive element 100 of Embodiment 2 was the same as that of Embodiment 1. In detail, the first magnetic lower layer 41, the nonmagnetic lower layer 42, and the second magnetic lower layer 43 were sequentially formed as the lower layer 40 in this order. A 1.5 nm thick NiFeW film was used as the first magnetic underlayer 41, and a 2 nm thick Pt film was used as the nonmagnetic underlayer 42. A magnetic film stack in which a plurality of Co films and a plurality of Pt films are alternately laminated was used as the second magnetic underlayer 43. A Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm are alternately stacked is used as the data recording layer 10. The magnetoresistive element 100 of Embodiment 2 was also heat treated at 350 ° C. for 2 hours in vacuum. For the magnetoresistive element 100 thus constructed, the change of the magnetic field H _s with respect to the film thickness ratio of the Pt and Co films of the second magnetic underlayer 43 and the number of Pt and Co films was examined. FIG. 11A is a graph showing the change in the magnetic field H _s versus the number of Pt and Co films in the second magnetic lower layer 43 with respect to the different film thickness ratios of the Pt and Co films. As can be understood from FIG. 11A, for the case where the film thickness ratio of the Pt film to the Co film of the second magnetic lower layer 43 is 1.0 to 5.0, when the number of Co films and Pt films is 1 to 3, Makeup H _s had a range from 3000 to 5500 (Oe); This means that the data recording layer 10 exhibited perpendicular magnetic anisotropy in which current-driven domain wall movement can be achieved.

Further, as Example 3, a magnetoresistive element 100 having a 1.5 nm thick NiFeV film as the first magnetic underlayer 41 and an Au film having a thickness of 2 nm was used. Except for this aspect, the configuration of the magnetoresistive element 100 of Example 3 was the same as that of the embodiments 1 and 2. For the magnetoresistive element 100 thus constructed, the change of the magnetic field H _s with respect to the film thickness ratio of the Pt and Co films of the second magnetic lower layer 43 and the number of Pt and Co films was examined. FIG. 11B is a graph showing the change in the magnetic field H _s with respect to the number of Pt and Co films in the second magnetic lower layer 43 with respect to the different film thickness ratios of the Pt and Co films. In addition, as in FIG. 11B, for the case where the film thickness ratio of the Pt film to the Co film of the second magnetic lower layer 43 is 1.0 to 5.0, the saturation field H _s has a range of 3000 to 5500 (Oe); This means that the data recording layer 10 exhibited perpendicular magnetic anisotropy in which current-driven domain wall movement can be achieved.

The above result indicates that the good film thickness ratio of the Co film and the Pt film in the second magnetic underlayer 43 is 1.0 to 5.0.

In the above-described examples, a NiFeZr film or NiFeW film is used as the first magnetic underlayer 41, a Pt film is used as the nonmagnetic underlayer 42, and a film stack composed of Co and Pt films is the second nonmagnetic underlayer 43. Although the present invention is related to the case, the materials of the first magnetic lower layer 41, the nonmagnetic lower layer 42, and the second magnetic lower layer 43 are not limited to those described above. The inventors have found that a similar effect can be achieved using thin film materials obtained by doping NiFe base metals with at least one nonmagnetic material selected from the group consisting of Ta, Hf and V (instead of Zr and W). It was. In addition, the inventors have confirmed that similar effects can be achieved by using Au film, Pd film or Ir film as the nonmagnetic underlayer 42 instead of the Pt film. In addition, the inventors use a combination of layers formed of any of Fe, Co, and Ni as the second magnetic underlayer 43, and a combination of layers formed of any of Pt and Pd, instead of the combination of Co film and Pt film. Thus, it was confirmed that similar effects can be achieved.

2nd Example

12 is a sectional view schematically showing an exemplary configuration of a magnetoresistive element 100A of a second embodiment of the present invention. The magnetoresistive effect element 100A of the second embodiment is configured similarly to the magnetoresistive effect element 100 of the first embodiment. The difference is in the structure of the lower layer. In the first embodiment, as described above, the first magnetic underlayer 41 of the underlayer 40 is formed of an essentially ferromagnetic material having a thin thickness such that the first magnetic underlayer 41 does not show ferromagneticity. . On the other hand, in the second embodiment, the first magnetic lower layer 41A of the lower layer 40A has a thin thickness (specifically, 0.5 to 3 nm) such that the first magnetic lower layer 41A exhibits perpendicular magnetic anisotropy, It is essentially formed of a material that exhibits in-plane magnetic anisotropy. The first magnetic lower layer 41A is formed of an amorphous magnetic material containing Co or Fe as a main component and at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf, and V.

The structures of the nonmagnetic lower layer 42, the second magnetic lower layer 43, and the data recording layer 10 are the same as in the first embodiment. The nonmagnetic lower layer 42 is formed of a nonmagnetic film having an fcc structure and exhibiting a strong (111) orientation. In this embodiment, the nonmagnetic underlayer 42 is formed of Pt, Au, Pd, or Ir, and has a thickness of 0.3 to 4.0 nm. The second magnetic underlayer 43 is formed of a magnetic film stack in which at least one first layer and at least one second layer are alternately stacked, wherein the first layer is formed of any one of Pt and Pd, The second layer is formed of any one of Fe, Co, and Ni. The data recording layer 10, which is a magnetic film having perpendicular magnetic anisotropy, preferably has alternating transition metals such as Co / Ni, Co / Pt, Co / Pd, CoFe / Ni, CoFe / Pt, and CoFe / Pd- It is formed into a film stack to be laminated. It is known that the saturation magnetization of these materials is relatively small. More generally speaking, the data recording layer 10 is configured as a film stack in which the first and second layers are laminated. The first layer comprises Fe, Co Ni, or an alloy of a plurality of materials selected from the group consisting of Fe, Co and Ni. The second layer comprises an alloy of plural materials selected from the group consisting of Pt, Pd, Au, Ag, Ni, Cu, or Pt, Pd, Au, Ag, Ni, and Cu. Among the film stacks described above, Co / Ni film stacks exhibit high spin polarization. Therefore, a Co / Ni film stack is particularly preferable as the data recording layer 10.

The advantages of the first magnetic underlayer 41A of the second embodiment are discussed below. When formed on an amorphous film, such as the interlayer dielectric 60, as in the case of the first magnetic underlayer 41 of the first embodiment, the first magnetic underlayer 41A has a thin film thickness range of 0.5 to 3.0 nm. It grows to become amorphous, and expands the surface energy. The first magnetic lower layer 41A thus constituted promotes the closest orientation (orientation with the minimum surface energy plane) of the crystal formed on the surface thereof. Further, the nonmagnetic underlayer 42 formed on the first magnetic underlayer 41A is grown such that its closest face faces the fcc (111) plane, which means that the nonmagnetic underlayer 42 is formed of Pt, Au, Pd, And a film formed of any of Ir, and formed of any of these materials originally have an fcc structure. The data recording layer 10 can be formed with strong perpendicular magnetic anisotropy by forming a magnetic film on the nonmagnetic underlayer 42, where the magnetic film has an fcc structure and strong perpendicular magnetic anisotropy with respect to the (111) orientation. Seems. It should be noted that the data recording layer 10 is formed with strong perpendicular magnetic anisotropy due to the provision of the first magnetic lower layer 41A even when the nonmagnetic lower layer 42 has a thin film thickness.

