CN113451504B

CN113451504B - Magnetic random access memory cell with composite seed layer structure

Info

Publication number: CN113451504B
Application number: CN202010214288.8A
Authority: CN
Inventors: 郭一民; 肖荣福; 陈峻; 麻榆阳
Original assignee: Shanghai Information Technologies Co ltd
Current assignee: Shanghai Information Technologies Co ltd
Priority date: 2020-03-24
Filing date: 2020-03-24
Publication date: 2023-03-24
Anticipated expiration: 2040-03-24
Also published as: CN113451504A

Abstract

The application discloses a composite seed layer structure and a magnetic random access memory storage unit thereof. The composite seed layer of the magnetic random access memory cell is positioned between the bottom electrode and the antiparallel ferromagnetic superlattice layer. In order to ensure the normal operation of the magnetic random access memory, the composite seed layer below the antiparallel ferromagnetic superlattice layer is required to have ultrahigh flatness, and the lattice constant of the composite seed layer is required to be highly matched with the antiparallel ferromagnetic superlattice layer. In the prior art, the composite seed layer is usually Pt grown by PVD, and the thickness of the Pt is more than 5nm. The invention adopts a composite seed layer with a multilayer structure containing metallic copper or copper nitride, increases the vertical magnetic anisotropy of an antiparallel ferromagnetic superlattice layer, simultaneously reduces the production cost and avoids the problem that thicker Pt is difficult to etch on the premise of ensuring the normal work of a magnetic random access memory.

Description

Magnetic random access memory cell with composite seed layer structure

Technical Field

The invention relates to the technical field of memories, in particular to a magnetic random access memory storage unit with copper or copper nitride as a composite seed layer.

Background

In recent years, a perpendicular spin-electron torque Magnetic memory (pSTT-MRAM) using a Magnetic Tunnel Junction (MTJ) has characteristics of non-volatility, high-speed writing and reading, large capacity, and low power consumption, and is considered to be one of the most promising future memories. The basic structure of a Magnetic Tunnel Junction (MTJ) includes a bottom electrode, a seed layer, an antiparallel ferromagnetic superlattice layer, a lattice partition layer, a reference layer, a barrier layer, a free layer, a capping layer, and a top electrode. All the above structures are deposited sequentially by using Physical Vapor Deposition (PVD) method.

Tunneling Magnetoresistance (TMR) refers to the effect of tunneling resistance in a ferromagnetic-insulator thin film (about 1 nm) -ferromagnetic material that varies in magnitude with the relative orientation of the ferromagnetic materials on both sides. The magnetic memory TMR size determines the read speed of the magnetic memory. The low TMR can reduce the read speed of the magnetic memory, greatly affecting the performance of the magnetic memory. It is theoretically calculated that the TMR of the Magnetic Tunnel Junction (MTJ) with FeCoB/MgO/FeCoB as the basic structure is more than 2000% when RA =10ohm. But the TMR is generally not more than 300% at RA =10ohm. Um2 using a Physical Vapor Deposition (PVD) method and a FeCoB/MgO/FeCoB based vertical type magnetic tunnel junction. In 2008, the s.ikeda, h.ohno team at northeast university of japan reported that the resistivity of the planar magnetic tunnel junction CoFeB/MgO/CoFeB reached 604% at room temperature. There are many reasons for the large difference between the theoretical value and the actual value of TMR, where the flatness and lattice matching of the bottom electrode, seed layer and antiparallel ferromagnetic superlattice layer of the magnetic tunnel junction have a large effect on TMR.

To ensure that the Magnetic Tunnel Junction (MTJ) can work properly, all layers need to ensure high flatness, and the crystal structure and lattice constant between layers need to be matched. In order to ensure high flatness and matching of crystal structures, the processes of the bottom electrode at the bottom of the magnetic tunnel junction, the seed layer and the antiparallel ferromagnetic superlattice layer are particularly important. The bottom electrode is deposited over the CMOS after a chemical mechanical polishing process (CMP). The CMOS adopting the chemical mechanical polishing process has higher flatness. The seed layer is deposited on the bottom electrode and under the antiferromagnetic layer, and its crystal structure and lattice constant are basically matched with those of the upper and lower layers, so that the higher Perpendicular Magnetic Anisotropy (PMA) required by the memory cell of the device can be obtained. The antiparallel ferromagnetic superlattice layer has higher requirements on the flatness and lattice matching of the bottom electrode and the seed layer.

