WO2021212780A1

WO2021212780A1 - Magnetic tunnel junction and manufacturing method therefor

Info

Publication number: WO2021212780A1
Application number: PCT/CN2020/121892
Authority: WO
Inventors: 孙一慧; 孟凡涛; 蒋信; 韩谷昌
Original assignee: 浙江驰拓科技有限公司
Priority date: 2020-04-21
Filing date: 2020-10-19
Publication date: 2021-10-28
Also published as: CN111509120A

Abstract

The present invention provides a magnetic tunnel junction and a manufacturing method therefor. The magnetic tunnel junction comprises a first seed crystal layer, a second seed crystal layer, a magnetic pinned layer, a barrier layer, a magnetic free layer, and a capping layer which are stacked in sequence; the first seed crystal layer contains a non-nickel alloy formed by boron and one of cobalt and iron or a combination thereof, and the second seed crystal layer contains a nickel-chromium alloy. According to the present invention, the perpendicular magnetic anisotropy of each magnetic layer is improved by using the second seed crystal layer containing the nickel-chromium alloy.

Description

Magnetic tunnel junction and manufacturing method thereof

Technical field

The invention relates to the technical field of magnetic memory, in particular to a magnetic tunnel junction and a manufacturing method thereof.

Background technique

In recent years, people use the characteristics of Magnetic Tunnel Junction (MTJ) to make magnetic random access memory, that is, MRAM (Magnetic Random Access Memory). MRAM is a new type of solid-state non-volatile memory, which has the characteristics of high-speed reading and writing. Ferromagnetic MTJ is usually a sandwich structure, which has a free layer, which can change the magnetization direction to record different data; an insulating barrier layer located in the middle; a reference layer, located on the other side of the barrier layer, its magnetization direction is Changeless. When the direction of the magnetization vector between the free layer and the reference layer is parallel or anti-parallel, the resistance state of the MTJ element is also a low resistance state or a high resistance state respectively. In this way, the stored information can be obtained by measuring the resistance state of the MTJ element.

Perpendicular Magnetic Tunnel Junction (pMTJ, Perpendicular Magnetic Tunnel Junction) is a magnetic tunnel junction with a magnetic moment perpendicular to the surface of the substrate. According to the relative position of the reference layer and the free layer, the vertical magnetic tunnel junction is divided into top type (the reference layer is at the top). Top) and bottom type (reference layer below) pMTJ. In the pMTJ structure, since the Perpendicular Magnetic Anisotropy (PMA) of the two magnetic layers is relatively strong (regardless of shape anisotropy), the easy magnetization directions are perpendicular to the layer surface. Under the same conditions, the size of the pMTJ element can be made smaller than the in-plane MTJ element, the magnetic polarization error in the easy magnetization direction can be made small, and the size of the MTJ element can be reduced so that the required switching current can be correspondingly Decrease.

Therefore, the vertical magnetic tunnel junction pMTJ using PMA has high thermal stability and low switching current. In practical applications, how to improve the PMA of each magnetic layer in the pMTJ and provide a flat substrate for the pMTJ has become an urgent need to solve The problem.

Summary of the invention

In view of this, the present invention provides a magnetic tunnel junction and a manufacturing method thereof, which can improve the perpendicular magnetic anisotropy of each magnetic layer.

In a first aspect, the present invention provides a magnetic tunnel junction, which includes a first seed layer, a second seed layer, a magnetic pinned layer, a barrier layer, a magnetic free layer, and a cover layer which are sequentially stacked, wherein:

The first seed layer includes a non-nickel alloy formed by one of cobalt, iron or a combination of boron, and is used to provide a flat and lattice-matched substrate for the second seed layer;

The second seed layer is located on the top surface of the first seed layer and includes a nickel-chromium alloy;

The magnetic pinned layer is adjacent to the second seed layer, and the magnetization direction of the magnetic pinned layer is unchanged and perpendicular to the surface of the magnetic pinned layer film;

The magnetization direction of the magnetic free layer is variable and perpendicular to the surface of the magnetic free layer film;

The barrier layer is located between the magnetic pinned layer and the magnetic free layer;

The cover layer is located on the top surface of the magnetic free layer and is used to protect the magnetic free layer.