Here, the first magnetic lower layer 41A of the second embodiment is formed of a material containing Co or Fe as a main component and at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf, and V; This material, in essence, exhibits in-plane magnetic anisotropy. This can be considered undesirably to cause deterioration of the perpendicular magnetic anisotropy of the data recording layer. Nevertheless, the first magnetic underlayer 41A of such a material is actually formed as an amorphous magnetic body having weak perpendicular magnetic anisotropy when the thickness of the first magnetic underlayer 41A is as thin as 0.5 to 3 nm. As in the case of the first magnetic underlayer 41 of the first embodiment formed to be substantially invisible to magnetization, the first magnetic underlayer 41A of the second embodiment does not degrade the perpendicular magnetic anisotropy of the data recording layer 10. . Therefore, the first magnetic lower layer 41A of the second embodiment is also preferable in order to achieve strong perpendicular magnetic anisotropy of the data recording layer 10.

On the other hand, the portion of the first magnetic lower layer 41A on the magnetized pinned layers 50a and 50b effectively strengthens the magnetic coupling between the data recording layer 10 and the magnetized pinned layers 50a and 50b. When the first magnetic lower layer 41A and the nonmagnetic lower layer 42 are subsequently stacked on the magnetized pinned layers 50a and 50b, the magnetized pinned layer 50a is made of a strong magnetic material such as a Co / Pt film stack and a Co-Pt alloy film. And 50b), the magnetization of the portions of the first magnetic underlayer 41A on the magnetization pinned layers 50a and 50b is due to the magnetic interaction from the magnetization pinned layers 50a and 50b, respectively. It goes in the vertical direction which is the same direction as the direction of 50a and 50b. This magnetic interaction fixes the magnetization of the portions of the data recording layer 10 through the nonmagnetic lower layer 42, and as a result, the magnetization fixing regions 11a and 11b are formed in the data recording layer 10. . It should be noted that due to the thin film thickness (0.5 to 4.0 nm) of the nonmagnetic underlayer 42, strong magnetic coupling is achieved between the data recording layer 10 and the magnetized pinned layers 50a and 50b.

As can be understood from the above experimental results, the first magnetic lower layer 41A of the second embodiment enhances the perpendicular magnetic anisotropy of the data recording layer 10 more effectively than the first magnetic lower layer 41 of the first embodiment. , MR ratio increase of the magnetoresistive effect element is achieved. Further, the first magnetic lower layer 41A of the second embodiment enhances the magnetic coupling between the magnetization pinned layers 50a and 50b and the data recording layer 10 more effectively than the first magnetic lower layer 41 of the first embodiment. . The experimental results are described below.

(Experiment 1: Underlying Material Dependence of MR Ratio of Magnetic Tunnel Junction)

First, the dependence of the MR ratio of the magnetic tunnel junction composed of the data recording layer 10, the spacer layer 20 and the reference layer 30 on the material of the first magnetic lower layer 41 or 41A was examined. For each magnetoresistive effect element, a dielectric film corresponding to the interlayer dielectric 60 was formed on the substrate and the lower layer 40 or 40A, and the data recording layer 10, spacer layer 20, and reference layer ( 30) was formed. The lower layer 40 or 40A, the first magnetic lower layer 41 or 41A, the nonmagnetic lower layer 42, and the second magnetic lower layer 43 were sequentially formed in this order.

NiFeZr films, CoTa films, CoZr films or FeZr films with a thickness of 1.5 nm were used as the first magnetic underlayer 41 or 41A. The NiFeW film contained 12.5 atomic% tungsten (W), with the remainder being a NiFe base metal. The ratio of Ni to Fe in the NiFe base metal is Ni: Fe = 77.5: 22.5. The CoTa film contained 20 atomic% tantalum (Ta), with the remainder being Co base metal. The CoZr film contained 20 atomic percent zirconium (Zr), with the remainder being Co base metal. The FeZr film contained 20 atomic% zirconium (Zr), and the rest was Fe base metal. The NiFeZr film corresponds to the first magnetic underlayer 41 of the first embodiment, and the CoTa film, CoZr film, and FeZr film correspond to the first magnetic underlayer 41A of the second embodiment.

In addition, a 2 nm thick Pt film was used as the nonmagnetic underlayer 42, and a magnetic film stack in which a plurality of 0.4 nm thick Co films and a plurality of 0.8 nm thick Pt films were alternately laminated was used as the second magnetic underlayer ( 43). A Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm are alternately stacked is used as the data recording layer 10. The samples thus prepared had a width of 100 nm. These samples were heat-treated at 300 to 350 ° C. for 2 hours in vacuum after the lower layer 40 (or 40A), data recording layer 10, spacer layer 20 and reference layer 30 were formed.

13A is a graph showing the dependence of the MR ratio on the material of the first magnetic lower layer 41 or 41A. As shown in Fig. 13A, as a result of using the NiFeZr film (corresponding to the first magnetic underlayer 41 of the first embodiment), the magnetic tunnel junction showed an MR ratio of about 23 to 42 (note that this range is MR ratio is sufficient for the actual implementation). On the other hand, as a result of using the CoTa film, CoZr film, or FeZr film (corresponding to the first magnetic lower layer 41A of the second embodiment), the magnetic tunnel junction showed an MR ratio of about 53 to 65, and the use of NiFeZr film MR ratios higher than the MR ratios achieved by The effect of MR ratio improvement was particularly significant for low heat treatment temperatures (especially for heat treatment temperatures of 300 ° C). As a result, the first magnetic lower layer 41A of the second embodiment enhances the perpendicular magnetic anisotropy of the data recording layer 10 more effectively than the first magnetic lower layer 41 of the first embodiment, and thus the MR of the magnetoresistive element Suggests increasing the rate effectively.

(Experiment 2: Evaluation of the bonding state between the magnetized pinned layers 50a and 50b and the data recording layer 10)

In addition, the bonding state between the magnetized pinned layers 50a and 50b and the data recording layer 10 was evaluated. A magnetic film corresponding to the magnetization pinned layers 50a and 50b was formed on the substrate, and the lower layer 40 or 40A and the data recording layer 10 were formed on this magnetic film. The lower layer 40 or 40A, the first magnetic lower layer 41 or 41A, the nonmagnetic lower layer 42, and the second magnetic lower layer 43 were sequentially formed in this order.

