CN204481056U - A kind of magnetoresistive element with double-deck auxiliary layer - Google Patents

Abstract

The utility model provides a magnetoresistance element with double auxiliary layers, which comprises a magnetic reference layer, a magnetic memory layer, a tunnel barrier layer, a first auxiliary layer, a second auxiliary layer and a protection layer. The magnetization direction of the magnetic reference layer is constant and the magnetic anisotropy is perpendicular to the layer surface; the magnetization direction of the magnetic memory layer is variable and the magnetic anisotropy is perpendicular to the layer surface, and the magnetic memory layer is a single layer or a multilayer layer structure; the tunnel barrier layer is disposed between the magnetic memory layer and the magnetic reference layer and is respectively adjacent to the magnetic memory layer and the magnetic reference layer; the first auxiliary layer and the The magnetic memory layer is adjacent, the first auxiliary layer is a metal layer with an electronegativity lower than that of the metal in the magnetic memory layer, and the second auxiliary layer is a metal layer with an electronegativity lower than that of the first auxiliary layer. an electronegative metal layer of the metal in the layer; the protective layer is adjacent to the second auxiliary layer.

Description

A magnetoresistance element with double auxiliary layers

technical field

The utility model relates to the field of memory devices, in particular to a vertical magnetoresistance element.

Background technique

With the continuous progress of material science, a new type of memory—Magnetic Random Access Memory (MRAM, Magnetic Random Access Memory) is attracting people's attention. It has the high-speed read and write capabilities of static random access memory (SRAM), and the high integration of dynamic random access memory (DRAM), and can basically be repeatedly written indefinitely. This high-speed memory has been regarded as the successor of DRAM memory.

The design of MRAM is not complicated, but it has high requirements for materials. For general materials, it is a relatively weak effect. The resistance change caused by the change of the magnetic field is not significant, and it is difficult to judge with a triode. There is already a small change in current.

Magnetic Tunneling Junction (MTJ, Magnetic Tunneling Junction) is a magnetic multilayer film composed of insulators or magnetic materials. Under the action of voltage across the insulating layer, its tunnel current and tunnel resistance depend on the magnetization of the two ferromagnetic layers. Relative orientation, when the relative orientation changes under the action of an external magnetic field, a large tunneling magnetoresistance (TMR) can be observed. The magnetic random access memory made by people using the characteristics of MTJ is non-volatile magnetic random access memory (MRAM). MRAM is a new type of solid-state non-volatile memory, which has the characteristics of high-speed reading and writing, large capacity, and low power consumption. Ferromagnetic MTJ is usually a sandwich structure, in which there is a magnetic memory layer, which can change the magnetization direction to record different data; the tunnel barrier layer is an insulating layer; the magnetic reference layer is located on the other side of the insulating layer, and its magnetization direction is different. changing.

Spin Transfer Torque (STT, Spin Transfer Torque) can be used for the write operation of the magnetoresistive element, that is, when the spin-polarized current passes through the magnetoresistive element, the magnetization direction of the memory layer can be changed through STT. When the volume of the magnetic object in the memory layer becomes smaller, the required polarization current will also become smaller, so that miniaturization and low current can be achieved at the same time.

Perpendicular Magnetic Tunnel Junctions (PMTJ, Perpendicular Magnetic Tunnel Junctions), in this structure, because the magnetic anisotropy of the two magnetic layers is relatively strong (regardless of the shape anisotropy), the easy magnetization direction is perpendicular to the layer surface. Under the same conditions, the size of the device can be made smaller than that of the planar magnetic tunnel junction (that is, the easy magnetization direction is in the plane), and the magnetic polarization error of the easy magnetization direction can be made very small. Therefore, if a material with greater magnetic anisotropy can be found, it can meet the requirements of device miniaturization and low current while maintaining thermal stability.

The high-performance MTJ element is mainly characterized by a high magnetoresistance (MR, Magnetoresistance) rate, MR rate=dR/R, R is the minimum resistance value of the MTJ element, and dR is observed by changing the magnetic state of the memory layer resistance change value. For PMTJ elements, the direction of improving the MR rate mainly focuses on making the magnetic memory layer have better magnetic perpendicular anisotropy and thermal stability. In the prior art, there are many element structures or corresponding elements optimized for the above characteristics. process, but at the same time, the accompanying problem is that due to the spin pump effect, the damping coefficient of the magnetic memory layer becomes larger. Whether it is a vertical or in-plane spin injection MRAM, the write current is proportional to the damping coefficient and inversely proportional to the spin pole. Therefore, the key to reducing the write current is to reduce the damping coefficient and increase the spin polarizability.