Optionally, the material of the first seed layer includes one or more of CoB, FeB and CoFeB.

Optionally, the material of the second seed layer includes one or more of NiCr and NiFeCr.

Optionally, the thickness of the first seed layer is between 1 and 5 nanometers.

Optionally, the thickness of the second seed layer is between 1-10 nanometers.

Optionally, the magnetic pinned layer includes a synthetic antiferromagnetic pinned layer, a magnetic spacer layer, and a magnetic reference layer, wherein:

The structure of the synthetic antiferromagnetic pinning layer is [Co/X]n/Co/Y/Co/[X/Co]m, where X is one of Ni, Pd or Pt, and the thickness of X is between At 0.2-1.0 nm, Y is one of Ru or Ir, the thickness of Y is between 0.4-0.9 nm, n and m are the number of superlattice layers, n is 3-8 layers, and m is 0-6 layers;

The magnetic reference layer includes various combinations of CoFeB, the magnetic reference layer has an amorphous structure before annealing, and transforms into a body-centered cubic lattice structure after annealing;

The magnetic spacer layer uses one of Ta, W, Mo, Hf, V, Zr and alloys thereof.

Optionally, the barrier layer is made of MgO, MgZnO or MgAlO, and the thickness of the barrier layer is between 0.5-2 nanometers.

Optionally, the magnetic free layer adopts CoFeB, CoFeB/Fe or CoFeB/β/CoFeB, where β is one of Ta, Mo, W, Hf, Zr or Fe, and the thickness of the magnetic free layer is between 0.5-5 nanometers; the magnetic free layer changes from an amorphous structure to a body-centered cubic lattice structure after annealing.

Optionally, the covering layer is made of at least one oxide of Mg and Al, and the thickness of the covering layer is between 0.2-2 nanometers.

In the second aspect, the present invention provides a method for manufacturing a magnetic tunnel junction, which includes the following steps:

Depositing a first seed layer on the substrate;

Depositing a second seed layer on the first seed layer;

Forming a synthetic antiferromagnetic pinning layer on the second seed layer;

Forming a magnetic spacer layer on the synthetic antiferromagnetic pinning layer;

Forming a magnetic reference layer on the magnetic spacer layer;

Forming a barrier layer on the magnetic reference layer;

Forming a magnetic free layer on the barrier layer;

Forming a covering layer on the magnetic free layer, and thus forming a magnetic tunnel junction multilayer film;

Annealing is performed after the formation of the magnetic tunnel junction multilayer film, the annealing temperature is 300-450°C, and the annealing time is 0.2-2 hours.

The magnetic tunnel junction and the manufacturing method thereof provided by the present invention utilize two seed layers to deposit a NiCr seed layer on the cobalt-iron-boron seed layer, and NiCr diffuses into the magnetic fixed layer, so that the magnetic moment direction of the magnetic fixed layer is changed. Vertical and more stable; the stable magnetic pinned layer can make the magnetic free layer flip more stable, and the RH loop uniformity is better.

Description of the drawings

FIG. 1 is a schematic structural diagram of a magnetic tunnel junction provided by an embodiment of the present invention;

FIG. 2 is a process flow diagram of a method for manufacturing a magnetic tunnel junction according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

This embodiment provides a magnetic tunnel junction. As shown in FIG. 1, the magnetic tunnel junction includes: a first seed layer 10, a second seed layer 20, a magnetic pinned layer 30, a barrier layer 40, and a magnetic Free layer 50 and cover layer 60.

The first seed layer 10 adopts a non-nickel alloy formed by one or a combination of cobalt and iron with boron, such as CoB, FeB, CoFeB, etc., with a thickness ranging from 1-5 nanometers. The first seed layer 10 is the second The seed layer 20 provides a flat and lattice-matched substrate.

The second seed layer 20 is made of a material containing a nickel-chromium alloy, such as NiCr, NiFeCr, etc., with a thickness in the range of 1-10 nanometers.