A NiFeZr film or CoTa film with a thickness of 1.5 nm was used as the first magnetic underlayer 41 or 41A. The NiFeZr film corresponds to the first magnetic underlayer 41 of the first embodiment, and the CoTa film corresponds to the first magnetic underlayer 41A of the second embodiment. The NiFeZr film contained 12.5 atomic% zirconium (Zr), with the remainder being a NiFe base metal. The ratio of Ni to Fe in the NiFe base metal is Ni: Fe = 77.5: 22.5. The CoTa film contained 20 atomic% tantalum (Ta), with the remainder being Co base metal.

In addition, a 2 nm thick Pt film was used as the nonmagnetic underlayer 42, and a magnetic film stack in which a plurality of 0.4 nm thick Co films and a plurality of 0.8 nm thick Pt films were alternately laminated was used as the second magnetic underlayer ( 43). A Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm are alternately stacked is used as the data recording layer 10. The width of the samples was 100 nm. These samples were heat-treated at 300 to 350 ° C. for 2 hours in vacuum after the lower layer 40 and the data recording layer 10 were formed.

13B-13E show the magnetic field curves of the samples thus obtained. Specifically, FIGS. 13B and 13C show a hysteresis loop of samples comprising a first magnetic underlayer 41 based on a NiFeZr film, while FIGS. 13D and 13E include a first magnetic underlayer 41A based on a CoTa film. The hysteresis loop of the samples is shown. Magnetically bonded Co / Ni film stacks as a unit when there is a sufficiently large magnetic bond between the magnetic film corresponding to the magnetized pinned layers 50a and 50b and the Co / Ni film stack corresponding to the data recording layer 10 In the magnetic film, magnetization reversal occurs, and as a result, a typical hysteresis loop without any step is observed as the magnetic field curve. On the other hand, when the magnetic coupling is weak, magnetization reversal occurs separately in the magnetic film and the Co / Ni film stack, so that a stepped hysteresis loop is observed as the magnetic field curve.

As shown in FIGS. 13B and 13C, the first magnetic underlayer 41 based on the NiFeZr film achieved a hysteresis loop without any steps for a heat treatment temperature of 350 ° C .; However, a stepped hysteresis loop was observed for the heat treatment temperature of 300 ° C. This, the use of NiFeZr film as the first magnetic underlayer 41 at a heat treatment temperature of 300 ° C., undesirably, Co corresponding to the magnetic film and data recording layer 10 corresponding to the magnetization pinned layers 50a and 50b Suggests weakening magnetic coupling between the / Ni film stacks.

On the other hand, as shown in FIGS. 13D and 13E, the first magnetic underlayer 41A based on the CoTa film achieved a hysteresis loop without any steps for both the heat treatment temperatures of 300 and 350 ° C. This suggests that the use of the CoTa film as the first magnetic lower layer 41A provides a sufficiently strong magnetic bond between the magnetic film corresponding to the magnetization pinned layers 50a and 50b and the Co / Ni film stack corresponding to the data recording layer 10. Imply that it achieves.

(Experiment 3: magnetic property of the first magnetic lower layer 41A)

Next, the magnetic properties and the good thickness range of the first magnetic lower layer 41A will be described. In order to study the portion of the first magnetic underlayer 41A in contact with the interlayer dielectric 60 (formed of SiN or SiO ₂ film), a CoTa film was formed on substrates on which a 20 nm SiN film was deposited on the Si substrate. And the magnetization of the CoTa film was measured. The thickness of the formed CoTa film was in the range of 0.5 to 5 nm. The CoTa film formed contained 20 atomic% of tantalum (Ta), and the remainder was Co base metal. Samples were heat treated at 350 ° C. for 2 hours in vacuo.

FIG. 14A shows the magnetic field curve of the CoTa film when the magnetic field is applied in the vertical direction of the film surface during the magnetization measurement, and FIG. 14B shows the change in size of magnetization with respect to the CoTa film thickness. This measurement is equivalent to the measurement of the perpendicular magnetic anisotropy of the samples. As shown in FIG. 14A, the CoTa film showed no magnetization for a thickness of 0.5 nm. Such a CoTa film (not showing in-plane magnetic anisotropy) is suitable as the first magnetic lower layer 41A, and thus does not have any magnetic influence on the generation of perpendicular magnetic anisotropy of the data recording layer 10.

In the film thickness range of 1.0 to 3.0 nm, hysteresis loops were obtained as magnetization curves. It should be noted that the magnetization of the CoTa film in the vertical direction of the film surface was small at a film thickness in the range of 1.0 to 3.0 nm, as shown in FIG. 14B. Vertical magnetization of the film surface showed a small increase with increasing film thickness. This suggests that the CoTa film exhibits small perpendicular magnetic anisotropy in the film thickness range of 1.0 to 3 nm. Such a CoTa film (not showing in-plane magnetic anisotropy) is suitable as the first magnetic lower layer 41A, and thus does not have any magnetic influence on the generation of perpendicular magnetic anisotropy of the data recording layer 10.

It should be noted that the first magnetic underlayer 41A does not provide the originally-intended function of enhancing crystal growth at film thickness below 0.5 nm. Therefore, when the CoTa film is used as the first magnetic underlayer 41A, the thickness of the CoTa film is preferably in the range of 0.5 nm to 3.0 nm.

On the other hand, when the film thickness was 4.0 nm, the vertical magnetization of the film surface was reduced as shown in FIG. 14A. This is derived from the fact that large magnetization occurred in the in-plane direction in the CoTa film, that is, large in-plane anisotropy occurred. Such a CoTa film is not suitable as the first magnetic underlayer 41A because a large in-plane magnetic anisotropy is produced in the CoTa film for a film thickness of 4.0 nm or more.

The above results indicate that the preferred film thickness range of the CoTa film as the first magnetic layer 41A is 0.5 nm to 3.0 nm.

The inventors confirmed that not only the CoTa film described above but also the CoZr film, the FeTa film, and the FeZr film.

(Experiment 4: Influence of the structure of the second magnetic lower layer 43)

In addition, when the above-described first magnetic lower layer 41A of the second embodiment is applied, the influence of the number of layers of the second magnetic lower layer 43 of the magnetoresistive effect element was examined. Specifically, samples of the following structure were prepared: first magnetic lower layer 41, nonmagnetic lower layer 42, and second magnetic lower layer 43 as lower layer 40A of each magnetoresistive effect element. It was laminated sequentially in this order. A 1.5 nm thick CoTa film was used as the first magnetic underlayer 41A, and a 2 nm thick Pt film was used as the nonmagnetic underlayer 42. The CoTa film contained 20 atomic% tantalum (Ta), with the remainder being Co base metal. A magnetic film stack in which one or more Co films of 0.4 nm in thickness and one or more Pt films of 0.8 nm in thickness were alternately stacked was used as the second magnetic underlayer 43. A Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm are alternately stacked is used as the data recording layer 10. A magnetoresistive element 100 having the above-described structure has been prepared, wherein the number of Co and Pt films in the second magnetic underlayer 43 varies from 0 to 4. The width of the samples was 100 nm. These samples were heat-treated at 350 ° C. for 2 hours in vacuum after the lower layer 40A and the data recording layer 10 were formed.