Utility model content

Aiming at the above-mentioned problem that both the MR rate and the damping coefficient need to be reduced simultaneously, the utility model provides a magneto-resistive element structure in which two auxiliary layers are added on the magnetic memory layer. In the annealing process (conventional process) for crystallization of the magnetic memory layer, the double-layer auxiliary layer helps the magnetic memory layer to obtain better magnetic perpendicular anisotropy and thermal stability and also has a very small damping coefficient.

The magnetoresistance element of the present utility model comprises:

a magnetic reference layer with a constant magnetization direction and a magnetic anisotropy perpendicular to the layer surface;

A magnetic memory layer, the magnetization direction of the magnetic memory layer is variable and the magnetic anisotropy is perpendicular to the layer surface, and the magnetic memory layer is a single-layer or multi-layer structure;

a tunnel barrier layer, the tunnel barrier layer is arranged between the magnetic memory layer and the magnetic reference layer and is respectively adjacent to the magnetic memory layer and the magnetic reference layer (layer and layer herein "Adjacent" means that the layers are set close to each other, and no other layers are actively set in between);

A first auxiliary layer and a second auxiliary layer arranged adjacently, the first auxiliary layer is adjacent to the magnetic memory layer, and the first auxiliary layer is an electronegativity lower than that of the metal in the magnetic memory layer. a negative metal layer, the second auxiliary layer is a metal layer having an electronegativity lower than that of the metal in the first auxiliary layer;

A protective layer, the protective layer is adjacent to the second auxiliary layer.

Further, the bonding degree of the second auxiliary layer to the B element is stronger than the bonding degree of the first auxiliary layer to the B element.

Further, the material of the first auxiliary layer is Ti, and the thickness range is 1-10 nm.

Further, the material of the second auxiliary layer is one of Zr, Hf, Mg, Al, Mn, Y, Cr, Nb, Ta, and the thickness range is 1-10 nm.

Further, the material of the protective layer is one of Cu, Ru, Al, Rh, Ag, Au.

Further, the magnetic memory layer is a single-layer ferromagnetic boron-containing alloy layer.

Further, the single-layer ferromagnetic boron-containing alloy layer is CoFeB, CoB or FeB, wherein the mole fraction of B is preferably between 10% and 30%, more preferably 20%.

Further, the magnetic memory layer is a three-layer structure adjacent in sequence, the middle layer is made of non-magnetic material, and the other two layers are made of magnetic material.

Further, the tunnel barrier layer is a non-magnetic metal oxide or nitride.

Further, the non-magnetic metal oxide is MgO, ZnO or MgZnO.

The utility model aims at protecting a magneto-resistance element structure before crystallization annealing (conventional process). By adding double-layer auxiliary layers, the magnetic memory layer can significantly improve its magnetic vertical anisotropy and Thermal stability, materials and formation of the auxiliary layer are realized by selecting conventional materials and conventional processes, and the preparation is simple and easy to realize.

The conception, specific structure and technical effects of the present utility model will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, characteristics and effects of the present utility model.

Description of drawings

Fig. 1 is a structural representation of a preferred embodiment of the magnetoresistive element of the present utility model;

Fig. 2 is a structural schematic diagram of the magnetoresistive element in Fig. 1 after being processed by a subsequent process;

Fig. 3 is a structural schematic diagram of another preferred embodiment of the magnetoresistive element of the present invention.

Detailed ways

Fig. 1 is a schematic structural view of an MTJ element based on the present invention, which includes a bottom electrode 1, a base layer 2, a magnetic reference layer 3, a tunnel barrier layer 4, a magnetic memory layer 5, The first auxiliary layer 6 and the second auxiliary layer 7 and the protective layer 8 .