The magnetization direction of the magnetic pinned layer 30 is constant and perpendicular to the surface of the magnetic pinned layer film, which in turn includes:

The first superlattice multilayer film 301 has a structure of [Co/X]n, where the thickness of Co is generally 0.3-0.6 nanometers, X is Ni, Pd or Pt, the thickness is generally 0.2-1.0 nanometers, and n is generally selected as 3-8;

The thickness of the first Co layer 302 is generally 0.4-0.6 nanometers;

The AP coupling layer 303 is generally Ru or Ir, and the thickness is generally 0.4-0.9 nm;

The thickness of the second Co layer 304 is generally 0.4-0.6 nanometers;

The second superlattice multilayer film 305 has a structure of [X/Co]m, where the thickness of Co is generally 0.3-0.6 nanometers, X is Ni, Pd or Pt, the thickness is generally 0.2-1.0 nanometers, and m is generally selected as 0-6;

The magnetic spacer layer 306 is made of one of Ta, W, Mo, Hf, V, Zr and alloys thereof, and the thickness is generally 0.2-0.5 nanometers;

The magnetic reference layer 307 includes various combinations of CoFeB, and the thickness is generally 0.5-1.5 nanometers. The magnetic reference layer 307 has an amorphous structure before annealing, and transforms into a body-centered cubic (BCC) lattice structure after annealing.

Among them, the first superlattice multilayer film 301, the first Co layer 302, the AP coupling layer 303, the second Co layer 304, and the second superlattice multilayer film 305 together constitute a synthetic antiferromagnetic (SAF) pinning layer , Used to pin the magnetization direction of the magnetic reference layer 307.

The barrier layer 40 is made of dielectric insulating materials, such as oxide insulating materials such as MgO, MgZnO, MgAlO, etc., and the preferred thickness is in the range of 0.5-2 nanometers.

The magnetization direction of the magnetic free layer 50 is variable and perpendicular to the surface of the magnetic free layer film, which adopts CoFeB, CoFeB/Fe or CoFeB/β/CoFeB, where β is one of Ta, Mo, W, Hf, Zr or Fe , The preferred thickness range is 0.5-5 nanometers. The magnetic free layer 50 has an amorphous structure before annealing, and transforms into a body-centered cubic (BCC) lattice structure after annealing.

The covering layer 60 uses at least one of Mg and Al oxides, such as MgO and MgAlO, and the thickness of the covering layer 60 is between 0.2-2 nanometers.

The above embodiments have obtained the magnetic tunnel junction multilayer film. Finally, the formed magnetic tunnel junction multilayer film is subjected to high-temperature annealing, and the temperature range is between 300-450°C. The non-magnetic reference layer 307 and the magnetic free layer 50 are The crystalline CoFeB transforms into a body-centered cubic (BCC) lattice structure. In the above embodiment, the first seed layer 10 cannot be too thick. If the first seed layer 10 is too thick, it will cause too strong magnetism and become in-plane, affecting the magnetization direction of the magnetic pinned layer 30; The layer 20 cannot be too thin. If the second seed layer 20 is too thin, it will lose its role as a stress buffer layer and cannot provide a flat base for the magnetic pinned layer 30, but the first seed layer 10 and the second seed layer 20 The two do not have a certain relative thickness requirement.

The magnetic tunnel junction provided in this embodiment uses two seed layers to deposit a NiCr seed layer on the cobalt-iron-boron seed layer, and NiCr diffuses into the first superlattice multilayer film (such as Co/Pt), The elastic stress caused by the lattice mismatch provides the stronger PMA of the first superlattice; after the stronger PMA is coupled through SAF, the direction of the magnetic moment of the magnetic reference layer is more vertical and more stable; the stable magnetic reference layer It can make the free layer flip more stable, and the RH loop has better uniformity.