15A to 15C are diagrams showing the magnetic field curve of the data recording layer 10 in the case where the number of Co and Pt films in the second magnetic lower layer 43 is 0 to 2. FIG. For the case where the number of Co and Pt films is zero (i.e., no second magnetic underlayer 43 is provided), as shown in Fig. 15A, the data recording layer 10 exhibited relatively weak perpendicular magnetic anisotropy and And in-plane magnetization. As shown in Figs. 15B to 15C, the M-H loops became more rectangular, and the vertical magnetic anisotropy tended to be enhanced as the number of laminated Co and Pt films increased. This means that the use of the second magnetic underlayer 43 is relatively difficult to achieve fcc (111) orientation even after heat treatment at 350 ° C. for 2 hours, in which a Co / Ni film stack is used as the data recording layer 10. It implies strong vertical magnetic anisotropy for the case.

This fact has two technical meanings: First, the use of a Co / Pt magnetic film stack as the data recording layer 10 effectively achieves strong perpendicular magnetic anisotropy with respect to the data recording layer 10. Second, the use of a Co / Pt magnetic film stack as the second magnetic underlayer 43 enables the formation of a second magnetic underlayer 43 having an improved fcc (111) orientation and, for example, Co / Ni It effectively improves the perpendicular magnetic anisotropy of the data recording layer 10 formed thereon (formed by a magnetic film stack).

Further, when a CoTa film is used as the first magnetic underlayer 41A, a Co / Pt magnetic film stack is used as the second magnetic underlayer 43, and a Co / Ni magnetic film stack is used as the data recording layer 10. Saturated field H _s was measured. Figure 16 shows a second port change makeup H _s of the data storage layer 10 with respect to the magnetic underlayer 43, a number of Co and Pt film, wherein the number of the Co and the Pt film is variable from 0 to 4; . As can be appreciated from FIG. 16, the saturation field H _s increased with the number of Co and Pt films in the second magnetic underlayer 43; This suggests that the perpendicular magnetic anisotropy is enhanced as the number of Co and Pt films increases.

Figure 17 shows the changes in the second magnetic from the lower layer (43) of the number of Co and Pt film, bubble cosmetic H _s and the recording current. The magnitude of the write current is defined as the minimum write current required to cause domain wall movement in the data recording layer 10. Details of the experimental procedure can be found in T. Suzuki et al., "Evaluation of Scalability for Current-Driven Domain Wall Motion in a Co / Ni Multilayer Strip for Memory Applications," IEEE Transactions on Magnetics, 45, 10, pages 3776-3779, (2009).

For samples where the number of Co and Pt in the second magnetic underlayer 43 was zero (which means that the second magnetic underlayer 43 was not deposited), the domain wall movement by the current was not clearly observed, and As a result, the measurement of the recording current was not successful. This may be considered to arise from the fact that the data recording layer 10 exhibited relatively weak perpendicular magnetic anisotropy and contained an in-plane magnetization component as shown in Fig. 15A.

For the case where the number of Co and Pt films in the second magnetic underlayer 43 is not zero, the recording current gradually increased as the number of Co and Pt films increased. For the case where the number of Co and Pt films was 4, the saturation field H _s increased to about 10000 (Oe) and the recording current increased steeply to exceed 0.5 mA. According to N. Sakimura et al., “MRAM Cell Technology for Over 500-MHz SoC,” IEEE Journal of Solid-State Circuits, Vol. 42, No. 4, pages 830-838, 2007. The cell area can be reduced by the level of the embedded SRAM.

As described above, the use of the Co / Pt film stack as the second magnetic underlayer 43 allows the CoTa film to be used as the first magnetic underlayer 41A and the Co / Ni film stack to be used as the data recording layer 10. At this time, the perpendicular magnetic anisotropy of the data recording layer 10 was effectively enhanced. In addition, adjustment of the number of Co and Pt films in the second magnetic underlayer 43 enabled the control of the perpendicular magnetic anisotropy of the data recording layer 10, and the write current (or domain wall movement required to induce domain wall movement). Current) is sufficiently reduced. In order to adjust the perpendicular magnetic anisotropy to an appropriate value, the preferred range of saturation field H _s was 3000 (Oe) ≤ H _S ≤ 10000 (Oe), in which the second magnetic lower layer 43 for achieving the saturation field H _s ), The number of Co and Pt films was 1-3.

Moreover, the influence of the film thickness ratio of the Pt and Co film of the 2nd magnetic lower layer 43 was examined. In detail, the first magnetic lower layer 41A, the nonmagnetic lower layer 42, and the second magnetic lower layer 43 were sequentially formed in this order as the lower layer 40A. A 1.5 nm thick CoTa film was used as the first magnetic underlayer 41A, and a 2 nm thick Pt film was used as the nonmagnetic underlayer 42. A magnetic film stack in which a plurality of Co films and a plurality of Pt films are alternately laminated was used as the second magnetic underlayer 43. A Co / Ni film stack in which five Co films having a thickness of 0.3 nm and five Ni films having a thickness of 0.6 nm are alternately stacked is used as the data recording layer 10. Samples were heat treated at 350 ° C. for 2 hours in vacuo. For the samples thus constructed, the change in the magnetic field H _s for the thickness ratio of the Pt and Co films and the number of Pt and Co films in the second magnetic lower layer 43 was examined.

FIG. 18 is a graph showing the change in the magnetic field H _s versus the number of Pt and Co films in the second magnetic underlayer 43 with respect to the different film thickness ratios of the Pt and Co films. As can be understood from FIG. 18, when the film thickness ratio of the Pt film to the Co film of the second magnetic lower layer 43 is 1.0 to 5.0, the number of Co films and Pt films is 1 to 3 Makeup H _s had a range from 3000 to 5500 (Oe); This means that the data recording layer 10 exhibited perpendicular magnetic anisotropy in which current-driven domain wall movement can be achieved.

The third Example

19A is a cross-sectional view showing an exemplary configuration of a magnetoresistive element 100B of a third embodiment of the present invention, and FIG. 19B is an exemplary configuration of a magnetic recording layer of the magnetoresistive element 100B of a third embodiment. It is a cross section. It should be noted that FIG. 19B is a cross sectional view of the SS ′ section of FIG. 19A.