In the prior art, relatively thick Pt, typically greater than 5nm, is used as the seed layer. Pt matches the lattice constant of the upper antiparallel ferromagnetic superlattice layer but does not match the lattice constant of the lower bottom electrode. It is desirable to deposit a thicker layer of Pt to function as a lattice transition. On one hand, the method is relatively expensive, and on the other hand, the method also brings difficulties to the subsequent etching process.

The TMR determines the read speed of the magnetic memory. The low TMR can reduce the read speed of the magnetic memory, greatly affecting the performance of the magnetic memory. The improvement of TMR has become one of the current technical problems to be solved. Optimizing the material and process conditions of the seed layer is one of the important ways to improve TMR.

Disclosure of Invention

In order to solve the above-mentioned problems, an objective of the present application is to provide a magnetic random access memory cell containing copper or copper nitride as a composite seed layer.

The purpose of the application and the technical problem to be solved are realized by adopting the following technical scheme.

According to the magnetic random access memory storage unit containing copper or copper nitride as a composite seed layer, a bottom electrode, the composite seed layer, an antiparallel ferromagnetic superlattice layer, a reference layer, a barrier layer, a free layer, a covering layer and a top electrode are sequentially deposited.

Further, the bottom electrode is made of TiN, ti, ta, taN, W, WN or a combination material thereof; tiN/Ta is preferred. Ta deposited using Physical Vapor Deposition (PVD) has a Body Centered Cubic (BCC) crystal structure with a lattice constant of 3.30 angstroms.

Further, the composite seed layer comprises: the copper-containing layer is arranged on the bottom electrode and is made of copper or copper nitride; a lattice stabilization layer disposed on the copper-containing layer; and the platinum (Pt) or palladium (Pd) metal layer is arranged on the lattice stabilizing layer.

Further, the thickness of the copper-containing layer is 1-20nm; the thickness of the platinum or palladium metal layer is 1-5nm.

Further, the composite seed layer is made of Cu/X/Pt, cuN/X/Pt, (Cu/X/Pt) n, (Cu/X) n/Pt or (CuN/X/Pt) n, wherein n is an integer of 2-6. The material of X (the lattice stabilization layer) is W, mo, nb, hf, ta, ru, rh or Ir, and the thickness is 0-1.0nm. Cu or CuN (copper-containing layer) has a Face Centered Cubic (FCC) crystal structure with a lattice constant of 3.61-3.88 angstroms. The lattice constant of CuN more approaches 3.88 angstroms as the nitrogen content increases. Pt has a Face Centered Cubic (FCC) crystal structure with a lattice constant of 3.9 angstroms. The Co in the antiparallel ferromagnetic superlattice layer also has a Face Centered Cubic (FCC) crystal structure with a lattice constant of 3.54 angstroms. The Cu or CuN is arranged on the Ta bottom electrode, and can easily grow into a face-centered cubic (FCC) crystal structure, and the lattice constant of the Cu or CuN is close to that of Pt and Co and is matched with the lattice. The thinner X between CuN and Pt also serves to stabilize the lattice and to block copper diffusion.

Further, the copper-containing layer and the platinum or palladium (Pt or Pd) layer are both deposited in a physical vapor deposition process chamber.

Further, after the platinum or palladium (Pt or Pd) layer is deposited, the surface treatment is further kept in vacuum and is performed by plasma etching, so that the surface flatness is improved.

Further, the lattice stabilization layer is deposited in a physical vapor deposition process cavity.

Further, the composite seed layer further comprises a structure repeated a plurality of times: x (copper-containing layer/lattice-stabilizing layer/platinum or palladium layer) or x/platinum or palladium layer, x being a positive integer not greater than 6.