The magnetic reference layer 3 and the magnetic memory layer 5 are ferromagnetic materials, the magnetization direction of the magnetic reference layer 3 is constant and the magnetic anisotropy is perpendicular to the layer surface, the magnetization direction of the magnetic memory layer 5 is variable and the magnetic anisotropy is perpendicular to the layer surface surface. The magnetic perpendicular anisotropy energy of the magnetic reference layer 3 is sufficiently greater than the magnetic perpendicular anisotropy energy of the magnetic memory layer 5, which can be realized by adjusting the material, structure and film thickness of the magnetic reference layer 3, so that when the spin pole When the magnetizing current passes through the MTJ, only the magnetization direction of the magnetic memory layer 5 with a lower energy barrier can be changed, while the magnetization direction of the magnetic reference layer 3 is not affected.

The magnetic memory layer 5 is a single-layer ferromagnetic boron-containing alloy layer, which can be CoFeB, CoB or FeB, wherein the mole fraction of B is preferably between 10% and 30%. In the present embodiment, the material of magnetic memory layer 5 is CoFeB (about 1.2nm in thickness), wherein the mole fraction content of B is 20%, and its deposition state is amorphous; the material structure of magnetic reference layer 3 is CoFeB (about 2nm in thickness). )/TbCoFe (thickness about 20nm). Where "/" represents a multi-layer structure, and the material layer on the left is set on the material layer on the right. It should be noted that the positional descriptions of "up" and "down" referred to in the embodiments are determined according to the display state of the components in the drawings, and are for better description of the drawings. When the angle or position changes, the position description between layers may also need to be changed accordingly according to the actual situation.

The tunnel barrier layer 4 is a non-magnetic insulating metal oxide layer or nitride, such as MgO, ZnO or MgZnO. In this embodiment, the tunnel barrier layer 4 is MgO with a NaCl lattice structure (thickness is about 1 nm), and its (100) crystal plane is parallel to the substrate.

Both the first auxiliary layer 6 and the second auxiliary layer 7 are metal layers, and the electronegativity of the metal is lower than that of the metal (Co and Fe in this embodiment) in the magnetic memory layer 5 . A more optimal choice is that the bonding degree of the second auxiliary layer to the B element is stronger than the bonding degree of the first auxiliary layer to the B element. The main function of the first auxiliary layer 6 and the second auxiliary layer 7 is to realize or enhance magnetic perpendicular anisotropy for the magnetic memory layer 5 . When the magnetic memory layer 5 is thermally annealed, a crystal grain structure will be formed, and its epitaxial growth surface (100) crystal plane is parallel to the surface of the tunnel barrier layer 4, so that the magnetic memory layer 5 has a vertical magnetic anisotropy, which is consistent with At the same time, the B element in the magnetic memory layer 5 migrates into the first auxiliary layer 6 and the second auxiliary layer 7 with lower electronegativity. Due to the spin pump effect, the material in contact with the magnetic memory layer 5 will cause the damping coefficient of the magnetic memory layer 5 to increase, and the first auxiliary layer 6 and the second auxiliary layer 7 can reduce the magnetic field by reducing the spin pump effect. The damping coefficient of memory layer 5. The following metals are arranged in descending order according to their bonding degree with B: Mg, Al, Mn, Y, Cr, Zr, Hf, Nb, Ta, V, Ti. In this embodiment, the material of the first auxiliary layer 6 is Ti (about 2 nm in thickness), and the material of the second auxiliary layer 7 is Zr (about 10 nm in thickness).

The material of the protective layer 8 includes at least one of Cu, Ru, Al, Rh, Ag, and Au. In this embodiment, the material of the protective layer 8 is Ru (about 10 nm in thickness), and the material structure of the base layer 2 is Ta (about 10 nm in thickness). 20nm)/Cu (thickness about 20nm)/Ta (thickness about 20nm).

The subsequent process of the magnetoresistive element of this embodiment will be further described below to better illustrate the beneficial effects of the present invention.