The magnetoresistive effect element 100B of the third embodiment is configured similarly to the magnetoresistive effect element 100 of the first embodiment. The difference is in the structure of the lower layer. In the first embodiment, the underlayer 40 includes a first magnetic underlayer 41, a nonmagnetic underlayer 42, and a second magnetic underlayer 43. On the other hand, in the third embodiment, the lower layer 40B does not include elements corresponding to the second magnetic underlayer 43 of the first embodiment, while the magnetic underlayer 41 and the intermediate layer (corresponding to the nonmagnetic underlayer) ( 42B). The data recording layer 10 is formed on the intermediate layer 42B. In the first embodiment, it has already been discussed that the second magnetic underlayer 43 is not an essential element; In this embodiment, a good structure will be presented for the case where the second magnetic underlayer 43 is not provided.

The magnetized pinned layers 50a and 50b are embedded in grooves formed on the interlayer dielectric 60. Below the interlayer dielectric 60 (such as SiO ₂ and SiN _x ), elements (such as select transistors Tra and Trb) and interconnects (such as word lines WL and bit lines BL and / BL) are embedded.

The magnetic lower layer 41 is formed on the upper surfaces of the interlayer dielectric 60 and the magnetization pinned layers 50a and 50b. The magnetic lower layer 41 is in contact with the upper surfaces of the magnetized pinned layers 50a and 50b at the lower surface (-z side) of the end portion (in the x direction). The magnetic lower layer 41 is formed of a magnetic material. As described above, the ferromagneticity of the magnetic lower layer 41 enhances the magnetic coupling between the magnetized pinned layers 50a and 50b and the data recording layer 10.

The magnetic underlayer 41 is preferably amorphous or has a microcrystalline structure, because such a structure improves the surface flatness of the magnetic underlayer 41. The microcrystalline structure of the magnetic underlayer 41 may be, for example, in a crystalline phase formed from crystals having a grain size of several nano to 20 nm. Alternatively, the magnetic lower layer 41A may be formed as a mixture of the crystalline phase and the amorphous phase. In order for the data recording layer 10 to have a desired crystallinity, the smooth surface of the magnetic lower layer 41 is formed to form the data recording layer 10 deposited over the magnetic lower layer 41 through the intermediate layer 42B. desirable. For example, when the data recording layer 10 is a [Co / Ni] _n / Pt film, the magnetic underlayer is such that the [Co / Ni] film stack exhibits an fcc (111) orientation that causes high perpendicular magnetic anisotropy. The smooth surface of (41) is preferable.

The magnetic lower layer 41 includes at least one of Ni, Fe, and Co as a main component, and at least one nonmagnetic element selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, W, B, and N. . It should be noted that "main component" means a configuration that most exists in the magnetic lower layer 41. The magnetic underlayer 41 may be formed of, for example, NiFeZr, CoFeB, CoZrMo, CoZrNb, CoZr, CoZrTa, CoHf, CoTa, CoTaHf, CoNbHf, CoZrNb, CoHfPd, CoTaZrNb, CoZrMoNi or CoTi.

The intermediate layer 42B is a nonmagnetic material formed to cover the magnetic lower layer 41. In order to enhance the perpendicular magnetic anisotropy of the data recording layer 10 formed on the intermediate layer 42B, the intermediate layer 42B is preferably formed of a material having a small surface energy to improve crystal orientation. In one example, the intermediate layer 42B is formed of a Ta film. When the intermediate layer 42B is formed of a Ta film, the intermediate layer 42B preferably has a thickness of 0.1 to 2.0 nm as described below. When the thickness of the intermediate layer 42B is smaller than 0.1 nm, the enhancement effect of the perpendicular magnetic anisotropy of the data recording layer 10 is considerably deteriorated. When the thickness of the intermediate layer 42B is larger than 2.0 nm, the magnetic coupling between the magnetized pinned layers 50a and 50b and the data recording layer 10 is lost.

The data recording layer 10 is a ferromagnetic material having perpendicular magnetic anisotropy formed to cover the intermediate layer 42B. The magnetization pinned layers 11a and 11b and the magnetization free region 13 are formed in the data recording layer 10. That is, the data recording layer 10 is an area in which a domain wall is formed and data is stored as the magnetization direction of the magnetization free area 13 or stored as a location of the domain wall. The recording layer 10 may be formed of a ferromagnetic material having perpendicular magnetic anisotropy, as described in the first and second embodiments.

In the following, an example of the magnetoresistive effect element of the third embodiment is described together with the comparison with the comparative examples. The saturation field is used as an index of the magnitude of the perpendicular magnetic anisotropy. The definition of the saturation field is as defined with reference to FIG. 7.

Comparative Example 1

20A and 20B are sectional views showing the configuration of the magnetoresistive element 300B of Comparative Example 1. FIG. It should be noted that the spacer layer 20 and the reference layer 30 are not shown. In one example, a SiO ₂ film was used as the interlayer dielectric 60. [Co / Ni] _n / Pt film stacks in which a Pt film 10b and a Co / Ni film stack 10a were laminated were used as the data recording layer 10, where the Co / Ni film stack 10a was Formed of laminated Co film and Ni film; [Co / Ni] _n / Pt film stacks exhibit perpendicular magnetic anisotropy and are suitable for domain wall movement. Pt film 10c was additionally deposited as a cap layer.

[Co / Ni] _n / Pt films exhibit perpendicular magnetic anisotropy when the Co / Ni film stack contained therein has an fcc (111) orientation. However, the crystal orientation of the Co / Ni film stack depends on the material and structure of the underlying layer; The magnitude of the perpendicular magnetic anisotropy also depends on the material and structure of the underlying layer. In Comparative Example 1, the data recording layer 10 was deposited directly on the magnetic lower layer 41 without using the intermediate layer 42B. A NiFeZr film with a thickness of 2.0 nm was used as the magnetic underlayer 41. In this experiment, samples were not patterned to assess intrinsic magnetic properties. That is, the magnetic property of the data recording layer 10 was evaluated in the state of being deposited (in the state of the deposited Pt / [Co / Ni] _n / Pt / NiFeZr film stack). A Vibrating Sample Magnetometer (VSM) was used for the evaluation of the magnetic properties (the same applies hereafter).