Further, the antiparallel ferromagnetic superlattice layer includes a lower ferromagnetic superlattice layer, an antiparallel ferromagnetic coupling layer, and an upper ferromagnetic layer, the antiparallel ferromagnetic superlattice layer having [ Co/Pt ] nCo/(Ru, ir, or Rh), [ Co/Pt ] nCo/(Ru, ir, or Rh)/Co [ Pt/Co ] m, [ Co/Pd ] nCo/(Ru, ir, or Rh), [ Co/Pd ] nCo/(Ru, ir, or Rh)/Co [ Pd/Co ] m, [ Co/Ni ] nCo/(Ru, ir, or Rh), or [ Co/Ni ] nCo/(Ru, ir, or Rh)/Co [ Ni/Co ] m superlattice structure, where n is 1,m. Preferably, the structure is one of the following bottom-up structures: (Co/(Pt or Pd)) n/Co/(Ru or Ir)/Co/((Pt or Pd)/Co) m, or (Co/(Pt or Pd)) nCo/Ru/(W, mo or Cr), n is an integer of 1-6, and m is an integer of 0-3.

Further, a lattice partition layer is further included between the reference layer and the antiparallel ferromagnetic superlattice layer, and the material of the lattice partition layer is selected from W, mo, nb, hf and Ta. Preferably, the lattice barrier layer is made of Ta, W, mo, hf, fe, co (Ta, W, mo or Hf), fe (Ta, W, mo or Hf), feCo (Ta, W, mo or Hf) or FeCoB (Ta, W, mo or Hf) and has a thickness of 0.15nm to 0.4nm. The anti-parallel ferromagnetic superlattice layer has a Face Centered Cubic (FCC) crystal structure, while the reference layer has a Body Centered Cubic (BCC) crystal structure, and if the two layers are in direct contact, crystal lattices can not be matched, so that TMR can be greatly reduced.

Furthermore, the total thickness of the reference layer is 0.8nm to 1.5nm, and the composition material is a ferromagnetic material, generally FeCoB, coB, feB, fe and other materials. The atomic percent of B in FeB or CoB is 15-40%; in the CoFeB alloy, co: the atomic ratio of Fe is 1:3 to 3:1; 15 to 40 percent;

further, the barrier layer is made of a non-magnetic metal oxide or metal, preferably a three-layer structure of MgO or MgO/Mg/MgO, and has a total thickness of 0.8-1.5nm.

Further, the total thickness of the free layer is 1.5nm to 2.5nm, and the composition material is ferromagnetic material, typically Co/(Pt, pd, ni or Ir)/(CoFeB, coB or FeB), (CoFeB, coB or FeB)/(Pt, pd, ni or Ir)/Co, (CoFeB, coB or FeB)/Co/(Pt, pd, ni or Ir)/Co, (CoFeB, coB or FeB)/(Pt, pd, ni or Ir)/(CoFeB, coB or FeB), co/(Pt, pd, ni or Ir)/Co/(CoFeB, coB or FeB), (CoFeB, coB or FeB)/X/Co/(Pt, pd, ni or Ir)/Co/X/(CoFeB, coB or FeB), (CoFeB, coB or FeB)/X/Co/(Pt, pd, ni or Ir), co/(Pt, pd, ni or Ir)/Co/X/(CoFeB, coB or FeB),

wherein X is W, mo, V, nb, cr, hf, ti, zr, ta, sc, Y, zn, ru or Os etc., and the thickness is 0.2-0.5nm.

The atomic percent of B in FeB or CoB is 15-40%; in the CoFeB alloy, co: the atomic ratio of Fe is 1:3 to 3:1; the atomic percent of B is 15% -40%;

furthermore, the covering layer is formed by sequentially depositing multiple materials such as MgO, pt, coFeB, coFeC, W, mo, mg, nb, ru, hf, V, cr and the like, and preferably has a structure of MgO/(W, mo, hf)/Ru or MgO/Pt/(W, mo, hf)/Ru.

Further, the top electrode is made of Ta, taN, ti, tiN, W, WN or a combination thereof.