Further, another embodiment of the present invention provides a manufacturing method of a magnetic tunnel junction, which is used to manufacture the magnetic tunnel junction of the foregoing embodiment. FIG. 2 shows the entire process flow of the manufacturing method, which specifically includes the following steps:

Depositing a first seed layer on the substrate;

Depositing a second seed layer on the first seed layer;

Forming a synthetic antiferromagnetic pinning layer on the second seed layer, and the synthetic antiferromagnetic pinning layer has a composite superlattice multilayer film structure;

Forming a magnetic reference layer on the magnetic spacer layer;

Forming a barrier layer on the magnetic reference layer;

A magnetic free layer is formed on the barrier layer;

A covering layer is formed on the magnetic free layer, and a magnetic tunnel junction multilayer film is formed so far;

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. All should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

A magnetic tunnel junction, characterized in that it comprises a first seed layer, a second seed layer, a magnetic pinned layer, a barrier layer, a magnetic free layer and a cover layer which are sequentially stacked, wherein:

The first seed layer includes a non-nickel alloy formed by one of cobalt, iron or a combination of boron, and is used to provide a flat and lattice-matched substrate for the second seed layer;

The second seed layer is located on the top surface of the first seed layer and includes a nickel-chromium alloy;

The magnetic fixed layer is adjacent to the second seed layer, and the magnetization direction of the magnetic fixed layer is unchanged and perpendicular to the surface of the magnetic fixed layer film;

The magnetization direction of the magnetic free layer is variable and perpendicular to the surface of the magnetic free layer film;

The barrier layer is located between the magnetic pinned layer and the magnetic free layer;

The cover layer is located on the top surface of the magnetic free layer.
The magnetic tunnel junction according to claim 1, wherein the material of the first seed layer contains one or more of CoB, FeB and CoFeB.
The magnetic tunnel junction according to claim 1, wherein the material of the second seed layer contains one or more of NiCr and NiFeCr.
The magnetic tunnel junction according to claim 1, wherein the thickness of the first seed layer is between 1 and 5 nanometers.
The magnetic tunnel junction of claim 1, wherein the thickness of the second seed layer is between 1-10 nanometers.
The magnetic tunnel junction according to claim 1, wherein the magnetic pinned layer comprises a synthetic antiferromagnetic pinning layer, a magnetic spacer layer and a magnetic reference layer, wherein:

The structure of the synthetic antiferromagnetic pinning layer is [Co/X]n/Co/Y/Co/[X/Co]m, where X is one of Ni, Pd or Pt, and the thickness of X is between At 0.2-1.0 nm, Y is one of Ru or Ir, the thickness of Y is between 0.4-0.9 nm, n and m are the number of superlattice layers, n is 3-8 layers, and m is 0-6 layers;

The magnetic reference layer includes various combinations of CoFeB, the magnetic reference layer has an amorphous structure before annealing, and transforms into a body-centered cubic lattice structure after annealing;

The magnetic spacer layer uses one of Ta, W, Mo, Hf, V, Zr and alloys thereof.
The magnetic tunnel junction according to claim 1, wherein the barrier layer is made of MgO, MgZnO or MgAlO, and the barrier layer has a thickness of 0.5-2 nanometers.
The magnetic tunnel junction according to claim 1, wherein the magnetic free layer uses CoFeB, CoFeB/Fe or CoFeB/β/CoFeB, wherein β is one of Ta, Mo, W, Hf, Zr or Fe The thickness of the magnetic free layer ranges from 0.5 to 5 nanometers; the magnetic free layer changes from an amorphous structure to a body-centered cubic lattice structure after annealing.
The magnetic tunnel junction according to claim 1, wherein the covering layer is made of at least one of Mg and Al oxide, and the thickness of the covering layer is between 0.2-2 nanometers.
A method for manufacturing a magnetic tunnel junction is characterized in that it comprises the following steps:

Depositing a first seed layer on the substrate;

Depositing a second seed layer on the first seed layer;

Forming a synthetic antiferromagnetic pinning layer on the second seed layer;

Forming a magnetic spacer layer on the synthetic antiferromagnetic pinning layer;

Forming a magnetic reference layer on the magnetic spacer layer;

Forming a barrier layer on the magnetic reference layer;

Forming a magnetic free layer on the barrier layer;

Forming a covering layer on the magnetic free layer, and thus forming a magnetic tunnel junction multilayer film;

Annealing is performed after the formation of the magnetic tunnel junction multilayer film, the annealing temperature is 300-450°C, and the annealing time is 0.2-2 hours.