First, the magnetic property of the data recording layer 10 will be described before the heat treatment after deposition. 21A and 21B are graphs showing exemplary magnetization curves when an external magnetic field is applied to the data recording layer 10 of the structure shown in FIGS. 20A and 20B. The vertical axis represents the product of magnetization M and the film thickness t (in arbitrary units), and the horizontal axis represents the applied external magnetic field H (Oe). It should be noted that FIG. 21A shows the magnetization curve when the external magnetic field H is applied in the vertical direction of the film surface, and FIG. 21B shows the magnetization curve when the external magnetic field H is applied in the in-plane direction of the film surface. will be. The magnetization curve of the vertical magnetic field (vertical loop shown in FIG. 21A) shows a steep shape, while the magnetization curve of the in-plane magnetic field (in-plane loop shown in FIG. 21B) shows an oblique shape. This suggests that the data recording layer 10 exhibited perpendicular magnetic anisotropy. That is, the [Co / Ni] _n / Pt film stack on the NiFeZr film showed perpendicular magnetic anisotropy, and the [Co / Ni] _n / Pt film stack was likely to be suitable for domain wall movement.

Next, the magnetic properties of the data recording layer 10 after heat treatment in an inert gas at 300 ° C. for 2 hours will be described. 22A and 22B are graphs showing exemplary magnetization curves when an external magnetic field is applied to the data recording layer 10 after the data recording layer 10 of the structure shown in FIGS. 20A and 20B is heat-treated. The vertical axis represents the product of magnetization M and the film thickness t (in arbitrary units), and the horizontal axis represents the applied external magnetic field H (Oe). It should be noted that FIG. 22A shows the magnetization curve when the external magnetic field H is applied in the vertical direction of the film surface, and FIG. 22B shows the magnetization curve when the external magnetic field H is applied in the in-plane direction of the film surface. Compared to FIGS. 21A and 21B, the vertical loop was modified to a more oblique shape as shown in FIG. 22A, while the in-plane loop was modified to a steeper shape, as shown in FIG. 22B. This suggests that the perpendicular magnetic anisotropy of the data recording layer 10 has been degraded by heat treatment at 300 ° C. Also, as can be understood from the comparison between FIGS. 21A and 22A, the product of saturation magnetization and thickness (M _s xt) increased after heat treatment as shown in FIG. 22A. This is derived from the fact that NiFeZr films, which have essentially in-plane magnetic anisotropy, are magnetically bonded to the [Co / Ni] _n / Pt film stack by heat treatment at 300 ° C., causing an increase in magnetization. Magnetic coupling between the NiFeZr film and the [Co / Ni] _n / Pt film degrades the perpendicular magnetic anisotropy of the [Co / Ni] _n / Pt film stack.

Comparative Example 2

In Comparative Example 2, the structure of the data recording layer 10 is Comparative Example 1 (a NiFeZr film was used as the magnetic lower layer 41) except that a Ta film was used in place of the magnetic lower layer 41. Same as the case. When a Ta film was used, the thickness of the Ta film was required to be at least 4.0 nm to achieve the fcc (111) orientation of the Co / Ni film stack. This thickness is very large at about twice the film thickness (2.0 nm) of the NiFeZr film in Comparative Example 1. Due to the large thickness of the Ta film, which is a nonmagnetic material, it was difficult to achieve magnetic coupling between the magnetized pinned layers 50a and 50b and the data recording layer 10 in Comparative Example 2. This potentially leads to the result that the magnetization of the magnetization fixed areas 11a and 11b is not fixed and data cannot be stored in the data recording layer 10.

From Comparative Examples 1 and 2, the inventors avoided unnecessary magnetic coupling between the NiFeZr film and the [Co / Ni] _n / Pt film stack after heat treatment, and the magnetic coupling between the magnetized pinned layers 50a, 50b and the data recording layer 10 In consideration of avoiding the separation of, we have created the following implementation.

[Example 1]

23A and 23B show an exemplary structure of the magnetoresistive effect element of Embodiment 1. FIG. It should be noted that the spacer 20 and the reference layer 30 are not shown. In one example, a SiO ₂ film was used as the interlayer dielectric 60. As in the case of Comparative Example 1, a [Co / Ni] _n / Pt film stack in which a Pt film 10b and a Co / Ni film stack 10a was laminated was used as the data recording layer 10, where Co The / Ni film stack 10a was formed of Co films and Ni films laminated alternately; [Co / Ni] _n / Pt film stacks exhibit perpendicular magnetic anisotropy and are suitable for domain wall movement. Pt film 10c was also additionally deposited as a cap layer.

Embodiment 1 was modified from Comparative Example 1, in which an intermediate layer 42B was inserted between the magnetic lower layer 41 (NiFeZr film) and the data recording layer 10 ([Co / Ni] _n / Pt film stack), It is not magnetically coupled. A Ta film with a thickness of 2.0 nm was used as the intermediate layer 42B. Samples were formed into a Pt / [Co / Ni] _n / Pt / Ta / NiFeZr film stack and then heat treated at 300 ° C. for 2 hours in an inert gas.

Next, the magnetic properties of the data recording layer 10 after heat treatment in an inert gas at 300 ° C. for 2 hours will be described.

24A and 24B are graphs showing exemplary magnetization curves when an external magnetic field is applied to the data recording layer 10 of the structure shown in FIGS. 23A and 23B. The vertical axis represents the product of magnetization M and the film thickness t (in arbitrary units), and the horizontal axis represents the applied external magnetic field H (Oe). It should be noted that FIG. 24A shows the magnetization curve when the external magnetic field H is applied in the vertical direction of the film surface, and FIG. 24B shows the magnetization curve when the external magnetic field H is applied in the in-plane direction of the film surface. will be. As can be understood from the comparison with FIGS. 21A, 21B, 22A, and 22B, the data recording layer 10 of Embodiment 1 showed a more oblique in-plane loop, which was larger vertical magnetic field even after heat treatment at 350 ° C. It means that anisotropy is achieved. In addition, as can be appreciated from the comparison with FIG. 22B, the saturation field Hs (see FIG. 7) was increased in embodiment 1 as shown in FIG. 24B. That is, the data recording layer 10 of Embodiment 1 exhibited a large external magnetic field necessary for directing magnetization in the direction of the external magnetic field as shown in FIG. 24B. As described above, the data recording layer 10 into which the Ta film is inserted as the intermediate layer 42B as shown in FIGS. 23A and 23B is the data recording layer shown in FIGS. 20A and 20B in which the intermediate layer 42B is excluded. It showed greater vertical magnetic anisotropy than (10).