For the magnetoresistive element of this embodiment, the annealing treatment (conventional process) is performed at a high temperature above 250°C, and the B element in the CoFeB of the magnetic memory layer 5 first diffuses to the first auxiliary layer 6, which is due to the electronegativity of Ti lower than Co and Fe; and then diffuse into the second auxiliary layer 7 because Zr has lower electronegativity and stronger bonding with B than Ti. The diffused B element forms TiB2 and ZrB2 with Ti in the first auxiliary layer 6 and Zr in the second auxiliary layer, respectively. At the same time, the amorphous CoFeB is crystallized into bcc phase CoFe crystal particles, and its epitaxial growth plane (100) crystal plane is parallel to the MgO surface of the tunnel barrier layer 4 . The thickness of the first auxiliary layer 6 and the second auxiliary layer 7 is sufficient to fully absorb enough B elements, and the gradient (electronegativity, bonding degree with B) of the double layer is set to be more conducive to the absorption of B elements, so that CoFe It can be epitaxially formed into a bcc phase lattice structure better. Typical pure CoFe has a damping coefficient of about 0.003, while CoFeB has a damping coefficient of 0.01. This makes it possible to form magnetic perpendicular anisotropy with low damping in the magnetic memory layer 5 .

After the annealing treatment, reactive ion etching (RIE, Reactive Ion Etching) can be used to etch and remove the protective layer 8 and the second auxiliary layer 7, leaving the first auxiliary layer 6, so as to facilitate the subsequent photolithography process, as shown in Figure 2 .

Fig. 3 is a structural schematic diagram of another MTJ element based on the utility model, and the difference from the above-mentioned embodiment is that the magnetic memory layer 5 adopts a three-layer structure, which is respectively a magnetic sublayer 5A and a nonmagnetic intermediate sublayer from top to bottom. Layer 5B and magnetic sublayer 5C, materials are respectively CoFeB (about 0.8nm), Ta (about 0.3nm), CoFeB (about 0.6nm), preferably, the Fe content of magnetic sublayer 5C is higher than that of magnetic sublayer 5A layer , which is more helpful to improve the MR rate. In addition, when the MTJ is heat-treated, B atoms will also diffuse into the non-magnetic intermediate sublayer 5B, which is more helpful to improve its perpendicular magnetic anisotropy.

The preferred specific embodiments of the present utility model have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the utility model without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the utility model through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection defined by the claims .

Claims (10)

1. A magnetoresistive element, comprising a magnetic reference layer with a constant magnetization direction and a magnetic anisotropy perpendicular to the layer surface; A magnetic memory layer, the magnetization direction of the magnetic memory layer is variable and the magnetic anisotropy is perpendicular to the layer surface, and the magnetic memory layer is a single-layer or multi-layer structure; a tunnel barrier layer, the tunnel barrier layer is disposed between the magnetic memory layer and the magnetic reference layer and is respectively adjacent to the magnetic memory layer and the magnetic reference layer; It is characterized in that it also includes A first auxiliary layer and a second auxiliary layer arranged adjacently, the first auxiliary layer is adjacent to the magnetic memory layer, and the first auxiliary layer is an electronegativity lower than that of the metal in the magnetic memory layer. a negative metal layer, the second auxiliary layer is a metal layer having an electronegativity lower than that of the metal in the first auxiliary layer; A protective layer, the protective layer is adjacent to the second auxiliary layer. 2 . The magnetoresistive element according to claim 1 , wherein the degree of bonding between the second auxiliary layer and element B is stronger than the degree of bonding between the first auxiliary layer and element B. 3 . 3 . The magneto-resistive element according to claim 1 , wherein the material of the first auxiliary layer is Ti, and the thickness ranges from 1 to 10 nm. 4 . 4. The magneto-resistive element according to claim 1, wherein the material of the second auxiliary layer is one of Zr, Hf, Mg, Al, Mn, Y, Cr, Nb, Ta, and the thickness range is It is 1 to 10 nm. 5. The magnetoresistive element according to claim 1, characterized in that, the material of the protective layer is one of Cu, Ru, Al, Rh, Ag, Au. 6. The magnetoresistive element according to claim 1, wherein the magnetic memory layer is a single-layer ferromagnetic boron-containing alloy layer. 7. The magneto-resistive element according to claim 6, wherein the material of the single-layer ferromagnetic boron-containing alloy layer is CoFeB, CoB or FeB. 8. The magneto-resistive element according to claim 1, wherein the magnetic memory layer is a three-layer structure adjacent in sequence, the middle layer is made of non-magnetic material, and the remaining two layers are made of magnetic material. 9. The magnetoresistive element according to claim 1, wherein the tunnel barrier layer is a non-magnetic metal oxide or nitride. 10. The magnetoresistive element according to claim 9, wherein the non-magnetic metal oxide is MgO, ZnO or MgZnO.