Further, after the bottom electrode, the composite seed layer, the antiparallel ferromagnetic superlattice layer, the lattice partition layer, the reference layer, the barrier layer, the free layer, the capping layer, and the top electrode are deposited, an annealing operation is performed at a temperature of 400 ℃ for 60 to 90 minutes. The annealing process causes some materials of Physical Vapor Deposition (PVD) to change from an amorphous state to a crystalline state, thereby providing a Magnetic Tunnel Junction (MTJ) with a tunneling magnetoresistance effect.

The application provides a magnetic tunnel junction structure with a lattice promoting layer, which requires that a composite seed layer below an antiparallel ferromagnetic superlattice layer has ultrahigh flatness and the lattice constant of the composite seed layer is highly matched with the antiparallel ferromagnetic superlattice layer in order to ensure the normal work of a magnetic random access memory. Furthermore, in the deposition process of the composite seed layer before the anti-parallel ferromagnetic superlattice layer (SyAF), the FCC (111) lattice promoting layer (CPL) and the growth process thereof are adopted, and the composite seed layer with the multilayer structure containing metallic copper or copper nitride is combined, so that the anti-parallel ferromagnetic superlattice layer (SyAF) has strong face-centered cubic structures (FCC (111) and PMA), and meanwhile, on the premise of ensuring the normal work of the magnetic random access memory, the production cost is reduced, and the problem that the thick Pt is difficult to etch is avoided. The method is very beneficial to the improvement of magnetism, electricity and yield of the whole MTJ unit and the miniaturization of devices.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a MRAM cell according to the present application;

wherein the reference numerals include: 110-bottom electrode, 210-composite seed layer, 220-antiparallel ferromagnetic superlattice layer, 221-lower ferromagnetic layer, 222-antiparallel ferromagnetic coupling layer, 223-upper ferromagnetic layer, 230-lattice partition layer, 240-reference layer, 250-barrier layer, 260-free layer, 261-free layer (I), 262-coupling layer, 263-free layer (II), 280-capping layer, 310-hard mask layer.

FIG. 2-a is a schematic view of an embodiment of a compound seed layer of a magnetic random access memory according to the present invention.

FIG. 2-b is a schematic diagram of a second embodiment of a compound seed layer of a magnetic random access memory according to the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in other sequences than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, apparatus, article, or device that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or device.

The following description of the embodiments refers to the accompanying drawings for illustrating the specific embodiments in which the invention may be practiced. In the present invention, directional terms such as "up", "down", "front", "back", "left", "right", "inner", "outer", "side", etc. refer to directions of the attached drawings. Accordingly, the directional terms used are used for explanation and understanding of the present invention, and are not used for limiting the present invention.

The drawings and description are to be regarded as illustrative in nature, and not as restrictive. In the drawings, elements having similar structures are denoted by the same reference numerals. In addition, the size and thickness of each component shown in the drawings are arbitrarily illustrated for understanding and ease of description, but the present invention is not limited thereto.

In the drawings, the range of configurations of devices, systems, components, circuits is expanded for clarity, understanding and ease of description. It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present.

In addition, in the description, unless explicitly described to the contrary, the word "comprise" will be understood to mean that the recited components are included, but not to exclude any other components. Further, in the specification, "on.

To further illustrate the technical means and effects of the present invention for achieving the predetermined objects, the following detailed description is given, with reference to the accompanying drawings and embodiments, for a magnetic random access memory cell containing copper or copper nitride as a composite seed layer according to the present invention, with reference to the following detailed description.

FIG. 1 is a schematic diagram of a MRAM cell according to the present application. In one embodiment of the present application, a magnetic random access memory cell is provided that includes copper or copper nitride as a composite seed layer. In the process of Physical Vapor Deposition (PVD) of the MRAM magnetic tunnel junction multilayer film, a layer of copper or copper nitride is deposited on the bottom electrode under the condition of not cutting off vacuum, so that the problem of mismatching of the lattice constant of Pt and the bottom electrode material in the prior art is solved, and the TMR is effectively improved. As shown in fig. 1, the magnetic random access memory cell comprises a stack of 110-bottom electrode, 210-composite seed layer, 220-antiparallel ferromagnetic superlattice layer, 221-lower ferromagnetic layer, 222-antiparallel ferromagnetic coupling layer, 223-upper ferromagnetic layer, 230-lattice partition layer, 240-reference layer, 250-barrier layer, 260-free layer, 261-free layer (I), 262-coupling layer, 263-free layer (II), 280-capping layer, 310-hard mask layer.