Hereinafter, a description will be given of a change in the port make-up H _s on the thickness of the heat treatment temperature and the intermediate layer (42B). 25 is a graph showing an example of a change in the port make-up H _s on the thickness and heat treatment temperature of the intermediate layer (42B). The vertical axis represents the PO makeup _s H (Oe), the horizontal axis represents the thickness of the Ta film used as the intermediate layer (42B). Circular dots indicate the saturated field H _s obtained after the heat treatment at 200 ° C., and the triangle mark indicates the saturated field H _s obtained after the heat treatment at 350 ° C. For both heat treatment at 200 ° C. and 350 ° C., the data recording layer 10 provided with a Ta film having a thickness of 0.1 nm or more has a higher saturation field H compared to the data recording layer 10 provided with no Ta film. _s and higher vertical magnetic anisotropy. Saturated field H _s was saturated for the configuration where the thickness of the Ta film is at least 2.0 nm. This suggests that it is unnecessary to increase the thickness of the Ta film thicker than 2.0 nm. Rather, if the thickness of the nonmagnetic Ta film is excessively increased, the magnetized pinned layers 50a and 50b cannot be magnetically coupled to the data recording layer 10. This potentially leads to the result that the magnetization of the magnetization fixed areas 11a and 11b is not fixed and data cannot be stored in the data recording layer 10. In addition, increasing the thickness of the magnetic lower layer 41 and the intermediate layer 42B increases the cross-sectional area of the path of the recording current including the data recording layer 10, which may cause difficulty in controlling the recording current due to manufacturing variation. have. Thus, the Ta film preferably has a thickness of 0.1 to 2.0 nm, more preferably 0.2 nm to 1.0 nm.

As can be seen from the above-described results, the insertion of the intermediate layer 42B (for example, Ta film) shows that the data recording layer 10 of FIGS. 23A and 23B, even after a high temperature heat treatment at 350 ° C., Compared with the data recording layer 10 in which 42B is not inserted (that is, the thickness of the Ta film is zero), it was allowed to exhibit high perpendicular magnetic anisotropy. The magnetic coupling between the NiFeZr film (magnetic lower layer 41) having in-plane magnetic anisotropy and the [Co / Ni] _n / Pt film stack (data recording layer 10) is a Ta film (intermediate layer 42B). It can be thought of as originating from the fact that it was suppressed by.

It was also confirmed that magnetic coupling was maintained between the magnetized pinned layers 50a and 50b and the data recording layer 10 even when the sum of the thicknesses of the intermediate layer 42B and the magnetic lower layer 41 was as large as about 4.0 nm. That is, the magnetization of the magnetization fixing regions 11a and 11b is fixed by the magnetization fixing layers 50a and 50b. This is because the increase in total thickness up to 4.0 nm is a result of the increase in the thickness of both the nonmagnetic Ta film and the magnetic NiFeZr film, not the increase in thickness of the nonmagnetic Ta film alone. The magnetic NiFeZr film probably contributes to some degree the magnetic coupling between the magnetization pinned layers 50a and 50b and the data recording layer 10.

As described above, the insertion of a Ta film having a thickness of 0.1 to 2.0 nm as the intermediate layer 42B between the magnetic lower layer 41 and the data recording layer 10 has a perpendicular magnetic anisotropy and a domain wall of the data recording layer 10. Effectively improves fitness for movement Insertion of the Ta film also provides thermal resistance to the data recording layer 10, thereby avoiding the undesirable effect on the magnetic coupling between the magnetized pinned layer and the magnetized pinned area of the data record layer 10. As a result, a magnetic memory in which the data recording layer exhibits strong perpendicular magnetic anisotropy after completion of the manufacturing process of the magnetic memory can be obtained.

[Example 2]

The structure of the data recording layer 10 of Embodiment 2 is similar to that of Embodiment 1; The difference from Embodiment 2 from Embodiment 1 in which the intermediate layer 42B is formed of a Ta film is that a Ru film or an Mg film was used as the intermediate layer 42B. FIG. 26 is a graph showing an example of a magnetization curve in the case where an external magnetic field is applied to the data recording layer having the structure shown in FIGS. 23A and 23B. The vertical axis represents the product of magnetization M and the film thickness t (in arbitrary units), and the horizontal axis represents the applied external magnetic field H (Oe). It should be noted that FIG. 26 shows an in-plane loop which is a magnetization curve when an external magnetic field H is applied in the in-plane direction. In Fig. 26, the magnetization curve E shows the case where a Ta film is used as the intermediate layer 42B (embodiment 1). The magnetization curve F shows the case where the Ru film is used as the intermediate layer 42B, and the magnetization curve G shows the case where the Mg film is used. The thickness of the Ru film, Mg film, and Ta film was 1.0 nm, and the samples were not heat treated.

As shown in FIG. 26, the in-plane loop (magnetization curve E) for the Ta film showed the smallest tilt angle and high saturation field H _s . The difference in the magnetic properties of the Ru film and the Mg film with the Ta film can be considered to be derived from the difference in the fcc (111) orientation of the [Co / Ni] _n / Pt film stack. The above results show that Ta films are quite suitable as interlayer 42B for improving the fcc (111) orientation, which is strongly related to the perpendicular magnetic anisotropy of the [Co / Ni] _n / Pt film stack. The results also showed that Ru films and Mg films are not necessarily suitable as the intermediate layer 42B, at least when they are used separately. The Ru film or Mg film may be usable in the form of a film stack comprising a Ta film.

Configuration of Magnetic Memory and Memory Cells

The magnetoresistive effect elements 100, 100A and 100B of the above-described embodiments can be used as memory cells of the magnetic memory. In the following, an exemplary structure of a magnetic memory and a memory cell will be described in one embodiment.

27 is a block diagram illustrating an exemplary configuration of the magnetic memory 90 in one embodiment of the present invention. The magnetic memory 90 includes a memory cell array, an X driver 92, a Y driver 93, and a controller 94. The memory cell array 91 includes a plurality of memory cells 80 arranged in an array, a plurality of word lines WL, a plurality of bit line pairs BLa and BLb, and a plurality of ground lines GL. Each memory cell 80 is connected to a corresponding word line WL, a corresponding ground line GL, and a corresponding bit line pair BLa, BLb. The X driver 92 drives a word line connected to the memory cell 80 to be accessed, which word line is selected from the plurality of word lines WL. The Y driver 93 is connected to the bit line pairs BLa and BLb and drives each bit line to a desired state in accordance with the write operation and the read operation. The controller 94 controls the X driver 92 and the Y driver 93 in accordance with the write operation and the read operation.

28 is a schematic circuit diagram illustrating an exemplary configuration of a memory cell 80 in one embodiment of the present invention. Each memory cell configured as a 2T-1MTJ structure (two transistors-one magnetic tunnel junction) includes the magnetoresistive effect elements 100, 100A or 100B described above and a pair of transistors TRa and TRb. The magnetoresistive effect element 100, 100A or 100B includes three terminals. The terminal connected to the reference layer 30 of the magnetoresistive element 100, 100A or 100B is connected to the corresponding ground line GL. The terminal connected to the magnetization fixing region 11a of the data recording layer 10 is connected to the corresponding bit line BLa through the transistor TRa and connected to the magnetization fixing region 11b of the data recording layer 10. The connected terminal is connected to the corresponding bit line BLb through the transistor TRb. Gates of the transistors TRa and TRb are commonly connected to the word line WL.