The bottom electrode 110 is made of TiN, ti, ta, taN, W, WN or their combination, preferably TiN. This is typically done by Physical Vapor Deposition (PVD), which is typically followed by planarization to achieve surface flatness for the fabrication of the magnetic tunnel junction. The thickness is generally 10-30nm.

The composite seed layer 210 is generally composed of Cu/Ta/Pt, and may have a multilayer structure such as CuN/Ta/Pt, cuN/Ru/Pt, or Cu/Ru/Pt.

In fig. 2-a, which is a first embodiment of the mram composite seed layer 210, the copper or copper nitride 211 is implemented by Physical Vapor Deposition (PVD), and the gas is Ar and N2, wherein the N2 content is 10% to 40%, and the thickness is 1 nm to 20nm. The platinum (Pt) or palladium (Pd) metal layer 212 is implemented by Physical Vapor Deposition (PVD), and has a thickness of 1-5nm.

In FIG. 2-b, a second embodiment of the MRAM composite seed layer 210 is shown, wherein a lattice-stabilizing layer 213 is inserted between the copper or copper nitride (CuN) 211 and the platinum (Pt) or palladium (Pd) metal layer 212 for blocking the diffusion of copper atoms, the lattice-stabilizing layer 213 is made of W, mo, nb, hf, ta, ru, rh or Ir and has a thickness of 0.15nm-0.4nm. The thickness of the lattice stabilizing layer is 0-1.5nm.

The composite seed layer 210 is made of Cu/X/Pt, cuN/X/Pt, (Cu/X/Pt) n, (Cu/X) n/Pt or (CuN/X/Pt) n, wherein n is an integer of 2-6. The material of X (the lattice stabilization layer 213) is W, mo, nb, hf, ta, ru, rh or Ir, and the thickness is 0-1.0nm. The Cu or CuN (copper-containing layer 211) has a Face Centered Cubic (FCC) crystal structure with a lattice constant of 3.61 to 3.88 angstroms. The lattice constant of CuN is closer to 3.88 angstroms as the nitrogen content increases. Pt has a Face Centered Cubic (FCC) crystal structure with a lattice constant of 3.9 angstroms. The Co in the antiparallel ferromagnetic superlattice layer also has a Face Centered Cubic (FCC) crystal structure with a lattice constant of 3.54 angstroms. The Cu or CuN is arranged on the Ta bottom electrode, and can easily grow into a face-centered cubic (FCC) crystal structure, the lattice constant of the Cu or CuN is close to that of Pt and Co, and the lattices are matched. The thinner X between CuN and Pt also serves to stabilize the lattice and block copper diffusion.

The platinum (Pt) or palladium (Pd) metal layer 212 may be processed by a plasma etching process with appropriate power and pressure to optimize the flatness and meet the requirement of the antiparallel ferromagnetic superlattice layer on the flatness.

Further, the lattice stabilization layer 213 is deposited in a physical vapor deposition process chamber.

Further, the composite seed layer 210 further includes a structure that is repeated a plurality of times: x (copper-containing layer/lattice-stabilizing layer/platinum or palladium layer) or x/platinum or palladium layer, x being a positive integer not greater than 6.

An Anti-Parallel ferromagnetic super-lattice (Anti-Parallel ferromagnetic super-lattice) layer 220 is generally comprised of a lower ferromagnetic layer 221, an Anti-Parallel ferromagnetic coupling layer 222, and an upper ferromagnetic layer 223. The main structure is [ Co/Pt ] nCo/(Ru, ir or Rh), [ Co/Pt ] nCo/(Ru, ir or Rh)/Co [ Pt/Co ] m, [ Co/Pd ] nCo/(Ru, ir or Rh), [ Co/Pd ] nCo/(Ru, ir or Rh)/Co [ Pd/Co ] m, [ Co/Ni ] nCo/(Ru, ir or Rh) or [ Co/Ni ] nCo/(Ru, ir or Rh)/Co [ Ni/Co ] m superlattice structure, wherein n is not less than 1,m and is not less than 0. Preferably, the structure is one of the following bottom-up structures: (Co/(Pt or Pd)) n/Co/(Ru or Ir)/Co/((Pt or Pd)/Co) m, or (Co/(Pt or Pd)) nCo/Ru/(W, mo or Cr), n is an integer of 1-6, m is an integer of 0-3, and the antiparallel ferromagnetic superlattice layer 220 has a strong Perpendicular Magnetic Anisotropy (PMA).

And a lattice partition layer is further included between the reference layer and the antiparallel ferromagnetic superlattice layer, and the material of the lattice partition layer is selected from W, mo, nb, hf and Ta. Preferably, the lattice-partition layer 230 is made of Ta, W, mo, hf, fe, co (Ta, W, mo or Hf), fe (Ta, W, mo or Hf), feCo (Ta, W, mo or Hf) or FeCoB (Ta, W, mo or Hf) and has a thickness of 0.15nm to 0.4nm.

The reference layer 240 is made of a ferromagnetic material, typically FeCoB, coB, feB, fe, etc. The atomic percent of B in FeB or CoB is 15-40%; in the CoFeB alloy, co: the atomic ratio of Fe is 1:3 to 3:1; the thickness is 0.8 nm-1.5nm.

The barrier layer 250 is made of a non-magnetic metal oxide or metal, typically of MgO or MgO/Mg/MgO structure, and has a thickness of 0.8-1.5nm.

The free layer 260 is composed of a free layer (I) 261, a coupling layer 262, and a free layer (II) 263. The total thickness is 1.8 nm-3 nm.

The thickness of the free layer (I) 261 is 1.3-1.9nm, and the material is CoFeB, coB or FeB. The coupling layer 262 is made of W, mo, V, nb, cr, hf, ti, zr, ta, sc, Y, zn, ru or Os with a thickness of 0.2-0.5nm. The thickness of the free layer (II) 263 is 0.3-0.8nm, and the material is CoFeB, coB or FeB. The atomic percent of B in FeB or CoB is 15-40%; in the CoFeB alloy, co: the atomic ratio of Fe is 1:3 to 3:1; 15 to 40 atomic percent;

the capping layer 270 is formed by sequentially depositing multiple materials such as MgO, pt, coFeB, coFeC, W, mo, mg, nb, ru, hf, V, cr, etc., and preferably has a structure of MgO/(W, mo, hf)/Ru or MgO/Pt/(W, mo, hf)/Ru.

The hard mask layer 310 is made of Ta, taN, ti, tiN, W, WN or a combination thereof.

In the specific process, the PVD deposition conditions are adjusted to change the composition of the materials, and a plasma etching process, an infrared heating process and a cooling process can be added to modify the materials to obtain the optimal performance.

After deposition of all the film layers, an anneal at a temperature of 400 ℃ for 60-90 minutes is preferred to cause the reference layer, barrier layer and free layer to change phase from amorphous to Body Centered Cubic (BCC) crystal structure.

Another objective of the present invention is to provide a magnetic random access memory architecture, which includes a plurality of memory cells, each memory cell being disposed at a crossing of a bit line and a word line, each memory cell comprising: a magnetic tunnel junction as any one of the previous; a bottom electrode located below the magnetic tunnel junction; and a top electrode located above the magnetic tunnel junction.