Access to the memory cell 80 is achieved as follows: In the write operation, the word line WL is set to a high level to turn on the transistors TRa and TRb. In addition, one of the bit lines BLa and BLb is set to a high level and the other is set to a low level (ground level). As a result, a write current flows between the bit lines BLa and BLb through the transistors TRa and TRb and the data recording layer 10. This achieves recording the desired data in the data recording layer 10.

In contrast, in the read operation, the word line WL is set to a high level to turn on the transistors TRa and TRb. The bit line BLa is set to a high impedance state and the bit line BLb is set to a high level. As a result, a read current Iread flows from the bit line BLb to the ground line GL through the MTJ of the magnetoresistive effect elements 100, 100A, or 100B. Data stored in the data recording layer 10 of the magnetoresistive effect element is identified by detecting the read current Iread.

Although the embodiments and embodiments of the present invention have been described in detail above, the present invention should not be construed as being limited to only the above-described embodiments and embodiments. It should be noted that the present invention may be implemented with various changes and modifications apparent to those skilled in the art.

Claims (21)

As magnetic memory,
A magnetization fixed layer having a perpendicular magnetic anisotropy and having a fixed magnetization direction;
Interlayer dielectrics;
An underlayer formed on the magnetization pinned layer and upper surfaces of the interlayer dielectric; And
A data recording layer formed on the upper surface of the lower layer and having perpendicular magnetic anisotropy
Including,
The lower layer,
A first magnetic underlayer; And
A non-magnetic underlayer formed on the first magnetic underlayer,
And the first magnetic underlayer is formed to a thickness such that the first magnetic underlayer does not show in-plane magnetic anisotropy in a portion of the first magnetic underlayer formed on the interlayer dielectric. The magnetic memory of claim 1 wherein the thickness of the first magnetic underlayer is adjusted such that the first magnetic underlayer does not show ferromagnetism in a portion of the first magnetic underlayer formed on the interlayer dielectric. The magnetic material of claim 2, wherein the first magnetic underlayer includes NiFe as a main component and includes at least one non-magnetic element selected from the group consisting of Zr, Ta, W, Hf and V. 4. Memory. 4. The magnetic memory of claim 3 wherein the first magnetic underlayer has a thickness in the range of 0.5 to 3 nm. The magnetic memory of claim 4 wherein the thickness of the first magnetic underlayer is less than 2 nm. 4. The magnetic memory of claim 3 wherein the concentration of the at least one nonmagnetic element in the first magnetic underlayer is in the range of 10-25 atomic percent. As magnetic memory,
A magnetization pinned layer having perpendicular magnetic anisotropy and having a fixed magnetization direction;
Interlayer dielectric;
An underlayer formed on the magnetization pinned layer and upper surfaces of the interlayer dielectric; And
A data recording layer formed on an upper surface of the lower layer and having perpendicular magnetic anisotropy
Including,
The lower layer,
A first magnetic underlayer; And
A nonmagnetic underlayer formed on the first magnetic underlayer,
The first magnetic underlayer includes NiFe as a main component and includes at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf, and V,
And the thickness of the first magnetic underlayer is in the range of 0.5 to 3 nm. 8. The magnetic memory of claim 7 wherein the thickness of the first magnetic underlayer is less than 2 nm. 8. The magnetic memory of claim 7 wherein the concentration of the at least one nonmagnetic element in the first magnetic underlayer is in the range of 10-25 atomic percent. 2. The method of claim 1, wherein the first magnetic underlayer is formed of a magnetic material that exhibits essentially in-plane magnetic anisotropy, and is formed to a thickness such that a portion of the first magnetic underlayer disposed on the interlayer dielectric exhibits vertical magnetic anisotropy. Being, magnetic memory. The magnetic memory of claim 10 wherein the first magnetic underlayer includes Co or Fe as a main component and comprises at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf and V. 12. The magnetic memory of claim 11 wherein the thickness of the first magnetic underlayer is in the range of 0.5 to 3 nm. As magnetic memory,
A magnetization pinned layer having perpendicular magnetic anisotropy and having a fixed magnetization direction;
Interlayer dielectric;
An underlayer formed on the magnetization pinned layer and upper surfaces of the interlayer dielectric; And
A data recording layer formed on an upper surface of the lower layer and having perpendicular magnetic anisotropy
Including,
The lower layer,
A first magnetic underlayer; And
A nonmagnetic underlayer formed on the first magnetic underlayer,
The first magnetic underlayer contains Co or Fe as a main component and includes at least one nonmagnetic element selected from the group consisting of Zr, Ta, W, Hf, and V,
And the thickness of the first magnetic underlayer is in the range of 0.5 to 3 nm. The method of claim 1, further comprising a second magnetic lower layer disposed between the nonmagnetic lower layer and the data recording layer,
And the second magnetic underlayer comprises at least one film stack comprising a layer of Pt or Pd and a layer of Fe, Co or Ni. The magnetic memory of claim 1 wherein the nonmagnetic underlayer is formed of a material selected from the group consisting of Pt, Au, Pd and Ir. The magnetic memory according to claim 15, wherein the thickness of the nonmagnetic underlayer is 0.5 nm or more and less than 3.0 nm. The magnetic memory of claim 1 wherein the nonmagnetic underlayer is formed of a Ta film having a thickness of 0.1-2.0 nm. As magnetic memory,
A ferromagnetic underlayer formed of a magnetic material;
A nonmagnetic intermediate layer disposed on the lower layer;
A ferromagnetic data recording layer formed on the intermediate layer and having perpendicular magnetic anisotropy;
A reference layer connected to the data recording layer through a nonmagnetic layer; And
First and second magnetized pinned layers disposed in contact with the lower surface of the lower layer
Including,
The data recording layer,
A magnetization free region having invertible magnetization and opposing the reference layer;
A first magnetization pinning region having magnetization fixed to a first direction and coupled to a first boundary of the magnetization free region; And
A second magnetization fixing region coupled to a second boundary of the magnetization free region and having magnetization fixed in a second direction opposite to the first direction,
And the intermediate layer is formed of a Ta film having a thickness of 0.1 to 2.0 nm. 19. The magnetic element of claim 18 wherein the underlying layer is amorphous or has a microcrystalline structure. 19. The method of claim 18, wherein the lower layer comprises at least one of Ni, Fe, and Co as a main component, and at least one non- selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, W, B and N Magnetic memory containing sex elements. 19. The apparatus of claim 18, wherein the data recording layer is formed of n film stacks, in each of the film stacks, a first layer and a second layer are stacked, n is a natural number,
The first layer comprises at least one material selected from the group consisting of Fe, Co and Ni,
And the second layer is formed of a material different from the material of the first layer and comprises at least one material selected from the group consisting of Fe, Co and Ni.

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