The application provides a magnetic tunnel junction structure with a lattice promoting layer, which requires that a composite seed layer below an anti-parallel ferromagnetic superlattice layer has ultrahigh flatness and the lattice constant of the composite seed layer is highly matched with the anti-parallel ferromagnetic superlattice layer in order to ensure the normal work of a magnetic random access memory. Furthermore, in the deposition process of the composite seed layer before the anti-parallel ferromagnetic superlattice layer (SyAF), the FCC (111) lattice promoting layer (CPL) and the growth process thereof are adopted, and the composite seed layer with the multilayer structure containing metallic copper or copper nitride is combined, so that the anti-parallel ferromagnetic superlattice layer (SyAF) has strong FCC (111) and PMA (cubic fluoride) structures, and meanwhile, on the premise of ensuring the normal work of the magnetic random access memory, the production cost is reduced, and the problem that thick Pt is difficult to etch is avoided. The method is very beneficial to the improvement of magnetism, electricity and yield of the whole MTJ unit and the miniaturization of devices.

The terms "in one embodiment of the present application" and "in various embodiments" are used repeatedly. This phrase generally does not refer to the same embodiment; it may also refer to the same embodiment. The terms "comprising," "having," and "including" are synonymous, unless the context dictates otherwise.

Although the present application has been described with reference to specific embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application, and all changes, substitutions and alterations that fall within the spirit and scope of the application are to be understood as being covered by the following claims.

Claims

1. A magnetic random access memory storage unit, magnetic random access memory storage unit from top to bottom structure includes top electrode, magnetic tunnel junction and bottom electrode, magnetic tunnel junction from top to bottom structure includes overburden, free layer, barrier layer, reference layer, anti-parallel ferromagnetic superlattice layer and composite seed layer, its characterized in that, composite seed layer includes:

the copper-containing layer is arranged on the bottom electrode and is made of copper or copper nitride;

a lattice stabilization layer disposed on the copper-containing layer;

a platinum or palladium (Pt or Pd) metal layer disposed on the lattice stabilization layer;

the copper-containing layer and the platinum or palladium metal layer are both in a face-centered cubic (FCC) crystal structure, the lattice constant of the copper-containing layer is 3.61-3.88 angstroms, and the composite seed layer is used for guiding the generation of the anti-parallel ferromagnetic superlattice layer, so that the anti-parallel ferromagnetic superlattice layer forms a face-centered cubic FCC (111) crystal orientation structure and has perpendicular magnetic anisotropy when being generated.

2. The magnetic random access memory cell of claim 1 wherein the copper-containing layer has a thickness of 1 to 20nm; the thickness of the platinum or palladium metal layer is 1-5nm.

3. The MRAM memory cell of claim 1, wherein the copper-containing layer and the platinum or palladium (Pt or Pd) metal layer are deposited in a PVD process chamber.

4. The MRAM memory cell of claim 3 wherein the platinum or palladium (Pt or Pd) metal layer is deposited and then further subjected to a plasma etch surface treatment in a vacuum to improve surface planarity.

5. The MRAM memory cell of claim 1, wherein the lattice-stabilizing layer is selected from Ta, hf, W, mo, nb, ru, rh and Ir and has a thickness of 0nm to 1.5nm.

6. The MRAM memory cell of claim 1, wherein the lattice-stabilizing layer is deposited in a physical vapor deposition process chamber.

7. The magnetic random access memory cell of claim 1 wherein the composite seed layer further comprises a structure that repeats a plurality of times: x (copper-containing layer/lattice-stabilizing layer/platinum or palladium layer) or x/platinum or palladium layer, x being a positive integer not greater than 6.

8. The magnetic random access memory cell of claim 1 wherein the antiparallel ferromagnetic superlattice layer is one of the following bottom-up structures: (Co/(Pt or Pd)) n/Co/(Ru, rh or Ir)/Co/((Pt or Pd)/Co) m, or (Co/(Pt or Pd)) nCo/Ru/(W, mo or Cr), n is an integer of 1-6, and m is an integer of 0-3.

9. The MRAM memory cell of claim 1, wherein the reference layer and the antiparallel ferromagnetic superlattice layer further comprise a lattice-stopper layer formed of a material selected from W, mo, nb, hf and Ta and having a thickness of 0.15nm to 0.4nm.

10. A magnetic random access memory comprising the magnetic random access memory cell of any one of claims 1-9.